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import Heap from '../../heap';
import * as util from '../../util';
const defaults = util.defaults({
weight: null,
directed: false
});
let elesfn = ({
// Implemented from the algorithm in the paper "On Variants of Shortest-Path Betweenness Centrality and their Generic Computation" by Ulrik Brandes
betweennessCentrality: function( options ){
let { directed, weight } = defaults(options);
let weighted = weight != null;
let cy = this.cy();
// starting
let V = this.nodes();
let A = {};
let _C = {};
let max = 0;
let C = {
set: function( key, val ){
_C[ key ] = val;
if( val > max ){ max = val; }
},
get: function( key ){ return _C[ key ]; }
};
// A contains the neighborhoods of every node
for( let i = 0; i < V.length; i++ ){
let v = V[ i ];
let vid = v.id();
if( directed ){
A[ vid ] = v.outgoers().nodes(); // get outgoers of every node
} else {
A[ vid ] = v.openNeighborhood().nodes(); // get neighbors of every node
}
C.set( vid, 0 );
}
for( let s = 0; s < V.length; s++ ){
let sid = V[s].id();
let S = []; // stack
let P = {};
let g = {};
let d = {};
let Q = new Heap(function( a, b ){
return d[a] - d[b];
}); // queue
// init dictionaries
for( let i = 0; i < V.length; i++ ){
let vid = V[ i ].id();
P[ vid ] = [];
g[ vid ] = 0;
d[ vid ] = Infinity;
}
g[ sid ] = 1; // sigma
d[ sid ] = 0; // distance to s
Q.push( sid );
while( !Q.empty() ){
let v = Q.pop();
S.push( v );
if( weighted ){
for( let j = 0; j < A[v].length; j++ ){
let w = A[v][j];
let vEle = cy.getElementById( v );
let edge;
if( vEle.edgesTo( w ).length > 0 ){
edge = vEle.edgesTo( w )[0];
} else {
edge = w.edgesTo( vEle )[0];
}
let edgeWeight = weight( edge );
w = w.id();
if( d[w] > d[v] + edgeWeight ){
d[w] = d[v] + edgeWeight;
if( Q.nodes.indexOf( w ) < 0 ){ //if w is not in Q
Q.push( w );
} else { // update position if w is in Q
Q.updateItem( w );
}
g[w] = 0;
P[w] = [];
}
if( d[w] == d[v] + edgeWeight ){
g[w] = g[w] + g[v];
P[w].push( v );
}
}
} else {
for( let j = 0; j < A[v].length; j++ ){
let w = A[v][j].id();
if( d[w] == Infinity ){
Q.push( w );
d[w] = d[v] + 1;
}
if( d[w] == d[v] + 1 ){
g[w] = g[w] + g[v];
P[w].push( v );
}
}
}
}
let e = {};
for( let i = 0; i < V.length; i++ ){
e[ V[ i ].id() ] = 0;
}
while( S.length > 0 ){
let w = S.pop();
for( let j = 0; j < P[w].length; j++ ){
let v = P[w][j];
e[v] = e[v] + (g[v] / g[w]) * (1 + e[w]);
}
if( w != V[s].id() ){
C.set( w, C.get( w ) + e[w] );
}
}
}
let ret = {
betweenness: function( node ){
let id = cy.collection(node).id();
return C.get( id );
},
betweennessNormalized: function( node ){
if ( max == 0 ){ return 0; }
let id = cy.collection(node).id();
return C.get( id ) / max;
}
};
// alias
ret.betweennessNormalised = ret.betweennessNormalized;
return ret;
} // betweennessCentrality
}); // elesfn
// nice, short mathematical alias
elesfn.bc = elesfn.betweennessCentrality;
export default elesfn;
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