NAME

get_earthmover_distance - Computes the earthmover's distance.

SYNOPSIS

#include "lsm/lsm_emd.h"

Example compile flags (system dependent):
  -DLINUX_X86_64 -DLINUX_X86_64_OPTERON  -DGNU_COMPILER 
   -I/home/kobus/include
   -L/home/kobus/misc/load/linux_x86_64_opteron -L/usr/lib/x86_64-linux-gnu
  -lKJB                               -lfftw3  -lgsl -lgslcblas -ljpeg  -lSVM -lstdc++                    -lpthread -lSLATEC -lg2c    -lacml -lacml_mv -lblas -lg2c      -lncursesw 


int get_earthmover_distance
(
	Signature *sig1,
	Signature *sig2,
	int (*distance_fn)(Vector *,Vector *,double *),
	Flow *flow_vec,
	int *num_flows_ptr,
	double *em_distance_ptr
);

PARAMETERS

Signature *sig1: First input signature
Signature *sig2: Second input signature
Flow *flow_vec: Output array of flows
int *num_flows_ptr: Number of valid flows
double *em_distance_ptr: Earthmover's Distance

DESCRIPTION

This routine computes the earthmover's distance between two distributions. Distributions are stored in "signatures" which consist of an array of "features" and a corresponding array of feature weights. In the emd_lib.c module, a "feature" is simply a "Vector". A "signature" is defined as follows: | typedef struct Signature

    {
        int      num_features; Number of features in the signature
        Vector** feature_vec;  Pointer to array of features
        double*    weights_vec;  Pointer to array of feature weights
    } Signature;

Each feature in a signature has a corresponding weight indicating its relative abundance in the distribution. A distance function must be supplied that computes the distance between two features. A function that computes the Euclidean distance between two features as defined above is provided: See the "distance" function. This routine will optionally return the flow that was required to map one input distribution to the other. If "flow_vec" is NULL, then no flow is computed. If output flows are required, then "flow_vec" must be preallocated, and contain n1 + n2 - 1 elements, where n1 and n2 are the numbers of elements in the two input signatures. Note that the earthmover's distance is a true metric ONLY when the two input signatures are the same size. Uses code written by Yosi Rubner. See http://vision.stanford.edu/~rubner

RETURNS

Either NO_ERROR, or ERROR, with an appropriate error message being set.

DISCLAIMER

This software is not adequatedly tested. It is recomended that results are checked independantly where appropriate.

AUTHOR

Yossi Rubner, Lindsay Martin

DOCUMENTER

Lindsay Martin