[gambit-list] Re: How to define c-lambda for this routine.

Bradley Lucier lucier at math.purdue.edu
Fri May 12 19:45:55 EDT 2006


I got the latest ooura parallel fft compiled into the bignum  
multiplication.  Supposedly it spawns 4 parallel threads for big  
enough ffts.  Note that in the test below, calculating 3^ 
{1,000,000,000} shifts back to Karatsuba multiply for really large  
numbers (> 256 million bits), so it slows down quite a bit.

Somehow it doesn't really seem worth it.  It ends up being a little  
over twice as fast on the parallel Opteron box. I think I'm going to  
look at less drastic measures to try to speed things up.

Brad

On my 2GHz G5 running 64-bit gambit, nothing else running.

Parallel fft in C (compiled with -O3):

[lindv2:~/programs/gambc40b17/gsi] lucier% ./gsi
Gambit Version 4.0 beta 17

 > (time (* 0 (expt 3 1000000)))
(time (* 0 (expt 3 1000000)))
     126 ms real time
     143 ms cpu time (119 user, 24 system)
     9 collections accounting for 11 ms real time (8 user, 4 system)
     10932368 bytes allocated
     no minor faults
     no major faults
0
 > (time (* 0 (expt 3 10000000)))
(time (* 0 (expt 3 10000000)))
     1271 ms real time
     1492 ms cpu time (1321 user, 171 system)
     10 collections accounting for 38 ms real time (9 user, 30 system)
     87918968 bytes allocated
     no minor faults
     no major faults
0
 > (time (* 0 (expt 3 100000000)))
(time (* 0 (expt 3 100000000)))
     23301 ms real time
     29528 ms cpu time (26815 user, 2713 system)
     13 collections accounting for 472 ms real time (14 user, 457  
system)
     1382017064 bytes allocated
     no minor faults
     no major faults
0
 > (time (* 0 (expt 3 1000000000)))
(time (* 0 (expt 3 1000000000)))
     379506 ms real time
     480968 ms cpu time (423657 user, 57311 system)
     24 collections accounting for 19308 ms real time (90 user, 18894  
system)
     22605836024 bytes allocated
     no minor faults
     no major faults
0

Serial fft running in scheme:

[lindv2:~/Desktop/gambc40b17/gsi] lucier% ./gsi
Gambit Version 4.0 beta 17

 > (time (* 0 (expt 3 1000000)))
(time (* 0 (expt 3 1000000)))
     176 ms real time
     176 ms cpu time (152 user, 24 system)
     9 collections accounting for 12 ms real time (8 user, 4 system)
     17846160 bytes allocated
     no minor faults
     no major faults
0
 > (time (* 0 (expt 3 10000000)))
(time (* 0 (expt 3 10000000)))
     1837 ms real time
     1834 ms cpu time (1617 user, 217 system)
     21 collections accounting for 67 ms real time (18 user, 48 system)
     143777912 bytes allocated
     no minor faults
     no major faults
0
 > (time (* 0 (expt 3 100000000)))
(time (* 0 (expt 3 100000000)))
     36836 ms real time
     36593 ms cpu time (32865 user, 3728 system)
     22 collections accounting for 881 ms real time (25 user, 853  
system)
     2276689064 bytes allocated
     no minor faults
     no major faults
0
 > (time (* 0 (expt 3 1000000000)))
(time (* 0 (expt 3 1000000000)))
     557969 ms real time
     548899 ms cpu time (485614 user, 63285 system)
     51 collections accounting for 19755 ms real time (219 user,  
19231 system)
     35132630760 bytes allocated
     no minor faults
     no major faults
0

On a 2.2(?) GHz Opteron box with 8 processors (and 8 niced-to-the-max  
folding at home jobs):

Parallel FFT in C (compiled with -O3):

euler-35% ./gsi
Gambit Version 4.0 beta 17

 > (time (* 0 (expt 3 1000000)))
(time (* 0 (expt 3 1000000)))
     126 ms real time
     99 ms cpu time (95 user, 4 system)
     9 collections accounting for 6 ms real time (6 user, 0 system)
     10932000 bytes allocated
     2643 minor faults
     no major faults
0
 > (time (* 0 (expt 3 10000000)))
(time (* 0 (expt 3 10000000)))
     1016 ms real time
     1021 ms cpu time (944 user, 77 system)
     10 collections accounting for 12 ms real time (4 user, 8 system)
     87918968 bytes allocated
     21455 minor faults
     no major faults
0
 > (time (* 0 (expt 3 100000000)))
(time (* 0 (expt 3 100000000)))
     15501 ms real time
     22549 ms cpu time (21398 user, 1151 system)
     5 collections accounting for 140 ms real time (8 user, 133 system)
     1382017064 bytes allocated
     338039 minor faults
     no major faults
0
 > (time (* 0 (expt 3 1000000000)))
(time (* 0 (expt 3 1000000000)))
     235335 ms real time
     381121 ms cpu time (361882 user, 19239 system)
     24 collections accounting for 2451 ms real time (61 user, 2378  
system)
     22605836024 bytes allocated
     5522936 minor faults
     no major faults
0

Serial FFT in Scheme:

euler-36% gsi
Gambit Version 4.0 beta 17

 > (time (* 0 (expt 3 1000000)))
(time (* 0 (expt 3 1000000)))
     154 ms real time
     154 ms cpu time (140 user, 14 system)
     11 collections accounting for 7 ms real time (5 user, 0 system)
     17843120 bytes allocated
     3105 minor faults
     no major faults
0
 > (time (* 0 (expt 3 10000000)))
(time (* 0 (expt 3 10000000)))
     1635 ms real time
     1634 ms cpu time (1522 user, 112 system)
     21 collections accounting for 22 ms real time (14 user, 9 system)
     143777912 bytes allocated
     26433 minor faults
     no major faults
0
 > (time (* 0 (expt 3 100000000)))
(time (* 0 (expt 3 100000000)))
     30350 ms real time
     30340 ms cpu time (28848 user, 1492 system)
     22 collections accounting for 142 ms real time (16 user, 124  
system)
     2276689064 bytes allocated
     418349 minor faults
     no major faults
0
 > (time (* 0 (expt 3 1000000000)))
(time (* 0 (expt 3 1000000000)))
     495749 ms real time
     494356 ms cpu time (472253 user, 22103 system)
     51 collections accounting for 2578 ms real time (42 user, 2530  
system)
     35132630760 bytes allocated
     6259491 minor faults
     no major faults
0



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