gfortran -O2 -ftree-vectorize -ftree-vectorizer-verbose=2 -c -v s112.f The case could be vectorized by taking the array elements in reverse order (as specified in the source). ifort vectorizes by creating a temporary array (when the reversal is removed from the source), losing performance.
-- Summary: can't determine dependence (loop reversal required) Product: gcc Version: 4.3.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: fortran AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: tprince at computer dot org GCC build triplet: x86_64-unknown-linux-gnu GCC host triplet: x86_64-unknown-linux-gnu GCC target triplet: x86_64-unknown-linux-gnu http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32379