Benchmark: arguments vs array arg

Script Preparation code:

function test() {
    var v = [];
    for (var _i = 0; _i < arguments.length; _i++) {
        v[_i] = arguments[_i];
    }
  var different = false;
  for (var j = 0; j < v.length; j++) {
    if (j % 2 === 0) different = true;
  }
  return different;
}


function test2(v) {
  var different = false;
  for (var j = 0; j < v.length; j++) {
    if (j % 2 === 0) different = true;
  }
  return different;
}

Tests:

arguments
for(var i = 0; i < 10000; i++) { test(i, i + 1, i + 2, i + 3, i + 4, i + 5); }
array arg
for(var i = 0; i < 10000; i++) { test2(i, i + 1, i + 2, i + 3, i + 4, i + 5); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
arguments
array arg

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 27 days ago):

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and explain what is being tested.

**Benchmark Definition**

The benchmark definition provides two scripts: `test` and `test2`. Both scripts have a similar structure, which is to iterate over an array of values (either from `arguments` or directly passed as an argument) and check if every other value in the array meets a certain condition (`j % 2 === 0`).

**Options Compared**

The benchmark compares two approaches:

1. **Arguments**: The script uses the `arguments` object, which is an array-like object that contains the arguments passed to the function. When called with multiple arguments, it creates an array of those arguments.
2. **Array Argument**: The script directly passes an array as an argument to the function.

**Pros and Cons**

* **Arguments**:
	+ Pros: Easy to use, requires minimal code changes to modify the benchmark.
	+ Cons: Performance might be slower due to the overhead of creating an array-like object from individual arguments.
* **Array Argument**:
	+ Pros: Can be faster, as it avoids the overhead of creating an array-like object and directly passes a pre-constructed array.
	+ Cons: Requires more code changes to modify the benchmark, and might not be suitable for all use cases.

**Library**

None explicitly mentioned in the provided code. However, it's worth noting that `arguments` is a built-in JavaScript object, while `Array` is a built-in JavaScript constructor.

**Special JS Features or Syntax**

The benchmark uses the `for...of` loop (not shown in the provided code) implicitly by using `var _i = 0; _i < arguments.length;`. This is not explicitly mentioned in the explanation, but it's an important detail to note. The `for...of` loop was introduced in ECMAScript 2015.

**Other Considerations**

* **Cache Locality**: In both scripts, the iteration over the array uses a sequential approach, which means that each element is accessed in contiguous memory locations. This can lead to cache locality issues, where the CPU caches elements closer together.
* **Branch Prediction**: The benchmark's condition `j % 2 === 0` creates a branch prediction issue, as it's unclear whether the even index will be true or false on average.

**Alternatives**

If you wanted to write this benchmark, alternative approaches could include:

1. Using a loop that directly iterates over an array of values.
2. Using `for...of` loop with an explicit array of values.
3. Using `Array.prototype.forEach()` method, which is more concise and expressive than the original implementation.

Keep in mind that these alternatives might not be suitable for every use case or performance-critical benchmarking scenario.

Latest run results:

Run details: (Test run date: 2025 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.132 Safari/537.36

Browser/OS: Chrome 63 on Mac OS X 10.12.6

View result in a separate tab

Test name	Executions per second
arguments	759.7 Ops/sec
array arg	1324.9 Ops/sec

Related benchmarks:

arguments vs array arg (version: 0)

Comparing performance of: arguments vs array arg

Created: 6 years ago by: Guest

Jump to the latest result

arguments

array arg

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 27 days ago):