Impl scalar switch case op with condition op

doc/design/switch.md

@@ -10,8 +10,7 @@ The following example shows the usage of `fluid.switch`.
 a = fluid.Var(10)
 b = fluid.Var(0)
 
-switch = fluid.switch()
-with switch.block():
+with switch() as switch:
     with switch.case(fluid.less_equal(a, 10)):
         fluid.print("Case 1")
     with switch.case(fluid.larger(a, 0)):

paddle/operators/conditional_block_op.cc

@@ -41,6 +41,21 @@ class ConditionalOp : public framework::OperatorBase {
         });
     return retv;
   }
+
+  bool ScalarCondition(
+      const std::vector<const framework::LoDTensor *> &ips) const {
+    if (!(ips.size() == 1UL && ips[0]->IsInitialized())) {
+      PADDLE_THROW("should have one initialized input as condition");
+    }
+    if (!(ips[0]->type().hash_code() == typeid(bool).hash_code() &&
+          ips[0]->numel() == 1)) {
+      PADDLE_THROW(
+          "condition input's data type should be bool, "
+          "numel should be 1, actual numel is %d",
+          ips[0]->numel());
+    }
+    return ips[0]->data<bool>()[0];
+  }
 };
 
 class ConditionalBlockOp : public ConditionalOp {
@@ -53,9 +68,15 @@ class ConditionalBlockOp : public ConditionalOp {
   void Run(const framework::Scope &scope,
            const platform::Place &dev_place) const override {
     auto xs = InputTensors(scope);
-    bool need_run = std::all_of(
-        xs.begin(), xs.end(),
-        [](const framework::LoDTensor *t) { return t->numel() != 0; });
+
+    bool need_run;
+    if (Attr<bool>("is_scalar_condition")) {
+      need_run = ScalarCondition(xs);
+    } else {
+      need_run = std::all_of(
+          xs.begin(), xs.end(),
+          [](const framework::LoDTensor *t) { return t->numel() != 0; });
+    }
 
     if (need_run) {
       auto *scope_var = scope.FindVar(Output("Scope"));
@@ -88,6 +109,10 @@ class ConditionalBlockOpProtoMaker : public framework::OpProtoAndCheckerMaker {
               "scope is std::vector<Scope*>");
     AddAttr<framework::BlockDesc *>(
         "sub_block", "The step block of conditional block operator");
+    AddAttr<bool>("is_scalar_condition",
+                  "the input X is used as scalar "
+                  "condition")
+        .SetDefault(false);
     AddComment(R"DOC(Conditional block operator
 
 Run the sub-block if X is not empty. Params is the other inputs and Out is the
@@ -106,9 +131,15 @@ class ConditionalBlockGradOp : public ConditionalOp {
   void Run(const framework::Scope &scope,
            const platform::Place &dev_place) const override {
     auto xs = this->InputTensors(scope);
-    bool need_run = std::all_of(
-        xs.begin(), xs.end(),
-        [](const framework::LoDTensor *t) { return t->numel() != 0; });
+
+    bool need_run;
+    if (Attr<bool>("is_scalar_condition")) {
+      need_run = ScalarCondition(xs);
+    } else {
+      need_run = std::all_of(
+          xs.begin(), xs.end(),
+          [](const framework::LoDTensor *t) { return t->numel() != 0; });
+    }
 
     if (need_run) {
       auto *scope_var = scope.FindVar(Input("Scope"));
@@ -182,6 +213,7 @@ class ConditionalBlockGradMaker : public framework::SingleGradOpDescMaker {
     grad_op->SetOutput(framework::GradVarName("Params"),
                        InputGrad("Params", false));
     grad_op->SetBlockAttr("sub_block", *this->grad_block_[0]);
+    grad_op->SetAttr("is_scalar_condition", GetAttr("is_scalar_condition"));
     return std::unique_ptr<framework::OpDesc>(grad_op);
   }
 };

python/paddle/v2/fluid/layers/control_flow.py

@@ -18,6 +18,7 @@
 from .. import core
 from ..framework import Program, Variable, Operator
 from ..layer_helper import LayerHelper, unique_name
+from ops import logical_and, logical_not, logical_or
 
 __all__ = [
     'split_lod_tensor',
@@ -27,6 +28,7 @@
     'StaticRNNMemoryLink',
     'WhileGuard',
     'While',
+    'Switch',
     'lod_rank_table',
     'max_sequence_len',
     'topk',
@@ -1063,11 +1065,12 @@ def __exit__(self, exc_type, exc_val, exc_tb):
 
 
 class ConditionalBlock(object):
-    def __init__(self, inputs, name=None):
+    def __init__(self, inputs, is_scalar_condition=False, name=None):
         for each_input in inputs:
             if not isinstance(each_input, Variable):
                 raise TypeError("Each input should be variable")
         self.inputs = inputs
+        self.is_scalar_condition = is_scalar_condition
         self.helper = LayerHelper('conditional_block', name=name)
 
     def block(self):
@@ -1112,7 +1115,66 @@ def complete(self):
             },
             outputs={'Out': out_list,
                      'Scope': [step_scope]},
-            attrs={'sub_block': inside_block})
+            attrs={
+                'sub_block': inside_block,
+                'is_scalar_condition': self.is_scalar_condition
+            })
+
+
+class Switch(object):
+    def __init__(self, name=None):
+        self.helper = LayerHelper('switch', name=name)
+        self.inside_scope = False
+        self.pre_not_conditions = []
+
+    def case(self, condition):
+        """create a new block for this condition
+        """
+        if not self.inside_scope:
+            raise ValueError("case should be called inside with")
+
+        if len(self.pre_not_conditions) == 0:
+            cond_block = ConditionalBlock([condition], is_scalar_condition=True)
+            not_cond = logical_not(x=condition)
+            self.pre_not_conditions.append(not_cond)
+        else:
+            pre_cond_num = len(self.pre_not_conditions)
+            pre_not_cond = self.pre_not_conditions[pre_cond_num - 1]
+            new_not_cond = logical_and(
+                x=pre_not_cond, y=logical_not(x=condition))
+            self.pre_not_conditions.append(new_not_cond)
+            cond_block = ConditionalBlock(
+                [logical_and(
+                    x=pre_not_cond, y=condition)],
+                is_scalar_condition=True)
+
+        return ConditionalBlockGuard(cond_block)
+
+    def default(self):
+        """create a default case for this switch
+        """
+        pre_cond_num = len(self.pre_not_conditions)
+        if pre_cond_num == 0:
+            raise ValueError("there should be at least one condition")
+        cond_block = ConditionalBlock(
+            [self.pre_not_conditions[pre_cond_num - 1]],
+            is_scalar_condition=True)
+        return ConditionalBlockGuard(cond_block)
+
+    def __enter__(self):
+        """
+        set flag that now is inside switch.block {}
+        :return:
+        """
+        self.inside_scope = True
+        return self
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        self.inside_scope = False
+        if exc_type is not None:
+            return False  # re-raise exception
+
+        return True
 
 
 class IfElseBlockGuard(object):

python/paddle/v2/fluid/layers/ops.py

@@ -61,6 +61,10 @@
     'clip_by_norm',
     'softmax',
     'sequence_softmax',
+    'logical_and',
+    'logical_or',
+    'logical_xor',
+    'logical_not',
 ] + __activations__
 
 for _OP in set(__all__):

python/paddle/v2/fluid/tests/test_switch.py

@@ -0,0 +1,64 @@
+#   Copyright (c) 2018 PaddlePaddle Authors. All Rights Reserve.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import unittest
+
+import paddle.v2.fluid.core as core
+import paddle.v2.fluid.layers as layers
+import paddle.v2.fluid.framework as framework
+from paddle.v2.fluid.executor import Executor
+from paddle.v2.fluid.framework import default_startup_program
+
+
+class TestSwitch(unittest.TestCase):
+    def check_switch(self, value):
+        x = layers.fill_constant(shape=[1], dtype='float32', value=value)
+
+        zero_var = layers.fill_constant(shape=[1], dtype='float32', value=0.0)
+        one_var = layers.fill_constant(shape=[1], dtype='float32', value=1.0)
+        two_var = layers.fill_constant(shape=[1], dtype='float32', value=2.0)
+        three_var = layers.fill_constant(shape=[1], dtype='float32', value=3.0)
+
+        result = layers.create_global_var(
+            shape=[1], value=-1.0, dtype='float32', persistable=True)
+
+        with layers.Switch() as switch:
+            with switch.case(layers.less_than(x, zero_var)):
+                layers.assign(zero_var, result)
+            with switch.case(layers.less_than(x, one_var)):
+                layers.assign(one_var, result)
+            with switch.case(layers.less_than(x, two_var)):
+                layers.assign(two_var, result)
+            with switch.default():
+                layers.assign(three_var, result)
+
+        cpu = core.CPUPlace()
+        exe = Executor(cpu)
+        exe.run(default_startup_program())
+
+        out = exe.run(feed={}, fetch_list=[result])[0][0]
+        return out
+
+    def test_switch(self):
+        test_data = {(-0.1, 0), (0.1, 1), (1.1, 2), (2.1, 3)}
+        for x, expected_result in test_data:
+            main_program = framework.Program()
+            startup_program = framework.Program()
+            with framework.program_guard(main_program, startup_program):
+                result = self.check_switch(x)
+                self.assertEqual(result, expected_result)
+
+
+if __name__ == '__main__':
+    unittest.main()