csFastFloat 2.0.0

csFastFloat : a fast and accurate float parser

C# port of Daniel Lemire's fast_float fully ported from C++ to C#. It is almost 7 times faster than the standard library in some cases while providing exact results.

Benchmarks

We use the realistic files in /data. The mesh.txt data file contains numbers that are easier to parse whereas the canada.txt data file is representative of a more challenging scenario. We compare the Double.Parse() function from the runtime library with our FastFloat.ParseDouble() function. The ParseNumberString() only function parses the string itself without any float computation: it might represent an upper bound on the possible performance.

BenchmarkDotNet=v0.12.1, OS=ubuntu 20.04 (container)
AMD EPYC 7262, 1 CPU, 16 logical and 8 physical cores
.NET Core SDK=5.0.102
  [Host]        : .NET Core 5.0.2 (CoreCLR 5.0.220.61120, CoreFX 5.0.220.61120), X64 RyuJIT
  .NET Core 5.0 : .NET Core 5.0.2 (CoreCLR 5.0.220.61120, CoreFX 5.0.220.61120), X64 RyuJIT

Job=.NET Core 5.0  Runtime=.NET Core 5.0

|                     Method |        FileName |      Mean |     Error |    StdDev |       Min | Ratio | MFloat/s |     MB/s |
|--------------------------- |---------------- |----------:|----------:|----------:|----------:|------:|---------:|---------:|
|    FastFloat.ParseDouble() | data/canada.txt |  5.140 ms | 0.0280 ms | 0.0262 ms |  5.105 ms |  0.14 |    21.77 |   408.99 |
| 'ParseNumberString() only' | data/canada.txt |  2.540 ms | 0.0053 ms | 0.0047 ms |  2.531 ms |  0.07 |    43.90 |   824.87 |
|             Double.Parse() | data/canada.txt | 37.147 ms | 0.3284 ms | 0.3071 ms | 36.443 ms |  1.00 |     3.05 |    57.29 |
|                            |                 |           |           |           |           |       |          |          |
|    FastFloat.ParseDouble() |   data/mesh.txt |  2.083 ms | 0.0029 ms | 0.0024 ms |  2.080 ms |  0.29 |    35.10 |   298.07 |
| 'ParseNumberString() only' |   data/mesh.txt |  1.298 ms | 0.0034 ms | 0.0032 ms |  1.294 ms |  0.18 |    56.45 |   479.30 |
|             Double.Parse() |   data/mesh.txt |  7.086 ms | 0.0911 ms | 0.0852 ms |  6.931 ms |  1.00 |    10.54 |    89.45 |

Requirements

.NET Core 3.1 or better. Under .NET 5 framework, the library takes advantage of the new Math.BigMul() function. Since v2.0, net standard 2.0 is supported.

Usage

Two functions are available: FastDoubleParser.ParseDouble and FastFloatParser.ParseFloat.

String, char * and ReadOnlySpan<char> are supported inputs.

using csFastFloat;


double x;
float y;
double answer = 0;
foreach (string l in lines)
{
        x = FastDoubleParser.ParseDouble(l);
        y = FastFloatParser.ParseFloat(l);
}

Input strings are expected to be valid UTF-16.

Trailing content in the string is ignored. You may pass an optional out int characters_consumed parameter FastDoubleParser.ParseDouble(l, out int characters_consumed) if you wich to check how many characters were processed. Some users may want to fail when the number of characters consumed does not match the string length.

For UTF-8 or ASCII inputs, you may pass a ReadOnlySpan<byte> argument. You can also pass an optional out int characters_consumed parameter to track the number of characters consumed by the number pattern.

Credit

This library is the main project in my master's degree under the direction of Professor Daniel Lemire at TELUQ University. A special thanks to Egor Bogatov and all contributors for their really meaningful contribution.

Reference

• Daniel Lemire, Number Parsing at a Gigabyte per Second, arXiv:2101.11408