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schubfach

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A C++ implementation of the Schubfach algorithm - fast and accurate conversion of IEEE-754 double values to decimal strings

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# Schubfach

A C++ implementation of the Schubfach algorithm - fast and accurate conversion
of IEEE-754 `double` values to decimal strings.

For a faster method see https://github.com/vitaut/zmij.

Usage:

```c++
#include "schubfach.h"
#include <stdio.h>

int main() {
  char buf[schubfach::buffer_size];
  schubfach::dtoa(6.62607015e-34, buf);
  puts(buf);
}
```

Average formatting time from [dtoa-benchmark](https://github.com/fmtlib/dtoa-benchmark), smaller is better:

| Function      | Time (ns) | Speedup |
|---------------|-----------|---------|
| ostringstream | 880.245   | 1.00x   |
| sprintf       | 742.654   | 1.19x   |
| doubleconv    | 83.629    | 10.53x  |
| ryu           | 37.184    | 23.67x  |
| schubfach     | 24.865    | 35.40x  |
| fmt           | 22.331    | 39.42x  |
| dragonbox     | 20.782    | 42.36x  |

The binary size is ~12kiB on an ARM-based macOS:

```
% c++ -c -Os -DNDEBUG -std=c++20 schubfach.cc
% du -Ah schubfach.o
 12K	schubfach.o
```

Build time is ~77ms by default and ~95ms with optimizations enabled as measured by

```
% time c++ -c -std=c++20 schubfach.cc [-O2]
```

taking the best of 3 runs.

schubfach

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