These benchmarks are informal and only intended to give us a general sense of the benefit Dart Sass could provide relative to other implementations. This was tested against: * libsass ac338dfd and sassc a873899 compiled with g++ (Debian 7.3.0-18) 7.3.0. * Dart Sass 143e02a on Dart 2.4.0 and Node v12.0.0. on Debian x64 with Intel Xeon E5-1650 v3 @ 3.50GHz. The Dart Sass [application snapshot][] was trained on the `tool/app-snapshot-input.scss` file. [application snapshot]: https://github.com/dart-lang/sdk/wiki/Snapshots # Measurements I ran five instances of each configuration and recorded the fastest time. ## Small Plain CSS Running on a file containing 4 instances of `.foo {a: b}`: * sassc: 0.005s * Dart Sass from a script snapshot: 0.219s * Dart Sass native executable: 0.019s * Dart Sass on Node.js: 0.195s Based on these numbers, Dart Sass from a native executable is approximately: * 3.8x slower than libsass * 10.3x faster than Dart Sass on Node ## Large Plain CSS Running on a file containing 2^17 instances of `.foo {a: b}`: * sassc: 1.735s * Dart Sass from a script snapshot: 1.573s * Dart Sass native executable: 1.460s * Dart Sass on Node.js: 2.729s Based on these numbers, Dart Sass from a native executable is approximately: * 1.2x faster than libsass * 1.9x faster than Dart Sass on Node ## Preceding Sparse `@extend` Running on a file containing `.x {@extend .y}`, 2^17 instances of `.foo {a: b}`, and then `.y {a: b}`: * sassc: 1.739s * Dart Sass from a script snapshot: 1.634s * Dart Sass native executable: 1.574s * Dart Sass on Node.js: 2.877s Based on these numbers, Dart Sass from a native executable is approximately: * 1.1x faster than libsass * 1.8x faster than Dart Sass on Node ## Following Sparse `@extend` Running on a file containing `.y {a: b}`, 2^17 instances of `.foo {a: b}`, and then `.x {@extend .y}`: * sassc: 1.726s * Dart Sass from a script snapshot: 1.536s * Dart Sass native executable: 1.512s * Dart Sass on Node.js: 2.768s Based on these numbers, Dart Sass from a native executable is approximately: * 1.1x faster than libsass * 1.8x faster than Dart Sass on Node ## Preceding Dense `@extend` Running on a file containing `.bar {@extend .foo}` followed by 2^17 instances of `.foo {a: b}`: * sassc: 2.356s * Dart Sass from a script snapshot: 2.556s * Dart Sass native executable: 2.628s * Dart Sass on Node.js: 5.737s Based on these numbers, Dart Sass from a native executable is approximately: * 1.1x slower than libsass * 2.2x faster than Dart Sass on Node ## Following Dense `@extend` Running on a file containing 2^17 instances of `.foo {a: b}` followed by `.bar {@extend .foo}`: * sassc: 2.377s * Dart Sass from a script snapshot: 2.420s * Dart Sass native executable: 2.440s * Dart Sass on Node.js: 5.841s Based on these numbers, Dart Sass from a native executable is approximately: * identical to libsass * 2.4x faster than Dart Sass on Node ## Bootstrap Running on a file containing 16 instances of importing the Bootstrap framework: * sassc: 0.820s * Dart Sass from a script snapshot: 1.558s * Dart Sass native executable: 0.927s * Dart Sass on Node.js: 3.129s Based on these numbers, Dart Sass from a native executable is approximately: * 1.1x slower than libsass * 3.4x faster than Dart Sass on Node ## a11ycolor Running on a file containing test cases for a computation-intensive color-processing library: * sassc: 0.264s * Dart Sass from a script snapshot: 0.699s * Dart Sass native executable: 0.375s * Dart Sass on Node.js: 0.792s Based on these numbers, Dart Sass from a native executable is approximately: * 1.4x slower than libsass * 2.1x faster than Dart Sass on Node ## Susy Running on a file containing test cases for the computation-intensive Susy grid framework: * sassc: 0.233s * Dart Sass from a script snapshot: 0.694s * Dart Sass native executable: 0.184s * Dart Sass on Node.js: 0.909s Based on these numbers, Dart Sass from a native executable is approximately: * 1.3x faster than libsass * 4.9x faster than Dart Sass on Node # Prior Measurements * [1.22.5](https://github.com/sass/dart-sass/blob/ed73c2c053435703cfbee8709f0dfb110cd31487/perf.md). * [1.22.4](https://github.com/sass/dart-sass/blob/a7172a2b1dd48b339e5d57159ed364ffb9f5812e/perf.md). * [1.20.2](https://github.com/sass/dart-sass/blob/4b7699291c9f69533d25980d23b0647266b665f2/perf.md). * [1.13.4](https://github.com/sass/dart-sass/blob/b6ccc91a138e75420227ff79381c5f70e60254f1/perf.md). * [1.6.0](https://github.com/sass/dart-sass/blob/048cbe197a77e1cf4b837a40a5acb737e949fd5c/perf.md). * [1.0.0-alpha.8](https://github.com/sass/dart-sass/blob/be44245a849f2bb18b5ca1fc74f3043a36da17f0/perf.md). * [Pre-alpha, 30 September 2016](https://github.com/sass/dart-sass/blob/169370bf18fd01d0618b0fc00d9db33e2fc52aa7/perf.md). * [Pre-alpha, 19 August 2016](https://github.com/sass/dart-sass/blob/4bea13cfe57d9e3c7f1f8580b80c59abe1cfabf8/perf.md). * [Pre-alpha, 15 July 2016](https://github.com/sass/dart-sass/blob/a3e00059c4371bfde9afada1759d8484aee05584/perf.md). # Conclusions This is the first measurement with Dart Sass running as ahead-of-time-compiled native code, and the results are encouraging. It's well below the 100ms threshold for tiny files, and it's on par with SassC for most test cases. SassC still leads for tests with many extends, although only slightly, and for one of our real-world test cases (although Dart Sass leads in others). The two implementations can be fairly described as having about the same performance overall. Dart Sass on Node is still substantially slower than on the Dart VM, and that relative slowdown becomes more pronounced as the raw Dart code becomes faster. Solutions for this such as [the embedded protocol][] or [WebAssembly support][] are becoming more and more important. [embedded Dart Sass]: https://github.com/sass/sass-embedded-protocol [Dart WebAssembly support]: https://github.com/dart-lang/sdk/issues/32894