Is this normal? I use Matlab and my school super computer's 28 core node.
My model has 5 state variables.
It takes 20 hours for my macro model to solve on my school's computer

It depends on how OP has discretized his or her state space and whether the underlying variables are naturally discrete or continuous. Also depends on the nature of the optimization problem for each point in the state space (e.g., root finding or bruteforce).

It depends on how OP has discretized his or her state space and whether the underlying variables are naturally discrete or continuous. Also depends on the nature of the optimization problem for each point in the state space (e.g., root finding or bruteforce).
It matters, but not in the magnitude of 20 h vs a few mins.

Is this normal? I use Matlab and my school super computer's 28 core node.
My model has 5 state variables.Op, no generic info from here will help.
1) are individual iterations taking too long, or is it taking too many interactions? The solution will be very different depending on each case. Figure it out.
2) in the former case: matlab has a great profiler. Use it to figure out what is taking the time.
3) in the latter case: analyze the behavior of the value function over the iterations to see what's going on. Experiment with optimization choices, algorithms etc.