Re: programming DeleteRepetitions Correction

*To*: mathgroup at smc.vnet.net*Subject*: [mg23777] Re: [mg23662] programming DeleteRepetitions Correction*From*: "Allan Hayes" <hay at haystack.demon.co.uk>*Date*: Sat, 10 Jun 2000 02:59:23 -0400 (EDT)*References*: <8gv88o$5n7@smc.vnet.net> <8hfegm$hnf@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Please change DF to DR in the code in my previous posting - appologies for the partial editing. I have made this correction in the copy below. ------- Bob, I have added to your codings and done more timing. The full list is {DR1, ...., DR9} DR1 is a new version using Splot DR2 is Carl Woll's code that I gave before (tidied up) DR3 is a faster rewrite of your DeleteRepetitions1 DR5 is your DeleteRepetitions1 The rest are your other examples reordered (your numbering is given against the code). In the timings: test[r, n] gives the timings for DR1, ...DRn on a list of 1000 random integers between 1 and r. DR6, your DeleteRepetitions6, is fastest up to r = 20. **TIMINGS** test[2, 9] {0.11, 0.06, 0., 0.22, 0.05, 0., 0.17, 0., 1.37} test[10, 8] {0.17, 0.05, 0.06, 0.22, 0.05, 0., 0.55, 0.} test[20, 8] {0.11, 0.05, 0.11, 0.22, 0.11, 0., 1.16, 0.16} test[30, 8] {0.1, 0.06, 0.11, 0.22, 0.11, 0.11, 1.49, 2.47} test[40, 8] {0.11, 0.05, 0.17, 0.38, 0.17, 0.16, 1.87, 4.28} test[60, 6] {0.11, 0.11, 0.22, 0.27, 0.22, 0.66} test[100, 6] {0.16, 0.06, 0.05, 0.49, 0.44, 0.61} test[200, 6] {0.11, 0.17, 0.11, 0.49, 0.94, 3.57} test[400, 6] {0.17, 0.27, 0.16, 0.94, 2.42, 4.99} test[600, 6] {0.16, 0.28, 0.22, 1.43, 3.79, 6.53} test[1000, 6] {0.16, 0.39, 0.33, 3.07, 5.93, 7.75} test[1000000000000, 6] (*almost certainly no repetitions*) {0.38, 0.55, 5.05, 5.28, 5.16, 5.33} ** CODE** (*1*) ... (*6*) indicateBob Hanlon's numbering. Remove["`*"]; DR1[x_List] := Last[Transpose[ Sort[Reverse /@ First /@ Split[Sort[ Transpose[{x, Range[Length[x]]}]], #1[[1]] == #2[[1]] &]]]]; DR2[x_List] := Block[{i}, i[n_] := (i[n] = Sequence[]; n); i /@ x]; DR3[x_List] := x[[Sort[Flatten[First[Position[x, #]] & /@ Union[x]]]]]; (*2*)DR4[x_List] := Module[{uniq = {}}, If[Not[MemberQ[uniq, #]], (uniq = Append[uniq, #])] & /@ x; uniq]; (*1*)DR5[x_List] := Take[x, #] & /@ Sort[First /@ (Position[x, #] & /@ Union[x])] // Flatten; (*6*)DR6[x_List] := Module[{uniq = Union[x], n, portion}, n = Length[uniq]; While[(Union[portion = Take[x, n]]) != uniq, n++]; Take[portion, #] & /@ Sort[First /@ (Position[portion, #] & /@ uniq)] // Flatten]; (*2*)DR7[x_List] := Transpose[ Union[Transpose[Join[{Range[Length[x]]}, {x}]], SameTest -> (#1[[2]] == #2[[2]] &)]][[2]] (*5*)DR8[x_List] := Module[{uniq = Union[x], n, portion}, n = Length[uniq]; While[(Union[portion = Take[x, n]]) != uniq, n++]; portion //. {a___, b_, c___, b_, d___} -> {a, b, c, d}] (*4*)DR9[x_List] := x //. {a___, b_, c___, b_, d___} -> {a, b, c, d} **TEST CODE** funcs = ToExpression[Names["DF*"]] {DR1, DR2, DR3, DR4, DR5, DR6, DR7, DR8, DR9} SameQ @@ Through[funcs[Table[Random[Integer, {1, 10}], {100}]]] True test[r_, n_] := With[{lst = Table[Random[Integer, {1, r}], {1000}]}, Timing[#[lst]][[1]]/Second & /@ Take[funcs, n]] ----------------- Allan --------------------- Allan Hayes Mathematica Training and Consulting Leicester UK www.haystack.demon.co.uk hay at haystack.demon.co.uk Voice: +44 (0)116 271 4198 Fax: +44 (0)870 164 0565