#23354 closed defect (fixed)
numerical noise in libs/lcalc/lcalc_Lfuntion.pyx with clang4 and icc
Reported by:  fbissey  Owned by:  

Priority:  major  Milestone:  sage8.1 
Component:  porting  Keywords:  
Cc:  dimpase  Merged in:  
Authors:  François Bissey  Reviewers:  Dima Pasechnik 
Report Upstream:  N/A  Work issues:  
Branch:  6ec19b5 (Commits, GitHub, GitLab)  Commit:  
Dependencies:  Stopgaps: 
Description
One doctest in libs/lcalc/lcalc_Lfuntion.pyx
fails because of excessive numerical noise when sage is compiled with clang >= 4.0 or icc (17.04).
clang4.0.1
File "src/sage/libs/lcalc/lcalc_Lfunction.pyx", line 188, in sage.libs.lcalc.lcalc_Lfunction.Lfunction.hardy_z_function Failed example: L.hardy_z_function(0) Expected: 0.7939675904771... Got: 0.793967590477206  4.03312243040125e17*I
icc:
File "src/sage/libs/lcalc/lcalc_Lfunction.pyx", line 188, in sage.libs.lcalc.lcalc_Lfunction.Lfunction.hardy_z_function Failed example: L.hardy_z_function(0) Expected: 0.7939675904771... Got: 0.793967590477208  4.03312243040124e17*I
Change History (9)
comment:1 Changed 4 years ago by
 Branch set to u/fbissey/lcalc_numerical_noise
 Cc dimpase added
 Commit set to 7de256c24f2c63df50b667a32d7c4969524693af
 Status changed from new to needs_review
comment:2 Changed 4 years ago by
 Status changed from needs_review to needs_work
comment:3 Changed 4 years ago by
 Commit changed from 7de256c24f2c63df50b667a32d7c4969524693af to 6ec19b5c462c5a8d058a251364ab6512c3d1b03f
Branch pushed to git repo; I updated commit sha1. New commits:
6ec19b5  fix numerical noise

comment:4 Changed 4 years ago by
Ooops. There is now.
comment:5 Changed 4 years ago by
The question is whether we should rather remove ffastmath
from the flagswhich probably will fix this noise by itself. I haven't tried this yet.
comment:6 Changed 4 years ago by
If we have the flag for gcc as well, it is not obvious which way things will go. All three may converge to something slightly different again.
comment:7 Changed 4 years ago by
 Reviewers set to Dima Pasechnik
 Status changed from needs_work to positive_review
OK.
comment:8 Changed 4 years ago by
 Branch changed from u/fbissey/lcalc_numerical_noise to 6ec19b5c462c5a8d058a251364ab6512c3d1b03f
 Resolution set to fixed
 Status changed from positive_review to closed
comment:9 Changed 4 years ago by
 Commit 6ec19b5c462c5a8d058a251364ab6512c3d1b03f deleted
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