Benchmark: Test array concat

HTML Preparation code:

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Script Preparation code:

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async function globalMeasureThatScriptPrepareFunction() {
    // This function is optional, feel free to remove it.
    // await someThing();
}

Tests:

copy
var getConcatenation = function(nums) { let ans = []; for (i = 0; i < nums.length; i++) { ans[i] = nums[i]; ans[i + nums.length] = nums[i]; } return ans; }; for (let i = 0; i < 100000; i++) { getConcatenation([1,2,3,4,5]); }
concat
var getConcatenation = function (nums) { return nums.concat(nums); }; for (let i = 0; i < 100000; i++) { getConcatenation([1,2,3,4,5]); }
in place
var getConcatenation = function(nums) { const len = nums.length; for (i = 0; i < len; i++) { nums[i + len] = nums[i]; } return nums; }; for (let i = 0; i < 100000; i++) { getConcatenation([1,2,3,4,5]); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
copy
concat
in place

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 3 days ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/129.0.0.0 Safari/537.36

Browser/OS: Chrome 129 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
copy	63.2 Ops/sec
concat	168.9 Ops/sec
in place	68.1 Ops/sec

Autogenerated LLM Summary (model gpt-4o-mini, generated 3 days ago):

LLMs can make mistakes. Check important info.

The benchmark is designed to compare three different methods for concatenating an array with itself in JavaScript. Here’s a breakdown of the methods evaluated, their pros and cons, and relevant considerations.

### Test Cases and Approaches

1. **Copy Method (Test Name: "copy")**
   ```javascript
   var getConcatenation = function(nums) {
       let ans = [];
       for (i = 0; i < nums.length; i++) {
           ans[i] = nums[i];
           ans[i + nums.length] = nums[i];
       }
       return ans;
   };
   ```
   - **Description**: This method creates a new array `ans` to hold the results. It loops through the original array `nums`, copying each element to the new array twice—once for the first half and once for the second half.
   - **Pros**:
     - Clear and straightforward implementation.
   - **Cons**:
     - Requires additional memory allocation for the new array `ans`, which can be less efficient regarding memory usage and performance due to the overhead of creating a new array.

2. **Concat Method (Test Name: "concat")**
   ```javascript
   var getConcatenation = function (nums) {
       return nums.concat(nums);
   };
   ```
   - **Description**: This approach uses the built-in `concat` method in JavaScript to combine the `nums` array with itself.
   - **Pros**:
     - Utilizes JavaScript's native method, which is typically optimized for performance.
     - Provides cleaner and more readable code.
   - **Cons**:
     - Depending on the implementation of the JavaScript engine, this may not be as memory-efficient due to the potential overhead of generating a new array.
  
3. **In-Place Method (Test Name: "in place")**
   ```javascript
   var getConcatenation = function(nums) {
       const len = nums.length;
       for (i = 0; i < len; i++) {
           nums[i + len] = nums[i];
       }
       return nums;
   };
   ```
   - **Description**: This method modifies the original array by expanding it in place, storing the values directly at the computed index.
   - **Pros**:
     - More efficient in terms of memory usage, as it alters the original array and doesn't create a new one.
   - **Cons**:
     - Modifies the original array, which may not be desired in scenarios where immutability is preferred.
     - The final size of the array becomes double its original length which can lead to inconsistencies if the original array is expected to remain unchanged.

### Benchmark Results

The benchmark results show the following executions per second for each approach on a specific setup (Chrome 129 on macOS):

- **concat**: 168.93 executions/second
- **in place**: 68.11 executions/second
- **copy**: 63.22 executions/second

From the results, it's evident that using the built-in `concat()` method outperformed both the copy and in-place methods, suggesting that optimizations in the JavaScript engine make this approach the fastest.

### Other Considerations

- **Performance Variation**: The performance characteristics may vary significantly based on the JavaScript engine and the context (e.g., browser, device). Different scenarios might show different results due to optimizations.
- **Function Complexity**: All three approaches exhibit linear time complexity O(n), but their space complexity differs, influencing their practical application based on memory constraints.
- **Use Cases**: Depending on whether immutability of the original array is a requirement, one method may be preferred over another. For example, in functional programming paradigms, the `concat` method would be favored due to its non-mutating behavior.

### Alternatives

1. **Spread Operator**: An alternative approach using the spread operator could look like this:
   ```javascript
   var getConcatenation = function(nums) {
       return [...nums, ...nums];
   };
   ```
   - This provides both immutability and a clean syntax but might have similar performance characteristics to existing methods.

2. **Array.from()**: Utilizing `Array.from()` paired with `Array.prototype.concat()` could provide a different method but often with comparable performance to the original `concat()` method.

In conclusion, the choice of method will largely depend on the specific requirements of the application, efficiency considerations, and the desired JavaScript behaviors regarding array immutability.

Related benchmarks:

Test array concat (version: 1)

Comparing performance of: copy vs concat vs in place

Created: 3 days ago by: Guest

Jump to the latest result

copy

concat

in place

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gpt-4o-mini, generated 3 days ago):