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@lshifr lshifr/LazyTuples.m
Last active Nov 3, 2017

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Implementation of lazy tuple list, for Streaming framework
BeginPackage["LazyTuples`"]
LazyTuples::usage = "LazyTuples[lists, opts] create a LazyList of the specified chunk size (\"ChunkSize\" option), containing tuples of the original lists";
Begin["`Private`"]
Needs["Streaming`"];
ClearAll[next];
next[{left_, _}, dim_] :=
{left - dim*(# - 1), #} &[IntegerPart[(left - 1)/dim] + 1];
ClearAll[multiDims];
multiDims[dims_] := Rest @ Reverse @ FoldList[Times, 1, Reverse @ dims];
ClearAll[multiIndex];
multiIndex[pos_, dims : {__Integer}] :=
Rest@FoldList[next, {pos, 0}, multiDims@dims][[All, 2]]
ClearAll[take];
take[lists : {__List}, {start_, end_}] :=
With[{rend = Min[end, Times @@ Map[Length, lists]]},
Transpose @ MapThread[
Part,
{lists, multiIndex[Range[start, rend], Length /@ lists]}
]
];
ClearAll[$iteratorChunkSize];
ClearAll[lazyTuplesVirtual];
lazyTuplesVirtual[lists:{__List}, chsize:_Integer?Positive:$iteratorChunkSize]:=
With[{
takeFun =
Function[index,
Function[
take[lists, {(index-1) * chsize+1, index * chsize}]
]
]
},
LazyListCreate[
Streaming`PackageScope`VirtualChunkGeneratorMake[takeFun,{}],
Function[index, If[# === 0, -1, #] & @ Length @ takeFun[index][]],
"FiniteList" -> True
]
];
ClearAll[makeTupleIterator];
makeTupleIterator[lists:{__List}, chunkSize_Integer?Positive]:=
With[{len = Times @@ Map[Length, lists]},
Module[{ctr = 0, active = False},
IteratorCreate[
ListIterator,
(active = True) &,
Function[
If[ctr >= len,
{},
(* else *)
With[{taken = take[lists, {ctr+1, Min[ctr + chunkSize, len]}]},
ctr += Length[taken];
taken
]
]
],
TrueQ[active] &,
Remove[active, ctr]&
]
]
];
ClearAll[lazyTuplesIterative];
lazyTuplesIterative[lists:{__List}, chunkSize:_Integer?Positive:$iteratorChunkSize]:=
LazyListCreate[makeTupleIterator[lists, chunkSize], chunkSize];
$iteratorChunkSize = 100000;
ClearAll[lazyTuples];
lazyTuples["Iterator"] = lazyTuplesIterative;
lazyTuples["Virtual"] = lazyTuplesVirtual;
lazyTuples[_][args___]:= $Failed;
ClearAll[LazyTuples];
Options[LazyTuples] = {
"Method" -> "Iterator",
"ChunkSize" :> $iteratorChunkSize
};
LazyTuples[lists_, opts:OptionsPattern[]]:=
lazyTuples[OptionValue["Method"]][lists, OptionValue["ChunkSize"]];
End[]
EndPackage[]
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