Pagina's

2011/07/05

Fibonacci numbers part 1

//  Fibonacci(1000000) in 105 mS (Athlon X4 640, XP, 2GB)

//  Two formulas:
//    
//  F[2n-1] = F[n-1]^2 + F[n]^2
//    
//  F[2n]   = (2*F[n-1] + F[n]) * F[n]  
//    
//  http://www.maths.surrey.ac.uk/hosted-sites/R.Knott/Fibonacci/fibFormula.html?n=55

//  Fibs(66) 
//  66 = 1000010
//       10000..  = 16 F0 = fibSmall(16) = 987                         = F(16)
//                     F1 = fibSmall(17) = 1597                        = F(17)
//                     F0 = (2*F1-F0)*F0 = (2*1597-987)*987  = 2178309 = F(32)
//                     F1 = F1*F1+F0*F0  = 1597*1597+987*987 = 3524578 = F(33)
//       .....1.       F0 = F1           = 3524578                     = F(33)
//                     F1 = F1+F0        = 3524578+2178309   = 5702887 = F(34)
//                     F0 = (2*F1-F0)*F0 = 27777890035288              = F(66)
//                     F1 = F1*F1+F0*F0  = 44945570212853              = F(67)
//       ......0       no change
//    
//  Fibs(66) = { Fib(66), Fib(67) } = { 27777890035288, 44945570212853 }

//                    +--------------------------------+
//                    | Fibonacci.exe in milliSeconds  |
//                    |--------------------------------|
//                    |    n    | F(n) | F(n+1)|Fibs(n)|
//                    |--------------------------------|
//                    |  156250 |   10 |    13 |    15 |
//                    |  312500 |   23 |    28 |    37 |
//                    |  625000 |   57 |    73 |    93 |
//                    | 1250000 |  148 |   198 |   255 |
//                    | 2500000 |  406 |   515 |   676 |
//                    | 5000000 | 1110 |  1420 |  1860 |
//                    |10000000 | 3010 |  3800 |  4930 | 
//                    |20000000 | 8080 | 10400 | 13500 |
//                    +--------------------------------+

//            !!! Project >> Add Reference >> System.Numerics !!!

using Xint = System.Numerics.BigInteger;
using System.Threading.Tasks;
using System.Diagnostics;
using System;
class program
{
    private static int fibSmall(int n)
    {
        int[] f = { 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987,
                    1597, 2584, 4181, 6765, 10946, 17711, 28657, 46368, 75025,
                    121393, 196418, 317811, 514229, 832040, 1346269, 2178309, 3524578 };
        return f[n];
    }
    public static Xint Fib(int n)
    {
        if (n < 34) return fibSmall(n);
        int i = fL2(n) - 4;
        int m = n >> i;
        Xint[] F = { fibSmall(m++), fibSmall(m) };
        for (--i; i > 0; i--)
        {
            F = new Xint[2] { MTP(2 * F[1] - F[0], F[0]), SQ(F[1]) + SQ(F[0]) };
            if (((1 << i) & n) != 0) F = new Xint[2] { F[1], F[1] + F[0] };
        }
        if ((n & 1) == 0) return MTP(2 * F[1] - F[0], F[0]);
        return SQ(F[1]) + SQ(F[0]);
    }
    public static Xint[] Fibs(int n)
    {
        if (n < 33) return new Xint[2] { fibSmall(n++), fibSmall(n) };
        int i = fL2(n) - 4;
        int m = n >> i;
        Xint[] F = { fibSmall(m++), fibSmall(m) };
        for (--i; i >= 0; i--)
        {
            F = new Xint[2] { MTP(2 * F[1] - F[0], F[0]), SQ(F[1]) + SQ(F[0]) };
            if (((1 << i) & n) != 0) F = new Xint[2] { F[1], F[1] + F[0] };
        }
        return F;
    }


    private static Stopwatch sw = new Stopwatch();
    static void Main()
    {
        for (int i = 0; i < 20; i++)
        {
            sw.Restart(); Fib(1000000); sw.Stop(); Console.WriteLine(sw.ElapsedMilliseconds);
        }
        Console.ReadLine();
    }

    private static Xint MTP(Xint U, Xint V)
    {
        return MTP(U, V, Xint.Max(U.Sign * U, V.Sign * V).ToByteArray().Length << 3);
    }
    private static Xint MTP(Xint U, Xint V, int n)
    {
        if (n <= 3000) return U * V;
        if (n <= 6000) return TC2(U, V, n);
        if (n <= 10000) return TC3(U, V, n);
        if (n <= 40000) return TC4(U, V, n);
        return TC2P(U, V, n);
    }
    private static Xint MTPr(Xint U, Xint V, int n)
    {
        if (n <= 3000) return U * V;
        if (n <= 6000) return TC2(U, V, n);
        if (n <= 10000) return TC3(U, V, n);
        return TC4(U, V, n);
    }
    private static Xint TC2(Xint U1, Xint V1, int n)
    {
        n >>= 1;
        Xint Mask = (Xint.One << n) - 1;
        Xint U0 = U1 & Mask; U1 >>= n;
        Xint V0 = V1 & Mask; V1 >>= n;
        Xint P0 = MTPr(U0, V0, n);
        Xint P2 = MTPr(U1, V1, n);
        return ((P2 << n) + (MTPr(U0 + U1, V0 + V1, n) - (P0 + P2)) << n) + P0;
    }
    private static Xint TC3(Xint U2, Xint V2, int n)
    {
        n = (int)((long)(n) * 0x55555556 >> 32); // n /= 3;
        Xint Mask = (Xint.One << n) - 1;
        Xint U0 = U2 & Mask; U2 >>= n;
        Xint U1 = U2 & Mask; U2 >>= n;
        Xint V0 = V2 & Mask; V2 >>= n;
        Xint V1 = V2 & Mask; V2 >>= n;
        Xint W0 = MTPr(U0, V0, n);
        Xint W4 = MTPr(U2, V2, n);
        Xint P3 = MTPr((((U2 << 1) + U1) << 1) + U0, (((V2 << 1) + V1 << 1)) + V0, n);
        U2 += U0;
        V2 += V0;
        Xint P2 = MTPr(U2 - U1, V2 - V1, n);
        Xint P1 = MTPr(U2 + U1, V2 + V1, n);
        Xint W2 = (P1 + P2 >> 1) - (W0 + W4);
        Xint W3 = W0 - P1;
        W3 = ((W3 + P3 - P2 >> 1) + W3) / 3 - (W4 << 1);
        Xint W1 = P1 - (W4 + W3 + W2 + W0);
        return ((((W4 << n) + W3 << n) + W2 << n) + W1 << n) + W0;
    }
    private static Xint TC4(Xint U3, Xint V3, int n)
    {
        n >>= 2;
        Xint Mask = (Xint.One << n) - 1;
        Xint U0 = U3 & Mask; U3 >>= n;
        Xint U1 = U3 & Mask; U3 >>= n;
        Xint U2 = U3 & Mask; U3 >>= n;
        Xint V0 = V3 & Mask; V3 >>= n;
        Xint V1 = V3 & Mask; V3 >>= n;
        Xint V2 = V3 & Mask; V3 >>= n;

        Xint W0 = MTPr(U0, V0, n);                               //  0
        U0 += U2; U1 += U3;
        V0 += V2; V1 += V3;
        Xint P1 = MTPr(U0 + U1, V0 + V1, n);                     //  1
        Xint P2 = MTPr(U0 - U1, V0 - V1, n);                     // -1
        U0 += 3 * U2; U1 += 3 * U3;
        V0 += 3 * V2; V1 += 3 * V3;
        Xint P3 = MTPr(U0 + (U1 << 1), V0 + (V1 << 1), n);       //  2
        Xint P4 = MTPr(U0 - (U1 << 1), V0 - (V1 << 1), n);       // -2
        Xint P5 = MTPr(U0 + 12 * U2 + ((U1 + 12 * U3) << 2),
                       V0 + 12 * V2 + ((V1 + 12 * V3) << 2), n); //  4
        Xint W6 = MTPr(U3, V3, n);                               //  inf

        Xint W1 = P1 + P2;
        Xint W4 = (((((P3 + P4) >> 1) - (W1 << 1)) / 3 + W0) >> 2) - 5 * W6;
        Xint W2 = (W1 >> 1) - (W6 + W4 + W0);
        P1 = P1 - P2;
        P4 = P4 - P3;
        Xint W5 = ((P1 >> 1) + (5 * P4 + P5 - W0 >> 4) - ((((W6 << 4) + W4) << 4) + W2)) / 45;
        W1 = ((P4 >> 2) + (P1 << 1)) / 3 + (W5 << 2);
        Xint W3 = (P1 >> 1) - (W1 + W5);
        return ((((((W6 << n) + W5 << n) + W4 << n) + W3 << n) + W2 << n) + W1 << n) + W0;
    }
    private static Xint TC2P(Xint A, Xint B, int n)
    {
        n >>= 1;
        Xint Mask = (Xint.One << n) - 1;
        Xint[] U = new Xint[3];
        U[0] = A & Mask; A >>= n; U[2] = A; U[1] = U[0] + A;
        Xint[] V = new Xint[3];
        V[0] = B & Mask; B >>= n; V[2] = B; V[1] = V[0] + B;
        Xint[] P = new Xint[3];
        Parallel.For(0, 3, (int i) => P[i] = MTPr(U[i], V[i], n));
        return ((P[2] << n) + P[1] - (P[0] + P[2]) << n) + P[0];
    }

    private static Xint SQ(Xint U)
    {
        return SQ(U, U.Sign * U.ToByteArray().Length << 3);
    }
    private static Xint SQ(Xint U, int n)
    {
        if (n <= 700) return U * U;
        if (n <= 3000) return Xint.Pow(U, 2);
        if (n <= 6000) return SQ2(U, n);
        if (n <= 10000) return SQ3(U, n);
        if (n <= 40000) return SQ4(U, n);
        return SQ2P(U, n);
    }
    private static Xint SQr(Xint U, int n)
    {
        if (n <= 3000) return Xint.Pow(U, 2);
        if (n <= 6000) return SQ2(U, n);
        if (n <= 10000) return SQ3(U, n);
        return SQ4(U, n);
    }
    private static Xint SQ2(Xint U1, int n)
    {
        n >>= 1;
        Xint U0 = U1 & ((Xint.One << n) - 1); U1 >>= n;
        Xint P0 = SQr(U0, n);
        Xint P2 = SQr(U1, n);
        return ((P2 << n) + (SQr(U0 + U1, n) - (P0 + P2)) << n) + P0;
    }
    private static Xint SQ3(Xint U2, int n)
    {
        n = (int)((long)(n) * 0x55555556 >> 32);
        Xint Mask = (Xint.One << n) - 1;
        Xint U0 = U2 & Mask; U2 >>= n;
        Xint U1 = U2 & Mask; U2 >>= n;
        Xint W0 = SQr(U0, n);
        Xint W4 = SQr(U2, n);
        Xint P3 = SQr((((U2 << 1) + U1) << 1) + U0, n);
        U2 += U0;
        Xint P2 = SQr(U2 - U1, n);
        Xint P1 = SQr(U2 + U1, n);
        Xint W2 = (P1 + P2 >> 1) - (W0 + W4);
        Xint W3 = W0 - P1;
        W3 = ((W3 + P3 - P2 >> 1) + W3) / 3 - (W4 << 1);
        Xint W1 = P1 - (W4 + W3 + W2 + W0);
        return ((((W4 << n) + W3 << n) + W2 << n) + W1 << n) + W0;
    }
    private static Xint SQ4(Xint U3, int n)
    {
        n >>= 2;
        Xint Mask = (Xint.One << n) - 1;
        Xint U0 = U3 & Mask; U3 >>= n;
        Xint U1 = U3 & Mask; U3 >>= n;
        Xint U2 = U3 & Mask; U3 >>= n;
        Xint W0 = SQr(U0, n);                                   //  0
        U0 += U2;
        U1 += U3;
        Xint P1 = SQr(U0 + U1, n);                              //  1
        Xint P2 = SQr(U0 - U1, n);                              // -1
        U0 += 3 * U2;
        U1 += 3 * U3;
        Xint P3 = SQr(U0 + (U1 << 1), n);                       //  2
        Xint P4 = SQr(U0 - (U1 << 1), n);                       // -2
        Xint P5 = SQr(U0 + 12 * U2 + ((U1 + 12 * U3) << 2), n); //  4
        Xint W6 = SQr(U3, n);                                   //  inf
        Xint W1 = P1 + P2;
        Xint W4 = (((((P3 + P4) >> 1) - (W1 << 1)) / 3 + W0) >> 2) - 5 * W6;
        Xint W2 = (W1 >> 1) - (W6 + W4 + W0);
        P1 = P1 - P2;
        P4 = P4 - P3;
        Xint W5 = ((P1 >> 1) + (5 * P4 + P5 - W0 >> 4) - ((((W6 << 4) + W4) << 4) + W2)) / 45;
        W1 = ((P4 >> 2) + (P1 << 1)) / 3 + (W5 << 2);
        Xint W3 = (P1 >> 1) - (W1 + W5);
        return ((((((W6 << n) + W5 << n) + W4 << n) + W3 << n) + W2 << n) + W1 << n) + W0;
    }
    private static Xint SQ2P(Xint A, int n)
    {
        n >>= 1;
        Xint[] U = new Xint[3];
        U[0] = A & ((Xint.One << n) - 1); A >>= n; U[2] = A; U[1] = U[0] + A;
        Xint[] P = new Xint[3];
        Parallel.For(0, 3, (int i) => P[i] = SQr(U[i], n));
        return ((P[2] << n) + P[1] - (P[0] + P[2]) << n) + P[0];
    }

    public static int bL(Xint U)
    {
        byte[] bytes = (U.Sign * U).ToByteArray();
        int i = bytes.Length - 1;
        return (i << 3) + bitLengthMostSignificantByte(bytes[i]);
    }
    private static int bitLengthMostSignificantByte(byte b)
    {
        return b < 08 ? b < 02 ? b < 01 ? 0 : 1 :
                                 b < 04 ? 2 : 3 :
                        b < 32 ? b < 16 ? 4 : 5 :
                                 b < 64 ? 6 : 7;
    }

    private static int fL2(int i)
    {
        return
        i < 1 << 15 ? i < 1 << 07 ? i < 1 << 03 ? i < 1 << 01 ? i < 1 << 00 ? -1 : 00 :
                                                                i < 1 << 02 ? 01 : 02 :
                                                  i < 1 << 05 ? i < 1 << 04 ? 03 : 04 :
                                                                i < 1 << 06 ? 05 : 06 :
                                    i < 1 << 11 ? i < 1 << 09 ? i < 1 << 08 ? 07 : 08 :
                                                                i < 1 << 10 ? 09 : 10 :
                                                  i < 1 << 13 ? i < 1 << 12 ? 11 : 12 :
                                                                i < 1 << 14 ? 13 : 14 :
                      i < 1 << 23 ? i < 1 << 19 ? i < 1 << 17 ? i < 1 << 16 ? 15 : 16 :
                                                                i < 1 << 18 ? 17 : 18 :
                                                  i < 1 << 21 ? i < 1 << 20 ? 19 : 20 :
                                                                i < 1 << 22 ? 21 : 22 :
                                    i < 1 << 27 ? i < 1 << 25 ? i < 1 << 24 ? 23 : 24 :
                                                                i < 1 << 26 ? 25 : 26 :
                                                  i < 1 << 29 ? i < 1 << 28 ? 27 : 28 :
                                                                i < 1 << 30 ? 29 : 30;
    }
}

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