Benchmark: Set Array elements vs create new Array

Script Preparation code:

var p = [ ];
for (var i=0; i<5000; i++) {
  p.push([i,i, 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++) { var px = p[i]; p2.push([i,i, px[i], px[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

Latest run results:

No previous run results

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Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):

LLMs can make mistakes. Check important info.

Let's dive into explaining the JavaScript microbenchmark provided by MeasureThat.net.

**Benchmark Description**

The benchmark compares two approaches to set elements in an array:

1. **Set Array Elements**: This approach uses the original array `p` and iterates over its length to access each element, modifying it directly.
2. **Recreate Array**: This approach creates a new array `p2` and iterates over the original array's length, pushing new elements into the new array.

**Options Compared**

The benchmark is comparing two options:

1. **Set Array Elements** (Test Name: "set")
2. **Recreate Array** (Test Name: "recreate")

These approaches have different performance implications due to the following factors:

* **Memory Allocation**: Creating a new array (`p2`) requires more memory allocation compared to modifying an existing array (`p`).
* **Iteration Over Array Length vs Iteration Over Indexes**: The `set` approach uses iteration over the array length, while the `recreate` approach uses iteration over indexes. This can lead to differences in performance due to the way JavaScript handles array indexing and bounds checking.

**Pros and Cons**

* **Set Array Elements (Test Name: "set")**
	+ Pros:
		- Modifies existing array elements directly, potentially reducing memory allocation.
		- May be more cache-friendly due to iterating over indexes.
	+ Cons:
		- Can lead to slower performance due to bounds checking and iteration over the array length.
* **Recreate Array (Test Name: "recreate")**
	+ Pros:
		- Creates a new array, potentially reducing memory allocation overhead.
		- May be more efficient for large datasets due to reduced bounds checking.
	+ Cons:
		- Requires more memory allocation and potentially slower performance due to creating a new array.

**Library Usage**

The benchmark does not explicitly mention any libraries, but it is using the `for` loop with `var` declarations, which are intrinsic JavaScript features. However, modern JavaScript code often uses modernized versions of these loops or polyfills for older browsers.

**Special JS Features/ Syntax**

There are no special JS features or syntax mentioned in this benchmark that would affect its understanding.

**Alternatives**

Other alternatives to measure the performance of array operations could include:

* **Array.prototype.fill()**: Using `Array.prototype.fill()` to set all elements of an array to a specific value.
* **Array.prototype.forEach()**: Using `Array.prototype.forEach()` with an arrow function to iterate over the array and modify its elements.
* **Native WebAssembly (WASM)**: Using WASM, which provides a low-level, compiled language for performance-critical code.

Keep in mind that the choice of alternative benchmarking methods depends on the specific use case and requirements.

Related benchmarks:

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

Comparing performance of: set vs recreate

Created: 8 years ago by: Guest

Jump to the latest result

set

recreate

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):