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58 lines
2.2 KiB
58 lines
2.2 KiB
from paddle.v2.framework import framework as framework
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__all__ = ['append_backward_ops']
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def append_backward_ops(loss, parameter_list=None, no_grad_set=None):
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"""
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Create and add gradient Operators in BlockDesc to compute
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gradients of `loss` for parameters in parameter_list
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:param loss: an variable generated by cost function.
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:type loss: Variable
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:param no_grad_set: variable that should not create gradient
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:type no_grad_set: set
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:param parameter_list: parameters that need to compute gradient and
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update to optimize the lost.
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:type: list
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:return: list of (parameters, gradients) pair.
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:rtype: list[Variable]
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"""
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assert isinstance(loss, framework.Variable)
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if no_grad_set is None:
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program = loss.block.program
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assert isinstance(program, framework.Program)
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no_grad_set = list()
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for block in program.blocks:
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assert isinstance(block, framework.Block)
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for var in block.vars.itervalues():
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assert isinstance(var, framework.Variable)
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if var.stop_gradient:
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no_grad_set.append(var.name)
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no_grad_set = set(no_grad_set)
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param_grad_map = loss.block.program.append_backward(loss, no_grad_set)
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if parameter_list is not None:
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parameters = parameter_list
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else:
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params = loss.block.program.global_block().all_parameters()
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parameters = [param.name for param in params]
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params_and_grads = []
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for param in parameters:
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if param not in param_grad_map:
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raise ValueError("param %s is not in map" % param)
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grad_info = param_grad_map[param]
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grad_block = loss.block.program.block(grad_info[1])
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if not grad_block.has_var(grad_info[0]):
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raise ValueError("grad block[{0}] did not have grad var {1}".format(
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grad_info[1], grad_info[0]))
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# Get the param var from the global block
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param_var = loss.block.program.global_block().var(param)
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grad_var = grad_block.var(grad_info[0])
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if loss.block.has_var(grad_info[0]):
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params_and_grads.append((param_var, grad_var))
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else:
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params_and_grads.append((param_var, None))
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return params_and_grads
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