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losses.py
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Sat, Apr 26, 16:54

losses.py
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import os
import tensorflow as tf
import numpy as np
import scipy
import data_loaders
import datetime
import sys
# import cv2
from scipy import ndimage
#from matplotlib import pyplot as plt
from PIL import Image
from keras.models import *
from keras.layers import Reshape
from keras.layers.core import *
from keras.layers import *
from keras.layers.normalization import BatchNormalization
from keras.layers.convolutional import *
from keras.layers.advanced_activations import LeakyReLU
from keras.optimizers import Adam, SGD
from keras.utils import np_utils
from keras import backend as K
def weighted_categorical_crossentropy(weights):
"""
A weighted version of keras.objectives.categorical_crossentropy
Variables:
weights: numpy array of shape (C,) where C is the number of classes
Usage:
weights = np.array([0.5,2,10]) # Class one at 0.5, class 2 twice the normal weights, class 3 10x.
loss = weighted_categorical_crossentropy(weights)
model.compile(loss=loss,optimizer='adam')
"""
weights = K.variable(weights)
def loss(y_true, y_pred):
# scale predictions so that the class probas of each sample sum to 1
y_pred /= K.sum(y_pred, axis=-1, keepdims=True)
# clip to prevent NaN's and Inf's
y_pred = K.clip(y_pred, K.epsilon(), 1 - K.epsilon())
# calc
loss = y_true * K.log(y_pred) * weights
loss = -K.sum(loss, -1)
return loss
return loss
def jaccard_distance_loss(y_true, y_pred, smooth=100):
"""
Jaccard = (|X & Y|)/ (|X|+ |Y| - |X & Y|)
= sum(|A*B|)/(sum(|A|)+sum(|B|)-sum(|A*B|))
The jaccard distance loss is usefull for unbalanced datasets. This has been
shifted so it converges on 0 and is smoothed to avoid exploding or disapearing
gradient.
Ref: https://en.wikipedia.org/wiki/Jaccard_index
@url: https://gist.github.com/wassname/f1452b748efcbeb4cb9b1d059dce6f96
@author: wassname
"""
intersection = K.sum(K.abs(y_true * y_pred), axis=-1)
sum_ = K.sum(K.abs(y_true) + K.abs(y_pred), axis=-1)
jac = (intersection + smooth) / (sum_ - intersection + smooth)
return (1 - jac) * smooth
def dice_coef(y_true, y_pred, smooth=0.01):
"""
~Intersection over Union (IoU)
Dice = (2*|X & Y|)/ (|X|+ |Y|)
= 2*sum(|A*B|)/(sum(A^2)+sum(B^2))
ref: https://github.com/keras-team/keras/issues/3611
"""
y_true_f = K.flatten(y_true[..., 1])
y_pred_f = K.flatten(y_pred[..., 1])
intersection = tf.to_float(K.sum(y_true_f * y_pred_f))
union = tf.to_float(K.sum(y_true_f) + K.sum(y_pred_f)) - intersection
return (2. * intersection + smooth) / (union + smooth)
def dice_coef_loss(y_true, y_pred):
return 1-dice_coef(y_true, y_pred)

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