[macstl-dev] not all rosey in the gcc-4.0.0 land

[Glen Low]

On 02/07/2005, at 12:32 PM, Ilya Lipovsky wrote:

>>
>> That is strange indeed. On Apple gcc 4.0 (as of Xcode 2.1), the  
>> following:
>>
>>        using namespace stdext;
>>        valarray <float> v1 (10.f, 100);
>>        valarray <float> v2 (20.f, 100);
>>        std::cout << (v1 * v2).sum ();
>>
>> produces 20000 as expected. Do you not get this result with Yellow  
>> Dog Linux?
>>
>> You may have to check carefully where the problem occurs in YDL,  
>> since this is explicitly one of the expressions optimized to use  
>> vmaddfp through valarray_altivec.h:154.
>>
>>
>
> Could you please try that with valarray<stdext::complex <float> > ?  
> Because this is where my code fails.
>
> -Ilya

Sure thing.

         using namespace stdext;
         valarray <complex <float> > v1 (complex <float> (1.0f,2.0f),  
100);
         valarray <complex <float> > v2 (complex <float> (3.0f,4.0f),  
100);
         std::cout << (v1 * v2).sum ();

produces

(-500,1000)
benchmark has exited with status 0.

on my Mac as expected.

Perhaps the error is with particular values of v1, v2 etc.? (BTW, the  
complex multiply then sum is also optimized to use some combination  
of vectorized fma, from recollection, so any error would start at  
valarray_altivec.h:154 -- test that is involved by inserting a  
std::cout << "x" in the static "call" function.) You can do a random  
search of the problem space by looking at exhaustive.cpp and  
configuring it with the right functor template, stdext::accumulator  
<stdext::plus>.

Cheers, Glen Low


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