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29380ff77d
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`)
46 lines
2.0 KiB
C
46 lines
2.0 KiB
C
/* fpconv_dtoa.h -- floating point conversion utilities.
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*
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* Fast and accurate double to string conversion based on Florian Loitsch's
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* Grisu-algorithm[1].
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*
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* [1] https://www.cs.tufts.edu/~nr/cs257/archive/florian-loitsch/printf.pdf
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* ----------------------------------------------------------------------------
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*
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* Copyright (c) 2013-2019, night-shift <as.smljk at gmail dot com>
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* Copyright (c) 2009, Florian Loitsch < florian.loitsch at inria dot fr >
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* All rights reserved.
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*
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* Boost Software License - Version 1.0 - August 17th, 2003
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*
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* Permission is hereby granted, free of charge, to any person or organization
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* obtaining a copy of the software and accompanying documentation covered by
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* this license (the "Software") to use, reproduce, display, distribute,
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* execute, and transmit the Software, and to prepare derivative works of the
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* Software, and to permit third-parties to whom the Software is furnished to
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* do so, all subject to the following:
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*
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* The copyright notices in the Software and this entire statement, including
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* the above license grant, this restriction and the following disclaimer,
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* must be included in all copies of the Software, in whole or in part, and
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* all derivative works of the Software, unless such copies or derivative
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* works are solely in the form of machine-executable object code generated by
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* a source language processor.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
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* SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
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* FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
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* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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* DEALINGS IN THE SOFTWARE.
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*/
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#ifndef FPCONV_DTOA_H
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#define FPCONV_DTOA_H
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int fpconv_dtoa(double fp, char dest[24]);
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#endif
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/* [1] http://florian.loitsch.com/publications/dtoa-pldi2010.pdf */
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