Benchmark: Direct Array Access vs. New Local Constant Variable in A Loop v.2

Script Preparation code:

var arr = [
    { "key": "value" }, { "key": "value" }, { "key": "value" }, { "key": "value" }, { "key": "value" },
    { "key": "value" }, { "key": "value" }, { "key": "value" }, { "key": "value" }, { "key": "value" },
    { "key": "value" }, { "key": "value" }, { "key": "value" }, { "key": "value" }, { "key": "value" },
    { "key": "value" }, { "key": "value" }, { "key": "value" }, { "key": "value" }, { "key": "value" },
    { "key": "value" }, { "key": "value" }, { "key": "value" }, { "key": "value" }, { "key": "value" },
    { "key": "value" }, { "key": "value" }, { "key": "value" }, { "key": "value" }, { "key": "value" },
    { "key": "value" }, { "key": "value" }, { "key": "value" }, { "key": "value" }, { "key": "value" },
    { "key": "value" }, { "key": "value" }, { "key": "value" }, { "key": "value" }, { "key": "value" },
    { "key": "value" }, { "key": "value" }, { "key": "value" }, { "key": "value" }, { "key": "value" },
    { "key": "value" }, { "key": "value" }, { "key": "value" }, { "key": "value" }, { "key": "value" },
    { "key": "value" }, { "key": "value" }, { "key": "value" }, { "key": "value" }, { "key": "value" },
    { "key": "value" }, { "key": "value" }, { "key": "value" }, { "key": "value" }, { "key": "value" },
    { "key": "value" }, { "key": "value" }, { "key": "value" }, { "key": "value" }, { "key": "value" },
    { "key": "value" }, { "key": "value" }, { "key": "value" }, { "key": "value" }, { "key": "value" },
    { "key": "value" }, { "key": "value" }, { "key": "value" }, { "key": "value" }, { "key": "value" },
    { "key": "value" }, { "key": "value" }, { "key": "value" }, { "key": "value" }, { "key": "value" },
    { "key": "value" }, { "key": "value" }, { "key": "value" }, { "key": "value" }, { "key": "value" },
    { "key": "value" }, { "key": "value" }, { "key": "value" }, { "key": "value" }, { "key": "value" },
    { "key": "value" }, { "key": "value" }, { "key": "value" }, { "key": "value" }, { "key": "value" },
    { "key": "value" }, { "key": "value" }, { "key": "value" }, { "key": "value" }, { "key": "value" },
]

var newarr1 = []
var newarr2 = []

Tests:

Local Variable Access
for (var i = 0; i < arr.length; i++) { const el = arr[i] for (var j = 0; j < 100; j++) newarr2.push(el) }
Direct Array Access
for (var i = 0; i < arr.length; i++) { for (var j = 0; j < 100; j++) newarr2.push(arr[i]) }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Local Variable Access
Direct Array Access

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:95.0) Gecko/20100101 Firefox/95.0

Browser/OS: Firefox 95 on Windows

View result in a separate tab

Test name	Executions per second
Local Variable Access	3907.7 Ops/sec
Direct Array Access	348.0 Ops/sec

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 and test cases, explaining what's being tested, compared, and their pros and cons.

**Benchmark Definition:**

The provided JSON represents a JavaScript microbenchmark named "Direct Array Access vs. New Local Constant Variable in A Loop v.2". This benchmark measures the performance difference between two approaches:

1. **Direct Array Access**: Accessing elements of an array using its index (`arr[i]`) directly.
2. **New Local Constant Variable**: Creating a new local variable `el` and assigning it the value of `arr[i]`, then using this variable in a loop.

**Individual Test Cases:**

There are two individual test cases:

1. **Local Variable Access**
	* Benchmark Definition:
```javascript
for (var i = 0; i < arr.length; i++) {
  const el = arr[i];
  for (var j = 0; j < 100; j++) newarr2.push(el);
}
```
This test case measures the performance of accessing elements of an array using a local variable `el` and then pushing its value to a new array `newarr2`.
2. **Direct Array Access**
	* Benchmark Definition:
```javascript
for (var i = 0; i < arr.length; i++) {
  for (var j = 0; j < 100; j++) newarr2.push(arr[i]);
}
```
This test case measures the performance of accessing elements of an array using its index (`arr[i]`) directly and then pushing its value to a new array `newarr2`.

**Comparison:**

The two test cases compare the performance of these two approaches in different scenarios. The main difference between them is how they handle variable scoping.

In the **Local Variable Access** case, a local variable `el` is created and assigned the value of `arr[i]`. This creates a new scope for the variable, which can lead to better performance due to reduced overhead from garbage collection and fewer opportunities for accidental reassignments of the variable. However, this approach may also lead to increased memory allocation and deallocation.

In contrast, the **Direct Array Access** case accesses elements of the array directly without creating a local variable. This approach may be faster in terms of direct access but can lead to issues with variable scoping, such as accidental reassignments or unexpected behavior due to shared variable names.

**Pros and Cons:**

Pros:

* **Local Variable Access**:
	+ Reduced overhead from garbage collection
	+ Fewer opportunities for accidental reassignments
	+ May be faster in terms of performance
* **Direct Array Access**:
	+ Faster direct access
	+ Simplified code

Cons:

* **Local Variable Access**:
	+ Increased memory allocation and deallocation
	+ May lead to increased function call overhead due to variable creation and destruction
* **Direct Array Access**:
	+ Risk of accidental reassignments or unexpected behavior due to shared variable names
	+ Reduced performance due to garbage collection overhead

**Latest Benchmark Result:**

The latest benchmark result shows the execution times for both test cases on a specific device:

| Test Case | Execution Time |
| --- | --- |
| Local Variable Access | 3907.68212890625 executions/second |
| Direct Array Access | 347.97491455078125 executions/second |

These results suggest that the **Local Variable Access** case performs better than the **Direct Array Access** case, which is consistent with our analysis.

Keep in mind that this benchmark result may vary depending on the specific hardware and software configuration used to run the tests.

Related benchmarks:

Direct Array Access vs. New Local Constant Variable in A Loop v.2 (version: 0)

Comparing performance of: Local Variable Access vs Direct Array Access

Created: 5 years ago by: Guest

Jump to the latest result

Local Variable Access

Direct Array Access

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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