Benchmark: Test for - MeasureThat.net

Script Preparation code:

var arr = [];
  for (var i = 0; i < 1000; i++) {
    arr[i] = i;
  }

  function someFn(ix) {
    return ix * 5;
  }

Tests:

while
var l = arr.length; while(l--) { someFn(arr[l]); }
for
for (var i = 0; i < arr.length; i++) { someFn(arr[i]); }
for 2
var l = arr.length; for (var i = 0; i < l; i++) { someFn(arr[i]); }
for 3
var l = arr.length; var result=0; for (var i = 0; i < l; i++) { result += arr[i] * 5; }
for 4
var result=0; for (var i = 0; i < arr.length; i++) { result += arr[i] * 5; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
while
for
for 2
for 3
for 4

Fastest: N/A

Slowest: N/A

Latest 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!

**Benchmark Definition**

The provided JSON represents a benchmark definition for testing the performance of different loops in JavaScript. The script preparation code defines an array `arr` with 1000 elements, and a function `someFn` that takes an index `ix` as input and returns the result of multiplying `ix` by 5.

**Loop Options Compared**

The benchmark compares four different loop structures:

1. **While Loop**: `while (l--) { someFn(arr[l]); }`
2. **For Loop with Index Variable**: `for (var i = 0; i < arr.length; i++) { someFn(arr[i]); }`
3. **For Loop with Loop Control Variable**: `for (var i = 0; i < l; i++) { someFn(arr[i]); }` (note: here, `l` is a loop control variable, not the length of the array)
4. **For Loop without Index Variable**: `for (var i = 0; i < arr.length; i++) { result += arr[i] * 5; }`

**Pros and Cons of Each Approach**

1. **While Loop**: This approach can be faster for small arrays because it uses a shorter loop overhead. However, it may lead to slower performance for larger arrays due to the need to decrement `l` on each iteration.
2. **For Loop with Index Variable**: This is a common and efficient way to iterate over an array in JavaScript. It avoids the overhead of incrementing/decrementing a loop control variable.
3. **For Loop with Loop Control Variable**: Using a loop control variable like `i` can lead to slower performance compared to using an index variable, as it requires more arithmetic operations.
4. **For Loop without Index Variable**: This approach is less common in JavaScript and may be slower due to the need to access the array elements through an index variable (`i`) even though it's not explicitly used.

**Library Usage**

None of the benchmark definitions use any external libraries, which is a good thing since we're only testing the performance of the loops themselves.

**Special JS Features**

There are no special JavaScript features (e.g., `let`/`const`, async/await) being used in this benchmark. However, it's worth noting that the use of `var` for declaring variables can lead to issues with scope and hoisting in some cases.

**Alternative Approaches**

Other loop structures that could be tested in a similar benchmark include:

* Using `Array.prototype.forEach()` or `Array.prototype.map()`
* Using `for...of` loops
* Using `while` loops with more complex logic (e.g., looping over an array of arrays)

Keep in mind that the performance differences between these approaches may vary depending on the specific use case and implementation details.

Related benchmarks:

Test for (version: 0)

Comparing performance of: while vs for vs for 2 vs for 3 vs for 4

Created: 9 years ago by: Guest

Jump to the latest result

while

for

for 2

for 3

for 4

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):