96 lines
2.4 KiB
Text
96 lines
2.4 KiB
Text
procedure StrongWeakPrimes(Memo: TMemo);
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{Display Strong/Weak prime information}
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var I,P: integer;
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var Sieve: TPrimeSieve;
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var S: string;
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var Cnt,Cnt1,Cnt2: integer;
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type TPrimeTypes = (ptStrong,ptWeak,ptBalanced);
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function GetTypeStr(PrimeType: TPrimeTypes): string;
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{Get string describing PrimeType}
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begin
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case PrimeType of
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ptStrong: Result:='Strong';
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ptWeak: Result:='Weak';
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ptBalanced: Result:='Balanced';
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end;
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end;
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function GetPrimeType(N: integer): TPrimeTypes;
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{Return flag indicating type of prime Primes[N] is}
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{Strong = Primes(N) > [Primes(N-1) + Primes(N+1)] / 2}
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{Weak = Primes(N) < [Primes(N-1) + Primes(N+1)] / 2}
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{Balanced = Primes(N) = [Primes(N-1) + Primes(N+1)] / 2}
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var P,P1: double;
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begin
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P:=Sieve.Primes[N];
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P1:=(Sieve.Primes[N-1] + Sieve.Primes[N+1]) / 2;
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if P>P1 then Result:=ptStrong
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else if P<P1 then Result:=ptWeak
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else Result:=ptBalanced;
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end;
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procedure GetPrimeCounts(PT: TPrimeTypes; var Cnt1,Cnt2: integer);
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{Get number of primes of type "PT" below 1 million and 10 million}
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var I: integer;
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begin
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Cnt1:=0; Cnt2:=0;
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for I:=1 to 1000000-1 do
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begin
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if GetPrimeType(I)=PT then
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begin
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if Sieve.Primes[I]>10000000 then break;
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Inc(Cnt2);
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if Sieve.Primes[I]<1000000 then Inc(Cnt1);
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end;
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end;
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end;
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function GetPrimeList(PT: TPrimeTypes; Limit: integer): string;
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{Get a list of primes of type PT up to Limit}
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var I,Cnt: integer;
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begin
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Result:='';
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Cnt:=0;
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for I:=1 to Sieve.PrimeCount-1 do
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if GetPrimeType(I)=PT then
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begin
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Inc(Cnt);
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P:=Sieve.Primes[I];
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Result:=Result+Format('%5d',[P]);
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if Cnt>=Limit then break;
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if (Cnt mod 10)=0 then Result:=Result+CRLF;
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end;
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end;
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procedure ShowPrimeTypeData(PT: TPrimeTypes; Limit: Integer);
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{Display information about specified PrimeType, listing items up to Limit}
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var S,TS: string;
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begin
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S:=GetPrimeList(PT,Limit);
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TS:=GetTypeStr(PT);
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Memo.Lines.Add(Format('First %d %s primes are:',[Limit,TS]));
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Memo.Lines.Add(S);
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GetPrimeCounts(PT,Cnt1,Cnt2);
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Memo.Lines.Add(Format('Number %s primes <1,000,000: %8.0n', [TS,Cnt1+0.0]));
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Memo.Lines.Add(Format('Number %s primes <10,000,000: %8.0n', [TS,Cnt2+0.0]));
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Memo.Lines.Add('');
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end;
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begin
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Sieve:=TPrimeSieve.Create;
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try
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Sieve.Intialize(200000000);
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Memo.Lines.Add('Primes in Sieve : '+IntToStr(Sieve.PrimeCount));
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ShowPrimeTypeData(ptStrong,36);
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ShowPrimeTypeData(ptWeak,37);
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ShowPrimeTypeData(ptBalanced,28);
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finally Sieve.Free; end;
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end;
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