#9937: PARI real precision is broken in many ways
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Reporter: jdemeyer | Owner: was
Type: defect | Status: new
Priority: major | Milestone: sage-4.6
Component: interfaces | Keywords: pari gp real precision
Author: | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
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Description changed by jdemeyer:
Old description:
> The following do not work as they should (try these examples with a
> freshly started copy of Sage, such that everything is default).
>
> {{{
> # Default: 2 significant words (while we really should get only 1)
> sage: pari('Pi').debug()
> [&=0000000004fc9620] REAL(lg=4):0400000000000004
> (+,expo=1):6000000000000001 c90fdaa22168c234 c4c6628b80dc1cd1
>
> # Change precision and then change it back: we get 1 word
> sage: n = pari.get_real_precision(); pari.set_real_precision(100);
> pari.set_real_precision(n);
> sage: pari('Pi').debug()
> [&=00000000012bf200] REAL(lg=3):0400000000000003
> (+,expo=1):6000000000000001 c90fdaa22168c235
> }}}
>
> {{{
> # We cannot compute constants with high precision:
> sage: pari.set_real_precision(1000);
> sage: pari.euler().debug()
> [&=0000000004f75e20] REAL(lg=3):0400000000000003
> (+,expo=-1):5fffffffffffffff 93c467e37db0c7a5
> }}}
>
> Dependencies: #9898, #9893
New description:
The following do not work as they should (try these examples with a
freshly started copy of Sage, such that everything is default).
{{{
# Default: 2 significant words (while we really should get only 1)
sage: pari('Pi').debug()
[&=0000000004fc9620] REAL(lg=4):0400000000000004
(+,expo=1):6000000000000001 c90fdaa22168c234 c4c6628b80dc1cd1
# Change precision and then change it back: we get 1 word
sage: n = pari.get_real_precision(); pari.set_real_precision(100);
pari.set_real_precision(n);
sage: pari('Pi').debug()
[&=00000000012bf200] REAL(lg=3):0400000000000003
(+,expo=1):6000000000000001 c90fdaa22168c235
}}}
{{{
# set_real_precision() doesn't do anything for library functions:
sage: pari.set_real_precision(1000);
sage: pari.euler().debug()
[&=0000000004f75e20] REAL(lg=3):0400000000000003
(+,expo=-1):5fffffffffffffff 93c467e37db0c7a5
}}}
Dependencies: #9898, #9893
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Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/9937#comment:1>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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