Merge pull request #3167 from reyoung/gradient_check_utils

Initialize Gradient Checker

paddle/framework/pybind.cc

@@ -105,7 +105,16 @@ PYBIND11_PLUGIN(core) {
       .def("set", PyCUDATensorSetFromArray<float>)
       .def("set", PyCUDATensorSetFromArray<int>)
 #endif
-      .def("shape", [](Tensor &self) { return vectorize(self.dims()); });
+      .def("shape", [](Tensor &self) { return vectorize(self.dims()); })
+      .def("set_float_element",
+           [](Tensor &self, size_t offset, float f) {
+             // TODO(yuyang18): Only support GPU now.
+             self.data<float>()[offset] = f;
+           })
+      .def("get_float_element", [](Tensor &self, size_t offset) -> float {
+        // TODO(yuyang18): Only support GPU now.
+        return self.data<float>()[offset];
+      });
 
   py::class_<Variable>(m, "Variable", R"DOC(Variable Class.
 

python/paddle/v2/framework/tests/CMakeLists.txt

@@ -13,4 +13,5 @@ add_python_test(test_framework
     test_sigmoid_op.py
     test_softmax_op.py
     test_rowwise_add_op.py
-    test_network.py)
+    test_network.py
+    gradient_checker.py)

python/paddle/v2/framework/tests/gradient_checker.py

+import paddle.v2.framework.core as core
+from paddle.v2.framework.create_op_creation_methods import op_creations
+import numpy
+import unittest
+
+__all__ = ['get_numeric_gradient']
+
+
+def get_numeric_gradient(op,
+                         input_values,
+                         output_name,
+                         input_to_check,
+                         delta=1e-2,
+                         local_scope=None):
+    """
+    Get Numeric Gradient for an operator's input.
+    
+    :param op: C++ operator instance, could be an network 
+    :param input_values: The input variables. Should be an dictionary, key is 
+    variable name. Value is numpy array.
+    :param output_name: The final output variable name. 
+    :param input_to_check: The input variable need to get gradient.
+    :param delta: The perturbation value for numeric gradient method. The 
+    smaller delta is, the more accurate result will get. But if that delta is
+     too small, it could occur numerical stability problem.
+    :param local_scope: The local scope used for get_numeric_gradient.
+    :return: The gradient array in numpy format.
+    """
+    if local_scope is None:
+        local_scope = core.Scope()
+
+    # Create all input variable in local_scope
+    for var_name in input_values:
+        var = local_scope.new_var(var_name)
+        tensor = var.get_tensor()
+        tensor.set_dims(input_values[var_name].shape)
+        tensor.alloc_float(core.CPUPlace())
+        tensor.set(input_values[var_name], core.CPUPlace())
+
+    # Create all output variable in local_scope
+    for output in op.outputs():
+        if local_scope.find_var(output) is None:
+            local_scope.new_var(output).get_tensor()
+
+    op.infer_shape(local_scope)
+
+    # allocate output memory
+    for output in op.outputs():
+        local_scope.find_var(output).get_tensor().alloc_float(core.CPUPlace())
+
+    # TODO(yuyang18): Only CPU is support now.
+    cpu_ctx = core.DeviceContext.create(core.CPUPlace())
+
+    def get_output():
+        op.run(local_scope, cpu_ctx)
+        return numpy.array(local_scope.find_var(output_name).get_tensor()).sum()
+
+    def product(dim):
+        return reduce(lambda a, b: a * b, dim, 1)
+
+    tensor_to_check = local_scope.find_var(input_to_check).get_tensor()
+    tensor_size = product(tensor_to_check.get_dims())
+    gradient_flat = numpy.zeros(shape=(tensor_size, ), dtype='float32')
+    for i in xrange(tensor_size):
+        origin = tensor_to_check.get_float_element(i)
+        x_pos = origin + delta
+        tensor_to_check.set_float_element(i, x_pos)
+        y_pos = get_output()
+
+        x_neg = origin - delta
+        tensor_to_check.set_float_element(i, x_neg)
+        y_neg = get_output()
+
+        tensor_to_check.set_float_element(i, origin)  # restore old value
+        gradient_flat[i] = (y_pos - y_neg) / delta / 2
+    return gradient_flat.reshape(tensor_to_check.get_dims())
+
+
+if __name__ == '__main__':
+
+    class GetNumericGradientTest(unittest.TestCase):
+        def test_add_op(self):
+            add_op = op_creations.add_two(X="X", Y="Y", Out="Z")
+            x = numpy.random.random((10, 1)).astype("float32")
+            y = numpy.random.random((10, 1)).astype("float32")
+
+            arr = get_numeric_gradient(add_op, {'X': x, "Y": y}, 'Z', 'X')
+            self.assertAlmostEqual(arr.mean(), 1.0, delta=1e-2)
+
+    unittest.main()