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Posted by gamo on March 17, 2006, 1:41 pm
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#!/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
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Posted by gamo on March 17, 2006, 8:53 pm
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On Fri, 17 Mar 2006, gamo wrote:
>=20
> #!/usr/local/bin/perl -w
>=20
> # use Math::PariInit qw( primes=3D12000000 stack=3D1e8 );
> # use Math::Pari qw(:all);
> use Math::Pari 'factor';
>=20
> # $i =3D PARI 0;
> # $P =3D PARI 1;
>=20
> for $i (0..1_000_000_000) {
> $P =3D 5*$i**4-10*$i**3+20*$i*$i-15*$i+11;
> $f =3D factor($P,0);
> # print "$f\n";
> # next if ($f =3D~ /-1/);
> @fact=3D ($f =3D~ /[\[|\;](\d+)\,/g);
> # print "@fact\n";
> for $j (@fact){
> =09if ($j%10!=3D1){
> =09 print "$f -> $j factor of P($i)=3D$P\n";
> =09}
> }
> # last if $i=3D=3D1000;
> }
>=20
>=20
> __END__
>=20
>=20
> 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.
>=20
> I do a sample calculation using 'echo "factor(number)" | gp' and this
> gives correct results. =20
>=20
> TIA, best regards=20
>=20
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) {
$P =3D 5*$i**4-10*$i**3+20*$i*$i-15*$i+11;
@f =3D `echo "factor($P)" | gp`;
# print "@f\n";
# @f2 =3D grep (/\[\d+\s/, @f);
# print "@f2\n";
@fact=3D map (/\[(\d+)\s/, @f);
# print "@fact\n";
for $j (@fact){
if ($j%10!=3D1){
print "$j factor of P($i)=3D$P\n";
}
}
if ($i % 10_000_000=3D=3D0) { print "."; }
# last if $i=3D=3D1000;
}
__END__
PS: use bignum; don't works here.
Best regards,
--=20
http://www.telecable.es/personales/gamo/
S=F3lo hay 10 tipos de personas, las que saben binario y las que no
perl -e 'print 111_111_111**2,"\n";'
--8323328-1598280312-1142646809=:27081--
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Posted by Sisyphus on March 18, 2006, 2:20 am
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.
.
>
>
> 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.
>
I think you could have provided a simpler test case:
use warnings;
use Math::Pari;
$f1 = Math::Pari::factor(72);
print $f1, "\n";
$z = 4225760561;
$f2 = Math::Pari::factor($z);
print $f2, "\n";
$p = PARI $z;
$f3 = Math::Pari::factor($p);
print $f3, "\n";
__END__
(You could, of course, further simplify the above code.) For me that
produces:
[2,3;3,2]
[-1,1;5,1;13,1;743,1;1433,1]
[-1,1;5,1;13,1;743,1;1433,1]
Quite clearly the first line is correct, since (2**3) * (3**2) == 72
Just as clearly, the second 2 lines are not what we expect.
There's obviously a problem when we get to 32-bit numbers. The unsigned long
4225760561, when treated as a signed int, becomes -69206735 - and it's not
hard to work out that the last 2 lines of output are the factorisation
of -69206735.
I'm not surprised that factor($z) in the above code returns what we see, but
I *did* think that factor($p) would have returned what you and I expected. I
think it's a bug - though I'm not an expert on Math::Pari and haven't read
the documentation very thoroughly.
As for what to do about this .... you could file a bug report at
http://rt.cpan.org/Public/Dist/Display.html?Name=Math-Pari , or you could
contact the author directly. I don't think he would mind that. (I think he
peruses this list, so he may yet respond to this thread.)
Cheers,
Rob
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Posted by Ilya Zakharevich on March 18, 2006, 2:32 am
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[A complimentary Cc of this posting was sent to
gamo
> 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.
How do you suppose we are going to treat this? Send you our
condolences? What else do you think we can do?
What version of what? What Math::Pari test suite was saying? Can you
shorten your program to 1 line?
Puzzled,
Ilya
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Posted by gamo on March 18, 2006, 5:30 am
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while the remaining parts are likely unreadable without MIME-aware tools.
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On Sat, 18 Mar 2006, Ilya Zakharevich wrote:
> [A complimentary Cc of this posting was sent to
> gamo=20
3094@jvz.es>:
>=20
Thank you.
> > 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.
>=20
> How do you suppose we are going to treat this? Send you our
> condolences? What else do you think we can do?
>=20
> What version of what? What Math::Pari test suite was saying? Can you
Math-Pari-2.010703.tar.gz
> shorten your program to 1 line?
>=20
No, I can't.
> Puzzled,
> Ilya
>=20
--=20
http://www.telecable.es/personales/gamo/
S=F3lo hay 10 tipos de personas, las que saben binario y las que no
perl -e 'print 111_111_111**2,"\n";'
--8323328-1710087361-1142677830=:22760--
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