Editing Duff's device

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Test case details

Title *

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Preparation code

Preparation code HTML (this will be inserted in the <body> of a valid HTML5 document in standards mode) (useful when testing DOM operations or including libraries)

Include JavaScript libraries as follows: <script src="//cdn.ext/library.js"></script>

Define setup for all tests (variables, functions, arrays or other objects that will be used in the tests) (runs before each clocked test loop, outside of the timed code region) (e.g. define local test variables, reset global variables, clear canvas, etc.) (see FAQ)

Define teardown for all tests (runs after each clocked test loop, outside of the timed code region) (see FAQ)

Code snippets to compare

Test 1

Title

Async (check if this is an asynchronous test)

Code

var testVal = 0;
var n = iterations;
while (n--) {
 testVal++;
}

Test 2

Title

Async (check if this is an asynchronous test)

Code

/**
 * Duff's Device 
 * http://home.earthlink.net/~kendrasg/info/js_opt/jsOptMain.html#duffsdevice
 */
var testVal = 0;
var n = iterations / 8;
var caseTest = iterations % 8;

do {
 switch (caseTest) {
 case 0:
  testVal++;
 case 7:
  testVal++;
 case 6:
  testVal++;
 case 5:
  testVal++;
 case 4:
  testVal++;
 case 3:
  testVal++;
 case 2:
  testVal++;
 case 1:
  testVal++;
 }
 caseTest = 0;
}
while (--n > 0);

Test 3

Title

Async (check if this is an asynchronous test)

Code

/**
 * Fast Duff's Device
 * @author Jeff Greenberg
 * http://home.earthlink.net/~kendrasg/info/js_opt/jsOptMain.html#fastDuffsdevice
 */
var testVal = 0;
var n = iterations % 8;
while (n--) {
 testVal++;
}

n = parseInt(iterations / 8);
while (n--) {
 testVal++;
 testVal++;
 testVal++;
 testVal++;
 testVal++;
 testVal++;
 testVal++;
 testVal++;
}

Test 4

Title

Async (check if this is an asynchronous test)

Code

/*
 * Fast Duff's Device
 * @author Miller Medeiros <http://millermedeiros.com> 
 * @version 0.1 (2010/08/25)
 */
var testVal = 0;
var n = iterations % 8;
while (n--) {
 testVal++;
}

n = Math.floor(iterations / 8);
while (n--) {
 testVal++;
 testVal++;
 testVal++;
 testVal++;
 testVal++;
 testVal++;
 testVal++;
 testVal++;
}

Test 5

Title

Async (check if this is an asynchronous test)

Code

/*
 * Fast Duff's Device
 * @author Miller Medeiros <http://millermedeiros.com> 
 * @version 0.2 (2010/08/25)
 */
var testVal = 0;
var n = iterations % 8;
while (n--) {
 testVal++;
}

n = (iterations / 8) ^ 0; //`value ^ 0` is the same as `Math.floor` for positive numbers and `Math.ceil` for negative numbers
while (n--) {
 testVal++;
 testVal++;
 testVal++;
 testVal++;
 testVal++;
 testVal++;
 testVal++;
 testVal++;
}

Test 6

Title

Async (check if this is an asynchronous test)

Code

/*
 * Fast Duff's Device
 * @author Miller Medeiros <http://millermedeiros.com> 
 * @version 0.3 (2010/08/25)
 */
var testVal = 0;
var n = iterations % 8;
while (n--) {
 testVal++;
}

n = (iterations * 0.125) ^ 0; //multiplication is faster than division in some cases
while (n--) {
 testVal++;
 testVal++;
 testVal++;
 testVal++;
 testVal++;
 testVal++;
 testVal++;
 testVal++;
}