moved python function to python backend

1 files changed, 304 insertions, 0 deletions

diff --git a/pyspike/python_backend.py b/pyspike/python_backend.py
new file mode 100644
index 0000000..9134149
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+++ b/pyspike/python_backend.py
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+""" python_backend.py
+
+Collection of python functions that can be used instead of the cython 
+implementation.
+
+Copyright 2014, Mario Mulanksy <mario.mulansky@gmx.net>
+
+"""
+
+import numpy as np
+
+from pyspike import PieceWiseConstFunc, PieceWiseLinFunc
+
+
+############################################################
+# isi_distance_python
+############################################################
+def isi_distance_python(s1, s2):
+    """ Plain Python implementation of the isi distance.
+    """
+    # compute the interspike interval
+    nu1 = s1[1:]-s1[:-1]
+    nu2 = s2[1:]-s2[:-1]
+    
+    # compute the isi-distance
+    spike_events = np.empty(len(nu1)+len(nu2))
+    spike_events[0] = s1[0]
+    # the values have one entry less - the number of intervals between events
+    isi_values = np.empty(len(spike_events)-1)
+    # 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])
+    index1 = 0
+    index2 = 0
+    index = 1
+    while True:
+        # check which spike is next - from s1 or s2
+        if s1[index1+1] < s2[index2+1]:
+            index1 += 1
+            # break condition relies on existence of spikes at T_end
+            if index1 >= len(nu1):
+                break
+            spike_events[index] = s1[index1]
+        elif s1[index1+1] > s2[index2+1]:
+            index2 += 1
+            if index2 >= len(nu2):
+                break
+            spike_events[index] = s2[index2]
+        else: # s1[index1+1] == s2[index2+1]
+            index1 += 1
+            index2 += 1
+            if (index1 >= len(nu1)) or (index2 >= len(nu2)):
+                break
+            spike_events[index] = s1[index1]
+        # compute the corresponding isi-distance
+        isi_values[index] = (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])
+
+
+############################################################
+# get_min_dist
+############################################################
+def get_min_dist(spike_time, spike_train, start_index=0):
+    """ Returns the minimal distance |spike_time - spike_train[i]| 
+    with i>=start_index.
+    """
+    d = abs(spike_time - spike_train[start_index])
+    start_index += 1
+    while start_index < len(spike_train):
+        d_temp = abs(spike_time - spike_train[start_index])
+        if d_temp > d:
+            break
+        else:
+            d = d_temp
+        start_index += 1
+    return d
+
+
+############################################################
+# spike_distance_python
+############################################################
+def spike_distance_python(spikes1, spikes2):
+    """ Computes the instantaneous spike-distance S_spike (t) of the two given
+    spike trains. The spike trains are expected to have auxiliary spikes at the
+    beginning and end of the interval. Use the function add_auxiliary_spikes to
+    add those spikes to the spike train.
+    Args:
+    - spikes1, spikes2: ordered arrays of spike times with auxiliary spikes.
+    Returns:
+    - PieceWiseLinFunc describing the spike-distance.
+    """
+    # check for auxiliary spikes - first and last spikes should be identical
+    assert spikes1[0]==spikes2[0], \
+        "Given spike trains seems not to have auxiliary spikes!"
+    assert spikes1[-1]==spikes2[-1], \
+        "Given spike trains seems not to have auxiliary spikes!"
+    # shorter variables
+    t1 = spikes1
+    t2 = spikes2
+
+    spike_events = np.empty(len(t1)+len(t2)-2)
+    spike_events[0] = t1[0]
+    y_starts = np.empty(len(spike_events)-1)
+    y_ends = np.empty(len(spike_events)-1)
+
+    index1 = 0
+    index2 = 0
+    index = 1
+    dt_p1 = 0.0
+    dt_f1 = get_min_dist(t1[1], t2, 0)
+    dt_p2 = 0.0
+    dt_f2 = get_min_dist(t2[1], t1, 0)
+    isi1 = max(t1[1]-t1[0], t1[2]-t1[1])
+    isi2 = max(t2[1]-t2[0], t2[2]-t2[1])
+    s1 = dt_f1*(t1[1]-t1[0])/isi1
+    s2 = dt_f2*(t2[1]-t2[0])/isi2
+    y_starts[0] = (s1*isi2 + s2*isi1) / ((isi1+isi2)**2/2)
+    while True:
+        # print(index, index1, index2)
+        if t1[index1+1] < t2[index2+1]:
+            index1 += 1
+            # break condition relies on existence of spikes at T_end
+            if index1+1 >= len(t1):
+                break
+            spike_events[index] = t1[index1]
+            # first calculate the previous interval end value
+            dt_p1 = dt_f1 # the previous time now was the following time before
+            s1 = dt_p1
+            s2 = (dt_p2*(t2[index2+1]-t1[index1]) + dt_f2*(t1[index1]-t2[index2])) / isi2
+            y_ends[index-1] = (s1*isi2 + s2*isi1) / ((isi1+isi2)**2/2)
+            # now the next interval start value
+            dt_f1 = get_min_dist(t1[index1+1], t2, index2)
+            isi1 = t1[index1+1]-t1[index1]
+            # s2 is the same as above, thus we can compute y2 immediately
+            y_starts[index] = (s1*isi2 + s2*isi1) / ((isi1+isi2)**2/2)
+        elif t1[index1+1] > t2[index2+1]:
+            index2 += 1
+            if index2+1 >= len(t2):
+                break
+            spike_events[index] = t2[index2]
+            # first calculate the previous interval end value
+            dt_p2 = dt_f2 # the previous time now was the following time before
+            s1 = (dt_p1*(t1[index1+1]-t2[index2]) + dt_f1*(t2[index2]-t1[index1])) / isi1
+            s2 = dt_p2
+            y_ends[index-1] = (s1*isi2 + s2*isi1) / ((isi1+isi2)**2/2)
+            # now the next interval start value
+            dt_f2 = get_min_dist(t2[index2+1], t1, index1)
+            #s2 = dt_f2
+            isi2 = t2[index2+1]-t2[index2]
+            # s2 is the same as above, thus we can compute y2 immediately
+            y_starts[index] = (s1*isi2 + s2*isi1) / ((isi1+isi2)**2/2)
+        else: # t1[index1+1] == t2[index2+1] - generate only one event
+            index1 += 1
+            index2 += 1
+            if (index1+1 >= len(t1)) or (index2+1 >= len(t2)):
+                break
+            assert dt_f2 == 0.0
+            assert dt_f1 == 0.0
+            spike_events[index] = t1[index1]
+            y_ends[index-1] = 0.0
+            y_starts[index] = 0.0
+            dt_p1 = 0.0
+            dt_p2 = 0.0
+            dt_f1 = get_min_dist(t1[index1+1], t2, index2)
+            dt_f2 = get_min_dist(t2[index2+1], t1, index1)
+            isi1 = t1[index1+1]-t1[index1]
+            isi2 = t2[index2+1]-t2[index2]
+        index += 1
+    # the last event is the interval end
+    spike_events[index] = t1[-1]
+    # the ending value of the last interval
+    isi1 = max(t1[-1]-t1[-2], t1[-2]-t1[-3])
+    isi2 = max(t2[-1]-t2[-2], t2[-2]-t2[-3])
+    s1 = dt_p1*(t1[-1]-t1[-2])/isi1
+    s2 = dt_p2*(t2[-1]-t2[-2])/isi2
+    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])
+
+
+############################################################
+# add_piece_wise_const_python
+############################################################
+def add_piece_wise_const_python(x1, y1, x2, y2):
+    x_new = np.empty(len(x1) + len(x2))
+    y_new = np.empty(len(x_new)-1)
+    x_new[0] = x1[0]
+    y_new[0] = y1[0] + y2[0]
+    index1 = 0
+    index2 = 0
+    index = 0
+    while (index1+1 < len(y1)) and (index2+1 < len(y2)):
+        index += 1
+        # print(index1+1, x1[index1+1], y1[index1+1], x_new[index])
+        if x1[index1+1] < x2[index2+1]:
+            index1 += 1
+            x_new[index] = x1[index1]
+        elif x1[index1+1] > x2[index2+1]:
+            index2 += 1
+            x_new[index] = x2[index2]
+        else: # x1[index1+1] == x2[index2+1]:
+            index1 += 1
+            index2 += 1
+            x_new[index] = x1[index1]
+        y_new[index] = y1[index1] + y2[index2]
+    # one array reached the end -> copy the contents of the other to the end
+    if index1+1 < len(y1):
+        x_new[index+1:index+1+len(x1)-index1-1] = x1[index1+1:]
+        y_new[index+1:index+1+len(y1)-index1-1] = y1[index1+1:] + \
+                                                      y2[-1]
+        index += len(x1)-index1-2
+    elif index2+1 < len(y2):
+        x_new[index+1:index+1+len(x2)-index2-1] = x2[index2+1:]
+        y_new[index+1:index+1+len(y2)-index2-1] = y2[index2+1:] + \
+                                                   y1[-1]
+        index += len(x2)-index2-2
+    else: # both arrays reached the end simultaneously
+        # only the last x-value missing
+        x_new[index+1] = x1[-1]
+    # the last value is again the end of the interval
+    # x_new[index+1] = x1[-1]
+    # only use the data that was actually filled
+
+    return x_new[:index+2], y_new[:index+1]
+
+
+############################################################
+# add_piece_lin_const_python
+############################################################
+def add_piece_wise_lin_python(x1, y11, y12, x2, y21, y22):
+    x_new = np.empty(len(x1) + len(x2))
+    y1_new = np.empty(len(x_new)-1)
+    y2_new = np.empty_like(y1_new)
+    x_new[0] = x1[0]
+    y1_new[0] = y11[0] + y21[0]
+    index1 = 0 # index for self
+    index2 = 0 # index for f
+    index = 0  # index for new
+    while (index1+1 < len(y11)) and (index2+1 < len(y21)):
+        # print(index1+1, x1[index1+1], self.y[index1+1], x_new[index])
+        if x1[index1+1] < x2[index2+1]:
+            # first compute the end value of the previous interval
+            # linear interpolation of the interval
+            y = y21[index2] + (y22[index2]-y21[index2]) * \
+                (x1[index1+1]-x2[index2]) / (x2[index2+1]-x2[index2])
+            y2_new[index] = y12[index1] + y
+            index1 += 1
+            index += 1
+            x_new[index] = x1[index1]
+            # and the starting value for the next interval
+            y1_new[index] = y11[index1] + y
+        elif x1[index1+1] > x2[index2+1]:
+            # first compute the end value of the previous interval
+            # linear interpolation of the interval
+            y = y11[index1] + (y12[index1]-y11[index1]) * \
+                (x2[index2+1]-x1[index1]) / \
+                (x1[index1+1]-x1[index1])
+            y2_new[index] = y22[index2] + y
+            index2 += 1
+            index += 1
+            x_new[index] = x2[index2]
+            # and the starting value for the next interval
+            y1_new[index] = y21[index2] + y
+        else: # x1[index1+1] == x2[index2+1]:
+            y2_new[index] = y12[index1] + y22[index2]
+            index1 += 1
+            index2 += 1
+            index += 1
+            x_new[index] = x1[index1]
+            y1_new[index] = y11[index1] + y21[index2]
+    # one array reached the end -> copy the contents of the other to the end
+    if index1+1 < len(y11):
+        # compute the linear interpolations values
+        y = y21[index2] + (y22[index2]-y21[index2]) * \
+            (x1[index1+1:-1]-x2[index2]) / (x2[index2+1]-x2[index2])
+        x_new[index+1:index+1+len(x1)-index1-1] = x1[index1+1:]
+        y1_new[index+1:index+1+len(y11)-index1-1] = y11[index1+1:]+y
+        y2_new[index:index+len(y12)-index1-1] = y12[index1:-1] + y
+        index += len(x1)-index1-2
+    elif index2+1 < len(y21):
+        # compute the linear interpolations values
+        y = y11[index1] + (y12[index1]-y11[index1]) * \
+            (x2[index2+1:-1]-x1[index1]) / \
+            (x1[index1+1]-x1[index1])
+        x_new[index+1:index+1+len(x2)-index2-1] = x2[index2+1:]
+        y1_new[index+1:index+1+len(y21)-index2-1] = y21[index2+1:] + y
+        y2_new[index:index+len(y22)-index2-1] = y22[index2:-1] + y
+        index += len(x2)-index2-2
+    else: # both arrays reached the end simultaneously
+        # only the last x-value missing
+        x_new[index+1] = x1[-1]
+    # finally, the end value for the last interval
+    y2_new[index] = y12[-1]+y22[-1]
+    # only use the data that was actually filled
+    return x_new[:index+2], y1_new[:index+1], y2_new[:index+1]