C gcc versus C clang fastest programs Always look at the source code. These are only the fastest programs. Look at the other programs. They may seem more-like a fair comparison to you. mandelbrot source secs mem gz busy cpu load C gcc 1.64 27,024 1135 6.53 99% 99% 100% 100% C clang 4.70 29,036 694 18.80 100% 100% 100% 100% k-nucleotide source secs mem gz busy cpu load C gcc 4.84 130,192 1506 16.00 98% 83% 63% 87% C clang 9.49 128,920 1506 20.32 51% 44% 59% 60% fannkuch-redux source secs mem gz busy cpu load C gcc 8.73 696 910 34.46 100% 95% 100% 100% C clang 13.88 772 1557 54.43 95% 100% 99% 98% binary-trees source secs mem gz busy cpu load C gcc 3.59 168,896 809 11.86 77% 74% 98% 82% C clang 4.81 117,408 836 14.25 63% 63% 92% 78% reverse-complement source secs mem gz busy cpu load C gcc 1.92 551,900 820 2.58 20% 99% 14% 1% C clang 2.19 994,284 750 3.28 14% 21% 40% 75% spectral-norm source secs mem gz busy cpu load C gcc 1.98 988 569 7.89 99% 99% 100% 99% C clang 2.08 3,212 569 8.27 100% 100% 100% 100% pidigits source secs mem gz busy cpu load C gcc 1.75 2,608 452 1.80 67% 0% 2% 33% C clang 1.75 2,616 452 1.88 5% 100% 1% 2% regex-redux source secs mem gz busy cpu load C gcc 1.42 152,192 1397 3.40 100% 48% 48% 44% C clang 1.41 154,436 1397 4.32 96% 69% 73% 70% fasta source secs mem gz busy cpu load C gcc 1.46 2,948 2268 5.84 100% 99% 100% 99% C clang 1.44 3,948 2268 5.74 99% 100% 99% 99% n-body source secs mem gz busy cpu load C gcc 7.30 8 1391 7.41 0% 1% 100% 0% C clang 6.11 8 1391 6.17 54% 1% 0% 47% C gcc gcc (Ubuntu 9.3.0-10ubuntu2) 9.3.0 C clang clang version 10.0.0-4ubuntu1 all C gcc programs & measurements all C clang programs & measurements