Benchmark: test ABS 5 - MeasureThat.net

Script Preparation code:

var abs = Math.abs
var x = -0.00034254146579137945;
var cycle_counter = 1000000;

Tests:

Math.abs
for(i=0; i<cycle_counter; i++){ var result = Math.abs(x); }
abs
for(i=0; i<cycle_counter; i++){ var result = abs(x); }
Custom1
for(i=0; i<cycle_counter; i++){ var negative = x < 0.0 ? 1 : 0; var result = x - x * 2.0 * negative; }
Compare
for(i=0; i<cycle_counter; i++){ var result = x < 0 ? -x : x }
Bitshift
for(i=0; i<cycle_counter; i++){ var result = (x ^ (x >> 31)) - (x >> 31) }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Math.abs
abs
Custom1
Compare
Bitshift

Fastest: N/A

Slowest: N/A

Latest run results:

No previous run results

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

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks on MeasureThat.net.

**Benchmark Definition**

The provided JSON represents a benchmark definition, which defines the test case:

*   **Script Preparation Code**: This code is executed once to set up the environment for the benchmark. In this case, it declares `abs` as an alias for `Math.abs` and initializes a variable `x` with a small negative value. The `cycle_counter` variable is also initialized with 1,000,000.

**Test Cases**

There are four test cases:

*   **Math.abs**: This test case uses the built-in JavaScript function `Math.abs`.
*   **abs**: This test case redefines `abs` as a local alias for `Math.abs`. In this case, it's equivalent to the first test case.
*   **Custom1** (also known as "Compare"): This test case performs an explicit comparison to determine whether `x` is negative or non-negative. It uses the bitwise shift operator (`>>`) to simulate multiplication by 2 and then checks if `x` is less than a small positive value. If so, it negates the result.
*   **Bitshift**: This test case exploits a trick that takes advantage of the behavior of the bitwise XOR operator (`^`) with negative numbers. The idea is that `(x ^ (x >> 31)) - (x >> 31)` equals `x` if and only if `x` is non-negative.

**Options Compared**

These four test cases demonstrate different approaches to calculate the absolute value:

*   **Using built-in functions**: `Math.abs`
*   **Redefining a local alias**: `abs`
*   **Bitwise shift trick**: `Bitshift`
*   **Explicit comparison**: `Custom1`

**Pros and Cons**

Here's a brief summary of each approach:

*   **Built-in function (Math.abs)**:
    *   Pros: Easy to read, widely supported, and well-documented.
    *   Cons: May be slower due to the overhead of the built-in function call.
*   **Local alias**: `abs`
    *   Pros: Similar performance to `Math.abs` and easy to read.
    *   Cons: Requires declaring a new variable, which can be a minor overhead.
*   **Bitwise shift trick (Bitshift)**:
    *   Pros: Can potentially be faster than the built-in function due to the bitwise operations, but its performance may vary depending on the browser and hardware.
    *   Cons: The code is less readable, and it relies on specific JavaScript engine behavior.
*   **Explicit comparison (Custom1)**:
    *   Pros: Easy to understand and might be faster than the built-in function due to fewer function calls, but its performance can be variable depending on the browser's optimization.
    *   Cons: Requires more CPU instructions for the explicit comparison.

**Libraries**

None are explicitly mentioned in the provided benchmark definition.

**Special JS Features or Syntax**

There is no special JavaScript feature or syntax used in this benchmark. The code only uses standard JavaScript features, such as variables, loops, and bitwise operators.

**Alternatives**

To compare the performance of different absolute value implementations:

*   You can use other browsers to run the benchmarks.
*   You can experiment with different input values for `x`.
*   You can try alternative implementations, like using a library or a specialized function for each platform (e.g., `Math.abs` on WebAssembly).

Remember that JavaScript engines and hardware have varying optimization techniques. Always test multiple approaches to ensure you're choosing the best one for your specific use case.

Related benchmarks:

test ABS 5 (version: 0)

Comparing performance of: Math.abs vs abs vs Custom1 vs Compare vs Bitshift

Created: 3 years ago by: Guest

Jump to the latest result

Math.abs

abs

Custom1

Compare

Bitshift

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):