https://community.intel.com/t5/Intel-Fortran-Compiler/Loop-unrolling/m-p/845437#M63406 I have some problems getting loop unrolling to function.<BR />Using for example the options for a simple dot product routine<BR /><BR />-QxW -Qunrolln<BR /><BR />the compiler always appears to unroll 4 times (actually 8 since<BR />double values are loaded) regardless of n, except in the case n=0 which does not unroll.<BR /><BR />Without SSE specification, i.e.<BR /><BR />-O3 -Qunroll<BR /><BR />nothing apparently happens! -Qunroll0 and -Qunroll4 gives identical code.<BR /><BR />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)<BR /><BR />Michael Mon, 23 Jan 2006 22:02:06 GMT kt_mic 2006-01-23T22:02:06Z https://community.intel.com/t5/Intel-Fortran-Compiler/Loop-unrolling/m-p/845437#M63406 I have some problems getting loop unrolling to function.<BR />Using for example the options for a simple dot product routine<BR /><BR />-QxW -Qunrolln<BR /><BR />the compiler always appears to unroll 4 times (actually 8 since<BR />double values are loaded) regardless of n, except in the case n=0 which does not unroll.<BR /><BR />Without SSE specification, i.e.<BR /><BR />-O3 -Qunroll<BR /><BR />nothing apparently happens! -Qunroll0 and -Qunroll4 gives identical code.<BR /><BR />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)<BR /><BR />Michael Mon, 23 Jan 2006 22:02:06 GMT https://community.intel.com/t5/Intel-Fortran-Compiler/Loop-unrolling/m-p/845437#M63406 kt_mic 2006-01-23T22:02:06Z https://community.intel.com/t5/Intel-Fortran-Compiler/Loop-unrolling/m-p/845438#M63407 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. Mon, 23 Jan 2006 22:39:02 GMT https://community.intel.com/t5/Intel-Fortran-Compiler/Loop-unrolling/m-p/845438#M63407 Steven_L_Intel1 2006-01-23T22:39:02Z