function createBenchmark( len, xtype ) {
	var strides;
	var arrays;
	var shape;
	var x;

	x = filledarray( 0.0, len, xtype );
	arrays = [ x ];
	shape = [ len ];
	strides = [ 1 ];

	return benchmark;

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

		b.tic();
		for ( i = 0; i < b.iterations; i++ ) {
			nullary( arrays, shape, strides, constantFunction( i+1 ) );
			if ( isnan( x[ i%len ] ) ) {
				b.fail( 'should not return NaN' );
			}
		}
		b.toc();
		if ( isnan( arrays[ 0 ][ i%len ] ) ) {
			b.fail( 'should not return NaN' );
		}
		b.pass( 'benchmark finished' );
		b.end();
	}
}
Creates a benchmark function.

@private
@param {PositiveInteger} len - array length
@param {string} xtype - output array data type
@returns {Function} benchmark function