Benchmark: div by 2 vs shift 1 vs mul 0.5

Tests:

Division (/ 2)
function testDivision(iterations) { let x = 123456; console.time('Division (/ 2)'); for (let i = 0; i < iterations; i++) { x = x / 2; } console.timeEnd('Division (/ 2)'); } testDivision(100000000);
Bitwise Shift (>> 1)
function testBitwiseShift(iterations) { let x = 123456; console.time('Bitwise Shift (>> 1)'); for (let i = 0; i < iterations; i++) { x = x >> 1; } console.timeEnd('Bitwise Shift (>> 1)'); } testBitwiseShift(100000000);
Multiplication (* 0.5)
function testMultiplication(iterations) { let x = 123456; console.time('Multiplication (* 0.5)'); for (let i = 0; i < iterations; i++) { x = x * 0.5; } console.timeEnd('Multiplication (* 0.5)'); } testMultiplication(100000000);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Division (/ 2)
Bitwise Shift (>> 1)
Multiplication (* 0.5)

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:136.0) Gecko/20100101 Firefox/136.0

Browser/OS: Firefox 136 on Windows

View result in a separate tab

Test name	Executions per second
Division (/ 2)	11.9 Ops/sec
Bitwise Shift (>> 1)	23.7 Ops/sec
Multiplication (* 0.5)	11.9 Ops/sec

Autogenerated LLM Summary (model gpt-4o-mini, generated one month ago):

LLMs can make mistakes. Check important info.

### Benchmark Overview

The provided benchmark tests three different approaches for halving a number: division by 2, a bitwise right shift by 1, and multiplication by 0.5. The benchmark is designed to compare the performance of these methods in JavaScript, specifically focusing on their execution speed.

### Test Cases

1. **Division by 2 (`x / 2`)** 
   - **Purpose**: This method uses the arithmetic division operator to halve the value of `x`.
   - **Performance Metrics**: The benchmark reports the number of executions per second for this operation.
   - **Pros**:
     - Easier to read and understand, especially for those familiar with arithmetic operations.
     - Standard and universally applicable in various contexts (e.g., can handle floating-point numbers accurately).
   - **Cons**:
     - Divisions can be less efficient than other arithmetic operations due to the way CPUs optimize processing.

2. **Bitwise Shift (`x >> 1`)**
   - **Purpose**: This approach uses the bitwise right shift operator, which shifts the bits of the number to the right by one position, effectively performing an integer division by 2.
   - **Performance Metrics**: It also records executions per second.
   - **Pros**:
     - Typically faster than direct division because it operates at the bit level, which is closer to the way processors handle data.
     - Can be beneficial for integer arithmetic, yielding more predictable performance metrics.
   - **Cons**:
     - This method only works correctly with non-negative integers, as it may yield different results for negative numbers (in terms of sign bits).
     - Less readable for those unfamiliar with bitwise operations.

3. **Multiplication by 0.5 (`x * 0.5`)**
   - **Purpose**: This operation multiplies the number by 0.5 to achieve the same effect as halving.
   - **Performance Metrics**: The number of executions per second is also measured for this operation.
   - **Pros**:
     - Readability is similar to division, making it intuitive for most programmers.
     - Works seamlessly with floating-point numbers, yielding precise results.
   - **Cons**:
     - Can be slower than bitwise operations due to potential optimizations in integer arithmetic.

### Benchmark Results

The benchmarking results show the following:

- **Bitwise Shift (>> 1)**: 23.70 executions per second (fastest)
- **Multiplication (* 0.5)**: 11.87 executions per second 
- **Division (/ 2)**: 11.87 executions per second (slowest)

From the results, it's clear that the bitwise shift operation is the fastest among the three methods, demonstrating the performance advantage of bitwise manipulations in JavaScript. Division and multiplication, while more readable, can be less efficient in terms of raw execution speed.

### Other Considerations and Alternatives

- **Precision**: When working with very large or very small numbers, the precision of floating-point arithmetic can lead to different outcomes between division and multiplication. This could be a significant factor depending on the application's context.
  
- **Alternative Approaches**: Besides these three methods, software engineers could consider other mathematical tricks or libraries, such as using specialized numerical libraries when dealing with performance-sensitive code or complex mathematical operations. However, the basic operations tested here are foundational and widely applicable.
  
- **Modern JavaScript Optimizations**: Engine-specific optimizations can change performance characteristics based on the JavaScript engine (like V8 in Chrome or SpiderMonkey in Firefox). Testing on various environments may yield different results.

In summary, when performance is crucial and working specifically with integers, the bitwise shift is preferred. For clarity and compatibility with floating-point arithmetic, division and multiplication remain valid choices, albeit potentially slower for large-scale operations.

Related benchmarks:

div by 2 vs shift 1 vs mul 0.5 (version: 1)

Comparing performance of: Division (/ 2) vs Bitwise Shift (>> 1) vs Multiplication (* 0.5)

Created: one month ago by: Registered User

Jump to the latest result

Division (/ 2)

Bitwise Shift (>> 1)

Multiplication (* 0.5)

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gpt-4o-mini, generated one month ago):