wcalc : Message: Re: [wcalc] mod doesn't work wery well

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mod doesn't work wery well

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Message #51 of 114 |

Re: [wcalc] mod doesn't work wery well

Daniele <scrows@...> schrieb:

> $ time wcalc "2^56 % 57"
> ^C
>
> real 0m15.002s
> user 0m14.635s
> sys 0m0.003s
> $
>
> the standard operator takes too much time to calculate the
> solution (I never waited for its solution),

Heh, right. Counting up to 2^56 in 57-steps might take a while. ;-)

> can anything be done to solve this issue?

Sure. Patch attached.

Cheers,
Ingo

Wed Jun 28, 2006 6:05 pm

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Ingo van Lil <inguin@...>

ingo_swt

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Attachment:
wcalc-modulo.patch

Type:
text/x-patch

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Message #51 of 114 |

Expand Messages	Author	Sort by Date
I wanted the remainder of a division with big numbers, this is what I've done: $ time wcalc "2^56 - floor(2^56 / 57)*57" = 4 real 0m0.004s user 0m0.001s ...	Daniele scrows@...	Jun 28, 2006 10:15 am
... Heh, right. Counting up to 2^56 in 57-steps might take a while. ;-) ... Sure. Patch attached. Cheers, Ingo...	Ingo van Lil ingo_swt	Jun 28, 2006 6:30 pm
... Hmm. What is currently in CVS is this: mpfr_set_ui(temp, 0, GMP_RNDN); mpfr_div(temp, first, second, GMP_RNDN); mpfr_rint(temp, temp, GMP_RNDZ); ...	Kyle Wheeler m3m0ryh0l3	Jun 29, 2006 4:18 am
... What's the first line good for? ... -20 is not an option. The question is: When performing the integer division of -340 and 60, do you round the result by...	Ingo van Lil ingo_swt	Jun 29, 2006 8:03 am
... Hmm, not much, come to think of it. ... Hmm, well, I tend to like not being restrictive, and I also like maintaining the existing behavior. In Wcalc 1.x,...	Kyle Wheeler m3m0ryh0l3	Jun 29, 2006 9:35 pm
... Actually, if I'm reading the ADA reference manual correctly, the REM operator does exactly what your algorithm does (A REM B keeps the sign of A) while the...	Ingo van Lil ingo_swt	Jun 29, 2006 11:05 pm
... Well, I'm not saying I'm in love with ADA, I'm just suggesting we preserve the existing behavior for % and do a better/different one with a new operator...	Kyle Wheeler m3m0ryh0l3	Jun 30, 2006 1:23 am
... Well, rounding output towards zero would pick floor() or ceil() depending on the sign of output. I'm checking the sign of the first operand instead. So, if...	Ingo van Lil ingo_swt	Jun 30, 2006 8:35 am
Perhaps I found another bug in the mod operator, I don't know if the result change with the last modifies to the way the mod works, so .. For `m % n' where `m'...	Daniele scrows@...	Jul 5, 2006 3:35 pm
... Nope, that's wrong. Looks like I need to get this fixed version out asap. ~Kyle -- It is easier to be critical than to be correct. -- Benjamin Disraeli...	Kyle Wheeler m3m0ryh0l3	Jul 6, 2006 7:01 am

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