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[Qemu-devel] [Bug 645662] Re: QEMU x87 emulation of trig and other compl
From: |
Arno Wagner |
Subject: |
[Qemu-devel] [Bug 645662] Re: QEMU x87 emulation of trig and other complex ops is only at 64-bit precision, not 80-bit |
Date: |
Wed, 29 Nov 2017 16:33:31 -0000 |
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.
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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(-1.0000000000000002, 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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