ENH: More descriptive error message on internal errors

On the example from issue #24, the raised exception now contains MKL's own
error message:

```
import numpy as np
from scipy.signal import fftconvolve
d1 = np.random.rand(18768768)
d2 = np.random.rand(15243648)
xcraw = fftconvolve(d1, d2, mode='full')
```

produces

```
ValueError: Internal error occurred: b'Intel MKL DFTI ERROR: Inconsistent configuration parameters'
```

Once the underlying issue in Intel(R) MKL is solved, the message will disappear
and the expected result will be computed, but addition of sensible description
of the nature of internal error is a good edition and will make future spelunking easier.

Author: oleksandr-pavlyk

mkl_fft/_pydfti.pyx

@@ -99,6 +99,7 @@ cdef extern from "src/mklfft.h":
     int double_cdouble_mkl_fftnd_out(cnp.ndarray, cnp.ndarray)
     int float_cfloat_mkl_ifftnd_out(cnp.ndarray, cnp.ndarray)
     int double_cdouble_mkl_ifftnd_out(cnp.ndarray, cnp.ndarray)
+    char * mkl_dfti_error(int)
 
 # Initialize numpy
 cnp.import_array()
@@ -265,6 +266,8 @@ def _fft1d_impl(x, n=None, axis=-1, overwrite_arg=False, direction=+1):
     cdef long n_, axis_
     cdef int x_type, f_type, status = 0
     cdef int ALL_HARMONICS = 1
+    cdef char * c_error_msg = NULL
+    cdef bytes py_error_msg
 
     x_arr = __process_arguments(x, n, axis, overwrite_arg, direction,
                                 &axis_, &n_, &in_place, &xnd, &dir_, 0)
@@ -307,7 +310,9 @@ def _fft1d_impl(x, n=None, axis=-1, overwrite_arg=False, direction=+1):
                 status = 1
 
         if status:
-            raise ValueError("Internal error, status={}".format(status))
+            c_error_msg = mkl_dfti_error(status)
+            py_error_msg = c_error_msg
+            raise ValueError("Internal error occurred: {}".format(py_error_msg))
 
         n_max = <long> cnp.PyArray_DIM(x_arr, axis_)
         if (n_ < n_max):
@@ -355,7 +360,9 @@ def _fft1d_impl(x, n=None, axis=-1, overwrite_arg=False, direction=+1):
                             x_arr, n_, <int> axis_, f_arr)
 
         if (status):
-            raise ValueError("Internal error occurred, status={}".format(status))
+            c_error_msg = mkl_dfti_error(status)
+            py_error_msg = c_error_msg
+            raise ValueError("Internal error occurred: {}".format(py_error_msg))
 
         return f_arr
 
@@ -379,6 +386,8 @@ def _rrfft1d_impl(x, n=None, axis=-1, overwrite_arg=False, direction=+1):
     cdef int xnd, err, n_max = 0, in_place, dir_
     cdef long n_, axis_
     cdef int x_type, status
+    cdef char * c_error_msg = NULL
+    cdef bytes py_error_msg
 
     x_arr = __process_arguments(x, n, axis, overwrite_arg, direction,
                                 &axis_, &n_, &in_place, &xnd, &dir_, 1)
@@ -419,7 +428,9 @@ def _rrfft1d_impl(x, n=None, axis=-1, overwrite_arg=False, direction=+1):
                 status = 1
 
         if status:
-            raise ValueError("Internal error, status={}".format(status))
+            c_error_msg = mkl_dfti_error(status)
+            py_error_msg = c_error_msg
+            raise ValueError("Internal error occurred: {}".format(py_error_msg))
 
         n_max = <long> cnp.PyArray_DIM(x_arr, axis_)
         if (n_ < n_max):
@@ -445,7 +456,9 @@ def _rrfft1d_impl(x, n=None, axis=-1, overwrite_arg=False, direction=+1):
                    status = float_float_mkl_rfft_out(x_arr, n_, <int> axis_, f_arr)
 
         if (status):
-            raise ValueError("Internal error occurred, status={}".format(status))
+            c_error_msg = mkl_dfti_error(status)
+            py_error_msg = c_error_msg
+            raise ValueError("Internal error occurred: {}".format(py_error_msg))
 
         return f_arr
 
@@ -463,7 +476,9 @@ def _rc_fft1d_impl(x, n=None, axis=-1, overwrite_arg=False):
     cdef long n_, axis_
     cdef int x_type, f_type, status, requirement
     cdef int HALF_HARMONICS = 0 # give only positive index harmonics
-    direction = 1 # dummy, only used for the sake of arg-processing
+    cdef int direction = 1 # dummy, only used for the sake of arg-processing
+    cdef char * c_error_msg = NULL
+    cdef bytes py_error_msg
 
     x_arr = __process_arguments(x, n, axis, overwrite_arg, direction,
                                 &axis_, &n_, &in_place, &xnd, &dir_, 1)
@@ -501,7 +516,9 @@ def _rc_fft1d_impl(x, n=None, axis=-1, overwrite_arg=False):
             status = double_cdouble_mkl_fft1d_out(x_arr, n_, <int> axis_, f_arr, HALF_HARMONICS)
 
     if (status):
-        raise ValueError("Internal error occurred, with status={}".format(status))
+        c_error_msg = mkl_dfti_error(status)
+        py_error_msg = c_error_msg
+        raise ValueError("Internal error occurred: {}".format(str(py_error_msg)))
 
     return f_arr
 
@@ -533,7 +550,9 @@ def _rc_ifft1d_impl(x, n=None, axis=-1, overwrite_arg=False):
     cdef int xnd, err, n_max = 0, in_place, dir_, int_n
     cdef long n_, axis_
     cdef int x_type, f_type, status
-    direction = 1 # dummy, only used for the sake of arg-processing
+    cdef int direction = 1 # dummy, only used for the sake of arg-processing
+    cdef char * c_error_msg = NULL
+    cdef bytes py_error_msg
 
     int_n = _is_integral(n)
     # nn gives the number elements along axis of the input that we use
@@ -579,7 +598,9 @@ def _rc_ifft1d_impl(x, n=None, axis=-1, overwrite_arg=False):
                 status = cdouble_double_mkl_irfft_out(x_arr, n_, <int> axis_, f_arr)
 
         if (status):
-            raise ValueError("Internal error occurred, status={}".format(status))
+            c_error_msg = mkl_dfti_error(status)
+            py_error_msg = c_error_msg
+            raise ValueError("Internal error occurred: {}".format(str(py_error_msg)))
 
         return f_arr
 

mkl_fft/src/mklfft.c.src

@@ -54,6 +54,11 @@ static NPY_INLINE MKL_LONG _to_mkl_long(npy_intp x)
     return lr;
 }
 
+NPY_INLINE char * mkl_dfti_error(MKL_LONG status)
+{
+    return DftiErrorMessage(status);
+}
+
 static npy_intp ar_size(npy_intp *sh, int len)
 {
     npy_intp r = (len > 0) ? 1 : 0;
@@ -567,11 +572,11 @@ int @name@_mkl_@mode@_in(PyArrayObject* x_inout, npy_intp n, int axis)
     }
 
 
-    return OK;
+    return status;
 
   failed:
 
-    return ERROR;
+    return status;
 }
 /**end repeat**/
 
@@ -841,7 +846,6 @@ int @REALIN@_@COMPLEXOUT@_mkl_@mode@_out(
 
   failed:
 
-    status = ERROR;
     goto cleanup;
 }
 /**end repeat**/
@@ -1016,7 +1020,6 @@ int @COMPLEXIN@_@COMPLEXOUT@_mkl_@mode@_out(
 
   failed:
 
-    status = ERROR;
     goto cleanup;
 }
 /**end repeat**/
@@ -1145,7 +1148,7 @@ int @name@_mkl_@mode@_in(PyArrayObject* x_inout, npy_intp n, int axis)
 
   failed:
 
-    return ERROR;
+    return status;
 }
 /**end repeat**/
 
@@ -1317,7 +1320,6 @@ int
 
   failed:
 
-    status = ERROR;
     goto cleanup;
 }
 /**end repeat**/
@@ -1496,7 +1498,6 @@ int @name@_@name@_mkl_@mode@_out(
 
   failed:
 
-    status = ERROR;
     goto cleanup;
 }
 /**end repeat**/

mkl_fft/src/mklfft.h

@@ -76,3 +76,5 @@ extern int float_cfloat_mkl_fftnd_out(PyArrayObject*, PyArrayObject*);
 extern int float_cfloat_mkl_ifftnd_out(PyArrayObject*, PyArrayObject*);
 extern int double_cdouble_mkl_fftnd_out(PyArrayObject*, PyArrayObject*);
 extern int double_cdouble_mkl_ifftnd_out(PyArrayObject*, PyArrayObject*);
+
+extern char* mkl_dfti_error(int);