Benchmark: 32bit copyWithin: is it fast?

Script Preparation code:

// starting with a plain array buffer, what is fastest?
var buffer = new ArrayBuffer(1024 * 1024);
var originalIntView = new Uint32Array(buffer);
for (var i = 0; i < originalIntView.length; i++) {
  originalIntView[i] = Math.round(Math.random() * 256);
}

Tests:

Uint32 copyWithin
originalIntView.copyWithin(0, 512*1024, 1024*1024)
Int32 Iteration
for (var i = 0; i < 1024 * 512; i++) { originalIntView[i] = originalIntView[i + 1024 * 512]; }
Uint32 copy within
var int32View = new Uint32Array(originalIntView.buffer, originalIntView.byteOffset, originalIntView.byteLength / 4); for (var i = 0; i < 1024 * 512 / 4; i++) { int32View[i] = int32View[i + 1024 * 512 / 4]; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Uint32 copyWithin
Int32 Iteration
Uint32 copy within

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 the world of JavaScript microbenchmarks on MeasureThat.net.

**Benchmark Definition:**

The benchmark is designed to measure the performance of the `copyWithin` method in JavaScript. The test aims to find out whether using `copyWithin` is faster than other approaches for copying a subset of elements within an array.

**Options Compared:**

There are three options being compared:

1. **Uint32 copyWithin**: This option uses the `copyWithin` method on a Uint32Array, which is a view into the underlying ArrayBuffer.
2. **Int32 Iteration**: This option uses a traditional for loop to iterate over the elements of the array and shift them manually.
3. **Uint32 copy within**: This option is similar to the first one but creates a new Uint32Array with the desired offset.

**Pros and Cons:**

1. **Uint32 copyWithin**:
	* Pros: Fast and efficient, leveraging the optimized `copyWithin` method in V8 (Chrome's JavaScript engine).
	* Cons: May not be compatible with older browsers or engines that don't support `copyWithin`.
2. **Int32 Iteration**:
	* Pros: Portable across all browsers and engines, as it only uses standard JavaScript features.
	* Cons: Can be slower due to the manual shifting of elements.
3. **Uint32 copy within**:
	* Pros: Similar performance to `copyWithin`, but creates a new array for better readability.
	* Cons: Creates an extra object in memory.

**Libraries and Special Features:**

The test doesn't explicitly use any libraries, but it does create a new ArrayBuffer using the `ArrayBuffer` constructor. This is a standard JavaScript feature that's supported by all browsers.

There are no special JavaScript features or syntax used in this benchmark. It only relies on standard JavaScript methods and data structures.

**Other Considerations:**

When writing benchmarks like this one, it's essential to consider factors like:

* **Memory allocation**: Creating new objects can impact performance, especially if the arrays are large.
* **Cache locality**: Accessing elements that are close together in memory can improve cache locality and reduce memory access overhead.
* **Browser-specific optimizations**: Different browsers may optimize certain features or methods differently, affecting benchmark results.

**Alternatives:**

If you're interested in exploring alternative approaches for copying arrays in JavaScript, here are a few options:

1. Use `splice()` to remove elements from the beginning of the array and then use `concat()` to add the desired number of copies.
2. Create a new array using the spread operator (`...`) and then copy the elements from the original array into the new one.
3. Use `slice()` or `subarray()` to create a shallow copy of the array, which can be more efficient than creating a deep copy.

Keep in mind that each approach has its trade-offs, and the best method depends on your specific use case and requirements.

Related benchmarks:

32bit copyWithin: is it fast? (version: 0)

Is copyWithin fast?

Comparing performance of: Uint32 copyWithin vs Int32 Iteration vs Uint32 copy within

Created: 4 years ago by: Guest

Jump to the latest result

Uint32 copyWithin

Int32 Iteration

Uint32 copy within

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):