Large Pages or Bigger Hash?

[RJN]

I have a computer with 16 GB of memory. If I wanted to analyze a position for about 30 minutes, using an engine that supported Large Pages (such as Houdini 3 Pro, or Critter 1.6a), which would be better?

1) Maximum LP size I can use is 4 GB, which gives about a 10% speedup.

2) Maximum regular hash I can use is 8 GB.

I have been using 8 GB, but was looking for opinions on what would be optimum. Also, what would be the better choice for MultiPV analysis, if there is any difference (?). Is speedup the only advantage of Large Pages?

TIA

[syzygy]

Is it impossible to allocate 8GB with large pages? Maybe you first have to reboot.

[RJN]

Hi Ronald:

I have tried doing a reboot, and have never been able to get above 4GB of large pages.

Here are the results of a reboot, and then immediately running Houdini with the "lp" command. No large pages available above 4GB:

http://www.flickr.com/photos/100098593@ ... 479373824/

(Note: this machine is running Windows 7)

[kgburcham]

Hi Ronald:

I have tried doing a reboot, and have never been able to get above 4GB of large pages.

Here are the results of a reboot, and then immediately running Houdini with the "lp" command. No large pages available above 4GB:
http://www.flickr.com/photos/100098593@ ... 479373824/
(Note: this machine is running Windows 7)

Here is what mine shows when running 8192 hash with large page
What version of windows 7 are you running?

6 processor(s) found, POPCNT available
NUMA configuration with 1 node(s), offset 0
8192 MB Large Page Hash
Nalimov 6 men EGTB available - 999 MB cache
Engine: Houdini 3 Pro x64 (8192 MB)
by Robert Houdart

[RJN]

Problem solved

I have a SSD, and guess the page file was set too small. After looking at the system info, I did some experimenting on a hunch that large pages can only be a maximum of half the total virtual memory available, and that seems to be the case...or something like that. 16 GB of physical RAM with a small page file did not allow 8 GB of large pages.

Reducing the page file size made me lose the ability of 8 GB large pages, so I can make the "problem" come and go.

Thanks for the replies, and stimulating my thinking. I was making a tradeoff that turned out wasn't needed.

Great site! Learn something new every day.

[ernest]

So what page file size now allows you 8 GB of large pages?

[RJN]

4096 MB did the trick. It had been 2048 MB.

I'm not sure what others would need in a similar situation, but if you leave the value at Windows managed, it would probably be OK. I had set the page file size lower to free some SSD space, since Windows wanted to use like 25 GB on automatic! Oink.

[ernest]

since Windows wanted to use like 25 GB on automatic! Oink.