directive for loop blocking?

[woshiwuxin]

Hi, everyone!

I'm looking for a directive that can tell the compiler to perform "loop blocking" automatically. With -O3 option, the compiler is able to block some simple loops, e.g. the triple loop in a matrix matrix multiplication. However, the compiler may be "puzzled" by more complicated loop structures (DO loop only). Is there any directives can help the compiler to block the loops (DO-loop is enough for my work)?

Thank you in advance!

[jimdempseyatthecove]

Can you provide an example and describe the problem in additional detail. Jim Dempsey

[woshiwuxin]

for example, a simple matrix matrix multiplication is do j=1, n do k=1, n do i=1, n c(i,j) = c(i,j) + a(i,k)*b(k,j) enddo enddo enddo ifort -O3 can do loop blocking automatically. But, "ifort -O3" fails to block the loops for the follow code. do j=1, n do k=1, n temp=b(k,j) ! temp in register do i=1, n c(i,j) = c(i,j) + a(i,k)*t enddo enddo enddo

[TimP]

This example raises the possibility that you mean introduction of an undefined variable suppresses optimization. That should not be surprising. If you mean you're interested in the directives !dir$ unroll_and_jam or !dir$ simd private, please refer to the ifort documentation, then present a clearer example of your intent.