mpz_limbs interface

Marc Glisse marc.glisse at
Thu Feb 6 16:17:36 UTC 2014

On Thu, 6 Feb 2014, Niels Möller wrote:

> Marc Glisse <marc.glisse at> writes:
>> Note that there exist standard functions like isfinite.
> But so far, we don't use any libm functions in gmp.


>>>  * no slower then the _GMP_IEEE_FLOATS definition (which extracts the
>>>    exponent via a union).
>> Are you sure about that?
> I'm not sure about anything... I'd expect that moving floating point
> values to integer registers (or to memory) is often slow.
>> If x is a denormal, x-x may take a very long
>> time to compute.
> I don't think the case of denormals is very important for performance.
> And there's a bit-by-bit normalization loop for that case later on. How
> long is "very long"? 10 cycles? 100 cycles?

I don't know exactly. I looked into it some time ago, there are some links 
in the first comment.

Marc Glisse

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