Benchmark: Multiplying lists of vectors - with or without declaration

Script Preparation code:

var N = 1000000;

var vectors = [];
var vector;
for (var i = 0, li=N; i < li; ++i) {
	vectors.push( {x:Math.random(), y:Math.random(), z:Math.random()} );
}
abc=123
var abc=456

Tests:

with duplicate declaration
var vector; for (var i = 0, li=vectors.length; i < li; ++i) { vector = vectors[i]; vector.x = 2 * vector.x; vector.y = 2 * vector.y; vector.z = 2 * vector.z; } abc=123 def=456 var abc
without duplicate declaration
for (var i = 0, li=vectors.length; i < li; ++i) { vector = vectors[i]; vector.x = 2 * vector.x; vector.y = 2 * vector.y; vector.z = 2 * vector.z; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
with duplicate declaration
without duplicate declaration

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 26 days ago):

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks on MeasureThat.net.

**Benchmark Definition JSON**

The provided benchmark definition represents a simple JavaScript script that generates an array of 1 million vectors, then multiplies each vector by 2 in three dimensions (x, y, z). The script also includes some unnecessary declarations and assignments (`abc=123` and `var abc`).

In essence, the benchmark is testing the performance of different approaches to accessing and modifying elements in an array.

**Options Compared**

The two options compared are:

1. **With duplicate declaration**: This option uses a traditional JavaScript `for` loop with a declared variable `vector` inside the loop.
```javascript
var vector;
for (var i = 0, li=vectors.length; i < li; ++i) {
    vector = vectors[i];
    vector.x = 2 * vector.x;
    vector.y = 2 * vector.y;
    vector.z = 2 * vector.z;
}
```
2. **Without duplicate declaration**: This option uses a simple `for` loop without declaring the variable inside.
```javascript
for (var i = 0, li=vectors.length; i < li; ++i) {
    vector = vectors[i];
    vector.x = 2 * vector.x;
    vector.y = 2 * vector.y;
    vector.z = 2 * vector.z;
}
```
**Pros and Cons**

**With duplicate declaration:**

Pros:

* This approach is more explicit and easier to read, as the variable `vector` is declared before use.
* It may be considered more "JavaScript-like" due to its traditional syntax.

Cons:

* The loop variable `i` is not used effectively, making the code slightly less efficient.
* The repeated declaration of `abc` can lead to performance issues in some browsers.

**Without duplicate declaration:**

Pros:

* This approach uses the loop variable `i` more efficiently, as it doesn't need to be declared separately.
* It avoids the unnecessary repetition of `abc` declarations.

Cons:

* The code may appear less explicit or "JavaScript-like" due to its concise syntax.
* Some developers might find this style harder to understand at first glance.

**Library Considerations**

In this benchmark, there are no libraries explicitly used. However, some modern JavaScript engines and browsers use various internal optimizations and mechanisms that can affect performance. For example:

* Chrome's `let` and `const` declarations have a different behavior compared to traditional `var`.
* Opera's execution environment might use its own internal optimizations or caching mechanisms.

**Special JS Feature**

This benchmark does not explicitly use any special JavaScript features, such as:

* ES6 classes
* Async/await
* Promises
* Generators
* Symbols

However, it is worth noting that modern JavaScript engines and browsers often have their own internal performance optimizations and caching mechanisms that can affect the results of microbenchmarks like this one.

**Alternatives**

If you're interested in exploring alternative approaches to benchmarking JavaScript performance, here are a few options:

1. **Benchmark.js**: A popular benchmarking library for JavaScript that provides a more comprehensive set of tools and features.
2. **Testify.js**: Another well-known benchmarking library that offers a wide range of features and customization options.
3. **JavaScript Performance Test (JST)**: An open-source benchmarking framework specifically designed for JavaScript performance testing.

These alternatives can provide more advanced features, customization options, and flexibility for creating custom benchmarks like the one on MeasureThat.net.

Latest run results:

Run details: (Test run date: 7 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2906.0 Safari/537.36 OPR/43.0.2420.0 (Edition developer)

Browser/OS: Opera 43 on Windows

View result in a separate tab

Test name	Executions per second
with duplicate declaration	11.9 Ops/sec
without duplicate declaration	1.5 Ops/sec

Related benchmarks:

Multiplying lists of vectors - with or without declaration (version: 0)

Comparing performance of: with duplicate declaration vs without duplicate declaration

Created: 7 years ago by: Guest

Jump to the latest result

with duplicate declaration

without duplicate declaration

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 26 days ago):