Merge pull request #426 from brainpy/doc

fix autograd bugs

brainpy/_src/math/object_transform/autograd.py

@@ -224,13 +224,17 @@ def __call__(self, *args, **kwargs):
               )
           cache_stack(self.target, stack)
 
-      self._dyn_vars = stack
-      self._dyn_vars.remove_var_by_id(*[id(v) for v in self._grad_vars])
-      self._eval_dyn_vars = True
+        self._dyn_vars = stack
+        self._dyn_vars.remove_var_by_id(*[id(v) for v in self._grad_vars])
+        self._eval_dyn_vars = True
 
-      # if not the outermost transformation
-      if current_transform_number():
-        return self._return(rets)
+        # if not the outermost transformation
+        if current_transform_number():
+          return self._return(rets)
+      else:
+        self._dyn_vars = stack
+        self._dyn_vars.remove_var_by_id(*[id(v) for v in self._grad_vars])
+        self._eval_dyn_vars = True
 
     rets = self._transform(
       [v.value for v in self._grad_vars],  # variables for gradients

brainpy/_src/math/object_transform/tests/test_autograd.py

@@ -1149,4 +1149,25 @@ def test_debug_correctness2(self):
     self.assertTrue(bm.allclose(r1[1], r2[1]))
     self.assertTrue(bm.allclose(r1[2], r2[2]))
 
+  def test_cache1(self):
+      file = tempfile.TemporaryFile(mode='w+')
+
+      def f(a, b):
+        print('compiling f ...', file=file)
+        return a + b
+
+      grad1 = bm.grad(f)(1., 2.)  # call "f" twice, one for Variable finding, one for compiling
+      grad2 = bm.vector_grad(f)(1., 2.)  # call "f" once for compiling
+
+      file.seek(0)
+      print(file.read().strip())
+
+      expect_res = '''
+compiling f ...
+compiling f ...
+compiling f ...
+      '''
+      file.seek(0)
+      self.assertTrue(file.read().strip() == expect_res.strip())
+