Migration Procedure

Migrating the Library That Uses the C Language

Both PETSc and KML_SOLVER provide C interfaces. However, the interface names and receiving parameters are inconsistent. Therefore, the corresponding function needs to be switched. The following is an example:

1. Initialization
   Before the migration:

   KSP            ksp;
   PetscErrorCode ierr;
   ierr = KSPCreate(PETSC_COMM_WORLD,&ksp);
   ierr = KSPSetOperators(ksp,A,A);

   After the migration:

   int n = 8;    
   int ia[9];    
   int ja[17];
   double a[17];
   void* handle;
   int error = KmlIssCgInitDI(&handle, &n, a, ja, ia);

2. Finding the solution
   Before the migration:

   Vec            u,x,b;
   ierr = VecCreate(PETSC_COMM_WORLD,&u);
   ierr = VecSetSizes(u,PETSC_DECIDE,rdim);
   ierr = VecSetFromOptions(u);CHKERRQ(ierr);
   ierr = VecDuplicate(u,&b);CHKERRQ(ierr);
   ierr = VecDuplicate(b,&x);CHKERRQ(ierr);
   
   ierr = KSPSolve(ksp,b,x);CHKERRQ(ierr);

   After the migration:

   double b[8];    
   /* Solution vector */    
   double x[8];
   int nrhs = 1; /* Number of right-hand sides */       
   int ldx=n, ldb=n; /*!Leading dimension of B and X */
   int error = KmlIssCgSolveDI(&handle, &nrhs, x, &ldx, b, &ldb);

3. Obtaining iteration parameters
   Before the migration:

   PetscInt       its;
   ierr = KSPGetIterationNumber(ksp,&its);CHKERRQ(ierr);

   After the migration:

   int *data;  // user data.
   int nd = 1;
   int error = KmlIssCgGetDII(&handle, ITERATION_COUNT, data, nd);

4. Clearing
   Before the migration:

   ierr = KSPDestroy(&ksp);

   After the migration:

   int error = KmlIssCgCleanDI(&handle);

5. Header file

   Before the migration:

   #include "petscksp.h"

   After the migration:

   #include "kml_iss.h"

6. Compiling the links

   Replace the link options related to PETSc. For details, see "Installing KML > Verifying the Installation" in Kunpeng Math Library Developer Guide.