valkey/deps/fpconv/README.md

libfpconv

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Fast and accurate double to string conversion based on Florian Loitsch's Grisu-algorithm[1].

This port contains a subset of the 'C' version of Fast and accurate double to string conversion based on Florian Loitsch's Grisu-algorithm available at [github.com/night-shift/fpconv](https://github.com/night-shift/fpconv)).

[1] https://www.cs.tufts.edu/~nr/cs257/archive/florian-loitsch/printf.pdf
optimizing d2string() and addReplyDouble() with grisu2: double to string conversion based on Florian Loitsch's Grisu-algorithm (#10587) All commands / use cases that heavily rely on double to a string representation conversion, (e.g. meaning take a double-precision floating-point number like 1.5 and return a string like "1.5" ), could benefit from a performance boost by swapping snprintf(buf,len,"%.17g",value) by the equivalent [fpconv_dtoa](https://github.com/night-shift/fpconv) or any other algorithm that ensures 100% coverage of conversion. This is a well-studied topic and Projects like MongoDB. RedPanda, PyTorch leverage libraries ( fmtlib ) that use the optimized double to string conversion underneath. The positive impact can be substantial. This PR uses the grisu2 approach ( grisu explained on https://www.cs.tufts.edu/~nr/cs257/archive/florian-loitsch/printf.pdf section 5 ). test suite changes: Despite being compatible, in some cases it produces a different result from printf, and some tests had to be adjusted. one case is that `%.17g` (which means %e or %f which ever is shorter), chose to use `5000000000` instead of 5e+9, which sounds like a bug? In other cases, we changed TCL to compare numbers instead of strings to ignore minor rounding issues (`expr 0.8 == 0.79999999999999999`) 2022-10-15 09:17:41 +00:00			`libfpconv`

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			`Fast and accurate double to string conversion based on Florian Loitsch's Grisu-algorithm[1].`

			`This port contains a subset of the 'C' version of Fast and accurate double to string conversion based on Florian Loitsch's Grisu-algorithm available at [github.com/night-shift/fpconv](https://github.com/night-shift/fpconv)).`

			`[1] https://www.cs.tufts.edu/~nr/cs257/archive/florian-loitsch/printf.pdf`