------- Comment #7 from burnus at gcc dot gnu dot org 2010-06-21 15:02 ------- (In reply to comment #1) > Just for reference, the difference in time between the two variants is truly > impressive. About a factor of 11 with gcc 4.4 and 8 with gcc 4.5.
I get for the example the following values, note especially the newly added CONTIGUOUS result: 0.31601900 - assumed-shape 0.21601403 - assumed-shape CONTIGUOUS 0.21601295 - explicit size (n,n,...) 0.20801300 - explicit size (10,10,...) 0.21601403 - explicit size (10*10*...) Ignoring some measuring noise, assumed-shape is 46% (-O0) to 25% (-O3) slower than explicit size, but using the CONTIGUOUS attribute, the performance is re-gained. I cannot reproduce the factor of 10 results, however. What surprises me a bit is that -flto -fwhole-program does not reduce the speed penalty of assumed-shape arrays. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41137