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This is a program for computing Wasserstein distances between persistence 
diagrams using the geometric version of auction algorithm.

Accompanying paper: M. Kerber, D. Morozov, A. Nigmetov. Geometry Helps To Compare
Persistence Diagrams (ALENEX 2016,
Bug reports can be sent to "nigmetov EMAIL SIGN tugraz DOT at".

Wasserstein distance $W_{q, p}(X, Y)$ between two persistent diagrams is
the minimum over all perfect matchings between $X$ and $Y$ ( $y(x)$ is the point of $Y$
matched to $x \in X$ ) of the following expression:
$ ( \sum \| x - y(x) \|_p ^ { q } ) ^ { 1 / q} $

# Dependencies

Requires boost 1.58 or higher.
Your compiler must support C++11.

# Usage:

To use a standalone command-line utility wasserstein_dist:

wasserstein_dist file1 file2  [wasserstein degree] [relative error] [internal norm]. 

Parameter wasserstein degree corresponds to $q$, when it tends to infinity,
Wasserstein distance tends to the bottleneck distance.

Parameter internal_p corresponds to p.

Default values: 
wasserstein_degree  = 1.0, 
relative_error = 0.01, 
internal_p = infinity.

Valid values: 
wasserstein_degree must be in $[1.0, \infinity)$, 
relative_error must be positive,
internal_p must be in $[1.0, \infinity]$ (to explicitly set internal_p to $\infinity$, supply inf).By default wasserstein degree is 1.0, relative error is 0.01, internal norm is l_infinity.

file1 and file2 must contain persistence diagrams in plain text format 
(one point per line, empty lines are ignored, comments can be made with #):

# this is how your input can look like
x_1 y_1 # two real numbers per line
# empty lines or comments are ignored
x_n y_n 

To use from your code:

#include "wasserstein.h"

// All classes and functions are in geom_ws namespace

std::vector<std::pair<double, double>> diagram1, diagram2;
// any container class that supports range-for loops will do.
// A pair represents a single point, 
// first component = x-coordinate,
// second component = y-coordinate.
// ...
// load your diagrams into diagram1, diagram2 (off-diagonal points).
// You can use function readDiagramPointSet:
geom_ws::readDiagramPointSet("diagram1.txt", diagram1);
geom_ws::readDiagramPointSet("diagram2.txt", diagram1);
// ...
// to get the distance:
double wsDist = geom_ws::wassersteinDist(diagram1, diagram2, q, delta, p);
// q is wasserstein degree, delta is relative error,
// p is the internal norm in Wasserstein distance, defaults to infinity

Necessary projections (diagonal points) will be added in the wassersteinDist

See also code in wasserstein/example/wasserstein_dist.cpp.

# License

See wasserstein/license.txt

# Building

CMakeLists.txt in the root directory can be used to make the library (contained 
in wasserstein/src/ directory) and the command-line utility (in wasserstein/example/ directory)
to compute the distance between two diagrams in txt files.

On Linux/Mac:

mkdir build
cd build
cmake ..

On Windows (checked with Visual Studio 2015, Community version)
use cmake-gui to create the solution in build directory and build it with VS.