Benchmark: I vs J - MeasureThat.net

Script Preparation code:

var arr = [];
for (var x = 0; x < 10000; x++)
{
 arr[x]=[]; 
}

Tests:

IJ
for (var i=0; i < 10000; i++) { for (var j=0; j < 10000; j++) { arr[i][j]=i*j; } }
JI
for (var i=0; i < 10000; i++) { for (var j=0; j < 10000; j++) { arr[j][i]=i*j; } }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
IJ
JI

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 8 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/52.0.2743.116 Safari/537.36

Browser/OS: Chrome 52 on Windows

View result in a separate tab

Test name	Executions per second
IJ	0.1 Ops/sec
JI	0.1 Ops/sec

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

LLMs can make mistakes. Check important info.

I'd be happy to explain what's being tested in this benchmark.

**Benchmark Overview**

The benchmark compares the performance of two approaches: nested loops with `i` as the outer loop and `j` as the inner loop, versus nested loops with `j` as the outer loop and `i` as the inner loop. The loop iterates 10,000 times in each direction.

**Script Preparation Code**

The script preparation code initializes an empty array `arr` and populates it with another empty array for each iteration of the outer loop (`x`). This is done to ensure that the inner loops have access to the correct index values.

**Options Compared**

There are two main options being compared:

1. **Nested Loops with `i` as Outer Loop and `j` as Inner Loop**
	* Code: `for (var i=0; i < 10000; i++) { for (var j=0; j < 10000; j++) { arr[i][j]=i*j; } }`
	* This approach is generally considered more efficient because it allows the compiler to optimize the loop bounds and avoid redundant calculations.
2. **Nested Loops with `j` as Outer Loop and `i` as Inner Loop**
	* Code: `for (var i=0; i < 10000; i++) { for (var j=0; j < 10000; j++) { arr[j][i]=i*j; } }`
	* This approach can be slower because it requires accessing the outer array `arr` with each inner loop iteration, which can lead to additional memory access and calculations.

**Pros and Cons**

* **Nested Loops with `i` as Outer Loop:**
	+ Pros:
		- Often optimized by compilers
		- Can avoid redundant calculations
	+ Cons:
		- May not be as intuitive for developers who are not familiar with this structure
* **Nested Loops with `j` as Outer Loop:**
	+ Pros:
		- Can be more intuitive for developers who are used to this structure
	+ Cons:
		- May not be optimized by compilers
		- Can lead to slower performance due to additional memory access and calculations

**Other Considerations**

* **Array Indexing**: In both approaches, the inner loops need to calculate the correct index values `i*j` or `j*i`. This can add unnecessary complexity and overhead.
* **Cache Efficiency**: The choice of loop structure can impact cache efficiency. For example, accessing an outer array with each inner loop iteration may lead to more cache misses.

**Library Usage**

There is no explicit library usage in the benchmark definition. However, the use of JavaScript's built-in `for` loops and array indexing suggests that the browser's V8 engine (used by Chrome 52) provides the necessary functionality for array manipulation and iteration.

**Special JS Features/Syntax**

There are no special JavaScript features or syntax used in this benchmark beyond standard loop constructs and array indexing.

Related benchmarks:

I vs J (version: 0)

Comparing performance of: IJ vs JI

Created: 8 years ago by: Guest

Jump to the latest result

IJ

JI

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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