memory problem with GMP 5

Torbjorn Granlund tg at
Fri Jan 15 17:11:15 CET 2010

Paul Zimmermann <Paul.Zimmermann at> writes:

  I've noticed that GMP 5 uses much more internal memory for big multiplications
  than previous versions. For example with the following program on a 64-bit
  Core 2, top gives a maximal "RES" memory of 1.6g for GMP 4.3.2, and 2.4g for
  GMP 5, i.e., 50% more!

have you checked balanced multiplies too?  Do they, too, require much
more memory than 4.3?

  Note that the inputs a and b use about 0.5g, as does the result a*b. Thus
  GMP 4.3.2 uses extra memory of 0.6g to perform the product, whereas GMP 5
  uses 1.4g.
  With a given memory limit, this means that GMP 4.3.2 is able to perform larger
  computations than GMP 5.
This ought to be fixed.  My goal is actually to gradually *lower* GMP's
memory thirst!


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