[ Dy2static ] infer_program may be incorrect in amp mode. (#44487)

* fix the outputs of net is x,x

* add unittest for duplicate output

* fix

* fix _infer_program use the original program not the amp program.

* get _***program_id back and avoid duplicate cache
ing

* fix

python/paddle/fluid/dygraph/dygraph_to_static/partial_program.py

@@ -243,6 +243,14 @@ class PartialProgramLayer:
     def _infer_program_id(self):
         return _hash_with_id(self._infer_program, self)
 
+    @LazyInitialized
+    def _infer_pure_fp16_program_id(self):
+        return _hash_with_id(self._infer_pure_fp16_program, self)
+
+    @LazyInitialized
+    def _infer_amp_program_id(self):
+        return _hash_with_id(self._infer_amp_program, self)
+
     @LazyInitialized
     def _train_program_id(self):
         program_id = _hash_with_id(self._train_program, self)
@@ -341,7 +349,7 @@ class PartialProgramLayer:
         elif _in_pure_fp16_guard():
             infer_program = self._infer_pure_fp16_program
         else:
-            infer_program = self._infer_program
+            infer_program = self.infer_program
         return infer_program.desc.block(0).op_size()
 
     def __call__(self, inputs):
@@ -380,14 +388,9 @@ class PartialProgramLayer:
     @property
     def program(self):
         if self.training:
-            if _in_amp_guard():
-                return self._train_amp_program
-            elif _in_pure_fp16_guard():
-                return self._train_pure_fp16_program
-            else:
-                return self._train_program
+            return self.train_program
         else:
-            return self._infer_program
+            return self.infer_program
 
     @property
     def program_id(self):
@@ -399,7 +402,30 @@ class PartialProgramLayer:
             else:
                 return self._train_program_id
         else:
-            return self._infer_program_id
+            if _in_amp_guard():
+                return self._infer_amp_program_id
+            elif _in_pure_fp16_guard():
+                return self._infer_pure_fp16_program_id
+            else:
+                return self._infer_program_id
+
+    @property
+    def train_program(self):
+        if _in_amp_guard():
+            return self._train_amp_program
+        elif _in_pure_fp16_guard():
+            return self._train_pure_fp16_program
+        else:
+            return self._train_program
+
+    @property
+    def infer_program(self):
+        if _in_amp_guard():
+            return self._infer_amp_program
+        elif _in_pure_fp16_guard():
+            return self._infer_pure_fp16_program
+        else:
+            return self._infer_program
 
     def _prepare(self, inputs):
         """