Benchmark: legacy vs ir - MeasureThat.net

Script Preparation code:

function isJsArray(obj_0) {
    var tmp0_unsafeCast_0 = Array.isArray(obj_0);
    return tmp0_unsafeCast_0;
  }

function isArray(obj_0) {
    var tmp;
    if (isJsArray(obj_0)) {
      tmp = !obj_0.$type$;
    } else {
      tmp = false;
    }
    return tmp;
  }

function arrayConcat(args) {
    var len = args.length;
    var tmp0_unsafeCast_0 = Array(len);
    var typed = tmp0_unsafeCast_0;
    var inductionVariable = 0;
    var last = len - 1 | 0;
    if (inductionVariable <= last)
      do {
        var i = inductionVariable;
        inductionVariable = inductionVariable + 1 | 0;
        var arr = args[i];
        if (!(!(arr == null) ? isArray(arr) : false)) {
          typed[i] = [].slice.call(arr);
        } else {
          {
            typed[i] = arr;
          }
        }
      }
       while (!(i === last));
    return [].concat.apply([], typed);
  }

var args = (new Int32Array(10000)).map(_ => Math.random(1000000));

Tests:

legacy
arrayConcat([0, 1], args)
ir
[0, 1].concat([].slice.call(args))

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
legacy
ir

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.

I'll explain the provided benchmark definition, options compared, pros and cons of each approach, and other considerations.

**Benchmark Definition**

The provided JSON represents a JavaScript microbenchmark that compares two approaches to concatenate arrays: the legacy approach and the "IR" (Intermediate Representation) approach. The test cases are:

1. `arrayConcat([0, 1], args)` - This is the legacy approach.
2. `[0, 1].concat([].slice.call(args))` - This is the IR approach.

**Options Compared**

The two approaches compared in this benchmark are:

### Legacy Approach

* Uses the `Array.isArray()` method to check if an object is an array.
* Uses the `arrayConcat()` function, which concatenates arrays using a loop that copies elements from each input array into a new array.
* Uses `Array.prototype.slice.call()` to convert the input arguments to arrays.

### IR Approach

* Does not use `Array.isArray()`.
* Directly calls the `concat()` method on an empty array created with `[]`.

**Pros and Cons of Each Approach**

### Legacy Approach

Pros:

* More explicit and readable code.
* Avoids potential issues with `Array.isArray()` returning `NaN` for certain types.

Cons:

* Has a higher constant factor due to the loop in `arrayConcat()`.
* May be slower due to the overhead of converting input arguments to arrays using `Array.prototype.slice.call()`.

### IR Approach

Pros:

* Generally faster than the legacy approach due to the optimized implementation of `concat()`.
* Avoids unnecessary overhead of explicit array creation and conversion.

Cons:

* Less readable code due to its concise syntax.
* May be less familiar to developers without experience with JavaScript's intermediate representation (IR).

**Library Used**

The `Array.isArray()` method is a built-in JavaScript function that checks if an object is an array. Its purpose is to provide a convenient way to check for array-like objects, which can be useful in various scenarios.

**Special JS Feature/Syntax**

None of the provided code uses special JavaScript features or syntax beyond what's considered standard (ECMAScript 2020).

**Other Considerations**

* The benchmark measures the execution speed of each approach using Firefox 86 on a Mac OS X 10.16 desktop.
* The benchmark results show that the legacy approach is slower than the IR approach, but both approaches should be optimized for performance in real-world scenarios.

As an alternative to these two approaches, other ways to concatenate arrays in JavaScript include:

1. Using the `concat()` method directly on arrays: `[0, 1].concat([]).concat(args)`.
2. Using the spread operator (`...`): `[0, 1, ...args]`.
3. Using `Array.prototype.concat()` with an empty array created using `[]`: `[0, 1].concat(new Array(0).concat(args))`.

Each of these alternatives has its own trade-offs in terms of performance, readability, and maintainability.

Related benchmarks:

legacy vs ir (version: 0)

Comparing performance of: legacy vs ir

Created: 5 years ago by: Guest

Jump to the latest result

legacy

ir

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):