Re: OpenMP + ACLiC

From: Philippe Canal <pcanal_at_fnal.gov>
Date: Wed, 15 Sep 2010 10:53:40 -0500


 Hi,

You need to at least hide the #pragma from CINT:

#ifndef __CINT__
#pragma omp parallel private(top, bottom)
#endif

 {
#ifndef __CINT__
#pragma omp for reduction(+:sum)
#endif

 for(Int_t i = 0; i < kN; i++) {

Cheers,
Philippe.

On 9/15/10 10:47 AM, OKUMURA, Akira wrote:
> Hello ROOTers,
>
> Does ACLiC support OpenMP?
>
> I started learning OpenMP to improve the speed of my analysis. The following is an example to calculate pi with OpenMP.
>
> === pi.C ===
> #include <omp.h>
> #include <time.h>
> #include <iostream>
>
> void pi()
> {
> const Int_t kN = 100000000;
> long double top = 0.L;
> long double bottom = 0.L;
> long double kStep = 1.L/kN;
> long double sum = 0.L;
>
> #pragma omp parallel private(top, bottom)
> {
> #pragma omp for reduction(+:sum)
> for(Int_t i = 0; i < kN; i++) {
> top = 4.L/(1.L + (kStep*i)*(kStep*i));
> bottom = 4.L/(1.L + (kStep*(i+1))*(kStep*(i + 1)));
> sum += (top + bottom)*kStep/2.L;
> } // i
> }
> std::cout.precision(16);
> std::cout << "pi = " << sum << "\n";
> }
> ============
>
> But I got the following error.
> ============
> root [0] gSystem->SetIncludePath("-fopenmp")
> root [1] gSystem->AddLinkedLibs("-lgomp")
> root [2] .L pi.C+O
> Info in <TUnixSystem::ACLiC>: creating shared library /Users/oxon/./pi_C.so
> In file included from /Users/oxon/pi_C_ACLiC_dict.h:34,
> from /Users/oxon/pi_C_ACLiC_dict.cxx:16:
> /Users/oxon/./pi.C: In function ‘void pi()’:
> /Users/oxon/./pi.C:13: error: expected ‘#pragma omp’ clause before ‘public’
> i686-apple-darwin10-g++-4.2.1: /Users/oxon/pi_C_ACLiC_dict.o: No such file or directory
> Error in <ACLiC>: Compilation failed!
> ============
>
> It seems that some of OpenMP words are not handled properly in generation of a dictionary. I suppose ACLiC does not support OpenMP yet.
>
> If ACLiC supports OpenMP, how can I run the script in ROOT? This example runs as I expected in standalone C++ program.
>
> I am using ROOT trunk and GCC (i686-apple-darwin10-g++-4.2.1 (GCC) 4.2.1 (Apple Inc. build 5664)) on Snow Leopard.
>
> Regards,
>
> --
> OKUMURA, Akira oxon@{astro.isas.jaxa.jp,stanford.edu}
> Institute of Space and Astronautical Science (ISAS/JAXA)
> Now at KIPAC/SLAC/Stanford
> Varian Physics #306
> 382 Via Pueblo Mall, MC 406 Stanford, CA94305
> TEL 650-736-0971/FAX 650-724-5065
> Skype : okumura.akira
>
Received on Wed Sep 15 2010 - 17:53:46 CEST

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