Benchmark: ArrayBuffer - MeasureThat.net

Script Preparation code:

var str = "aa34a5b6c5acb67acb5acb678acb6ac4b5a6c7b5a4c3b45a67c8b76a54cb34a5c6b7aa34a5b6c5acb67acb5acb678acb6ac4b5a6c7b5a4c3b45a67c8b76a54cb34a5c6b7aa34a5b6c5acb67acb5acb678acb6ac4b5a6c7b5a4c3b45a67c8b76a54cb34a5c6b7aa34a5b6c5acb67acb5acb678acb6ac4b5a6c7b5a4c3b45a67c8b76a54cb34a5c6b7aa34a5b6c5acb67acb5acb678acb6ac4b5a6c7b5a4c3b45a67c8b76a54cb34a5c6b7aa34a5b6c5acb67acb5acb678acb6ac4b5a6c7b5a4c3b45a67c8b76a54cb34a5c6b7aa34a5b6c5acb67acb5acb678acb6ac4b5a6c7b5a4c3b45a67c8b76a54cb34a5c6b7aa34a5b6c5acb67acb5acb678acb6ac4b5a6c7b5a4c3b45a67c8b76a54cb34a5c6b7aa34a5b6c5acb67acb5acb678acb6ac4b5a6c7b5a4c3b45a67c8b76a54cb34a5c6b7aa34a5b6c5acb67acb5acb678acb6ac4b5a6c7b5a4c3b45a67c8b76a54cb34a5c6b7aa34a5b6c5acb67acb5acb678acb6ac4b5a6c7b5a4c3b45a67c8b76a54cb34a5c6b7aa34a5b6c5acb67acb5acb678acb6ac4b5a6c7b5a4c3b45a67c8b76a54cb34a5c6b7";

var chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

// Use a lookup table to find the index.
var lookup = new Uint8Array(256);
for (var i = 0; i < chars.length; i++) {
  lookup[chars.charCodeAt(i)] = i;
}

function decode(base64) {
    var bufferLength = base64.length * 0.75,
    len = base64.length, i, p = 0,
    encoded1, encoded2, encoded3, encoded4;

    if (base64[base64.length - 1] === "=") {
      bufferLength--;
      if (base64[base64.length - 2] === "=") {
        bufferLength--;
      }
    }

    var arraybuffer = new ArrayBuffer(bufferLength),
    bytes = new Uint8Array(arraybuffer);

    for (i = 0; i < len; i+=4) {
      encoded1 = lookup[base64.charCodeAt(i)];
      encoded2 = lookup[base64.charCodeAt(i+1)];
      encoded3 = lookup[base64.charCodeAt(i+2)];
      encoded4 = lookup[base64.charCodeAt(i+3)];

      bytes[p++] = (encoded1 << 2) | (encoded2 >> 4);
      bytes[p++] = ((encoded2 & 15) << 4) | (encoded3 >> 2);
      bytes[p++] = ((encoded3 & 3) << 6) | (encoded4 & 63);
    }

    return arraybuffer;
  };

function _base64ToArrayBuffer(base64) {
    var binary_string =  window.atob(base64);
    var len = binary_string.length;
    var bytes = new Uint8Array( len );
    for (var i = 0; i < len; i++)        {
        bytes[i] = binary_string.charCodeAt(i);
    }
    return bytes.buffer;
}

Tests:

Cached decode
decode(str);
Simple decode
_base64ToArrayBuffer(str);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Cached decode
Simple decode

Fastest: N/A

Slowest: N/A

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

LLMs can make mistakes. Check important info.

I'll break down the provided benchmark definition, options being compared, and considerations for each test case.

**Benchmark Definition and Test Cases**

The benchmark measures the performance of two functions: `decode` (with caching) and `_base64ToArrayBuffer` (without caching). The `decode` function takes a base64-encoded string as input and returns an ArrayBuffer. The `_base64ToArrayBuffer` function also takes a base64-encoded string as input and returns an ArrayBuffer.

**Options Being Compared**

The options being compared are:

1. **Caching**: In the `decode` function, we have two approaches:
	* **Lookup table**: Using a lookup table to find the index of each character in the base64-encoded string.
	* **atob**: Using the `atob` method (a built-in JavaScript function) to decode the base64-encoded string directly into an ArrayBuffer.
2. **Function call frequency**: In both functions, we have two options:
	* **Direct encoding** (e.g., `lookup[base64.charCodeAt(i)]`): Encodes each character in the input string individually using a lookup table or by iterating over the characters.
	* **Batch encoding** (e.g., `_base64ToArrayBuffer(str)`): Passes the entire base64-encoded string to the decoding function at once, without iterating over individual characters.

**Pros and Cons of Each Approach**

**Lookup Table (decode)**

Pros:

* Can be optimized for performance by precomputing and caching the lookup table.
* May lead to more cache-friendly access patterns.

Cons:

* Requires additional memory allocation for the lookup table.
* May require more complex data structures or optimizations to handle edge cases.

**atob (decode)**

Pros:

* Eliminates the need for a lookup table or explicit encoding.
* Simplifies code and reduces the likelihood of errors.

Cons:

* May be slower due to the overhead of calling an external function (`atob` is implemented in native code).
* May lead to less cache-friendly access patterns, depending on the implementation.

**Direct Encoding vs. Batch Encoding**

For both functions, **direct encoding** can lead to slower performance due to the overhead of iterating over individual characters or accessing a lookup table for each character.

**Batch Encoding** can be more efficient by allowing the decoding function to process large chunks of data at once. However, this approach may require additional memory allocation and management to handle large inputs efficiently.

**Considerations**

When designing optimizations for these functions, consider the following factors:

* **Cache locality**: Minimize cache misses by optimizing access patterns to reduce memory accesses.
* **Function call frequency**: Balance between direct encoding (more predictable but slower) and batch encoding (less predictable but faster).
* **Memory allocation and management**: Optimize memory usage to avoid performance bottlenecks.
* **Edge cases**: Handle special cases, such as invalid input or very large inputs, efficiently.

By understanding these trade-offs and optimizations, developers can create more efficient and scalable implementations for the `decode` and `_base64ToArrayBuffer` functions.

Related benchmarks:

ArrayBuffer (version: 0)

Comparing performance of: Cached decode vs Simple decode

Created: 9 years ago by: Guest

Jump to the latest result

Cached decode

Simple decode

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):