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体验新版 GitCode,发现更多精彩内容 >>
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bb0427ad
编写于
12月 28, 2017
作者:
F
fengjiayi
浏览文件
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电子邮件补丁
差异文件
Add comments for functions in backward.py
上级
18311767
变更
1
隐藏空白更改
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并排
Showing
1 changed file
with
67 addition
and
10 deletion
+67
-10
python/paddle/v2/fluid/backward.py
python/paddle/v2/fluid/backward.py
+67
-10
未找到文件。
python/paddle/v2/fluid/backward.py
浏览文件 @
bb0427ad
...
...
@@ -5,14 +5,17 @@ import collections
__all__
=
[
'append_backward'
]
def
_rename_arg_
(
op_desc_list
,
old_name
,
new_name
,
begin_idx
=
None
,
end_idx
=
None
):
def
_rename_arg_
(
op_descs
,
old_name
,
new_name
,
begin_idx
=
None
,
end_idx
=
None
):
"""
Traverse all ops in op_descs[begin_idx : end_idx],
if any op has inputs/outputs named "old_name", rename it as 'new_name'
"""
if
begin_idx
is
None
:
begin_idx
=
0
if
end_idx
is
None
:
end_idx
=
len
(
op_desc
_list
)
end_idx
=
len
(
op_desc
s
)
for
i
in
range
(
begin_idx
,
end_idx
):
op_desc
=
op_desc
_list
[
i
]
op_desc
=
op_desc
s
[
i
]
if
isinstance
(
op_desc
,
tuple
):
op_desc
=
op_desc
[
0
]
op_desc
.
rename_input
(
old_name
,
new_name
)
...
...
@@ -20,6 +23,9 @@ def _rename_arg_(op_desc_list, old_name, new_name, begin_idx=None,
def
_create_op_desc_
(
op_type
,
inputs
,
outputs
,
attrs
):
"""
Create a C++ OpDesc object with specified inputs, outputs and attributes.
"""
op_desc
=
core
.
OpDesc
()
op_desc
.
set_type
(
op_type
)
for
para
,
args
in
inputs
.
iteritems
():
...
...
@@ -34,9 +40,12 @@ def _create_op_desc_(op_type, inputs, outputs, attrs):
return
op_desc
def
_infer_var_data_type_
(
var_name
,
block
):
grad_var
=
block
.
desc
.
find_var
(
var_name
.
encode
(
"ascii"
))
fwd_name
=
_strip_grad_suffix_
(
var_name
.
encode
(
"ascii"
))
def
_infer_var_data_type_
(
grad_var_name
,
block
):
"""
Infer the data type of given grad variable
"""
grad_var
=
block
.
desc
.
find_var
(
grad_var_name
.
encode
(
"ascii"
))
fwd_name
=
_strip_grad_suffix_
(
grad_var_name
.
encode
(
"ascii"
))
if
block
.
desc
.
has_var_recursive
(
fwd_name
):
fwd_var
=
block
.
desc
.
find_var_recursive
(
fwd_name
.
encode
(
"ascii"
))
grad_var
.
set_dtype
(
fwd_var
.
dtype
())
...
...
@@ -45,6 +54,9 @@ def _infer_var_data_type_(var_name, block):
def
_all_in_set_
(
cands
,
s
):
"""
Test if all elements of 'cands' are in set 's'
"""
for
c
in
cands
:
if
not
c
in
s
:
return
False
...
...
@@ -52,18 +64,29 @@ def _all_in_set_(cands, s):
def
_strip_grad_suffix_
(
name
):
"""
Strip the grad suffix from the given varibale name
e.g. x@GRAD ==> x
y@GRAD@RENAME@1 ==> y
"""
pos
=
name
.
find
(
core
.
grad_var_suffix
())
return
name
[:
pos
]
if
pos
!=
-
1
else
name
def
_append_grad_suffix_
(
name
):
"""
Append grad suffix to the given variable name
e.g. x ==> x@GRAD
"""
return
name
+
core
.
grad_var_suffix
()
def
_addup_repetitive_outputs_
(
op_descs
):
# In backward part, an variable my be the output of more than one ops.
# In this case, the variable should be the accumulation of all the outputs.
# We adopt adding `sum_op`s to implement the accumulate.
"""
In backward part, an variable may be the output of more than one ops.
In this case, the variable should be the accumulation of all the outputs.
`sum_op`s are added to implement the accumulate.
"""
pending_sum_ops
=
[]
var_rename_count
=
collections
.
defaultdict
(
int
)
renamed_vars
=
collections
.
defaultdict
(
list
)
...
...
@@ -109,6 +132,12 @@ def _addup_repetitive_outputs_(op_descs):
def
_remove_no_grad_branch_
(
op_descs
,
no_grad_set
):
"""
Remove unnecessary grad ops
A grad op can be removed in two cases:
1. all outputs of the grad op are in 'no_grad_set'
2. (TODO) all grad inputs of the grad op are in 'no_grad_set'
"""
# Remove ops whose outputs are all in no_grad_dict
op_descs
=
filter
(
lambda
op_desc
:
not
_all_in_set_
(
op_desc
.
output_arg_names
(),
no_grad_set
),
...
...
@@ -133,6 +162,20 @@ def _append_backward_ops_(target,
no_grad_dict
,
grad_to_var
,
callback
=
None
):
"""
Create all grad ops, and insert them into given block
Args:
target(Variable): the target variable of forward pass
block(Block): the block where forward ops are
target_block(Block): the block which is going to hold new generated grad ops
no_grad_dict(dict):
key(int) block index
val(set) a set of varibale names. These varibales have no gradient
grad_to_var(dict)(output argument):
key(str): grad variable name
val(str): corresponding forward variable name
"""
grad_op_descs
=
[]
program
=
block
.
program
for
op
in
reversed
(
block
.
ops
):
...
...
@@ -170,6 +213,20 @@ def _append_backward_ops_(target,
def
_append_backward_vars_
(
block
,
start_op_idx
,
grad_to_var
,
grad_info_map
):
"""
Create new variables required by backward pass.
Args:
block(Block): the block where new variables will be created
start_op_idx(int): Only variables required by ops in block.ops[start_op_idx : ] will be created
grad_to_var(dict):
key(str): grad variable name
val(str): corresponding forward variable name
In most cases, this dict is generated by _append_backward_ops_()
grad_info_map(dict)(output argument):
key(str): forward variable name
val(tuple): a tuple of (str, int), str is the corresponding grad name, int is the block index
"""
for
op_idx
in
range
(
start_op_idx
,
block
.
desc
.
op_size
()):
op_desc
=
block
.
desc
.
op
(
op_idx
)
if
op_desc
.
has_attr
(
"sub_block"
):
...
...
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