More changes than I first noticed (issue #222)

Author: lmcinnes

hdbscan/dist_metrics.pyx

@@ -1108,31 +1108,27 @@ cdef class ArccosDistance(DistanceMetric):
 #
 cdef class PyFuncDistance(DistanceMetric):
     """PyFunc Distance
-
     A user-defined distance
-
     Parameters
     ----------
     func : function
         func should take two numpy arrays as input, and return a distance.
     """
     def __init__(self, func, **kwargs):
         self.func = func
-        x = np.random.random(10)
-        try:
-            d = self.func(x, x, **kwargs)
-        except TypeError:
-            raise ValueError("func must be a callable taking two arrays")
-
-        try:
-            d = float(d)
-        except TypeError:
-            raise ValueError("func must return a float")
-
         self.kwargs = kwargs
 
+    # in cython < 0.26, GIL was required to be acquired during definition of
+    # the function and inside the body of the function. This behaviour is not
+    # allowed in cython >= 0.26 since it is a redundant GIL acquisition. The
+    # only way to be back compatible is to inherit `dist` from the base class
+    # without GIL and called an inline `_dist` which acquire GIL.
     cdef inline DTYPE_t dist(self, DTYPE_t* x1, DTYPE_t* x2,
-                             ITYPE_t size) except -1 with gil:
+                             ITYPE_t size) nogil except -1:
+        return self._dist(x1, x2, size)
+
+    cdef inline DTYPE_t _dist(self, DTYPE_t* x1, DTYPE_t* x2,
+                              ITYPE_t size) except -1 with gil:
         cdef np.ndarray x1arr
         cdef np.ndarray x2arr
         x1arr = _buffer_to_ndarray(x1, size)