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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
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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>
Run tests (3)
Previous results
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Test case name
Result
Uint32 copyWithin
Int32 Iteration
Uint32 copy within
Fastest:
N/A
Slowest:
N/A
Latest run results:
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Autogenerated LLM Summary
(model
llama3.2:3b
, generated one year ago):
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.
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