Benchmark: What's faster unshifting left by 1 or multiplying by 2

Tests:

left unshift
console.log(34 << 1)
times two
console.log(34 * 2)

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
left unshift
times two

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:125.0) Gecko/20100101 Firefox/125.0

Browser/OS: Firefox 125 on Windows

View result in a separate tab

Test name	Executions per second
left unshift	248697.6 Ops/sec
times two	251958.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Measuring JavaScript performance is an essential task, and MeasureThat.net provides a great platform for it.

**What's being tested?**

The provided benchmark tests the performance of two different operations:

1. **Left unshift**: This operation shifts the elements in an array to the left by one position, effectively moving the last element to the end of the array.
2. **Multiplying by 2**: This operation multiplies a number by 2.

**Options compared**

Two approaches are being tested:

1. **Left shift operator (`<<`)**: This operator shifts the bits in an integer to the left by a specified number of positions, effectively multiplying the value by 2.
2. **Multiplication by 2**: This is a simple arithmetic operation that multiplies a number by 2.

**Pros and cons of each approach**

1. **Left shift operator (`<<`)**:
	* Pros: Efficient use of CPU resources, as it operates on the integer representation of the value, rather than creating an intermediate result.
	* Cons: May not be suitable for large integers or values with a lot of decimal places, as it can lead to rounding errors and overflow issues.
2. **Multiplication by 2**:
	* Pros: Easy to understand and implement, especially for small numbers. It's also more intuitive than the left shift operator for some developers.
	* Cons: May result in slower performance due to intermediate calculations and memory allocation.

**Other considerations**

When dealing with arrays or large numbers, other factors come into play, such as:

* **Array indexing**: In JavaScript, when using `<<` on an array, it's essential to consider how the index calculation works. This can impact performance.
* **Integer overflow**: When performing left shifts or multiplications, it's crucial to handle potential integer overflows correctly.

**Library and purpose**

In this benchmark, no libraries are explicitly mentioned. However, JavaScript engines, such as V8 (used by Chrome), SpiderMonkey (used by Firefox), or others, might employ various optimizations and internal representations for integers and arrays.

If you were to write a test script, it would likely involve:

* Creating an array or number
* Applying the left shift operator or multiplication by 2
* Verifying the result

Here's a sample implementation in JavaScript:
```javascript
const arr = [1, 2, 3];

// Left shift operator example
console.log(arr.slice(0, -1).concat([arr[arr.length - 1]])); // Slice and concatenate

// Multiplication by 2 example
console.log(arr.map(x => x * 2));
```
**Special JavaScript features or syntax**

This benchmark does not use any special JavaScript features or syntax. It's focused on demonstrating the performance comparison between two simple operations.

If you have any further questions about this explanation, feel free to ask!

Related benchmarks:

What's faster unshifting left by 1 or multiplying by 2 (version: 0)

Benchmark description

Comparing performance of: left unshift vs times two

Created: 2 years ago by: Registered User

Jump to the latest result

left unshift

times two

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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