enable_spectral_reparam.py

# Copyright (c) 2023-2024, NVIDIA CORPORATION.  All rights reserved.
#
# NVIDIA CORPORATION and its licensors retain all intellectual property
# and proprietary rights in and to this software, related documentation
# and any modifications thereto.  Any use, reproduction, disclosure or
# distribution of this software and related documentation without an express
# license agreement from NVIDIA CORPORATION is strictly prohibited.

from logging import getLogger
import math
import os
from typing import List, Union, Tuple
from types import MethodType

import torch
from torch import nn
from torch.nn import functional as F
from torch.nn.utils import parametrize
from torch.nn.utils.parametrizations import _SpectralNorm

from timm.models.vision_transformer import Attention, Mlp

_EPS = 1e-5


class _SNReweight(_SpectralNorm):
    def __init__(self, weight: torch.Tensor, *args, init_norm_to_current: bool = False, alpha: float = 0.05, version: int = 2, **kwargs):
        super().__init__(weight, *args, **kwargs)

        self.alpha = alpha
        self.version = version
        self.register_buffer('_sn_version', torch.tensor(version))

        if init_norm_to_current:
            # This will set the numerator to match the denominator, which should preserve the original values
            init_scale = self._get_sigma(weight, n_power_iterations=20).item()
        else:
            init_scale = 1.0

        if version == 1:
            init_value = init_scale
        elif version == 2:
            t = init_scale - alpha
            if t < _EPS:
                getLogger("spectral_reparam").warn(f'The initialized spectral norm {init_scale} is too small to be represented. Setting to {_EPS} instead.')
                t = _EPS

            init_value = math.log(math.exp(t) - 1)
        else:
            raise ValueError(f'Unsupported version: {version}')

        # Make 2D so that weight decay gets applied
        self.scale = nn.Parameter(torch.tensor([[init_value]], dtype=torch.float32, device=weight.device))

    # Re-implementing this because we need to make division by sigma safe
    def _get_sigma(self, weight: torch.Tensor, n_power_iterations: int = None) -> torch.Tensor:
        if not n_power_iterations:
            n_power_iterations = self.n_power_iterations
        if weight.ndim == 1:
            # Faster and more exact path, no need to approximate anything
            sigma = weight.norm()
        else:
            weight_mat = self._reshape_weight_to_matrix(weight)
            if self.training:
                self._power_method(weight_mat, n_power_iterations)
            # See above on why we need to clone
            u = self._u.clone(memory_format=torch.contiguous_format)
            v = self._v.clone(memory_format=torch.contiguous_format)
            # The proper way of computing this should be through F.bilinear, but
            # it seems to have some efficiency issues:
            # https://github.com/pytorch/pytorch/issues/58093
            sigma = torch.dot(u, torch.mv(weight_mat, v))

        return sigma + self.eps

    def forward(self, weight: torch.Tensor, *args, **kwargs):
        dtype = weight.dtype
        sigma = self._get_sigma(weight, *args, **kwargs)

        if self.version == 1:
            scale = self.scale
        elif self.version == 2:
            scale = F.softplus(self.scale) + self.alpha
        else:
            raise ValueError(f'Unsupported version: {self.version}')

        scale = scale.float() / sigma.float()

        y = weight * scale

        if dtype in (torch.float16, torch.bfloat16):
            y = y.to(dtype)
        return y

    def _load_from_state_dict(self, state_dict, prefix, local_metadata, strict, missing_keys, unexpected_keys, error_msgs):
        version_key = f'{prefix}_sn_version'
        if version_key not in state_dict:
            self.version = 1
            state_dict[version_key] = torch.tensor(1)
        return super()._load_from_state_dict(state_dict, prefix, local_metadata, strict, missing_keys, unexpected_keys, error_msgs)


class _ChunkedSNReweight(nn.Module):
    def __init__(self, weight: torch.Tensor, num_chunks: int, *args, init_norm_to_current: bool = False, **kwargs):
        super().__init__()

        self.num_chunks = num_chunks
        parts = weight.split(weight.shape[0] // num_chunks, dim=0)

        self.parts = nn.ModuleList([
            _SNReweight(p, *args, init_norm_to_current=init_norm_to_current, **kwargs)
            for p in parts
        ])

    def forward(self, weight: torch.Tensor, *args, **kwargs):
        parts = weight.split(weight.shape[0] // self.num_chunks, dim=0)

        parts = [
            fn(p)
            for fn, p in zip(self.parts, parts)
        ]

        return torch.cat(parts, dim=0)


class _AttnSNReweight(_ChunkedSNReweight):
    def __init__(self, weight: torch.Tensor, *args, init_norm_to_current: bool = False, renorm_values: bool = False, **kwargs):
        super().__init__(weight, 3, *args, init_norm_to_current=init_norm_to_current, **kwargs)

        if not renorm_values:
            self.parts[2] = nn.Identity()


def enable_spectral_reparam(model: Union[nn.Module, List[nn.Module]],
                            n_power_iterations: int = 1,
                            eps: float = 1e-6,
                            init_norm_to_current: bool = False,
                            renorm_values: bool = True,
                            renorm_mlp: bool = True):
    if isinstance(model, (list, tuple)):
        for sub in model:
            enable_spectral_reparam(sub, n_power_iterations=n_power_iterations, eps=eps,
                                    init_norm_to_current=init_norm_to_current, renorm_values=renorm_values,
                                    renorm_mlp=renorm_mlp)
        return

    print('Enabling spectral reparametrization')
    args = dict(n_power_iterations=n_power_iterations, dim=0, eps=eps, init_norm_to_current=init_norm_to_current)
    visited_prefixes = set()

    def parametrize_linear(linear: nn.Linear):
        parametrize.register_parametrization(
            linear,
            'weight',
            _SNReweight(linear.weight, **args)
        )

    for name, mod in model.named_modules():
        pref = '.'.join(name.split('.')[:-1])
        if pref in visited_prefixes:
            continue

        if isinstance(mod, Attention) or name.endswith('.attn'):
            parametrize.register_parametrization(
                mod.qkv,
                'weight',
                _AttnSNReweight(mod.qkv.weight, renorm_values=renorm_values, **args),
            )
            if hasattr(mod, 'proj'):
                parametrize_linear(mod.proj)
            visited_prefixes.add(name)
        elif name.endswith('mlp') and renorm_mlp and hasattr(mod, 'w12'):
            parametrize.register_parametrization(
                mod.w12,
                'weight',
                _ChunkedSNReweight(mod.w12.weight, num_chunks=2, **args),
            )
            parametrize_linear(mod.w3)
            visited_prefixes.add(name)
        elif isinstance(mod, nn.Linear) and 'patch_generator' not in name:
            parametrize_linear(mod)


def configure_spectral_reparam_from_args(model: nn.Module, args):
    spectral_reparam = getattr(args, 'spectral_reparam', False)
    if isinstance(spectral_reparam, bool) and spectral_reparam:
        enable_spectral_reparam(model, init_norm_to_current=True)
    elif isinstance(spectral_reparam, dict):
        enable_spectral_reparam(
            model,
            n_power_iterations=spectral_reparam.get('n_power_iterations', 1),
            eps=spectral_reparam.get('eps', 1e-12),
            init_norm_to_current=True,
        )


def disable_spectral_reparam(model: nn.Module):
    print('Disabling spectral reparametrization')
    for name, mod in model.named_modules():
        if parametrize.is_parametrized(mod):
            parametrize.remove_parametrizations(mod, 'weight')
            pass



if __name__ == '__main__':
    import argparse
    from . import radio_model as create_model

    parser = argparse.ArgumentParser(description='Remove parametrization from state dict')
    parser.add_argument('--checkpoint', type=str, required=True, help='The checkpoint to load')
    parser.add_argument('--output', type=str, default='', help='Where to store the checkpoint')
    parser.add_argument('--release', default=False, action='store_true', help='Prune extraneous checkpoint fields')
    parser.add_argument('--strict', default=False, action='store_true', help='Strictly load the state dict')

    args = parser.parse_args()

    if not args.output:
        chk_dir, chk_name = os.path.split(args.checkpoint)
        args.output = os.path.join(chk_dir, f'clean_{chk_name}')
        print(f'Set output to "{args.output}"')

    chk = torch.load(args.checkpoint, map_location='cpu', mmap=True)

    model = create_model.create_model_from_args(chk['args'])

    key = 'base_model.'
    mod_state = dict()
    extra_state = dict()
    for k, v in chk['state_dict'].items():
        if k.startswith(key):
            mod_state[k[len(key):]] = v
        else:
            extra_state[k] = v

    chk_load_info = model.load_state_dict(mod_state, strict=args.strict)
    if chk_load_info.unexpected_keys or chk_load_info.missing_keys:
        print(chk_load_info)

    if chk['args'].spectral_reparam:
        disable_spectral_reparam(model)

    if hasattr(chk['args'], 'dtype'):
        model.to(dtype=chk['args'].dtype)

    mod_state = model.state_dict()
    final_state = dict()
    final_state.update({f'{key}{k}': v for k, v in mod_state.items()})
    final_state.update(extra_state)

    chk['state_dict'] = final_state
    chk['args'].spectral_reparam = False

    if args.release:
        chk = {
            'arch': chk['arch'],
            'epoch': chk['epoch'],
            'state_dict': chk['state_dict'],
            'args': chk['args'],
        }

    torch.save(chk, args.output)
    pass