What will the tape array be like in a triangular iteration space?

[roastduck]

Hi,

I have a question on how Enzyme will generate tape arrays for intermediate values. If I want to differentiate the following program with triangular iteration space, what will the tape array of x be like?

for (int i = 0; i < n; i++) {
  for (int j = 0; j < i + 1; j++) {
    double x = ...;
    use(x);
  }
}

Will it be an array of size n * (n + 1) / 2 (the best case), or an array of size n * n (a single array with relaxed size), or an array of arrays of size from 1 to n, or will there be an array with unknown size when allocated but growing dynamically?