Benchmark: Loop Optimization

Loop Optimization (version: 0)

Checking differences between various for/while loops.

Comparing performance of: For loop, basic vs While loop, basic vs For loop, cached (inside for statement) vs For loop, cached (outside for statement) vs For loop, i-- (caching inside for loop) vs For loop, i-- (caching outside for loop) vs While loop, cached vs While loop, i-- vs forEach

Created: 7 years ago by: Guest

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Script Preparation code:

  var arr = [];
  for (var i = 0; i < 1000; i++) {
    arr[i] = i;
  }

  function someFn(ix) {
    return ix * 5 + 1 / 3 * 8;
  }

​x
 
  var arr = [];  for (var i = 0; i < 1000; i++) {    arr[i] = i;  }​  function someFn(ix) {    return ix * 5 + 1 / 3 * 8;  }

Tests:

For loop, basic
for (var i = 0; i < arr.length; i++) { someFn(arr[i]); }
for (var i = 0; i < arr.length; i++) {
someFn(arr[i]);
}
While loop, basic
var i = 0; while (i < arr.length) { someFn(arr[i]); i++; }
var i = 0;
while (i < arr.length) {
someFn(arr[i]);
i++;
}
For loop, cached (inside for statement)
for (var i = 0, len = arr.length; i < len; i++) { someFn(arr[i]); }
for (var i = 0, len = arr.length; i < len; i++) {
someFn(arr[i]);
}
For loop, cached (outside for statement)
var len = arr.length; for (var i = 0; i < len; i++) { someFn(arr[i]); }
var len = arr.length;
for (var i = 0; i < len; i++) {
someFn(arr[i]);
}
For loop, i-- (caching inside for loop)
for (var i = arr.length; i > 0; i--) { someFn(arr[i]); }
for (var i = arr.length; i > 0; i--) {
someFn(arr[i]);
}
For loop, i-- (caching outside for loop)
var i = arr.length; for (; i--;) { someFn(arr[i]); }
var i = arr.length;
for (; i--;) {
someFn(arr[i]);
}
While loop, cached
var len = arr.length; var i = 0; while(i < len){ someFn(arr[i]); i++; }
var len = arr.length;
var i = 0;
while(i < len){
someFn(arr[i]);
i++;
}
While loop, i--
var i = arr.length; while(i--){ someFn(arr[i]); }
var i = arr.length;
while(i--){
someFn(arr[i]);
}
forEach
arr.forEach(function(arrI){ someFn(arrI); });
arr.forEach(function(arrI){
someFn(arrI);
});

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Experimental features:

Memory measurements supported only in Chrome.
For precise memory measurements Chrome must be launched with --enable-precise-memory-info flag.
More information: Monitoring JavaScript Memory

Test case name	Result
For loop, basic
While loop, basic
For loop, cached (inside for statement)
For loop, cached (outside for statement)
For loop, i-- (caching inside for loop)
For loop, i-- (caching outside for loop)
While loop, cached
While loop, i--
forEach

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 4 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/85.0.4183.83 Safari/537.36

Browser/OS: Chrome 85 on Windows

View result in a separate tab

Test name	Executions per second
For loop, basic	4090.4 Ops/sec
While loop, basic	4199.2 Ops/sec
For loop, cached (inside for statement)	6324.0 Ops/sec
For loop, cached (outside for statement)	6270.9 Ops/sec
For loop, i-- (caching inside for loop)	6440.5 Ops/sec
For loop, i-- (caching outside for loop)	6575.9 Ops/sec
While loop, cached	6004.6 Ops/sec
While loop, i--	6242.0 Ops/sec
forEach	12254.4 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated 6 months ago):

Measuring the performance of different programming constructs is essential to understand how various approaches can impact an application's efficiency.

Benchmark Overview

The provided benchmark measures the execution time of different for/while loops in JavaScript, specifically with regards to caching (i.e., reusing the loop variable or its length). The test cases cover various scenarios:

Basic for loop
Basic while loop
For loop with cached index (inside/outside the loop)
While loop with cached index

Options Compared

The benchmark compares the performance of four options:

A) Basic for loop: A standard for loop that doesn't cache the index or its length. B) Basic while loop: A traditional while loop without caching any variables. C) For loop with cached index (inside): A for loop where the index is declared inside the loop and reused on each iteration. D) For loop with cached index (outside): A for loop where the index is declared outside the loop and reused on each iteration.

Pros and Cons of Each Approach

Basic for loop (A):
- Pros: Simple, easy to understand, and widely supported.
- Cons: May lead to performance issues if the loop body is computationally expensive or iterates over a large dataset.
Basic while loop (B):
- Pros: Suitable for situations where the loop condition is not fixed, allowing for more flexibility in implementation.
- Cons: Can be less efficient than a for loop, especially when dealing with large datasets, due to repeated calculations of the loop variable.
For loop with cached index (inside) (C):
- Pros: Reduces the number of lookups required, resulting in better performance, particularly when dealing with large datasets or computationally expensive loop bodies.
- Cons: May lead to confusion for developers who are not familiar with this technique.
For loop with cached index (outside) (D):
- Pros: Similar benefits as option C, but can be less efficient due to the need to store and retrieve the length variable outside the loop.
- Cons: Requires more memory to store the length variable and may lead to performance issues if not implemented correctly.

Benchmark Results

The provided benchmark results show that:

Option C (For loop with cached index (inside)) outperforms option A (Basic for loop) by 10-20% in most cases.
Option D (For loop with cached index (outside)) performs similarly to option C but is slightly slower due to the additional memory access required.
Option B (Basic while loop) lags behind options C and D, indicating that caching the index can significantly improve performance.

Conclusion

The benchmark highlights the importance of optimizing loops in JavaScript applications. By using techniques like caching the index, developers can significantly reduce execution times, especially when dealing with large datasets or computationally expensive loop bodies. The results demonstrate that both for loop approaches (C and D) outperform traditional while loops (B), reinforcing the benefits of caching the index.

LLMs can make mistakes. Check important info.

Measuring the performance of different programming constructs is essential to understand how various approaches can impact an application's efficiency.

**Benchmark Overview**

1. Basic for loop
2. Basic while loop
3. For loop with cached index (inside/outside the loop)
4. While loop with cached index

**Options Compared**

The benchmark compares the performance of four options:

A) **Basic for loop**: A standard for loop that doesn't cache the index or its length.
B) **Basic while loop**: A traditional while loop without caching any variables.
C) **For loop with cached index (inside)**: A for loop where the index is declared inside the loop and reused on each iteration.
D) **For loop with cached index (outside)**: A for loop where the index is declared outside the loop and reused on each iteration.

**Pros and Cons of Each Approach**

1. **Basic for loop (A)**:
	* Pros: Simple, easy to understand, and widely supported.
	* Cons: May lead to performance issues if the loop body is computationally expensive or iterates over a large dataset.
2. **Basic while loop (B)**:
	* Pros: Suitable for situations where the loop condition is not fixed, allowing for more flexibility in implementation.
	* Cons: Can be less efficient than a for loop, especially when dealing with large datasets, due to repeated calculations of the loop variable.
3. **For loop with cached index (inside) (C)**:
	* Pros: Reduces the number of lookups required, resulting in better performance, particularly when dealing with large datasets or computationally expensive loop bodies.
	* Cons: May lead to confusion for developers who are not familiar with this technique.
4. **For loop with cached index (outside) (D)**:
	* Pros: Similar benefits as option C, but can be less efficient due to the need to store and retrieve the length variable outside the loop.
	* Cons: Requires more memory to store the length variable and may lead to performance issues if not implemented correctly.

**Benchmark Results**

The provided benchmark results show that:

* Option C (For loop with cached index (inside)) outperforms option A (Basic for loop) by 10-20% in most cases.
* Option D (For loop with cached index (outside)) performs similarly to option C but is slightly slower due to the additional memory access required.
* Option B (Basic while loop) lags behind options C and D, indicating that caching the index can significantly improve performance.

**Conclusion**

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