Benchmark: Fast Sqrt - MeasureThat.net

Script Preparation code:

var i;
var r;
var v = 2**16;

function test1() {
  for(i=0; i < 1000; ++i) {
    r = Math.sqrt(v);
  }
}

function test2() {
  for(i=0; i < 1000; ++i) {
    r = Q_rsqrt(v) * v;
  }
}

//Based on the fast inverse square root function
// https://en.wikipedia.org/wiki/Fast_inverse_square_root
// Some original comments preserved for humor value
// Designed to try to mimic the original as closely as possible
function Q_rsqrt(number)
{ 
    var i;
    var x2, y;
    const threehalfs = 1.5;
  
    x2 = number * 0.5;
    y = number;
    //evil floating bit level hacking
    var buf = new ArrayBuffer(4);
    (new Float32Array(buf))[0] = number;
    i =  (new Uint32Array(buf))[0];
    i = (0x5f3759df - (i >> 1)); //What the fuck?
    (new Uint32Array(buf))[0] = i;
    y = (new Float32Array(buf))[0];
    y  = y * ( threehalfs - ( x2 * y * y ) );   // 1st iteration
//  y  = y * ( threehalfs - ( x2 * y * y ) );   // 2nd iteration, this can be removed

    return y;
}

Tests:

Math.sqrt
test1();
Quakes fast inverse sqrt.
test2();

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Math.sqrt
Quakes fast inverse sqrt.

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 6 months ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:145.0) Gecko/20100101 Firefox/145.0

Browser/OS: Firefox 145 on Windows

View result in a separate tab

Test name	Executions per second
Math.sqrt	45726.2 Ops/sec
Quakes fast inverse sqrt.	494.8 Ops/sec

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

LLMs can make mistakes. Check important info.

I'll break down the provided benchmark definition and test cases to explain what's being tested, compared, and their pros and cons.

**Benchmark Definition**

The benchmark is testing two JavaScript functions: `test1()` and `test2()`. The latter uses the Quakes fast inverse square root function, which is a custom implementation of the fast inverse square root algorithm. This algorithm is an optimization for calculating the square root in floating-point arithmetic, particularly useful for high-performance applications.

**Functionality of test1()**

`test1()` calculates the square root of a large number (`v`) using the built-in `Math.sqrt()` function 1000 times. The purpose of this test is to evaluate how fast the `Math.sqrt()` function executes.

**Functionality of test2()**

`test2()` also calculates the square root of `v`, but it uses the Quakes fast inverse square root function, which is a custom implementation that attempts to mimic the original fast inverse square root algorithm. This test aims to compare the performance of this custom implementation with the built-in `Math.sqrt()` function.

**Comparison**

The benchmark compares the execution time of two approaches:

1. **Built-in Math.sqrt()**: The first test case (`test1()`) measures the execution time of using the built-in `Math.sqrt()` function.
2. **Quakes fast inverse sqrt.**: The second test case (`test2()`) measures the execution time of using the custom Quakes fast inverse square root function.

**Pros and Cons**

Pros:

* The use of a benchmarking framework allows for a fair comparison between different implementations.
* The tests cover two common scenarios: using built-in functions versus custom optimizations.

Cons:

* Using a custom implementation (Quakes fast inverse sqrt.) may introduce additional complexity and potential errors, which could affect the results.
* The Quakes fast inverse square root function is not part of the standard JavaScript library, so it might not be supported by all browsers or environments.

**Library: FastInverseSqrt**

The `FastInverseSqrt` library is a custom implementation of the fast inverse square root algorithm. It's likely that this library is designed for high-performance applications and provides an optimized solution for calculating square roots in floating-point arithmetic.

**Other alternatives**

In general, when it comes to calculating square roots in JavaScript:

1. **Built-in Math.sqrt()**: This is a reliable and widely supported function that works well for most use cases.
2. **Custom implementations**: Optimized custom implementations like Quakes fast inverse sqrt. might be useful in specific high-performance applications where the built-in function is not sufficient.

However, it's essential to note that using custom implementations can add complexity and potential errors, so they should be used judiciously.

**Special JS feature or syntax**

This benchmark does not use any special JavaScript features or syntax beyond what's required for the implementation of the Quakes fast inverse square root function.

Related benchmarks:

Fast Sqrt (version: 0)

Compare Quakes fast inverse squareroot

Comparing performance of: Math.sqrt vs Quakes fast inverse sqrt.

Created: 7 years ago by: Guest

Jump to the latest result

Math.sqrt

Quakes fast inverse sqrt.

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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