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Re: [Bug 645662] Re: QEMU x87 emulation of trig and other complex ops is


From: Arno Wagner
Subject: Re: [Bug 645662] Re: QEMU x87 emulation of trig and other complex ops is only at 64-bit precision, not 80-bit
Date: Sun, 22 Nov 2020 16:41:11 -0000

Talk about a "blast form the past!" This Bug is now over 10 years old. 
But at least somebody is still working on it and it was not
just quietly dropped. I can respect that. 

My original recommendation stands: At least use long double for the
calcuations where available. 

Regards,
Arno

On Sun, Nov 22, 2020 at 00:21:50 CET, Peter Maydell wrote:
> For 5.1 (commits 1f18a1e6ab8368a4, 5eebc49d2d0aa5fc7e,
> 5ef396e2ba865f34a, eca30647fc078f4) we reimplemented FPATAN, FYL2X,
> FYL2XP1, FPREM, FPREM1, F2XM1 to do proper 80-bit precision operations.
> However the trig operations FPTAN, FSINCOS, FSIN, FCOS are still
> implemented as naive "convert to host double and use host C library
> functions".
> 
> -- 
> You received this bug notification because you are subscribed to the bug
> report.
> https://bugs.launchpad.net/bugs/645662
> 
> Title:
>   QEMU x87 emulation of trig and other complex ops is only at 64-bit
>   precision, not 80-bit
> 
> Status in QEMU:
>   Confirmed
> 
> Bug description:
>   When doing the regression tests for Python 3.1.2 with Qemu 0.12.5, (Linux 
> version 2.6.26-2-686 (Debian 2.6.26-25lenny1)),
>   gcc (Debian 4.3.2-1.1) 4.3.2, Python compiled from sources within qemu,
>   3 math tests fail, apparently because the floating point unit is buggy. 
> Qmeu was compiled from original sources
>   on Debian Lenny with kernel  2.6.34.6 from kernel.org, gcc  (Debian 
> 4.3.2-1.1) 4.3. 
> 
>   Regression testing errors:
> 
>   test_cmath
>   test test_cmath failed -- Traceback (most recent call last):
>     File "/root/tools/python3/Python-3.1.2/Lib/test/test_cmath.py", line 364, 
> in
>       self.fail(error_message)
>   AssertionError: acos0034: acos(complex(-1.0000000000000002, 0.0))
>   Expected: complex(3.141592653589793, -2.1073424255447014e-08)
>   Received: complex(3.141592653589793, -2.1073424338879928e-08)
>   Received value insufficiently close to expected value.
> 
>   
>   test_float
>   test test_float failed -- Traceback (most recent call last):
>     File "/root/tools/python3/Python-3.1.2/Lib/test/test_float.py", line 479, 
> in
>       self.assertEqual(s, repr(float(s)))
>   AssertionError: '8.72293771110361e+25' != '8.722937711103609e+25'
> 
>   
>   test_math
>   test test_math failed -- multiple errors occurred; run in verbose mode for 
> deta
> 
>   =>
> 
>   runtests.sh -v test_math
> 
>   le01:~/tools/python3/Python-3.1.2# ./runtests.sh -v test_math
>   test_math BAD
>    1 BAD
>    0 GOOD
>    0 SKIPPED
>    1 total
>   le01:~/tools/python3/Python-3.1.2#
> 
> To manage notifications about this bug go to:
> https://bugs.launchpad.net/qemu/+bug/645662/+subscriptions

-- 
Arno Wagner,     Dr. sc. techn., Dipl. Inform.,    Email: arno@wagner.name
GnuPG: ID: CB5D9718  FP: 12D6 C03B 1B30 33BB 13CF  B774 E35C 5FA1 CB5D 9718
----
A good decision is based on knowledge and not on numbers. -- Plato

If it's in the news, don't worry about it.  The very definition of 
"news" is "something that hardly ever happens." -- Bruce Schneier

-- 
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/645662

Title:
  QEMU x87 emulation of trig and other complex ops is only at 64-bit
  precision, not 80-bit

Status in QEMU:
  Confirmed

Bug description:
  When doing the regression tests for Python 3.1.2 with Qemu 0.12.5, (Linux 
version 2.6.26-2-686 (Debian 2.6.26-25lenny1)),
  gcc (Debian 4.3.2-1.1) 4.3.2, Python compiled from sources within qemu,
  3 math tests fail, apparently because the floating point unit is buggy. Qmeu 
was compiled from original sources
  on Debian Lenny with kernel  2.6.34.6 from kernel.org, gcc  (Debian 
4.3.2-1.1) 4.3. 

  Regression testing errors:

  test_cmath
  test test_cmath failed -- Traceback (most recent call last):
    File "/root/tools/python3/Python-3.1.2/Lib/test/test_cmath.py", line 364, in
      self.fail(error_message)
  AssertionError: acos0034: acos(complex(-1.0000000000000002, 0.0))
  Expected: complex(3.141592653589793, -2.1073424255447014e-08)
  Received: complex(3.141592653589793, -2.1073424338879928e-08)
  Received value insufficiently close to expected value.

  
  test_float
  test test_float failed -- Traceback (most recent call last):
    File "/root/tools/python3/Python-3.1.2/Lib/test/test_float.py", line 479, in
      self.assertEqual(s, repr(float(s)))
  AssertionError: '8.72293771110361e+25' != '8.722937711103609e+25'

  
  test_math
  test test_math failed -- multiple errors occurred; run in verbose mode for 
deta

  =>

  runtests.sh -v test_math

  le01:~/tools/python3/Python-3.1.2# ./runtests.sh -v test_math
  test_math BAD
   1 BAD
   0 GOOD
   0 SKIPPED
   1 total
  le01:~/tools/python3/Python-3.1.2#

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