Python tensor.log函数代码示例

 def cross_entropy(self, y):
     
     #return (-(y * T.log(self.y) + (1.0 - y) * T.log(1.0 - self.y))).mean()
     #return T.nnet.binary_crossentropy(self.y, y).mean()
      y_used = self.y
      y_used = T.clip(self.y, 0.0000001, 0.999999999)
      return T.mean(-y * T.log(y_used) - (1 - y) * T.log(1 - y_used))

    def compileFunctions(self, x_image_global, examples, ib, B, K, corrupt):
        if x_image_global == None:
            x_image_global = self.x

        if corrupt == 0.0:
            self.x_c = self.x
        else:
            self.x_c = self.theano_rng.binomial(
                size=self.x.shape, n=1, p=1-corrupt,
                dtype=theano.config.floatX) * self.x

        self.h = self.g(T.dot(self.x_c, self.W_hl) + self.b_hl)
        self.x_r = self.o(T.dot(self.h, self.W_ol) + self.b_ol)
        self.params = [self.W_hl, self.b_hl, self.b_ol]
        self.cost = \
            (- T.sum(
                self.x * T.log(self.x_r) + (1 - self.x) * T.log(1 - self.x_r),
                axis=(0,1)))

        gparams = T.grad(self.cost, self.params)
        updates = [
            (param, param - K * gparam)
            for param, gparam in zip(self.params, gparams)
        ]

        fun_train = theano.function(
            inputs=[ib],
            outputs=(self.cost, self.x_r, self.x_c),
            updates=updates,
            givens={
                x_image_global: examples[ib*B: (ib+1)*B]
            }
        )

        return fun_train

    def get_reconstruction_cost(self, updates, pre_sigmoid_nv):
        """ Approximation to the recontruction error

        Note that this function requires the pre-sigmoid actiavtion as input. To
        undertstand why this is so you need to understand a bit about how Theano works.
        Whenever you compile a Theano function, the computational graph that you pass as input
        gets optimized for speed and stability. This is done by changing several parts of
        the subgraphs with others. One such optimization expresses terms of softplus. We need this
        optimizations for the cross-entropy since sigmoid of numbers larger than 30. (or even less
        then that) return to 1. and numbers of smaller than -30, turn to 0 which ini terms will force
        theano to compute log(0) and thereforce we will get either -inf or NaN as cost. If the value is
        expressed in terms of softplus we do not get this undersirable behaviour. This optimiation usually
        works fine, but here we have a special case. The sigmoid is applied inside the scan op, while
        the log is outisde. Therefore Theano will only see log(scan(...)) instead of log(sigmoid(..))
        and will not apply the wanted optimization. We can not go and replace the sigmoid in scan
        with something else alse, because this only needs to be done on the last step. Therefore the
        easiest adn more efficient way is to get also teh pre-sigmoid activation as an output of
        scan, and apply both the log and sigmoid outside scan sunch that Theano can catch and optimize
        the expression.
        """

        cross_entropy = T.mean(
            T.sum(
                self.input * T.log(T.nnet.sigmoid(pre_sigmoid_nv)) +
                ( 1 - self.input) * T.log(1 - T.nnet.sigmoid(pre_sigmoid_nv)),
                axis=1
            )
        )

        return  cross_entropy

 def logp(self, value):
     alpha = self.alpha
     beta = self.beta
     return bound(T.log(alpha) - T.log(beta)
                  + (alpha - 1) * T.log(value/beta)
                  - (value/beta)**alpha,
                  value >= 0, alpha > 0, beta > 0)

def _elbo_t(logp, uw, inarray, n_mcsamples, random_seed):
    """Create Theano tensor of approximate ELBO by Monte Carlo sampling.
    """
    l = (uw.size / 2)
    l_int = l.astype('int64')
    u = uw[:l_int]
    w = uw[l_int:]

    # Callable tensor
    def logp_(input):
        return theano.clone(logp, {inarray: input}, strict=False)

    # Naive Monte-Carlo
    if random_seed is None:
        r = MRG_RandomStreams(gen_random_state())
    else:
        r = MRG_RandomStreams(seed=random_seed)

    if n_mcsamples == 1:
        n = r.normal(size=inarray.tag.test_value.shape)
        q = n * tt.exp(w) + u
        elbo = logp_(q) + tt.sum(w) + 0.5 * l * (1 + tt.log(2.0 * np.pi))
    else:
        n = r.normal(size=(n_mcsamples, u.tag.test_value.shape[0]))
        qs = n * tt.exp(w) + u
        logps, _ = theano.scan(fn=lambda q: logp_(q),
                               outputs_info=None,
                               sequences=[qs])
        elbo = tt.mean(logps) + tt.sum(w) + 0.5 * l * (1 + tt.log(2.0 * np.pi))

    return elbo

def get_model(Ws, bs, dropout=False):
    v = T.matrix('input')
    m = T.matrix('missing')
    q = T.matrix('target')
    k = T.vector('normalization factor')

    # Set all missing/target values to 0.5
    keep_mask = (1-m) * (1-q)
    h = keep_mask * (v * 2 - 1) # Convert to +1, -1
    
    # Normalize layer 0
    h *= k.dimshuffle(0, 'x')

    for l in xrange(len(Ws)):
        h = T.dot(h, Ws[l]) + bs[l]

        if l < len(Ws) - 1:
            h = h * (h > 0) # relu
            if dropout:
                mask = srng.binomial(n=1, p=0.5, size=h.shape)
                h = h * mask * 2

    output = sigmoid(h)
    LL = v * T.log(output) + (1 - v) * T.log(1 - output)
    # loss = -(q * LL).sum() / q.sum()
    loss = -((1 - m) * LL).sum() / (1 - m).sum()

    return v, m, q, k, output, loss

    def get_cost(self, p=0, sigma=1):
        # the last layer    
        z = self.sigmoid_layers[-1].output
        L = -T.sum(self.x * T.log(z) + (1 - self.x) * T.log(1 - z), axis=1)
        p_idx = len(self.sigmoid_layers)/2 - 1 #penalty layer, the middle layer        
        if p == 0:
            cost = T.mean(L)
#             cost = T.mean(T.sqrt(T.mean(self.errors, axis=1))) #Log Spectral Distance(LSD)
        elif (p != 0) and (sigma == 0):# for square penalty
            square_cost = self.get_square_cost(self.sigmoid_layers[p_idx].output, p)
            cost = T.mean(L) + T.mean(square_cost)
        elif(p != 0) and (sigma != 0):# for Gaussian penalty
            gaussian_cost = self.get_gaussian_cost(self.sigmoid_layers[p_idx].output, p, sigma)
            cost = T.mean(L) + T.mean(gaussian_cost)
#         elif(p == -1) and (sigma == 0):#binary
#             code_val = self.sigmoid_layers[p_idx].output
#             binary_val = code_val>=0.5
#             self.sigmoid_layers[p_idx+1].input = binary_val
#             z = self.sigmoid_layers[-1].output
#             L = -T.sum(self.x * T.log(z) + (1 - self.x) * T.log(1 - z), axis=1)
#             cost = T.mean(L)
#         elif(p == -1) and (sigma != 0):#add gaussian noise
#             gaussian_data = self.theano_rng.normal(size=self.sigmoid_layers[p_idx-1].output.shape, std=sigma,
#                                                    dtype=theano.config.floatX)
#             self.sigmoid_layers[p_idx].input = self.sigmoid_layers[p_idx-1].output + gaussian_data
#             z = self.sigmoid_layers[-1].output
#             L = -T.sum(self.x * T.log(z) + (1 - self.x) * T.log(1 - z), axis=1)
#             cost = T.mean(L)
        else:
            cost = T.mean(L)
        return cost

    def negative_log_likelihood(self, y):
        """ Return the mean of the negative log-likelihood of the prediction
        of this model under a given target distribution.

        .. math::
            \frac{1}{|\mathcal{D}|} \mathcal{L} (\theta=\{W,b\}, \mathcal{D}) =
            \frac{1}{|\mathcal{D}|} \sum_{i=0}^{|\mathcal{D}|} \log(P(Y=y^{(i)}|x^{(i)}, W,b)) \\
                    \ell (\theta=\{W,b\}, \mathcal{D})

        :type y: theano.tensor.TensorType
        :param y: corresponds to a vector that gives for each example the
                  correct label
        Note: we use the mean instead of the sum so that
              the learning rate is less dependent on the batch size
        """

        # y.shape[0] is (symbolically) the number of rows in y, i.e.,
        # number of examples (call it n) in the minibatch
        # T.arange(y.shape[0]) is a symbolic vector which will contain
        # [0,1,2,... n-1] T.log(self.p_y_given_x) is a matrix of
        # Log-Probabilities (call it LP) with one row per example and
        # one column per class LP[T.arange(y.shape[0]),y] is a vector
        # v containing [LP[0,y[0]], LP[1,y[1]], LP[2,y[2]], ...,
        # LP[n-1,y[n-1]]] and T.mean(LP[T.arange(y.shape[0]),y]) is
        # the mean (across minibatch examples) of the elements in v,
        # i.e., the mean log-likelihood across the minibatch.
        if self.is_binary:
            -T.mean(T.log(self.p_y_given_x))
        return -T.mean(T.log(self.p_y_given_x)[T.arange(y.shape[0]), y])

    def get_sparsity_cost(self):

        # update mean activation using exponential moving average
        hack_h = self.h_given_v(self.sp_pos_v)

        # define loss based on value of sp_type
        if self.sp_type == 'kl':
            eps = npy_floatX(1./self.batch_size)
            loss = lambda targ, val: - npy_floatX(targ) * T.log(eps + val) \
                                     - npy_floatX(1-targ) * T.log(1 - val + eps)
        else:
            raise NotImplementedError('Sparsity type %s is not implemented' % self.sp_type)

        cost = T.zeros((), dtype=floatX)

        params = []
        if self.sp_weight['h']: 
            cost += self.sp_weight['h']  * T.sum(loss(self.sp_targ['h'], hack_h.mean(axis=0)))
            params += [self.hbias]

        if self.sp_type in ['kl'] and self.sp_weight['h']:
            params += [self.Wv, self.alpha, self.mu]
            if self.flags['split_norm']:
                params += [self.scalar_norms]

        return costmod.Cost(cost, params)

def simple_RNN(nh):
  Wx = theano.shared(0.2 * numpy.random.uniform(-1.0, 1.0, (1, nh)).astype(theano.config.floatX))
  Wh = theano.shared(0.2 * numpy.random.uniform(-1.0, 1.0, (nh, nh)).astype(theano.config.floatX))
  Wy = theano.shared(0.2 * numpy.random.uniform(-1.0, 1.0, (nh, 1)).astype(theano.config.floatX))
  bh = theano.shared(numpy.zeros(nh, dtype=theano.config.floatX))
  by = theano.shared(numpy.zeros(1, dtype=theano.config.floatX))
  h0 = theano.shared(numpy.zeros(nh, dtype=theano.config.floatX))
  p = [Wx, Wh, Wy, bh, by, h0]

  x = T.matrix()

  def recurrence(x_t, h_tm1):
    h_t = T.tanh(T.dot(x_t, Wx) + T.dot(h_tm1, Wh) + bh)
    s_t = T.dot(h_t, Wy) + by
    return [h_t, s_t]

  ([h, activations], updates) = theano.scan(fn=recurrence, sequences=x, outputs_info=[h0, dict()])

  t = x[0, 0]
  s = activations[-1, 0]
  y = T.nnet.sigmoid(s)
  loss = -t*T.log(y + 1e-14) - (1-t)*T.log((1-y) + 1e-14)
  acc = T.neq(T.round(y), t)
  
  return p, [x], s, [loss, acc], h

    def get_cost_updates(self, contraction_level, learning_rate, cost_measure="cross_entropy"):
        """ This function computes the cost and the updates for one trainng
        step of the cA """

        y = self.get_hidden_values(self.x)
        z = self.get_reconstructed_input(y)
        J = self.get_jacobian(y, self.W)

        if cost_measure=="cross_entropy":
            #self.L_rec = - T.sum(self.x * T.log(z) + (1 - self.x) * T.log(1 - z), axis=1)
            self.L_rec = T.mean(- T.sum(self.x * T.log(z) + (1 - self.x) * T.log(1 - z),axis=1))
        elif cost_measure=="euclidean":
            self.L_rec = T.mean(T.sum((self.x-z)**2,axis=1)) 
            
        # Compute the jacobian and average over the number of samples/minibatch
        self.L_jacob = T.mean(T.sum(J ** 2) / self.n_batchsize)
        
        cost = self.L_rec + contraction_level * self.L_jacob

        # compute the gradients of the cost of the `cA` with respect
        # to its parameters
        gparams = T.grad(cost, self.params)
        # generate the list of updates
        updates = []
        for param, gparam in zip(self.params, gparams):
            updates.append((param, param - learning_rate * gparam))

        return (cost, updates)

 def forward_jacobian_log_det(self, x):
     y_sum = self.forward_map(x).sum()
     dy_dx = th.grad(y_sum, x)
     if self.fudge != 0.:
         return tt.log(dy_dx + self.fudge).sum()
     else:
         return tt.log(dy_dx).sum()

def GMM(y, mu, sig, coeff):
    """
    Gaussian mixture model negative log-likelihood
    Parameters
    ----------
    y     : TensorVariable
    mu    : FullyConnected (Linear)
    sig   : FullyConnected (Softplus)
    coeff : FullyConnected (Softmax)
    """

    n_dim = y.ndim
    shape_y = y.shape
    y = y.reshape((-1, shape_y[-1]))
    y = y.dimshuffle(0, 1, "x")

    mu = mu.reshape((-1, mu.shape[-1] / coeff.shape[-1], coeff.shape[-1]))
    sig = sig.reshape((-1, sig.shape[-1] / coeff.shape[-1], coeff.shape[-1]))
    coeff = coeff.reshape((-1, coeff.shape[-1]))

    inner = -0.5 * T.sum(T.sqr(y - mu) / sig ** 2 + 2 * T.log(sig) + T.log(2 * np.pi), axis=-2)

    nll = -logsumexp(T.log(coeff) + inner, axis=-1)

    # Adjust dimension
    new_dim = T.set_subtensor(shape_y[-1], 1)

    nll = nll.reshape(new_dim, ndim=n_dim)
    nll = nll.flatten(n_dim - 1)

    return nll

    def test_log1msigm_to_softplus(self):
        x = T.matrix()

        out = T.log(1 - sigmoid(x))
        f = theano.function([x], out, mode=self.m)
        topo = f.maker.fgraph.toposort()
        assert len(topo) == 2
        assert isinstance(topo[0].op.scalar_op,
                          theano.tensor.nnet.sigm.ScalarSoftplus)
        assert isinstance(topo[1].op.scalar_op, theano.scalar.Neg)
        f(numpy.random.rand(54, 11).astype(config.floatX))

        # Same test with a flatten
        out = T.log(1 - T.flatten(sigmoid(x)))
        f = theano.function([x], out, mode=self.m)
        topo = f.maker.fgraph.toposort()
        assert len(topo) == 3
        assert isinstance(topo[0].op, T.Flatten)
        assert isinstance(topo[1].op.scalar_op,
                          theano.tensor.nnet.sigm.ScalarSoftplus)
        assert isinstance(topo[2].op.scalar_op, theano.scalar.Neg)
        f(numpy.random.rand(54, 11).astype(config.floatX))

        # Same test with a reshape
        out = T.log(1 - sigmoid(x).reshape([x.size]))
        f = theano.function([x], out, mode=self.m)
        topo = f.maker.fgraph.toposort()
        #assert len(topo) == 3
        assert any(isinstance(node.op, T.Reshape) for node in topo)
        assert any(isinstance(getattr(node.op, 'scalar_op', None),
                              theano.tensor.nnet.sigm.ScalarSoftplus)
                   for node in topo)
        f(numpy.random.rand(54, 11).astype(config.floatX))

def unet_crossentropy_loss_sampled(y_true, y_pred):
    print 'unet_crossentropy_loss_sampled'
    epsilon = 1.0e-4
    y_pred_clipped = T.flatten(T.clip(y_pred, epsilon, 1.0-epsilon))
    y_true = T.flatten(y_true)
    # this seems to work
    # it is super ugly though and I am sure there is a better way to do it
    # but I am struggling with theano to cooperate
    # filter the right indices
    indPos = T.nonzero(y_true)[0] # no idea why this is a tuple
    indNeg = T.nonzero(1-y_true)[0]
    # shuffle
    n = indPos.shape[0]
    indPos = indPos[srng.permutation(n=n)]
    n = indNeg.shape[0]
    indNeg = indNeg[srng.permutation(n=n)]
    # take equal number of samples depending on which class has less
    n_samples = T.cast(T.min([T.sum(y_true), T.sum(1-y_true)]), dtype='int64')

    indPos = indPos[:n_samples]
    indNeg = indNeg[:n_samples]
    loss_vector = -T.mean(T.log(y_pred_clipped[indPos])) - T.mean(T.log(1-y_pred_clipped[indNeg]))
    average_loss = T.mean(loss_vector)
    print 'average_loss:', average_loss
    return average_loss