Benchmark: anti-gc in for loops

Script Preparation code:

var ARRAY = [undefined, null, 0, 0, 1, 0.1, NaN, "ez", "dsadsadsa", new Map(), {}, Math, Object, class k {}, () => {}, , , , undefined];
delete ARRAY[0];
var resetPoint = ARRAY;

Tests:

no reuse
ARRAY = resetPoint; for (let i = ARRAY.length; i--;) { ARRAY[i] = ARRAY[i] + "" + i; }; for (let i = ARRAY.length; i--;) { ARRAY[i] = ARRAY[i] + "" + i; }; for (let i = ARRAY.length; i--;) { ARRAY[i] = ARRAY[i] + "" + i; }; for (let i = ARRAY.length; i--;) { ARRAY[i] = ARRAY[i] + "" + i; }; for (let i = ARRAY.length; i--;) { ARRAY[i] = ARRAY[i] + "" + i; };
reuse
ARRAY = resetPoint; let i = ARRAY.length; for (; i--;) { ARRAY[i] = ARRAY[i] + "" + i; }; for (i = ARRAY.length; i--;) { ARRAY[i] = ARRAY[i] + "" + i; }; for (i = ARRAY.length; i--;) { ARRAY[i] = ARRAY[i] + "" + i; }; for (i = ARRAY.length; i--;) { ARRAY[i] = ARRAY[i] + "" + i; }; for (i = ARRAY.length; i--;) { ARRAY[i] = ARRAY[i] + "" + i; };

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
no reuse
reuse

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!

**What is being tested?**

The provided JSON represents two benchmark test cases: "anti-gc in for loops" and its variants, "no reuse" and "reuse". The goal is to measure how different approaches to iterating over an array with "for" loops affect performance.

**Options compared:**

There are two main options being compared:

1. **Using the length property of the array**: In both test cases, the `ARRAY` variable is created and then the `length` property is used to iterate over the array.
2. **Reusing the iteration variable**: In the "reuse" variant, a separate variable `i` is declared and reused for each iteration.

**Pros and Cons:**

1. **Using the length property of the array**:
	* Pros:
		+ Simple and straightforward approach.
	* Cons:
		+ May lead to more garbage collection (GC) overhead due to frequent changes in the loop variable.
2. **Reusing the iteration variable**:
	* Pros:
		+ Reduces GC overhead by reusing a single variable for each iteration.
	* Cons:
		+ May require additional memory allocation and deallocation, leading to slower performance.

**Library usage:**

There is no explicit library mentioned in the benchmark definition or test cases. However, it's worth noting that some modern JavaScript engines use specialized libraries like V8 (used by Chrome) or SpiderMonkey (used by Firefox) to optimize JavaScript execution.

**Special JS features/syntax:**

There are a few subtle aspects of JavaScript syntax and engine behavior being tested here:

* **Array indexing**: The benchmark uses the array index `i` to access elements, which is a fundamental aspect of array manipulation in JavaScript.
* **Variable scoping**: The reuse variant declares a new variable `i` outside the loop, which can affect its visibility and behavior within the loop.

**Other alternatives:**

If you wanted to write your own benchmarking code for this scenario, you could consider using a framework like BenchmarkJS or Microbenchmark (which is used by MeasureThat.net). These libraries provide a simple way to define and run microbenchmarks, allowing you to compare different approaches and measure their performance.

In terms of alternative iteration methods, you could explore using other techniques like:

* **ForEach**: This method applies a provided callback function to each element in the array without creating an explicit loop.
* **Array.prototype.forEach.call()**: This method is similar to forEach but allows for additional functionality (like handling asynchronous callbacks).

However, for this specific benchmark, using a simple "for" loop with array indexing is likely the most straightforward and efficient approach.

Related benchmarks:

anti-gc in for loops (version: 0)

Comparing performance of: no reuse vs reuse

Created: 4 years ago by: Guest

Jump to the latest result

no reuse

reuse

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):