checked_powd takes exponentially long time to complete about rust-decimal

[schungx]

The use case is actually exposing a function for users to call. If users put in a huge exponent, they may not expect the program to be running for 100 seconds and will think the program has hung. An error would be a much better solution in my case.

Thus, I'll limit the max exponent for users. That would make it more foolproof.

On your side I'd suggest a note on the API saying that it may take a long time to run if the exponent is large, as it may not be completely expected.

Thanks!

[Tony-Samuels]

It's certainly slow, but I wouldn't say it takes forever. As an example:

    let base = dec!(0.99999999999999);
    let exp = dec!(147728940);
    println!("Starting");
    let result = base.powd(exp);
    println!("{result}");
    let second_result = base.checked_powd(exp).unwrap();
    println!("{second_result}");

The powd's result is printed about 10 seconds after the previous message, and checked_powd takes the same amount of time. Increasing the exponent by a factor of ten again makes it take 100 seconds instead, so (with admittedly few data points) this seems linear with the exponent value rather than exponential.

I don't suppose you could explain a little more about your use case? What are you attempting to do where you want to attempt to calculate an exponential, giving up if it takes too long? Maybe there's another solution that would work better.