/*
 * -----------------------------------------------------------------
 * Programmer(s): Daniel Reynolds @ SMU
 * Based on codes <solver>_lapack.c by: Radu Serban @ LLNL
 * -----------------------------------------------------------------
 * LLNS/SMU Copyright Start
 * Copyright (c) 2017, Southern Methodist University and 
 * Lawrence Livermore National Security
 *
 * This work was performed under the auspices of the U.S. Department 
 * of Energy by Southern Methodist University and Lawrence Livermore 
 * National Laboratory under Contract DE-AC52-07NA27344.
 * Produced at Southern Methodist University and the Lawrence 
 * Livermore National Laboratory.
 *
 * All rights reserved.
 * For details, see the LICENSE file.
 * LLNS/SMU Copyright End
 * -----------------------------------------------------------------
 * This is the implementation file for the LAPACK band 
 * implementation of the SUNLINSOL package.
 * -----------------------------------------------------------------
 */ 

#include <stdio.h>
#include <stdlib.h>

#include <sunlinsol/sunlinsol_lapackband.h>
#include <sundials/sundials_math.h>

#define ZERO  RCONST(0.0)
#define ONE   RCONST(1.0)

/* Private function prototypes */
sunindextype GlobalVectorLength_LapBand(N_Vector y);

/*
 * -----------------------------------------------------------------
 * Band solver structure accessibility macros: 
 * -----------------------------------------------------------------
 */

#define LAPACKBAND_CONTENT(S) ( (SUNLinearSolverContent_LapackBand)(S->content) )
#define PIVOTS(S)             ( LAPACKBAND_CONTENT(S)->pivots )
#define LASTFLAG(S)           ( LAPACKBAND_CONTENT(S)->last_flag )

/*
 * -----------------------------------------------------------------
 * exported functions
 * -----------------------------------------------------------------
 */

/* ----------------------------------------------------------------------------
 * Function to create a new LAPACK band linear solver
 */

SUNLinearSolver SUNLapackBand(N_Vector y, SUNMatrix A)
{
  SUNLinearSolver S;
  SUNLinearSolver_Ops ops;
  SUNLinearSolverContent_LapackBand content;
  sunindextype MatrixRows, VecLength;
  
  /* Check compatibility with supplied SUNMatrix and N_Vector */
  if (SUNMatGetID(A) != SUNMATRIX_BAND)
    return(NULL);
  if (SUNBandMatrix_Rows(A) != SUNBandMatrix_Columns(A))
    return(NULL);
  MatrixRows = SUNBandMatrix_Rows(A);
  if ( (N_VGetVectorID(y) != SUNDIALS_NVEC_SERIAL) &&
       (N_VGetVectorID(y) != SUNDIALS_NVEC_OPENMP) &&
       (N_VGetVectorID(y) != SUNDIALS_NVEC_PTHREADS) )
    return(NULL);

  /* optimally this function would be replaced with a generic N_Vector routine */
  VecLength = GlobalVectorLength_LapBand(y);
  if (MatrixRows != VecLength)
    return(NULL);
  
  /* Create linear solver */
  S = NULL;
  S = (SUNLinearSolver) malloc(sizeof *S);
  if (S == NULL) return(NULL);
  
  /* Create linear solver operation structure */
  ops = NULL;
  ops = (SUNLinearSolver_Ops) malloc(sizeof(struct _generic_SUNLinearSolver_Ops));
  if (ops == NULL) { free(S); return(NULL); }

  /* Attach operations */
  ops->gettype           = SUNLinSolGetType_LapackBand;
  ops->initialize        = SUNLinSolInitialize_LapackBand;
  ops->setup             = SUNLinSolSetup_LapackBand;
  ops->solve             = SUNLinSolSolve_LapackBand;
  ops->lastflag          = SUNLinSolLastFlag_LapackBand;
  ops->space             = SUNLinSolSpace_LapackBand;
  ops->free              = SUNLinSolFree_LapackBand;
  ops->setatimes         = NULL;
  ops->setpreconditioner = NULL;
  ops->setscalingvectors = NULL;
  ops->numiters          = NULL;
  ops->resnorm           = NULL;
  ops->resid             = NULL;

  /* Create content */
  content = NULL;
  content = (SUNLinearSolverContent_LapackBand) malloc(sizeof(struct _SUNLinearSolverContent_LapackBand));
  if (content == NULL) { free(ops); free(S); return(NULL); }

  /* Fill content */
  content->N = MatrixRows;
  content->last_flag = 0;
  content->pivots = NULL;
  content->pivots = (sunindextype *) malloc(MatrixRows * sizeof(sunindextype));
  if (content->pivots == NULL) {
    free(content); free(ops); free(S); return(NULL);
  }
  
  /* Attach content and ops */
  S->content = content;
  S->ops     = ops;

  return(S);
}


/*
 * -----------------------------------------------------------------
 * implementation of linear solver operations
 * -----------------------------------------------------------------
 */

SUNLinearSolver_Type SUNLinSolGetType_LapackBand(SUNLinearSolver S)
{
  return(SUNLINEARSOLVER_DIRECT);
}


int SUNLinSolInitialize_LapackBand(SUNLinearSolver S)
{
  /* all solver-specific memory has already been allocated */
  LASTFLAG(S) = SUNLS_SUCCESS;
  return(LASTFLAG(S));
}


int SUNLinSolSetup_LapackBand(SUNLinearSolver S, SUNMatrix A)
{
  int n, ml, mu, ldim, ier;

  /* check for valid inputs */
  if ( (A == NULL) || (S == NULL) ) 
    return(SUNLS_MEM_NULL);
  
  /* Ensure that A is a band matrix */
  if (SUNMatGetID(A) != SUNMATRIX_BAND) {
    LASTFLAG(S) = SUNLS_ILL_INPUT;
    return(LASTFLAG(S));
  }
  
  /* Call LAPACK to do LU factorization of A */
  n = SUNBandMatrix_Rows(A);
  ml = SUNBandMatrix_LowerBandwidth(A);
  mu = SUNBandMatrix_UpperBandwidth(A);
  ldim = SUNBandMatrix_LDim(A);
  xgbtrf_f77(&n, &n, &ml, &mu, SUNBandMatrix_Data(A), 
	     &ldim, PIVOTS(S), &ier);
  
  LASTFLAG(S) = (long int) ier;
  if (ier > 0) 
    return(SUNLS_LUFACT_FAIL);
  if (ier < 0) 
    return(SUNLS_PACKAGE_FAIL_UNREC);
  return(SUNLS_SUCCESS);
}


int SUNLinSolSolve_LapackBand(SUNLinearSolver S, SUNMatrix A, N_Vector x, 
                              N_Vector b, realtype tol)
{
  int n, ml, mu, ldim, one, ier;
  realtype *xdata;
  
  /* check for valid inputs */
  if ( (A == NULL) || (S == NULL) || (x == NULL) || (b == NULL) ) 
    return(SUNLS_MEM_NULL);
  
  /* copy b into x */
  N_VScale(ONE, b, x);

  /* access x data array */
  xdata = N_VGetArrayPointer(x);
  if (xdata == NULL) {
    LASTFLAG(S) = 1;
    return(LASTFLAG(S));
  }
  
  /* Call LAPACK to solve the linear system */
  n = SUNBandMatrix_Rows(A);
  ml = SUNBandMatrix_LowerBandwidth(A);
  mu = SUNBandMatrix_UpperBandwidth(A);
  ldim = SUNBandMatrix_LDim(A);
  one = 1;
  xgbtrs_f77("N", &n, &ml, &mu, &one, SUNBandMatrix_Data(A), 
	     &ldim, PIVOTS(S), xdata, &n, &ier, 1);
  LASTFLAG(S) = (long int) ier;
  if (ier < 0) 
    return(SUNLS_PACKAGE_FAIL_UNREC);

  LASTFLAG(S) = SUNLS_SUCCESS;
  return(LASTFLAG(S));
}


long int SUNLinSolLastFlag_LapackBand(SUNLinearSolver S)
{
  /* return the stored 'last_flag' value */
  return(LASTFLAG(S));
}


int SUNLinSolSpace_LapackBand(SUNLinearSolver S, 
                              long int *lenrwLS, 
                              long int *leniwLS)
{
  *lenrwLS = 0;
  *leniwLS = 2 + LAPACKBAND_CONTENT(S)->N;
  return(SUNLS_SUCCESS);
}

int SUNLinSolFree_LapackBand(SUNLinearSolver S)
{
  /* return with success if already freed */
  if (S == NULL)
    return(SUNLS_SUCCESS);
  
  /* delete items from contents, then delete generic structure */
  if (S->content) {
    if (PIVOTS(S)) {
      free(PIVOTS(S));
      PIVOTS(S) = NULL;
    }
    free(S->content);  
    S->content = NULL;
  }
 
  if (S->ops) {
    free(S->ops);  
    S->ops = NULL;
  }
  free(S); S = NULL;
  return(SUNLS_SUCCESS);
}

/*
 * -----------------------------------------------------------------
 * private functions
 * -----------------------------------------------------------------
 */

/* Inefficient kludge for determining the number of entries in a N_Vector 
   object (replace if such a routine is ever added to the N_Vector API).

   Returns "-1" on an error. */
sunindextype GlobalVectorLength_LapBand(N_Vector y)
{
  realtype len;
  N_Vector tmp = NULL;
  tmp = N_VClone(y);
  if (tmp == NULL)  return(-1);
  N_VConst(ONE, tmp);
  len = N_VDotProd(tmp, tmp);
  N_VDestroy(tmp);
  return( (sunindextype) len );
}
