Source code for infpy.gp.pre_calculated_kernel

#
# Copyright John Reid 2006
#


from kernel import *
import numpy

class PreCalculatedKernel( Kernel ):
    """A kernel that has been pre-computed"""

    def __init__(
            self,
            objects,
            matrix
    ):
        """objects: The objects that we have pre-computed the kernel on
        matrix: The kernel values
        """
        self.objects = objects
        self.matrix = numpy.array( matrix, copy = True )
        if len( self.matrix.shape ) != 2:
            raise RuntimeError( 'Kernel must be of rank 2' )
        if self.matrix.shape[0] != self.matrix.shape[1]:
            raise RuntimeError( 'Kernel must be square' )
        if self.matrix.shape[0] != len( objects ):
            raise RuntimeError( 'Kernel must be of same size as objects' )
        self.indices = dict(
                [
                        ( o, i )
                        for i, o in enumerate( objects )
                ]
        )
        Kernel.__init__( self, [], [] )

    def __str__( self ):
        return """PreCalculatedKernel"""

    def __call__( self, x1, x2, identical = False ):
        if identical and x1 != x2: raise RuntimeError( 'x1 and x2 should be identical' )
        return self.matrix[
                self.indices[ x1 ],
                self.indices[ x2 ]
        ]