smth
September 20, 2017, 4:27am
2
These two posts will help get through the code structure and build system:
http://pytorch.org/2017/05/11/Internals.html
http://pytorch.org/2017/06/27/Internals2.html
It doesn’t touch the autograd system though.
Here’s a pointer to very old source code, where all the logic was in Python, in the early days of PyTorch. The logic is largely the same still, but moved into C.
from collections import Counter
class ExecutionEngine(object):
def __init__(self):
pass
def _compute_dependencies(self, function):
dependencies = {}
seen = {function}
queue = [function]
while len(queue) > 0:
fn = queue.pop()
for prev_fn, arg_id in fn.previous_functions:
if prev_fn not in dependencies:
dependencies[prev_fn] = [Counter() for _ in prev_fn.output_ids]
output_idx = prev_fn.output_ids[arg_id]
dependencies[prev_fn][output_idx][fn] += 1
if prev_fn not in seen:
queue.append(prev_fn)
seen.add(prev_fn)
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from collections import OrderedDict
from .variable import Variable
class Function(object):
def __init__(self):
self.previous_functions = None
self.output_ids = None
self.needs_input_grad = None
self.backward_hooks = OrderedDict()
def __call__(self, *input):
return self._do_forward(*input)
def _do_forward(self, *input):
unpacked_input = tuple(arg.data for arg in input)
raw_output = self.forward(*unpacked_input)
if not isinstance(raw_output, tuple):
raw_output = (raw_output,)
self.needs_input_grad = tuple(arg.creator.requires_grad for arg in input)
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