# two possible coding porjects

**Torbjorn Granlund
**
tege@swox.com

*05 Aug 2003 00:29:19 +0200*

stephen-nuchia@utulsa.edu writes:
Quoting Karl Hasselström <kha@treskal.com>:
> That is, you call a function that may or may not preinvert
> your divisor depending on how big it is, how many operations
> you'll do, etc.
OK, as long as there is a provision for telling it the number
of expected operations is very very large.
I think we'll use 0 as an approximation of infinity.
I.e., mpz_preinv_divisor (inv_a, a, 0) will be used
in such cases.
Pollard Rho spends a long time computing modular squares
against an invariant divisor that can be presumed to be
largish, for example. There is no way to know (without already
knowing the factorization) how many times it will use the
inverse.
Is that possible? So how many times will the divisor be used for
factoring 87029875480922160292881764593? The factorization is
40075522721471*2171646670357583. ;-)
In interactive programs it is also difficult to know in advance
how many times a divisor will be used. If the shell notices that
some number is being used as the size of a ring it ought to be
able to cache an inverse for it without a lot of drama.
Are you suggesting some clever enhancements to GNU bash?
--
Torbjörn