Question

I’m building a simulator for a 40 card’s deck game. The deck is divided into 4 seeds, each one with 10 cards. Since there’s only 1 seed that’s different from the others ( let’s say, hearts ) , I’ve thinked of a quite convinient way to store a set of 4 cards with the same value in 3 bits: the first two indicate how many cards of a given value are left, and the last one is a marker that tells if the heart card of that value is still in the deck.
So,

{7h 7c 7s} = 101

That allows me to store the whole deck on 30 bits of memory instead of 40. Now, when i was programming in C, I’d have allocated 4 chars ( 1 byte each = 32 bits), and played with the values with bit operations.
In C# I can’t do that, since chars are 2 bytes each and playing with bits is much more of a pain, so, the question is : what’s the smallest amount of memory I’ll have to use to store the data required?

PS: Keep in mind that i may have to allocate 100k+ of those decks in system’s memory, so saving 10 bits is quite a lot

Answer 1

in C, I’d have allocated 3 chars ( 1 byte each = 32 bits)

3 bytes gives you 24 bits, not 32… you need 4 bytes to get 32 bits. (Okay, some platforms have non-8-bit bytes, but they’re pretty rare these days.)

In C# I can’t do that, since chars are 2 bytes each

Yes, so you use byte instead of char. You shouldn’t be using char for non-textual information.

and playing with bits is much more of a pain

In what way?

But if you need to store 30 bits, just use an int or a uint. Or, better, create your own custom value type which backs the data with an int, but exposes appropriate properties and constructors to make it better to work with.

PS: Keep in mind that i may have to allocate 100k+ of those decks in system’s memory, so saving 10 bits is quite a lot

Is it a significant amount though? If it turned out you needed to store 8 bytes per deck instead of 4 bytes, that means 800M instead of 400M for 100,000 of them. Still less than a gig of memory. That’s not that much…