Swift versus C gcc fastest programs Always look at the source code. These are only the fastest programs. Do some of them use manually vectorized SIMD? Look at the other programs. They may seem more-like a fair comparison to you. fannkuch-redux source secs mem gz busy cpu load Swift 8.01 7,576 1097 31.78 100% 100% 99% 98% C gcc 7.52 836 910 29.37 99% 100% 93% 99% pidigits source secs mem gz busy cpu load Swift 0.89 8,584 600 0.89 0% 0% 0% 100% C gcc 0.73 2,848 416 0.75 1% 100% 1% 0% n-body source secs mem gz busy cpu load Swift 5.32 13,444 1326 5.39 0% 0% 100% 1% C gcc 4.02 796 1250 4.06 100% 0% 0% 1% mandelbrot source secs mem gz busy cpu load Swift 2.14 39,228 1138 8.52 99% 99% 100% 99% C gcc 1.27 31,692 1135 5.08 100% 100% 100% 99% fasta source secs mem gz busy cpu load Swift 1.43 26,128 2090 4.70 78% 78% 95% 78% C gcc 0.78 1,220 1463 0.79 1% 0% 0% 100% spectral-norm source secs mem gz busy cpu load Swift 1.43 8,168 601 5.68 99% 100% 99% 99% C gcc 0.72 1,100 569 2.86 100% 99% 100% 100% reverse-complement source secs mem gz busy cpu load Swift 1.82 785,580 1286 2.28 49% 3% 0% 74% C gcc 0.86 698,264 820 1.27 1% 18% 100% 28% k-nucleotide source secs mem gz busy cpu load Swift 13.46 256,584 1367 51.58 94% 99% 95% 96% C gcc 3.81 130,112 1506 12.18 54% 87% 79% 100% binary-trees source secs mem gz busy cpu load Swift 15.86 699,612 816 50.77 100% 79% 76% 66% C gcc 1.79 168,760 809 5.35 64% 64% 71% 100% regex-redux source secs mem gz busy cpu load Swift 23.71 1,060,560 745 49.20 35% 45% 92% 35% C gcc 0.80 152,196 1397 2.03 48% 100% 54% 53% Swift Swift version 5.4-dev (LLVM b6e6f458bb01f1f, Swift 53cfe019c0ce26d) Target: x86_64-unknown-linux-gnu C gcc gcc (Ubuntu 10.2.0-13ubuntu1) 10.2.0 all Swift programs & measurements all C gcc programs & measurements