random variate from power exponential distribution: performances

[Claudio Attaccalite]

For better optimization options have a look
of this page

http://home.comcast.net/~jcunningham63/linux/GCC_Optimization.html

Claudio


Giulio Bottazzi ha scritto:

>On Mon, 27 Sep 2004 11:00:08 -0500
>Linas Vepstas <linas@austin.ibm.com> wrote:
>
>  
>
>>You should test again with optimization turned on. This can make 
>>a *huge* difference in relative performance.   Without optimization,
>>the compiler does literally what the C code says, with an excess use
>>of register-to-register copies.  Thus, and sort of redundant
>>    
>>
>
>Hi Linas,
>very good point!  What you suggest is longer to say than to do
>
>gcc -O3 -march=i686 -lgsl -lgslcblas testran.c -o testran
>
>results (ignore the value for a, it doesn't matter) :
>
>value for a    value for b   JOHNSON (secs)  TADIKAMALLA (secs)    
>
>1.000000	0.500000	0.540000	3.630000
>1.000000	0.600000	1.590000	2.880000
>1.000000	0.700000	1.550000	2.500000
>1.000000	0.800000	1.490000	2.290000
>1.000000	0.900000	1.430000	2.170000
>1.000000	1.000000	0.510000	0.220000
>1.000000	1.100000	1.330000	2.160000
>1.000000	1.200000	1.330000	2.180000
>1.000000	1.300000	1.330000	2.160000
>1.000000	1.400000	1.320000	2.180000
>1.000000	1.500000	1.310000	2.180000
>1.000000	1.600000	1.320000	2.170000
>1.000000	1.700000	1.300000	2.170000
>1.000000	1.800000	1.290000	2.180000
>1.000000	1.900000	1.290000	2.180000
>1.000000	2.000000	1.290000	0.410000
>1.000000	2.100000	1.280000	4.370000
>1.000000	2.200000	1.270000	4.370000
>1.000000	2.300000	1.270000	4.360000
>1.000000	2.400000	1.260000	4.370000
>1.000000	2.500000	1.260000	4.370000
>1.000000	2.600000	1.250000	4.370000
>1.000000	2.700000	1.250000	4.380000
>1.000000	2.800000	1.250000	4.380000
>1.000000	2.900000	1.250000	4.380000
>1.000000	3.000000	1.230000	3.920000
>1.000000	3.200000	1.230000	4.390000
>1.000000	3.400000	1.230000	4.370000
>1.000000	3.600000	1.220000	4.370000
>1.000000	3.800000	1.210000	4.370000
>1.000000	4.000000	1.210000	3.960000
>
>
>comment: things did not change, JOHNSON is ALWAYS faster.
>
>
>BTW I've tested also on a dual opteron compiling with
>
>gcc -O3 -lgsl -lgslcblas testran.c -o testran
>
>guess what? same thing: JOHNSON is ALWAYS faster.
>
>
>Any other optimization option to suggest?
>
>
>	G.
>
>
>
>
>  
>


-- 
==========================================================
Claudio Attaccalite
PhD student in Condensed Matter Theory
S.I.S.S.A.
Via Beirut 2-4 34014 Grignano (TS)
email: attacc@sissa.it
ICQ number: 23970278
web site: http://www.freescience.info/claudio/
=========================================================== 

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