refactoring files added

GPy/core/gp.py

@@ -0,0 +1,150 @@
+# Copyright (c) 2012, GPy authors (see AUTHORS.txt).
+# Licensed under the BSD 3-clause license (see LICENSE.txt)
+
+
+import numpy as np
+from scipy import linalg
+import pylab as pb
+from .. import kern
+from ..util.linalg import pdinv, mdot, tdot
+#from ..util.plot import gpplot,  Tango
+from ..likelihoods import EP
+from gp_base import GPBase
+
+class GP(GPBase):
+    """
+    Gaussian Process model for regression and EP
+
+    :param X: input observations
+    :param kernel: a GPy kernel, defaults to rbf+white
+    :parm likelihood: a GPy likelihood
+    :param normalize_X:  whether to normalize the input data before computing (predictions will be in original scales)
+    :type normalize_X: False|True
+    :rtype: model object
+    :param epsilon_ep: convergence criterion for the Expectation Propagation algorithm, defaults to 0.1
+    :param powerep: power-EP parameters [$\eta$,$\delta$], defaults to [1.,1.]
+    :type powerep: list
+
+    .. Note:: Multiple independent outputs are allowed using columns of Y
+
+    """
+    def __init__(self, X, likelihood, kernel, normalize_X=False):
+        GPBase.__init__(self, X, likelihood, kernel, normalize_X=normalize_X)
+        self._set_params(self._get_params())
+
+    def _set_params(self, p):
+        self.kern._set_params_transformed(p[:self.kern.Nparam_transformed()])
+        self.likelihood._set_params(p[self.kern.Nparam_transformed():])
+
+        self.K = self.kern.K(self.X)
+        self.K += self.likelihood.covariance_matrix
+
+        self.Ki, self.L, self.Li, self.K_logdet = pdinv(self.K)
+
+        # the gradient of the likelihood wrt the covariance matrix
+        if self.likelihood.YYT is None:
+            #alpha = np.dot(self.Ki, self.likelihood.Y)
+            alpha,_ = linalg.lapack.flapack.dpotrs(self.L, self.likelihood.Y,lower=1)
+
+            self.dL_dK = 0.5 * (tdot(alpha) - self.input_dim * self.Ki)
+        else:
+            #tmp = mdot(self.Ki, self.likelihood.YYT, self.Ki)
+            tmp, _ = linalg.lapack.flapack.dpotrs(self.L, np.asfortranarray(self.likelihood.YYT), lower=1)
+            tmp, _ = linalg.lapack.flapack.dpotrs(self.L, np.asfortranarray(tmp.T), lower=1)
+            self.dL_dK = 0.5 * (tmp - self.input_dim * self.Ki)
+
+    def _get_params(self):
+        return np.hstack((self.kern._get_params_transformed(), self.likelihood._get_params()))
+
+
+    def _get_param_names(self):
+        return self.kern._get_param_names_transformed() + self.likelihood._get_param_names()
+
+    def update_likelihood_approximation(self):
+        """
+        Approximates a non-gaussian likelihood using Expectation Propagation
+
+        For a Gaussian likelihood, no iteration is required:
+        this function does nothing
+        """
+        self.likelihood.fit_full(self.kern.K(self.X))
+        self._set_params(self._get_params())  # update the GP
+
+    def _model_fit_term(self):
+        """
+        Computes the model fit using YYT if it's available
+        """
+        if self.likelihood.YYT is None:
+            tmp, _ = linalg.lapack.flapack.dtrtrs(self.L, np.asfortranarray(self.likelihood.Y), lower=1)
+            return -0.5 * np.sum(np.square(tmp))
+            #return -0.5 * np.sum(np.square(np.dot(self.Li, self.likelihood.Y)))
+        else:
+            return -0.5 * np.sum(np.multiply(self.Ki, self.likelihood.YYT))
+
+    def log_likelihood(self):
+        """
+        The log marginal likelihood of the GP.
+
+        For an EP model,  can be written as the log likelihood of a regression
+        model for a new variable Y* = v_tilde/tau_tilde, with a covariance
+        matrix K* = K + diag(1./tau_tilde) plus a normalization term.
+        """
+        return -0.5 * self.input_dim * self.K_logdet + self._model_fit_term() + self.likelihood.Z
+
+
+    def _log_likelihood_gradients(self):
+        """
+        The gradient of all parameters.
+
+        Note, we use the chain rule: dL_dtheta = dL_dK * d_K_dtheta
+        """
+        return np.hstack((self.kern.dK_dtheta(dL_dK=self.dL_dK, X=self.X), self.likelihood._gradients(partial=np.diag(self.dL_dK))))
+
+    def _raw_predict(self, _Xnew, which_parts='all', full_cov=False,stop=False):
+        """
+        Internal helper function for making predictions, does not account
+        for normalization or likelihood
+        """
+        Kx = self.kern.K(_Xnew,self.X,which_parts=which_parts).T
+        #KiKx = np.dot(self.Ki, Kx)
+        KiKx, _ = linalg.lapack.flapack.dpotrs(self.L, np.asfortranarray(Kx), lower=1)
+        mu = np.dot(KiKx.T, self.likelihood.Y)
+        if full_cov:
+            Kxx = self.kern.K(_Xnew, which_parts=which_parts)
+            var = Kxx - np.dot(KiKx.T, Kx)
+        else:
+            Kxx = self.kern.Kdiag(_Xnew, which_parts=which_parts)
+            var = Kxx - np.sum(np.multiply(KiKx, Kx), 0)
+            var = var[:, None]
+        if stop:
+            debug_this # @UndefinedVariable
+        return mu, var
+
+    def predict(self, Xnew, which_parts='all', full_cov=False):
+        """
+        Predict the function(s) at the new point(s) Xnew.
+        Arguments
+        ---------
+        :param Xnew: The points at which to make a prediction
+        :type Xnew: np.ndarray, Nnew x self.input_dim
+        :param which_parts:  specifies which outputs kernel(s) to use in prediction
+        :type which_parts: ('all', list of bools)
+        :param full_cov: whether to return the folll covariance matrix, or just the diagonal
+        :type full_cov: bool
+        :rtype: posterior mean,  a Numpy array, Nnew x self.input_dim
+        :rtype: posterior variance, a Numpy array, Nnew x 1 if full_cov=False, Nnew x Nnew otherwise
+        :rtype: lower and upper boundaries of the 95% confidence intervals, Numpy arrays,  Nnew x self.input_dim
+
+
+           If full_cov and self.input_dim > 1, the return shape of var is Nnew x Nnew x self.input_dim. If self.input_dim == 1, the return shape is Nnew x Nnew.
+           This is to allow for different normalizations of the output dimensions.
+
+        """
+        # normalize X values
+        Xnew = (Xnew.copy() - self._Xmean) / self._Xstd
+        mu, var = self._raw_predict(Xnew, full_cov=full_cov, which_parts=which_parts)
+
+        # now push through likelihood
+        mean, var, _025pm, _975pm = self.likelihood.predictive_values(mu, var, full_cov)
+
+        return mean, var, _025pm, _975pm