add a fast and simple rounding function with given precision #29518
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VinInn
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-code-checks Logs: https://cmssdt.cern.ch/SDT/code-checks/cms-sw-PR-29518/14777
Code check has found code style and quality issues which could be resolved by applying following patch(s)
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| // round with N significant bits | ||
| template <int N> | ||
| float roundAtPrecision(float x) { | ||
| if (edm::isNotFinite(x)) |
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other than this, what is the performance difference wrt reduceMantissaToNbits in libminifloat?
I'd rather not proliferate. If this is better and the isNotFinite is the only difference, perhaps it's better to update reduceMantissaToNbits
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reduceMantissaToNbits just truncate.
reduceMantissaToNbitsRounding most probably is numerically equivalent even if the code looks more complex
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but isn't this code actually a truncation?
I see the unit test assert(roundAtPrecision<0>(2.9) == 2.f); (round(2.9) = 3)
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It is a binary rounding
with only exponent (0 signficant bits) you have to choose between 2 and 4
so 2.9 rounds to 2 and pi to 4...
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+code-checks Logs: https://cmssdt.cern.ch/SDT/code-checks/cms-sw-PR-29518/14779
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A new Pull Request was created by @VinInn (Vincenzo Innocente) for master. It involves the following packages: DataFormats/Math @perrotta, @cmsbuild, @slava77 can you please review it and eventually sign? Thanks. cms-bot commands are listed here |
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duplicate of reduceMantissaToNbitsRounding |
As discussed in #29513 it would be useful to have a fast and simple function to round a floating point number to a given precision of N bits.
here is it!
compiler will simplify it in just 2 integer instructions
https://godbolt.org/z/rpBkVS