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Subject: Re: [Boost-users] Xcode - Slow
From: Raphaël Amiot (raphael.amiot_at_[hidden])
Date: 2010-06-30 13:12:15


Code here. You'll need to change the path to boost headers in the includes to make it run.

Part that runs way too slow:

chrono.begin();
        for(int i=0; i<nombremult; i++)
        res = prod(m,n);
        
                if(chrono.elapsed()<1000)
                        fileoutput << chrono.elapsed() << " " << chrono.elapsed_micro() << " ";
                else
                        fileoutput << chrono.elapsed() << " " << 0 << " ";
                
        }

This goes far faster on visual than on xcode.

Le 30 juin 2010 à 18:09, Christopher Jefferson a écrit :

>
> On 30 Jun 2010, at 16:55, Raphaël Amiot wrote:
>
>> Hello there.
>>
>> I am implementing matrix multiplication and am trying to have my stuff run as fast as possible.
>> But then I noticed something strange.
>> Using Xcode,
>>
>> resultmatrix = prod(matrix1,matrix2);
>>
>> is 10 to 16 times slower (with 100x100 matrixes) than simply doing something like that:
>>
>>
>> for(...)
>> for(...)
>> for(..)
>> multiply_things();
>>
>> And 20 to 40 times slower than a simple threaded approach.
>>
>>
>> Using visual studio, it's 2 times faster than naive multiplication.
>>
>>
>> This is on a release build, with
>> #define BOOST_UBLAS_NDEBUG 1
>> #define NDEBUG 1
>>
>> So what gives?_______________________________________________
>
> Could you provide a small complete program which shows your problem?
>
> Chris
>
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