BF: add check for powerpc platform and longdouble

Catch double pair on IBM PPC as well as Mac PPC

Author: matthew-brett

nibabel/casting.py

@@ -168,6 +168,14 @@ class FloatingError(Exception):
     pass
 
 
+def on_powerpc():
+    """ True if we are running on a Power PC platform
+
+    Has to deal with older Macs and IBM POWER7 series among others
+    """
+    return processor() == 'powerpc' or machine().startswith('ppc')
+
+
 def type_info(np_type):
     """ Return dict with min, max, nexp, nmant, width for numpy type `np_type`
 
@@ -249,10 +257,10 @@ def type_info(np_type):
     # complex equivalent.
     if not np_type in (np.longdouble, np.longcomplex) or width not in (16, 32):
         raise FloatingError('We had not expected type %s' % np_type)
-    if (vals == (1, 1, 16) and processor() == 'powerpc' and
+    if (vals == (1, 1, 16) and on_powerpc() and
         _check_maxexp(np.longdouble, 1024)):
         # double pair on PPC.  The _check_nmant routine does not work for this
-        # type, hence the processor check
+        # type, hence the powerpc platform check instead
         ret.update(dict(nmant = 106, width=width))
     elif (_check_nmant(np.longdouble, 52) and
           _check_maxexp(np.longdouble, 11)):

nibabel/tests/test_floating.py

@@ -1,12 +1,10 @@
 """ Test floating point deconstructions and floor methods
 """
-from platform import processor
-
 import numpy as np
 
 from ..casting import (floor_exact, ceil_exact, as_int, FloatingError,
                        int_to_float, floor_log2, type_info, _check_nmant,
-                       _check_maxexp, ok_floats)
+                       _check_maxexp, ok_floats, on_powerpc)
 
 from nose import SkipTest
 from nose.tools import assert_equal, assert_raises, assert_true, assert_false
@@ -234,7 +232,7 @@ def test_floor_exact():
                 assert_equal(func(-iv+1, t), -iv+1)
         # The nmant value for longdouble on PPC appears to be conservative, so
         # that the tests for behavior above the nmant range fail
-        if t is np.longdouble and processor() == 'powerpc':
+        if t is np.longdouble and on_powerpc():
             continue
         # Confirm to ourselves that 2**(nmant+1) can't be exactly represented
         iv = 2**(nmant+1)