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#!/usr/bin/env python |
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# -*- coding: utf-8 -*- |
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import numpy as np |
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from deepy.utils import global_rand |
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def get_fans(shape): |
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fan_in = shape[0] if len(shape) == 2 else np.prod(shape[1:]) |
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fan_out = shape[1] if len(shape) == 2 else shape[0] |
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return fan_in, fan_out |
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class WeightInitializer(object): |
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""" |
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Initializer for creating weights. |
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""" |
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def __init__(self, seed=None): |
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if not seed: |
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self.rand = global_rand |
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else: |
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self.rand = np.random.RandomState(seed) |
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def sample(self, shape): |
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""" |
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Sample parameters with given shape. |
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""" |
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raise NotImplementedError |
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class UniformInitializer(WeightInitializer): |
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""" |
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Uniform weight sampler. |
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""" |
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def __init__(self, scale=None, svd=False, seed=None): |
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super(UniformInitializer, self).__init__(seed) |
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self.scale = scale |
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self.svd = svd |
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def sample(self, shape): |
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if not self.scale: |
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scale = np.sqrt(6. / sum(get_fans(shape))) |
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else: |
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scale = self.scale |
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weight = self.rand.uniform(-1, 1, size=shape) * scale |
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if self.svd: |
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norm = np.sqrt((weight**2).sum()) |
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ws = scale * weight / norm |
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_, v, _ = np.linalg.svd(ws) |
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ws = scale * ws / v[0] |
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return weight |
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class GaussianInitializer(WeightInitializer): |
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""" |
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Gaussian weight sampler. |
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""" |
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def __init__(self, mean=0, deviation=0.01, seed=None): |
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super(GaussianInitializer, self).__init__(seed) |
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self.mean = mean |
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self.deviation = deviation |
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def sample(self, shape): |
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weight = self.rand.normal(self.mean, self.deviation, size=shape) |
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return weight |
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class IdentityInitializer(WeightInitializer): |
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""" |
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Initialize weight as identity matrices. |
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""" |
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def __init__(self, scale=1): |
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super(IdentityInitializer, self).__init__() |
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self.scale = 1 |
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def sample(self, shape): |
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assert len(shape) == 2 |
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return np.eye(*shape) * self.scale |
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class XavierGlorotInitializer(WeightInitializer): |
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""" |
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Xavier Glorot's weight initializer. |
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See http://jmlr.org/proceedings/papers/v9/glorot10a/glorot10a.pdf |
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""" |
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def __init__(self, uniform=False, seed=None): |
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""" |
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Parameters: |
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uniform - uniform distribution, default Gaussian |
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seed - random seed |
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""" |
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super(XavierGlorotInitializer, self).__init__(seed) |
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self.uniform = uniform |
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def sample(self, shape): |
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scale = np.sqrt(2. / sum(get_fans(shape))) |
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if self.uniform: |
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return self.rand.uniform(-1, 1, size=shape) * scale |
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else: |
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return self.rand.randn(*shape) * scale |
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class KaimingHeInitializer(WeightInitializer): |
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""" |
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Kaiming He's initialization scheme, especially made for ReLU. |
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See http://arxiv.org/abs/1502.01852. |
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""" |
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def __init__(self, uniform=False, seed=None): |
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""" |
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Parameters: |
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uniform - uniform distribution, default Gaussian |
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seed - random seed |
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""" |
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super(KaimingHeInitializer, self).__init__(seed) |
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self.uniform = uniform |
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def sample(self, shape): |
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fan_in, fan_out = get_fans(shape) |
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scale = np.sqrt(2. / fan_in) |
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if self.uniform: |
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return self.rand.uniform(-1, 1, size=shape) * scale |
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else: |
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return self.rand.randn(*shape) * scale |
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class OrthogonalInitializer(WeightInitializer): |
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""" |
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Orthogonal weight initializer. |
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""" |
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def __init__(self, scale=1.1, seed=None): |
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""" |
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Parameters: |
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scale - scale |
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seed - random seed |
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""" |
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super(OrthogonalInitializer, self).__init__(seed) |
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self.scale = scale |
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def sample(self, shape): |
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flat_shape = (shape[0], np.prod(shape[1:])) |
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a = np.random.normal(0.0, 1.0, flat_shape) |
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u, _, v = np.linalg.svd(a, full_matrices=False) |
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q = u if u.shape == flat_shape else v |
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q = q.reshape(shape) |
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return self.scale * q[:shape[0], :shape[1]] |
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zomux /
deepy
