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java.lang.Objectorg.apache.mahout.cf.taste.impl.similarity.CachingItemSimilarity
public final class CachingItemSimilarity
Caches the results from an underlying ItemSimilarity
implementation.
Constructor Summary | |
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CachingItemSimilarity(ItemSimilarity similarity,
DataModel dataModel)
Creates a CachingItemSimilarity on top of the given ItemSimilarity . |
|
CachingItemSimilarity(ItemSimilarity similarity,
int maxCacheSize)
Creates a CachingItemSimilarity on top of the given ItemSimilarity . |
Method Summary | |
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double[] |
itemSimilarities(long itemID1,
long[] itemID2s)
A bulk-get version of ItemSimilarity.itemSimilarity(long, long) . |
double |
itemSimilarity(long itemID1,
long itemID2)
Returns the degree of similarity, of two items, based on the preferences that users have expressed for the items. |
void |
refresh(java.util.Collection<Refreshable> alreadyRefreshed)
Triggers "refresh" -- whatever that means -- of the implementation. |
Methods inherited from class java.lang.Object |
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clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Constructor Detail |
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public CachingItemSimilarity(ItemSimilarity similarity, DataModel dataModel) throws TasteException
CachingItemSimilarity
on top of the given ItemSimilarity
.
The cache is sized according to properties of the given DataModel
.
TasteException
public CachingItemSimilarity(ItemSimilarity similarity, int maxCacheSize)
CachingItemSimilarity
on top of the given ItemSimilarity
.
The cache size is capped by the given size.
Method Detail |
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public double itemSimilarity(long itemID1, long itemID2) throws TasteException
ItemSimilarity
Returns the degree of similarity, of two items, based on the preferences that users have expressed for the items.
itemSimilarity
in interface ItemSimilarity
itemID1
- first item IDitemID2
- second item ID
Double.NaN
similarity is unknown
NoSuchItemException
- if either item is known to be non-existent in the data
TasteException
- if an error occurs while accessing the datapublic double[] itemSimilarities(long itemID1, long[] itemID2s) throws TasteException
ItemSimilarity
A bulk-get version of ItemSimilarity.itemSimilarity(long, long)
.
itemSimilarities
in interface ItemSimilarity
itemID1
- first item IDitemID2s
- second item IDs to compute similarity with
NoSuchItemException
- if any item is known to be non-existent in the data
TasteException
- if an error occurs while accessing the datapublic void refresh(java.util.Collection<Refreshable> alreadyRefreshed)
Refreshable
Triggers "refresh" -- whatever that means -- of the implementation. The general contract is that any should always leave itself in a consistent, operational state, and that the refresh atomically updates internal state from old to new.
refresh
in interface Refreshable
alreadyRefreshed
- s that are known to have already been
refreshed as a result of an initial call to a method on some
object. This ensure that objects in a refresh dependency graph aren't refreshed twice
needlessly.
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