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text<->double conversions refactored [message #57476]

Sun, 29 August 2021 13:57

mirek
Messages: 14291
Registered: November 2005

Ultimate Member

After month of development I have today commited refactored text<->double conversion routines (FormatDouble, ScanDouble...)

New routines should(*) guarantee that

- ScanDouble(FormatDouble(x)) == x for all finite doubles
- FormatG(x, 17) returns the same text as printf("%.17g", x) for all doubles

New routines are in the same speed class as ryu, wich seems to be current performance standard (conversion in both directions is around 20ns on modern CPU). (well, I believe my algorithm would be actually faster than ryu if it was doing the same thing, but U++ provides a lot of options which slow it down a bit to basically "ryu equivalent speed").

(*) Well, the theory behind is a bit complicated and I am still ironing details, but from practical point of view I have tested it so far with 300 billions of random double numbers and continue to do so...

https://github.com/ultimatepp/ultimatepp/blob/420697e4630d89 2aaf61b0ab8ba797a810ab7e14/uppsrc/Core/CvFlt.cpp

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[Message index]

		text<->double conversions refactored By: mirek on Sun, 29 August 2021 13:57
		Re: text<->double conversions refactored By: zsolt on Sun, 12 September 2021 20:50
		Re: text<->double conversions refactored By: Tom1 on Tue, 16 November 2021 09:44
		Re: text<->double conversions refactored By: Tom1 on Tue, 16 November 2021 10:03

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