[New-bugs-announce] [issue18340] float related test has problem with Denormal Flush to Zero compiler options

[V.E.O]

New submission from V.E.O:

With Intel Compiler's default options or GCC with -mfpmath=sse, the built Python failed at float related test.

For failures in test_strtod:
Traceback (most recent call last):
  File ".\test_strtod.py", line 190, in test_boundaries
    self.check_strtod(s)
  File ".\test_strtod.py", line 104, in check_strtod
    "expected {}, got {}".format(s, expected, got))
AssertionError: '0x0.fffffffffffffp-1022' != '0x0.0p+0'
- 0x0.fffffffffffffp-1022
+ 0x0.0p+0
 : Incorrectly rounded str->float conversion for 22250738585072008690e-327: expected 0x0.fffffffffffffp-1022, got 0x0.0p+0

22250738585072008690e-327 is less than positive normalize float 2250738585072014e-308 in sys.float_info, that is denormal float

With SSE optimization opened on current compilers, Denormal Flush to Zero feature will flush all denormal float to 0 to avoid hardware unsupport and increase performance.

The tests here better be skipped on DFZ opened binaries.
http://bugs.python.org/issue1672332 is related to this problem.

Reference:
http://software.intel.com/sites/products/documentation/doclib/iss/2013/compiler/cpp-lin/GUID-3A5C3E47-250D-4178-A0D4-6C4ACDDA5EB8.htm

----------
components: Tests
messages: 192134
nosy: V.E.O, mark.dickinson
priority: normal
severity: normal
status: open
title: float related test has problem with Denormal Flush to Zero compiler options
type: behavior
versions: Python 3.3

_______________________________________
Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue18340>
_______________________________________