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Some optimization.

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This commit is contained in:
Daniel Lemire 2020-10-27 21:11:19 -04:00
parent c53bfc4176
commit 8559cfa73f
2 changed files with 4 additions and 0 deletions
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3
include/fast_float/simple_decimal_conversion.h
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@ -356,6 +356,9 @@ adjusted_mantissa parse_long_mantissa(const char *first, const char* last) {
decimal d = parse_decimal(first, last); decimal d = parse_decimal(first, last);
const uint64_t mantissa = d.to_truncated_mantissa(); const uint64_t mantissa = d.to_truncated_mantissa();
const int64_t exponent = d.to_truncated_exponent(); const int64_t exponent = d.to_truncated_exponent();
// credit: Nigel Tao who first implemented this fast path (to my knowledge).
// It is rough, but it does the job of accelerating the slow path since most
// long streams of digits are determined after 19 digits.
adjusted_mantissa am1 = compute_float<binary>(exponent, mantissa); adjusted_mantissa am1 = compute_float<binary>(exponent, mantissa);
adjusted_mantissa am2 = compute_float<binary>(exponent, mantissa+1); adjusted_mantissa am2 = compute_float<binary>(exponent, mantissa+1);
if( am1 == am2 ) { return am1; } if( am1 == am2 ) { return am1; }

1
tests/basictest.cpp
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@ -139,6 +139,7 @@ int main() {
std::cout << "======= 64 bits " << std::endl; std::cout << "======= 64 bits " << std::endl;
Assert(basic_test_64bit("2.22507385850720212418870147920222032907240528279439037814303133837435107319244194686754406432563881851382188218502438069999947733013005649884107791928741341929297200970481951993067993290969042784064731682041565926728632933630474670123316852983422152744517260835859654566319282835244787787799894310779783833699159288594555213714181128458251145584319223079897504395086859412457230891738946169368372321191373658977977723286698840356390251044443035457396733706583981055420456693824658413747607155981176573877626747665912387199931904006317334709003012790188175203447190250028061277777916798391090578584006464715943810511489154282775041174682194133952466682503431306181587829379004205392375072083366693241580002758391118854188641513168478436313080237596295773983001708984375e-308", 0x1.0000000000002p-1022));
Assert(basic_test_64bit("1.0000000000000006661338147750939242541790008544921875",1.0000000000000007)); Assert(basic_test_64bit("1.0000000000000006661338147750939242541790008544921875",1.0000000000000007));
Assert(basic_test_64bit("1090544144181609348835077142190",0x1.b8779f2474dfbp+99)); Assert(basic_test_64bit("1090544144181609348835077142190",0x1.b8779f2474dfbp+99));
Assert(basic_test_64bit("2.2250738585072013e-308",2.2250738585072013e-308)); Assert(basic_test_64bit("2.2250738585072013e-308",2.2250738585072013e-308));