On 2017-02-12 21:14, Nils Bruin wrote:
sage: U=ComplexField(300)(1/2+sqrt(-3)/2)
sage: U._pari_()
0.500 + 0.866025403784439*I
so the thing the dilog is taken of doesn't even have the right precision
Actually, it does have the right precision, it's just that PARI only
prints a few
Why not use arb which seems faster:
sage: BF=ComplexBallField(600)
sage: %timeit _=(BF(-3).sqrt()/2+1/2).polylog(2)
1000 loops, best of 3: 1.57 ms per loop
sage: %timeit _=dilog(1/2+sqrt(-3)/2).n(600)
100 loops, best of 3: 2.97 ms per loop
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On Sunday, February 12, 2017 at 2:11:29 PM UTC-8, John Cremona wrote:
>
> About 8 years ago I spent a long time making sure that precision was
> handled correctly in converting between Sage and pari. Since then the
> interface has totally changed and possibly these recent changes are at
> fault
Update:
All the build dependencies of sagelib except libgap is in conda-forge now
for Linux and OS X. See
https://github.com/conda-forge/staged-recipes/issues/2357 for details on
what has to be done. If there are volunteers who would like to help me in
maintaining these conda recipes, please let m
About 8 years ago I spent a long time making sure that precision was
handled correctly in converting between Sage and pari. Since then the
interface has totally changed and possibly these recent changes are at
fault.
Jeroen do you know the answer?
On 12 Feb 2017 20:14, "Nils Bruin" wrote:
On
On Sunday, February 12, 2017 at 10:59:06 AM UTC-8, Matthias Goerner wrote:
>
> Careful: you are changing the default precision before calling dilog. That
> might mask the problem with pari's dilog.
Indeed, the dilog is just implemented as
self._parent(self._pari_().dilog())
and:
sage: U=Comp
Careful: you are changing the default precision before calling dilog. That
might mask the problem with pari's dilog.
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The dilog function is calling pari which does not seem to have this fault:
? \pb 600
realbitprecision = 600 significant bits (180 decimal digits displayed)
? z = (1+sqrt(-3))/2
%1 = 1/2 +
0.86602540378443864676372317075293618347140262690519031402790348972596650845440001854057309337862428783781
When I am trying to compute complex dilog's to high precision, sage gives
the wrong by just filling up with zeros:
ComplexField(600)(1/2+sqrt(-3)/2).dilog()
0.274155677808037739629767534643711712760705268010497093200683593750
