Example 2: using persistency

Let us consider the following problem : , with A,B and C persistent matrices.

  double *A, *B, *C; 
  // matrices initialization
  ...
  diet_initialize();
  strcpy(path,"MatPROD");
  profile = diet_profile_alloc(path, 1, 1, 2);
  diet_matrix_set(diet_parameter(profile,0),
                  A, DIET_PERSISTENT, DIET_DOUBLE, mA, nA, oA);
  print_matrix(A, mA, nA, (oA == DIET_ROW_MAJOR));
  diet_matrix_set(diet_parameter(profile,1),
                  B, DIET_PERSISTENT, DIET_DOUBLE, mB, nB, oB);
  print_matrix(B, mB, nB, (oB == DIET_ROW_MAJOR));
  diet_matrix_set(diet_parameter(profile,2),
                  NULL, DIET_PERSISTENT_RETURN, DIET_DOUBLE, mA, nB, oC);
  
  if (!diet_call(profile)) {
    diet_matrix_get(diet_parameter(profile,2),&C, NULL, &mA, &nB, &oC);
    store_id(profile->parameters[2].desc.id,"matrix C of doubles");
    store_id(profile->parameters[1].desc.id,"matrix B of doubles");
    store_id(profile->parameters[0].desc.id,"matrix A of doubles");
    print_matrix(C, mA, nB, (oC == DIET_ROW_MAJOR));
      
  }
  diet_profile_free(profile);
  // free matrices memory
  ...
  diet_finalize();

Then, a client submits the problem : with C already present in the platform. We consider that the handle of C is “id.MA1.1.3”.

  double *C, *D, *E; 
  // matrices initialization
  ...
  diet_initialize();

  strcpy(path,"MatSUM");
  profile2 = diet_profile_alloc(path, 1, 1, 2);
  
  printf("second pb\n\n");
  diet_use_data(diet_parameter(profile2,0), "id.MA1.1.3");
  diet_matrix_set(diet_parameter(profile2,1),
                  E, DIET_PERSISTENT, DIET_DOUBLE, mA, nB, oE);
  print_matrix(E, mA, nB, (oE == DIET_ROW_MAJOR));
  diet_matrix_set(diet_parameter(profile2,2),
                  NULL, DIET_PERSISTENT_RETURN, DIET_DOUBLE, mA, nB, oD);
  
  if (!diet_call(profile2)) {
   diet_matrix_get(diet_parameter(profile2,2), &D, NULL, &mA, &nB, &oD);
   print_matrix(D, mA, nB, (oD == DIET_ROW_MAJOR));
   store_id(profile2->parameters[2].desc.id,"matrix D of doubles");
   store_id(profile2->parameters[1].desc.id,"matrix E of doubles");
  
  }
  diet_profile_free(profile2);
  diet_free_persistent_data("id.MA1.1.3");
  // free matrices memory
  ...
  diet_finalize();

Note that when a single client creates persistent data with a first DIET call and uses that data with a second DIET call, we will not know in advance the identifier of the data. However, the identifier is stored in the structure of the first profile. For example, consider a matrix A built with diet_matrix_set() method as follows:

  ...
  diet_profile_t *profile;
  ...
  diet_matrix_set(diet_parameter(profile,0),
                  E, DIET_PERSISTENT, DIET_DOUBLE, mA, nA, oA);
  ...

After the first diet_call, the identifier of A is stored in the profile
(in profile->parameters[0].desc.id). So, for the second call we will have the following instruction in order to use A:

  ...
  diet_profile_t *profile2;
  ...
  diet_use_data(diet_parameter(profile2,0),profile->parameters[0].desc.id);
  ...

NB:

when using this method, the first profile (here profile) must not be freed before using or making a copy of the data identifier.