On T, 2005-05-17 at 22:37 -0400, Tom Lane wrote: > Bruce Momjian <pgman@candle.pha.pa.us> writes: > > I don't understand why we are testing 64-bit CRC when I thought we > > agreed that 32-bit was good enough for our purposes. > > Well, we need to understand exactly what is going on here. I'd not > like to think that we dropped back from 64 to 32 bit because of one > possibly-minor optimization bug in one compiler on one platform. > Even if that compiler+platform is 90% of the market.
There are cases where 32bit is about 20% slower. I tried to send the folowing yesterday, but for some reason the mails I send from home where To: is Tom Lane get errors from "RCPT:[EMAIL PROTECTED] " and fail to go through to other destinations (like pgsql-hackers) after that :( ----- crc32 compiled as 32bit executable is 10% slower than crc64 as eithet 32 or 64 bit exe, but if you compile your backend as 64bit then the difference is almost 20%. crc64 is the same speed compiled either way. gcc version 3.4.3 20041212 (Red Hat 3.4.3-9.EL4) on OpenPower5 1.8GHz file ./crctest ./crctest: ELF 32-bit MSB executable, PowerPC or cisco 4500, version 1 (SYSV) cc -O1 crctest.c -o crctest -- time 0.584327 s cc -O2 crctest.c -o crctest -- time 0.594664 s cc -O3 crctest.c -o crctest -- time 0.594764 s file ./crctest ./crctest: ELF 64-bit MSB executable, cisco 7500, version 1 (SYSV) cc -O1 -m64 crctest.c -o crctest -- time 0.644473 s cc -O2 -m64 crctest.c -o crctest -- time 0.648033 s cc -O3 -m64 crctest.c -o crctest -- time 0.688682 s file ./crctest64 ./crctest64: ELF 64-bit MSB executable, cisco 7500, version 1 (SYSV) cc -O1 -m64 crctest64.c -o crctest64 -- time 0.545026 s cc -O2 -m64 crctest64.c -o crctest64 -- time 0.545470 s cc -O3 -m64 crctest64.c -o crctest64 -- time 0.545037 s file ./crctest64 ./crctest64: ELF 32-bit MSB executable, PowerPC or cisco 4500, version 1 (SYSV) cc -O1 crctest64.c -o crctest64 -- time 0.545364 s cc -O2 crctest64.c -o crctest64 -- time 0.644093 s cc -O3 crctest64.c -o crctest64 -- time 0.644155 s [EMAIL PROTECTED] -- Hannu Krosing <[EMAIL PROTECTED]> ---------------------------(end of broadcast)--------------------------- TIP 3: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly