On 20130306@12:08, Tim Prince wrote: > > > . CFLAGS for gcc: > >"-O3 -pipe -march=native -mtune=native -mavx -std=c99 -fno-unroll-loops" > > . CFLAGS for icc: "-O3 -xAVX -restrict -unroll=0" > > ... > >Do you find this consistent with your experience in "complex" and gcc, > >or it may be the case I am ignoring some basic rule in using gcc ? > > > In the absence of -fcx-limited-range, gcc may protect divide and > sqrt by using library functions, where icc would simply widen to > double. You would see any such library function usage if you > profiled by gprof, at least when the library is static linked. Also, > the library functions used by gcc aren't vectorized, while icc would > go further toward promoting vectorization by in-lining code or > calling vector math functions. In man gcc I see that -fcx-limited-range affects both multiplication and division, while -fcx-fortran-rules only division. The functions in my code only contain integer/floating point array accesses and add / multiply operations. So only multiplications may be accelerated by this or -ffast-math. And as you suggest, man icc says -no-complex-limited-range is the default, so icc -O3 would need at least -complex-limited-range to be fairly compared to gcc -ffast-math . > Vectorization reports for both compilers would shed light on this question. Ok: Could you please suggest the options for getting "enough, but not too many" report info ?
