Re: My review of Decimal

From: John Maddock (jz.maddock_at_[hidden])
Date: 2025-01-21 14:36:17

> General Comments
>
> Counting Digits - It's easy to say a binary search tree is a naive implementation. A CLZ based implementation from blog posts by Daniel Lemire and Junekey Jeon can be found on branch `better_count_dig`. I found it actually benchmarked worse on a number of platforms.
It's worth emphasizing that simple code will always run faster for 
simple problems than a theoretically better but more complex algorithm: 
the classic example is that a linear search will generally beat a binary 
search when the number of items are low. There should probably be a 
comment in the code indicating that the alternative has been tried and 
was found to be slower though.
> "Only interesting design question is if functions producing new value should be void returning and
> modify inplace argument passed by reference(as for example std::ranges::sort does) or they
> should be returning a value." - I don't see any advantage to this as it would be a serious departure from expectations and norms.
>
> Taking decimal types by reference instead of by value - fundamentally the decimalXX types are std::uint32_t, std::uint64_t, and struct { uint64_t hi, uint64_t lo }. I don't think you'll see any performance improvements with those. Maybe for the fast types? Those are still reasonably small structs. We can try a few.

It may be worth the experiment, but I'd be surprised if adding a level 
of indirection is of benefit over passing arguments by value in a couple 
of registers: possibly there may be benefit for functions accepting many 
arguments, but I'm assuming there aren't too many of those?

John.