This package provides memoised functions. A memoised function wraps an ordinary GAP function, and caches its outputs so that they do not need to be computed again later. This cache is stored in a permanent format that persists between different GAP sessions, different users, and even different locations. It is also compatible with the pypersist library for Python, allowing results to be shared between GAP and Python or Sage.
The following example shows a simple use of MemoisedFunction (2.1-1) to begin caching the results of a function to disk.
gap> triple := x -> x * 3; function( x ) ... end gap> mtriple := MemoisedFunction(triple); <memoised function( x ) ... end> gap> mtriple(3); #I Memo key: [ 3 ] #I Key unknown. Computing result... 9 gap> mtriple(3); #I Memo key: [ 3 ] #I Key known! Loading result from cache... 9
The memoised function mtriple behaves just like the function triple that it wraps, but if the same call is repeated, its result is loaded from the cache instead of being recomputed. This cache even persists across sessions!
Additional options can be specified, as shown here:
gap> msize := MemoisedFunction(Size, rec(key := GeneratorsOfGroup, > storekey := true, > cache := "file://~/Desktop/mycache")); <memoised <Attribute "Size">> gap> msize(SymmetricGroup(6)); #I Memo key: [ (1,2,3,4,5,6), (1,2) ] #I Key unknown. Computing result... 720 gap> msize(Group((5,6,1,2,3,4), (1,2))); #I Memo key: [ (1,2,3,4,5,6), (1,2) ] #I Key known! Loading result from cache... 720
All these options are explained in the next chapter.
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