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* [Bug fortran/100561] New: Error while computing square of a real number (8 and 16 bytes) @ 2021-05-12 8:53 h0bb_88 at protonmail dot com 2021-05-12 8:58 ` [Bug fortran/100561] " h0bb_88 at protonmail dot com ` (5 more replies) 0 siblings, 6 replies; 7+ messages in thread From: h0bb_88 at protonmail dot com @ 2021-05-12 8:53 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100561 Bug ID: 100561 Summary: Error while computing square of a real number (8 and 16 bytes) Product: gcc Version: og10 (devel/omp/gcc-10) Status: UNCONFIRMED Severity: normal Priority: P3 Component: fortran Assignee: unassigned at gcc dot gnu.org Reporter: h0bb_88 at protonmail dot com Target Milestone: --- This simple example didn't give the same result than wolfram or any calculator : - result from program : 9.869604950... - result from other calculators : 9.869604401... The rounding is not the cause, because of error from 10° decimal, in 16-byte floating point. This error exist too in 8-byte floating-points number. Simple example : program main real(16), parameter :: pi = 3.1415926535897932384626433832795028841971693993751058209749445923 write(*,*) pi**2, pi*pi end program ^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug fortran/100561] Error while computing square of a real number (8 and 16 bytes) 2021-05-12 8:53 [Bug fortran/100561] New: Error while computing square of a real number (8 and 16 bytes) h0bb_88 at protonmail dot com @ 2021-05-12 8:58 ` h0bb_88 at protonmail dot com 2021-05-12 8:59 ` h0bb_88 at protonmail dot com ` (4 subsequent siblings) 5 siblings, 0 replies; 7+ messages in thread From: h0bb_88 at protonmail dot com @ 2021-05-12 8:58 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100561 --- Comment #1 from h0bb_88 at protonmail dot com --- Created attachment 50797 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=50797&action=edit Source code ^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug fortran/100561] Error while computing square of a real number (8 and 16 bytes) 2021-05-12 8:53 [Bug fortran/100561] New: Error while computing square of a real number (8 and 16 bytes) h0bb_88 at protonmail dot com 2021-05-12 8:58 ` [Bug fortran/100561] " h0bb_88 at protonmail dot com @ 2021-05-12 8:59 ` h0bb_88 at protonmail dot com 2021-05-12 9:02 ` h0bb_88 at protonmail dot com ` (3 subsequent siblings) 5 siblings, 0 replies; 7+ messages in thread From: h0bb_88 at protonmail dot com @ 2021-05-12 8:59 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100561 --- Comment #2 from h0bb_88 at protonmail dot com --- Created attachment 50798 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=50798&action=edit Comparison between f90 result and bc computation ^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug fortran/100561] Error while computing square of a real number (8 and 16 bytes) 2021-05-12 8:53 [Bug fortran/100561] New: Error while computing square of a real number (8 and 16 bytes) h0bb_88 at protonmail dot com 2021-05-12 8:58 ` [Bug fortran/100561] " h0bb_88 at protonmail dot com 2021-05-12 8:59 ` h0bb_88 at protonmail dot com @ 2021-05-12 9:02 ` h0bb_88 at protonmail dot com 2021-05-12 9:54 ` rguenth at gcc dot gnu.org ` (2 subsequent siblings) 5 siblings, 0 replies; 7+ messages in thread From: h0bb_88 at protonmail dot com @ 2021-05-12 9:02 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100561 --- Comment #3 from h0bb_88 at protonmail dot com --- System: Kernel: 5.8.0-53-generic x86_64 bits: 64 compiler: N/A Desktop: Cinnamon 4.8.6 wm: muffin dm: LightDM Distro: Linux Mint 20.1 Ulyssa base: Ubuntu 20.04 focal Machine: Type: Desktop Mobo: ASUSTeK model: Z170-K v: Rev X.0x serial: <filter> UEFI [Legacy]: American Megatrends v: 3805 date: 05/16/2018 CPU: Topology: Quad Core model: Intel Core i7-6700K bits: 64 type: MT MCP arch: Skylake-S rev: 3 L2 cache: 8192 KiB flags: avx avx2 lm nx pae sse sse2 sse3 sse4_1 sse4_2 ssse3 vmx bogomips: 63999 Speed: 3900 MHz min/max: 800/4200 MHz Core speeds (MHz): 1: 3900 2: 3900 3: 3900 4: 3900 5: 3900 6: 3900 7: 3900 8: 3900 ^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug fortran/100561] Error while computing square of a real number (8 and 16 bytes) 2021-05-12 8:53 [Bug fortran/100561] New: Error while computing square of a real number (8 and 16 bytes) h0bb_88 at protonmail dot com ` (2 preceding siblings ...) 2021-05-12 9:02 ` h0bb_88 at protonmail dot com @ 2021-05-12 9:54 ` rguenth at gcc dot gnu.org 2021-05-12 9:55 ` rguenth at gcc dot gnu.org 2021-05-12 9:56 ` pinskia at gcc dot gnu.org 5 siblings, 0 replies; 7+ messages in thread From: rguenth at gcc dot gnu.org @ 2021-05-12 9:54 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100561 --- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> --- It looks like gfortran parses the constant in single-precision, which might be an issue with your fortran source. ^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug fortran/100561] Error while computing square of a real number (8 and 16 bytes) 2021-05-12 8:53 [Bug fortran/100561] New: Error while computing square of a real number (8 and 16 bytes) h0bb_88 at protonmail dot com ` (3 preceding siblings ...) 2021-05-12 9:54 ` rguenth at gcc dot gnu.org @ 2021-05-12 9:55 ` rguenth at gcc dot gnu.org 2021-05-12 9:56 ` pinskia at gcc dot gnu.org 5 siblings, 0 replies; 7+ messages in thread From: rguenth at gcc dot gnu.org @ 2021-05-12 9:55 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100561 Richard Biener <rguenth at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |RESOLVED Resolution|--- |INVALID --- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> --- it is. real(8), parameter :: pi = 3.1415926535d0 works for example. ^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug fortran/100561] Error while computing square of a real number (8 and 16 bytes) 2021-05-12 8:53 [Bug fortran/100561] New: Error while computing square of a real number (8 and 16 bytes) h0bb_88 at protonmail dot com ` (4 preceding siblings ...) 2021-05-12 9:55 ` rguenth at gcc dot gnu.org @ 2021-05-12 9:56 ` pinskia at gcc dot gnu.org 5 siblings, 0 replies; 7+ messages in thread From: pinskia at gcc dot gnu.org @ 2021-05-12 9:56 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100561 --- Comment #6 from Andrew Pinski <pinskia at gcc dot gnu.org> --- This is invalid because you wrote: 3.1415926535897932384626433832795028841971693993751058209749445923 And not: 3.1415926535897932384626433832795028841971693993751058209749445923_16 The first is a real type which is already rounded to 64bit. When I used the _16, I get the correct answer. ^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2021-05-12 9:56 UTC | newest] Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2021-05-12 8:53 [Bug fortran/100561] New: Error while computing square of a real number (8 and 16 bytes) h0bb_88 at protonmail dot com 2021-05-12 8:58 ` [Bug fortran/100561] " h0bb_88 at protonmail dot com 2021-05-12 8:59 ` h0bb_88 at protonmail dot com 2021-05-12 9:02 ` h0bb_88 at protonmail dot com 2021-05-12 9:54 ` rguenth at gcc dot gnu.org 2021-05-12 9:55 ` rguenth at gcc dot gnu.org 2021-05-12 9:56 ` pinskia at gcc dot gnu.org
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