V Tue, 22 Dec 2015 21:10:54 +0000 rumbu via Digitalmars-d-learn <digitalmars-d-learn@puremagic.com> napsáno:
> On Tuesday, 22 December 2015 at 20:52:07 UTC, rumbu wrote: > > On Tuesday, 22 December 2015 at 19:45:46 UTC, Daniel Kozák > > wrote: > >> V Tue, 22 Dec 2015 18:11:24 +0000 > >> rumbu via Digitalmars-d-learn > >> <digitalmars-d-learn@puremagic.com> > >> napsáno: > >> > >>> On Tuesday, 22 December 2015 at 17:15:27 UTC, Andrew Chapman > >>> wrote: > >>> > Sorry if this is a silly question but is the to! method > >>> > from the conv library the most efficient way of converting > >>> > an integer value to a string? > >>> > > >>> > e.g. > >>> > string s = to!string(100); > >>> > > >>> > I'm seeing a pretty dramatic slow down in my code when I > >>> > use a conversion like this (when looped over 10 million > >>> > iterations for benchmarking). > >>> > > >>> > Cheers! > >>> > >>> Converting numbers to string involves the most expensive > >>> known two operations : division and modulus by 10. > >> > >> No, IIRC few months or maybe years I have optimize this so it > >> does not use division and modulus > > > > It's using division and modulus, as expected: > > > > https://github.com/D-Programming-Language/phobos/blob/master/std/conv.d#L5529 > > > > If the compiler is smart enough, maybe it will replace this by > > well known multiplication trick. > > Tested it, I was right: > > No optimizations: two divisions, one for the modulus and one for > the division itself > Optimized: multiplication by 0xCCCCCCCD trick. > > http://imgur.com/a/lHeHe > > Yes this is expected :).
