speed of unbalanced multiplication
bodrato at mail.dm.unipi.it
bodrato at mail.dm.unipi.it
Sat Jan 26 16:01:53 CET 2013
Ciao Paul,
Il Ven, 25 Gennaio 2013 9:24 pm, Zimmermann Paul ha scritto:
> in GMP 5.1.0, a multiplication of n x m limbs for m < n can be slower than
> a multiplication of n x n limbs. Compare for example the line starting
> mpn_mul.1000000 mpn_mul.1000000
> 775660 #0.740046000 0.744046000
> mpn_mul_n mpn_mul_n
> 1000000 0.736046000 #0.728045000
Is the problem due to the unbalanced size of operands, or it depends on
the fact that FFT is poorly tuned for very big sizes?
I mean, which timing do you obtain with the following?
./speed -s $((1000000+775660)/2) mpn_mul_n mpn_mul_n
Regards,
m
--
http://bodrato.it/papers/combinatorics.html
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