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author | filipe oliveira <filipecosta.90@gmail.com> | 2022-10-15 10:17:41 +0100 |
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committer | GitHub <noreply@github.com> | 2022-10-15 12:17:41 +0300 |
commit | 29380ff77d5da51d3065b810a9f93171f8724c1a (patch) | |
tree | d40fb96981280f3dd5ddea2833997cfc88d28b35 /deps/fpconv/README.md | |
parent | 9ab873d9d35e789a228c5281d57c9c4fdc1e4ce1 (diff) | |
download | redis-29380ff77d5da51d3065b810a9f93171f8724c1a.tar.gz |
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`)
Diffstat (limited to 'deps/fpconv/README.md')
-rw-r--r-- | deps/fpconv/README.md | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/deps/fpconv/README.md b/deps/fpconv/README.md new file mode 100644 index 000000000..d64ca685a --- /dev/null +++ b/deps/fpconv/README.md @@ -0,0 +1,9 @@ +libfpconv + +---------------------------------------------- + +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 |