GNU Scientific Library - Bugs: bug #47347, Complex tangent failure for -1000i

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bug #47347: Complex tangent failure for -1000i

Thu 15 Sep 2016 05:12:18 PM UTC, comment #2: Patch applied in commit 6f69962d548859d8ee1624e97077bd92e7e3730a	Patrick Alken <psa>
Mon 12 Sep 2016 04:51:09 AM UTC, comment #1: Please see test_tan.c for trouble shooting process and gsl_complex_tan.diff for a proposed fix. 1. This proposed fixed is based on 7141c7adb8100207ef01ff87a94d5179103fcebc which add a branch in gsl_complex_tanh to handle a similar issue. In this commit, tanh was modified to have a separate branch to handle large real part in input. This is what gsl_complex_tan.diff is doing in essense. In test_tan.c, this idea is implemented in `gsl_complex_tan_2` for testing purposes. 2. glibc implementation (https://github.com/lattera/glibc/blob/a2f34833b1042d5d8eeb263b4cf4caaea138c4ad/math/s_ctan.c) converts everything to exponential when the imagineary part is big. Is this a better implementation?	Yu Liu <yuliu>
Sat 05 Mar 2016 10:37:23 PM UTC, original submission: With a large negative imaginary component of the argument, the code for complex tangent ends up doing inf/inf. tan(-1000i) produces nan-nan*i for me. tan(1000i) produces i just fine. Suggestion: use tan(z)=conj(tan(conj(z))) whenever Im(z)<=-1.	M Welinder <terra>

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Attached Files

file #38480: gsl_complex_tan.diff added by yuliu (1KiB - application/octet-stream)

file #38481: test_tan.c added by yuliu (7KiB - application/octet-stream)

Depends on the following items: None found

Items that depend on this one: None found

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-email is unavailable- added by yuliu (Updated the item)

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Follow 4 latest changes.

Date	Changed by	Updated Field	Previous Value	Replaced by
2016-09-15	psa	Status	None	Fixed
		Open/Closed	Open	Closed
2016-09-12	yuliu	Attached File	-	Added gsl_complex_tan.diff, #38480
		Attached File	-	Added test_tan.c, #38481