My program uses a very long list of (index,count) items. Index and count are Int's. The program updates the count values a lot. Therefor it uses the index as a key to update the belonging count value. After updating, the program needs the (index,count) pair with the least count value in the list. What is an approriate (fast) datastructure? My first idea was to use a heap. Problem with the heap is that I can't update the count value by its index fast. Any ideas? Kees
"Kees Bleijenberg"
My program uses a very long list of (index,count) items. Index and count are Int's. The program updates the count values a lot. Therefor it uses the index as a key to update the belonging count value. After updating, the program needs the (index,count) pair with the least count value in the list. What is an approriate (fast) datastructure? My first idea was to use a heap. Problem with the heap is that I can't update the count value by its index fast. Any ideas?
Try Data.IntMap and Data.Map. I think they have different asymptotics, but they both do exactly what you want, so try both. Because of the purity I would estimate the total query time to O(log n) and the total update time to O((log n)^2). Greets, Ertugrul -- nightmare = unsafePerformIO (getWrongWife >>= sex) http://ertes.de/
On Fri, Jul 15, 2011 at 11:42 AM, Kees Bleijenberg
My program uses a very long list of (index,count) items. Index and count are Int's. The program updates the count values a lot. Therefor it uses the index as a key to update the belonging count value. After updating, the program needs the (index,count) pair with the least count value in the list. What is an approriate (fast) datastructure? My first idea was to use a heap. Problem with the heap is that I can't update the count value by its index fast. Any ideas?
Do you need to be able to "remove" the pair that has the least count cheaply ? -- Jedaï
Jedaï,
On Fri, Jul 15, 2011 at 11:42 AM, Kees Bleijenberg
My program uses a very long list of (index,count) items. Index and count are Int's. The program updates the count values a lot. Therefor it uses the index as a key to update the belonging count value. After updating, the program needs the (index,count) pair with the least count value in the list. What is an approriate (fast) datastructure? My first idea was to use a heap. Problem with the heap is that I can't update the count value by its index fast. Any ideas?
Do you need to be able to "remove" the pair that has the least count cheaply ? Yes, that would be nice. But as an alternative I can give give it a very, very high count. I need an index to access the elements (just like a map) and the map should stay sorted on another 'field' then the key (or at least it should act as a heap for that 'non-key field'). Kees
On Jul 15, 2011, at 8:30 AM, Kees Bleijenberg wrote:
I need an index to access the elements (just like a map) and the map should stay sorted on another 'field' then the key (or at least it should act as a heap for that 'non-key field').
Kees
Hi, Kees. Have you looked into fingertrees? They give an enormously powerful way to express incremental computations over trees with big O logarithmic complexity.
____________________ David Place Owner, Panpipes Ho! LLC http://panpipesho.com d@vidplace.com
On Jul 15, 2011, at 8:30 AM, Kees Bleijenberg wrote:
need an index to access the elements (just like a map) and the map should stay sorted on another 'field' then the key (or at least it should act as a heap for that 'non-key field').
More on fingertrees. In fact, i think this module in the fingertree package does exactly what you need.
http://hackage.haskell.org/packages/archive/fingertree/0.0.1.0/doc/html/Data...
____________________ David Place Owner, Panpipes Ho! LLC http://panpipesho.com d@vidplace.com
participants (4)
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Chaddaï Fouché -
David Place -
Ertugrul Soeylemez -
Kees Bleijenberg