Loop unrolling

[kt_mic]

I have some problems getting loop unrolling to function.
Using for example the options for a simple dot product routine

-QxW -Qunrolln

the compiler always appears to unroll 4 times (actually 8 since
double values are loaded) regardless of n, except in the case n=0 which does not unroll.

Without SSE specification, i.e.

-O3 -Qunroll

nothing apparently happens! -Qunroll0 and -Qunroll4 gives identical code.

I am using the latest version of the compiler, and I have tried many 'unroll'-variants with and without : (the documentation is not quite consistent)

Michael

[Steven_L_Intel1]

In the current version of the IA-32 compiler, you need to use one of the Qx switches to get loop unrolling in conjunction with -O3. My understanding is that this will no longer be required in a future version.