BUG: always return MultEvaluator when requesting evaluator

gyral_structure/basis/core.py

@@ -321,9 +321,9 @@ class BasisFunc(object):
         :return: an :class:`RequestEvaluator <.evaluator.RequestEvaluator>` that has been set up to quickly evaluate the field
             at the requested positions given a vector field.
         """
-        from .evaluator import get_single_evaluator
+        from .evaluator import MultEvaluator
         with algorithm.set(method=method, override=True):
-            return get_single_evaluator(self, req)
+            return MultEvaluator(self, req)
 
     def param_evaluator(self, parameters, method=None, nsim=2**12):
         """Returns a function that evaluates the field at a given location
@@ -335,10 +335,10 @@ class BasisFunc(object):
         :param nsim: number of positions to evaluate simultaneously
         :return: function to map the positions to the field
         """
-        from .evaluator import get_single_evaluator
+        from .evaluator import MultEvaluator
         self.precompute_evaluator()
         with algorithm.set(store_matrix=False, method=method):
-            sim_evaluator = get_single_evaluator(self, request.PositionRequest(np.zeros((nsim, self.ndim))))
+            sim_evaluator = MultEvaluator(self, request.PositionRequest(np.zeros((nsim, self.ndim))))
             if sim_evaluator.use_mat:
                 warn("Running tractography with pre-computed matrix is very slow")
 

gyral_structure/basis/evaluator.py

@@ -464,10 +464,13 @@ class MultEvaluator(object):
         assert self.nparams == self.sum_basis.nparams
         self.request_list = list(set(self.full_request.flatten()))
 
+        self.fixed_field_evaluators = {req: [(bf.get_evaluator(req), params) for bf, params in fixed_field]
+                                       for req in self.request_list}
         if len(fixed_field) != 0:
-            self.fixed_field = {req: sp.sum([bf.get_evaluator(req)(params)
-                                             for bf, params in fixed_field], 0)
-                                for req in self.request_list}
+            self.fixed_field = {
+                req: sp.sum([evaluator(params) for evaluator, params in self.fixed_field_evaluators[req]], 0)
+                for req in self.request_list
+            }
 
         self.evaluators = sp.zeros((len(self.basis_list), len(self.request_list)), dtype='object')
         for idxb, (basis, _) in enumerate(self.basis_list):
@@ -629,3 +632,16 @@ class MultEvaluator(object):
     @property
     def use_mat(self, ):
         return any(eval.use_mat for eval in self.evaluators.flatten())
+
+    def update_pos(self, new_positions):
+        if len(self.request_list) > 1:
+            raise ValueError("Can't update the positions of multiple requests")
+        for evaluator in self.evaluators.flat:
+            evaluator.update_pos(new_positions)
+        for evaluator in self.fixed_field_evaluators[self.request_list[0]]:
+            evaluator.update_pos(new_positions)
+        if self.fixed_field:
+            self.fixed_field = {
+                req: sp.sum([evaluator(params) for evaluator, params in self.fixed_field_evaluators[req]], 0)
+                for req in self.request_list
+            }