Writing bugs

[Rebel]

Funnily enough I made the same mistake today, but the compiler caught it for me. (See here.)

[Rebel]

Nothing wring with

if((x&1) != engine) ...

If you dislike parentheses, you could also do

if(x-engine & 1) ...

I wouldn't say adding unnecessary dummy variables is "the right way to do it".

Maybe not, but I left it, it's a great reminder!

[chrisw]

Took me a while to track this one down .....

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while(the cows come home)
{
	selfplay(engine_1, engine_1)
	append game to file
	engine_weights += initial_weights + random(small_variation)
}

which produces lots of varied games.
Then same thing in parallel, the equivalent of this loop:

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for thread in range(cores)
{
	while(the cows come home)
	{
		selfplay(engine_1, engine_1)
		append game to file(thread)
		engine_weights += initial_weights + random(small_variation)
	}		
}
concatenate(files)

What could possibly go wrong?

[Ras]

What could possibly go wrong?

If one thread finishes its game early and modifies the engine weights while the other threads are still playing, they might not like that? Also, it looks strange with the "+=" in both cases, but probably more serious in the parallel case.

[chrisw]

What could possibly go wrong?

If one thread finishes its game early and modifies the engine weights while the other threads are still playing, they might not like that? Also, it looks strange with the "+=" in both cases, but probably more serious in the parallel case.

pardon the sloppy pseudo code.

no, it's a more general problem ...

[Fulvio]

no, it's a more general problem ...

https://stackoverflow.com/questions/212 ... om-numbers

[chrisw]

no, it's a more general problem ...

https://stackoverflow.com/questions/212 ... om-numbers

Each parallel batch contains identical games is (was) the problem

[mar]

Each parallel batch contains identical games is (was) the problem

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int random() {return 42;}

Wait - could this possibly be related to the fact that you used Python, where threads are completely useless due to GIL and you have to use multiple processes?

Then your "bug" is directly related to the language "features" you used, not at all to the pseudo-code which tells absolutely nothing.

[mar]

Ok, seriously: you forgot to reseed, no big deal.
This is suspicious as well:

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engine_weights += initial_weights + random(small_variation)

as it would skyrocket the weights quickly. I believe the first += should actually be =

[mcostalba]

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for (x = engine; x < MAX_MOVES; x += 2)

If x <= MAX_MOVES happens to be correct, then make it wrong fixing the definition somewhere else: it should really be wrong