On Thu, Feb 05, 2009 at 11:39:09AM -0600, Ross Bates wrote:
Hi All - can someone help me clarify the difference between Algebra "-G" mode and setting SQL debug equal to 16384 in the monetdb config file? With an older version of MonetDb I set the sql_debug=16384 in the config file so I could take advantage of Algebra mode when starting the server via mero. Today I compiled the Nov08-SP2 release and ran some tests using sql_debug=0 vs sql_debug=16384. I assumed they would do the exact same since Algebra mode is now the default. They returned very different results however. For SQL statements with a large number of predicates (100+), performance is about the same. But for anything smaller the query speed is much worse (10x avg) when I don't have sql_debug=16384 turned on. The Algebra because default in the current stable (and the development up to it). So the Nov08 doesn't have this by default. So I don't think its strang that the 16384 setting (ie enabling algebra) works better. Anyway if your in a testing phase, please consider the current cvs stable branch. It could improve the release later this month.
Niels
The query trace files are also different when I run the exact same query with and without the 16384 flag. I made sure to restart the server process in between. Also, below is the latest output from mserver --version: Copyright (c) 1993-July 2008 CWI Copyright (c) August 2008- MonetDB B.V., all rights reserved Visit [1]http://monetdb.cwi.nl/ for further information Configured for prefix: /home/ross/monetNov08sp2 Libraries: openssl: OpenSSL 0.9.8g 19 Oct 2007 (compiled with OpenSSL 0.9.8g 19 Oct 2007) Compiled by: ross@home Compilation: gcc -O2 -std=c99 -fgnu89-inline -O6 -fomit-frame-pointer
-finline-functions -falign-loops=4 -falign-jumps=4 -falign-functions=4 -fexpensive-optimizations -funroll-loops -frerun-cse-after-loop -frerun-loop-opt -ftree-vectorize Linking : /usr/bin/ld Any thoughts? Best Regards, Ross
References
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-- Niels Nes, Centre for Mathematics and Computer Science (CWI) Science Park 123, 1098 XG Amsterdam, The Netherlands room C0.02, phone ++31 20 592-4098, fax ++31 20 592-4312 url: http://www.cwi.nl/~niels e-mail: Niels.Nes@cwi.nl