Windows 7 [C#] - stack vs. heap allocation

[AceInfinity]

Here's a demonstration and benchmark test I did on allocating to the stack vs. allocating on the heap. I combined both allocation and retrieval into each method for each allocation destination, and the results are below.

Note: There are benefits of each, although for speed, allocation on the stack is much faster if you need that for performance. The downside is that the heap is a much larger block of space than the stack, which is usually limited. Therefore, you can get a stack overflow exception if you try to push too much to the stack before it's pop'd off.

Upon declaration to the stack, for instance, this line:

int* i = stackalloc int[100000];

Will actually measure how much space we need to allocate 100000 signed 32 bit integer values on the stack, which is 4 bytes * 100000 = 400000bytes.

private unsafe void Method1()
{
    int tmp;
    int* i = stackalloc int[100000];
    for (int n = 0; n < 100000; n++)
        i[n] = 0;
    for (int x = 0; x < 100000; x++) tmp = i[x];
}

private unsafe void Method2()
{
    int tmp;
    int[] i = new int[100000];
    for (int n = 0; n < 100000; n++)
        i[n] = 0;
    for (int x = 0; x < 100000; x++) tmp = i[x];
}

(Benchmark Starting... 10 averages of 100 runs)

# Method1
> [Average 1/10] Complete - 2720.28 ticks
> [Average 2/10] Complete - 2471.68 ticks
> [Average 3/10] Complete - 2502.54 ticks
> [Average 4/10] Complete - 2510.59 ticks
> [Average 5/10] Complete - 2508.63 ticks
> [Average 6/10] Complete - 2501.61 ticks
> [Average 7/10] Complete - 2776.15 ticks
> [Average 8/10] Complete - 2450.17 ticks
> [Average 9/10] Complete - 2451.4 ticks
> [Average 10/10] Complete - 2645.82 ticks
# Result: 2553.887 ticks

# Method2
> [Average 1/10] Complete - 5423.1 ticks
> [Average 2/10] Complete - 5580.77 ticks
> [Average 3/10] Complete - 5003.69 ticks
> [Average 4/10] Complete - 5214.7 ticks
> [Average 5/10] Complete - 4891.69 ticks
> [Average 6/10] Complete - 5313.5 ticks
> [Average 7/10] Complete - 5554.04 ticks
> [Average 8/10] Complete - 5269.06 ticks
> [Average 9/10] Complete - 5384.69 ticks
> [Average 10/10] Complete - 5209.16 ticks
# Result: 5284.44 ticks

 

[ChatGPT]

The benchmark test you conducted provides a clear comparison between allocating on the stack and allocating on the heap. Here's a breakdown of the results you shared:

### Method1 - Stack Allocation
- Average time: 2553.887 ticks

### Method2 - Heap Allocation
- Average time: 5284.44 ticks

From these results, it's evident that stack allocation (Method1) is significantly faster than heap allocation (Method2). This speed advantage is crucial for performance-sensitive applications.

However, as you mentioned, there are trade-offs to consider:

• Stack space is limited, and excessive stack usage can lead to a stack overflow exception.
• Heap provides a larger block of memory, making it more suitable for dynamic memory allocation where the size is not known at compile time.

For scenarios where speed is critical, stack allocation can be preferred, while heap allocation is more flexible and suitable for larger memory requirements.

Your demonstration and benchmarking effectively highlighted the performance differences between these allocation methods.