Unable to import random with python2.7 on power pc based machine

[ragreddy]

BPO	26743
Nosy	@rhettinger, @mdickinson, @vstinner, @skrah, @serhiy-storchaka, @csabella
Files	sqrt.c

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2018-02-14.07:34:47.156>
created_at = <Date 2016-04-13.00:56:46.007>
labels = ['type-bug', 'library']
title = 'Unable to import random with python2.7 on power pc based machine'
updated_at = <Date 2018-02-14.07:34:47.155>
user = 'https://bugs.python.org/ragreddy'

bugs.python.org fields:

activity = <Date 2018-02-14.07:34:47.155>
actor = 'mark.dickinson'
assignee = 'none'
closed = True
closed_date = <Date 2018-02-14.07:34:47.156>
closer = 'mark.dickinson'
components = ['Library (Lib)']
creation = <Date 2016-04-13.00:56:46.007>
creator = 'ragreddy'
dependencies = []
files = ['42459']
hgrepos = []
issue_num = 26743
keywords = []
message_count = 29.0
messages = ['263292', '263309', '263327', '263360', '263362', '263363', '263364', '263365', '263366', '263369', '263370', '263373', '263376', '263379', '263428', '263429', '263431', '263432', '263433', '263435', '263436', '263513', '263514', '263516', '263526', '263527', '263528', '312146', '312162']
nosy_count = 7.0
nosy_names = ['rhettinger', 'mark.dickinson', 'vstinner', 'skrah', 'serhiy.storchaka', 'ragreddy', 'cheryl.sabella']
pr_nums = []
priority = 'normal'
resolution = 'third party'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue26743'
versions = ['Python 2.7']

[ragreddy]

Hi, I am trying to import random on a power pc based machine and I see this exception. Could you please help me?

root@host# python
Python 2.7.3 (default, Apr  3 2016, 22:31:30)
[GCC 4.8.1] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import random
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python2.7/random.py", line 58, in <module>
    NV_MAGICCONST = 4 * _exp(-0.5)/_sqrt(2.0)
ValueError: math domain error
>>>

[rhettinger]

That's odd.

Try:
import math
print math.sqrt(2.0)
print math

Post what you see.

[mdickinson]

The output of struct.pack('<d', 2.0) would also be worth knowing about. I'm wondering whether there's some kind of endianness issue going on in the float-to-string conversions.

[ragreddy]

Hi, I apologize. I didn't expect a quick reply.
Here are the outputs you requested.

root@host:~# python
Python 2.7.3 (default, Apr  3 2016, 22:31:30)
[GCC 4.8.1] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import math
>>> print math.sqrt(2.0)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: math domain error
>>> print math
<module 'math' from '/usr/lib/python2.7/lib-dynload/math.so'>
>>> import struct
>>> struct.pack('<d', 2.0)
'\x00\x00\x00\x00\x00\x00\x00@'
>>>

[vstinner]

>>> print math.sqrt(2.0)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: math domain error

I'm surprised that such basic math function fails.

Can you please try to compile and run attached C program?

$ gcc sqrt.c -o sqrt -lm && ./sqrt
sqrt(2) = 1.41421

[ragreddy]

stinner victor, my host doesn't have a gcc compiler. is there a way you can give me the binary?

[ragreddy]

my host details:

Linux fpc0 3.10.62-ltsi-WR6.0.0.18_standard #1 SMP PREEMPT Sun Apr 3 23:17:02 PDT 2016 ppc64 ppc64 ppc64 GNU/Linux

[vstinner]

What is your Linux distribution and what is your CPU? (try to read /proc/cpuinfo)

You cannot install a C compiler?

[ragreddy]

It's windriver linux. Processor is PPC64-E5500

[serhiy-storchaka]

What is the output of struct.pack('d', 2.0) and struct.pack('d', float(2))?

[ragreddy]

Serhiy,

root@host:~# python
Python 2.7.3 (default, Apr  3 2016, 22:31:30)
[GCC 4.8.1] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import struct
>>> struct.pack('d', 2.0)
'@\x00\x00\x00\x00\x00\x00\x00'
>>> struct.pack('d', float(2))
'@\x00\x00\x00\x00\x00\x00\x00'
>>>