fix api sigmoid_focal_loss to final state (#45207)

python/paddle/nn/functional/loss.py

@@ -2616,7 +2616,6 @@ def sigmoid_focal_loss(logit,
                 "Expected one dimension of normalizer in sigmoid_focal_loss but got {}."
                 .format(normalizer_dims))
 
-    if _non_static_mode():
     if in_dygraph_mode():
         place = _current_expected_place()
         one = _C_ops.final_state_full(logit.shape, float(1.0), logit.dtype,
@@ -2625,14 +2624,46 @@ def sigmoid_focal_loss(logit,
         loss = _C_ops.final_state_sigmoid_cross_entropy_with_logits(
             logit, label, False, -100)
 
+        pred = _C_ops.final_state_sigmoid(logit)
+
+        p_t = _C_ops.final_state_add(
+            _C_ops.final_state_multiply(pred, label),
+            _C_ops.final_state_multiply(_C_ops.final_state_subtract(one, pred),
+                                        _C_ops.final_state_subtract(one,
+                                                                    label)))
+
+        alpha = fluid.dygraph.base.to_variable([alpha], dtype=loss.dtype)
+        alpha_t = _C_ops.final_state_add(
+            _C_ops.final_state_multiply(alpha, label),
+            _C_ops.final_state_multiply(_C_ops.final_state_subtract(one, alpha),
+                                        _C_ops.final_state_subtract(one,
+                                                                    label)))
+        loss = _C_ops.final_state_multiply(alpha_t, loss)
+
+        gamma = fluid.dygraph.base.to_variable([gamma], dtype=loss.dtype)
+        gamma_t = _C_ops.final_state_pow(_C_ops.elementwise_sub(one, p_t),
+                                         gamma)
+        loss = _C_ops.final_state_multiply(gamma_t, loss)
+
+        if normalizer is not None:
+            loss = _C_ops.final_state_divide(loss, normalizer)
+
+        if reduction == "sum":
+            return _C_ops.final_state_sum(loss, [], None, False)
+        elif reduction == "mean":
+            return _C_ops.final_state_mean_all(loss)
+
+        return loss
+
     elif _in_legacy_dygraph():
         one = _varbase_creator(dtype=logit.dtype)
         _C_ops.fill_constant(one, 'value', float(1.0), 'force_cpu', False,
-                                 'dtype', one.dtype, 'str_value', '1.0',
-                                 'shape', logit.shape)
+                             'dtype', one.dtype, 'str_value', '1.0', 'shape',
+                             logit.shape)
         loss = _C_ops.sigmoid_cross_entropy_with_logits(logit, label)
 
         pred = _C_ops.sigmoid(logit)
+
         p_t = _C_ops.elementwise_add(
             _C_ops.elementwise_mul(pred, label),
             _C_ops.elementwise_mul(_C_ops.elementwise_sub(one, pred),
@@ -2656,8 +2687,6 @@ def sigmoid_focal_loss(logit,
         if reduction == "sum":
             return _C_ops.reduce_sum(loss, 'reduce_all', True)
         elif reduction == "mean":
-            if in_dygraph_mode():
-                return _C_ops.final_state_mean_all(loss)
             return _C_ops.mean(loss)
 
         return loss