My initial problem is that I need to implement a very fast, sparse array in C#. Original idea was to use a normal Dictionary<uint, TValue>
and wrap it in my own class to only expose the TValue
type parameter. Turns out this is pretty slow.
So my next idea was to map each integer in the needed range ( UInt32.MinValue
to UInt32.MaxValue
) to a bucket, of some size and use that. So I'm looking for a good way to map an unsigned integer X to a bucket Y, for example:
Mapping the numbers 0-1023 to 8 different buckets holding 128 numbers each, 0-127, 128-255.
But if someone has a better way of implementing a fast sparse array in C#, that would be most appreciated also.
I, too, noticed that Dictionary<K,V>
is slow when the key is an integer. I don't know exactly why this is the case, but I wrote a faster hash-table implementation for uint
and ulong
keys:
Caveats/downsides:
The 64-bit one (key is ulong
) is generic, but the other one (key is uint
) assumes int
values because that's all I needed at the time; I'm sure you can make this generic easily.
Currently the capacity determines the size of the hashtable forever (ie it doesn't grow).
There are a 101 different ways to implement sparse arrays depending on factors like:
Most textbooks have a section on sparse array, just doing a Google comes up with lots of hits. You will then have to translate the code into C#, or just use the code someone else has written, I have found two without much effort (I don't know how good these are)
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