ASIC Verification Interview Series Blog #1

06.11.25 11:11 AM - By Advane Harshal

How to Swap Two Elements in a 2D Array in SystemVerilog

Breaking into the world of ASIC verification requires far more than a surface-level understanding of SystemVerilog or just crafting functional scripts. Leading semiconductor companies focus their interviews on how you approach complex problems, your grasp of underlying principles, and your familiarity with industry best practices. What might look like simple interview questions often serve as windows into your mindset for debugging, handling corner cases, and clearly articulating your solutions.
That’s exactly what inspired me to launch this blog series.


In ASIC verification interviews, candidates are tested not only on their ability to write SystemVerilog code, but also on their capacity to reason about robustness, best practices, and simulation safety. By showing how to turn a naive solution into a professional one, this series teaches how and why to code correctly for real-world verification!

The Simple, Naive Swap Function
Let's start with a basic swap function. This version skips safety checks and doesn't use ref, making it easy to understand but unsafe
// Naive swap (not robust)
function void simple_swap(byte arr[][], int i1, int j1, int i2, int j2);

    byte temp;

    temp = arr[i1][j1];

    arr[i1][j1] = arr[i2][j2];

    arr[i2][j2] = temp;

endfunction


Problems in the Naive Version
  • No boundary checks: Can crash simulation if indices are wrong
  • Pass by value: The array isn't changed outside the function call.
  • No debug info: Hard to verify in larger testbenches.

2. The Robust, Interview-Ready Swap Function

Now we upgrade the code for real projects and interviews, using ref and validation.


// Robust swap with checks and ref


function void swap_2d_elements(ref byte arr[][], int i1, int j1, int i2, int j2);


    if (i1 >= arr.size() || i2 >= arr.size() || j1 >= arr[0].size() || j2 >= arr[0].size()) begin


        $error("swap_2d_elements: Index out of bounds (%0d,%0d), (%0d,%0d)", i1, j1, i2, j2);


        return;


    end


    byte temp = arr[i1][j1];


    arr[i1][j1] = arr[i2][j2];


    arr[i2][j2] = temp;


    $display("Swapped arr[%0d][%0d] with arr[%0d][%0d]", i1, j1, i2, j2);


endfunction

Takeaways

    1. Start with simple code for clarity.
    2. Make your solution robust: use ref and validate indices.
    3. Add debug output so others can quickly verify your logic.
    4. Explain these improvements in interviews—they prove your maturity as a verification engineer!
Get Started Now

Advane Harshal

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