Hello! Here are some effects of newly introduced -mpcX flag on a povray-3.6.1 (as kind of representative FP-heavy application to measure FP performance).
The code was compiled using: -O3 -march=native -funroll-all-loops -ffast-math -D__NO_MATH_INLINES -malign-double -minline-all-stringops (32bit code) and final binary was linked using -mpc32, -mpc64 or -mpc80. The testfile was abyss.pov in default resolution (320 x 240) and the timings were performed on 'Intel(R) Xeon(TM) CPU 3.60GHz'. Following are averages of 5 runs: -mpc80: average runtime 13.273s (baseline) -mpc64: average runtime 12.977s (2.2 % faster than baseline) -mpc32: average runtime 12.160s (9.2 % faster than baseline) It should be noted, that rendered picture in -mpc32 case developed a strange halo around rendered object (nice special effect ;), and this is clearly the effect of too low FP precision. -mpc64 and -mpc80 rendered pictures were equal, as far as my vision in concerned (well, not quite a scientific approach). It should be noted, that ifort defaults to -pc64 and this brings some 2% better runtimes on FP intensive code. Uros.
