Learn to enhance your performance with stackalloc in C#. Discover a better approach on Day 28 of our 30-Day .NET Challenge.
Introduction
.Net applications rely on a Garbage collector for memory allocation and deallocation, which simplifies memory management but leads to performance degradation if not managed efficiently. The article demonstrates how to use stackalloc to enhance application performance.
Learning Objectives
Understanding what is stackalloc
Problem with traditional heap allocation
Optimal use of stackalloc
Prerequisites for Developers
Basic understanding of C# programming language.
Familiar with for loops
Getting Started
Understanding what is stackalloc
Stackalloc is a reserved keyword in C# which helps to allocate memory on the stack instead of heap which is managed by Garbage Collector whereas stack allocation is automatically freed once method execution ends.
Problem with traditional heap allocation
Consider the following code example wherein the memory for the double array is allocation on the heap.
private double CalculateSum(double[] values)
{
double sum = 0;
for (int i = 0; i < values.Length; i++)
{
sum += values[i];
}
return sum;
}
If the aforementioned method is called frequently, then it creates an overhead for garbage collection which slows down the application performance.
Optimal use of stackalloc
Please find below the refactored version of the previous code snippet
private unsafe double CalculateSum(int count)
{
double sum = 0;
double* values = stackalloc double[count]; // Allocate memory on the stack
for (int i = 0; i < count; i++)
{
values[i] = SomeValue(i); // Assume SomeValue is a method returning a double
sum += values[i];
}
return sum;
}
In the above method, the values are allocated on stack rather than heap. In this approach there is no need for garbage collection, leading to faster execution and can reduce the pressure on GC.
For performance-sensitive applications, memory management is critical hence using stackalloc a developer can perform memory allocation/deallocation efficiently.
Complete Code
Create another class named StackAlloc and add the following code snippet
public static class StackAlloc
{
static int count = 10000; // Number of elements
static double[] values = new double[count];
public static void BadWay() {
FillValues(values);
// Calculate sum using heap allocation
double heapSum = CalculateSumHeap(values);
Console.WriteLine($"Heap allocation sum: {heapSum}");
}
public static void GoodWay()
{
FillValues(values);
// Calculate sum using stackalloc
double stackSum = CalculateSumStackalloc(count);
Console.WriteLine($"Stackalloc sum: {stackSum}");
}
private static void FillValues(double[] values)
{
for (int i = 0; i < values.Length; i++)
{
values[i] = SomeValue(i);
}
}
private static double SomeValue(int i)
{
// Just a sample value function
return i * 2.5;
}
private static double CalculateSumHeap(double[] values)
{
double sum = 0;
for (int i = 0; i < values.Length; i++)
{
sum += values[i];
}
return sum;
}
private static unsafe double CalculateSumStackalloc(int count)
{
double sum = 0;
double* values = stackalloc double[count];
for (int i = 0; i < count; i++)
{
values[i] = SomeValue(i);
sum += values[i];
}
return sum;
}
}
Execute from the main method as follows
#region Day 28: Use Stackalloc
static string ExecuteDay28()
{
StackAlloc.BadWay();
StackAlloc.GoodWay();
return "Executed Day 28 successfully..!!";
}
#endregion
Console Output
Heap allocation sum: 124987500
Stackalloc sum: 124987500
Complete Code on GitHub
GitHub — ssukhpinder/30DayChallenge.Net
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