mergesort count comparisons

gistfile1.js

__mergesort__ = require( "./sort/mergesort.js").__mergesort__

tapemerge = require("./merge/tapemerge.js").tapemerge

mergesort = __mergesort__(tapemerge)

asc = function ( a , b ) { return a < b ? -1 : a > b ? 1 : 0 ; }

gen = function ( n ) { var a = [] ; var i = n ; while ( i-- ) { a.push(Math.random()) } ; return a ; }

copy = function ( a ) { return a.slice() }

comparator = function ( compare ) { var count = 0 ; var compare2 = function ( a , b ) { ++count ; return compare ( a , b ) }; compare2.count = function ( ) { return count } ; return compare2 ; }

test = function ( n ) { var a = gen( n ) ; var b = copy( a ) ; var compare = comparator(asc) ; mergesort( compare , a , 0,n,b,0,n) ; return compare.count() ; }

nlogn = function ( n ) { return n * Math.log( n ) / Math.log( 2 ) }

average = function ( n , m ) { var i = m ; var c = 0 ; while ( i-- ) { c += test( n ) ; } return c / m / nlogn(n) ; }