N'th Fibonacci sequence function fails to output result when n > 35

[partylikeits1983]

Describe the bug When running the fib.bend program with an input value larger than 30, the time to generate an output becomes unusably slow.

In contrast, running the same program in Rust produces a near-instant output. This might be due to the fib.bend program not being parallelizable.

fib.bend (very slow):

add = λa λb (+ a b)

fib = λx switch x {
  0: 1
  _: let p = x-1; switch p {
    0: 1
    _: (+ (fib p) (fib p-1))
  }
}

main = (fib 30)

fibonacci in rust (near instant)

fn fibonacci(n: u32) -> u64 {
  if n == 0 {
      return 0;
  }
  let mut prev = 0;
  let mut curr = 1;
  for _ in 1..n {
      let next = prev + curr;
      prev = curr;
      curr = next;
  }
  curr
}

fn main() {
  let n = 31;
  let fib_n = fibonacci(n);
  println!("{}", fib_n);
}

To Reproduce

Run fib.bend with a value larger than 30.

Expected behavior Similar output speed to Rust.

Desktop (please complete the following information): OS: macOS CPU: M2 Pro

Additional context Just wondering why it is slow. Does the program need to be compiled into HVM first and then executed to run fast?