Add initial unit test for Problem class

Signed-off-by: Niklas Koep <niklas.koep@gmail.com>

pymanopt/tools/autodiff/autodiff.py

@@ -4,21 +4,19 @@
 
 
 def compile(problem, need_grad, need_hess):
-    # Conditionally load autodiff backend if needed
-    if ((need_grad and problem.grad is None and problem.egrad is None) or
-        (need_hess and problem.hess is None and problem.ehess is None)):
-        if isinstance(problem.cost, T.TensorVariable):
-            if not isinstance(problem.arg, T.TensorVariable):
-                raise ValueError(
-                    "Theano backend requires an argument with respect to "
-                    "which compilation of the cost function is to be carried "
-                    "out")
-            backend = _theano
-        elif callable(problem.cost):
-            backend = _autograd
-        else:
-            raise ValueError("Cannot identify autodiff backend from cost "
-                             "variable.")
+    # Conditionally load autodiff backend if needed.
+    if isinstance(problem.cost, T.TensorVariable):
+        if not isinstance(problem.arg, T.TensorVariable):
+            raise ValueError(
+                "Theano backend requires an argument with respect to "
+                "which compilation of the cost function is to be carried "
+                "out")
+        backend = _theano
+    elif callable(problem.cost):
+        backend = _autograd
+    else:
+        raise ValueError("Cannot identify autodiff backend from cost "
+                         "variable.")
 
     if problem.verbosity >= 1:
         print("Compiling cost function...")
@@ -28,10 +26,10 @@ def compile(problem, need_grad, need_hess):
         if problem.verbosity >= 1:
             print("Computing gradient of cost function...")
         problem.egrad = backend.gradient(problem.cost, problem.arg)
-        # Assume if Hessian is needed gradient is as well
-        if need_hess and problem.ehess is None and problem.hess is None:
-            if problem.verbosity >= 1:
-                print("Computing Hessian of cost function...")
-            problem.ehess = backend.hessian(problem.cost, problem.arg)
+
+    if need_hess and problem.ehess is None and problem.hess is None:
+        if problem.verbosity >= 1:
+            print("Computing Hessian of cost function...")
+        problem.ehess = backend.hessian(problem.cost, problem.arg)
 
     problem.cost = compiled_cost_function

tests/test_problem.py

@@ -0,0 +1,28 @@
+import unittest
+
+import numpy as np
+import numpy.linalg as la
+import numpy.random as rnd
+import numpy.testing as np_testing
+
+import theano.tensor as T
+
+import warnings
+
+from pymanopt import Problem
+from pymanopt.manifolds import Sphere
+
+
+class TestProblem(unittest.TestCase):
+    def setUp(self):
+        self.X = X = T.vector()
+        self.cost = T.exp(T.sum(X**2))
+
+        n = self.n = 15
+
+        self.man = Sphere(n)
+
+    def test_compile(self):
+        problem = Problem(man=self.man, cost=self.cost)
+        with self.assertRaises(ValueError):
+            problem.prepare()