KmlScaissCgSolve?I

Solve a system of linear equations.

Interface Definition

C interface:

int KmlScaissCgSolveSI(KmlScasolverTask **handle, int nb, float *x, int ldx, const float *b, int ldb);

int KmlScaissCgSolveDI(KmlScasolverTask **handle, int nb, double *x, int ldx, const double *b, int ldb);

Parameters

Parameter	Type	Description	Input/Output
handle	KmlScasolverTask **	Solver handle, which transfers a variable defined previously.	Input/Output
nb	int	Number of RHS vectors. The value of nb can only be 1.	Input
x	float * in KmlScaissCgSolveSI double * in KmlScaissCgSolveDI	Array that reads and stores the global solution result, with n elements.	Input/Output
ldx	int	Size of the leading dimension of x. This is a reserved parameter.	Input
b	const float * in KmlScaissCgSolveSI const double * in KmlScaissCgSolveDI	Array that reads the local RHS terms corresponding to a process, with stripeWidth[0] elements	Input
ldb	int	Size of the leading dimension of b. This is a reserved parameter.	Input

Return Value

Return Value	Type	Description
KMLSS_NO_ERROR	int	The execution is successful.
KMLSS_BAD_NB	int	The value of nb is not 1.
KML_NO_MEMORY	int	The memory is insufficient.
KMLSS_NULL_ARGUMENT	int	A null argument exists in {handle, x, b}.

Dependency

#include "kml_scaiss.h"

Example

C interface:

MPI_Init(NULL, NULL);
int size, rank;
MPI_Comm_size(MPI_COMM_WORLD, &size);// Obtain the total number of processes.
MPI_Comm_rank(MPI_COMM_WORLD, &rank);// Obtain the current process ID.

int n = 8 / size;
int n_beg = n * rank;
if (n * size != 8 && rank == (size - 1)) {
    n = 8 - n * rank;
}
int ja[26] = { 0, 3, 4, 1, 2, 3, 5, 1, 2, 7, 0, 1, 3, 6, 0, 4, 5, 1, 4, 5, 7, 3, 6, 2, 5, 7 };
double a[26] = { 1.0, 1.0, 2.0, 9.0, 2.0, 1.0, -3.0, 2.0, 3.0, 2.0, 1.0, 1.0, 9.0, -5.0, 2.0, 6.0, 1.0, -3.0, 1.0, 4.0, 1.0, -5.0, 7.0, 2.0, 1.0, 2.0 };
int ia[9] = { 0, 3, 7, 10, 14, 17, 21, 23, 26 };
double b[8] = { 4.0, 9.0, 7.0, 6.0, 9.0, 3.0, 2.0, 5.0 };
double x[8] = { 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 };
int a_beg = ia[n_beg];
for (int i = n_beg; i < 9; i++) {
    ia[i] -= a_beg;
}

/* Internal KML_SCAISS structure */
KmlScasolverTask *handle;

/* KML_SCAISS control parameters */
int nrhs = 1;         /* Number of right-hand sides */
int ldx = 8, ldb = 8; /*!Leading dimension of B and X */
int error;            /* Output error handle */

/* Create data structures */
const double *a_holder = &a[a_beg];
const int *ja_holder = &ja[a_beg];
const int *ia_holder = &ia[n_beg];
error = KmlScaissCgInitStripesDI(&handle, 8, 1, &n, &n_beg, &a_holder, &ja_holder, &ia_holder, MPI_COMM_WORLD);

double eps = 1e-4;
error = KmlScaissCgSetDID(&handle, KMLSS_THRESHOLD, &eps, 1); 
int max_iters = 2000;
error = KmlScaissCgSetDII(&handle, KMLSS_MAX_ITERATION_COUNT, &max_iters, 1);

error = KmlScaissCgSolveDI(&handle, nrhs, &x[0], ldx, &b[n_beg], ldb);

if (error != 0) {
    printf("\nERROR in KmlScaissCgSolveDI: %d", error);
    return 1;
    }

Parent topic: SCAISS-CG