On 19 October 2007 02:45, tim prince wrote: > skaller wrote: >> On Thu, 2007-10-18 at 06:00 -0700, Tim Prince wrote: >> >>> skaller wrote: >>> >> >> >>> I don't know of any OpenMP compiler which would correct the nesting of >>> parallel loops in your LU. I have assumed that OpenMP doesn't allow >>> such optimization; you have to get it right yourself. >>> >> >> Can you explain? This code was taken from a *tutorial* on OpenMP: >> >> http://kallipolis.com/openmp/2.html >> >> > Did they show your version somewhere as an example of what not to do? > In the page you referenced, they appear to have the correct loop nesting.
Huh? http://kallipolis.com/openmp/2.html Or, if you are really lazy, you can download LU_mp.c. 47: /* Here we update A by subtracting the appropriate values from row 48: and column. Note that these adjustments to A can be done in 49: any order */ 50: #pragma omp parallel for shared(A, row, col) 51: for (i = k+1; i<SIZE; i++) { 52: for (j = k+1; j<SIZE; j++) { 53: A[i][j] = A[i][j] - row[i] * col[j]; 54: } 55: } Now instead of a parallel http://gcc.gnu.org/ml/gcc/2007-10/msg00230.html /* Here we update A by subtracting the appropriate values from row and column. Note that these adjustments to A can be done in any order */ #pragma omp parallel for shared(A, row, col) for (i = k+1; i<SIZE; i++) { for (j = k+1; j<SIZE; j++) { A[i][j] = A[i][j] - row[i] * col[j]; } } } cheers, DaveK -- Can't think of a witty .sigline today....
