[Python-Dev] A new dict for Xmas?

[Mark Shannon]

Antoine Pitrou wrote:
> On Thu, 15 Dec 2011 22:18:18 +0000
> Mark Shannon <mark at hotpy.org> wrote:
>> For the gcbench benchmark (from unladen swallow),
>> cpython with the new dict is about 9% faster and, more importantly,
>> reduces memory use from 99 Mbytes to 61Mbytes (a 38% reduction).
>>
>> All tests were done on my ancient 32 bit intel linux  machine,
>> please try it out on your machines and let me know what sort of results 
>> you get.
> 
> Benchmark results under a Core i5, 64-bit Linux:
> 
> Report on Linux localhost.localdomain 2.6.38.8-desktop-8.mga #1 SMP Fri
> Nov 4 00:05:53 UTC 2011 x86_64 x86_64 Total CPU cores: 4
> 
> ### call_method ###
> Min: 0.292352 -> 0.274041: 1.07x faster
> Avg: 0.292978 -> 0.277124: 1.06x faster
> Significant (t=17.31)
> Stddev: 0.00053 -> 0.00351: 6.5719x larger
> 
> ### call_method_slots ###
> Min: 0.284101 -> 0.273508: 1.04x faster
> Avg: 0.285029 -> 0.274534: 1.04x faster
> Significant (t=26.86)
> Stddev: 0.00068 -> 0.00135: 1.9969x larger
> 
> ### call_simple ###
> Min: 0.225191 -> 0.222104: 1.01x faster
> Avg: 0.227443 -> 0.222776: 1.02x faster
> Significant (t=9.53)
> Stddev: 0.00181 -> 0.00056: 3.2266x smaller
> 
> ### fastpickle ###
> Min: 0.482402 -> 0.493695: 1.02x slower
> Avg: 0.486077 -> 0.496568: 1.02x slower
> Significant (t=-5.35)
> Stddev: 0.00340 -> 0.00276: 1.2335x smaller
> 
> ### fastunpickle ###
> Min: 0.394846 -> 0.433733: 1.10x slower
> Avg: 0.397362 -> 0.436318: 1.10x slower
> Significant (t=-23.73)
> Stddev: 0.00234 -> 0.00283: 1.2129x larger
> 
> ### float ###
> Min: 0.052567 -> 0.051377: 1.02x faster
> Avg: 0.053812 -> 0.052669: 1.02x faster
> Significant (t=3.72)
> Stddev: 0.00110 -> 0.00107: 1.0203x smaller
> 
> ### json_dump ###
> Min: 0.381395 -> 0.391053: 1.03x slower
> Avg: 0.381937 -> 0.393219: 1.03x slower
> Significant (t=-7.15)
> Stddev: 0.00043 -> 0.00350: 8.1447x larger
> 
> ### json_load ###
> Min: 0.347112 -> 0.369763: 1.07x slower
> Avg: 0.347490 -> 0.370317: 1.07x slower
> Significant (t=-69.64)
> Stddev: 0.00045 -> 0.00058: 1.2717x larger
> 
> ### nbody ###
> Min: 0.238068 -> 0.219208: 1.09x faster
> Avg: 0.238951 -> 0.220000: 1.09x faster
> Significant (t=36.09)
> Stddev: 0.00076 -> 0.00090: 1.1863x larger
> 
> ### nqueens ###
> Min: 0.262282 -> 0.252576: 1.04x faster
> Avg: 0.263835 -> 0.254497: 1.04x faster
> Significant (t=7.12)
> Stddev: 0.00117 -> 0.00269: 2.2914x larger
> 
> ### regex_effbot ###
> Min: 0.060298 -> 0.057791: 1.04x faster
> Avg: 0.060435 -> 0.058128: 1.04x faster
> Significant (t=17.82)
> Stddev: 0.00012 -> 0.00026: 2.1761x larger
> 
> ### richards ###
> Min: 0.148266 -> 0.143755: 1.03x faster
> Avg: 0.150677 -> 0.145003: 1.04x faster
> Significant (t=5.74)
> Stddev: 0.00200 -> 0.00094: 2.1329x smaller
> 
> ### silent_logging ###
> Min: 0.057191 -> 0.059082: 1.03x slower
> Avg: 0.057335 -> 0.059194: 1.03x slower
> Significant (t=-17.40)
> Stddev: 0.00020 -> 0.00013: 1.4948x smaller
> 
> ### unpack_sequence ###
> Min: 0.000046 -> 0.000042: 1.10x faster
> Avg: 0.000048 -> 0.000044: 1.09x faster
> Significant (t=128.98)
> Stddev: 0.00000 -> 0.00000: 1.8933x smaller

Thanks for running the benchmarks.
It's probably best not to attach to much significance to
a few percent her and there, but its good to see that performance is OK.

> 
> 
> gcbench first showed no memory consumption difference (using "ps -u").
> I then removed the "stretch tree" (which apparently reserves memory
> upfront) and I saw a ~30% memory saving as well as a 20% performance
> improvement on large sizes.

I should say how I did my memory tests.
I did a search using ulimit to limit the maximum amount of memory the 
process was allowed. The given numbers were the minimum required to 
complete, I did not remove the "stretch tree".

Cheers,
Mark.