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From: "pozar at ecs dot umass.edu" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug fortran/98201] New: CSQRT function gives bad resuts at runtime Date: Tue, 08 Dec 2020 14:44:08 +0000 [thread overview] Message-ID: <bug-98201-4@http.gcc.gnu.org/bugzilla/> (raw) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98201 Bug ID: 98201 Summary: CSQRT function gives bad resuts at runtime Product: gcc Version: 9.2.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: fortran Assignee: unassigned at gcc dot gnu.org Reporter: pozar at ecs dot umass.edu Target Milestone: --- I am running mingw gfortran 9.2.0 on Windows 7, and have a problem with results from the CSQRT function during runtime. Sample code below, with results. Starting with a complex argument having increasingly large real part, and a relatively small imaginary part, csqrt initially gives a correct result (as tested by squaring the result from CSQRT). But the second row shows some significant error, and later rows show 'Infinity' for the imaginary part. (using sq = z**.5 gives correct results) F95 CODE; ! test CSQRT complex z, sq write(6,*) " Argument SquareRoot SR squared" do n=1,9 z=-10.**n+(0.,.1) sq=csqrt(z) write(*,1) z, sq, sq*sq end do 1 format(3("(",e10.4,2x,e10.4,")",3x)) pause RESULTS: Argument SquareRoot SR squared (-.1000E+02 0.1000E+00) (0.1581E-01 0.3163E+01) (-.1001E+02 0.1000E+00) (-.1000E+03 0.1000E+00) (0.5167E-02 0.9676E+01) (-.9362E+02 0.1000E+00) (-.1000E+04 0.1000E+00) (0.0000E+00 Infinity) ( -Infinity NaN) (-.1000E+05 0.1000E+00) (0.0000E+00 Infinity) ( -Infinity NaN) (-.1000E+06 0.1000E+00) (0.0000E+00 Infinity) ( -Infinity NaN) (-.1000E+07 0.1000E+00) (0.0000E+00 Infinity) ( -Infinity NaN) (-.1000E+08 0.1000E+00) (0.0000E+00 Infinity) ( -Infinity NaN) (-.1000E+09 0.1000E+00) (0.0000E+00 Infinity) ( -Infinity NaN) (-.1000E+10 0.1000E+00) (0.0000E+00 Infinity) ( -Infinity NaN) PAUSE
next reply other threads:[~2020-12-08 14:44 UTC|newest] Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-12-08 14:44 pozar at ecs dot umass.edu [this message] 2020-12-08 15:34 ` [Bug fortran/98201] " tkoenig at gcc dot gnu.org 2020-12-08 15:35 ` dominiq at lps dot ens.fr 2020-12-08 15:47 ` dpozar at ecs dot umass.edu 2020-12-08 15:54 ` dpozar at ecs dot umass.edu 2020-12-08 15:55 ` tkoenig at gcc dot gnu.org 2020-12-08 16:27 ` dpozar at ecs dot umass.edu 2020-12-08 17:36 ` kargl at gcc dot gnu.org 2020-12-08 18:19 ` tkoenig at gcc dot gnu.org 2020-12-08 19:13 ` dpozar at ecs dot umass.edu 2020-12-08 19:27 ` tkoenig at gcc dot gnu.org 2020-12-08 20:46 ` dpozar at ecs dot umass.edu 2020-12-08 22:06 ` kargl at gcc dot gnu.org 2020-12-09 0:28 ` dpozar at ecs dot umass.edu 2020-12-09 4:38 ` sgk at troutmask dot apl.washington.edu 2020-12-09 13:24 ` dpozar at ecs dot umass.edu 2020-12-09 15:37 ` sgk at troutmask dot apl.washington.edu 2020-12-09 16:04 ` dpozar at ecs dot umass.edu 2021-03-28 12:38 ` dominiq at lps dot ens.fr 2021-03-28 13:05 ` dpozar at ecs dot umass.edu 2021-03-28 13:16 ` dominiq at lps dot ens.fr
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