Improvements to apex.mlp (#804)

* update fused bias relu backward kernel

* adding support for not require first layer dgrad

* fix bug: wrong layer in requires grad

* add infrastructure for optional bias and activation, currently only support no bias and no relu

* make bias and relu optional separately

* add sigmoid activation option

apex/mlp/mlp.py

@@ -7,17 +7,19 @@
 
 class MlpFunction(torch.autograd.Function):
     @staticmethod
-    def forward(ctx, *args):
-        output = mlp_cuda.forward(args)
+    def forward(ctx, bias, activation, *args):
+        output = mlp_cuda.forward(bias, activation, args)
         ctx.save_for_backward(*args)
         ctx.outputs = output
+        ctx.bias = bias
+        ctx.activation = activation
         return output[0]
 
     @staticmethod
     def backward(ctx, grad_o):
-        grads = mlp_cuda.backward(grad_o, ctx.outputs, ctx.saved_tensors)
+        grads = mlp_cuda.backward(ctx.bias, ctx.activation, grad_o, ctx.outputs, ctx.saved_tensors)
         del ctx.outputs
-        return tuple(grads)
+        return (None, None, *grads)
 
 mlp_function = amp.half_function(MlpFunction.apply)
 
@@ -29,27 +31,33 @@ class MLP(torch.nn.Module):
         bias (bool): Default True:
         relu (bool): Default True
     """
-    def __init__(self, mlp_sizes, bias=True, relu=True):
-        if not (bias and relu):
-            raise TypeError("bias and relu must be both true.")
+    def __init__(self, mlp_sizes, bias=True, activation='relu'):
         super(MLP, self).__init__()
         self.num_layers = len(mlp_sizes) - 1
         self.mlp_sizes = copy(mlp_sizes)
-        self.bias = bias
-        self.relu= relu
+        self.bias = 1 if bias else 0
+
+        if activation is 'none':
+            self.activation = 0
+        elif activation is 'relu':
+            self.activation = 1
+        elif activation is 'sigmoid':
+            self.activation = 2
+        else:
+            raise TypeError("activation must be relu or none.")
 
-        # ignoring bias = False now
         self.weights = []
         self.biases = []
         for i in range(self.num_layers):
             w = torch.nn.Parameter(torch.empty(mlp_sizes[i+1], mlp_sizes[i]))
             self.weights.append(w)
             name = 'weight_{}'.format(i)
             setattr(self, name, w)
-            b = torch.nn.Parameter(torch.empty(mlp_sizes[i+1]))
-            self.biases.append(b)
-            name = 'bias_{}'.format(i)
-            setattr(self, name, b)
+            if self.bias:
+                b = torch.nn.Parameter(torch.empty(mlp_sizes[i+1]))
+                self.biases.append(b)
+                name = 'bias_{}'.format(i)
+                setattr(self, name, b)
 
         self.reset_parameters()
 
@@ -58,13 +66,14 @@ def reset_parameters(self):
             dimsum = weight.size(0) + weight.size(1)
             std = math.sqrt(2. / float(dimsum))
             nn.init.normal_(weight, 0., std)
-        for bias in self.biases:
-            std = math.sqrt(1. / float(bias.size(0)))
-            nn.init.normal_(bias, 0., std)
+        if self.bias:
+            for bias in self.biases:
+                std = math.sqrt(1. / float(bias.size(0)))
+                nn.init.normal_(bias, 0., std)
 
     def forward(self, input):
-        return mlp_function(input, *self.weights, *self.biases)
+        return mlp_function(self.bias, self.activation, input, *self.weights, *self.biases)
 
     def extra_repr(self):
-        s = F"MLP sizes: {self.mlp_sizes}, Bias={self.bias}, ReLU={self.relu}"
+        s = F"MLP sizes: {self.mlp_sizes}, Bias={self.bias}, activation={self.activation}"
         return s

csrc/mlp.cpp

@@ -19,7 +19,9 @@ int mlp_fp(
     int* output_features,
     T** BPtr,
     T* Y,
-    T* reserved_space);
+    T* reserved_space,
+    int use_bias,
+    int activation);
 
 template <typename T>
 int mlp_bp(
@@ -35,11 +37,18 @@ int mlp_bp(
     T* work_space,
     T* dX,
     T** dwPtr,
-    T** dbPtr);
+    T** dbPtr,
+    bool requires_grad,
+    int use_bias,
+    int activation);
+
+std::vector<at::Tensor> mlp_forward(int use_bias, int activation, std::vector<at::Tensor> inputs) {
 
-std::vector<at::Tensor> mlp_forward(std::vector<at::Tensor> inputs) {
-  // inputs contains (input, weights, biases)
-  auto num_layers = (inputs.size() - 1) / 2;
+  auto num_layers = inputs.size() - 1;
+  if (use_bias) {
+    // inputs contains (input, weights, biases)
+    num_layers /= 2;
+  }
   auto batch_size = inputs[0].size(0);
   auto input_features = inputs[0].size(1);
 
@@ -60,7 +69,9 @@ std::vector<at::Tensor> mlp_forward(std::vector<at::Tensor> inputs) {
     std::vector<scalar_t*> b_ptr;
     for (int i = 0; i < num_layers; i++) {
       w_ptr.push_back(inputs[i + 1].data_ptr<scalar_t>());
-      b_ptr.push_back(inputs[i + 1 + num_layers].data_ptr<scalar_t>());
+      if (use_bias) {
+        b_ptr.push_back(inputs[i + 1 + num_layers].data_ptr<scalar_t>());
+      }
     }
     auto result = mlp_fp<scalar_t>(
         inputs[0].data_ptr<scalar_t>(),
@@ -71,37 +82,48 @@ std::vector<at::Tensor> mlp_forward(std::vector<at::Tensor> inputs) {
         output_features.data(),
         b_ptr.data(),
         out.data_ptr<scalar_t>(),
-        reserved_space.data_ptr<scalar_t>());
+        reserved_space.data_ptr<scalar_t>(),
+        use_bias,
+        activation);
   });
 
   return {out, reserved_space};
 }
 
 std::vector<at::Tensor> mlp_backward(
-    at::Tensor grad_o,
-    std::vector<at::Tensor> fprop_outputs,
-    std::vector<at::Tensor> inputs) {
-  // same code to get sizes and W pointers
-  auto num_layers = (inputs.size() - 1) / 2;
+  int use_bias,
+  int activation,
+  at::Tensor grad_o,
+  std::vector<at::Tensor> fprop_outputs,
+  std::vector<at::Tensor> inputs) {
+
+  auto num_layers = inputs.size() - 1;
+  if (use_bias) {
+    // inputs contains (input, weights, biases)
+    num_layers /= 2;
+  }
+
   auto batch_size = inputs[0].size(0);
   auto input_features = inputs[0].size(1);
 
+  // TODO: not creating empty tensor for it?
+  bool requires_grad = inputs[0].requires_grad();
+
   std::vector<int> output_features;
   for (int i = 0; i < num_layers; i++) {
     output_features.push_back(inputs[i + 1].size(0));
   }
   // create outputs, length of inputs
+  // TODO: not create bias if not needed
   std::vector<at::Tensor> outputs;
   for (int i = 0; i < inputs.size(); i++) {
     outputs.push_back(at::empty(inputs[i].sizes(), inputs[i].type()));  // clone for testing now
   }
 
-  AT_DISPATCH_FLOATING_TYPES_AND_HALF(inputs[0].type(), "mlp_forward", [&] {
+  AT_DISPATCH_FLOATING_TYPES_AND_HALF(inputs[0].type(), "mlp_backward", [&] {
     std::vector<scalar_t*> w_ptr;
-    std::vector<scalar_t*> b_ptr;
     for (int i = 0; i < num_layers; i++) {
       w_ptr.push_back(inputs[i + 1].data_ptr<scalar_t>());
-      b_ptr.push_back(inputs[i + 1 + num_layers].data_ptr<scalar_t>());
     }
     std::vector<scalar_t*> outputs_ptr;
     for (int i = 0; i < inputs.size(); i++) {
@@ -127,7 +149,10 @@ std::vector<at::Tensor> mlp_backward(
         work_space.data_ptr<scalar_t>(),
         outputs_ptr[0],
         outputs_ptr.data() + 1,
-        outputs_ptr.data() + 1 + num_layers);
+        outputs_ptr.data() + 1 + num_layers,
+        requires_grad,
+        use_bias,
+        activation);
   });
 
   return outputs;