Any formula or way to figure out optimal hash size?
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jmartus
- Posts: 256
- Joined: Sun May 16, 2010 2:50 am
Any formula or way to figure out optimal hash size?
Is there any way to figure out the best hash table size or does it not really matter anyways?
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kranium
- Posts: 2129
- Joined: Thu May 29, 2008 10:43 am
Re: Any formula or way to figure out optimal hash size?
time per move (secs) * nodes per sec * hash entry size (in bytes)
for ex:
if time per move = 60 sec, nps = 700,000, and hash table entry = 16 bytes
(16 bytes being somewhat typical but can vary)
then:
60 secs x 700,000 nps x 16 bytes = 640 MB
to make this calculation you have to determine the engine's NPS on the hardware being used (run bench with same # of threads to be used, or observe output from command line).
that is the amount of RAM that will be used in a typical move for that time control
adding extra RAM might be useful, but a full hash table is not really a big problem as most modern hash algorithms age entries for replacement
My advice: give modern engines a lot of workspace (within reason), and as much as you can afford for analysis
and don't worry...
for ex:
if time per move = 60 sec, nps = 700,000, and hash table entry = 16 bytes
(16 bytes being somewhat typical but can vary)
then:
60 secs x 700,000 nps x 16 bytes = 640 MB
to make this calculation you have to determine the engine's NPS on the hardware being used (run bench with same # of threads to be used, or observe output from command line).
that is the amount of RAM that will be used in a typical move for that time control
adding extra RAM might be useful, but a full hash table is not really a big problem as most modern hash algorithms age entries for replacement
My advice: give modern engines a lot of workspace (within reason), and as much as you can afford for analysis
and don't worry...