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flintlib / arb

Arb has been merged into FLINT -- use https://github.com/flintlib/flint/ instead
http://arblib.org/
GNU Lesser General Public License v2.1
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printing error messages ought to be conditional: https://trac.sagemath.org/ticket/28817 #302

Closed dimpase closed 4 years ago

dimpase commented 4 years ago

Please see comments on https://trac.sagemath.org/ticket/28817

tl;dr: in arf/get_mpfr.c and fmpr/get_mpfr.c there are

flint_printf("exception: exponent too large to convert to mpfr");

calls which cause too much noise in case of an exception.

fredrik-johansson commented 4 years ago

The problem isn't printing an error message when there is an exception; the problem is calling the function in a way that can trigger the exception in the first place. Either the Sage code should check the exponent range before trying to convert to an MPFR, or Arb should provide a version of this function which handles the overflow more smoothly than calling flint_abort().

dimpase commented 4 years ago

It's hard to deal with an error message in a context of Sage (or any interactive use, in fact). That's why there should be a way to suppress it (if you really think it's not handled better by a usual mechanism of aborting with a documented numeric code, which can be processed).

@vbraun ?

vbraun commented 4 years ago

IMHO a user of the library shouldn't have to figure out exactly what the limits are (which is moreover different on 32 and 64 bit afair), only to have the library then check it again.

As far as Sage is concerned, the current API of signaling the exception (which we then catch) is fine, were it not for text injected into stdio that then somewhat randomly pops out when buffers get flushed.

A different API that notifies the caller of the overflow via a return code, say, would be fine as well.

fredrik-johansson commented 4 years ago

Yes, I think the API should be different.

Arguably, this conversion should just follow MPFR semantics: if the exponent is out of range, underflow to 0 or overflow to infinity, setting the relevant MPFR exception flags.

fredrik-johansson commented 4 years ago

I have changed the behavior in f433b7597e140a6ebd556de59ff5ee086a18b0ab. It would be great if someone could test this in Sage to make sure it works as intended.

dimpase commented 4 years ago

OK, will be testing this - also on flint 2.6.0.alpha (which, I suppose, mandates a new arb release, due to a patch needed?), see https://trac.sagemath.org/ticket/29719