Benchmark: Substring vs Bitmask FIXED

Tests:

Substring
let num = 255; let nums = []; for(let i = 0; i < 100; ++i) { nums.push(parseInt(num.toString(2).padStart(8, '0').substring(0, 4), 2)); }
Bitmask
let num = 255; let nums = []; for(let i = 0; i < 100; ++i) { nums.push((num >> 4) & 0xF); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Substring
Bitmask

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.

**Understanding the Benchmark**

The provided benchmark, hosted on MeasureThat.net, compares two approaches to extract 4-bit values from a binary number: using substring (or indexing) and using bitwise operations with bitmasks.

**Approach 1: Substring**

In this approach, the binary representation of the input number `num` (255 in decimal) is converted to a string using `toString(2)`. The resulting string is then padded with zeros to ensure it has at least 8 characters. Finally, the first 4 characters are extracted using `substring(0, 4)`.

**Approach 2: Bitmask**

In this approach, the bitwise right shift operator (`>>`) is used to extract the upper 4 bits of the input number `num`. The result is then ANDed with a bitmask (0xF) to ensure only the least significant 4 bits are extracted.

**Comparison and Pros/Cons**

The two approaches have different performance characteristics:

*   **Substring approach:**
    *   Advantages:
        *   Simpler code, easier to understand.
        *   Works well for smaller inputs or when the number of bits is not a concern.
    *   Disadvantages:
        *   Slower due to string manipulation and indexing operations.
        *   May be less efficient for large inputs or when the number of bits is significant.
*   **Bitmask approach:**
    *   Advantages:
        *   Faster, as it directly manipulates binary values without creating strings or using indexing.
        *   More efficient for large inputs or when working with a fixed number of bits.
    *   Disadvantages:
        *   Requires knowledge of bitwise operations and bitmasks.
        *   Code can be more complex to understand.

**Library and Special JS Feature**

There are no libraries mentioned in the benchmark, but we might assume some basic JavaScript functionality is available. No special JavaScript features or syntax are explicitly used in these approaches.

**Alternative Approaches**

Other alternatives could include:

*   Using assembly code or native code (not applicable on MeasureThat.net).
*   Employing more advanced bitwise operations, like using masks with specific bit patterns.
*   Utilizing libraries or frameworks that specialize in performance-critical computations.

Related benchmarks:

Substring vs Bitmask FIXED (version: 0)

Comparing performance of: Substring vs Bitmask

Created: 4 years ago by: Guest

Jump to the latest result

Substring

Bitmask

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):