Index funtion for eval func

 Posts: 17
 Joined: Mon Oct 17, 2016 09:05
 Real name: Robin Messemer
Index funtion for eval func
Hey,
I am currently working on my evaluation function and wanted to copy the approach used by Scan and other programs. I use regions of the size 4x4 and need a good index function.
Currently, I use a base 5 index function which seems utterly wasteful.
(PseudoCode)
My board implementation uses 3 bitboards. BP=BlackPieces,WP=WhitePieces,K=Kings.
What index function are u using and could you explain why your index function works
I am currently working on my evaluation function and wanted to copy the approach used by Scan and other programs. I use regions of the size 4x4 and need a good index function.
Currently, I use a base 5 index function which seems utterly wasteful.
(PseudoCode)
Code: Select all
for(uint32_t i=0;i<8;++i){
uint32_t maske =1<<(i+shift);
if((maske&(bp&k))==maske){
index+=factor*4;
}else if((maske&(wp&k))==maske){
index+=factor*3;
}else if((maske&(bp))==maske){
index+=factor*2;
}else if((maske&(wp))==maske){
index+=factor*1;
}else{
index+=factor*0;
}
factor*=5;
}
}
What index function are u using and could you explain why your index function works

 Posts: 776
 Joined: Sat Apr 28, 2007 14:53
 Real name: Ed Gilbert
 Location: Morristown, NJ USA
 Contact:
Re: Index funtion for eval func
I'm looking at this now for use in an eval function for 8x8 English checkers. I think you can speed up the index calculation using the PEXT instrinsic that is available on newer CPUs.
 Ed
Why do you say it is wasteful?Currently, I use a base 5 index function which seems utterly wasteful.
 Ed

 Posts: 17
 Joined: Mon Oct 17, 2016 09:05
 Real name: Robin Messemer
Re: Index funtion for eval func
Oh, I thought there were better index functions. Better = less memory
I am using this for checkers as well and initial resullts were quite promising. May I ask which optimization algorithm u use for the logistic regression ? I tried stochastic graidient descent which works but is still rather slow. The Gauss Newton method is next on my list if I find a good matrix library which supports sparse matrices
I am using this for checkers as well and initial resullts were quite promising. May I ask which optimization algorithm u use for the logistic regression ? I tried stochastic graidient descent which works but is still rather slow. The Gauss Newton method is next on my list if I find a good matrix library which supports sparse matrices

 Posts: 776
 Joined: Sat Apr 28, 2007 14:53
 Real name: Ed Gilbert
 Location: Morristown, NJ USA
 Contact:
Re: Index funtion for eval func
Only if you want to consider compression. There are a lot of indexes that are not used because they don't represent quiet positions, or men of the wrong color on a king row. But even the simplest compression schemes like RLE are a lot slower, and I don't think it is a good tradeoff for an eval.Oh, I thought there were better index functions. Better = less memory
I'm using simple gradient descent, with a few iterations (epochs?) of minibatches before using the whole dataset for the remaining iterations. Convergence takes about 31/2 hours using 75M training positions. Nothing fancy, singlethreaded optimizer.May I ask which optimization algorithm u use for the logistic regression ?
 Ed

 Posts: 17
 Joined: Mon Oct 17, 2016 09:05
 Real name: Robin Messemer
Re: Index funtion for eval func
Intresting 75M position is really a lot and I am not even close to that. Did you use a fixed ply search when generating those games ? If so, how many plies were sufficient ? I am currently doing a 7 ply search during the "generatinggames"part.Takes me quite some time to generate a lot of unique positions

 Posts: 776
 Joined: Sat Apr 28, 2007 14:53
 Real name: Ed Gilbert
 Location: Morristown, NJ USA
 Contact:
Re: Index funtion for eval func
See this post for more details: viewtopic.php?f=53&t=6808&p=114452#p114452 With two 8core computers it takes a few weeks to play ~1M games.Did you use a fixed ply search when generating those games ?
 Ed
Re: Index funtion for eval func
I wouldn't bother with stochastic methods; the eval score function is a simple convex function. Stochastic methods just add complexity in this case.CheckersGuy wrote:Oh, I thought there were better index functions. Better = less memory
I am using this for checkers as well and initial resullts were quite promising. May I ask which optimization algorithm u use for the logistic regression ? I tried stochastic graidient descent which works but is still rather slow. The Gauss Newton method is next on my list if I find a good matrix library which supports sparse matrices
I am using a multithreaded conjungated gradient algorithm for optimization . It works fairly well, but gradient descent works as well and is much easier to program.
For small number of weights and data points dragon runs pretty quickly. As the number of weights/data points increase, they don't fit into cache anymore and the algorithm slows down.
As for the number of training positions; i think 510 million is a good point to start and experiment with. As you increase the training set, the performance will keep increasing every time you double the amount of positions.
Michel