Re: [Bug 645662] Re: QEMU x87 emulation of trig and other complex ops is only at 64-bit precision, not 80-bit

2020-11-22 Thread Arno Wagner 
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(-1.0002, 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: a...@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-
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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(-1.0002, 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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Re: [Qemu-devel] [Bug 645662] Re: QEMU x87 emulation of trig and other complex ops is only at 64-bit precision, not 80-bit

2019-08-16 Thread Arno Wagner 
Fine by me. I suggest to keep tracking this though, if necessary
in another bug item.

Regards,
Arno


On Fri, Aug 16, 2019 at 16:06:29 CEST, Peter Maydell wrote:
> Looking at our code we're still implementing the x87 insns FSIN, FCOS,
> FSINCOS, FPTAN, FPATAN, F2XM1, FYL2X, FYL2XP1 by "convert the floatx80
> to a host double and use the host C library functions", so I think this
> bug is still unfixed. If the C program in comment 1 and/or the Python
> code has stopped reporting failures it's probably just because the guest
> C library routines have stopped using the x87 80-bit FPU instructions
> internally.
> 
> 
> ** Changed in: qemu
>Status: Fix Released => Confirmed
> 
> -- 
> 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(-1.0002, 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: a...@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(-1.0002, 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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Re: [Qemu-devel] [Bug 645662] Re: QEMU x87 emulation of trig and other complex ops is only at 64-bit precision, not 80-bit

2019-08-16 Thread Arno Wagner 
To be sure, you can also run my original C test code from
2010. If that produces a bit-identtical result, then this
has indeed been fixed. If there are deviations in the last
digits, then the fingerprinting issues is still there, but
at least Python has stopped complaining.

Regards,
Arno

On Fri, Aug 16, 2019 at 07:47:59 CEST, Thomas Huth wrote:
> The test code from comment #1 now prints out the correct value with QEMU
> v4.1, so I think this has been fixed with the softfloat work that has
> been done within the last year.
> 
> ** Changed in: qemu
>Status: Confirmed => Fix Released
> 
> -- 
> 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:
>   Fix Released
> 
> 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(-1.0002, 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: a...@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:
  Fix Released

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(-1.0002, 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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[Qemu-devel] [Bug 645662] Re: QEMU x87 emulation of trig and other complex ops is only at 64-bit precision, not 80-bit

2017-11-29 Thread Arno Wagner 
That explains it. For most operations that approach works well as
basically nobody uses the 80 bit formats directly anyways. Unfortunately
asinh() is very badly conditioned in the region tested and it is not
enough.

A possible approach to fix this would be to use long double (128 bit)
were available instead of just double and to document this limitation
for double.

-- 
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(-1.0002, 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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Re: [Qemu-devel] [Bug 645662] Re: Python 3.1.2 math errors with Qemu 0.12.5

2017-01-23 Thread Arno Wagner 
I had a brief look at softfloat. In principle, it should fix the 
issue, but only if the FPU uses 80-bit double-extended-precision
internally. I guess the qemu FPU is still stuck at 64 bit double
internally and that does not cut it for some calculations.

Just to be sure, I re-tested the code from comment 1 and it does
work as expected with a real FPU.

Regards,
Arno


On Mon, Jan 23, 2017 at 22:20:18 CET, Thomas Huth wrote:
> Looks like your test code from comment #1 still prints out a wrong
> value, so the bug has apparently not been fixed by the FPU updates...
> 
> ** Changed in: qemu
>Status: Incomplete => Triaged
> 
> -- 
> You received this bug notification because you are subscribed to the bug
> report.
> https://bugs.launchpad.net/bugs/645662
> 
> Title:
>   Python 3.1.2 math errors with Qemu 0.12.5
> 
> Status in QEMU:
>   Triaged
> 
> 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(-1.0002, 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: a...@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:
  Python 3.1.2 math errors with Qemu 0.12.5

Status in QEMU:
  Triaged

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(-1.0002, 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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Re: [Qemu-devel] [Bug 645662] Re: Python 3.1.2 math errors with Qemu 0.12.5

2017-01-19 Thread Arno Wagner 
Hi,

I just tried for about 2 hours without success or getting any useful 
diagnostic to compile and run current qemu 2.8. No console,
no window opens, -curses does not work in .configure, despite
ncurses-dev being installed, etc. 

Quite frankly, as I have not used qemu for several years now, 
I cannot be bothered to fight through an apparently mostly
broken build and install process. I did include two diagnostic
options in my bug-report, please try them out yourself.

Regards,
Arno

On Thu, Jan 19, 2017 at 09:34:56 CET, Thomas Huth wrote:
> Can you still reproduce this problem with the latest version of QEMU? As
> far as I know, the FPU emulation has been completely switched to
> softfloat with the latest versions, so I assume your problem might be
> fixed in recent releases...
> 
> ** Changed in: qemu
>Status: New => Incomplete
> 
> -- 
> You received this bug notification because you are subscribed to the bug
> report.
> https://bugs.launchpad.net/bugs/645662
> 
> Title:
>   Python 3.1.2 math errors with Qemu 0.12.5
> 
> Status in QEMU:
>   Incomplete
> 
> 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(-1.0002, 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: a...@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:
  Python 3.1.2 math errors with Qemu 0.12.5

Status in QEMU:
  Incomplete

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(-1.0002, 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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[Qemu-devel] [Bug 645662] Re: Python 3.1.2 math errors with Qemu 0.12.5

2010-10-24 Thread Arno Wagner 
And I unexpectedly had more time to dig.

Findings:

  - asinh() is not in IEEE754, please ignore my comment about
non-conformity, sorry.
  - The calculation for asinh() is pretty badly conditioned, i.e.
it blows up errors in the basic calculations.
  - asinh() is implemented in glibc in assembler on the FPU stack.   
This would mean 80 bits float representation.

Error observations:

  Calculations for asinh( -2.1073424255447017e-08), derived from
  the Python 3.1.2 selftest. Formula is asinh(x) = log(x+sqrt(x*x+1))
  Reference is a calculation with long double (128 bit)

  - qemu:   6 correct digits behind the dot
  - C with double:  7 correct digits behind the dot
  - i387:  10 correct digits behind the dot

Possible root cause:

   The observed error may be due to qemu using 64 bit double math in
   the FPU implementation, instead of the 80 bit internal precision   
   a real i387 uses.

Comparison with kernel i387 emulation

   As an additional verification, I tried the calculations using the
   Linux kernel coprocessor emulation. This basically failed. With
   kernel 2_6_26 and 2_6_27 and the ''no387'' flag, the kernel locked
   up without output early during boot. With 2.6.34, I could not do
   an ssh login. I may try this again later, and especially try
   to find out what is wrong with qemu and 2.6.34.

Consequences:

  1) qemu is significantly less accurate for some mathematics than a
 genuine i387. This may cause problesm with sensitive mathematics
 developed on a real i387.
  2) qemu can be fingerprinted easily using this problem. This may
 have security implications.

Fix Options:

  1) - Moving the FPU internal representation to long double. It will
   still not be the same results as on an  i387, but it will be
   _more_ accurate instead of less, which generally is far less
   of a problem.

   Pro:  Higher accuracy
   Cons: Slower

 - Use code derived from the Linux kernel i387 FPU emulator.
   The emulator is not bit-exact, but relatively close and it
   is used at least on some small x86 architectures.

   Pro:  Higher accuracy
   Cons: Need to integrate foreign code

 - Leave it as it is but add a clear warning to the Known qemu
   Problems Section in the manual and Wiki (I did not find one, I
   think it should be added in an easily findable place), that
   i387 FPU emulation is only 64 bits internally and may be less
   exact for combined calculations done on the FPU stack, such
   as asinh() in glibc(), than a real i387.

   You may recommend to use kernel FPU emulation, but
   this may not work or be a pain to get working.

   Pro: Least work
   Cons: Not really a solution 

2) Fixing this is difficult and there are other ways to find
 out that you are running in qemu anyways. I think the security
 implications are insiginficant in most cases.

-- 
Python 3.1.2 math errors with Qemu 0.12.5
https://bugs.launchpad.net/bugs/645662
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.

Status in QEMU: New

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(-1.0002, 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#

[Qemu-devel] [Bug 645662] Re: Python 3.1.2 math errors with Qemu 0.12.5

2010-10-23 Thread Arno Wagner 
Forgot so say: This is still present in 0.13.0.

-- 
Python 3.1.2 math errors with Qemu 0.12.5
https://bugs.launchpad.net/bugs/645662
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.

Status in QEMU: New

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(-1.0002, 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#

[Qemu-devel] [Bug 645662] Re: Python 3.1.2 math errors with Qemu 0.12.5

2010-10-23 Thread Arno Wagner 
Just found time to look a bit deeper into this. The problem is in the (real) 
asinh() function. 
I think it is possible that somewhere a calculation was done in float instead 
of double or a double value was shortened to float.
Please note that until this is fixed, qemu i386 is not IEEE754 conform.

Minimal test code in c:
---
#include stdio.h
#include math.h

int main(){ /* compile with gcc -lm test.c */
  double x, y;
  x = -2.1073424255447017e-08;
  y = asinh(x);
  printf(y = %20.16e\n,y);
  printf(should be   -2.1073424255447017e-08\n);
}

---

-- 
Python 3.1.2 math errors with Qemu 0.12.5
https://bugs.launchpad.net/bugs/645662
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.

Status in QEMU: New

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(-1.0002, 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#

[Qemu-devel] [Bug 645662] [NEW] Python 3.1.2 math errors with Qemu 0.12.5

2010-09-22 Thread Arno Wagner 
Public bug reported:

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(-1.0002, 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#

** Affects: qemu
 Importance: Undecided
 Status: New

-- 
Python 3.1.2 math errors with Qemu 0.12.5
https://bugs.launchpad.net/bugs/645662
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.

Status in QEMU: New

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(-1.0002, 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#