Remove unnecessary signal handling for low prec mpfr operations.

[robertwb]

_sig_on and _sig_off are more expensive than computing the result itself.

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Apply only attachment: trac_7879-RR-signal.2.rebased_to_4.7.2.alpha2.patch to the Sage library.

Component: basic arithmetic

Keywords: sd32

Author: Robert Bradshaw

Reviewer: Alex Ghitza, Mariah Lenox, William Stein

Merged: sage-4.7.2.alpha3

Issue created by migration from https://trac.sagemath.org/ticket/7879

[robertwb]

comment:1

Signal handling is omitted for functions/precisions that were clearly and uniformly in the millisecond range or less.

[robertwb]

Description changed:

--- 
+++ 
@@ -1 +1 @@
-`_sig_on` and {{{_sig_off}} are more expensive than computing the result itself. 
+`_sig_on` and `_sig_off` are more expensive than computing the result itself. 

[robertwb]

Attachment: 7879-RR-signal.patch.gz

[aghitza]

Reviewer: Alex Ghitza

[aghitza]

Author: Robert Bradshaw

[aghitza]

comment:3

This looks good. I have one question: you are hardcoding threshold precisions after which the signals should be used, mostly 1000, but also 10000 in a couple of places. Would it be better to have a global variable PREC_THRESHOLD set to 1000 at the top of the file, and then use it or 10*PREC_THRESHOLD where needed? It would make it easier to change this in the future, since a search for it would be all that's needed.

I'm marking this as needs_info. If you think it's not worth the trouble, I'll put a positive review.

[jdemeyer]

comment:4

I am proposing to close this ticket as invalid since #9678 makes sig_on() and sig_off() a lot faster. In any case, if you want to keep the patch, it needs rebasing (_sig_on and _sig_off must be replaced by sig_on() and sig_off() but there are more patch conflicts).