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Thursday, January 7, 2016

Stockfish 7...which version?!

   As I mentioned in my recent post on Stockfish 7, it comes with several versions: 32-bit, 64-bit, 64-bit bmi2 and 64-bit popcnt, but I had no idea what the last two were.  The 64-bit bmi2 won't run on my laptop because it's too old.  Since then I discovered the following explanation on Chess2U which "explains" the popcnt version.  If I understand the writer correctly, if your processor was released in 2008 or later then you should use the popcnt version.  Although the popcnt version seems to run OK on my laptop, the processor is dated 2004 so I assume that for me, the 64-bit version is the best.
    A quick engine match using both versions running on a single core resulted in 5 draws, so  apparently it doesn't make much difference which version I actually use.  Maybe my laptop just does not utilize the popcnt feature...I don't know.
     In the following position from a recent online game white (me) is to move:

The results after 10 minutes: 

First Choice: 17.a4 
Evaluation: white's favor at 0.91 
Depth: 29 plies 
kN/s: 2536 

First Choice: 17.a4 
Evaluation: white's favor at 0.85 
Depth: 30 plies 
kN/s: 2235

Komodo 8 (as a comparison)
First Choice: 17.a4 
Evaluation: white's favor at 0.77 
Depth: 23 plies 
kN/s: 2551

So, it does not appear that it matters a whole lot which version of SF I use on my machine. Any computer gurus have a comment?

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