added fall-back to python when cython is missing

3 files changed, 50 insertions, 24 deletions

diff --git a/pyspike/distances.py b/pyspike/distances.py
index 7d7044b..3e97b77 100644
--- a/pyspike/distances.py
+++ b/pyspike/distances.py
@@ -33,10 +33,17 @@ def isi_profile(spikes1, spikes2):
     assert spikes1[-1] == spikes2[-1], \
         "Given spike trains seems not to have auxiliary spikes!"
 
-    # cython implementation
-    from cython_distance import isi_distance_cython
-
-    times, values = isi_distance_cython(spikes1, spikes2)
+    # load cython implementation
+    try:
+        from cython_distance import isi_distance_cython as isi_distance_impl
+    except ImportError:
+        print("Warning: isi_distance_cython not found. Make sure that PySpike \
+is installed by running\n 'python setup.py build_ext --inplace'!\n \
+Falling back to slow python backend.")
+        # use python backend
+        from python_backend import isi_distance_python as isi_distance_impl
+
+    times, values = isi_distance_impl(spikes1, spikes2)
     return PieceWiseConstFunc(times, values)
 
 
@@ -76,10 +83,17 @@ def spike_profile(spikes1, spikes2):
         "Given spike trains seems not to have auxiliary spikes!"
 
     # cython implementation
-    from cython_distance import spike_distance_cython
-
-    times, y_starts, y_ends = spike_distance_cython(spikes1, spikes2)
-
+    try:
+        from cython_distance import spike_distance_cython \
+            as spike_distance_impl
+    except ImportError:
+        print("Warning: spike_distance_cython not found. Make sure that \
+PySpike is installed by running\n 'python setup.py build_ext --inplace'!\n \
+Falling back to slow python backend.")
+        # use python backend
+        from python_backend import spike_distance_python as spike_distance_impl
+
+    times, y_starts, y_ends = spike_distance_impl(spikes1, spikes2)
     return PieceWiseLinFunc(times, y_starts, y_ends)
 
 
diff --git a/pyspike/function.py b/pyspike/function.py
index 46fdea2..b161034 100644
--- a/pyspike/function.py
+++ b/pyspike/function.py
@@ -83,14 +83,19 @@ class PieceWiseConstFunc:
         assert self.x[0] == f.x[0], "The functions have different intervals"
         assert self.x[-1] == f.x[-1], "The functions have different intervals"
 
-        # python implementation
-        # from python_backend import add_piece_wise_const_python
-        # self.x, self.y = add_piece_wise_const_python(self.x, self.y,
-        #                                              f.x, f.y)
-
         # cython version
-        from cython_add import add_piece_wise_const_cython
-        self.x, self.y = add_piece_wise_const_cython(self.x, self.y, f.x, f.y)
+        try:
+            from cython_add import add_piece_wise_const_cython as \
+                add_piece_wise_const_impl
+        except ImportError:
+            print("Warning: add_piece_wise_const_cython not found. Make sure \
+that PySpike is installed by running\n 'python setup.py build_ext --inplace'! \
+\n Falling back to slow python backend.")
+            # use python backend
+            from python_backend import add_piece_wise_const_python as \
+                add_piece_wise_const_impl
+
+        self.x, self.y = add_piece_wise_const_impl(self.x, self.y, f.x, f.y)
 
     def mul_scalar(self, fac):
         """ Multiplies the function with a scalar value
@@ -188,8 +193,18 @@ class PieceWiseLinFunc:
         #     self.x, self.y1, self.y2, f.x, f.y1, f.y2)
 
         # cython version
-        from cython_add import add_piece_wise_lin_cython
-        self.x, self.y1, self.y2 = add_piece_wise_lin_cython(
+        try:
+            from cython_add import add_piece_wise_lin_cython as \
+                add_piece_wise_lin_impl
+        except ImportError:
+            print("Warning: add_piece_wise_lin_cython not found. Make sure \
+that PySpike is installed by running\n 'python setup.py build_ext --inplace'! \
+\n Falling back to slow python backend.")
+            # use python backend
+            from python_backend import add_piece_wise_lin_python as \
+                add_piece_wise_lin_impl
+
+        self.x, self.y1, self.y2 = add_piece_wise_lin_impl(
             self.x, self.y1, self.y2, f.x, f.y1, f.y2)
 
     def mul_scalar(self, fac):
diff --git a/pyspike/python_backend.py b/pyspike/python_backend.py
index a1f5ea2..874c689 100644
--- a/pyspike/python_backend.py
+++ b/pyspike/python_backend.py
@@ -11,8 +11,6 @@ Distributed under the BSD License
 
 import numpy as np
 
-from pyspike import PieceWiseConstFunc, PieceWiseLinFunc
-
 
 ############################################################
 # isi_distance_python
@@ -32,7 +30,7 @@ def isi_distance_python(s1, s2):
     # add the distance of the first events
     # isi_values[0] = nu1[0]/nu2[0] - 1.0 if nu1[0] <= nu2[0] \
     #                 else 1.0 - nu2[0]/nu1[0]
-    isi_values[0] = (nu1[0] - nu2[0]) / max(nu1[0], nu2[0])
+    isi_values[0] = abs(nu1[0] - nu2[0]) / max(nu1[0], nu2[0])
     index1 = 0
     index2 = 0
     index = 1
@@ -56,14 +54,14 @@ def isi_distance_python(s1, s2):
                 break
             spike_events[index] = s1[index1]
         # compute the corresponding isi-distance
-        isi_values[index] = (nu1[index1] - nu2[index2]) / \
+        isi_values[index] = abs(nu1[index1] - nu2[index2]) / \
             max(nu1[index1], nu2[index2])
         index += 1
     # the last event is the interval end
     spike_events[index] = s1[-1]
     # use only the data added above
     # could be less than original length due to equal spike times
-    return PieceWiseConstFunc(spike_events[:index + 1], isi_values[:index])
+    return spike_events[:index + 1], isi_values[:index]
 
 
 ############################################################
@@ -187,8 +185,7 @@ def spike_distance_python(spikes1, spikes2):
     y_ends[index-1] = (s1*isi2 + s2*isi1) / ((isi1+isi2)**2/2)
     # use only the data added above
     # could be less than original length due to equal spike times
-    return PieceWiseLinFunc(spike_events[:index+1],
-                            y_starts[:index], y_ends[:index])
+    return spike_events[:index+1], y_starts[:index], y_ends[:index]
 
 
 ############################################################