Merge lp:~widelands-dev/widelands/terrain_affinity_as_int into lp:widelands

[GunChleoc]

Fix desyncs caused by floating point arithmetic

- Floating point arithmetic can become inconsistent across platforms/compilers/hardware
- Upscale terrain affinity constants to turn them into ints
- Upscale the result of the affinity calculation and then use std::floor to cut it off at
  largely reduced precision for consistent rounding behavior. This should fix inconsistencies
  with double rounding and rounding direction.
- Catch a possible division by 0.

Fix cross-platform desyncs caused by floating point arithmetic. Further reading:

https://randomascii.wordpress.com/2012/03/21/intermediate-floating-point-precision/

https://arxiv.org/abs/cs/0701192

Test savegame:

https://bugs.launchpad.net/widelands/+bug/1800338/comments/3

With this savegame, I can cause a multiplayer desync on the same machine by compiling one copy of Widelands with GCC and another copy with Clang. The desync happens before the ship finishes building. With this branch, the desync is gone.

[bunnybot (widelandsofficial)]

Continuous integration builds have changed state:

Travis build 4197. State: failed. Details: https://travis-ci.org/widelands/widelands/builds/452676073.
Appveyor build 3993. State: failed. Details: https://ci.appveyor.com/project/widelands-dev/widelands/build/_widelands_dev_widelands_terrain_affinity_as_int-3993.

[bunnybot (widelandsofficial)]

Continuous integration builds have changed state:

Travis build 4213. State: errored. Details: https://travis-ci.org/widelands/widelands/builds/453859920.
Appveyor build 4009. State: failed. Details: https://ci.appveyor.com/project/widelands-dev/widelands/build/_widelands_dev_widelands_terrain_affinity_as_int-4009.

[bunnybot (widelandsofficial)]

Continuous integration builds have changed state:

Travis build 4238. State: passed. Details: https://travis-ci.org/widelands/widelands/builds/455849882.
Appveyor build 4034. State: success. Details: https://ci.appveyor.com/project/widelands-dev/widelands/build/_widelands_dev_widelands_terrain_affinity_as_int-4034.

[Arty (artydent)]

I reviewed the code and also tested somewhat. Still has a few issues, most of them minor though. See diff comments.

The file data\world\immovables\bush1\init.lua still has a few comments (lines 86-94) referring to the floating point values, this should also be changed in this branch.

Overall it should be much less likely now to get different results based on platform/compiler dependent precision choices, but they might still happen. There are still things based on floating point calculations (like the main probability calculation in calculate_probability_to_grow) but they might be difficult to replace with pure integer based stuff.
That said, considering that the ratios of the final probabilities of the six best immovables already change significantly with this branch, we could possibly also change the basic probability calculation to somewhat that uses only integer operations but is not too far off from the current approach (which seems to have been based roughly on multivariate normal distributions).

Btw, where did those three weight constants in calculate_probability_to_grow originally come from? Their precision is too high to be from a simple "try and error until it feels right" approach. They still feel quite arbitrary though.

review: Needs Fixing

[GunChleoc (gunchleoc)]

Thanks for the excellent review :)

I have addressed most of your comments and left replies to the rest.

One of our math wizards spent a long time tweaking the system and the function, so I'm hesitant to change any semantics here. There is an e function involved, so there is no way to avoid floating point completely unless we radically change the system.

[Arty (artydent)]

Yes, the exponential function is the problem. Approximating it with highish precision using only integer calculations would require a lot of computation, which isn't really feasible. There are reasonable options though if we don't mind straying a little. The function we use here is basically a three-dimensional Gauß-curve, and I think we could find an alternative that roughly preserves the shape and can be done with a small number of integer operations.
It's probably not necessary though, but if we keep getting desyncs because of such platform/compiler-dependent computation differences, this would provide an option.

I also replied to your replies.

[GunChleoc (gunchleoc)]

Thanks for your math wizardry - I have now implemented both suggestions.

I think that greatly cutting the precision while forcing a uniform rounding strategy (round down) should be good enough for our purposes. Let's merge this and see if we're still getting desyncs. We can always decide to change the formula later if necessary.

@bunnybot merge

[Arty (artydent)]

Looks good now.

The comment with the assciativity is kinda obsolete now though.

And using int64_t wasn't really necessary now that you use the weights linearly.

review: Approve

=== modified file 'data/tribes/immovables/berry_bushes/blueberry/init.lua'
--- data/tribes/immovables/berry_bushes/blueberry/init.lua	2018-02-17 15:41:29 +0000
+++ data/tribes/immovables/berry_bushes/blueberry/init.lua	2018-11-23 12:45:17 +0000
@@ -2,9 +2,9 @@
 
 terrain_affinity = {
    preferred_temperature = 45, -- Temperature is in arbitrary units.
-   preferred_humidity = 0.75,  -- In percent (1 being very wet).
-   preferred_fertility = 0.4,  -- In percent (1 being very fertile).
-   pickiness = 0.15,           -- Lower means it is less picky, i.e. it can deal better.
+   preferred_humidity = 750,   -- Values between 0 and 1000 (1000 being very wet).
+   preferred_fertility = 400,  -- Values between 0 and 1000 (1000 being very fertile).
+   pickiness = 15,             -- Lower means it is less picky, i.e. it can deal better.
 }
 
 tribes:new_immovable_type {
 
=== modified file 'data/tribes/immovables/berry_bushes/currant_black/init.lua'
--- data/tribes/immovables/berry_bushes/currant_black/init.lua	2018-02-17 15:41:29 +0000
+++ data/tribes/immovables/berry_bushes/currant_black/init.lua	2018-11-23 12:45:17 +0000
@@ -2,9 +2,9 @@
 
 terrain_affinity = {
    preferred_temperature = 120,
-   preferred_humidity = 0.1,
-   preferred_fertility = 0.2,
-   pickiness = 0.5,
+   preferred_humidity = 100,
+   preferred_fertility = 200,
+   pickiness = 50,
 }
 
 tribes:new_immovable_type {
 
=== modified file 'data/tribes/immovables/berry_bushes/currant_red/init.lua'
--- data/tribes/immovables/berry_bushes/currant_red/init.lua	2018-02-17 15:41:29 +0000
+++ data/tribes/immovables/berry_bushes/currant_red/init.lua	2018-11-23 12:45:17 +0000
@@ -2,9 +2,9 @@
 
 terrain_affinity = {
    preferred_temperature = 95,
-   preferred_humidity = 0.55,
-   preferred_fertility = 0.45,
-   pickiness = 0.4,
+   preferred_humidity = 550,
+   preferred_fertility = 450,
+   pickiness = 40,
 }
 
 tribes:new_immovable_type {
 
=== modified file 'data/tribes/immovables/berry_bushes/desert_hackberry/init.lua'
--- data/tribes/immovables/berry_bushes/desert_hackberry/init.lua	2018-02-17 15:41:29 +0000
+++ data/tribes/immovables/berry_bushes/desert_hackberry/init.lua	2018-11-23 12:45:17 +0000
@@ -2,9 +2,9 @@
 
 terrain_affinity = {
    preferred_temperature = 170, -- Temperature is in arbitrary units.
-   preferred_humidity = 0.05,   -- In percent (1 being very wet).
-   preferred_fertility = 0.05,  -- In percent (1 being very fertile).
-   pickiness = 0.3,             -- Lower means it is less picky, i.e. it can deal better.
+   preferred_humidity = 50,     -- Values between 0 and 1000 (1000 being very wet).
+   preferred_fertility = 50,    -- Values between 0 and 1000 (1000 being very fertile).
+   pickiness = 30,             -- Lower means it is less picky, i.e. it can deal better.
 }
 
 tribes:new_immovable_type {
 
=== modified file 'data/tribes/immovables/berry_bushes/juniper/init.lua'
--- data/tribes/immovables/berry_bushes/juniper/init.lua	2018-04-21 15:27:00 +0000
+++ data/tribes/immovables/berry_bushes/juniper/init.lua	2018-11-23 12:45:17 +0000
@@ -2,9 +2,9 @@
 
 terrain_affinity = {
    preferred_temperature = 115,
-   preferred_humidity = 0.6,
-   preferred_fertility = 0.2,
-   pickiness = 0.15,
+   preferred_humidity = 600,
+   preferred_fertility = 200,
+   pickiness = 15,
 }
 
 tribes:new_immovable_type {
 
=== modified file 'data/tribes/immovables/berry_bushes/raspberry/init.lua'
--- data/tribes/immovables/berry_bushes/raspberry/init.lua	2018-02-17 15:41:29 +0000
+++ data/tribes/immovables/berry_bushes/raspberry/init.lua	2018-11-23 12:45:17 +0000
@@ -2,9 +2,9 @@
 
 terrain_affinity = {
    preferred_temperature = 50,
-   preferred_humidity = 0.3,
-   preferred_fertility = 0.05,
-   pickiness = 0.1,
+   preferred_humidity = 300,
+   preferred_fertility = 50,
+   pickiness = 10,
 }
 
 tribes:new_immovable_type {
 
=== modified file 'data/tribes/immovables/berry_bushes/sea_buckthorn/init.lua'
--- data/tribes/immovables/berry_bushes/sea_buckthorn/init.lua	2018-02-17 15:41:29 +0000
+++ data/tribes/immovables/berry_bushes/sea_buckthorn/init.lua	2018-11-23 12:45:17 +0000
@@ -2,9 +2,9 @@
 
 terrain_affinity = {
    preferred_temperature = 100, -- Temperature is in arbitrary units.
-   preferred_humidity = 0.95,   -- In percent (1 being very wet).
-   preferred_fertility = 0.05,  -- In percent (1 being very fertile).
-   pickiness = 0.15,            -- Lower means it is less picky, i.e. it can deal better.
+   preferred_humidity = 950,    -- Values between 0 and 1000 (1000 being very wet).
+   preferred_fertility = 50,    -- Values between 0 and 1000 (1000 being very fertile).
+   pickiness = 15,              -- Lower means it is less picky, i.e. it can deal better.
 }
 
 tribes:new_immovable_type {
 
=== modified file 'data/tribes/immovables/berry_bushes/strawberry/init.lua'
--- data/tribes/immovables/berry_bushes/strawberry/init.lua	2018-05-02 08:13:07 +0000
+++ data/tribes/immovables/berry_bushes/strawberry/init.lua	2018-11-23 12:45:17 +0000
@@ -2,9 +2,9 @@
 
 terrain_affinity = {
    preferred_temperature = 110, -- Temperature is in arbitrary units.
-   preferred_humidity = 0.6,    -- In percent (1 being very wet).
-   preferred_fertility = 0.8,   -- In percent (1 being very fertile).
-   pickiness = 0.2,             -- Lower means it is less picky, i.e. it can deal better.
+   preferred_humidity = 600,    -- Values between 0 and 1000 (1000 being very wet).
+   preferred_fertility = 800,   -- Values between 0 and 1000 (1000 being very fertile).
+   pickiness = 20,             -- Lower means it is less picky, i.e. it can deal better.
 }
 
 tribes:new_immovable_type {
 
=== modified file 'data/world/immovables/bush1/init.lua'
--- data/world/immovables/bush1/init.lua	2017-09-02 16:12:50 +0000
+++ data/world/immovables/bush1/init.lua	2018-11-23 12:45:17 +0000
@@ -83,15 +83,15 @@
 --             -- Temperature is in arbitrary units.
 --             preferred_temperature = 125,
 --
---             -- In percent (1 being very wet).
---             preferred_humidity = 0.65,
---
---             -- In percent (1 being very fertile).
---             preferred_fertility = 0.6,
---
---             -- A value in [0, 1] that defines how well this immovable can deal with non-ideal terrain.
+--             -- The preferred humibity. This is a value between 0 and 1000, with 1000 being very wet.
+--             preferred_humidity = 650,
+--
+--             -- The preferred fertility. This is a value between 0 and 1000, with 1000 being very fertile.
+--             preferred_fertility = 600,
+--
+--             -- A value in [0, 99] that defines how well this immovable can deal with non-ideal terrain.
 --             -- A lower value means that it is less picky, i.e. it can deal better with it.
---             pickiness = 0.6,
+--             pickiness = 60,
 --          }
 --
 --    **animations**
 
=== modified file 'data/world/immovables/trees/alder/init.lua'
--- data/world/immovables/trees/alder/init.lua	2016-02-10 19:50:13 +0000
+++ data/world/immovables/trees/alder/init.lua	2018-11-23 12:45:17 +0000
@@ -4,15 +4,15 @@
    -- Temperature is in arbitrary units.
    preferred_temperature = 125,
 
-   -- In percent (1 being very wet).
-   preferred_humidity = 0.65,
-
-   -- In percent (1 being very fertile).
-   preferred_fertility = 0.6,
-
-   -- A value in [0, 1] that defines how well this can deal with non-ideal
+   -- Value between 0 and 1000 (1000 being very wet).
+   preferred_humidity = 650,
+
+   -- Values between 0 and 1000 (1000 being very fertile).
+   preferred_fertility = 600,
+
+   -- A value in [0, 100] that defines how well this can deal with non-ideal
    -- situations. Lower means it is less picky, i.e. it can deal better.
-   pickiness = 0.6,
+   pickiness = 60,
 }
 
 world:new_immovable_type{
 
=== modified file 'data/world/immovables/trees/aspen/init.lua'
--- data/world/immovables/trees/aspen/init.lua	2016-02-10 19:50:13 +0000
+++ data/world/immovables/trees/aspen/init.lua	2018-11-23 12:45:17 +0000
@@ -2,9 +2,9 @@
 
 terrain_affinity = {
    preferred_temperature = 100,
-   preferred_humidity = 0.6,
-   preferred_fertility = 0.7,
-   pickiness = 0.8,
+   preferred_humidity = 600,
+   preferred_fertility = 700,
+   pickiness = 80,
 }
 
 world:new_immovable_type{
 
=== modified file 'data/world/immovables/trees/beech/init.lua'
--- data/world/immovables/trees/beech/init.lua	2016-02-10 19:50:13 +0000
+++ data/world/immovables/trees/beech/init.lua	2018-11-23 12:45:17 +0000
@@ -2,9 +2,9 @@
 
 terrain_affinity = {
    preferred_temperature = 110,
-   preferred_humidity = 0.4,
-   preferred_fertility = 0.6,
-   pickiness = 0.6,
+   preferred_humidity = 400,
+   preferred_fertility = 600,
+   pickiness = 60,
 }
 
 world:new_immovable_type{
 
=== modified file 'data/world/immovables/trees/birch/init.lua'
--- data/world/immovables/trees/birch/init.lua	2016-02-10 19:50:13 +0000
+++ data/world/immovables/trees/birch/init.lua	2018-11-23 12:45:17 +0000
@@ -2,9 +2,9 @@
 
 terrain_affinity = {
    preferred_temperature = 80,
-   preferred_humidity = 0.65,
-   preferred_fertility = 0.6,
-   pickiness = 0.6,
+   preferred_humidity = 650,
+   preferred_fertility = 600,
+   pickiness = 60,
 }
 
 world:new_immovable_type{
 
=== modified file 'data/world/immovables/trees/cirrus/init.lua'
--- data/world/immovables/trees/cirrus/init.lua	2016-02-10 19:50:13 +0000
+++ data/world/immovables/trees/cirrus/init.lua	2018-11-23 12:45:17 +0000
@@ -2,9 +2,9 @@
 
 terrain_affinity = {
    preferred_temperature = 110,
-   preferred_humidity = 0.15,
-   preferred_fertility = 0.95,
-   pickiness = 0.8,
+   preferred_humidity = 150,
+   preferred_fertility = 950,
+   pickiness = 80,
 }
 
 world:new_immovable_type{
 
=== modified file 'data/world/immovables/trees/larch/init.lua'
--- data/world/immovables/trees/larch/init.lua	2016-02-10 19:50:13 +0000
+++ data/world/immovables/trees/larch/init.lua	2018-11-23 12:45:17 +0000
@@ -2,9 +2,9 @@
 
 terrain_affinity = {
    preferred_temperature = 50,
-   preferred_humidity = 0.8,
-   preferred_fertility = 0.45,
-   pickiness = 0.8,
+   preferred_humidity = 800,
+   preferred_fertility = 450,
+   pickiness = 80,
 }
 
 world:new_immovable_type{
 
=== modified file 'data/world/immovables/trees/liana/init.lua'
--- data/world/immovables/trees/liana/init.lua	2016-02-10 19:50:13 +0000
+++ data/world/immovables/trees/liana/init.lua	2018-11-23 12:45:17 +0000
@@ -2,9 +2,9 @@
 
 terrain_affinity = {
    preferred_temperature = 120,
-   preferred_humidity = 0.2,
-   preferred_fertility = 0.7,
-   pickiness = 0.6,
+   preferred_humidity = 200,
+   preferred_fertility = 700,
+   pickiness = 60,
 }
 
 world:new_immovable_type{
 
=== modified file 'data/world/immovables/trees/maple/init.lua'
--- data/world/immovables/trees/maple/init.lua	2016-02-28 08:33:59 +0000
+++ data/world/immovables/trees/maple/init.lua	2018-11-23 12:45:17 +0000
@@ -2,9 +2,9 @@
 
 terrain_affinity = {
    preferred_temperature = 110,
-   preferred_humidity = 0.55,
-   preferred_fertility = 0.8,
-   pickiness = 0.8,
+   preferred_humidity = 550,
+   preferred_fertility = 800,
+   pickiness = 80,
 }
 
 world:new_immovable_type{
 
=== modified file 'data/world/immovables/trees/mushroom_dark/init.lua'
--- data/world/immovables/trees/mushroom_dark/init.lua	2016-02-10 19:50:13 +0000
+++ data/world/immovables/trees/mushroom_dark/init.lua	2018-11-23 12:45:17 +0000
@@ -2,9 +2,9 @@
 
 terrain_affinity = {
    preferred_temperature = 100,
-   preferred_humidity = 0.2,
-   preferred_fertility = 0.8,
-   pickiness = 0.8,
+   preferred_humidity = 200,
+   preferred_fertility = 800,
+   pickiness = 80,
 }
 
 world:new_immovable_type{
 
=== modified file 'data/world/immovables/trees/mushroom_green/init.lua'
--- data/world/immovables/trees/mushroom_green/init.lua	2016-02-10 19:50:13 +0000
+++ data/world/immovables/trees/mushroom_green/init.lua	2018-11-23 12:45:17 +0000
@@ -2,9 +2,9 @@
 
 terrain_affinity = {
    preferred_temperature = 105,
-   preferred_humidity = 0.2,
-   preferred_fertility = 0.9,
-   pickiness = 0.8,
+   preferred_humidity = 200,
+   preferred_fertility = 900,
+   pickiness = 80,
 }
 
 world:new_immovable_type{
 
=== modified file 'data/world/immovables/trees/mushroom_red/init.lua'
--- data/world/immovables/trees/mushroom_red/init.lua	2016-02-10 19:50:13 +0000
+++ data/world/immovables/trees/mushroom_red/init.lua	2018-11-23 12:45:17 +0000
@@ -2,9 +2,9 @@
 
 terrain_affinity = {
    preferred_temperature = 80,
-   preferred_humidity = 0.35,
-   preferred_fertility = 0.85,
-   pickiness = 0.6,
+   preferred_humidity = 350,
+   preferred_fertility = 850,
+   pickiness = 60,
 }
 
 world:new_immovable_type{
 
=== modified file 'data/world/immovables/trees/oak/init.lua'
--- data/world/immovables/trees/oak/init.lua	2016-02-10 19:50:13 +0000
+++ data/world/immovables/trees/oak/init.lua	2018-11-23 12:45:17 +0000
@@ -2,9 +2,9 @@
 
 terrain_affinity = {
    preferred_temperature = 90,
-   preferred_humidity = 0.7,
-   preferred_fertility = 0.5,
-   pickiness = 0.6,
+   preferred_humidity = 700,
+   preferred_fertility = 500,
+   pickiness = 60,
 }
 
 world:new_immovable_type{
 
=== modified file 'data/world/immovables/trees/palm_borassus/init.lua'
--- data/world/immovables/trees/palm_borassus/init.lua	2016-02-10 19:50:13 +0000
+++ data/world/immovables/trees/palm_borassus/init.lua	2018-11-23 12:45:17 +0000
@@ -2,9 +2,9 @@
 
 terrain_affinity = {
    preferred_temperature = 180,
-   preferred_humidity = 0.4,
-   preferred_fertility = 0.4,
-   pickiness = 0.6,
+   preferred_humidity = 400,
+   preferred_fertility = 400,
+   pickiness = 60,
 }
 
 world:new_immovable_type{
 
=== modified file 'data/world/immovables/trees/palm_coconut/init.lua'
--- data/world/immovables/trees/palm_coconut/init.lua	2016-02-10 19:50:13 +0000
+++ data/world/immovables/trees/palm_coconut/init.lua	2018-11-23 12:45:17 +0000
@@ -2,9 +2,9 @@
 
 terrain_affinity = {
    preferred_temperature = 130,
-   preferred_humidity = 0.5,
-   preferred_fertility = 0.6,
-   pickiness = 0.6,
+   preferred_humidity = 500,
+   preferred_fertility = 600,
+   pickiness = 60,
 }
 
 world:new_immovable_type{
 
=== modified file 'data/world/immovables/trees/palm_date/init.lua'
--- data/world/immovables/trees/palm_date/init.lua	2016-02-10 19:50:13 +0000
+++ data/world/immovables/trees/palm_date/init.lua	2018-11-23 12:45:17 +0000
@@ -2,9 +2,9 @@
 
 terrain_affinity = {
    preferred_temperature = 160,
-   preferred_humidity = 0.5,
-   preferred_fertility = 0.5,
-   pickiness = 0.8,
+   preferred_humidity = 500,
+   preferred_fertility = 500,
+   pickiness = 80,
 }
 
 world:new_immovable_type{
 
=== modified file 'data/world/immovables/trees/palm_oil/init.lua'
--- data/world/immovables/trees/palm_oil/init.lua	2016-02-10 19:50:13 +0000
+++ data/world/immovables/trees/palm_oil/init.lua	2018-11-23 12:45:17 +0000
@@ -2,9 +2,9 @@
 
 terrain_affinity = {
    preferred_temperature = 150,
-   preferred_humidity = 0.55,
-   preferred_fertility = 0.5,
-   pickiness = 0.8,
+   preferred_humidity = 550,
+   preferred_fertility = 500,
+   pickiness = 80,
 }
 
 world:new_immovable_type{
 
=== modified file 'data/world/immovables/trees/palm_roystonea/init.lua'
--- data/world/immovables/trees/palm_roystonea/init.lua	2016-02-10 19:50:13 +0000
+++ data/world/immovables/trees/palm_roystonea/init.lua	2018-11-23 12:45:17 +0000
@@ -2,9 +2,9 @@
 
 terrain_affinity = {
    preferred_temperature = 160,
-   preferred_humidity = 0.6,
-   preferred_fertility = 0.6,
-   pickiness = 0.9,
+   preferred_humidity = 600,
+   preferred_fertility = 600,
+   pickiness = 90,
 }
 
 world:new_immovable_type{
 
=== modified file 'data/world/immovables/trees/rowan/init.lua'
--- data/world/immovables/trees/rowan/init.lua	2016-02-10 19:50:13 +0000
+++ data/world/immovables/trees/rowan/init.lua	2018-11-23 12:45:17 +0000
@@ -2,9 +2,9 @@
 
 terrain_affinity = {
    preferred_temperature = 105,
-   preferred_humidity = 0.65,
-   preferred_fertility = 0.75,
-   pickiness = 0.8,
+   preferred_humidity = 650,
+   preferred_fertility = 750,
+   pickiness = 80,
 }
 
 world:new_immovable_type{
 
=== modified file 'data/world/immovables/trees/spruce/init.lua'
--- data/world/immovables/trees/spruce/init.lua	2016-02-10 19:50:13 +0000
+++ data/world/immovables/trees/spruce/init.lua	2018-11-23 12:45:17 +0000
@@ -2,9 +2,9 @@
 
 terrain_affinity = {
    preferred_temperature = 60,
-   preferred_humidity = 0.7,
-   preferred_fertility = 0.5,
-   pickiness = 0.6,
+   preferred_humidity = 700,
+   preferred_fertility = 500,
+   pickiness = 60,
 }
 
 world:new_immovable_type{
 
=== modified file 'data/world/immovables/trees/twine/init.lua'
--- data/world/immovables/trees/twine/init.lua	2016-02-10 19:50:13 +0000
+++ data/world/immovables/trees/twine/init.lua	2018-11-23 12:45:17 +0000
@@ -2,9 +2,9 @@
 
 terrain_affinity = {
    preferred_temperature = 95,
-   preferred_humidity = 0.2,
-   preferred_fertility = 0.4,
-   pickiness = 0.8,
+   preferred_humidity = 200,
+   preferred_fertility = 400,
+   pickiness = 80,
 }
 
 world:new_immovable_type{
 
=== modified file 'data/world/immovables/trees/umbrella_green/init.lua'
--- data/world/immovables/trees/umbrella_green/init.lua	2016-02-10 19:50:13 +0000
+++ data/world/immovables/trees/umbrella_green/init.lua	2018-11-23 12:45:17 +0000
@@ -2,9 +2,9 @@
 
 terrain_affinity = {
    preferred_temperature = 110,
-   preferred_humidity = 0.2,
-   preferred_fertility = 0.85,
-   pickiness = 0.8,
+   preferred_humidity = 200,
+   preferred_fertility = 850,
+   pickiness = 80,
 }
 
 world:new_immovable_type{
 
=== modified file 'data/world/immovables/trees/umbrella_red/init.lua'
--- data/world/immovables/trees/umbrella_red/init.lua	2016-02-29 17:10:00 +0000
+++ data/world/immovables/trees/umbrella_red/init.lua	2018-11-23 12:45:17 +0000
@@ -2,9 +2,9 @@
 
 terrain_affinity = {
    preferred_temperature = 90,
-   preferred_humidity = 0.15,
-   preferred_fertility = 0.825,
-   pickiness = 0.8,
+   preferred_humidity = 150,
+   preferred_fertility = 825,
+   pickiness = 80,
 }
 
 world:new_immovable_type{
 
=== modified file 'data/world/terrains/init.lua'
--- data/world/terrains/init.lua	2017-09-02 16:12:50 +0000
+++ data/world/terrains/init.lua	2018-11-23 12:45:17 +0000
@@ -131,17 +131,17 @@
 --
 --    **humidity**
 --        *Mandatory*. A terrain affinity constant. These are used to model how well
---        trees will grow on this terrain. Humidity is in percent (1 being very wet).
+--        trees will grow on this terrain. Values range from 1 - 1000 (1000 being very wet).
 --        Example::
 --
---            humidity = 0.6,
+--            humidity = 600,
 --
 --    **fertility**
 --        *Mandatory*. A terrain affinity constant. These are used to model how well
---        trees will grow on this terrain. Fertility is in percent (1 being very
+--        trees will grow on this terrain. Values range from 1 - 1000 (1000 being very
 --        fertile). Example::
 --
---            fertility = 0.7,
+--            fertility = 700,
 --
 
 ------------------------
@@ -167,8 +167,8 @@
    dither_layer = 340,
 
    temperature = 100,
-   humidity = 0.6,
-   fertility = 0.7,
+   humidity = 600,
+   fertility = 700,
 }
 
 
@@ -187,8 +187,8 @@
    textures = { pics_dir .. "summer/meadow2_00.png" },
    dither_layer = 350,
    temperature = 100,
-   humidity = 0.6,
-   fertility = 0.65,
+   humidity = 600,
+   fertility = 650,
 
 }
 
@@ -208,8 +208,8 @@
    textures = { pics_dir .. "summer/meadow3_00.png" },
    dither_layer = 350,
    temperature = 105,
-   humidity = 0.55,
-   fertility = 0.8,
+   humidity = 550,
+   fertility = 800,
 }
 
 
@@ -228,8 +228,8 @@
    textures = { pics_dir .. "summer/meadow4_00.png" },
    dither_layer = 350,
    temperature = 110,
-   humidity = 0.65,
-   fertility = 0.75,
+   humidity = 650,
+   fertility = 750,
 }
 
 
@@ -244,8 +244,8 @@
    textures = { pics_dir .. "summer/steppe_00.png" },
    dither_layer = 330,
    temperature = 100,
-   humidity = 0.4,
-   fertility = 0.4,
+   humidity = 400,
+   fertility = 400,
 }
 
 
@@ -260,8 +260,8 @@
    textures = { pics_dir .. "summer/steppe_barren_00.png" },
    dither_layer = 320,
    temperature = 100,
-   humidity = 0.15,
-   fertility = 0.15,
+   humidity = 150,
+   fertility = 150,
 }
 
 
@@ -276,8 +276,8 @@
    textures = { pics_dir .. "summer/mountain_meadow_00.png" },
    dither_layer = 160,
    temperature = 75,
-   humidity = 0.8,
-   fertility = 0.45,
+   humidity = 800,
+   fertility = 450,
 }
 
 world:new_terrain_type{
@@ -296,8 +296,8 @@
    textures = { pics_dir .. "summer/forested_mountain1_00.png" },
    dither_layer = 71,
    temperature = 50,
-   humidity = 0.75,
-   fertility = 0.5,
+   humidity = 750,
+   fertility = 500,
 }
 
 world:new_terrain_type{
@@ -316,8 +316,8 @@
    textures = { pics_dir .. "summer/forested_mountain2_00.png" },
    dither_layer = 71,
    temperature = 50,
-   humidity = 0.75,
-   fertility = 0.5,
+   humidity = 750,
+   fertility = 500,
 }
 
 world:new_terrain_type{
@@ -331,8 +331,8 @@
    textures = { pics_dir .. "summer/mountain1_00.png" },
    dither_layer = 70,
    temperature = 80,
-   humidity = 0.1,
-   fertility = 0.1,
+   humidity = 100,
+   fertility = 100,
 }
 
 
@@ -347,8 +347,8 @@
    textures = { pics_dir .. "summer/mountain2_00.png" },
    dither_layer = 70,
    temperature = 80,
-   humidity = 0.1,
-   fertility = 0.1,
+   humidity = 100,
+   fertility = 100,
 }
 
 
@@ -363,8 +363,8 @@
    textures = { pics_dir .. "summer/mountain3_00.png" },
    dither_layer = 70,
    temperature = 80,
-   humidity = 0.1,
-   fertility = 0.1,
+   humidity = 100,
+   fertility = 100,
 }
 
 
@@ -379,8 +379,8 @@
    textures = { pics_dir .. "summer/mountain4_00.png" },
    dither_layer = 70,
    temperature = 80,
-   humidity = 0.1,
-   fertility = 0.1,
+   humidity = 100,
+   fertility = 100,
 }
 
 world:new_terrain_type{
@@ -394,8 +394,8 @@
    textures = { pics_dir .. "summer/beach_00.png" },
    dither_layer = 60,
    temperature = 120,
-   humidity = 0.6,
-   fertility = 0.2,
+   humidity = 600,
+   fertility = 200,
 }
 
 world:new_terrain_type{
@@ -410,8 +410,8 @@
    dither_layer = 370,
    fps = 14,
    temperature = 105,
-   humidity = 0.999,
-   fertility = 0.1,
+   humidity = 999,
+   fertility = 100,
 }
 world:new_terrain_type{
    name = "summer_snow",
@@ -424,8 +424,8 @@
    textures = { pics_dir .. "summer/snow_00.png" },
    dither_layer = 220,
    temperature = 50,
-   humidity = 0.999,
-   fertility = 0.001,
+   humidity = 999,
+   fertility = 1,
 }
 
 
@@ -440,9 +440,9 @@
    textures = path.list_files(pics_dir .. "summer/lava/lava_??.png"),
    dither_layer = 30,
    fps = 4,
-   temperature = 1273.0,
-   humidity = 0.001,
-   fertility = 0.001,
+   temperature = 1273,
+   humidity = 1,
+   fertility = 1,
 }
 
 
@@ -458,8 +458,8 @@
    dither_layer = 180,
    fps = 14,
    temperature = 100,
-   humidity = 0.999,
-   fertility = 0.001,
+   humidity = 999,
+   fertility = 1,
 }
 
 ------------------------
@@ -482,8 +482,8 @@
    textures = { pics_dir .. "wasteland/ashes_00.png" },
    dither_layer = 400,
    temperature = 120,
-   humidity = 0.15,
-   fertility = 0.9,
+   humidity = 150,
+   fertility = 900,
 }
 
 
@@ -502,8 +502,8 @@
    textures = { pics_dir .. "wasteland/ashes2_00.png" },
    dither_layer = 410,
    temperature = 118,
-   humidity = 0.13,
-   fertility = 0.999,
+   humidity = 130,
+   fertility = 999,
 }
 
 
@@ -522,8 +522,8 @@
    textures = { pics_dir .. "wasteland/hardground1_00.png" },
    dither_layer = 420,
    temperature = 100,
-   humidity = 0.25,
-   fertility = 0.8,
+   humidity = 250,
+   fertility = 800,
 }
 
 
@@ -542,8 +542,8 @@
    textures = { pics_dir .. "wasteland/hardground2_00.png" },
    dither_layer = 370,
    temperature = 95,
-   humidity = 0.15,
-   fertility = 0.85,
+   humidity = 150,
+   fertility = 850,
 }
 
 
@@ -562,8 +562,8 @@
    textures = { pics_dir .. "wasteland/hardground3_00.png" },
    dither_layer = 380,
    temperature = 105,
-   humidity = 0.2,
-   fertility = 0.9,
+   humidity = 200,
+   fertility = 900,
 }
 
 
@@ -582,8 +582,8 @@
    textures = { pics_dir .. "wasteland/hardground4_00.png" },
    dither_layer = 390,
    temperature = 90,
-   humidity = 0.2,
-   fertility = 0.8,
+   humidity = 200,
+   fertility = 800,
 }
 
 
@@ -598,8 +598,8 @@
    textures = { pics_dir .. "wasteland/hardlava_00.png" },
    dither_layer = 360,
    temperature = 120,
-   humidity = 0.1,
-   fertility = 0.2,
+   humidity = 100,
+   fertility = 200,
 }
 
 
@@ -618,8 +618,8 @@
    textures = { pics_dir .. "wasteland/forested_mountain1_00.png" },
    dither_layer = 81,
    temperature = 110,
-   humidity = 0.15,
-   fertility = 0.95,
+   humidity = 150,
+   fertility = 950,
 }
 
 world:new_terrain_type{
@@ -637,8 +637,8 @@
    textures = { pics_dir .. "wasteland/forested_mountain2_00.png" },
    dither_layer = 81,
    temperature = 95,
-   humidity = 0.2,
-   fertility = 0.4,
+   humidity = 200,
+   fertility = 400,
 }
 
 world:new_terrain_type{
@@ -652,8 +652,8 @@
    textures = { pics_dir .. "wasteland/mountain1_00.png" },
    dither_layer = 90,
    temperature = 80,
-   humidity = 0.05,
-   fertility = 0.2,
+   humidity = 50,
+   fertility = 200,
 }
 
 
@@ -668,8 +668,8 @@
    textures = { pics_dir .. "wasteland/mountain2_00.png" },
    dither_layer = 90,
    temperature = 80,
-   humidity = 0.05,
-   fertility = 0.2,
+   humidity = 50,
+   fertility = 200,
 }
 
 
@@ -684,8 +684,8 @@
    textures = { pics_dir .. "wasteland/mountain3_00.png" },
    dither_layer = 90,
    temperature = 80,
-   humidity = 0.05,
-   fertility = 0.2,
+   humidity = 50,
+   fertility = 200,
 }
 
 
@@ -700,8 +700,8 @@
    textures = { pics_dir .. "wasteland/mountain4_00.png" },
    dither_layer = 80,
    temperature = 80,
-   humidity = 0.05,
-   fertility = 0.2,
+   humidity = 50,
+   fertility = 200,
 }
 
 
@@ -716,8 +716,8 @@
    textures = { pics_dir .. "wasteland/beach_00.png" },
    dither_layer = 50,
    temperature = 60,
-   humidity = 0.4,
-   fertility = 0.2,
+   humidity = 400,
+   fertility = 200,
 }
 
 
@@ -732,9 +732,9 @@
    textures = path.list_files(pics_dir .. "wasteland/lava_stone1/lava-stone1_??.png"),
    dither_layer = 20,
    fps = 7,
-   temperature = 1273.0,
-   humidity = 0.001,
-   fertility = 0.001,
+   temperature = 1273,
+   humidity = 1,
+   fertility = 1,
 }
 
 
@@ -749,9 +749,9 @@
    textures = path.list_files(pics_dir .. "wasteland/lava_stone2/lava-stone2_??.png"),
    dither_layer = 10,
    fps = 7,
-   temperature = 1273.0,
-   humidity = 0.001,
-   fertility = 0.001,
+   temperature = 1273,
+   humidity = 1,
+   fertility = 1,
 }
 
 
@@ -767,8 +767,8 @@
    dither_layer = 170,
    fps = 14,
    temperature = 100,
-   humidity = 0.999,
-   fertility = 0.001,
+   humidity = 999,
+   fertility = 1,
 }
 
 
@@ -792,8 +792,8 @@
    textures = { pics_dir .. "winter/tundra_00.png" },
    dither_layer = 230,
    temperature = 50,
-   humidity = 0.85,
-   fertility = 0.45,
+   humidity = 850,
+   fertility = 450,
 }
 
 
@@ -812,8 +812,8 @@
    textures = { pics_dir .. "winter/tundra2_00.png" },
    dither_layer = 240,
    temperature = 55,
-   humidity = 0.75,
-   fertility = 0.45,
+   humidity = 750,
+   fertility = 450,
 }
 
 
@@ -832,8 +832,8 @@
    textures = { pics_dir .. "winter/tundra3_00.png" },
    dither_layer = 240,
    temperature = 50,
-   humidity = 0.8,
-   fertility = 0.4,
+   humidity = 800,
+   fertility = 400,
 }
 
 
@@ -848,8 +848,8 @@
    textures = { pics_dir .. "winter/tundra_taiga_00.png" },
    dither_layer = 230,
    temperature = 40,
-   humidity = 0.75,
-   fertility = 0.4,
+   humidity = 750,
+   fertility = 400,
 }
 
 
@@ -864,8 +864,8 @@
    textures = { pics_dir .. "winter/taiga_00.png" },
    dither_layer = 250,
    temperature = 35,
-   humidity = 0.75,
-   fertility = 0.3,
+   humidity = 750,
+   fertility = 300,
 }
 
 
@@ -880,8 +880,8 @@
    textures = { pics_dir .. "winter/snow_00.png" },
    dither_layer = 250,
    temperature = 25,
-   humidity = 0.8,
-   fertility = 0.1,
+   humidity = 800,
+   fertility = 100,
 }
 
 
@@ -900,8 +900,8 @@
    textures = { pics_dir .. "winter/forested_mountain1_00.png" },
    dither_layer = 101,
    temperature = 35,
-   humidity = 0.7,
-   fertility = 0.4,
+   humidity = 700,
+   fertility = 400,
 }
 
 world:new_terrain_type{
@@ -919,8 +919,8 @@
    textures = { pics_dir .. "winter/forested_mountain2_00.png" },
    dither_layer = 101,
    temperature = 35,
-   humidity = 0.7,
-   fertility = 0.4,
+   humidity = 700,
+   fertility = 400,
 }
 
 world:new_terrain_type{
@@ -934,8 +934,8 @@
    textures = { pics_dir .. "winter/mountain1_00.png" },
    dither_layer = 110,
    temperature = 20,
-   humidity = 0.3,
-   fertility = 0.05,
+   humidity = 300,
+   fertility = 50,
 }
 
 
@@ -950,8 +950,8 @@
    textures = { pics_dir .. "winter/mountain2_00.png" },
    dither_layer = 110,
    temperature = 20,
-   humidity = 0.3,
-   fertility = 0.05,
+   humidity = 300,
+   fertility = 50,
 }
 
 
@@ -966,8 +966,8 @@
    textures = { pics_dir .. "winter/mountain3_00.png" },
    dither_layer = 100,
    temperature = 20,
-   humidity = 0.3,
-   fertility = 0.05,
+   humidity = 300,
+   fertility = 50,
 }
 
 
@@ -982,8 +982,8 @@
    textures = { pics_dir .. "winter/mountain4_00.png" },
    dither_layer = 100,
    temperature = 20,
-   humidity = 0.3,
-   fertility = 0.05,
+   humidity = 300,
+   fertility = 50,
 }
 world:new_terrain_type{
    name = "ice",
@@ -996,8 +996,8 @@
    textures = { pics_dir .. "winter/ice_00.png" },
    dither_layer = 260,
    temperature = 25,
-   humidity = 0.5,
-   fertility = 0.1,
+   humidity = 500,
+   fertility = 100,
 }
 
 
@@ -1012,8 +1012,8 @@
    textures = { pics_dir .. "winter/beach_00.png" },
    dither_layer = 40,
    temperature = 60,
-   humidity = 0.5,
-   fertility = 0.1,
+   humidity = 500,
+   fertility = 100,
 }
 
 
@@ -1029,8 +1029,8 @@
    dither_layer = 210,
    fps = 5,
    temperature = 50,
-   humidity = 0.999,
-   fertility = 0.001,
+   humidity = 999,
+   fertility = 1,
 }
 
 
@@ -1046,8 +1046,8 @@
    dither_layer = 210,
    fps = 5,
    temperature = 50,
-   humidity = 0.999,
-   fertility = 0.001,
+   humidity = 999,
+   fertility = 1,
 }
 
 
@@ -1063,8 +1063,8 @@
    dither_layer = 190,
    fps = 8,
    temperature = 50,
-   humidity = 0.999,
-   fertility = 0.001,
+   humidity = 999,
+   fertility = 1,
 }
 
 
@@ -1083,8 +1083,8 @@
    textures = { pics_dir .. "desert/desert4_00.png" },
    dither_layer = 270,
    temperature = 168,
-   humidity = 0.001,
-   fertility = 0.1,
+   humidity = 1,
+   fertility = 100,
 }
 
 world:new_terrain_type{
@@ -1098,8 +1098,8 @@
    textures = { pics_dir .. "desert/drysoil_00.png" },
    dither_layer = 300,
    temperature = 172,
-   humidity = 0.2,
-   fertility = 0.2,
+   humidity = 200,
+   fertility = 200,
 }
 world:new_terrain_type{
    name = "desert_steppe",
@@ -1116,8 +1116,8 @@
    textures = { pics_dir .. "desert/steppe_00.png" },
    dither_layer = 360,
    temperature = 155,
-   humidity = 0.5,
-   fertility = 0.5,
+   humidity = 500,
+   fertility = 500,
 }
 
 
@@ -1136,8 +1136,8 @@
    textures = { pics_dir .. "desert/meadow_00.png" },
    dither_layer = 310,
    temperature = 160,
-   humidity = 0.6,
-   fertility = 0.6,
+   humidity = 600,
+   fertility = 600,
 }
 
 
@@ -1156,8 +1156,8 @@
    textures = { pics_dir .. "desert/mountainmeadow_00.png" },
    dither_layer = 150,
    temperature = 145,
-   humidity = 0.5,
-   fertility = 0.5,
+   humidity = 500,
+   fertility = 500,
 }
 
 
@@ -1176,8 +1176,8 @@
    textures = { pics_dir .. "desert/highmountainmeadow_00.png" },
    dither_layer = 150,
    temperature = 140,
-   humidity = 0.4,
-   fertility = 0.4,
+   humidity = 400,
+   fertility = 400,
 }
 
 
@@ -1196,8 +1196,8 @@
    textures = { pics_dir .. "desert/forested_mountain1_00.png" },
    dither_layer = 71,
    temperature = 141,
-   humidity = 0.5,
-   fertility = 0.5,
+   humidity = 500,
+   fertility = 500,
 }
 
 world:new_terrain_type{
@@ -1215,8 +1215,8 @@
    textures = { pics_dir .. "desert/forested_mountain2_00.png" },
    dither_layer = 141,
    temperature = 120,
-   humidity = 0.5,
-   fertility = 0.5,
+   humidity = 500,
+   fertility = 500,
 }
 
 
@@ -1231,8 +1231,8 @@
    textures = { pics_dir .. "desert/mountain1_00.png" },
    dither_layer = 120,
    temperature = 130,
-   humidity = 0.05,
-   fertility = 0.05,
+   humidity = 50,
+   fertility = 50,
 }
 
 
@@ -1247,8 +1247,8 @@
    textures = { pics_dir .. "desert/mountain2_00.png" },
    dither_layer = 120,
    temperature = 130,
-   humidity = 0.05,
-   fertility = 0.05,
+   humidity = 50,
+   fertility = 50,
 }
 
 
@@ -1263,8 +1263,8 @@
    textures = { pics_dir .. "desert/mountain3_00.png" },
    dither_layer = 130,
    temperature = 130,
-   humidity = 0.05,
-   fertility = 0.05,
+   humidity = 50,
+   fertility = 50,
 }
 
 
@@ -1279,8 +1279,8 @@
    textures = { pics_dir .. "desert/mountain4_00.png" },
    dither_layer = 140,
    temperature = 130,
-   humidity = 0.05,
-   fertility = 0.05,
+   humidity = 50,
+   fertility = 50,
 }
 world:new_terrain_type{
    name = "desert1",
@@ -1293,8 +1293,8 @@
    textures = { pics_dir .. "desert/desert1_00.png" },
    dither_layer = 290,
    temperature = 167,
-   humidity = 0.001,
-   fertility = 0.001,
+   humidity = 1,
+   fertility = 1,
 }
 
 
@@ -1309,8 +1309,8 @@
    textures = { pics_dir .. "desert/desert2_00.png" },
    dither_layer = 280,
    temperature = 168,
-   humidity = 0.001,
-   fertility = 0.001,
+   humidity = 1,
+   fertility = 1,
 }
 
 
@@ -1325,8 +1325,8 @@
    textures = { pics_dir .. "desert/desert3_00.png" },
    dither_layer = 280,
    temperature = 178,
-   humidity = 0.001,
-   fertility = 0.001,
+   humidity = 1,
+   fertility = 1,
 }
 
 
@@ -1341,8 +1341,8 @@
    textures = { pics_dir .. "desert/beach_00.png" },
    dither_layer = 60,
    temperature = 179,
-   humidity = 0.5,
-   fertility = 0.1,
+   humidity = 500,
+   fertility = 100,
 }
 
 
@@ -1358,6 +1358,6 @@
    dither_layer = 200,
    fps = 5,
    temperature = 150,
-   humidity = 0.999,
-   fertility = 0.001,
+   humidity = 999,
+   fertility = 1,
 }
 
=== modified file 'src/logic/game.cc'
--- src/logic/game.cc	2018-11-23 08:20:36 +0000
+++ src/logic/game.cc	2018-11-23 12:45:17 +0000
@@ -1076,8 +1076,4 @@
 		fw.unsigned_32(general_stats_[p - 1].custom_statistic[j]);
 	}
 }
-
-double logic_rand_as_double(Game* game) {
-	return static_cast<double>(game->logic_rand()) / std::numeric_limits<uint32_t>::max();
-}
 }
 
=== modified file 'src/logic/game.h'
--- src/logic/game.h	2018-10-21 09:42:03 +0000
+++ src/logic/game.h	2018-11-23 12:45:17 +0000
@@ -347,9 +347,6 @@
 	location.y += logic_rand() % s - radius;
 	return location;
 }
-
-// Returns a value between [0., 1].
-double logic_rand_as_double(Game* game);
 }
 
 #endif  // end of include guard: WL_LOGIC_GAME_H
 
=== modified file 'src/logic/map_objects/immovable.cc'
--- src/logic/map_objects/immovable.cc	2018-09-25 06:32:35 +0000
+++ src/logic/map_objects/immovable.cc	2018-11-23 12:45:17 +0000
@@ -943,7 +943,7 @@
 	FCoords const f = map.get_fcoords(immovable.get_position());
 	const ImmovableDescr& descr = immovable.descr();
 
-	if (logic_rand_as_double(&game) <
+	if ((game.logic_rand() % TerrainAffinity::kPrecisionFactor) <
 	    probability_to_grow(descr.terrain_affinity(), f, map, game.world().terrains())) {
 		MapObjectDescr::OwnerType owner_type = descr.owner_type();
 		Player* owner = immovable.get_owner();
@@ -1030,7 +1030,7 @@
 	FCoords const f = map.get_fcoords(immovable.get_position());
 	const ImmovableDescr& descr = immovable.descr();
 
-	if (logic_rand_as_double(&game) <
+	if ((game.logic_rand() % TerrainAffinity::kPrecisionFactor) <
 	    probability_to_grow(descr.terrain_affinity(), f, map, game.world().terrains())) {
 		// Seed a new tree.
 		MapFringeRegion<> mr(map, Area<>(f, 0));
@@ -1047,7 +1047,7 @@
 		const FCoords new_location = map.get_fcoords(mr.location());
 		if (!new_location.field->get_immovable() &&
 		    (new_location.field->nodecaps() & MOVECAPS_WALK) &&
-		    logic_rand_as_double(&game) < probability_to_grow(descr.terrain_affinity(), new_location,
+		    (game.logic_rand() % TerrainAffinity::kPrecisionFactor) < probability_to_grow(descr.terrain_affinity(), new_location,
 		                                                      map, game.world().terrains())) {
 			game.create_immovable_with_name(mr.location(), type_name, descr.owner_type(),
 			                                nullptr /* owner */, nullptr /* former_building_descr */);
 
=== modified file 'src/logic/map_objects/terrain_affinity.cc'
--- src/logic/map_objects/terrain_affinity.cc	2018-04-07 16:59:00 +0000
+++ src/logic/map_objects/terrain_affinity.cc	2018-11-23 12:45:17 +0000
@@ -33,113 +33,122 @@
 
 namespace {
 
-constexpr double pow2(const double& a) {
+// Literature on cross-platform floating point precision-problems:
+// https://arxiv.org/abs/cs/0701192
+// Monniaux, David (2008): "The pitfalls of verifying floating-point computations",
+// in: ACM Transactions on Programming Languages and Systems 30, 3 (2008) 12.
+//
+// Recommends using heximal float constants, but we'd need to switch to C++17 for that.
+//
+// https://randomascii.wordpress.com/2012/03/21/intermediate-floating-point-precision/
+
+constexpr double square(const double& a) {
 	return a * a;
 }
 
 // Helper function for probability_to_grow
 // Calculates the probability to grow for the given affinity and terrain values
-double calculate_probability_to_grow(const TerrainAffinity& affinity,
-                                     double terrain_humidity,
-                                     double terrain_fertility,
-                                     double terrain_temperature) {
-
-	constexpr double kHumidityWeight = 0.500086642549548;
-	constexpr double kFertilityWeight = 0.5292268046607387;
-	constexpr double kTemperatureWeight = 61.31300863608306;
-
-	const double sigma_humidity = (1. - affinity.pickiness());
-	const double sigma_temperature = (1. - affinity.pickiness());
-	const double sigma_fertility = (1. - affinity.pickiness());
-
-	return exp((-pow2((affinity.preferred_fertility() - terrain_fertility) /
-	                  (kFertilityWeight * sigma_fertility)) -
-	            pow2((affinity.preferred_humidity() - terrain_humidity) /
-	                 (kHumidityWeight * sigma_humidity)) -
-	            pow2((affinity.preferred_temperature() - terrain_temperature) /
-	                 (kTemperatureWeight * sigma_temperature))) /
-	           2);
+inline unsigned int calculate_probability_to_grow(const TerrainAffinity& affinity,
+                                     int terrain_humidity,
+                                     int terrain_fertility,
+                                     int terrain_temperature) {
+	constexpr double kHumidityWeight = 5.00086642549548;
+	constexpr double kFertilityWeight = 5.292268046607387;
+	constexpr double kTemperatureWeight = 0.6131300863608306;
+
+    // Avoid division by 0
+    assert(affinity.pickiness() < 100);
+	const double sigma = std::floor(100.0 - affinity.pickiness());
+
+	// Unlike real numbers, floating point multiplication/division is neither associative nor commutative. Fortunately, execution order is well-defined by the C++ standard.
+	const double result = exp(-
+							  (square((affinity.preferred_fertility() - terrain_fertility) / (kFertilityWeight * sigma)) +
+							   square((affinity.preferred_humidity() - terrain_humidity) / (kHumidityWeight * sigma)) +
+							   square((affinity.preferred_temperature() - terrain_temperature) / (kTemperatureWeight * sigma))) / 2.0);
+
+    return static_cast<unsigned int>(std::max(0.0, std::floor(result * static_cast<double>(TerrainAffinity::kPrecisionFactor))));
 }
 
 }  // namespace
 
 TerrainAffinity::TerrainAffinity(const LuaTable& table, const std::string& immovable_name)
-   : preferred_fertility_(table.get_double("preferred_fertility")),
-     preferred_humidity_(table.get_double("preferred_humidity")),
-     preferred_temperature_(table.get_double("preferred_temperature")),
-     pickiness_(table.get_double("pickiness")) {
-	if (!(0 <= preferred_fertility_ && preferred_fertility_ <= 1.)) {
-		throw GameDataError("%s: preferred_fertility is not in [0, 1].", immovable_name.c_str());
-	}
-	if (!(0 <= preferred_humidity_ && preferred_humidity_ <= 1.)) {
-		throw GameDataError("%s: preferred_humidity is not in [0, 1].", immovable_name.c_str());
-	}
-	if (!(0 <= pickiness_ && pickiness_ <= 1.)) {
-		throw GameDataError("%s: pickiness is not in [0, 1].", immovable_name.c_str());
+   : preferred_fertility_(table.get_int("preferred_fertility")),
+     preferred_humidity_(table.get_int("preferred_humidity")),
+     preferred_temperature_(table.get_int("preferred_temperature")),
+     pickiness_(table.get_int("pickiness")) {
+	if (!(0 <= preferred_fertility_ && preferred_fertility_ <= 1000)) {
+		throw GameDataError("%s: preferred_fertility is not in [0, 1000].", immovable_name.c_str());
+	}
+	if (!(0 <= preferred_humidity_ && preferred_humidity_ <= 1000)) {
+		throw GameDataError("%s: preferred_humidity is not in [0, 1000].", immovable_name.c_str());
+	}
+	if (!(0 <= pickiness_ && pickiness_ < 100)) {
+		throw GameDataError("%s: pickiness is not in [0, 99].", immovable_name.c_str());
 	}
 	if (preferred_temperature_ < 0) {
 		throw GameDataError("%s: preferred_temperature is not possible.", immovable_name.c_str());
 	}
 }
 
-double TerrainAffinity::preferred_temperature() const {
+int TerrainAffinity::preferred_temperature() const {
 	return preferred_temperature_;
 }
 
-double TerrainAffinity::preferred_fertility() const {
+int TerrainAffinity::preferred_fertility() const {
 	return preferred_fertility_;
 }
 
-double TerrainAffinity::preferred_humidity() const {
+int TerrainAffinity::preferred_humidity() const {
 	return preferred_humidity_;
 }
 
-double TerrainAffinity::pickiness() const {
+int TerrainAffinity::pickiness() const {
 	return pickiness_;
 }
 
-double probability_to_grow(const TerrainAffinity& affinity,
+unsigned int probability_to_grow(const TerrainAffinity& affinity,
                            const FCoords& fcoords,
                            const Map& map,
                            const DescriptionMaintainer<TerrainDescription>& terrains) {
-	double terrain_humidity = 0;
-	double terrain_fertility = 0;
-	double terrain_temperature = 0;
+	// Initialize with 3 to get proper rounding with the integer division in the return statement
+	int terrain_humidity = 3;
+	int terrain_fertility = 3;
+	int terrain_temperature = 3;
 
-	const auto average = [&terrain_humidity, &terrain_fertility, &terrain_temperature,
+	const auto sum_up_values = [&terrain_humidity, &terrain_fertility, &terrain_temperature,
 	                      &terrains](const int terrain_index) {
 		const TerrainDescription& t = terrains.get(terrain_index);
-		terrain_humidity += t.humidity() / 6.;
-		terrain_temperature += t.temperature() / 6.;
-		terrain_fertility += t.fertility() / 6.;
+		terrain_humidity += t.humidity();
+		terrain_temperature += t.temperature();
+		terrain_fertility += t.fertility();
 	};
 
-	average(fcoords.field->terrain_d());
-	average(fcoords.field->terrain_r());
+	sum_up_values(fcoords.field->terrain_d());
+	sum_up_values(fcoords.field->terrain_r());
 	{
 		FCoords tln;
 		map.get_tln(fcoords, &tln);
-		average(tln.field->terrain_d());
-		average(tln.field->terrain_r());
+		sum_up_values(tln.field->terrain_d());
+		sum_up_values(tln.field->terrain_r());
 	}
 
 	{
 		FCoords trn;
 		map.get_trn(fcoords, &trn);
-		average(trn.field->terrain_d());
+		sum_up_values(trn.field->terrain_d());
 	}
 
 	{
 		FCoords ln;
 		map.get_ln(fcoords, &ln);
-		average(ln.field->terrain_r());
+		sum_up_values(ln.field->terrain_r());
 	}
 
 	return calculate_probability_to_grow(
-	   affinity, terrain_humidity, terrain_fertility, terrain_temperature);
+	   affinity, terrain_humidity / 6, terrain_fertility / 6, terrain_temperature / 6);
 }
 
-double probability_to_grow(const TerrainAffinity& affinity, const TerrainDescription& terrain) {
+unsigned int probability_to_grow(const TerrainAffinity& affinity, const TerrainDescription& terrain) {
 
 	return calculate_probability_to_grow(
 	   affinity, terrain.humidity(), terrain.fertility(), terrain.temperature());
 
=== modified file 'src/logic/map_objects/terrain_affinity.h'
--- src/logic/map_objects/terrain_affinity.h	2018-04-07 16:59:00 +0000
+++ src/logic/map_objects/terrain_affinity.h	2018-11-23 12:45:17 +0000
@@ -31,7 +31,6 @@
 
 class Map;
 class TerrainDescription;
-class World;
 struct FCoords;
 
 // Describes the parameters and the pickiness of Immovables towards terrain
@@ -39,39 +38,46 @@
 // define this.
 class TerrainAffinity {
 public:
+    static constexpr int kPrecisionFactor = 1 << 26;
+
 	explicit TerrainAffinity(const LuaTable& table, const std::string& immovable_name);
 
 	// Preferred temperature is in arbitrary units.
-	double preferred_temperature() const;
-
-	// Preferred fertility in percent [0, 1].
-	double preferred_fertility() const;
-
-	// Preferred humidity in percent [0, 1].
-	double preferred_humidity() const;
-
-	// A value in [0, 1] that defines how well this can deal with non-ideal
+	int preferred_temperature() const;
+
+	// Preferred fertility, ranging from 0 to 1000.
+	int preferred_fertility() const;
+
+	// Preferred humidity, ranging from 0 to 1000.
+	int preferred_humidity() const;
+
+	// A value in [0, 99] that defines how well this can deal with non-ideal
 	// situations. Lower means it is less picky, i.e. it can deal better.
-	double pickiness() const;
+	int pickiness() const;
 
 private:
-	double preferred_fertility_;
-	double preferred_humidity_;
-	double preferred_temperature_;
-	double pickiness_;
+	const int preferred_fertility_;
+	const int preferred_humidity_;
+	const int preferred_temperature_;
+	const int pickiness_;
 
 	DISALLOW_COPY_AND_ASSIGN(TerrainAffinity);
 };
 
-// Returns a value in [0., 1.] that describes the suitability for the
-// 'immovable_affinity' for 'field'. Higher is better suited.
-double probability_to_grow(const TerrainAffinity& immovable_affinity,
+/**
+ * Returns a value in [0, TerrainAffinity::kPrecisionFactor] that describes the suitability for the 'immovable_affinity' for all 6 terrains around 'field'.
+ * Higher is better suited, with TerrainAffinity::kPrecisionFactor representing a probability of 1.
+ * */
+unsigned int probability_to_grow(const TerrainAffinity& immovable_affinity,
                            const FCoords& fcoords,
                            const Map& map,
                            const DescriptionMaintainer<TerrainDescription>& terrains);
 
-// Probability to grow for a single terrain
-double probability_to_grow(const TerrainAffinity& immovable_affinity,
+/**
+ * Returns a value in [0, TerrainAffinity::kPrecisionFactor] that describes the suitability for the 'immovable_affinity' for a single 'terrain'.
+ * Higher is better suited, with TerrainAffinity::kPrecisionFactor representing a probability of 1.
+ * */
+unsigned int probability_to_grow(const TerrainAffinity& immovable_affinity,
                            const TerrainDescription& terrain);
 
 }  // namespace Widelands
 
=== modified file 'src/logic/map_objects/tribes/worker.cc'
--- src/logic/map_objects/tribes/worker.cc	2018-11-07 10:19:29 +0000
+++ src/logic/map_objects/tribes/worker.cc	2018-11-23 12:45:17 +0000
@@ -452,11 +452,11 @@
 	const uint32_t attribute_id = ImmovableDescr::get_attribute_id("tree_sapling");
 
 	const DescriptionMaintainer<TerrainDescription>& terrains = game.world().terrains();
-	double best = 0.0;
+	int best = 0;
 	for (DescriptionIndex i = 0; i < immovables.size(); ++i) {
 		const ImmovableDescr& immovable_descr = immovables.get(i);
 		if (immovable_descr.has_attribute(attribute_id) && immovable_descr.has_terrain_affinity()) {
-			double probability =
+			int probability =
 			   probability_to_grow(immovable_descr.terrain_affinity(), fpos, map, terrains);
 			if (probability > best) {
 				best = probability;
@@ -464,7 +464,7 @@
 		}
 	}
 	// normalize value to int16 range
-	const int16_t correct_val = (std::numeric_limits<int16_t>::max() - 1) * best;
+	const int16_t correct_val = (std::numeric_limits<int16_t>::max() - 1) * (static_cast<double>(best) / TerrainAffinity::kPrecisionFactor);
 
 	if (x_check && (correct_val != cache_entry)) {
 		forester_cache.clear();
@@ -798,7 +798,7 @@
 	// affinity). We will pick one of them at random later. The container is
 	// picked to be a stable sorting one, so that no deyncs happen in
 	// multiplayer.
-	std::set<std::tuple<double, DescriptionIndex, MapObjectDescr::OwnerType>>
+	std::set<std::tuple<int, DescriptionIndex, MapObjectDescr::OwnerType>>
 	   best_suited_immovables_index;
 
 	// Checks if the 'immovable_description' has a terrain_affinity, if so use it. Otherwise assume
@@ -809,7 +809,7 @@
 		if (!immovable_description.has_attribute(attribute_id)) {
 			return;
 		}
-		double p = 1.;
+		int p = TerrainAffinity::kPrecisionFactor;
 		if (immovable_description.has_terrain_affinity()) {
 			p = probability_to_grow(
 			   immovable_description.terrain_affinity(), fpos, map, game.world().terrains());
@@ -856,18 +856,18 @@
 	// Randomly pick one of the immovables to be planted.
 
 	// Each candidate is weighted by its probability to grow.
-	double total_weight = 0.0;
+	int total_weight = 0;
 	for (const auto& bsii : best_suited_immovables_index) {
-		double weight = std::get<0>(bsii);
-		total_weight += weight * weight;
+		const int weight = std::get<0>(bsii);
+		total_weight += weight;
 	}
 
-	double choice = logic_rand_as_double(&game) * total_weight;
+	int choice = game.logic_rand() % total_weight;
 	for (const auto& bsii : best_suited_immovables_index) {
-		double weight = std::get<0>(bsii);
+		const int weight = std::get<0>(bsii);
 		state.ivar2 = std::get<1>(bsii);
 		state.ivar3 = static_cast<int>(std::get<2>(bsii));
-		choice -= weight * weight;
+		choice -= weight;
 		if (0 > choice) {
 			break;
 		}
 
=== modified file 'src/logic/map_objects/world/terrain_description.cc'
--- src/logic/map_objects/world/terrain_description.cc	2018-04-07 16:59:00 +0000
+++ src/logic/map_objects/world/terrain_description.cc	2018-11-23 12:45:17 +0000
@@ -105,19 +105,19 @@
      default_resource_index_(world.get_resource(table.get_string("default_resource").c_str())),
      default_resource_amount_(table.get_int("default_resource_amount")),
      dither_layer_(table.get_int("dither_layer")),
-     temperature_(table.get_double("temperature")),
-     fertility_(table.get_double("fertility")),
-     humidity_(table.get_double("humidity")) {
+     temperature_(table.get_int("temperature")),
+     fertility_(table.get_int("fertility")),
+     humidity_(table.get_int("humidity")) {
 
 	if (table.has_key("tooltips")) {
 		custom_tooltips_ = table.get_table("tooltips")->array_entries<std::string>();
 	}
 
-	if (!(0 < fertility_ && fertility_ < 1.)) {
-		throw GameDataError("%s: fertility is not in (0, 1).", name_.c_str());
+	if (!(0 < fertility_ && fertility_ < 1000)) {
+		throw GameDataError("%s: fertility is not in (0, 1000).", name_.c_str());
 	}
-	if (!(0 < humidity_ && humidity_ < 1.)) {
-		throw GameDataError("%s: humidity is not in (0, 1).", name_.c_str());
+	if (!(0 < humidity_ && humidity_ < 1000)) {
+		throw GameDataError("%s: humidity is not in (0, 1000).", name_.c_str());
 	}
 	if (temperature_ < 0) {
 		throw GameDataError("%s: temperature is not possible.", name_.c_str());
@@ -244,15 +244,15 @@
 	return dither_layer_;
 }
 
-double TerrainDescription::temperature() const {
+int TerrainDescription::temperature() const {
 	return temperature_;
 }
 
-double TerrainDescription::humidity() const {
+int TerrainDescription::humidity() const {
 	return humidity_;
 }
 
-double TerrainDescription::fertility() const {
+int TerrainDescription::fertility() const {
 	return fertility_;
 }
 
 
=== modified file 'src/logic/map_objects/world/terrain_description.h'
--- src/logic/map_objects/world/terrain_description.h	2018-04-27 06:11:05 +0000
+++ src/logic/map_objects/world/terrain_description.h	2018-11-23 12:45:17 +0000
@@ -115,13 +115,13 @@
 
 	/// Parameters for terrain affinity of immovables.
 	/// Temperature is in arbitrary units.
-	double temperature() const;
-
-	/// Humidity in percent [0, 1].
-	double humidity() const;
-
-	/// Fertility in percent [0, 1].
-	double fertility() const;
+	int temperature() const;
+
+	/// Humidity, ranging from 0 to 1000.
+	int humidity() const;
+
+	/// Fertility, ranging from 0 to 1000.
+	int fertility() const;
 
 	/// Additional tooptip entries for the editor
 	const std::vector<std::string>& custom_tooltips() const {
@@ -139,9 +139,9 @@
 	int default_resource_amount_;
 	int dither_layer_;
 	int frame_length_;
-	double temperature_;
-	double fertility_;
-	double humidity_;
+	int temperature_;
+	int fertility_;
+	int humidity_;
 	std::vector<std::string> texture_paths_;
 	std::vector<const Image*> textures_;
 	RGBColor minimap_colors_[256];
 
=== modified file 'src/scripting/lua_map.cc'
--- src/scripting/lua_map.cc	2018-11-09 01:26:21 +0000
+++ src/scripting/lua_map.cc	2018-11-23 12:45:17 +0000
@@ -1927,8 +1927,8 @@
 
          returns the terrain affinity values for this immovable
 
-         (RO) a table containing numbers labeled as pickiness (double), preferred_fertility (double),
-         preferred_humidity (double), and preferred_temperature (uint),
+         (RO) a table containing numbers labeled as pickiness (uint), preferred_fertility (uint),
+         preferred_humidity (uint), and preferred_temperature (uint),
          or nil if the immovable has no terrain affinity.
 */
 int LuaImmovableDescription::get_terrain_affinity(lua_State* L) {
@@ -1936,13 +1936,13 @@
 		const TerrainAffinity& affinity = get()->terrain_affinity();
 		lua_newtable(L);
 		lua_pushstring(L, "pickiness");
-		lua_pushdouble(L, affinity.pickiness());
+		lua_pushuint32(L, affinity.pickiness());
 		lua_settable(L, -3);
 		lua_pushstring(L, "preferred_fertility");
-		lua_pushdouble(L, affinity.preferred_fertility());
+		lua_pushuint32(L, affinity.preferred_fertility());
 		lua_settable(L, -3);
 		lua_pushstring(L, "preferred_humidity");
-		lua_pushdouble(L, affinity.preferred_humidity());
+		lua_pushuint32(L, affinity.preferred_humidity());
 		lua_settable(L, -3);
 		lua_pushstring(L, "preferred_temperature");
 		lua_pushuint32(L, affinity.preferred_temperature());
@@ -2034,7 +2034,7 @@
 	if (get()->has_terrain_affinity()) {
 		const TerrainDescription* terrain =
 		   (*get_user_class<LuaMaps::LuaTerrainDescription>(L, 2))->get();
-		lua_pushdouble(L, Widelands::probability_to_grow(get()->terrain_affinity(), *terrain));
+		lua_pushdouble(L, Widelands::probability_to_grow(get()->terrain_affinity(), *terrain) / static_cast<double>(Widelands::TerrainAffinity::kPrecisionFactor));
 	} else {
 		lua_pushnil(L);
 	}
@@ -3513,22 +3513,22 @@
 /* RST
    .. attribute:: fertility
 
-         (RO) the :class:`double` fertility value for this terrain
+         (RO) the :class:`uint` fertility value for this terrain
 */
 
 int LuaTerrainDescription::get_fertility(lua_State* L) {
-	lua_pushdouble(L, get()->fertility());
+	lua_pushuint32(L, get()->fertility());
 	return 1;
 }
 
 /* RST
    .. attribute:: humidity
 
-         (RO) the :class:`double` humidity value for this terrain
+         (RO) the :class:`uint` humidity value for this terrain
 */
 
 int LuaTerrainDescription::get_humidity(lua_State* L) {
-	lua_pushdouble(L, get()->humidity());
+	lua_pushuint32(L, get()->humidity());
 	return 1;
 }
 
 
=== modified file 'test/maps/lua_testsuite.wmf/scripting/immovables_descriptions.lua'
--- test/maps/lua_testsuite.wmf/scripting/immovables_descriptions.lua	2018-09-29 05:10:39 +0000
+++ test/maps/lua_testsuite.wmf/scripting/immovables_descriptions.lua	2018-11-23 12:45:17 +0000
@@ -75,22 +75,22 @@
    local aff_umbrella_green_mature = egbase:get_immovable_description("umbrella_green_wasteland_mature").terrain_affinity
 
    -- Pickiness
-   assert_near(0.6, aff_alder_sapling["pickiness"], 0.01)
+   assert_equal(60, aff_alder_sapling["pickiness"])
    assert_equal(aff_alder_sapling["pickiness"], aff_alder_old["pickiness"])
-   assert_near(0.6, aff_mushroom_red_pole["pickiness"], 0.01)
-   assert_near(0.8, aff_umbrella_green_mature["pickiness"], 0.01)
+   assert_equal(60, aff_mushroom_red_pole["pickiness"])
+   assert_equal(80, aff_umbrella_green_mature["pickiness"])
 
    -- preferred_fertility
-   assert_near(0.6, aff_alder_sapling["preferred_fertility"], 0.01)
+   assert_equal(600, aff_alder_sapling["preferred_fertility"])
    assert_equal(aff_alder_sapling["preferred_fertility"], aff_alder_old["preferred_fertility"])
-   assert_near(0.85, aff_mushroom_red_pole["preferred_fertility"], 0.01)
-   assert_near(0.85, aff_umbrella_green_mature["preferred_fertility"], 0.01)
+   assert_equal(850, aff_mushroom_red_pole["preferred_fertility"])
+   assert_equal(850, aff_umbrella_green_mature["preferred_fertility"])
 
    -- preferred_humidity
-   assert_near(0.65, aff_alder_sapling["preferred_humidity"], 0.01)
+   assert_equal(650, aff_alder_sapling["preferred_humidity"])
    assert_equal(aff_alder_sapling["preferred_humidity"], aff_alder_old["preferred_humidity"])
-   assert_near(0.35, aff_mushroom_red_pole["preferred_humidity"], 0.01)
-   assert_near(0.2, aff_umbrella_green_mature["preferred_humidity"], 0.01)
+   assert_equal(350, aff_mushroom_red_pole["preferred_humidity"])
+   assert_equal(200, aff_umbrella_green_mature["preferred_humidity"])
 
    -- preferred_temperature
    assert_equal(125, aff_alder_sapling["preferred_temperature"])
 
=== modified file 'test/maps/lua_testsuite.wmf/scripting/terrains_resources_descriptions.lua'
--- test/maps/lua_testsuite.wmf/scripting/terrains_resources_descriptions.lua	2016-07-10 19:03:33 +0000
+++ test/maps/lua_testsuite.wmf/scripting/terrains_resources_descriptions.lua	2018-11-23 12:45:17 +0000
@@ -141,17 +141,17 @@
 end
 
 function test_terrains_resource_descr:test_terrain_fertility()
-   assert_near(0.7, egbase:get_terrain_description("summer_meadow1").fertility, 0.01)
-   assert_near(0.2, egbase:get_terrain_description("wasteland_beach").fertility, 0.01)
-   assert_near(0.5, egbase:get_terrain_description("desert_forested_mountain2").fertility, 0.01)
-   assert_near(0.001, egbase:get_terrain_description("winter_water").fertility, 0.0001)
+   assert_equal(700, egbase:get_terrain_description("summer_meadow1").fertility)
+   assert_equal(200, egbase:get_terrain_description("wasteland_beach").fertility)
+   assert_equal(500, egbase:get_terrain_description("desert_forested_mountain2").fertility)
+   assert_equal(1, egbase:get_terrain_description("winter_water").fertility)
 end
 
 function test_terrains_resource_descr:test_terrain_humidity()
-   assert_near(0.6, egbase:get_terrain_description("summer_meadow1").humidity, 0.01)
-   assert_near(0.4, egbase:get_terrain_description("wasteland_beach").humidity, 0.01)
-   assert_near(0.5, egbase:get_terrain_description("desert_forested_mountain2").humidity, 0.01)
-   assert_near(0.999, egbase:get_terrain_description("winter_water").humidity, 0.0001)
+   assert_equal(600, egbase:get_terrain_description("summer_meadow1").humidity)
+   assert_equal(400, egbase:get_terrain_description("wasteland_beach").humidity)
+   assert_equal(500, egbase:get_terrain_description("desert_forested_mountain2").humidity)
+   assert_equal(999, egbase:get_terrain_description("winter_water").humidity)
 end
 
 function test_terrains_resource_descr:test_terrain_temperature()