On 11/24/16 14:11, Vsevolod Stakhov wrote:
On 24/11/2016 13:05, Hans Petter Selasky wrote:
On 11/24/16 13:13, Vsevolod Stakhov wrote:
On 23/11/2016 16:27, Ed Schouten wrote:
Hi Hans,
2016-11-23 15:27 GMT+01:00 Hans Petter Selasky <h...@selasky.org>:
I've made a patch to hopefully optimise SAT solving in our pkg utility.
Nice! Do you by any chance have any numbers that show the performance
improvements made by this change? Assuming that the SAT solver of
pkg(1) uses an algorithm similar to DPLL[1], a change like this would
affect performance linearly. My guess is therefore that the running
time is reduced by approximately 5/12. Is this correct?
There won't be any improvement if you just remove duplicates from SAT
formula. This situation is handled by picosat internally and even for
naive DPLL there is no significant influence of duplicate KNF clauses:
once you've assumed all vars in some clause, you automatically resolve
all duplicates.
Is there any real improvement of SAT solver speed with this patch? From
my experiences, SAT solving is negligible in terms of CPU time comparing
to other tasks performed by pkg.
Hi,
I added some code to measure the time for SAT solving. During my test
run I'm seeing values in the range 8-10ms for both versions, so I
consider that neglible. However, the unpatched version wants to
reinstall 185 packages while the non-patched version wants to reinstall
1 package. That has a huge time influential. I'm not that familar with
PKG that I can draw any conclusions from this.
# Test1:
echo "n" | /xxx/pkg/src/pkg-static upgrade --no-repo-update > b.txt
# Test2:
echo "n" | env PKG_NO_SORT=YES /xxx/pkg/src/pkg-static upgrade
--no-repo-update > a.txt
Then I don't understand how your patch should affect the solving
procedure. If pkg tries to reinstall something without *reason* it is a
good sign of bug in pkg itself and/or your database/repo and not in SAT
solver.
I'll try to review your issue but I'll likely need your local packages
database for this test.
Hi,
Maybe it is a bug somewhere.
I noticed some rules repeating the same variable two times for example.
Send me the list of files you need off-list.
Thank you!
--HPS
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