Benchmark: Coordinate test 3

Script Preparation code:

var width = 480;
var halfWidth = width >> 1;

Tests:

Conditional comparison
var xPos = Math.random() * width; var xQuadLeft = xPos < halfWidth ? 0 : 1;
Bitwise comparison
var xPos = Math.random() * width; var diff = xPos ^ halfWidth; diff |= diff >> 1; diff |= diff >> 2; diff |= diff >> 4; diff |= diff >> 8; diff |= diff >> 16; diff &= ~(diff >> 1) | 0x80000000; diff &= (xPos ^ 0x80000000) & (halfWidth ^ 0x7fffffff); var xQuad = !!diff;
Other test
var xPos = Math.random() * width; var xQuad = xPos ^ halfWidth && ( !(halfWidth ^ 0) || ( (xPos / halfWidth) | 0 ) );

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Conditional comparison
Bitwise comparison
Other test

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 5 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/75.0.3770.100 Safari/537.36

Browser/OS: Chrome 75 on Mac OS X 10.14.5

View result in a separate tab

Test name	Executions per second
Conditional comparison	3509927.2 Ops/sec
Bitwise comparison	2843207.5 Ops/sec
Other test	2347072.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and explain what is being tested.

**Benchmark Definition**

The benchmark definition provides a script that prepares the environment for the tests, including variables `width` and `halfWidth`. The `halfWidth` variable is calculated by shifting the `width` value one bit to the right (`>> 1`). This suggests that the benchmark is testing various comparisons involving binary shifts.

**Individual Test Cases**

There are three test cases:

1. **Conditional comparison**: This test case generates a random `xPos` value between 0 and `halfWidth`, then checks if it's less than or equal to `halfWidth`. The comparison uses a simple ternary operator (`?:`) and is likely testing the speed of conditional branching.
2. **Bitwise comparison**: This test case generates a random `xPos` value between 0 and `width`, performs several bitwise operations on it, and then checks if it has any bits set in common with `halfWidth`. The bitwise operations include:
	* `diff ^ halfWidth`: Performs an XOR operation to clear any bits in `diff` that are set in `halfWidth`.
	* `diff |= diff >> 1`, etc.: Shifts the bits of `diff` one position to the right, effectively dividing it by 2, and then performs an OR operation with itself.
	* `xPos ^ 0x80000000`: Performs an XOR operation with a magic number (`0x80000000`) that sets the most significant bit of any integer value passed as the first argument.
3. **Other test**: This test case generates a random `xPos` value between 0 and `width`, performs a bitwise AND operation on it, and then checks if the result is non-zero using the `!!` operator (a trick to check for zero).

**Library/Functions Used**

The benchmark uses two functions:

* `Math.random()`: Generates a random floating-point number.
* `~` and `&` operators: Perform bitwise NOT and AND operations, respectively.

**Special JS Features/Syntax**

None of the test cases use any special JavaScript features or syntax that would require additional explanation. However, it's worth noting that the `!!` operator used in the "Other test" is a common idiom for checking if a value is zero.

**Approaches Compared**

The benchmark compares three different approaches to perform comparisons:

1. **Conditional branching**: The first test case uses a simple ternary operator to check if `xPos` is less than or equal to `halfWidth`.
2. **Bitwise operations**: The second test case uses bitwise operations (XOR, OR, and NOT) to manipulate the bits of `diff` and compare it with `halfWidth`.
3. **Trick to check for zero**: The third test case uses a trick (`!!`) to check if a value is non-zero.

**Pros and Cons**

Each approach has its pros and cons:

1. **Conditional branching**:
	* Pros: Simple, easy to understand.
	* Cons: May incur branch prediction penalties or have slower execution due to the need for conditional logic.
2. **Bitwise operations**:
	* Pros: Can be faster than conditional branching, as it avoids branch prediction and can utilize pipelining.
	* Cons: Requires careful understanding of bitwise operations and their behavior on integer values.
3. **Trick to check for zero**:
	* Pros: Simple and easy to understand, but may not be immediately obvious to readers without context.
	* Cons: May incur a small performance penalty due to the additional logic required.

**Other Alternatives**

If you were to write a similar benchmark, you might consider adding additional test cases that:

1. Test the behavior of bitwise operations on different integer ranges (e.g., negative numbers, zero, or very large values).
2. Compare the performance of these approaches with other methods, such as comparing against an array or a specific value.
3. Include more variations in the input data to better simulate real-world scenarios and stress the systems being tested.

Keep in mind that writing effective benchmarks requires careful consideration of the target audience, the performance characteristics of the systems being measured, and the test case's relevance to real-world use cases.

Related benchmarks:

Coordinate test 3 (version: 0)

Comparing performance of: Conditional comparison vs Bitwise comparison vs Other test

Created: 5 years ago by: Guest

Jump to the latest result

Conditional comparison

Bitwise comparison

Other test

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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