[LLVMdev] no differnce in the execution time between seq. and parallel programs

[Esraa]

Duncan Sands <baldrick <at> free.fr> writes:

> 
> > I would be happy if you give me an insight into what could have caused the
> > difference.
> 
> No idea.  Maybe you forgot to turn optimizations on when compiling?  Otherwise
> you are going to have to send in your programs along with an explanation of how
> you compiled them exactly (exact sequence of commands) both for gcc and LLVM.
> 
> Ciao, Duncan.
> 

Hi Ciao
Thank you very much for your help and patience

I want to check with you the compilation steps witout turn on any optimazation
in both gcc and llvm :

Fft_x.c      The first program before the transformation 
Fft_dswp.c   The second program after the transformation

In gcc compiler I used the following steps
--Before the transformation
gcc  –Wall  fft_x.c  –o  samp  -lm
Time  ./samp      
    0.544         the execution time before transformation 

--After the transformation 
Gcc –Wall   fftx_dswp.c  –o  samp  -lm  -lpthread
Time  ./samp 
0.319        the execution time after transformation 
-------------------------------------------------------       

Then I repeat the same Pervious steps with the llvm

In llvm compiler I used the following steps

--Before the transformation

Llvm-gcc   -c  -emit-llvm    fft_x.c   -o  sam.o    
Llvm-ld  sam.o  -lm
Time  ./a.out
    0.320         the execution time before transformation 

--After the transformation 
Llvm-gcc   -c  -emit-llvm    fft_dswp.c   -o  sam.o    
Llvm-ld   sam.o  -lm
Time  ./a.out
    0.350         the execution time after transformation
------------------------------------------------------

Realy I don’t care which one is faster llvm or gcc , but the thing that I care
about is 
In gcc there was difference in the execution time  before and after the
transformation, but in llvm I didn’t see any difference in llvm.
 In llvm the execution time after the transformation became worse .

if evey thing is ok and no error

My question is
Are there any strategies that llvm use it to treat with threads that make the
performance worse.

many thanks
Esraa