|Bill Allombert on Wed, 27 Jan 2016 14:57:56 +0100|
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|Re: Precision in the PARI library (gp_read_str)|
On Wed, Jan 27, 2016 at 02:38:01PM +0100, Rafael Guglielmetti wrote: > Dear PARI users, > I would like to compute the eigenvalues of a real symmetric matrix > with PARI in a C++ program. To create the matrix, I use several > information I read in a text file, create a string and use > gp_read_str. > > My problem: if one of the entry of the matrix is "sqrt(3)" for > example, then the correspondent t_GEN has DEFAULTPREC and I'd like > BIGDEFAULTPREC. > My question is the following: how can I increase the precision of > gp_read_str? You need to increase the default precision. If you use the stable version you can do long prec; setrealprecision(57,&prec); gp_read_str(....) If you use the master branch you can change the default precision locally with: push_localprec(BIGDEFAULTPREC); gp_read_str(....) pop_localprec(); Cheers, Bill.