Benchmark: Bitwise shift vs and

Script Preparation code:

var hash = 0x1B873593;
var k = hash;
var n = hash;

Tests:

shift
k = k ^ (k >>> 16);
and
n = n ^ (n & 0xFFFF);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
shift
and

Fastest: N/A

Slowest: N/A

Latest run results:

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

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Let's break down the provided benchmark and its options.

**Benchmark Overview**

The test is designed to compare the performance of two bitwise operations: shifting (>>> 16) vs. ANDing with a mask (& 0xFFFF). The goal is to measure which operation is faster for performing a specific hash calculation.

**Script Preparation Code**

The script preparation code initializes three variables:

* `hash`: a constant value set to `0x1B873593`
* `k`: initialized to the value of `hash`
* `n`: also initialized to the value of `hash`

These variables will be used in the test cases.

**Benchmark Definition and Test Cases**

There are two test cases:

1. **Shift**: The benchmark definition is `k = k ^ (k >>> 16)`. This operation performs a bitwise XOR between `k` and the result of shifting `k` right by 16 bits.
2. **AND**: The benchmark definition is `n = n ^ (n & 0xFFFF)`. This operation performs a bitwise XOR between `n` and the result of ANDing `n` with the mask `0xFFFF`.

**Options Compared**

The two options are:

1. **Shift**: uses bitwise shifting (`>>> 16`)
2. **AND**: uses bitwise AND (`& 0xFFFF`)

**Pros and Cons**

* **Shift**:
	+ Pros: Can be more efficient for large values, as it only requires a single shift operation.
	+ Cons: May not be suitable for small values or when the shift amount is close to the word size.
* **AND**:
	+ Pros: Suitable for small values or when the mask is close to the word size.
	+ Cons: Requires two separate operations (masking and shifting) which may be slower than a single shift operation.

**Library and Special JS Features**

There are no libraries mentioned in the benchmark definition. However, JavaScript has some special features that might affect the performance of these operations:

* **Bitwise operators**: The `>>>` operator is used for unsigned right shift, while `>>` is used for signed right shift.
* **Integer arithmetic**: The bitwise operations are performed on integers, which may have different behavior than floating-point numbers.

**Alternatives**

Other alternatives to compare the performance of these two options might include:

1. Bitwise OR (`|`) vs. AND (`&`)
2. Bitwise XOR (`^`) vs. Shift
3. Simple arithmetic (`k * 65536 + k` vs `n * 65536 + n`)

However, it's essential to note that the specific choice of operation depends on the problem being solved and the characteristics of the input data.

**Device-Specific Considerations**

The benchmark results are reported for a mobile device (Android 13) running Firefox Mobile 116. The performance results may vary depending on other factors such as CPU architecture, memory constraints, and JavaScript engine optimizations.

In conclusion, the test compares the performance of two bitwise operations: shifting vs. ANDing with a mask. While both options have their pros and cons, the shift operation might be more efficient for large values, while the AND operation is suitable for small values or when the mask is close to the word size.

Related benchmarks:

Bitwise shift vs and (version: 0)

Comparing performance of: shift vs and

Created: 2 years ago by: Guest

Jump to the latest result

shift

and

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

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