BF: allow for PPC64 little endian long doubles

Fix test failures for numpy / PPC 64 little-endian systems.

Closes gh-657.

Author: matthew-brett

nibabel/casting.py

@@ -268,6 +268,9 @@ def type_info(np_type):
         # 80) but in calculations nexp in fact appears to be 11 as for float64
         ret.update(dict(width=width))
         return ret
+    if vals == (105, 11, 16): # correctly detected double double
+        ret.update(dict(nmant=nmant, nexp=nexp, width=width))
+        return ret
     # Oh dear, we don't recognize the type information.  Try some known types
     # and then give up. At this stage we're expecting exotic longdouble or
     # their complex equivalent.

nibabel/tests/test_floating.py

@@ -30,6 +30,16 @@
 LD_INFO = type_info(np.longdouble)
 
 
+def dtt2dict(dtt):
+    """ Create info dictionary from numpy type
+    """
+    info = np.finfo(dtt)
+    return dict(min=info.min, max=info.max,
+                nexp=info.nexp, nmant=info.nmant,
+                minexp=info.minexp, maxexp=info.maxexp,
+                width=np.dtype(dtt).itemsize)
+
+
 def test_type_info():
     # Test routine to get min, max, nmant, nexp
     for dtt in np.sctypes['int'] + np.sctypes['uint']:
@@ -42,42 +52,36 @@ def test_type_info():
         assert_equal(infod['min'].dtype.type, dtt)
         assert_equal(infod['max'].dtype.type, dtt)
     for dtt in IEEE_floats + [np.complex64, np.complex64]:
-        info = np.finfo(dtt)
         infod = type_info(dtt)
-        assert_equal(dict(min=info.min, max=info.max,
-                          nexp=info.nexp, nmant=info.nmant,
-                          minexp=info.minexp, maxexp=info.maxexp,
-                          width=np.dtype(dtt).itemsize),
-                     infod)
+        assert_equal(dtt2dict(dtt), infod)
         assert_equal(infod['min'].dtype.type, dtt)
         assert_equal(infod['max'].dtype.type, dtt)
     # What is longdouble?
-    info = np.finfo(np.longdouble)
-    dbl_info = np.finfo(np.float64)
+    ld_dict = dtt2dict(np.longdouble)
+    dbl_dict = dtt2dict(np.float64)
     infod = type_info(np.longdouble)
-    width = np.dtype(np.longdouble).itemsize
-    vals = (info.nmant, info.nexp, width)
+    ld_dict['width'] = np.dtype(np.longdouble).itemsize
+    vals = tuple(ld_dict[k] for k in ('nmant', 'nexp', 'width'))
     # Information for PPC head / tail doubles from:
     # https://developer.apple.com/library/mac/#documentation/Darwin/Reference/Manpages/man3/float.3.html
     if vals in ((52, 11, 8),  # longdouble is same as double
                 (63, 15, 12), (63, 15, 16),  # intel 80 bit
                 (112, 15, 16),  # real float128
                 (106, 11, 16)):  # PPC head, tail doubles, expected values
-        assert_equal(dict(min=info.min, max=info.max,
-                          minexp=info.minexp, maxexp=info.maxexp,
-                          nexp=info.nexp, nmant=info.nmant, width=width),
-                     infod)
-    elif vals == (1, 1, 16):  # bust info for PPC head / tail longdoubles
-        assert_equal(dict(min=dbl_info.min, max=dbl_info.max,
-                          minexp=-1022, maxexp=1024,
-                          nexp=11, nmant=106, width=16),
-                     infod)
+        pass
+    elif vals == (105, 11, 16):  # bust info for PPC head / tail longdoubles
+        # min and max broken.
+        ld_dict['min'] = infod['min']
+        ld_dict['max'] = infod['max']
+    elif vals == (1, 1, 16):  # another bust info for PPC head / tail longdoubles
+        ld_dict = dbl_dict.copy()
+        ld_dict.update(dict(nmant=106, width=16))
     elif vals == (52, 15, 12):
-        exp_res = type_info(np.float64)
-        exp_res['width'] = width
-        assert_equal(exp_res, infod)
+        ld_dict = dbl_dict.copy()
+        ld_dict['width'] = width
     else:
-        raise ValueError("Unexpected float type to test")
+        raise ValueError("Unexpected float type {} to test".format(np.longdouble))
+    assert_equal(ld_dict, infod)
 
 
 def test_nmant():
@@ -103,7 +107,7 @@ def test_check_nmant_nexp():
     # Check against type_info
     for t in ok_floats():
         ti = type_info(t)
-        if ti['nmant'] != 106:  # This check does not work for PPC double pair
+        if ti['nmant'] not in (105, 106):  # This check does not work for PPC double pair
             assert_true(_check_nmant(t, ti['nmant']))
         # Test fails for longdouble after blacklisting of OSX powl as of numpy
         # 1.12 - see https://github.com/numpy/numpy/issues/8307