[Python-Dev] String hash function multiplier (original) (raw)

Andrew MacIntyre andymac at bullseye.apana.org.au
Wed Apr 14 09:34:13 EDT 2004

On Wed, 14 Apr 2004, Jeff Epler wrote:

Pentium IV, 2.4GHz: -O2 -mcpu=i386 -DMUL=100003 1.56

{...}

-O2 -mcpu=pentium4 -DMUL=100003 0.63

{...}

With AMD CPUs, the current multiplier beats both the new multipler and the version expressed as shifts and adds/subtracts:

{...}

On an Athlon XP 2600+: -O2 -mcpu=i386 -DMUL=100003 0.95

{...}

-O2 -mcpu=athlon-xp -DMUL=100003 0.43 *

{...}

Long-at-a-time hash, Duron, 1GHz: -O2 -march=athlon-tbird -DMUL=100003 0.35

Ummm... are you showing what you think you're showing here? As I recall, i386 gcc uses -mcpu and -march differently to most other architectures:

So most of the timings you show are for the i386 instruction set, but with different scheduling. The exception is the long-at-a-time hash.

-- Andrew I MacIntyre "These thoughts are mine alone..." E-mail: andymac at bullseye.apana.org.au (pref) | Snail: PO Box 370 andymac at pcug.org.au (alt) | Belconnen ACT 2616 Web: http://www.andymac.org/ | Australia