Benchmark: Set Array elements vs create new Array

Script Preparation code:

var p = [ ];
for (var i=0; i<1000; i++) {
  p.push([i,i]);
}

Tests:

set
var p2 = []; for (var i=0, ito=p.length; i<ito; i++) { var px = p[i]; px[0]=i; px[1]=i; p2.push(px); }
recreate
var p2 = []; for (var i=0, ito=p.length; i<ito; i++) { p2.push([i,i]); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
set
recreate

Fastest: N/A

Slowest: N/A

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

LLMs can make mistakes. Check important info.

I'll break down the benchmark definition and explain what's being tested, compared, and their pros and cons.

**Benchmark Definition**

The benchmark is designed to measure the performance difference between two approaches:

1. **"Set Array elements vs create new Array"**: This is a high-level description of the test. In more detail, it involves creating an array `p` with 1000 elements, each containing two values, and then either updating each element in place or recreating a new array (`p2`) with the same number of elements but updated values.

**Script Preparation Code**

The script preparation code for both tests is identical:
```javascript
var p = [];
for (var i=0; i<1000; i++) {
  p.push([i,i]);
}
```
This creates an array `p` with 1000 elements, each containing two values.

**Html Preparation Code**

There is no HTML preparation code provided for this benchmark.

**Individual Test Cases**

The benchmark consists of two test cases:

1. **"set"`**: This test case updates each element in place using the syntax:
```javascript
for (var i=0, ito=p.length; i<ito; i++) {
  var px = p[i];
  px[0]=i;
  px[1]=i;
  p2.push(px);
}
```
This approach modifies the original array `p` directly.

2. **"recreate"`**: This test case recreates a new array (`p2`) with the same number of elements, but updated values using the syntax:
```javascript
var p2 = [];
for (var i=0; i<1000; i++) {
  p2.push([i,i]);
}
```
This approach creates a new array and copies the updated values from `p` to it.

**Library Used**

There is no explicit library mentioned in the benchmark definition. However, since both tests create arrays using the `push()` method, it's likely that the browser's built-in JavaScript engine is being used.

**Special JS Feature or Syntax**

No special JavaScript features or syntax are explicitly used in these test cases. They only utilize standard JavaScript language constructs.

**Pros and Cons of Each Approach**

1. **"set"` (in-place update):
	* Pros:
		+ May be faster since it doesn't involve creating a new array.
		+ Reduces memory allocation overhead.
	* Cons:
		+ Modifies the original array, which might have unintended consequences in certain situations.
		+ Might not preserve the original values of `p` if there are references to them elsewhere.
2. **"recreate"` (new array creation):
	* Pros:
		+ Preserves the original array `p`.
		+ Reduces the risk of modifying the original data accidentally.
	* Cons:
		+ Involves creating a new array, which can be slower than in-place updates.
		+ Increases memory allocation overhead.

**Other Alternatives**

If you want to explore other alternatives or variations on this benchmark, you could consider:

1. Using different data structures, such as objects or linked lists, instead of arrays.
2. Adding additional operations to the tests, such as sorting or filtering the data.
3. Increasing the size of the array or using more complex data types (e.g., objects with nested properties).
4. Comparing performance across multiple browsers or platforms.

Keep in mind that these alternatives might require adjustments to the benchmark definition and test cases to ensure they remain relevant and accurate.

Latest run results:

Run details: (Test run date: 6 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:57.0) Gecko/20100101 Firefox/57.0

Browser/OS: Firefox 57 on Windows

View result in a separate tab

Test name	Executions per second
set	79977.0 Ops/sec
recreate	77625.5 Ops/sec

Related benchmarks:

Set Array elements vs create new Array (version: 0)

Comparing performance of: set vs recreate

Created: 6 years ago by: Guest

Jump to the latest result

set

recreate

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):