Hi;

I'm working on the Rosetta Code task:

"Stirling numbers of the second kind"

I have a working recursive solution written in Ada but I'd like to memoize it to cut down on the redundant and duplicative calls (similar to a recursive solution to calculating the Fibonacci sequence).

So I think I need a hash ADT (which I've used in Perl) but I've never used in Ada.

So I want to preserve the calculation of the Stirling2 for each N and K so I can do a lookup. If this were based on a single unsigned integer, an array would suffice. Maybe a 2d array would suffice?

Thanks,
Ken Wolcott

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On Friday, July 21, 2023 at 8:50:06 PM UTC-7, Kenneth Wolcott wrote:

Hi;

I'm working on the Rosetta Code task:

"Stirling numbers of the second kind"

I have a working recursive solution written in Ada but I'd like to memoize it to cut down on the redundant and duplicative calls (similar to a recursive solution to calculating the Fibonacci sequence).

So I think I need a hash ADT (which I've used in Perl) but I've never used in Ada.

So I want to preserve the calculation of the Stirling2 for each N and K so I can do a lookup. If this were based on a single unsigned integer, an array would suffice. Maybe a 2d array would suffice?

Thanks,
Ken Wolcott

I solved the specific problem using a 2d array for caching. This is not memoization, per se, but this works very well. The recursive calls are now very fast as there is a maximum of one calculation per recursive call.

So, any resources on how to write Ada programs that take advantage of memoization?

Thanks,
Ken

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So, any resources on how to write Ada programs that take advantage of memoization?

Look here https://forum.ada-lang.io/ for discussions about Advent of Code puzzles. Some solutions use (and need, for completing in a reasonable time) memoization.
You find with HAC ( https://hacadacompiler.sourceforge.io/ ) a set of solutions (search "memoiz*" or "cache"), mostly compiling with the HAC subset.

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On Monday, July 24, 2023 at 2:18:28 PM UTC-7, Gautier write-only address wrote:

So, any resources on how to write Ada programs that take advantage of memoization?

Look here https://forum.ada-lang.io/ for discussions about Advent of Code puzzles. Some solutions use (and need, for completing in a reasonable time) memoization.
You find with HAC ( https://hacadacompiler.sourceforge.io/ ) a set of solutions (search "memoiz*" or "cache"), mostly compiling with the HAC subset.

Thanks for the pointer to the forum.

Regarding HAC, isn't that Windows-only? I'm on a Mac (M1 chip). I'll look again at HAC.

Ken

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Kenneth Wolcott <kennethwolcott@gmail.com> writes:

Regarding HAC, isn't that Windows-only? I'm on a Mac (M1 chip). I'll
look again at HAC.

It worked well enough for me to find a failing test case (now fixed!)

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Regarding HAC, isn't that Windows-only?

Not at all :-)

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On Wednesday, July 26, 2023 at 2:36:17 PM UTC-7, Gautier write-only address wrote:

Regarding HAC, isn't that Windows-only?

Not at all :-)

Downloaded and ran demo. Will experiment further as time permits. Nice!

Thanks,
Ken

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