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improve hash function #132

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Merged
gcarreno merged 1 commit into from
Apr 26, 2024
Merged

improve hash function #132

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11 changes: 9 additions & 2 deletions entries/ghatem-fpc/src/onebrc.pas
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Original file line number Diff line number Diff line change
Expand Up @@ -11,7 +11,7 @@ interface
function RoundExDouble(const ATemp: Double): Double; inline;

const
cDictSize: Integer = 45000;
cDictSize: Integer = 45003;

type

Expand Down Expand Up @@ -128,11 +128,18 @@ function Compare(AList: TStringList; AIndex1, AIndex2: Integer): Integer;

{ TMyDictionary }

const
cHashConst: Double = (Sqrt(5) - 1) / 2;

procedure TMyDictionary.InternalFind(const aKey: Cardinal; out aFound: Boolean; out aIndex: Integer);
var vIdx: Integer;
vDbl: Double;
vOffset: Integer;
begin
vIdx := aKey mod cDictSize;
vDbl := aKey * cHashConst;
vDbl := vDbl - Trunc (vDbl);
vIdx := Trunc (vDbl * cDictSize);

aFound := False;

if FHashes[vIdx] = aKey then begin
Expand Down