Re: Math::Pari 'factor' is wrong

On Fri, 17 Mar 2006, gamo wrote:


#!/usr/local/bin/perl -w

# use Math::PariInit qw( primes=12000000 stack=1e8 );
# use Math::Pari qw(:all);
use Math::Pari 'factor';

# $i = PARI 0;
# $P = PARI 1;

for $i (0..1_000_000_000) {
$P = 5*$i**4-10*$i**3+20*$i*$i-15*$i+11;
$f = factor($P,0);
# print "$f\n";
# next if ($f =~ /-1/);
@fact= ($f =~ /[\[|\;](\d+)\,/g);
# print "@fact\n";
for $j (@fact){
if ($j%10!=1){
print "$f -> $j factor of P($i)=$P\n";
}
}
# last if $i==1000;
}


__END__


This code gives incorrects results as -1 as factor of a positive
integer or 5 as factor of a number not terminated in 5 or 0.

I do a sample calculation using 'echo "factor(number)" | gp' and this
gives correct results.

TIA, best regards


Well I have a workaround, but the speed is so slow that is impractical.

#!/usr/local/bin/perl -w

use Math::BigInt;

for $i (0..1_000_000_000) {
$P = 5*$i**4-10*$i**3+20*$i*$i-15*$i+11;
@f = `echo "factor($P)" | gp`;
# print "@f\n";
# @f2 = grep (/\[\d+\s/, @f);
# print "@f2\n";
@fact= map (/\[(\d+)\s/, @f);
# print "@fact\n";
for $j (@fact){
if ($j%10!=1){
print "$j factor of P($i)=$P\n";
}
}
if ($i % 10_000_000==0) { print "."; }
# last if $i==1000;
}

__END__

PS: use bignum; don't works here.
Best regards,

--
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