utils.py

import torch
import torch.nn.functional as F
import os
import math
from enum import Enum
import sys


class TestAccuracies:
    """
    Determines if an evaluation on the validation set is better than the best so far.
    In particular, this handles the case for meta-dataset where we validate on multiple datasets and we deem
    the evaluation to be better if more than half of the validation accuracies on the individual validation datsets
    are better than the previous best.
    """

    def __init__(self, validation_datasets):
        self.datasets = validation_datasets
        self.dataset_count = len(self.datasets)
#        self.current_best_accuracy_dict = {}
#        for dataset in self.datasets:
#            self.current_best_accuracy_dict[dataset] = {"accuracy": 0.0, "confidence": 0.0}

#    def is_better(self, accuracies_dict):
#        is_better = False
#        is_better_count = 0
#        for i, dataset in enumerate(self.datasets):
#            if accuracies_dict[dataset]["accuracy"] > self.current_best_accuracy_dict[dataset]["accuracy"]:
#                is_better_count += 1
#
#        if is_better_count >= int(math.ceil(self.dataset_count / 2.0)):
#            is_better = True
#
#        return is_better

#    def replace(self, accuracies_dict):
#        self.current_best_accuracy_dict = accuracies_dict

    def print(self, logfile, accuracy_dict):
        print_and_log(logfile, "")  # add a blank line
        print_and_log(logfile, "Test Accuracies:")
        for dataset in self.datasets:
            print_and_log(logfile, "{0:}: {1:.1f}+/-{2:.1f}".format(dataset, accuracy_dict[dataset]["accuracy"],
                                                                    accuracy_dict[dataset]["confidence"]))
        print_and_log(logfile, "")  # add a blank line

#    def get_current_best_accuracy_dict(self):
#        return self.current_best_accuracy_dict


def verify_checkpoint_dir(checkpoint_dir, resume, test_mode):
    if resume:  # verify that the checkpoint directory and file exists
        if not os.path.exists(checkpoint_dir):
            print("Can't resume for checkpoint. Checkpoint directory ({}) does not exist.".format(checkpoint_dir), flush=True)
            sys.exit()

        checkpoint_file = os.path.join(checkpoint_dir, 'checkpoint.pt')
        if not os.path.isfile(checkpoint_file):
            print("Can't resume for checkpoint. Checkpoint file ({}) does not exist.".format(checkpoint_file), flush=True)
            sys.exit()
    # elif test_mode:
    #    if not os.path.exists(checkpoint_dir):
    #        print("Can't test. Checkpoint directory ({}) does not exist.".format(checkpoint_dir), flush=True)
    #        sys.exit()
    else:
        if os.path.exists(checkpoint_dir):
            print("Checkpoint directory ({}) already exits.".format(checkpoint_dir), flush=True)
            print("If starting a new training run, specify a directory that does not already exist.", flush=True)
            print("If you want to resume a training run, specify the -r option on the command line.", flush=True)
            sys.exit()


def print_and_log(log_file, message):
    """
    Helper function to print to the screen and the cnaps_layer_log.txt file.
    """
    print(message, flush=True)
    log_file.write(message + '\n')


def get_log_files(checkpoint_dir, resume, test_mode):
    """
    Function that takes a path to a checkpoint directory and returns a reference to a logfile and paths to the
    fully trained model and the model with the best validation score.
    """
    # 该函数检验从头训练时候不要有文件夹，继续训练时候应该有文件夹
    verify_checkpoint_dir(checkpoint_dir, resume, test_mode)
    # if not test_mode and not resume:
    if not resume:
        os.makedirs(checkpoint_dir)
    checkpoint_path_validation = os.path.join(checkpoint_dir, 'best_validation.pt')
    checkpoint_path_final = os.path.join(checkpoint_dir, 'fully_trained.pt')
    logfile_path = os.path.join(checkpoint_dir, 'log.txt')
    if os.path.isfile(logfile_path):
        # "a"写入打开，如果文件存在则添加到尾部
        logfile = open(logfile_path, "a", buffering=1)
    else:
        # "w"写入打开，首先截断文件，buffering是一个整数可选项，用于设置缓冲策略，传入0关闭缓冲（仅允许在二进制模式下），1选择行缓冲（尽用于文本模式）
        logfile = open(logfile_path, "w", buffering=1)

    return checkpoint_dir, logfile, checkpoint_path_validation, checkpoint_path_final


def stack_first_dim(x):
    """
    Method to combine the first two dimension of an array
    """
    x_shape = x.size()
    new_shape = [x_shape[0] * x_shape[1]]
    if len(x_shape) > 2:
        new_shape += x_shape[2:]
    return x.view(new_shape)


def split_first_dim_linear(x, first_two_dims):
    """
    Undo the stacking operation
    """
    x_shape = x.size()
    new_shape = first_two_dims
    if len(x_shape) > 1:
        new_shape += [x_shape[-1]]
    return x.view(new_shape)


def sample_normal(mean, var, num_samples):
    """
    Generate samples from a reparameterized normal distribution
    :param mean: tensor - mean parameter of the distribution
    :param var: tensor - variance of the distribution
    :param num_samples: np scalar - number of samples to generate
    :return: tensor - samples from distribution of size numSamples x dim(mean)
    """
    sample_shape = [num_samples] + len(mean.size())*[1]
    normal_distribution = torch.distributions.Normal(mean.repeat(sample_shape), var.repeat(sample_shape))
    return normal_distribution.rsample()


def loss(test_logits_sample, test_labels, device):
    """
    Compute the classification loss.
    """
    size = test_logits_sample.size()
    sample_count = size[0]  # scalar for the loop counter
    num_samples = torch.tensor([sample_count], dtype=torch.float, device=device, requires_grad=False)

    log_py = torch.empty(size=(size[0], size[1]), dtype=torch.float, device=device)
    for sample in range(sample_count):
        log_py[sample] = -F.cross_entropy(test_logits_sample[sample], test_labels, reduction='none')
    score = torch.logsumexp(log_py, dim=0) - torch.log(num_samples)
    return -torch.sum(score, dim=0)


def aggregate_accuracy(test_logits_sample, test_labels):
    """
    Compute classification accuracy.
    """
    averaged_predictions = torch.logsumexp(test_logits_sample, dim=0)
    return torch.mean(torch.eq(test_labels, torch.argmax(averaged_predictions, dim=-1)).float())


def task_confusion(test_logits, test_labels, real_test_labels, batch_class_list):
    preds = torch.argmax(torch.logsumexp(test_logits, dim=0), dim=-1)
    real_preds = batch_class_list[preds]
    return real_preds


def linear_classifier(x, param_dict):
    """
    Classifier.
    """
    return F.linear(x, param_dict['weight_mean'], param_dict['bias_mean'])