function iterations( name, options, benchmark, clbk ) {
	var opts;
	var time;

	// Elapsed time (in seconds):
	time = 0;

	// Create a local copy:
	opts = copy( options );
	opts.iterations = ITERATIONS;

	// Begin running benchmarks:
	return next();

	/**
	* Run a new benchmark.
	*
	* @private
	*/
	function next() {
		var b = new Benchmark( name, opts, benchmark );
		b.on( 'result', onResult );
		b.once( 'end', onEnd );
		b.run();
	}

	/**
	* Callback invoked upon a `result` event.
	*
	* @private
	* @param {(string|Object)} result - result
	*/
	function onResult( result ) {
		if ( !isString( result ) && result.operator === 'result' ) {
			time = result.elapsed;
		}
	}

	/**
	* Callback invoked upon an `end` event.
	*
	* @private
	* @returns {void}
	*/
	function onEnd() {
		if (
			time < MIN_TIME &&
			opts.iterations < MAX_ITERATIONS
		) {
			opts.iterations *= 10;
			return next();
		}
		clbk( null, opts.iterations );
	}
}
Determines the number of iterations.

@private
@param {string} name - benchmark name
@param {Options} options - benchmark options
@param {(Function|undefined)} benchmark - function containing benchmark code
@param {Callback} clbk - callback to invoke after determining number of iterations
@returns {void}