Marco,
> Date: Wed, 6 Feb 2013 17:59:44 +0100 (CET)
> From: bodr...@mail.dm.unipi.it
>
> Ciao Paul!
Ciao!!!
> Of course. With current implementation, unbalanced multiplications need
> some more memory and a few additions/subtractions, but this should not
> give a measurable slow-down. The "matrix" obtained with
>
> $ tune/speed -s 400000-800000 -t 100000 mpn_mul.800000 mpn_mul.900000
> mpn_mul.1000000 mpn_mul.1100000 mpn_mul.1200000
>
> shows that times are not as monotonic as desired, but "unbalancement" does
> not really have an influence.
indeed:
frite% ./speed -s 400000-800000 -t 100000 mpn_mul.800000 mpn_mul.900000
mpn_mul.1000000 mpn_mul.1100000 mpn_mul.1200000
overhead 0.000000002 secs, precision 10000 units of 3.33e-10 secs, CPU freq
3000.00 MHz
mpn_mul.800000 mpn_mul.900000 mpn_mul.1000000 mpn_mul.1100000
mpn_mul.1200000
400000 #0.460029000 0.472029000 0.564035000 0.572035000 0.712044000
500000 #0.476029000 0.560035000 0.548034000 0.692043000 0.708044000
600000 #0.572036000 0.576036000 0.704044000 0.680042000 0.696044000
700000 #0.556035000 0.688043000 0.672042000 0.676042000 0.724046000
800000 0.712045000 0.700044000 #0.668042000 0.688043000 0.772048000
> I think that the culprit is the tune/speed program, but I'm not able to
> correct it. I just tested the attached patch. After patching, the results
> are:
>
> $ tune/speed -s 800000-1000000 -t 100000 mpn_mul_n mpn_mul mpn_mul_bal
> overhead 0.000000000 secs, precision 10000 units of 3.13e-11 secs, CPU
> freq 31990.26 MHz
> mpn_mul_n mpn_mul mpn_mul_bal
> 800000 0.646571000 0.682834000 #0.632961000
> 900000 #0.652178000 0.678564000 0.655979000
> 1000000 0.710674000 0.740998000 #0.702508000
I can reproduce this on GMP 5.1.0 with your patch:
frite% ./speed -s 800000-1000000 -t 100000 mpn_mul_n mpn_mul mpn_mul_bal
overhead 0.000000002 secs, precision 10000 units of 3.33e-10 secs, CPU freq
3000.00 MHz
mpn_mul_n mpn_mul mpn_mul_bal
800000 0.668041000 0.716045000 #0.664041000
900000 #0.652040000 0.696043000 0.656041000
1000000 0.724045000 0.748046000 #0.720045000
> As you can see mpn_mul_n and mpn_mul_bal are comparable, and mpn_mul is
> always slower. All the three functions measure the time to multiply two
> numbers of the same size. mpn_mul_bal and mpn_mul measure the same
> function, but the first uses the same macro that tune/speed uses for
> mpn_mul_n...
if the culprit is the macro used in speed, it should be fixed!
Paul
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