Trainable conv net of MNIST (#4960)

* Init file

* Update

* Update

* Complete conv net of MNIST

python/paddle/v2/framework/nets.py

@@ -7,18 +7,21 @@ def simple_img_conv_pool(input,
                          pool_size,
                          pool_stride,
                          act,
-                         program=None):
+                         program=None,
+                         init_program=None):
     conv_out = layers.conv2d(
         input=input,
         num_filters=num_filters,
         filter_size=filter_size,
         act=act,
-        program=program)
+        program=program,
+        init_program=init_program)
 
     pool_out = layers.pool2d(
         input=conv_out,
         pool_size=pool_size,
         pool_type='max',
         pool_stride=pool_stride,
-        program=program)
+        program=program,
+        init_program=init_program)
     return pool_out

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

+import paddle.v2 as paddle
+import paddle.v2.framework.layers as layers
+import paddle.v2.framework.nets as nets
+import paddle.v2.framework.core as core
+import paddle.v2.framework.optimizer as optimizer
+
+from paddle.v2.framework.framework import Program, g_program
+from paddle.v2.framework.executor import Executor
+
+import numpy as np
+
+init_program = Program()
+program = Program()
+
+images = layers.data(
+    name='pixel',
+    shape=[1, 28, 28],
+    data_type='float32',
+    program=program,
+    init_program=init_program)
+label = layers.data(
+    name='label',
+    shape=[1],
+    data_type='int32',
+    program=program,
+    init_program=init_program)
+conv_pool_1 = nets.simple_img_conv_pool(
+    input=images,
+    filter_size=5,
+    num_filters=20,
+    pool_size=2,
+    pool_stride=2,
+    act="relu",
+    program=program,
+    init_program=init_program)
+conv_pool_2 = nets.simple_img_conv_pool(
+    input=conv_pool_1,
+    filter_size=5,
+    num_filters=50,
+    pool_size=2,
+    pool_stride=2,
+    act="relu",
+    program=program,
+    init_program=init_program)
+
+predict = layers.fc(input=conv_pool_2,
+                    size=10,
+                    act="softmax",
+                    program=program,
+                    init_program=init_program)
+cost = layers.cross_entropy(
+    input=predict, label=label, program=program, init_program=init_program)
+avg_cost = layers.mean(x=cost, program=program)
+
+sgd_optimizer = optimizer.SGDOptimizer(learning_rate=0.001)
+opts = sgd_optimizer.minimize(avg_cost)
+
+BATCH_SIZE = 50
+PASS_NUM = 1
+train_reader = paddle.batch(
+    paddle.reader.shuffle(
+        paddle.dataset.mnist.train(), buf_size=500),
+    batch_size=BATCH_SIZE)
+
+place = core.CPUPlace()
+exe = Executor(place)
+
+exe.run(init_program, feed={}, fetch_list=[])
+
+for pass_id in range(PASS_NUM):
+    count = 0
+    for data in train_reader():
+        img_data = np.array(map(lambda x: x[0].reshape([1, 28, 28]),
+                                data)).astype("float32")
+        y_data = np.array(map(lambda x: x[1], data)).astype("int32")
+        y_data = y_data.reshape([BATCH_SIZE, 1])
+
+        tensor_img = core.LoDTensor()
+        tensor_y = core.LoDTensor()
+        tensor_img.set(img_data, place)
+        tensor_y.set(y_data, place)
+
+        outs = exe.run(program,
+                       feed={"pixel": tensor_img,
+                             "label": tensor_y},
+                       fetch_list=[avg_cost])
+
+        loss = np.array(outs[0])
+
+        if loss < 10.0:
+            exit(0)  # if avg cost less than 10.0, we think our code is good.
+exit(1)