Dynamic Arrays

Dynamic arrays in SystemVerilog bring added flexibility compared to their fixed-size counterparts. Their size can be changed at runtime, making them suitable for a wider range of situations, especially when you don't know the array's size during compile-time.

Declaration and Usage

Dynamic arrays are declared in a similar way to fixed-size arrays, but without specifying a size. The syntax is as follows:

datatype array_name[];

For example, to declare a dynamic integer array:

integer dynamic_array[];

The size of the dynamic array can be set or changed at runtime using the new keyword followed by the desired size in brackets:

dynamic_array = new[10]; // Allocate size for 10 elements

Dynamic arrays can also be resized later in the code:

dynamic_array = new[20]; // Resize array to hold 20 elements

To access elements in a dynamic array, use the array name followed by the index of the element in square brackets:

dynamic_array[0] = 5; // Sets the first element of dynamic_array to 5

Characteristics and Use Cases

Dynamic arrays offer significant flexibility, but this comes at the cost of a slight overhead in terms of memory and performance. However, this is generally not a concern unless you're working with very large data sets.

Dynamic arrays are used in a variety of situations where the number of elements is not known ahead of time or can change during execution. These situations might include storing the results of a testbench that can have a variable number of outputs, or storing a list of errors detected during verification that can vary between runs.

While dynamic arrays are powerful, they are still indexed arrays and require you to manage the indices. If you need an array with arbitrary indexing, an associative array might be a better choice. Similarly, if you need to frequently insert or delete elements at both ends of the array, you might find a queue more suitable.

In the next section, we will delve into associative arrays, exploring their features, use cases, and how to use them effectively in SystemVerilog.