2.08 and Incompatible Battle Reports

[alexti]

Originally posted by Johan K:
If we are lucky bug rogers is right here and the microsoft compiler bugs caused most of battle replay bugs. Even if there's something more wrong it should at least be better now.

In particular, if you were optimizing for speed.
And if you use MSVC6 (or 5), complier patches [surprisingly] don't include STL patches which you can get from http://www.dinkumware.com/vc_fixes.html

[Johan K]

Some good new for those who don't play Dominions on Windows exclusively. The problem with incompatible battle replays has been found. There was a disagrement on how to compile an expression between microsoft's and the others' compilers.

Magic resistance check:
if (penetration+2d6 < MR+2d6)

Other compiler solved it from left to right, but microsoft's solved it from right to left. This results in the same roll of dice appearing on different sides of the '<' for windows and linux.
Bloody annoying!


Alexti: Thanks for the STL info and I use MSVC6.

[ February 25, 2004, 17:35: Message edited by: Johan K ]

[Saber Cherry]

Yay! Not only was the problem solved, but also, Microsoft gets another black mark

[PhilD]

Originally posted by Johan K:
Some good new for those who don't play Dominions on Windows exclusively. The problem with incompatible battle replays has been found. There was a disagrement on how to compile an expression between microsoft's and the others' compilers.

Magic resistance check:
if (penetration+2d6 < MR+2d6)

Other compiler solved it from left to right, but microsoft's solved it from right to left. This results in the same roll of dice appearing on different sides of the '<' for windows and linux.
Bloody annoying!


Alexti: Thanks for the STL info and I use MSVC6.

Hmm... it's been some time since I had a look at books where the norm is described, but I'm not sure it says anything for this. I believe the result is "unspecified"...

Don't use two function calls in the same expression, is the lesson.

(And congrats on the Illwinter crew! When are we getting a patch so we can celebrate?)

[fahdiz]

Originally posted by PhilD:
(And congrats on the Illwinter crew! When are we getting a patch so we can celebrate?)

I second on both counts. After reading Arryn's AAR, Utgard is calling to me...

...unfortunately, it's calling from a moose-laden Smouldercone right now.

[Saber Cherry]

Originally posted by PhilD:
Don't use two function calls in the same expression, is the lesson.

Compliers do strange things. A poorly-written compiler could rearrange consecutive lines if there is no obvious dependancy.

1: a=2d6+penetration
2: b=2d6+mrst
3: if(a>b){do c}

Lines 1 & 2 could be rearranged by a compiler if, for example, mrst is more local (already in a register) and penetration has to be fetched. That would have the same effect. I think C has some commands that let you force the complier to not rearrange things, though.

So the moral is actually not to trust Microsoft products, since they take away your control

[Taqwus]

There may be #pragmas or compiler options to change reordering behavior, but I'm not too familiar with MSVC.
Wrapping the randomizer in an object and making sure that the "get a random number" method (perhaps as a static method, even) might serve as a hint to the compiler; could be more work than it's worth.

[edit] Making sure that it's not flagged as constant, that is. IOW to encourage the compiler to consider side-effects of function invocation.

[ February 25, 2004, 18:51: Message edited by: Taqwus ]