Benchmark: array dynamic vs fixed length

Script Preparation code:

var len = 100000;

Tests:

dynamic
var arr = []; for (var i = 0; i < len; i++) { arr.unshift(i); }
fixed
var arr = new Array(len); for (var i = 0; i < len; i++) { arr.unshift(i); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
dynamic
fixed

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 break down the benchmark definition and test cases to understand what is being tested.

**Benchmark Definition:**
The benchmark definition is comparing two approaches to create an array in JavaScript:

1. **Dynamic length**: Creating an empty array `[]` and then pushing elements onto it using `unshift()` method.
2. **Fixed length**: Creating an array with a fixed length using `new Array(len)` and then pushing elements onto it using `unshift()` method.

**Script Preparation Code:**
The script preparation code is setting the length of the array to be tested, which is set to 100000 in this case.

**Html Preparation Code:**
There is no HTML preparation code provided, suggesting that the benchmark only measures JavaScript performance and does not involve rendering or executing any HTML-related tasks.

**Individual Test Cases:**

1. **Dynamic**: This test creates an empty array `[]` and then pushes elements onto it using `unshift()` method.
```javascript
var arr = [];
for (var i = 0; i < len; i++) {
    arr.unshift(i);
}
```
This approach can be beneficial when the number of elements is not known in advance, as it allows for dynamic array creation.

**Pros:**

* Can handle variable-length arrays
* No need to specify the length upfront

**Cons:**

* Can lead to slower performance due to repeated allocations and memory reallocations
* May result in less cache-friendly data structures

2. **Fixed**: This test creates an array with a fixed length using `new Array(len)` and then pushes elements onto it using `unshift()` method.
```javascript
var arr = new Array(len);
for (var i = 0; i < len; i++) {
    arr.unshift(i);
}
```
This approach can be beneficial when the number of elements is known in advance, as it allows for more efficient memory allocation and caching.

**Pros:**

* Faster performance due to fewer allocations and memory reallocations
* More cache-friendly data structures

**Cons:**

* Requires specifying the length upfront, which may not be ideal if the length is variable

**Library Usage:**
There is no explicit library usage mentioned in this benchmark. However, `unshift()` method is a built-in JavaScript method.

**Special JS Features/Syntax:**
None mentioned.

**Other Alternatives:**

* Other approaches to create arrays include using `Array.prototype.fill()` or `Array.from()`, but these methods are not being tested here.
* Some modern JavaScript engines may also optimize array creation by allocating a contiguous block of memory for the array, but this is not explicitly being compared in this benchmark.

**Benchmark Results:**
The latest benchmark results show that the **Dynamic** approach performs worse than the **Fixed** approach, with an execution rate of 58.87785720825195 executions per second (FPS) compared to 8.834522247314453 FPS for the **Fixed** approach. This suggests that creating an array with a fixed length is generally faster and more efficient in this benchmark.

Related benchmarks:

array dynamic vs fixed length (version: 0)

Comparing performance of: dynamic vs fixed

Created: 9 years ago by: Guest

Jump to the latest result

dynamic

fixed

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):