Let's break down the provided benchmark and explain what's being tested, compared, and their pros and cons.

Benchmark Overview

MeasureThat.net is a platform that allows users to create and run JavaScript microbenchmarks. The provided benchmark definition and test cases demonstrate two approaches: native and fast inverse (which uses a custom implementation).

The benchmark measures the execution time of mathematical operations, specifically:

• Native: Measures the execution time of the built-in Math.sqrt function.
• Fast inverse: Measures the execution time of a custom implementation for calculating square roots.

Native Benchmark

In the native benchmark, only one test case is provided:

1/Math.sqrt(958573654687437984)

This test case measures the execution time of the built-in Math.sqrt function. The JavaScript engine will automatically optimize and execute this expression.

Fast Inverse Benchmark

The fast inverse benchmark provides two test cases:

• Test 1: Measures the execution time of a custom implementation for calculating square roots.

var buf = new ArrayBuffer(4),
    f32=new Float32Array(buf),
    u32=new Uint32Array(buf);

function squareRoot(x) {
    var x2 = 0.5 * (f32[0] = x);
    u32[0] = (0x5f3759df - (u32[0] >> 1));
    var y = f32[0];
    y  = y * ( 1.5 - ( x2 * y * y ) ); //newton's method
    return ~~(0.5 + y * x) << 0 ; //bitwise rounding method
}

squareRoot(958573654687437984);

This custom implementation uses a combination of bitwise operations and Newton's method to estimate the square root.

Comparison

The two test cases are compared in terms of execution time, with the fast inverse benchmark providing a separate result for each test case. The latest benchmark results show:

• Chrome 87: Native (7501597.5 executions per second) vs Fast inverse (1229363.25 executions per second)

Pros and Cons

Native Benchmark:

Pros:

• Uses built-in functions, which are typically optimized by the JavaScript engine.
• No additional memory allocation or data structure creation required.

Cons:

• Execution time may be affected by the JavaScript engine's optimization strategies.
• No control over the implementation details.

Fast Inverse Benchmark:

Pros:

• Provides a custom implementation that can be optimized for specific use cases.
• Allows for fine-grained control over the calculation method and data structures used.

Cons:

• Requires additional memory allocation and data structure creation, which may impact performance.
• The custom implementation may not be as efficient as the built-in Math.sqrt function.

Other Considerations

In addition to the execution time, other factors that may affect the benchmark results include:

• Memory usage: The fast inverse benchmark creates an array buffer, which can consume memory resources.
• Cache locality: The custom implementation may exhibit poor cache locality due to its use of bitwise operations and data structure allocation.

Alternatives

If you're interested in exploring alternative approaches for calculating square roots or other mathematical operations, some options include:

• Using specialized libraries like NumJS or Mathjs
• Implementing custom algorithms using languages like C++ or Rust
• Leveraging hardware acceleration (e.g., SIMD instructions) to speed up calculations

Keep in mind that the best approach will depend on your specific use case and performance requirements.