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Date: Sat, 6 Jun 2026 16:24:18 -0700 (PDT)
To: KENNON J CONRAD via Cygwin <cygwin AT cygwin DOT com>,
        "Carlo B." <carlo DOT bramini AT gmail DOT com>,
        Dimitry Andric <dimitry AT unified-streaming DOT com>
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Subject: Re: log2() is not called for C code, a bug into math.h ?
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From: KENNON J CONRAD via Cygwin <cygwin AT cygwin DOT com>
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Should have written "I found that using log2 directly on my computer was slower than using log
with the divide".

> On 06/06/2026 4:06 PM PDT KENNON J CONRAD via Cygwin <cygwin AT cygwin DOT com> wrote:
> 
>  
> Hello Carlo B.,
> 
> There was another discussion of this issue back in January.  Beware, at the time I found that
> using log2 directly on my computer was slower than using log2 with the divide (by removing the
> same lines you mention in math.h).  It seems to me that in a perfect world, using log2 should
> be both more accurate and faster than calling log and dividing the result by a constant.
> 
> Best Regards,
> 
> Kennon Conrad
> 
> https://cygwin.com/pipermail/cygwin/2026-January/259314.html
> 
> > On 06/06/2026 9:53 AM PDT Carlo B. via Cygwin <cygwin AT cygwin DOT com> wrote:
> > 
> >  
> > Hello,
> > 
> > Il Sab 6 Giu 2026, 14:19 Dimitry Andric <dimitry AT unified-streaming DOT com> ha
> > scritto:
> > 
> > >
> > > It's been defined like that since the "import newlib-2000-02-17 snapshot",
> > > so for 26 years:
> > >
> > >
> > > https://sourceware.org/git/?p=newlib-cygwin.git;a=blob;f=newlib/libc/include/math.h;h=d3f2e99ae4d33596b608225f0349a6d581d265ca;hb=8a0efa53e44919bcf5ccb1d3353618a82afdf8bc#l103
> > >
> > > My guess is that at the time, there wasn't yet a separate log2()
> > > implementation, so this was an easy way to cover that case.
> > >
> > 
> > Thank you very much for the reply.
> > So, do you think that it would be possible to remove those lines from
> > math.h and use the log2() now provided?
> > 
> > Sincerely,
> > 
> > Carlo Bramini
> > 
> > 
> > > -Dimitry
> > >
> > >
> > 
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