# Copyright (c) 2019 PaddlePaddle Authors. All Rights Reserved. # # Licensed under the Apache License, Version 2.0 (the "License"); # you may not use this file except in compliance with the License. # You may obtain a copy of the License at # # http://www.apache.org/licenses/LICENSE-2.0 # # Unless required by applicable law or agreed to in writing, software # distributed under the License is distributed on an "AS IS" BASIS, # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. # See the License for the specific language governing permissions and # limitations under the License. from __future__ import print_function import numpy as np import six import logging from collections import defaultdict import paddle from paddle.fluid.distribute_lookup_table import find_distributed_lookup_table from paddle.fluid.framework import Program, Variable, name_scope, default_main_program, default_startup_program, device_guard from ..fluid import framework from ..fluid import layers from ..fluid import unique_name from ..fluid.backward import append_backward, _some_in_set_, _append_grad_suffix_, _get_no_grad_set_name from ..fluid.clip import GradientClipBase, GradientClipByNorm, error_clip_callback, append_gradient_clip_ops from ..fluid.framework import program_guard from ..fluid.initializer import Constant from ..fluid.layer_helper import LayerHelper from ..fluid.layers import ops from ..fluid.regularizer import append_regularization_ops from ..fluid.dygraph import base as imperative_base from ..fluid.dygraph import no_grad from paddle.fluid import core from paddle.fluid.layers import tensor from functools import reduce from ..fluid.wrapped_decorator import signature_safe_contextmanager from .. import compat as cpt from .lr import LRScheduler class Optimizer(object): r"""Optimizer Base class. Define the common interface of an optimizer. User should not use this class directly, but need to use one of it's implementation. Args: learning_rate (float|LRScheduler): The learning rate used to update ``Parameter``. It can be a float value or any subclass of ``LRScheduler`` . parameters (list, optional): List of ``Tensor`` names to update to minimize ``loss``. \ This parameter is required in dygraph mode. \ The default value is None in static mode, at this time all parameters will be updated. weight_decay (float|WeightDecayRegularizer, optional): The strategy of regularization. \ It canbe a float value as coeff of L2 regularization or \ :ref:`api_fluid_regularizer_L1Decay`, :ref:`api_fluid_regularizer_L2Decay`. If a parameter has set regularizer using :ref:`api_fluid_ParamAttr` already, \ the regularization setting here in optimizer will be ignored for this parameter. \ Otherwise, the regularization setting here in optimizer will take effect. \ Default None, meaning there is no regularization. grad_clip (GradientClipBase, optional): Gradient cliping strategy, it's an instance of \ some derived class of ``GradientClipBase`` . There are three cliping strategies \ ( :ref:`api_fluid_clip_GradientClipByGlobalNorm` , :ref:`api_fluid_clip_GradientClipByNorm` , \ :ref:`api_fluid_clip_GradientClipByValue` ). Default None, meaning there is no gradient clipping. name (str, optional): Normally there is no need for user to set this property. For more information, please refer to :ref:`api_guide_Name`. The default value is None. Returns: Base class for optimizer. Examples: .. code-block:: python #Take the subclass adam as an example import paddle linear = paddle.nn.Linear(10, 10) inp = paddle.uniform(shape=[10, 10], min=-0.1, max=0.1) out = linear(inp) loss = paddle.mean(out) adam = paddle.optimizer.Adam(learning_rate=0.1, parameters=linear.parameters()) out.backward() adam.step() adam.clear_grad() """ @imperative_base.no_grad def __init__(self, learning_rate, parameters=None, weight_decay=None, grad_clip=None, name=None): if parameters is not None: # paddle.Tensor is also iterable, so here we don't check whether # the input is iterable, if the input is paddle.Tensor, the # list(paddle.Tensor) will be a error value if isinstance(parameters, paddle.Tensor): raise TypeError( "`parameters` argument given to the optimizer should be " "an iterable of paddle Tensors, but got argument type is `{}`.". format(type(parameters))) self._parameter_list = list(parameters) else: self._parameter_list = None self._name = name if framework.in_dygraph_mode(): if self._parameter_list is None: raise AttributeError( "parameters argument given to the Optimizer should not be None in dygraph mode." ) if weight_decay is not None: for param in self._parameter_list: if hasattr(param, 'regularizer') and param.regularizer is not None: logging.info( "If regularizer of a Parameter has been set by 'paddle.ParamAttr' or 'static.WeightNormParamAttr' already. " "The weight_decay[%s] in Optimizer will not take effect, and it will only be applied to other Parameters!" % weight_decay.__str__()) break if not isinstance(learning_rate, (float, LRScheduler)): raise TypeError( "learning rate should be float or LRScheduler, got %s here" % type(learning_rate)) if grad_clip is not None: if not isinstance(grad_clip, GradientClipBase): raise TypeError( "'grad_clip' should be an instance of GradientClipBase's derived class" ) if isinstance(weight_decay, float): from ..fluid.regularizer import L2Decay self.regularization = L2Decay(weight_decay) else: self.regularization = weight_decay self._grad_clip = grad_clip self._learning_rate = learning_rate self._dtype = None # Infer the dtype form parameter if self._parameter_list: self._dtype = self._parameter_list[0].dtype # each program should have a independent learning rate # program -> tensor(learning_rate) self._learning_rate_map = dict() # Dictionary of accumulators. Some optimizer subclasses need to # allocate and manage extra tensors associated with the parameters # to train. These tensors are called accumulators. # {accum_name : { paramter_name : accumulator_for_parameter, ...}, ...} self._accumulators = defaultdict(lambda: dict()) self.helper = None self._opti_name_list = [] self._accumulators_holder = {} self._param_device_map = dict() self.clear_gradients = self.clear_grad @framework.dygraph_only def state_dict(self): ''' Get state dict information from optimizer. It contain all the tensor used by optimizer. For Adam optimizer, contains beta1, beta2, momentum etc. If LRScheduler have been used, global_step will be include in state dict. If the optimizer never be called(minimize function), the state_dict is empty. Args: None Returns: state_dict(dict) : dict contains all the Tensor used by optimizer Examples: .. code-block:: python import paddle emb = paddle.nn.Embedding(10, 10) adam = paddle.optimizer.Adam(0.001, parameters=emb.parameters()) state_dict = adam.state_dict() ''' state_dict = {} for k, v in self._accumulators.items(): for para_name, var_tmp in v.items(): state_dict[var_tmp.name] = var_tmp # global step if use lr decay if isinstance(self._learning_rate, LRScheduler): state_dict["LR_Scheduler"] = self._learning_rate.state_dict() return state_dict @framework.dygraph_only def set_state_dict(self, state_dict): ''' Load optimizer state dict. For Adam optimizer, contains beta1, beta2, momentum etc. If LRScheduler have been used, global_step will be changed. Args: state_dict(dict) : Dict contains all the Tensor needed by optimizer Return: None Examples: .. code-block:: python import paddle emb = paddle.nn.Embedding(10, 10) layer_state_dict = emb.state_dict() paddle.save(layer_state_dict, "emb.pdparams") scheduler = paddle.optimizer.lr.NoamDecay( d_model=0.01, warmup_steps=100, verbose=True) adam = paddle.optimizer.Adam( learning_rate=scheduler, parameters=emb.parameters()) opt_state_dict = adam.state_dict() paddle.save(opt_state_dict, "adam.pdopt") opti_state_dict = paddle.load("adam.pdopt") adam.set_state_dict(opti_state_dict) ''' if isinstance(self._learning_rate, LRScheduler): self._learning_rate.set_dict(state_dict["LR_Scheduler"]) if isinstance(self._learning_rate, LRScheduler): self._learning_rate.set_state_dict(state_dict["LR_Scheduler"]) self._accumulators_holder = state_dict for k, v in self._accumulators.items(): for para_name, var_tmp in v.items(): assert var_tmp.name in state_dict, \ "optimizer Tensor {} not found".format( var_tmp.name ) var = var_tmp.value() tensor = var.get_tensor() model_np = np.array(tensor) load_para = state_dict[var_tmp.name] if isinstance(load_para, Variable): load_para_np = load_para.numpy() elif isinstance(load_para, core.VarBase): load_para_np = load_para.numpy() elif isinstance(load_para, np.ndarray): load_para_np = load_para else: raise RuntimeError("State dict type {} not supprt".format( str(type(load_para)))) assert model_np.shape == load_para_np.shape, \ "Parameter shape not match, Dygraph Parameter [ {} ] need tensor with shape {} but load tensor with shape {}".format( item.name, model_np.shape, load_para_np.shape) assert model_np.dtype == load_para_np.dtype, \ "Parameter dtype not match, Dygraph Parameter [ {} ] need tensor with dtype {} but load tensor with dtype {}".format( item.name, model_np.dtype, load_para_np.dtype) tensor.set(load_para_np, framework._current_expected_place()) def get_opti_var_name_list(self): return self._opti_name_list def _create_global_learning_rate(self): if isinstance(self._learning_rate, LRScheduler): lr_var = self._global_learning_rate() # only create global lr_var once if not isinstance(lr_var, framework.Variable): lr_name = unique_name.generate('learning_rate') self._learning_rate._var_name = lr_name lr_var = self.helper.create_global_variable( name=lr_name, shape=[1], persistable=True, stop_gradient=True, dtype=paddle.get_default_dtype() if self._dtype is None else self._dtype) main_prog = framework.default_main_program() main_prog.lr_sheduler = self._learning_rate main_prog.lr_var = lr_var self._learning_rate_map[framework.default_main_program( )] = lr_var lr_value = float(self._learning_rate()) self.helper.set_variable_initializer( lr_var, initializer=Constant(value=lr_value)) elif isinstance(self._learning_rate, float): # only create global lr_var once lr = self._global_learning_rate() if isinstance(lr, framework.Variable): return else: self._learning_rate_map[framework.default_main_program( )] = layers.create_global_var( name=unique_name.generate("learning_rate"), shape=[1], value=float(self._learning_rate), dtype=paddle.get_default_dtype() if self._dtype is None else self._dtype, persistable=True) @framework.dygraph_only def set_lr(self, value): """ :api_attr: imperative Set the value of the learning rate manually in the optimizer. If the optimizer use LRScheduler, this API cannot be invoked, because it will lead to conflict. Args: value (float): the value of learning rate Returns: None Examples: .. code-block:: python import paddle linear = paddle.nn.Linear(10, 10) adam = paddle.optimizer.Adam(0.1, parameters=linear.parameters()) # set learning rate manually by python float value lr_list = [0.2, 0.3, 0.4, 0.5, 0.6] for i in range(5): adam.set_lr(lr_list[i]) lr = adam.get_lr() print("current lr is {}".format(lr)) # Print: # current lr is 0.2 # current lr is 0.3 # current lr is 0.4 # current lr is 0.5 # current lr is 0.6 """ if not isinstance(value, (int, float)): raise TypeError( "The type of 'value' in optimizer.set_lr must be float, but received %s." % (type(value))) if isinstance(self._learning_rate, LRScheduler): raise RuntimeError( "optimizer's learning rate can't be LRScheduler when invoke this API, because this will lead to conflict." ) self._learning_rate = float(value) current_lr = self._global_learning_rate() if current_lr is not None: global_block = framework.default_main_program().global_block() global_block.append_op( type='fill_constant', outputs={'Out': [current_lr]}, attrs={ 'dtype': current_lr.dtype, 'shape': list(current_lr.shape), 'value': float(value) }, stop_gradient=True) def get_lr(self): """ Get current learning rate of optimizer. If 'LRScheduler' is not used, the return value is all the same. If 'LRScheduler' is used, the return value is the current scheduled learing rete. Returns: float: The current learning rate of optimizer. Examples: .. code-block:: python # train on default dynamic graph mode import paddle import numpy as np emb = paddle.nn.Embedding(10, 3) ## example1: LRScheduler is not used, return the same value is all the same adam = paddle.optimizer.Adam(0.01, parameters = emb.parameters()) for batch in range(10): input = paddle.randint(low=0, high=5, shape=[5]) out = emb(input) out.backward() print("Learning rate of step{}: {}".format(batch, adam.get_lr())) # 0.01 adam.step() ## example2: StepDecay is used, return the scheduled learning rate scheduler = paddle.optimizer.lr.StepDecay(learning_rate=0.5, step_size=2, gamma=0.1) adam = paddle.optimizer.Adam(scheduler, parameters = emb.parameters()) for batch in range(10): input = paddle.randint(low=0, high=5, shape=[5]) out = emb(input) out.backward() print("Learning rate of step{}: {}".format(batch, adam.get_lr())) # 0.5->0.05... adam.step() scheduler.step() # train on static graph mode paddle.enable_static() main_prog = paddle.static.Program() start_prog = paddle.static.Program() with paddle.static.program_guard(main_prog, start_prog): x = paddle.static.data(name='x', shape=[None, 10]) z = paddle.static.nn.fc(x, 100) loss = paddle.mean(z) scheduler = paddle.optimizer.lr.StepDecay(learning_rate=0.5, step_size=2, gamma=0.1) adam = paddle.optimizer.Adam(learning_rate=scheduler) adam.minimize(loss) exe = paddle.static.Executor() exe.run(start_prog) for batch in range(10): print("Learning rate of step{}: {}", adam.get_lr()) # 0.5->0.05->0.005... out = exe.run(main_prog, feed={'x': np.random.randn(3, 10).astype('float32')}) scheduler.step() """ if isinstance(self._learning_rate, float): return self._learning_rate else: return self._learning_rate() def _global_learning_rate(self, program=None): """ get global decayed learning rate :return: """ if program is None: program = framework.default_main_program() return self._learning_rate_map.get(program, None) def _append_optimize_op(self, block, param_and_grad): """ append optimize operator to block and return all the added optimize_op """ raise NotImplementedError( "Class \"Optimizer\" connot be used directly as an optimizer, please use its subclasses such as \"Adam\"" ) def _create_param_lr(self, param_and_grad): # create learning rate tensor for every parameter param = param_and_grad[0] if hasattr(param, 'optimize_attr'): param_lr = param.optimize_attr['learning_rate'] if type(param_lr) == Variable: return param_lr else: if param_lr == 1.0: return self._global_learning_rate() else: with default_main_program()._lr_schedule_guard( is_with_opt=True), framework.name_scope( 'scale_with_param_lr'): return self._global_learning_rate() * param_lr else: return self._global_learning_rate() def _create_accumulators(self, block, parameters): """Create all accumulators needed by the parameters Args: block: the block in which the loss tensor is present parameters: list of parameter tensors for the optimizer """ pass def _finish_update(self, block, parameters_and_grads): """Finish any custom updates needed before completing an optimization step Args: block: the block in which the loss tensor is present parameters: list of parameter tensors for the optimizer Returns: None """ pass def _add_accumulator(self, name, param, dtype=None, fill_value=0.0, shape=None, type=None, device=None): """Utility function to add an accumulator for a parameter Args: block: the block in which the loss tensor is present name: name of the accumulator param: parameter tensor for which accumulator is to be added dtype: data type of the accumulator tensor fill_value: value to initialize the accumulator tensor """ if self._name is not None: name = self._name + "_" + name if (name in self._accumulators and param.name in self._accumulators[name]): if framework.in_dygraph_mode(): return self._accumulators[name][param.name] raise Exception("Accumulator {} already exists for parameter {}". format(name, param.name)) if shape == None: shape = param.shape assert isinstance(self.helper, LayerHelper) var_name = param.name + "_" + name var_name = unique_name.generate(var_name) self._opti_name_list.append(var_name) var = self.helper.create_global_variable( name=var_name, persistable=True, dtype=dtype or param.dtype, type=param.type if type is None else type, shape=shape, belong_to_optimizer=True) if device is None: device = self._get_device_for_param(param.name) with device_guard(device): self.helper.set_variable_initializer( var, initializer=Constant(value=float(fill_value))) if framework.in_dygraph_mode(): if len(self._accumulators_holder) > 0: assert var_name in self._accumulators_holder, \ "Optimizer set error, {} should in state dict".format( var_name ) var.set_value(self._accumulators_holder[var_name]) self._accumulators[name][param.name] = var return var def _get_accumulator(self, name, param): """Utility function to fetch an accumulator for a parameter Args: name: name of the accumulator param: parameter tensor for which accumulator is to be fetched Returns: accumulator tensor for the parameter """ if self._name is not None: name = self._name + "_" + name if (name not in self._accumulators or param.name not in self._accumulators[name]): raise Exception("Accumulator {} does not exist for parameter {}". format(name, param.name)) return self._accumulators[name][param.name] def _update_param_device_map(self, parameters_and_grads, target_block): for param_and_grad in parameters_and_grads: if param_and_grad[0].stop_gradient is False: param_name = param_and_grad[0].name ops = target_block.ops device_attr_name = core.op_proto_and_checker_maker.kOpDeviceAttrName( ) for op in ops: input_arg_names = op.input_arg_names if param_name in input_arg_names: self._param_device_map[param_name] = op.attr( device_attr_name) break def _get_device_for_param(self, param_name): device = None if param_name in self._param_device_map: device = self._param_device_map[param_name] return device def _create_optimization_pass(self, parameters_and_grads): """Add optimization operators to update gradients to tensors. Args: parameters_and_grads(list(tuple(Tensor, Tensor))): a list of (tensor, gradient) pair to update. Returns: return_op_list: a list of operators that will complete one step of optimization. This will include parameter update ops, global step update ops and any other custom ops required by subclasses to manage their internal state. """ # This is a default implementation of create_optimization_pass that # can be shared by most optimizers. This implementation assumes that # the subclass will implement the _append_optimize_op method and the # _initialize_tensors method. The subclass can extend the # _create_accumulators method if it needs to create accumulators # for parameters and extend _finish_update method to add custom ops. # Allways called under program_guard use global block as loss block # But if current block is in control flow, append optimize op in the # grad block of current block global_block = framework.default_main_program().global_block() target_block = global_block current_block = framework.default_main_program().current_block() if current_block.idx != global_block.idx: assert current_block.backward_block_idx != -1, \ "current block is not global_block, but it doesn't have backward block." target_block = framework.default_main_program().blocks[ current_block.backward_block_idx] start = len(target_block.ops) self.helper = LayerHelper(self.__class__.__name__) self._update_param_device_map(parameters_and_grads, target_block) self._create_accumulators( target_block, [p[0] for p in parameters_and_grads if not p[0].stop_gradient]) self._create_global_learning_rate() if framework.in_dygraph_mode(): for param_and_grad in parameters_and_grads: if param_and_grad[1] is None: continue if param_and_grad[0].stop_gradient is False: self._append_optimize_op(target_block, param_and_grad) else: for param_and_grad in parameters_and_grads: if param_and_grad[1] is None: continue with param_and_grad[0].block.program._optimized_guard( param_and_grad), name_scope("optimizer"): if param_and_grad[0].stop_gradient is False: device = self._get_device_for_param(param_and_grad[0] .name) with device_guard(device): optimize_op = self._append_optimize_op( target_block, param_and_grad) # Get custom finish ops for subclasses # FIXME: Need to fix this once we figure out how to handle dependencies self._finish_update(target_block, parameters_and_grads) end = len(target_block.ops) return target_block._slice_ops(start, end) def _append_dgc_ops(self, param_and_grad): pass def backward(self, loss, startup_program=None, parameters=None, no_grad_set=None, callbacks=None): """ The first part of ``minimize``, do auto-diff to append backward operations for the current program. Args: loss (Tensor): ``loss`` tensor to run optimizations. startup_program (Program, optional): :ref:`api_fluid_Program` for initializing parameters in ``parameters``. The default value is None, at this time :ref:`api_fluid_default_startup_program` will be used. parameters (list, optional): List of ``Tensor`` or ``Tensor.name`` to update to minimize ``loss``. The default value is None, at this time all parameters will be updated. no_grad_set (set, optional): Set of ``Tensor`` or ``Tensor.name`` that don't need to be updated. The default value is None. callbacks (list, optional): list of callable objects to run when appending backward operator for one parameter. The default value is None. Return: list: list of (param, grad) tensor pairs, param is ``Parameter``, grad is the gradient value corresponding to the parameter. Examples: .. code-block:: python import paddle import numpy as np value = np.arange(26).reshape(2, 13).astype("float32") a = paddle.to_tensor(value) linear = paddle.nn.Linear(13, 5) # This can be any optimizer supported by dygraph. adam = paddle.optimizer.Adam(learning_rate = 0.01, parameters = linear.parameters()) out = linear(a) out.backward() adam.step() adam.clear_grad() """ act_no_grad_set = None if framework.in_dygraph_mode(): pass else: act_no_grad_set = self._get_no_grad_set(loss, no_grad_set) # Infer dtype by loss if None if self._dtype is None: self._dtype = loss.dtype if framework.in_dygraph_mode(): parameter_list = parameters if parameters \ else self._parameter_list params_grads = [] for param in parameter_list: if param.stop_gradient: continue if param._grad_ivar() is not None: # create gradient tensor grad_var = param._grad_ivar() params_grads.append((param, grad_var)) else: if callbacks is None: callbacks = [error_clip_callback] else: assert (isinstance(callbacks, list)) program = loss.block.program assert len(loss.shape) == 1 and loss.shape[0] == 1, \ "The loss.shape should be (1L,), but the current loss.shape is {}. " \ "Maybe that you should call paddle.mean to process the current loss.".format( loss.shape) parameter_list = parameters if parameters \ else self._parameter_list with program_guard(program, startup_program): params_grads = append_backward(loss, parameter_list, act_no_grad_set, callbacks) # Note: since we can't use all_reduce_op now, # dgc_op should be the last op of one grad. self._append_dgc_ops(params_grads) return params_grads def apply_gradients(self, params_grads): """ Second part of `minimize`, appending optimization operators for given `params_grads` pairs. Args: params_grads (list): list of (param, grad) pair to do optimization. Returns: list: A list of operators appended to the current program. Examples: .. code-block:: python import paddle import numpy as np inp = np.random.uniform(-0.1, 0.1, [10, 10]).astype("float32") linear = paddle.nn.Linear(10, 10) inp = paddle.to_tensor(inp) out = linear(inp) loss = paddle.mean(out) optimizer = paddle.optimizer.Adam(learning_rate=0.1, parameters=linear.parameters()) params_grads = optimizer.backward(loss) optimizer.apply_gradients(params_grads) """ params_grads = sorted(params_grads, key=lambda x: x[0].name) # 'optimizer(grad_clip)' or 'set_gradient_clip' if self._grad_clip is not None: params_grads = self._grad_clip(params_grads) else: params_grads = append_gradient_clip_ops(params_grads) # Add regularization if any params_grads = append_regularization_ops(params_grads, self.regularization) optimize_ops = self._create_optimization_pass(params_grads) return optimize_ops def _apply_optimize(self, loss, startup_program, params_grads): """ Second part of `minimize`, appending optimization operators for given `params_grads` pairs. Args: loss (Tensor): loss tensor to run optimizations. startup_program (Program): startup_program for initializing parameters in `parameters`. params_grads (list): list of (param, grad) pair to do optimization. Returns: list: A list of operators appended to the current program. """ if framework.in_dygraph_mode(): with program_guard(framework.default_main_program(), framework.default_startup_program()): if self._grad_clip is not None: params_grads = self._grad_clip(params_grads) params_grads = append_regularization_ops(params_grads, self.regularization) optimize_ops = self._create_optimization_pass(params_grads) else: program = loss.block.program with program_guard(program, startup_program): optimize_ops = self.apply_gradients(params_grads) return optimize_ops def _get_no_grad_set(self, loss, no_grad_set=None): no_grad_set = _get_no_grad_set_name(no_grad_set) parameters = loss.block.program.global_block().all_parameters() param_no_trainable = set([ param.name for param in parameters if param.stop_gradient is True ]) # If the parameter is no trainable, it should not have a gradient. no_grad_set.update(param_no_trainable) return no_grad_set @framework.dygraph_only def clear_grad(self): """ Clear the gradients of all optimized parameters for model. If not, new gradient will accumulat on previous gradient. Returns: None Examples: .. code-block:: python import numpy as np import paddle value = np.arange(26).reshape(2, 13).astype("float32") a = paddle.to_tensor(value) linear = paddle.nn.Linear(13, 5) # This can be any optimizer supported by dygraph. adam = paddle.optimizer.Adam(learning_rate = 0.01, parameters = linear.parameters()) out = linear(a) out.backward() adam.step() adam.clear_grad() """ for p in self._parameter_list: if not p.stop_gradient: p.clear_gradient() @imperative_base.no_grad def minimize(self, loss, startup_program=None, parameters=None, no_grad_set=None): """ Add operations to minimize ``loss`` by updating ``parameters``. Args: loss (Tensor): A ``Tensor`` containing the value to minimize. startup_program (Program, optional): :ref:`api_fluid_Program` for initializing parameters in ``parameters``. The default value is None, at this time :ref:`api_fluid_default_startup_program` will be used. parameters (list, optional): List of ``Tensor`` or ``Tensor.name`` to update to minimize ``loss``. The default value is None, at this time all parameters will be updated. no_grad_set (set, optional): Set of ``Tensor`` or ``Tensor.name`` that don't need to be updated. The default value is None. Returns: tuple: tuple (optimize_ops, params_grads), A list of operators appended by minimize and a list of (param, grad) tensor pairs, param is ``Parameter``, grad is the gradient value corresponding to the parameter. In static graph mode, the returned tuple can be passed to ``fetch_list`` in ``Executor.run()`` to indicate program pruning. If so, the program will be pruned by ``feed`` and ``fetch_list`` before run, see details in ``Executor``. Examples: .. code-block:: python import paddle linear = paddle.nn.Linear(10, 10) input = paddle.uniform(shape=[10, 10], min=-0.1, max=0.1) out = linear(input) loss = paddle.mean(out) beta1 = paddle.to_tensor([0.9], dtype="float32") beta2 = paddle.to_tensor([0.99], dtype="float32") adam = paddle.optimizer.Adam(learning_rate=0.1, parameters=linear.parameters(), weight_decay=0.01) out.backward() adam.minimize(loss) adam.clear_grad() """ assert isinstance(loss, Variable), "The loss should be an Tensor." parameter_list = parameters if parameters \ else self._parameter_list params_grads = self.backward( loss, startup_program=startup_program, parameters=parameter_list, no_grad_set=no_grad_set) optimize_ops = self._apply_optimize( loss, startup_program=startup_program, params_grads=params_grads) return optimize_ops, params_grads @imperative_base.no_grad @framework.dygraph_only def step(self): """ Execute the optimizer and update parameters once. Returns: None Examples: .. code-block:: python import paddle import numpy as np value = np.arange(26).reshape(2, 13).astype("float32") a = paddle.to_tensor(value) linear = paddle.nn.Linear(13, 5) # This can be any optimizer supported by dygraph. adam = paddle.optimizer.Adam(learning_rate = 0.01, parameters = linear.parameters()) out = linear(a) out.backward() adam.step() adam.clear_grad() """ params_grads = [] for param in self._parameter_list: if param.stop_gradient: continue if param._grad_ivar() is not None: grad_var = param._grad_ivar() params_grads.append((param, grad_var)) self._apply_optimize( loss=None, startup_program=None, params_grads=params_grads)