add index_add_ doc

python/jittor/misc.py

@@ -14,6 +14,22 @@ import math
 from collections.abc import Sequence,Iterable
 
 def index_add_(x, dim, index, tensor):
+    """ Take out each index subscript vector of the dim dimension and add the corresponding tensor variable.
+    
+    Example:
+
+        x = jt.ones((5,3))
+        tensor = jt.array([[1, 2, 3], [4, 5, 6], [7, 8, 9]])
+        index = jt.array([0,4,2])
+        x.index_add_(0, index, tensor)
+        print(x)
+
+        >>> jt.Var([[  2.,   3.,   4.],
+        [  1.,   1.,   1.],
+        [  8.,   9.,  10.],
+        [  1.,   1.,   1.],
+        [  5.,   6.,   7.]])
+    """
     assert len(index.shape) == 1
     assert tensor.shape[0] == index.shape[0]
     x[(slice(None,),)*dim+(index,)] += tensor