multiply.txt

    Trachtenberg Multiplication using multi-tasking
    Each process does 1 pass

    char result[11];

    int N = 6; // number of digits
    int a[] = { 1, 2, 3, 4, 5, 6};
    int b[] = { 7, 8, 9, 0, 1, 2);

    process    start       end
    number     position    position
    -------    --------    --------
      ps1        6     to    6
      ps2        5     to    6
      ps3        4     to    6
      ps4        3     to    6
      ps5        2     to    6
      ps6        1     to    6
      ps7        1     to    5
      ps8        1     to    4
      ps9        1     to    3
      ps10       1     to    2
      ps11       1     to    1

    ps = 0           // 0
      ls = rs = N-1;
      for (i=1; i < N*2-1;i++
        {
          if (i < n*2-1)
            {
              send_to_ps(i,ls);
              send_to_ps(i,rs);
            }
          if (i==1)  send_to_ps(ps1, 0)
          if (ls > 0) ls--; else rs--;
        }
      for (i=1; i < N*2-1;i++
        {
          read(digit, psnumber)
          result[psnumber]= digit;
        }
      print result

    ps = 1..N*2-1    // 1 2 3 4 5 6 7 8 9 10 11
      read(psnumber, ls)
      read(psnumber, rs)
      carry = 0;
      for (k=ls, j=rs; k <= rs; k++,j--) carry += a[j]*b[k];
      read(psnumber, tcarry);
      carry += tcarry;

      rmd = carry%10;  // pick off right-most digit
      send to ps(0,rmd);
      carry /= 10;
      send to ps(ps+1,carry);

    ps = N*2       // 12
      read(psnumber,carry);
      rmd = carry%10;  
      send to ps(0,rmd);