------- Comment #9 from kargl at gcc dot gnu dot org 2009-11-07 19:00 ------- Even without acml, there appears to be an issue.
gfortran44 -o one -O2 -pipe -march=native one.f90 -L/usr/local/lib \ -llapack -lblas -fopenmp ./one fred_f_1000 LAPACK Cholesky time = .27 seconds, CPU = .27 seconds LAPACK solver time = 2.48 seconds, CPU = 2.47 seconds Coded Cholesky time = .81 seconds, CPU = 1.47 seconds Coded solver time = 33.76 seconds, CPU = 38.68 seconds gfortran44 -o one -O2 -pipe -march=native one.f90 \ -L/usr/local/lib -llapack -lblas ./one fred_f_1000 LAPACK Cholesky time = .30 seconds, CPU = .30 seconds LAPACK solver time = 2.49 seconds, CPU = 2.49 seconds Coded Cholesky time = 1.36 seconds, CPU = 1.36 seconds Coded solver time = 2.97 seconds, CPU = 2.96 seconds OpenMP clearly helps the 'Coded Cholesky time', but it causes a factor of 10 degradation in the 'Coded solver time'. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41977