added function to compute likelihood between sample and target distri…

src/pytorch_llid/__init__.py

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+__version__ = '0.2.1'

src/pytorch_llid/__main__.py

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+import pytorch_llid.llid_score
+
+pytorch_llid.llid_score.main()

src/pytorch_llid/llid_score.py

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+"""Calculates the LLID between an image and batch of images to evalulate GANs
+
+The LLID metric calculates the loglikelihood of an image under a target distribution, estimated from a batch of images.
+
+See --help to see further details.
+
+Code apapted from https://github.com/bioinf-jku/TTUR to use PyTorch instead
+of Tensorflow
+
+Copyright 2018 Institute of Bioinformatics, JKU Linz
+
+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.
+"""
+import os
+import pathlib
+from argparse import ArgumentDefaultsHelpFormatter, ArgumentParser
+
+import numpy as np
+import torch
+import torchvision.transforms as TF
+from PIL import Image
+from scipy import linalg
+from scipy.stats import multivariate_normal
+from torch.nn.functional import adaptive_avg_pool2d
+
+try:
+    from tqdm import tqdm
+except ImportError:
+    # If tqdm is not available, provide a mock version of it
+    def tqdm(x):
+        return x
+
+from pytorch_fid.inception import InceptionV3
+
+parser = ArgumentParser(formatter_class=ArgumentDefaultsHelpFormatter)
+parser.add_argument('--batch-size', type=int, default=50,
+                    help='Batch size to use')
+parser.add_argument('--num-workers', type=int,
+                    help=('Number of processes to use for data loading. '
+                          'Defaults to `min(8, num_cpus)`'))
+parser.add_argument('--device', type=str, default=None,
+                    help='Device to use. Like cuda, cuda:0 or cpu')
+parser.add_argument('--dims', type=int, default=2048,
+                    choices=list(InceptionV3.BLOCK_INDEX_BY_DIM),
+                    help=('Dimensionality of Inception features to use. '
+                          'By default, uses pool3 features'))
+parser.add_argument('path', type=str, nargs=2,
+                    help=('Paths to the generated images or '
+                          'to .npz statistic files'))
+
+IMAGE_EXTENSIONS = {'bmp', 'jpg', 'jpeg', 'pgm', 'png', 'ppm',
+                    'tif', 'tiff', 'webp'}
+
+
+class ImagePathDataset(torch.utils.data.Dataset):
+    def __init__(self, files, transforms=None):
+        self.files = files
+        self.transforms = transforms
+
+    def __len__(self):
+        return len(self.files)
+
+    def __getitem__(self, i):
+        path = self.files[i]
+        img = Image.open(path).convert('RGB')
+        if self.transforms is not None:
+            img = self.transforms(img)
+        return img
+
+
+def get_activations(files, model, batch_size=50, dims=2048, device='cpu',
+                    num_workers=1):
+    """Calculates the activations of the pool_3 layer for all images.
+
+    Params:
+    -- files       : List of image files paths
+    -- model       : Instance of inception model
+    -- batch_size  : Batch size of images for the model to process at once.
+                     Make sure that the number of samples is a multiple of
+                     the batch size, otherwise some samples are ignored. This
+                     behavior is retained to match the original FID score
+                     implementation.
+    -- dims        : Dimensionality of features returned by Inception
+    -- device      : Device to run calculations
+    -- num_workers : Number of parallel dataloader workers
+
+    Returns:
+    -- A numpy array of dimension (num images, dims) that contains the
+       activations of the given tensor when feeding inception with the
+       query tensor.
+    """
+    model.eval()
+
+    if batch_size > len(files):
+        print(('Warning: batch size is bigger than the data size. '
+               'Setting batch size to data size'))
+        batch_size = len(files)
+
+    dataset = ImagePathDataset(files, transforms=TF.ToTensor())
+    dataloader = torch.utils.data.DataLoader(dataset,
+                                             batch_size=batch_size,
+                                             shuffle=False,
+                                             drop_last=False,
+                                             num_workers=num_workers)
+
+    pred_arr = np.empty((len(files), dims))
+
+    start_idx = 0
+
+    for batch in tqdm(dataloader):
+        batch = batch.to(device)
+
+        with torch.no_grad():
+            pred = model(batch)[0]
+
+        # If model output is not scalar, apply global spatial average pooling.
+        # This happens if you choose a dimensionality not equal 2048.
+        if pred.size(2) != 1 or pred.size(3) != 1:
+            pred = adaptive_avg_pool2d(pred, output_size=(1, 1))
+
+        pred = pred.squeeze(3).squeeze(2).cpu().numpy()
+
+        pred_arr[start_idx:start_idx + pred.shape[0]] = pred
+
+        start_idx = start_idx + pred.shape[0]
+
+    return pred_arr
+
+
+def calculate_frechet_distance(mu1, sigma1, mu2, sigma2, eps=1e-6):
+    """Numpy implementation of the Frechet Distance.
+    The Frechet distance between two multivariate Gaussians X_1 ~ N(mu_1, C_1)
+    and X_2 ~ N(mu_2, C_2) is
+            d^2 = ||mu_1 - mu_2||^2 + Tr(C_1 + C_2 - 2*sqrt(C_1*C_2)).
+
+    Stable version by Dougal J. Sutherland.
+
+    Params:
+    -- mu1   : Numpy array containing the activations of a layer of the
+               inception net (like returned by the function 'get_predictions')
+               for generated samples.
+    -- mu2   : The sample mean over activations, precalculated on an
+               representative data set.
+    -- sigma1: The covariance matrix over activations for generated samples.
+    -- sigma2: The covariance matrix over activations, precalculated on an
+               representative data set.
+
+    Returns:
+    --   : The Frechet Distance.
+    """
+
+    mu1 = np.atleast_1d(mu1)
+    mu2 = np.atleast_1d(mu2)
+
+    sigma1 = np.atleast_2d(sigma1)
+    sigma2 = np.atleast_2d(sigma2)
+
+    assert mu1.shape == mu2.shape, \
+        'Training and test mean vectors have different lengths'
+    assert sigma1.shape == sigma2.shape, \
+        'Training and test covariances have different dimensions'
+
+    diff = mu1 - mu2
+
+    # Product might be almost singular
+    covmean, _ = linalg.sqrtm(sigma1.dot(sigma2), disp=False)
+    if not np.isfinite(covmean).all():
+        msg = ('fid calculation produces singular product; '
+               'adding %s to diagonal of cov estimates') % eps
+        print(msg)
+        offset = np.eye(sigma1.shape[0]) * eps
+        covmean = linalg.sqrtm((sigma1 + offset).dot(sigma2 + offset))
+
+    # Numerical error might give slight imaginary component
+    if np.iscomplexobj(covmean):
+        if not np.allclose(np.diagonal(covmean).imag, 0, atol=1e-3):
+            m = np.max(np.abs(covmean.imag))
+            raise ValueError('Imaginary component {}'.format(m))
+        covmean = covmean.real
+
+    tr_covmean = np.trace(covmean)
+
+    return (diff.dot(diff) + np.trace(sigma1)
+            + np.trace(sigma2) - 2 * tr_covmean)
+
+
+def calculate_activation_statistics(files, model, batch_size=50, dims=2048,
+                                    device='cpu', num_workers=1):
+    """Calculation of the statistics used by the FID.
+    Params:
+    -- files       : List of image files paths
+    -- model       : Instance of inception model
+    -- batch_size  : The images numpy array is split into batches with
+                     batch size batch_size. A reasonable batch size
+                     depends on the hardware.
+    -- dims        : Dimensionality of features returned by Inception
+    -- device      : Device to run calculations
+    -- num_workers : Number of parallel dataloader workers
+
+    Returns:
+    -- mu    : The mean over samples of the activations of the pool_3 layer of
+               the inception model.
+    -- sigma : The covariance matrix of the activations of the pool_3 layer of
+               the inception model.
+    """
+    act = get_activations(files, model, batch_size, dims, device, num_workers)
+    mu = np.mean(act, axis=0)
+    sigma = np.cov(act, rowvar=False)
+    return mu, sigma
+
+
+def compute_statistics_of_path(path, model, batch_size, dims, device,
+                               num_workers=1):
+    if path.endswith('.npz'):
+        with np.load(path) as f:
+            m, s = f['mu'][:], f['sigma'][:]
+    else:
+        path = pathlib.Path(path)
+        files = sorted([file for ext in IMAGE_EXTENSIONS
+                       for file in path.glob('*.{}'.format(ext))])
+        m, s = calculate_activation_statistics(files, model, batch_size,
+                                               dims, device, num_workers)
+
+    return m, s
+
+
+def calculate_llid_given_paths(paths, batch_size, device, dims, num_workers=1):
+    """Calculates the likelihood of sample under the specified target distribution"""
+    for p in paths:
+        if not os.path.exists(p):
+            raise RuntimeError('Invalid path: %s' % p)
+
+    #Load Inception-V3 pretrained model        
+    block_idx = InceptionV3.BLOCK_INDEX_BY_DIM[dims]
+    model = InceptionV3([block_idx]).to(device)
+    #Compute multivariate gaussian of the target distribution
+    m1, s1 = compute_statistics_of_path(paths[0], model, batch_size,
+                                        dims, device, num_workers)
+    #Calculates the activations of the pool_3 layer for the sample
+    act = get_activations([paths[1]], model, batch_size, dims, device, num_workers)
+    #Compute likelihood of sample under the target distribution, given mean and covariance matrix
+    likelihood = multivariate_normal.logpdf(act, mean=m1, cov=s1)
+
+    return likelihood
+
+
+def main():
+    args = parser.parse_args()
+
+    if args.device is None:
+        device = torch.device('cuda' if (torch.cuda.is_available()) else 'cpu')
+    else:
+        device = torch.device(args.device)
+
+    if args.num_workers is None:
+        num_avail_cpus = len(os.sched_getaffinity(0))
+        num_workers = min(num_avail_cpus, 8)
+    else:
+        num_workers = args.num_workers
+
+    likelihood = calculate_llid_given_paths(args.path,
+                                          args.batch_size,
+                                          device,
+                                          args.dims,
+                                          num_workers)
+    print('Likelihood: ', likelihood)
+
+
+if __name__ == '__main__':
+    main()