fibonacciIter is not even optimized...

fiboperf.zig

const std = @import("std");
const time = std.time;

pub fn main() anyerror!void {
    const fibo_arg = 30;
    var start = time.nanoTimestamp();
    var end = time.nanoTimestamp();
    std.debug.print("noop                            - {}ns\n", .{end - start});
    start = time.nanoTimestamp();
    var result = fibonacciRecurse(fibo_arg);
    end = time.nanoTimestamp();
    std.debug.print("fibonacciRecurse({}) -> {} - {}ns\n", .{ fibo_arg, result, end - start });
    start = time.nanoTimestamp();
    result = fibonacciIter(fibo_arg);
    end = time.nanoTimestamp();
    std.debug.print("fibonacciIter({}) -> {}    - {}ns\n", .{ fibo_arg, result, end - start });
}

fn fibonacciRecurse(n: u64) u64 {
    return if (n < 2) 1 else fibonacciRecurse(n - 1) + fibonacciRecurse(n - 2);
}

fn fibonacciIter(n: u64) u64 {
    if (n < 2) return n;
    var result: u64 = 1;
    var prev: u64 = 1;
    var it: u64 = 2;
    while (it <= n) {
        const before = result;
        result += prev;
        prev = before;
        it += 1;
    }
    return result;
}