mersennetwisterfast.java

java 写的一个新闻发布系统

                b ^= (b >>> 18);                        // TEMPERING_SHIFT_L(b)
                
                /* derived from nextDouble documentation in jdk 1.2 docs, see top */
                v1 = 2 *
                    (((((long)(y >>> 6)) << 27) + (z >>> 5)) / (double)(1L << 53))
                    - 1;
                v2 = 2 * (((((long)(a >>> 6)) << 27) + (b >>> 5)) / (double)(1L << 53))
                    - 1;
                s = v1 * v1 + v2 * v2;
                } while (s >= 1);
            double multiplier = Math.sqrt(-2 * Math.log(s)/s);
            nextNextGaussian = v2 * multiplier;
            haveNextNextGaussian = true;
            return v1 * multiplier;
            }
        }
    
    
    

    








    public final float nextFloat()
        {
        int y;
        
        if (mti >= N)   // generate N words at one time
            {
            int kk;
            
            for (kk = 0; kk < N - M; kk++)
                {
                y = (mt[kk] & UPPER_MASK) | (mt[kk+1] & LOWER_MASK);
                mt[kk] = mt[kk+M] ^ (y >>> 1) ^ mag01[y & 0x1];
                }
            for (; kk < N-1; kk++)
                {
                y = (mt[kk] & UPPER_MASK) | (mt[kk+1] & LOWER_MASK);
                mt[kk] = mt[kk+(M-N)] ^ (y >>> 1) ^ mag01[y & 0x1];
                }
            y = (mt[N-1] & UPPER_MASK) | (mt[0] & LOWER_MASK);
            mt[N-1] = mt[M-1] ^ (y >>> 1) ^ mag01[y & 0x1];

            mti = 0;

            }
  
        y = mt[mti++];
        y ^= y >>> 11;                          // TEMPERING_SHIFT_U(y)
        y ^= (y << 7) & TEMPERING_MASK_B;       // TEMPERING_SHIFT_S(y)
        y ^= (y << 15) & TEMPERING_MASK_C;      // TEMPERING_SHIFT_T(y)
        y ^= (y >>> 18);                        // TEMPERING_SHIFT_L(y)

        return (y >>> 8) / ((float)(1 << 24));
        }



    /** Returns an integer drawn uniformly from 0 to n-1.  Suffice it to say,
        n must be > 0, or an IllegalArgumentException is raised. */
    public int nextInt(int n)
        {
        if (n<=0)
            throw new IllegalArgumentException("n must be positive");
        
        if ((n & -n) == n)  // i.e., n is a power of 2
            {
            int y;
        
            if (mti >= N)   // generate N words at one time
                {
                int kk;
                
                for (kk = 0; kk < N - M; kk++)
                    {
                    y = (mt[kk] & UPPER_MASK) | (mt[kk+1] & LOWER_MASK);
                    mt[kk] = mt[kk+M] ^ (y >>> 1) ^ mag01[y & 0x1];
                    }
                for (; kk < N-1; kk++)
                    {
                    y = (mt[kk] & UPPER_MASK) | (mt[kk+1] & LOWER_MASK);
                    mt[kk] = mt[kk+(M-N)] ^ (y >>> 1) ^ mag01[y & 0x1];
                    }
                y = (mt[N-1] & UPPER_MASK) | (mt[0] & LOWER_MASK);
                mt[N-1] = mt[M-1] ^ (y >>> 1) ^ mag01[y & 0x1];
                
                mti = 0;
                }
            
            y = mt[mti++];
            y ^= y >>> 11;                          // TEMPERING_SHIFT_U(y)
            y ^= (y << 7) & TEMPERING_MASK_B;       // TEMPERING_SHIFT_S(y)
            y ^= (y << 15) & TEMPERING_MASK_C;      // TEMPERING_SHIFT_T(y)
            y ^= (y >>> 18);                        // TEMPERING_SHIFT_L(y)
            
            return (int)((n * (long) (y >>> 1) ) >> 31);
            }
        
        int bits, val;
        do 
            {
            int y;
            
            if (mti >= N)   // generate N words at one time
                {
                int kk;
                
                for (kk = 0; kk < N - M; kk++)
                    {
                    y = (mt[kk] & UPPER_MASK) | (mt[kk+1] & LOWER_MASK);
                    mt[kk] = mt[kk+M] ^ (y >>> 1) ^ mag01[y & 0x1];
                    }
                for (; kk < N-1; kk++)
                    {
                    y = (mt[kk] & UPPER_MASK) | (mt[kk+1] & LOWER_MASK);
                    mt[kk] = mt[kk+(M-N)] ^ (y >>> 1) ^ mag01[y & 0x1];
                    }
                y = (mt[N-1] & UPPER_MASK) | (mt[0] & LOWER_MASK);
                mt[N-1] = mt[M-1] ^ (y >>> 1) ^ mag01[y & 0x1];
                
                mti = 0;
                }
            
            y = mt[mti++];
            y ^= y >>> 11;                          // TEMPERING_SHIFT_U(y)
            y ^= (y << 7) & TEMPERING_MASK_B;       // TEMPERING_SHIFT_S(y)
            y ^= (y << 15) & TEMPERING_MASK_C;      // TEMPERING_SHIFT_T(y)
            y ^= (y >>> 18);                        // TEMPERING_SHIFT_L(y)
        
            bits = (y >>> 1);
            val = bits % n;
            } while(bits - val + (n-1) < 0);
        return val;
        }
    








    /**
     * Tests the code.
     */
    public static void main(String args[])
        { 
        int j;

        MersenneTwisterFast r;

        // UNCOMMENT THIS TO TEST FOR PROPER GAUSSIAN STATE INITIALIZATION
        
        /*
        System.out.println("If the gaussian state is properly initialized when setSeed() is called,\nthen #1 != #2, but #1 == #3\nIt's known that java 1.0.2 doesn't do gaussian initialization right,\nso setSeed() may result in one last gaussian drawn from the *previous* seed.");
        r = new MersenneTwisterFast(1);
        r.nextGaussian();  // loads the later gaussian into the state
        System.out.println("1:  " + r.nextGaussian());
        r = new MersenneTwisterFast(1);
        r.nextGaussian(); // loads the later gaussian into the state
        r.setSeed(1);     // should reset the gaussian state
        System.out.println("2:  " + r.nextGaussian());
        System.out.println("3:  " + r.nextGaussian());
        */

        
        // UNCOMMENT THIS TO TEST FOR CORRECTNESS
        // COMPARE WITH http://www.math.keio.ac.jp/~nisimura/random/int/mt19937int.out
        
        /*
        r = new MersenneTwisterFast(4357);
        System.out.println("Output of MersenneTwisterFast.java");
        for (j=0;j<1000;j++)
            {
            // first, convert the int from signed to "unsigned"
            long l = (long)r.nextInt();

            if (l < 0 ) l += 4294967296L;  // max int value
            String s = String.valueOf(l);

            while(s.length() < 10) s = " " + s;  // buffer
            System.out.print(s + " ");
            if (j%8==7) System.out.println();       
            }
        */


        // UNCOMMENT THIS TO TEST FOR SPEED

        /*
        r = new MersenneTwisterFast();
        System.out.println("\nTime to test grabbing 10000000 ints");
        long ms = System.currentTimeMillis();
        int xx=0;
        for (j = 0; j < 10000000; j++)
            xx += r.nextInt();
        System.out.println("Mersenne Twister: " + (System.currentTimeMillis()-ms + "          Ignore this: " + xx));

        Random rr = new Random(1);
        xx = 0;
        ms = System.currentTimeMillis();
        for (j = 0; j < 10000000; j++)
            xx += rr.nextInt();
        System.out.println("java.util.Random: " + (System.currentTimeMillis()-ms + "          Ignore this: " + xx));
        */

        
        // UNCOMMENT THIS TO DO TEST DIFFERENT TYPE OUTPUTS
        // THIS CAN BE USED TO COMPARE THE DIFFERENCE BETWEEN

        // MersenneTwisterFast.java AND MersenneTwister.java

        /*
        System.out.println("\nGrab the first 1000 booleans");
        r = new MersenneTwisterFast();
        for (j = 0; j < 1000; j++)
            {
            System.out.print(r.nextBoolean() + " ");
            if (j%8==7) System.out.println();
            }
        if (!(j%8==7)) System.out.println();

        byte[] bytes = new byte[1000];
        System.out.println("\nGrab the first 1000 bytes using nextBytes");
        r = new MersenneTwisterFast();
        r.nextBytes(bytes);
        for (j = 0; j < 1000; j++)
            {
            System.out.print(bytes[j] + " ");
            if (j%16==15) System.out.println();
            }
        if (!(j%16==15)) System.out.println();
        
        byte b;
        System.out.println("\nGrab the first 1000 bytes -- must be same as nextBytes");
        r = new MersenneTwisterFast();

        for (j = 0; j < 1000; j++)
            {
            System.out.print((b = r.nextByte()) + " ");
            if (b!=bytes[j]) System.out.print("BAD ");
            if (j%16==15) System.out.println();
            }
        if (!(j%16==15)) System.out.println();

        System.out.println("\nGrab the first 1000 shorts");
        r = new MersenneTwisterFast();
        for (j = 0; j < 1000; j++)
            {
            System.out.print(r.nextShort() + " ");
            if (j%8==7) System.out.println();
            }
        if (!(j%8==7)) System.out.println();

        System.out.println("\nGrab the first 1000 ints");
        r = new MersenneTwisterFast();
        for (j = 0; j < 1000; j++)
            {
            System.out.print(r.nextInt() + " ");
            if (j%4==3) System.out.println();
            }
        if (!(j%4==3)) System.out.println();

        System.out.println("\nGrab the first 1000 ints of different sizes");
        r = new MersenneTwisterFast();
        for (j = 0; j < 1000; j++)
            {
            System.out.print(r.nextInt(j+1) + " ");
            if (j%4==3) System.out.println();
            }
        if (!(j%4==3)) System.out.println();

        System.out.println("\nGrab the first 1000 longs");
        r = new MersenneTwisterFast();
        for (j = 0; j < 1000; j++)
            {
            System.out.print(r.nextLong() + " ");
            if (j%3==2) System.out.println();
            }
        if (!(j%3==2)) System.out.println();

        System.out.println("\nGrab the first 1000 floats");
        r = new MersenneTwisterFast();
        for (j = 0; j < 1000; j++)
            {
            System.out.print(r.nextFloat() + " ");
            if (j%4==3) System.out.println();
            }
        if (!(j%4==3)) System.out.println();

        System.out.println("\nGrab the first 1000 doubles");
        r = new MersenneTwisterFast();
        for (j = 0; j < 1000; j++)
            {
            System.out.print(r.nextDouble() + " ");
            if (j%3==2) System.out.println();
            }
        if (!(j%3==2)) System.out.println();

        System.out.println("\nGrab the first 1000 gaussian doubles");
        r = new MersenneTwisterFast();
        for (j = 0; j < 1000; j++)
            {
            System.out.print(r.nextGaussian() + " ");
            if (j%3==2) System.out.println();
            }
        if (!(j%3==2)) System.out.println();
        */
        }

    }