Benchmark: Math.round vs 0.5 << 0

Script Preparation code:

window.round = (val, decimalScale = 1) => Math.round(val * decimalScale) / decimalScale;
window.bitRound = (val, base = 1) => (val * base + 0.5 << 0) / base;

Tests:

round
round(Math.random(), 100);
bitRound
bitRound(Math.random(), 100);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
round
bitRound

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 25 days ago):

LLMs can make mistakes. Check important info.

I'd be happy to help explain the benchmark and its results.

**Benchmark Overview**

The provided benchmark measures the performance of two rounding methods: `Math.round` and `0.5 << 0`. The test case consists of two parts:

1. **Script Preparation Code**: This section defines two new functions, `window.round` and `window.bitRound`, which are used to simulate the behavior of `Math.round`. `window.round` uses the traditional rounding method, while `window.bitRound` uses a bit-shifting trick (more on this later).
2. **Test Case**: The test case consists of two separate tests: one for each of the two rounding functions.

**0.5 << 0: A Bit-Shifting Trick**

The `0.5 << 0` syntax is an interesting one. In JavaScript, the left shift operator (`<<`) shifts the bits of a number to the left by a specified amount. When you use `0.5 << 0`, it's equivalent to multiplying `0.5` by 2^0 (which is just 1). This effectively rounds up the result of dividing two numbers with the same scale factor.

In this case, the bit-shifting trick works because it effectively adds a tiny bias to the division result, causing the rounding to always round up. The trick relies on the fact that `0.5` can be represented as a binary fraction (0.1 in decimal). When you shift this value by 0, you're essentially losing the least significant bit, which means you're no longer dealing with fractions.

**Pros and Cons of Bit-Shifting Trick**

Pros:

* Faster execution: The bit-shifting trick can potentially outperform traditional rounding methods for certain use cases.
* Scalable: This method scales better than traditional rounding methods as numbers increase in magnitude.

Cons:

* Less readable: Using a bit-shifting trick can make the code harder to understand and debug, especially for developers without a strong background in binary arithmetic.
* Not standard-compliant: While this trick works in most browsers, it's not explicitly defined in the JavaScript standard.

**Other Alternatives**

If you're interested in exploring alternative rounding methods, some other options include:

* `Number.EPSILON`: This property represents the smallest difference between two distinct values. You can use it to create a more precise rounding method.
* `BigInt` and arithmetic operations: For larger integers or numbers with specific scale factors, using `BigInt` arithmetic can provide better performance.

However, keep in mind that these alternatives might not be as optimized for general-purpose rounding tasks.

**Library and Framework Considerations**

There are no libraries specifically used in this benchmark. The only external function is `Math.round`, which is part of the JavaScript standard library.

**Special JS Features or Syntax (None)**

There are no special features or syntax used in this benchmark, aside from the bit-shifting trick mentioned earlier.

In summary, the 0.5 << 0 trick relies on a binary arithmetic optimization to achieve faster rounding times. While it has its advantages, it can make the code harder to understand and is not standard-compliant.

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/16.5 Safari/605.1.15

Browser/OS: Safari 16 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
round	2896543.2 Ops/sec
bitRound	4171890.8 Ops/sec

Related benchmarks:

Math.round vs 0.5 << 0 (version: 0)

Comparing performance of: round vs bitRound

Created: one year ago by: Registered User

Jump to the latest result

round

bitRound

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 25 days ago):