Benchmark: just another for loop performance

Script Preparation code:

var array = new Array(100000).fill(Math.random())

Tests:

cached
let tmp = 0; let k = array.length; for (let i = 0; i < k; i++) { tmp++; };
uncached
let tmp = 0; for (let i = 0; i < array.length; i++) { tmp++; };

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
cached
uncached

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:97.0) Gecko/20100101 Firefox/97.0

Browser/OS: Firefox 97 on Mac OS X 10.15

View result in a separate tab

Test name	Executions per second
cached	11051.9 Ops/sec
uncached	15455.4 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated 2 months ago):

LLMs can make mistakes. Check important info.

**What is being tested?**

The provided benchmark tests the performance of two approaches: using `array.length` as a constant value versus caching it within a variable, `k`, in a JavaScript for loop.

In essence, the benchmark compares the execution time of two versions of the same code:

1. **Uncached**: Using `array.length` directly in the for loop.
2. **Cached**: Storing the length of the array in a variable `k` before using it in the loop.

**Options being compared**

The two approaches differ in how they access the length of the array.

* **Uncached**: Directly uses `array.length` as a value to iterate over the array.
* **Cached**: Stores the length of the array in a variable `k`, and then uses `k` to iterate over the array.

**Pros and Cons**

Here's a brief overview of the pros and cons of each approach:

**Uncached**

Pros:

1. Simple and straightforward code.
2. No additional memory allocation is required.

Cons:

1. Potential performance degradation due to repeated calls to `array.length`.
2. May lead to slower execution times, especially for large arrays.

**Cached**

Pros:

1. Improved performance by storing the length of the array once and reusing it.
2. Reduced overhead from repeated calls to `array.length`.

Cons:

1. Additional memory allocation is required for the variable `k`.
2. Code complexity increases slightly due to the additional variable.

**Library usage**

There is no explicit library mentioned in the benchmark definition or test cases. However, some libraries like Lodash or Ramda might be used indirectly by developers writing tests or benchmarking code.

**Special JS feature/syntax**

This benchmark does not rely on any special JavaScript features or syntax. It's a straightforward, vanilla JavaScript benchmark.

**Other alternatives**

To achieve similar performance improvements, developers could consider using:

1. **Array.prototype.length**: Some JavaScript engines (like V8) cache the length of arrays in memory.
2. **Compiler optimizations**: Some compilers, like Webpack or Rollup, can optimize code by storing array lengths and reusing them.

Keep in mind that these alternatives may not be directly applicable to this specific benchmark, as it's meant to demonstrate a simple performance trade-off between two approaches.

In conclusion, the benchmark tests the performance difference between using `array.length` directly versus caching its value in a variable. The cached approach generally yields better performance due to reduced overhead from repeated calls to `array.length`.

Related benchmarks:

just another for loop performance (version: 0)

cached vs uncached

Comparing performance of: cached vs uncached

Created: 2 years ago by: Guest

Jump to the latest result

cached

uncached

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 2 months ago):