chore: import upstream snapshot with attribution
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# Copyright (c) Facebook, Inc. and its affiliates.
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#
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# This source code is licensed under the MIT license found in the
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# LICENSE file in the root directory of this source tree.
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import importlib
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from collections.abc import Collection
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from dataclasses import dataclass, field
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from typing import List
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import torch
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from fairseq.dataclass import FairseqDataclass
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from fairseq.optim import FairseqOptimizer, register_optimizer
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from omegaconf import II, DictConfig
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try:
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from deepspeed.ops.op_builder import CPUAdamBuilder
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has_deepspeed_cpu_adam = True
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except ImportError:
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has_deepspeed_cpu_adam = False
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@dataclass
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class FairseqCPUAdamConfig(FairseqDataclass):
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adam_betas: str = field(
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default="(0.9, 0.999)", metadata={"help": "betas for Adam optimizer"}
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)
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adam_eps: float = field(
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default=1e-8, metadata={"help": "epsilon for Adam optimizer"}
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)
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weight_decay: float = field(default=0.0, metadata={"help": "weight decay"})
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fp16_adam_stats: bool = field(
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default=False, metadata={"help": "use FP16 stats (with automatic scaling)"}
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)
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# TODO common vars below in parent
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lr: List[float] = II("optimization.lr")
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@register_optimizer("cpu_adam", dataclass=FairseqCPUAdamConfig)
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class FairseqCPUAdam(FairseqOptimizer):
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"""Adam optimizer for fairseq, optimized for CPU tensors.
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Important note: this optimizer corresponds to the "AdamW" variant of
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Adam in its weight decay behavior. As such, it is most closely
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analogous to torch.optim.AdamW from PyTorch.
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"""
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def __init__(self, cfg: DictConfig, params):
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super().__init__(cfg)
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self._optimizer = CPUAdam(params, **self.optimizer_config)
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@property
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def optimizer_config(self):
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"""
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Return a kwarg dictionary that will be used to override optimizer
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args stored in checkpoints. This allows us to load a checkpoint and
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resume training using a different set of optimizer args, e.g., with a
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different learning rate.
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"""
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return {
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"lr": self.cfg.lr[0]
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if isinstance(self.cfg.lr, Collection)
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else self.cfg.lr,
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"betas": eval(self.cfg.adam_betas),
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"eps": self.cfg.adam_eps,
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"weight_decay": self.cfg.weight_decay,
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"use_fp16_stats": self.cfg.fp16_adam_stats,
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}
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class CPUAdam(torch.optim.Optimizer):
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optimizer_id = 0
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def __init__(
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self,
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params,
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lr=1e-3,
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bias_correction=True,
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betas=(0.9, 0.999),
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eps=1e-8,
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weight_decay=0,
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use_fp16_stats=False,
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):
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defaults = {
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"lr": lr,
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"bias_correction": bias_correction,
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"betas": betas,
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"eps": eps,
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"weight_decay": weight_decay,
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}
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super().__init__(params, defaults)
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self.use_fp16_stats = use_fp16_stats
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self.FLOAT16_MAX = 65504.0
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if not has_deepspeed_cpu_adam:
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raise ImportError("Please install DeepSpeed: pip install deepspeed")
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self.opt_id = CPUAdam.optimizer_id
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CPUAdam.optimizer_id = CPUAdam.optimizer_id + 1
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self.ds_opt_adam = CPUAdamBuilder().load()
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adamw_mode = True
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self.ds_opt_adam.create_adam(
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self.opt_id, lr, betas[0], betas[1], eps, weight_decay, adamw_mode
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)
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@torch.no_grad()
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def step(self, closure=None):
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loss = None
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if closure is not None:
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with torch.enable_grad():
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loss = closure()
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for group_id, group in enumerate(self.param_groups):
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for param_id, p in enumerate(group["params"]):
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if p.grad is None:
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continue
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state = self.state[p]
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if len(state) == 0:
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state["step"] = 0
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dtype = torch.float16 if self.use_fp16_stats else p.data.dtype
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# gradient momentums
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state["exp_avg"] = torch.zeros_like(
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p.data, dtype=dtype, device="cpu"
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)
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# gradient variances
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state["exp_avg_sq"] = torch.zeros_like(
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p.data, dtype=dtype, device="cpu"
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)
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if self.use_fp16_stats:
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assert torch.is_floating_point(p.data)
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state["exp_avg_scale"] = 1.0
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state["exp_avg_sq_scale"] = 1.0
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exp_avg, exp_avg_sq = state["exp_avg"], state["exp_avg_sq"]
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p_data_bak = p.data # backup of the original data pointer
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p.data = p.data.to(dtype=torch.float32, device="cpu")
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p.grad.data = p.grad.data.to(dtype=torch.float32, device="cpu")
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if self.use_fp16_stats:
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exp_avg = exp_avg.float() * state["exp_avg_scale"]
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exp_avg_sq = exp_avg_sq.float() * state["exp_avg_sq_scale"]
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state["step"] += 1
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beta1, beta2 = group["betas"]
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self.ds_opt_adam.adam_update(
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self.opt_id,
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state["step"],
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group["lr"],
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beta1,
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beta2,
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group["eps"],
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group["weight_decay"],
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group["bias_correction"],
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p.data,
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p.grad.data,
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exp_avg,
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exp_avg_sq,
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)
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if p_data_bak.data_ptr() != p.data.data_ptr():
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p_data_bak.copy_(p.data)
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p.data = p_data_bak
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if self.use_fp16_stats:
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def inf_norm(t):
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return torch.norm(t, float("inf"))
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# from github.com/openai/jukebox/blob/master/jukebox/utils/fp16.py
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state["exp_avg_scale"], state["exp_avg_sq_scale"] = (
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1e-8 + inf_norm(exp_avg) / self.FLOAT16_MAX,
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1e-8 + inf_norm(exp_avg_sq) / self.FLOAT16_MAX,
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)
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state["exp_avg"], state["exp_avg_sq"] = (
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(exp_avg / state["exp_avg_scale"]).half(),
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(exp_avg_sq / state["exp_avg_sq_scale"]).half(),
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)
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return loss
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