function createBenchmark( len, chart ) {
	var x;
	var r;
	var i;

	x = new Int8Array( len );
	for ( i = 0; i < x.length; i++ ) {
		r = randu();
		if ( r > 0.5 ) {
			x[ i ] = 1;
		} else {
			x[ i ] = -1;
		}
	}
	chart.data = x;
	return benchmark;

	/**
	* Benchmark function.
	*
	* @private
	* @param {Benchmark} b - benchmark instance
	*/
	function benchmark( b ) {
		var str;
		var i;

		b.tic();
		for ( i = 0; i < b.iterations; i++ ) {
			str = chart.push( randu() ).render();
			if ( typeof str !== 'string' ) {
				b.fail( 'should return a string' );
			}
		}
		b.toc();
		if ( typeof str !== 'string' ) {
			b.fail( 'should return a string' );
		}
		b.pass( 'benchmark finished' );
		b.end();
	}
}
Creates a benchmark function.

@private
@param {PositiveInteger} len - array length
@param {UpDownChart} chart - chart instance
@returns {Function} benchmark function