Classic Fortran versus Intel Fortran fastest performance Always look at the source code. If the fastest programs are hand-written vector instructions, does the host language matter? You might be more interested in the less optimised programs — more seconds, less gz source code. fannkuch-redux source secs mem gz cpu secs Intel Fortran #3 9.58 19,856 1164 38.22 Classic Fortran 38.73 19,724 608 38.73 Classic Fortran #3 10.14 19,724 1164 40.45 Intel Fortran 41.03 19,724 608 41.02 n-body source secs mem gz cpu secs Intel Fortran #5 3.42 19,728 1669 3.41 Classic Fortran #6 4.21 19,856 1530 4.21 Intel Fortran #6 4.26 19,728 1530 4.26 Intel Fortran #2 4.40 19,728 1507 4.40 Intel Fortran #3 4.42 19,728 1311 4.41 Intel Fortran 4.53 19,728 1400 4.53 Classic Fortran #2 5.37 19,856 1507 5.37 Classic Fortran 5.43 19,728 1400 5.43 Classic Fortran #5 5.98 19,728 1669 5.98 Classic Fortran #4 6.18 19,728 1183 6.18 Classic Fortran #3 6.32 19,856 1311 6.32 Intel Fortran #4 Bad Output spectral-norm source secs mem gz cpu secs Intel Fortran #2 2.66 19,736 520 2.66 Classic Fortran #2 2.66 19,736 520 2.66 Classic Fortran #3 0.72 19,736 644 2.87 Intel Fortran #3 0.73 19,736 644 2.88 mandelbrot source secs mem gz cpu secs Classic Fortran #8 1.42 75,392 965 5.59 Intel Fortran #6 2.81 76,288 669 8.96 Classic Fortran #6 3.27 75,904 669 10.86 Intel Fortran #8 4.06 75,904 965 16.12 Intel Fortran #4 9.79 76,416 626 25.24 Classic Fortran #4 10.27 75,904 626 26.58 Intel Fortran #5 32.52 43,904 528 32.52 Classic Fortran #5 45.21 43,648 528 45.21 pidigits source secs mem gz cpu secs Intel Fortran #4 0.87 19,856 987 0.87 Classic Fortran #4 0.87 19,728 987 0.87 regex-redux source secs mem gz cpu secs Classic Fortran 0.93 176,236 2229 3.04 Intel Fortran 0.95 176,564 2229 3.08 fasta source secs mem gz cpu secs Intel Fortran #4 1.30 19,728 1355 1.30 Classic Fortran #4 2.05 19,728 1355 2.05 Intel Fortran 5.76 19,728 1193 5.76 Intel Fortran #3 6.34 19,728 1217 6.34 Classic Fortran #3 6.55 19,728 1217 6.55 Classic Fortran 6.85 19,728 1193 6.85 k-nucleotide source secs mem gz cpu secs Classic Fortran Make Error Intel Fortran Make Error reverse-complement source secs mem gz cpu secs Intel Fortran 3.32 986,304 1026 3.32 Classic Fortran 4.15 986,304 1026 4.14 Classic Fortran #2 41.23 769,748 778 41.23 Intel Fortran #2 44.96 769,748 778 44.95 binary-trees source secs mem gz cpu secs Intel Fortran #2 2.13 136,576 1155 6.55 Classic Fortran #2 2.26 136,704 1155 6.87 Classic Fortran 31.48 525,824 780 31.48 Intel Fortran 31.50 525,824 780 31.50 Classic Fortran Fortran Compiler Classic 2021.11.1 20231117 Intel Fortran ifx (IFX) 2024.0.2 20231213 all Classic Fortran programs & measurements all Intel Fortran programs & measurements