Imagenette baseline for AdaBelief about adabelief-optimizer

[juntang-zhuang]

@tmabraham Hi, turning off fp16, and decrease batch size for both baseline and adabelief (my GPU is out of memory), I got 82.8% acc with adabelief, 82.6% with ranger, pretty close now.

See the link:
AdaBelief
Ranger

[juntang-zhuang]

@tmabraham Hi, quickly skimming over the code, I noticed that you enabled fp16. Note that this might cause error with AdaBelief and Adam, if I remember correctly, float16 rounds number blow 1e-7 to 0, this means if eps is smaller than that then it would be rounded to 0. In this case, the division could explode. AdaBelief uses eps=1e-16 or 1e-12, this might be the reason. Please let me know if you have specified the full parameters to reproduce best baseline results, or try float32 format.

[juntang-zhuang]

@tmabraham I'm closing this issue now since it seems to be solved. Please leave me a message if you have other comments.

[juntang-zhuang]

@tmabraham Hi, please try this code to deal with mixed precision training. A by-pass is to cast weight and grad to float32., then update, and cast back to float16.

import math
import torch
from torch.optim.optimizer import Optimizer
from tabulate import tabulate
from colorama import Fore, Back, Style

version_higher = ( torch.__version__ >= "1.5.0" )

class AdaBelief(Optimizer):
    r"""Implements AdaBelief algorithm. Modified from Adam in PyTorch
    Arguments:
        params (iterable): iterable of parameters to optimize or dicts defining
            parameter groups
        lr (float, optional): learning rate (default: 1e-3)
        betas (Tuple[float, float], optional): coefficients used for computing
            running averages of gradient and its square (default: (0.9, 0.999))
        eps (float, optional): term added to the denominator to improve
            numerical stability (default: 1e-16)
        weight_decay (float, optional): weight decay (L2 penalty) (default: 0)
        amsgrad (boolean, optional): whether to use the AMSGrad variant of this
            algorithm from the paper `On the Convergence of Adam and Beyond`_
            (default: False)
        weight_decouple (boolean, optional): ( default: True) If set as True, then
            the optimizer uses decoupled weight decay as in AdamW
        fixed_decay (boolean, optional): (default: False) This is used when weight_decouple
            is set as True.
            When fixed_decay == True, the weight decay is performed as
            $W_{new} = W_{old} - W_{old} \times decay$.
            When fixed_decay == False, the weight decay is performed as
            $W_{new} = W_{old} - W_{old} \times decay \times lr$. Note that in this case, the
            weight decay ratio decreases with learning rate (lr).
        rectify (boolean, optional): (default: True) If set as True, then perform the rectified
            update similar to RAdam
        degenerated_to_sgd (boolean, optional) (default:True) If set as True, then perform SGD update
            when variance of gradient is high
        print_change_log (boolean, optional) (default: True) If set as True, print the modifcation to
            default hyper-parameters
    reference: AdaBelief Optimizer, adapting stepsizes by the belief in observed gradients, NeurIPS 2020
    """

    def __init__(self, params, lr=1e-3, betas=(0.9, 0.999), eps=1e-16,
                 weight_decay=0, amsgrad=False, weight_decouple=True, fixed_decay=False, rectify=True,
                 degenerated_to_sgd=True, print_change_log = True):

        # ------------------------------------------------------------------------------
        # Print modifications to default arguments
        if print_change_log:
            print(Fore.RED + 'Please check your arguments if you have upgraded adabelief-pytorch from version 0.0.5.')
            print(Fore.RED + 'Modifications to default arguments:')
            default_table = tabulate([
                ['adabelief-pytorch=0.0.5','1e-8','False','False'],
                ['>=0.1.0 (Current 0.2.0)','1e-16','True','True']],
                headers=['eps','weight_decouple','rectify'])
            print(Fore.RED + default_table)

            recommend_table = tabulate([
                ['Recommended eps = 1e-8', 'Recommended eps = 1e-16'],
                ],
                headers=['SGD better than Adam (e.g. CNN for Image Classification)','Adam better than SGD (e.g. Transformer, GAN)'])
            print(Fore.BLUE + recommend_table)

            print(Fore.BLUE +'For a complete table of recommended hyperparameters, see')
            print(Fore.BLUE + 'https://github.com/juntang-zhuang/Adabelief-Optimizer')

            print(Fore.GREEN + 'You can disable the log message by setting "print_change_log = False", though it is recommended to keep as a reminder.')

            print(Style.RESET_ALL)
        # ------------------------------------------------------------------------------

        if not 0.0 <= lr:
            raise ValueError("Invalid learning rate: {}".format(lr))
        if not 0.0 <= eps:
            raise ValueError("Invalid epsilon value: {}".format(eps))
        if not 0.0 <= betas[0] < 1.0:
            raise ValueError("Invalid beta parameter at index 0: {}".format(betas[0]))
        if not 0.0 <= betas[1] < 1.0:
            raise ValueError("Invalid beta parameter at index 1: {}".format(betas[1]))

        self.degenerated_to_sgd = degenerated_to_sgd
        if isinstance(params, (list, tuple)) and len(params) > 0 and isinstance(params[0], dict):
            for param in params:
                if 'betas' in param and (param['betas'][0] != betas[0] or param['betas'][1] != betas[1]):
                    param['buffer'] = [[None, None, None] for _ in range(10)]

        defaults = dict(lr=lr, betas=betas, eps=eps,
                        weight_decay=weight_decay, amsgrad=amsgrad, buffer=[[None, None, None] for _ in range(10)])
        super(AdaBelief, self).__init__(params, defaults)

        self.degenerated_to_sgd = degenerated_to_sgd
        self.weight_decouple = weight_decouple
        self.rectify = rectify
        self.fixed_decay = fixed_decay
        if self.weight_decouple:
            print('Weight decoupling enabled in AdaBelief')
            if self.fixed_decay:
                print('Weight decay fixed')
        if self.rectify:
            print('Rectification enabled in AdaBelief')
        if amsgrad:
            print('AMSGrad enabled in AdaBelief')

    def __setstate__(self, state):
        super(AdaBelief, self).__setstate__(state)
        for group in self.param_groups:
            group.setdefault('amsgrad', False)

    def reset(self):
        for group in self.param_groups:
            for p in group['params']:
                state = self.state[p]
                amsgrad = group['amsgrad']

                # State initialization
                state['step'] = 0
                # Exponential moving average of gradient values
                state['exp_avg'] = torch.zeros_like(p.data,memory_format=torch.preserve_format) \
                    if version_higher else torch.zeros_like(p.data)

                # Exponential moving average of squared gradient values
                state['exp_avg_var'] = torch.zeros_like(p.data,memory_format=torch.preserve_format) \
                    if version_higher else torch.zeros_like(p.data)

                if amsgrad:
                    # Maintains max of all exp. moving avg. of sq. grad. values
                    state['max_exp_avg_var'] = torch.zeros_like(p.data,memory_format=torch.preserve_format) \
                        if version_higher else torch.zeros_like(p.data)

    def step(self, closure=None):
        """Performs a single optimization step.
        Arguments:
            closure (callable, optional): A closure that reevaluates the model
                and returns the loss.
        """
        loss = None
        if closure is not None:
            loss = closure()

        for group in self.param_groups:
            for p in group['params']:
                if p.grad is None:
                    continue

                # cast data type
                half_precision = False
                if p.data.dtype == torch.float16:
                    half_precision = True
                    p.data = p.data.float()
                    p.grad = p.grad.float()

                grad = p.grad.data
                if grad.is_sparse:
                    raise RuntimeError(
                        'AdaBelief does not support sparse gradients, please consider SparseAdam instead')
                amsgrad = group['amsgrad']

                state = self.state[p]

                beta1, beta2 = group['betas']

                # State initialization
                if len(state) == 0:
                    state['step'] = 0
                    # Exponential moving average of gradient values
                    state['exp_avg'] = torch.zeros_like(p.data,memory_format=torch.preserve_format) \
                        if version_higher else torch.zeros_like(p.data)
                    # Exponential moving average of squared gradient values
                    state['exp_avg_var'] = torch.zeros_like(p.data,memory_format=torch.preserve_format) \
                        if version_higher else torch.zeros_like(p.data)
                    if amsgrad:
                        # Maintains max of all exp. moving avg. of sq. grad. values
                        state['max_exp_avg_var'] = torch.zeros_like(p.data,memory_format=torch.preserve_format) \
                            if version_higher else torch.zeros_like(p.data)
                
                # perform weight decay, check if decoupled weight decay
                if self.weight_decouple:
                    if not self.fixed_decay:
                        p.data.mul_(1.0 - group['lr'] * group['weight_decay'])
                    else:
                        p.data.mul_(1.0 - group['weight_decay'])
                else:
                    if group['weight_decay'] != 0:
                        grad.add_(p.data, alpha=group['weight_decay'])

                # get current state variable
                exp_avg, exp_avg_var = state['exp_avg'], state['exp_avg_var']

                state['step'] += 1
                bias_correction1 = 1 - beta1 ** state['step']
                bias_correction2 = 1 - beta2 ** state['step']

                # Update first and second moment running average
                exp_avg.mul_(beta1).add_(grad, alpha=1 - beta1)
                grad_residual = grad - exp_avg
                exp_avg_var.mul_(beta2).addcmul_( grad_residual, grad_residual, value=1 - beta2)

                if amsgrad:
                    max_exp_avg_var = state['max_exp_avg_var']
                    # Maintains the maximum of all 2nd moment running avg. till now
                    torch.max(max_exp_avg_var, exp_avg_var.add_(group['eps']), out=max_exp_avg_var)

                    # Use the max. for normalizing running avg. of gradient
                    denom = (max_exp_avg_var.sqrt() / math.sqrt(bias_correction2)).add_(group['eps'])
                else:
                    denom = (exp_avg_var.add_(group['eps']).sqrt() / math.sqrt(bias_correction2)).add_(group['eps'])

                # update
                if not self.rectify:
                    # Default update
                    step_size = group['lr'] / bias_correction1
                    p.data.addcdiv_( exp_avg, denom, value=-step_size)

                else:  # Rectified update, forked from RAdam
                    buffered = group['buffer'][int(state['step'] % 10)]
                    if state['step'] == buffered[0]:
                        N_sma, step_size = buffered[1], buffered[2]
                    else:
                        buffered[0] = state['step']
                        beta2_t = beta2 ** state['step']
                        N_sma_max = 2 / (1 - beta2) - 1
                        N_sma = N_sma_max - 2 * state['step'] * beta2_t / (1 - beta2_t)
                        buffered[1] = N_sma

                        # more conservative since it's an approximated value
                        if N_sma >= 5:
                            step_size = math.sqrt(
                                (1 - beta2_t) * (N_sma - 4) / (N_sma_max - 4) * (N_sma - 2) / N_sma * N_sma_max / (
                                        N_sma_max - 2)) / (1 - beta1 ** state['step'])
                        elif self.degenerated_to_sgd:
                            step_size = 1.0 / (1 - beta1 ** state['step'])
                        else:
                            step_size = -1
                        buffered[2] = step_size

                    if N_sma >= 5:
                        denom = exp_avg_var.sqrt().add_(group['eps'])
                        p.data.addcdiv_(exp_avg, denom, value=-step_size * group['lr'])
                    elif step_size > 0:
                        p.data.add_( exp_avg, alpha=-step_size * group['lr'])

                if half_precision:
                    p.data = p.data.half()
                    p.grad = p.grad.half() 

        return loss