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Math.round vs 0.5 << 0
(version: 0)
Comparing performance of:
round vs bitRound
Created:
2 years ago
by:
Registered User
Jump to the latest result
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>
Run tests (2)
Previous results
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Test case name
Result
round
bitRound
Fastest:
N/A
Slowest:
N/A
Latest run results:
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Autogenerated LLM Summary
(model
llama3.2:3b
, generated one year ago):
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.
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