/* nag_dgbtrs (f07bec) Example Program. * * Copyright 2001 Numerical Algorithms Group. * * Mark 7, 2001. */ #include #include #include #include #include int main(int argc, char *argv[]) { FILE *fpin, *fpout; char *outfile = 0; /* Scalars */ Integer i, ipiv_len, j, kl, ku, n, nrhs, pdab, pdb; Integer exit_status = 0; NagError fail; Nag_OrderType order; /* Arrays */ double *ab = 0, *b = 0; Integer *ipiv = 0; #ifdef NAG_COLUMN_MAJOR #define AB(I, J) ab[(J-1)*pdab + kl + ku + I - J] #define B(I, J) b[(J-1)*pdb + I - 1] order = Nag_ColMajor; #else #define AB(I, J) ab[(I-1)*pdab + kl + J - I] #define B(I, J) b[(I-1)*pdb + J - 1] order = Nag_RowMajor; #endif INIT_FAIL(fail); /* Check for command-line IO options */ fpin = nag_example_file_io(argc, argv, "-data", NULL); fpout = nag_example_file_io(argc, argv, "-results", NULL); (void) nag_example_file_io(argc, argv, "-nag_write", &outfile); fprintf(fpout, "nag_dgbtrs (f07bec) Example Program Results\n\n"); /* Skip heading in data file */ fscanf(fpin, "%*[^\n] "); fscanf(fpin, "%ld%ld%ld%ld%*[^\n] ", &n, &nrhs, &kl, &ku); ipiv_len = n; #ifdef NAG_COLUMN_MAJOR pdab = 2*kl + ku + 1; pdb = n; #else pdab = 2*kl + ku + 1; pdb = nrhs; #endif /* Allocate memory */ if (!(ab = NAG_ALLOC((2*kl+ku+1) * n, double)) || !(b = NAG_ALLOC(nrhs * n, double)) || !(ipiv = NAG_ALLOC(ipiv_len, Integer))) { fprintf(fpout, "Allocation failure\n"); exit_status = -1; goto END; } /* Read A from data file */ for (i = 1; i <= n; ++i) { for (j = MAX(i-kl, 1); j <= MIN(i+ku, n); ++j) fscanf(fpin, "%lf", &AB(i, j)); } fscanf(fpin, "%*[^\n] "); /* Read B from data file */ for (i = 1; i <= n; ++i) { for (j = 1; j <= nrhs; ++j) fscanf(fpin, "%lf", &B(i, j)); } fscanf(fpin, "%*[^\n] "); /* Factorize A */ /* nag_dgbtrf (f07bdc). * LU factorization of real m by n band matrix */ nag_dgbtrf(order, n, n, kl, ku, ab, pdab, ipiv, &fail); if (fail.code != NE_NOERROR) { fprintf(fpout, "Error from nag_dgbtrf (f07bdc).\n%s\n", fail.message); exit_status = 1; goto END; } /* Compute solution */ /* nag_dgbtrs (f07bec). * Solution of real band system of linear equations, * multiple right-hand sides, matrix already factorized by * nag_dgbtrf (f07bdc) */ nag_dgbtrs(order, Nag_NoTrans, n, kl, ku, nrhs, ab, pdab, ipiv, b, pdb, &fail); if (fail.code != NE_NOERROR) { fprintf(fpout, "Error from nag_dgbtrs (f07bec).\n%s\n", fail.message); exit_status = 1; goto END; } /* Print solution */ /* nag_gen_real_mat_print (x04cac). * Print real general matrix (easy-to-use) */ if (outfile) fclose(fpout); nag_gen_real_mat_print(order, Nag_GeneralMatrix, Nag_NonUnitDiag, n, nrhs, b, pdb, "Solution(s)", outfile, &fail); if (outfile && !(fpout = fopen(outfile, "a"))) { exit_status = 2; goto END; } if (fail.code != NE_NOERROR) { fprintf(fpout, "Error from nag_gen_real_mat_print (x04cac).\n%s\n", fail.message); exit_status = 1; goto END; } END: if (fpin != stdin) fclose(fpin); if (fpout != stdout) fclose(fpout); if (ab) NAG_FREE(ab); if (b) NAG_FREE(b); if (ipiv) NAG_FREE(ipiv); return exit_status; }