kernels.py 文件源码

def getTrainKernel(self, params):
        self.checkParams(params)
        if (self.sameParams(params)): return self.cache['getTrainKernel']

        ell = np.exp(params[0])
        if (self.K_sq is None): K = sq_dist(self.X_scaled.T / ell)  #precompute squared distances
        else: K = self.K_sq / ell**2        
        self.cache['K_sq_scaled'] = K

        # # # #manual computation (just for sanity checks)
        # # # K1 = np.exp(-K / 2.0)
        # # # K2 = np.zeros((self.X_scaled.shape[0], self.X_scaled.shape[0]))
        # # # for i1 in xrange(self.X_scaled.shape[0]):
            # # # for i2 in xrange(i1, self.X_scaled.shape[0]):
                # # # diff = self.X_scaled[i1,:] - self.X_scaled[i2,:]
                # # # K2[i1, i2] = np.exp(-np.sum(diff**2) / (2*ell))
                # # # K2[i2, i1] = K2[i1, i2]               
        # # # print np.max((K1-K2)**2)
        # # # sys.exit(0)

        K_exp = np.exp(-K / 2.0)
        self.cache['getTrainKernel'] = K_exp
        self.saveParams(params)
        return K_exp