src/hamiltonian_expectation_value/sparse_matrix_setup.c

   1
   2                    //  PHYS 405                                                 //
   3
   4                    //  code to generate a sparse Hamiltonian matrix             //
   5                    //  H matrix filled with random numbers at random locations  //
   6
   7                    //  assignment 2 - part b               //
   8
   9                                          // Michel Vallieres, Fall 2007 //
  10
  11 #include <stdio.h>
  12 #include <math.h>
  13 #include <stdlib.h>
  14
  15                                            /* matrix size */
  16 #define N 1000000
  17                                            /* # non-zero elements */
  18 #define Nelements   1012717
  19
  20
  21 int main( int argc, char * argv[] )
  22 {
  23   double Hij;
  24   int    i, j, k, element;
  25   int    scan, repeat, kepti[Nelements], keptj[Nelements];
  26   FILE   *fp;
  27                                           /* data file size */
  28   fp = fopen( "sparse_Hamiltonian_size", "w" );
  29   fprintf( fp, "%d %d\n", N, Nelements);
  30   fclose( fp );
  31                                           /* data file */
  32   fp = fopen( "sparse_Hamiltonian", "w" );
  33                                           /* initialize random numbers */
  34   srand( 1.0 );
  35                                           /* loop over non-zero Hij */
  36   element =0;
  37   while ( element<Nelements )
  38     {
  39                                           /* random location */
  40       i = N * (float)rand() / (float)RAND_MAX;
  41       j = N * (float)rand() / (float)RAND_MAX;
  42
  43                                          /* symmetric matrix */
  44       if ( j > i )
  45         {
  46           k = i;
  47           i = j;
  48           j = k;
  49         }
  50
  51                                         /* avoid repetition */
  52       repeat = 0;
  53       if ( element > 0 )
  54         {
  55           scan = 0;
  56           while ( scan < element )
  57             {
  58               if ( i == kepti[scan] && j == keptj[scan] )
  59                 {
  60                   repeat = 1;
  61                 }
  62               scan++;
  63               if ( repeat == 1 )
  64                 break;
  65             }
  66         }
  67
  68       if ( repeat == 0 )
  69         {
  70                                          /* random value */
  71            Hij = (float)rand() / (float)RAND_MAX;
  72
  73                                          /* store element */
  74            kepti[element] = i;
  75            keptj[element] = j;
  76            fprintf( fp, "%d %d %f\n", i, j, Hij );
  77            element++;
  78         }
  79     }
  80
  81   fclose( fp );
  82
  83 }
  84
  85