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/*! @file dGetDiagU.c
* \brief Extracts main diagonal of matrix
*
* <pre>
* -- Auxiliary routine in SuperLU (version 2.0) --
* Lawrence Berkeley National Lab, Univ. of California Berkeley.
* Xiaoye S. Li
* September 11, 2003
*
* Purpose
* =======
*
* GetDiagU extracts the main diagonal of matrix U of the LU factorization.
*
* Arguments
* =========
*
* L (input) SuperMatrix*
* The factor L from the factorization Pr*A*Pc=L*U as computed by
* dgstrf(). Use compressed row subscripts storage for supernodes,
* i.e., L has types: Stype = SLU_SC, Dtype = SLU_D, Mtype = SLU_TRLU.
*
* diagU (output) double*, dimension (n)
* The main diagonal of matrix U.
*
* Note
* ====
* The diagonal blocks of the L and U matrices are stored in the L
* data structures.
* </pre>
*/
#include "slu_ddefs.h"
void dGetDiagU(SuperMatrix *L, double *diagU)
{
int_t i, k, nsupers;
int_t fsupc, nsupr, nsupc, luptr;
double *dblock, *Lval;
SCformat *Lstore;
Lstore = L->Store;
Lval = Lstore->nzval;
nsupers = Lstore->nsuper + 1;
for (k = 0; k < nsupers; ++k) {
fsupc = L_FST_SUPC(k);
nsupc = L_FST_SUPC(k+1) - fsupc;
nsupr = L_SUB_START(fsupc+1) - L_SUB_START(fsupc);
luptr = L_NZ_START(fsupc);
dblock = &diagU[fsupc];
for (i = 0; i < nsupc; ++i) {
dblock[i] = Lval[luptr];
luptr += nsupr + 1;
}
}
}
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