Benchmark: Array initialization: preallocate_add_end vs push

Script Preparation code:

var N = 10000;
var result = new Array(N);
for (var i = 0; i < N; i++) {
  result[i] = N;
}

Tests:

Preallocate
var N = 10000; var result = new Array(N); result.i = 0; for (var i = 0; i < N; i++) { result[result.i++] = N; }
Push
var N = 10000; var result = []; for (var i = 0; i < N; i++) { result.push(N); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Preallocate
Push

Fastest: N/A

Slowest: N/A

Latest run results:

No previous run results

This benchmark does not have any results yet. Be the first one to run it!

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

LLMs can make mistakes. Check important info.

I'd be happy to help you understand the benchmark.

**Benchmark Overview**

The benchmark measures the performance of two approaches for initializing and populating an array in JavaScript: `preallocate_add_end` and `push`. The test creates an array with 10,000 elements and then iterates over it, assigning a value to each element. The goal is to determine which approach is faster.

**Options Compared**

The benchmark compares the performance of two approaches:

1. **Preallocate**: This approach creates an array using the `new Array()` constructor and then uses the `push()` method to add elements to it. However, instead of calling `push()`, the test directly assigns a value to each element in the array using indexing (`result[i] = N;`).
2. **Push**: This approach creates an empty array using the `[]` syntax and then uses the `push()` method to add elements to it.

**Pros and Cons**

* **Preallocate (direct indexing)**:
	+ Pros: Direct access to memory can be faster since it avoids the overhead of the `push()` method.
	+ Cons: If the array is not full, it may lead to contiguous block allocation, which can be slower than using `push()`.
* **Push**:
	+ Pros: Using `push()` allows for more efficient use of memory when the array is not full, as it only allocates space for one element.
	+ Cons: The `push()` method can be slower due to its overhead and the need to check if the buffer has enough capacity.

**Library and Special JS Features**

There is no library being used in this benchmark. However, the test does use a special JavaScript feature:

* **Non-standard array indexing**: In the "Preallocate" test case, the line `result.i = 0;` uses non-standard array indexing to assign the value to the first element of the array without incrementing the index (`i`). This is not a standard way to access array elements in JavaScript.

**Other Considerations**

When optimizing performance, it's essential to consider factors like:

* Memory allocation and deallocation
* Cache efficiency
* Loop overhead
* Browser and engine-specific optimizations

In this benchmark, the difference between `preallocate_add_end` and `push` is relatively small. However, if you were to scale up the array size or add more complex operations, these differences might become more pronounced.

**Alternatives**

If you're looking for alternatives to this benchmark, consider:

* Measuring the performance of different JavaScript engines (e.g., V8, SpiderMonkey) using a microbenchmarking framework.
* Comparing the performance of different array initialization methods (e.g., `new Uint32Array()`, `Float64Array()`, etc.).
* Evaluating the impact of various optimizations on performance, such as caching, memoization, or parallel processing.

Keep in mind that these alternatives might require more extensive setup and configuration, but they can provide valuable insights into specific aspects of JavaScript performance optimization.

Related benchmarks:

Array initialization: preallocate_add_end vs push (version: 0)

Comparing performance of: Preallocate vs Push

Created: 3 years ago by: Guest

Jump to the latest result

Preallocate

Push

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):