[Bug]: Inflation breaks negative cargo payments #9440
Comments
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Can you please check the cargo payment rates graph as well pre- and post-inflation and post your findings? |
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As intended, without inflation: With inflation: |
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I can tell that the erratic cargo payment rate is highly dependent on the least significant bits (i.e. fractional part) of the inflation income factor. If the inflation income factor is an integer, normal behavior is exhibited, but if the inflation income factor is not an integer, that very easily leads to the erratic behavior shown. For example, there is an overflow in the cargo payment rates for imported cargoes that is triggered when the inflation income factor is greater than 0.5 (modulo 1.0): For comparison, cargo payment rates where the inflation income factor is set to exactly 1.00000: Cargo payment rates where the inflation income factor is set to exactly 1.00003: Cargo payment rates where the inflation income factor is set to exactly 1.50000: Cargo payment rates where the inflation income factor is set to exactly 1.50003: Cargo payment rates where the inflation income factor is set to exactly 1.99999: Cargo payment rates where the inflation income factor is set to exactly 2.00000 is the same as with 1.00000, just the magnitudes are doubled. ... Cargo payment rates where the inflation income factor is set to exactly 10,000.501: |
Cargo payments were stored as unsigned integer, but cast to int64 during application of inflation. However, then being multiplied with a uint64 making the result uint64. So in the end the payment that should have been negative becomes hugely positive.
Cargo payments were stored as unsigned integer, but cast to int64 during application of inflation. However, then being multiplied with a uint64 making the result uint64. So in the end the payment that should have been negative becomes hugely positive.
Version of OpenTTD
OpenTTD 1.11.2, Windows 10
Expected result
My NewGRF industry set, Industries of the Caribbean, uses negative cargo rates set in the NML properties (not the profit callback, where a known issue exists).
When Inflation is disabled, this works as intended. A cargo delivery like that in the savegame attached below costs the company about -£50.
Actual result
When Inflation is enabled, that -£50 cargo delivery instead gives £205 million.
Steps to reproduce
A user provided this savegame illustrating the issue.
IOTC_inflation_bug.zip
When a new map is started with Inflation disabled and the same set of NewGRFs, the profit works as intended.
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