[llvm-dev] Issues with omp simd

[Craig Topper via llvm-dev]

I didn’t look at the assembly, but you didn’t initialize your arrays. Your
program isn’t meaningful.

On Sat, Dec 30, 2017 at 9:08 AM hameeza ahmed <hahmed2305 at gmail.com> wrote:

> hello,
>
> i am trying to optimize omp simd loop as follows
>
> int main(int argc, char **argv)
> {
>     const int size = 1000000;
>
>
>     float a[size], b[size],c[size];
>
>
>
>         #pragma omp simd
>         for (int i=0; i<size; ++i)
>         {
>             c[i]= a[i] + b[i];
>         }
>
>
>     return 0;
> }
>
> i run it using the following command;
>
> g++ -O0 --std=c++14 -fopenmp-simd lab.cpp  -Iinclude -S -o lab.s
>
> when i compared it with code as follows without simd
>
>
> int main(int argc, char **argv)
> {
>     const int size = 1000000;
>
>
>     float a[size], b[size],c[size];
>
>
>
>         for (int i=0; i<size; ++i)
>         {
>             c[i]= a[i] + b[i];
>         }
>
>
>     return 0;
> }
>
> using following command
>
> g++ -O0 --std=c++14  lab.cpp -Iinclude -S -o lab.s
>
> I am getting the same assembly. Why is that so? why not omp simd is more
> efficient?
>
> Please help
>
>
> --
~Craig
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