#13003: numerical evaluation of `erf` crashes PARI at large numbers
------------------------------------------------------------------+---------
Reporter: benjaminfjones |
Owner: burcin
Type: defect |
Status: new
Priority: minor |
Milestone: sage-5.1
Component: symbolics |
Resolution:
Keywords: erf pari sd40.5 | Work
issues:
Report Upstream: Reported upstream. Developers deny it's a bug. |
Reviewers:
Authors: | Merged
in:
Dependencies: |
Stopgaps:
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Comment (by benjaminfjones):
Here is an example that is closer to (part of) the problem:
Consider `erf(10^i)` where `i=5,6,7`:
{{{
sage: pari(10**5).erfc()
5.23488067975405 E-4342944825
sage: RR(pari(10**5).erfc())
0.000000000000000
}}}
looks good!
{{{
sage: pari(10**6).erfc()
3.15934761259943 E-434294481910
sage: RR(pari(10**6).erfc())
5.64243263573681e124617551
}}}
there's a bug.
Then,
{{{
sage: pari(10**7).erfc()
3.70390595226759 E-43429448190333
sage: RR(pari(10**7).erfc())
0.000000000000000
}}}
looks good again ?!?
If the input is too large, there is an overflow in PARI (the exponent is
too large for PARI to represent):
{{{
sage: pari(10**10).erfc()
---------------------------------------------------------------------------
PariError Traceback (most recent call
last)
/Users/jonesbe/sage/sage-5.0/<ipython console> in <module>()
/Users/jonesbe/sage/sage-5.0/local/lib/python2.7/site-
packages/sage/libs/pari/gen.so in sage.libs.pari.gen._pari_trap
(sage/libs/pari/gen.c:49843)()
PariError: (15)
}}}
and that's something we should probably address separately.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/13003#comment:6>
Sage <http://www.sagemath.org>
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