!10424 Compute weighted loss

From: @xuguoyang5566
Reviewed-by: @wuxuejian
Signed-off-by:

mindspore/nn/loss/loss.py

@@ -29,7 +29,7 @@ class _Loss(Cell):
     """
     Base class for other losses.
     """
-    def __init__(self, reduction='mean'):
+    def __init__(self, reduction='mean', weights=1.0):
         super(_Loss, self).__init__()
         if reduction is None:
             reduction = 'none'
@@ -46,6 +46,11 @@ class _Loss(Cell):
 
         self.reduce_mean = _selected_ops.ReduceMean()
         self.reduce_sum = P.ReduceSum()
+        self.mul = P.Mul()
+        if isinstance(weights, int):
+            self.weights = float(weights)
+        else:
+            self.weights = weights
 
     def get_axis(self, x):
         shape = F.shape(x)
@@ -54,6 +59,8 @@ class _Loss(Cell):
         return perm
 
     def get_loss(self, x):
+        if self.weights != 1.0:
+            x = self.mul(self.weights, x)
         if self.reduce and self.average:
             x = self.reduce_mean(x, self.get_axis(x))
         if self.reduce and not self.average:

mindspore/nn/optim/rmsprop.py

@@ -131,7 +131,7 @@ class RMSProp(Optimizer):
         Tensor[bool], the value is True.
 
     Supported Platforms:
-        ``Ascend`` ``GPU``
+        ``Ascend`` ``GPU`` ``CPU``
 
     Examples:
         >>> net = Net()

tests/st/ops/gpu/test_loss.py

@@ -0,0 +1,51 @@
+# Copyright 2020 Huawei Technologies Co., Ltd
+#
+# 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.
+# ============================================================================
+""" test loss """
+import numpy as np
+
+from mindspore import Tensor
+from mindspore.ops import operations as P
+from mindspore.nn.loss.loss import _Loss
+
+class WeightedLoss(_Loss):
+    def __init__(self, reduction='mean', weights=1.0):
+        super(WeightedLoss, self).__init__(reduction, weights)
+        self.abs = P.Abs()
+
+    def construct(self, base, target):
+        x = self.abs(base - target)
+        return self.get_loss(x)
+
+def test_WeightedLoss():
+    loss = WeightedLoss()
+    input_data = Tensor(np.array([[1, 2, 3], [2, 3, 4]]).astype(np.float32))
+    target_data = Tensor(np.array([[0, 2, 5], [3, 1, 1]]).astype(np.float32))
+    output_data = loss(input_data, target_data)
+
+    error_range = np.ones(shape=output_data.shape) * 10e-6
+    loss.weights = 1.0
+    test_output = loss(input_data, target_data)
+    diff = test_output - output_data * loss.weights
+    assert np.all(abs(diff.asnumpy()) < error_range)
+
+    loss.weights = 2.0
+    test_output = loss(input_data, target_data)
+    diff = test_output - output_data * loss.weights
+    assert np.all(abs(diff.asnumpy()) < error_range)
+
+    loss.weights = 3
+    test_output = loss(input_data, target_data)
+    diff = test_output - output_data * loss.weights
+    assert np.all(abs(diff.asnumpy()) < error_range)