Bill Allombert on Fri, 27 Sep 2019 21:29:47 +0200

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Re: qfbsolve (and ispseudoprime)

On Fri, Sep 27, 2019 at 02:58:43PM +0200, Paul Underwood wrote:
> It is a pity that the function qfbsolve is much slower in 2.12 alpha where it solves for composite n too.
> For example:
> gettime();k=198;n=2^p-3;if(qfbsolve(Qfb(1,0,1),n),print([k,gettime()]))
> overflows the default stack whereas it gives an almost instantaneous answer with version 2.11 and version 2.9.
> Also, qfbsolve(Qfb(1,0,1),n) *was* quicker than ispseudoprime for
> positive integers of the form 4*K+1,

If n is actually prime, then this is to be expected. 
ispseudoprime is a strong pseudo-primality test.
If you want a fast test rather than a strong test, use ispseudoprime(,1).