MASSTRANSIT 1103 PATCH
MASSTRANSIT 1103 CODE

Now, how would you guys out there suggest to patch it?

The riddle in the riddle that isn't solved, though, is: was this done on purpose? I guess we'll never know. The theoretical numbers seem to more or less match what people have reported in the various threads above, although some other unknown conditions may add variations.

Emperor = 4: (256*2/4) = 128 -> pollution bug triggered after Future Tech.

King = 3: (256*2/3) = 170 -> pollution bug triggered after Future Tech.

Prince = 2: (256*2/2) = 256 -> pollution bug triggered after Future Tech.

Warlord = 1: (256*2/1) = 512 -> pollution bug triggered after Future Tech.Chieftain = 0: (256*2/0) = +infinity -> pollution bug never triggered.In other words, as soon as one gets (256*2/difficultyLevel) Techs, pollution starts to get triggered at every turn. Then the RANDOM() call has a negative argument, for which it will always return zero. So we can see that multiple combination are possible, but the key to this bug lies in the RANDOM() call: what if CityOwnerTechCount * difficultyLevel / 2 is more than 256? PollutionFactor depends on the 'polluting' techs known by the player (INDUSTRIALIZATION=1, AUTOMOBILE=2, MASS PRODUCTION=3 and PLASTICS=4), and whether the city has a MASS TRANSIT (= 0). In the above, CityPollution is computed as explained in other threads:ĬityPollution = CityShields / CityPowerType - 20 + CitySize * PollutionFactorĬityPowerType depends on the power infrastructure in the city (default/power plant = 1, hydro/nuke plant = 2, recycling center = 3) IF ( 2 * CityPollution > Random(256 - CityOwnerTechCount * difficultyLevel / 2) ) THEN AddPollution Re-writing the condition in a single formula, it gives this:

MASSTRANSIT 1103 CODE

This code block is one of the first condition to be assessed when checking whether pollution should be spawned. Seg007:639A 10C cmp cx, ax Compare Two Operands Seg007:6398 10C shl cx, 1 Shift Logical Left Seg007:638C 10E call random_N Call Procedure Seg007:6389 10C neg ax Two's Complement Negation Seg007:6386 10C sub ax, 100h Integer Subtraction Seg007:6384 10C sar ax, 1 Shift Arithmetic Right Seg007:6382 10C sub ax, dx Integer Subtraction Seg007:637D 10C imul difficultyLevel Signed Multiply Seg007:6377 10C shl bx, 1 Shift Logical Left Seg007:636D 10C sub ax, dx Integer Subtraction Seg007:636B 10C xor ax, dx Logical Exclusive OR Seg007:6369 10C sar ax, cl Shift Arithmetic Right Seg007:6364 10C sub ax, dx Integer Subtraction Seg007:6362 10C xor ax, dx Logical Exclusive OR Seg007:635D 10C imul pollutionFactor_dseg_C7A2 Signed Multiply Seg007:6358 10C mov al, CityData.ActualSize Seg007:6349 10C sub ax, 14h Integer Subtraction Seg007:633F 10C mov ax, cityShieldsProd_dseg_705C Here the raw piece of assembly, for the die-hards out there: ).īack-tracking the call from the City Process routine, I could finally dig out what I believe to be the cause of this famous 'bug'. It seems this routine is used anytime pollution should be added to the map (nuke, city process. Some of the above links contain detailed game logic, extracted from 'Rome on 640K a Day' regarding pollution, namely how known Techs influence pollution, how a city's power source influence chimneys, how population influence pollution, as well as shields production (or did it?).Īnyhow, I had already identified a very small routine in CIV.EXE, that I bluntly called 'AddPollution(x, y)'. Did anyone try to remove the pollution? - Jun 2008.So, first thing, I looked up the forums for related threads, and here is what I found: Although I never put it at the center of my focus, stories about the 'pollution bug' have been kept roaming at the back of my mind ever since I became active on those forums, and read people mentioning it here and there.īeing more or less done with the City Process routine (I'm not done yet, in fact, but a bi tired ), I thought it would be more fun to investigate this so-called pollution bug one way or another.

Masstransit 1103