Python keras.backend.max() Examples

def yolo_filter_boxes(box_confidence, boxes, box_class_probs, threshold = .6):    
    # Compute box scores
    box_scores = box_confidence * box_class_probs
    
    # Find the box_classes thanks to the max box_scores, keep track of the corresponding score
    box_classes = K.argmax(box_scores, axis=-1)
    box_class_scores = K.max(box_scores, axis=-1, keepdims=False)
    
    # Create a filtering mask based on "box_class_scores" by using "threshold". The mask should have the
    # same dimension as box_class_scores, and be True for the boxes you want to keep (with probability >= threshold)
    filtering_mask = box_class_scores >= threshold
    
    # Apply the mask to scores, boxes and classes
    scores = tf.boolean_mask(box_class_scores, filtering_mask)
    boxes = tf.boolean_mask(boxes, filtering_mask)
    classes = tf.boolean_mask(box_classes, filtering_mask)
    
    return scores, boxes, classes 

def call(self, x, mask=None):
        # computes a probability distribution over the timesteps
        # uses 'max trick' for numerical stability
        # reshape is done to avoid issue with Tensorflow
        # and 1-dimensional weights
        logits = K.dot(x, self.W)
        x_shape = K.shape(x)
        logits = K.reshape(logits, (x_shape[0], x_shape[1]))
        ai = K.exp(logits - K.max(logits, axis=-1, keepdims=True))

        # masked timesteps have zero weight
        if mask is not None:
            mask = K.cast(mask, K.floatx())
            ai = ai * mask
        att_weights = ai / (K.sum(ai, axis=1, keepdims=True) + K.epsilon())
        weighted_input = x * K.expand_dims(att_weights)
        result = K.sum(weighted_input, axis=1)
        if self.return_attention:
            return [result, att_weights]
        return result 

def time_distributed_nonzero_max_pooling(x):
    """
    Computes maximum along the first (time) dimension.
    It ignores the mask m.

    In:
        x - input; a 3D tensor
        mask_value - value to mask out, if None then no masking; 
            by default 0.0, 
    """

    import theano.tensor as T

    mask_value=0.0
    x = T.switch(T.eq(x, mask_value), -numpy.inf, x)
    masked_max_x = x.max(axis=1)
    # replace infinities with mask_value
    masked_max_x = T.switch(T.eq(masked_max_x, -numpy.inf), 0, masked_max_x)
    return masked_max_x 

def time_distributed_masked_max(x, m):
    """
    Computes max along the first (time) dimension.

    In:
        x - input; a 3D tensor
        m - mask
        m_value - value for masking
    """
    # place infinities where mask is off
    m_value = 0.0
    tmp = K.switch(K.equal(m, 0.0), -numpy.inf, 0.0)
    x_with_inf = x + K.expand_dims(tmp)
    x_max = K.max(x_with_inf, axis=1) 
    r = K.switch(K.equal(x_max, -numpy.inf), m_value, x_max)
    return r 


## classes  ##

# Transforms existing layers to masked layers 

def gen_adv_loss(logits, y, loss='logloss', mean=False):
    """
    Generate the loss function.
    """

    if loss == 'training':
        # use the model's output instead of the true labels to avoid
        # label leaking at training time
        y = K.cast(K.equal(logits, K.max(logits, 1, keepdims=True)), "float32")
        y = y / K.sum(y, 1, keepdims=True)
        out = K.categorical_crossentropy(y, logits, from_logits=True)
    elif loss == 'logloss':
        out = K.categorical_crossentropy(y, logits, from_logits=True)
    else:
        raise ValueError("Unknown loss: {}".format(loss))

    if mean:
        out = K.mean(out)
    # else:
    #     out = K.sum(out)
    return out 

def gen_adv_loss(logits, y, loss='logloss', mean=False):
    """
    Generate the loss function.
    """

    if loss == 'training':
        # use the model's output instead of the true labels to avoid
        # label leaking at training time
        y = K.cast(K.equal(logits, K.max(logits, 1, keepdims=True)), "float32")
        y = y / K.sum(y, 1, keepdims=True)
        out = K.categorical_crossentropy(logits, y, from_logits=True)
    elif loss == 'logloss':
        # out = K.categorical_crossentropy(logits, y, from_logits=True)
        out = tf.nn.softmax_cross_entropy_with_logits(logits=logits, labels=y)
        out = tf.reduce_mean(out)
    else:
        raise ValueError("Unknown loss: {}".format(loss))

    if mean:
        out = tf.mean(out)
    # else:
    #     out = K.sum(out)
    return out 

def calculate_gradient_weighted_CAM(gradient_function, image):
    output, evaluated_gradients = gradient_function([image, False])
    output, evaluated_gradients = output[0, :], evaluated_gradients[0, :, :, :]
    weights = np.mean(evaluated_gradients, axis=(0, 1))
    CAM = np.ones(output.shape[0: 2], dtype=np.float32)
    for weight_arg, weight in enumerate(weights):
        CAM = CAM + (weight * output[:, :, weight_arg])
    CAM = cv2.resize(CAM, (64, 64))
    CAM = np.maximum(CAM, 0)
    heatmap = CAM / np.max(CAM)

    # Return to BGR [0..255] from the preprocessed image
    image = image[0, :]
    image = image - np.min(image)
    image = np.minimum(image, 255)

    CAM = cv2.applyColorMap(np.uint8(255 * heatmap), cv2.COLORMAP_JET)
    CAM = np.float32(CAM) + np.float32(image)
    CAM = 255 * CAM / np.max(CAM)
    return np.uint8(CAM), heatmap 

def yolo_eval(yolo_outputs, image_shape=(720., 1280.), max_boxes=10, score_threshold=.6, iou_threshold=.5):    
    # Retrieve outputs of the YOLO model (≈1 line)
    box_confidence, box_xy, box_wh, box_class_probs = yolo_outputs

    # Convert boxes to be ready for filtering functions 
    boxes = yolo_boxes_to_corners(box_xy, box_wh)

    # Use one of the functions you've implemented to perform Score-filtering with a threshold of score_threshold (≈1 line)
    scores, boxes, classes = yolo_filter_boxes(box_confidence, boxes, box_class_probs, score_threshold)
    
    # Scale boxes back to original image shape.
    boxes = scale_boxes(boxes, image_shape) # boxes: [y1, x1, y2, x2]

    # Use one of the functions you've implemented to perform Non-max suppression with a threshold of iou_threshold (≈1 line)
    scores, boxes, classes = yolo_non_max_suppression(scores, boxes, classes, max_boxes, iou_threshold)
    
    ### END CODE HERE ###
    
    return scores, boxes, classes 

def calculate_gradient_weighted_CAM(gradient_function, image):
    output, evaluated_gradients = gradient_function([image, False])
    output, evaluated_gradients = output[0, :], evaluated_gradients[0, :, :, :]
    weights = np.mean(evaluated_gradients, axis = (0, 1))
    CAM = np.ones(output.shape[0 : 2], dtype=np.float32)
    for weight_arg, weight in enumerate(weights):
        CAM = CAM + (weight * output[:, :, weight_arg])
    CAM = cv2.resize(CAM, (64, 64))
    CAM = np.maximum(CAM, 0)
    heatmap = CAM / np.max(CAM)

    #Return to BGR [0..255] from the preprocessed image
    image = image[0, :]
    image = image - np.min(image)
    image = np.minimum(image, 255)

    CAM = cv2.applyColorMap(np.uint8(255 * heatmap), cv2.COLORMAP_JET)
    CAM = np.float32(CAM) + np.float32(image)
    CAM = 255 * CAM / np.max(CAM)
    return np.uint8(CAM), heatmap 

def calculate_gradient_weighted_CAM(gradient_function, image):
    output, evaluated_gradients = gradient_function([image, False])
    output, evaluated_gradients = output[0, :], evaluated_gradients[0, :, :, :]
    weights = np.mean(evaluated_gradients, axis = (0, 1))
    CAM = np.ones(output.shape[0 : 2], dtype=np.float32)
    for weight_arg, weight in enumerate(weights):
        CAM = CAM + (weight * output[:, :, weight_arg])
    CAM = cv2.resize(CAM, (64, 64))
    CAM = np.maximum(CAM, 0)
    heatmap = CAM / np.max(CAM)

    #Return to BGR [0..255] from the preprocessed image
    image = image[0, :]
    image = image - np.min(image)
    image = np.minimum(image, 255)

    CAM = cv2.applyColorMap(np.uint8(255 * heatmap), cv2.COLORMAP_JET)
    CAM = np.float32(CAM) + np.float32(image)
    CAM = 255 * CAM / np.max(CAM)
    return np.uint8(CAM), heatmap 

def lq_loss_wrap(_q):
    def lq_loss_core(y_true, y_pred):
        """
        This loss function is proposed in:
         Zhilu Zhang and Mert R. Sabuncu, "Generalized Cross Entropy Loss for Training Deep Neural Networks with
         Noisy Labels", 2018
        https://arxiv.org/pdf/1805.07836.pdf
        :param y_true:
        :param y_pred:
        :return:
        """

        # hyper param
        print(_q)

        _tmp = y_pred * y_true
        _loss = K.max(_tmp, axis=-1)

        # compute the Lq loss between the one-hot encoded label and the prediction
        _loss = (1 - (_loss + 10 ** (-8)) ** _q) / _q

        return _loss
    return lq_loss_core 

def _softmax(x, axis=-1, alpha=1):
    """
    building on keras implementation, allow alpha parameter

    Softmax activation function.
    # Arguments
        x : Tensor.
        axis: Integer, axis along which the softmax normalization is applied.
        alpha: a value to multiply all x
    # Returns
        Tensor, output of softmax transformation.
    # Raises
        ValueError: In case `dim(x) == 1`.
    """
    x = alpha * x
    ndim = K.ndim(x)
    if ndim == 2:
        return K.softmax(x)
    elif ndim > 2:
        e = K.exp(x - K.max(x, axis=axis, keepdims=True))
        s = K.sum(e, axis=axis, keepdims=True)
        return e / s
    else:
        raise ValueError('Cannot apply softmax to a tensor that is 1D') 

def call(self, x, mask=None):
        # computes a probability distribution over the timesteps
        # uses 'max trick' for numerical stability
        # reshape is done to avoid issue with Tensorflow
        # and 1-dimensional weights
        logits = K.dot(x, self.W)
        x_shape = K.shape(x)
        logits = K.reshape(logits, (x_shape[0], x_shape[1]))
        ai = K.exp(logits - K.max(logits, axis=-1, keepdims=True))

        # masked timesteps have zero weight
        if mask is not None:
            mask = K.cast(mask, K.floatx())
            ai = ai * mask
        att_weights = ai / (K.sum(ai, axis=1, keepdims=True) + K.epsilon())
        weighted_input = x * K.expand_dims(att_weights)
        result = K.sum(weighted_input, axis=1)
        if self.return_attention:
            return [result, att_weights]
        return result 

def call(self, inputs, mask=None, **kwargs):
        if isinstance(inputs, list):
            query, key, value = inputs
        else:
            query = key = value = inputs
        if isinstance(mask, list):
            mask = mask[1]
        feature_dim = K.shape(query)[-1]
        e = K.batch_dot(query, key, axes=2) / K.sqrt(K.cast(feature_dim, dtype=K.floatx()))
        e = K.exp(e - K.max(e, axis=-1, keepdims=True))
        if self.history_only:
            query_len, key_len = K.shape(query)[1], K.shape(key)[1]
            indices = K.tile(K.expand_dims(K.arange(key_len), axis=0), [query_len, 1])
            upper = K.expand_dims(K.arange(key_len), axis=-1)
            e *= K.expand_dims(K.cast(indices <= upper, K.floatx()), axis=0)
        if mask is not None:
            e *= K.cast(K.expand_dims(mask, axis=-2), K.floatx())
        a = e / (K.sum(e, axis=-1, keepdims=True) + K.epsilon())
        v = K.batch_dot(a, value)
        if self.return_attention:
            return [v, a]
        return v 

def call(self, x, mask=None):
        # computes a probability distribution over the timesteps
        # uses 'max trick' for numerical stability
        # reshape is done to avoid issue with Tensorflow
        # and 1-dimensional weights
        logits = K.dot(x, self.W)
        x_shape = K.shape(x)
        logits = K.reshape(logits, (x_shape[0], x_shape[1]))
        ai = K.exp(logits - K.max(logits, axis=-1, keepdims=True))

        # masked timesteps have zero weight
        if mask is not None:
            mask = K.cast(mask, K.floatx())
            ai = ai * mask
        att_weights = ai / (K.sum(ai, axis=1, keepdims=True) + K.epsilon())
        weighted_input = x * K.expand_dims(att_weights)
        result = K.sum(weighted_input, axis=1)
        if self.return_attention:
            return [result, att_weights]
        return result 

def softmax(x, axis=1):
    """Softmax activation function.
    # Arguments
        x : Tensor.
        axis: Integer, axis along which the softmax normalization is applied.
    # Returns
        Tensor, output of softmax transformation.
    # Raises
        ValueError: In case `dim(x) == 1`.
    """
    ndim = K.ndim(x)
    if ndim == 2:
        return K.softmax(x)
    elif ndim > 2:
        e = K.exp(x - K.max(x, axis=axis, keepdims=True))
        s = K.sum(e, axis=axis, keepdims=True)
        return e / s
    else:
        raise ValueError('Cannot apply softmax to a tensor that is 1D') 

def softmax(x, axis=1):
    """Softmax activation function.
    # Arguments
        x : Tensor.
        axis: Integer, axis along which the softmax normalization is applied.
    # Returns
        Tensor, output of softmax transformation.
    # Raises
        ValueError: In case `dim(x) == 1`.
    """
    ndim = K.ndim(x)
    if ndim == 2:
        return K.softmax(x)
    elif ndim > 2:
        e = K.exp(x - K.max(x, axis=axis, keepdims=True))
        s = K.sum(e, axis=axis, keepdims=True)
        return e / s
    else:
        raise ValueError('Cannot apply softmax to a tensor that is 1D') 

def get_batch(self, model, batch_size, gamma=0.9):
        if self.fast:
            return self.get_batch_fast(model, batch_size, gamma)
        if len(self.memory) < batch_size:
            batch_size = len(self.memory)
        nb_actions = model.get_output_shape_at(0)[-1]
        samples = np.array(sample(self.memory, batch_size))
        input_dim = np.prod(self.input_shape)
        S = samples[:, 0 : input_dim]
        a = samples[:, input_dim]
        r = samples[:, input_dim + 1]
        S_prime = samples[:, input_dim + 2 : 2 * input_dim + 2]
        game_over = samples[:, 2 * input_dim + 2]
        r = r.repeat(nb_actions).reshape((batch_size, nb_actions))
        game_over = game_over.repeat(nb_actions).reshape((batch_size, nb_actions))
        S = S.reshape((batch_size, ) + self.input_shape)
        S_prime = S_prime.reshape((batch_size, ) + self.input_shape)
        X = np.concatenate([S, S_prime], axis=0)
        Y = model.predict(X)
        Qsa = np.max(Y[batch_size:], axis=1).repeat(nb_actions).reshape((batch_size, nb_actions))
        delta = np.zeros((batch_size, nb_actions))
        a = np.cast['int'](a)
        delta[np.arange(batch_size), a] = 1
        targets = (1 - delta) * Y[:batch_size] + delta * (r + gamma * (1 - game_over) * Qsa)
        return S, targets 

def set_batch_function(self, model, input_shape, batch_size, nb_actions, gamma):
        input_dim = np.prod(input_shape)
        samples = K.placeholder(shape=(batch_size, input_dim * 2 + 3))
        S = samples[:, 0 : input_dim]
        a = samples[:, input_dim]
        r = samples[:, input_dim + 1]
        S_prime = samples[:, input_dim + 2 : 2 * input_dim + 2]
        game_over = samples[:, 2 * input_dim + 2 : 2 * input_dim + 3]
        r = K.reshape(r, (batch_size, 1))
        r = K.repeat(r, nb_actions)
        r = K.reshape(r, (batch_size, nb_actions))
        game_over = K.repeat(game_over, nb_actions)
        game_over = K.reshape(game_over, (batch_size, nb_actions))
        S = K.reshape(S, (batch_size, ) + input_shape)
        S_prime = K.reshape(S_prime, (batch_size, ) + input_shape)
        X = K.concatenate([S, S_prime], axis=0)
        Y = model(X)
        Qsa = K.max(Y[batch_size:], axis=1)
        Qsa = K.reshape(Qsa, (batch_size, 1))
        Qsa = K.repeat(Qsa, nb_actions)
        Qsa = K.reshape(Qsa, (batch_size, nb_actions))
        delta = K.reshape(self.one_hot(a, nb_actions), (batch_size, nb_actions))
        targets = (1 - delta) * Y[:batch_size] + delta * (r + gamma * (1 - game_over) * Qsa)
        self.batch_function = K.function(inputs=[samples], outputs=[S, targets]) 

def kl_divergence(y_true, y_pred):
    max_y_pred = K.repeat_elements(K.expand_dims(K.repeat_elements(K.expand_dims(K.max(K.max(y_pred, axis=2), axis=2)), 
                                                                   shape_r_out, axis=-1)), shape_c_out, axis=-1)
    y_pred /= max_y_pred

    sum_y_true = K.repeat_elements(K.expand_dims(K.repeat_elements(K.expand_dims(K.sum(K.sum(y_true, axis=2), axis=2)), 
                                                                   shape_r_out, axis=-1)), shape_c_out, axis=-1)
    sum_y_pred = K.repeat_elements(K.expand_dims(K.repeat_elements(K.expand_dims(K.sum(K.sum(y_pred, axis=2), axis=2)), 
                                                                   shape_r_out, axis=-1)), shape_c_out, axis=-1)
    y_true /= (sum_y_true + K.epsilon())
    y_pred /= (sum_y_pred + K.epsilon())

    return 10 * K.sum(K.sum(y_true * K.log((y_true / (y_pred + K.epsilon())) + K.epsilon()), axis=-1), axis=-1)


# Correlation Coefficient Loss 

def nss(y_true, y_pred):
    max_y_pred = K.repeat_elements(K.expand_dims(K.repeat_elements(K.expand_dims(K.max(K.max(y_pred, axis=2), axis=2)), 
                                                                   shape_r_out, axis=-1)), shape_c_out, axis=-1)
    y_pred /= max_y_pred
    y_pred_flatten = K.batch_flatten(y_pred)

    y_mean = K.mean(y_pred_flatten, axis=-1)
    y_mean = K.repeat_elements(K.expand_dims(K.repeat_elements(K.expand_dims(K.expand_dims(y_mean)), 
                                                               shape_r_out, axis=-1)), shape_c_out, axis=-1)

    y_std = K.std(y_pred_flatten, axis=-1)
    y_std = K.repeat_elements(K.expand_dims(K.repeat_elements(K.expand_dims(K.expand_dims(y_std)), 
                                                              shape_r_out, axis=-1)), shape_c_out, axis=-1)

    y_pred = (y_pred - y_mean) / (y_std + K.epsilon())

    return -(K.sum(K.sum(y_true * y_pred, axis=2), axis=2) / K.sum(K.sum(y_true, axis=2), axis=2))


# Gaussian priors initialization 

def softmax(x, axis=-1):
    """
    Self-defined softmax function
    """
    x = K.exp(x - K.max(x, axis=axis, keepdims=True))
    x /= K.sum(x, axis=axis, keepdims=True)
    return x 

def linf_loss(X1, X2):
    return np.max(np.abs(X1 - X2), axis=(1, 2, 3)) 

def linf_loss(X1, X2):
    return np.max(np.abs(X1 - X2), axis=(1, 2, 3)) 

def yolo_filter_boxes(boxes, box_confidence, box_class_probs, threshold=.6):
    """Filter YOLO boxes based on object and class confidence."""
    box_scores = box_confidence * box_class_probs
    box_classes = K.argmax(box_scores, axis=-1)
    box_class_scores = K.max(box_scores, axis=-1)
    prediction_mask = box_class_scores >= threshold

    # TODO: Expose tf.boolean_mask to Keras backend?
    boxes = tf.boolean_mask(boxes, prediction_mask)
    scores = tf.boolean_mask(box_class_scores, prediction_mask)
    classes = tf.boolean_mask(box_classes, prediction_mask)
    return boxes, scores, classes 

def max_1d(X):
    return K.max(X, axis=1) 

def max_1d(X):
    return K.max(X, axis=1) 

def max_1d(X):
    return K.max(X, axis=1) 

def compile_saliency_function(model, activation_layer='conv2d_7'):
    input_image = model.input
    layer_output = model.get_layer(activation_layer).output
    max_output = K.max(layer_output, axis=3)
    saliency = K.gradients(K.sum(max_output), input_image)[0]
    return K.function([input_image, K.learning_phase()], [saliency]) 

def call(self, x, mask=None):
        scaled = self.kernel * x
        max_val = K.max(scaled, axis=self.axis, keepdims=True)
        softmax = K.exp(scaled - max_val)
        weights = softmax / K.sum(softmax, axis=self.axis, keepdims=True)
        return K.sum(x * weights, axis=self.axis, keepdims=False)