/* -----------------------------------------------------------------
 * Programmer: Radu Serban @ LLNL
 * -----------------------------------------------------------------
 * SUNDIALS Copyright Start
 * Copyright (c) 2002-2021, Lawrence Livermore National Security
 * and Southern Methodist University.
 * All rights reserved.
 *
 * See the top-level LICENSE and NOTICE files for details.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 * SUNDIALS Copyright End
 * -----------------------------------------------------------------
 * This header file contains definitions and declarations for use by
 * generic direct linear solvers for Ax = b. It defines types for
 * dense and banded matrices and corresponding accessor macros.
 * -----------------------------------------------------------------*/

#ifndef _SUNDIALS_DIRECT_H
#define _SUNDIALS_DIRECT_H

#include <stdio.h>
#include <sundials/sundials_types.h>

#ifdef __cplusplus  /* wrapper to enable C++ usage */
extern "C" {
#endif

/*
 * =================================================================
 *                C O N S T A N T S
 * =================================================================
 */

/*
 *  SUNDIALS_DENSE: dense matrix
 *  SUNDIALS_BAND:  banded matrix
 */

#define SUNDIALS_DENSE 1
#define SUNDIALS_BAND  2

/*
 * ==================================================================
 * Type definitions
 * ==================================================================
 */

/*
 * -----------------------------------------------------------------
 * Type : DlsMat
 * -----------------------------------------------------------------
 * The type DlsMat is defined to be a pointer to a structure
 * with various sizes, a data field, and an array of pointers to
 * the columns which defines a dense or band matrix for use in
 * direct linear solvers. The M and N fields indicates the number
 * of rows and columns, respectively. The data field is a one
 * dimensional array used for component storage. The cols field
 * stores the pointers in data for the beginning of each column.
 * -----------------------------------------------------------------
 * For DENSE matrices, the relevant fields in DlsMat are:
 *    type  = SUNDIALS_DENSE
 *    M     - number of rows
 *    N     - number of columns
 *    ldim  - leading dimension (ldim >= M)
 *    data  - pointer to a contiguous block of realtype variables
 *    ldata - length of the data array =ldim*N
 *    cols  - array of pointers. cols[j] points to the first element
 *            of the j-th column of the matrix in the array data.
 *
 * The elements of a dense matrix are stored columnwise (i.e. columns
 * are stored one on top of the other in memory).
 * If A is of type DlsMat, then the (i,j)th element of A (with
 * 0 <= i < M and 0 <= j < N) is given by (A->data)[j*n+i].
 *
 * The DENSE_COL and DENSE_ELEM macros below allow a user to access
 * efficiently individual matrix elements without writing out explicit
 * data structure references and without knowing too much about the
 * underlying element storage. The only storage assumption needed is
 * that elements are stored columnwise and that a pointer to the
 * jth column of elements can be obtained via the DENSE_COL macro.
 * -----------------------------------------------------------------
 * For BAND matrices, the relevant fields in DlsMat are:
 *    type  = SUNDIALS_BAND
 *    M     - number of rows
 *    N     - number of columns
 *    mu    - upper bandwidth, 0 <= mu <= min(M,N)
 *    ml    - lower bandwidth, 0 <= ml <= min(M,N)
 *    s_mu  - storage upper bandwidth, mu <= s_mu <= N-1.
 *            The dgbtrf routine writes the LU factors into the storage
 *            for A. The upper triangular factor U, however, may have
 *            an upper bandwidth as big as MIN(N-1,mu+ml) because of
 *            partial pivoting. The s_mu field holds the upper
 *            bandwidth allocated for A.
 *    ldim  - leading dimension (ldim >= s_mu)
 *    data  - pointer to a contiguous block of realtype variables
 *    ldata - length of the data array =ldim*(s_mu+ml+1)
 *    cols  - array of pointers. cols[j] points to the first element
 *            of the j-th column of the matrix in the array data.
 *
 * The BAND_COL, BAND_COL_ELEM, and BAND_ELEM macros below allow a
 * user to access individual matrix elements without writing out
 * explicit data structure references and without knowing too much
 * about the underlying element storage. The only storage assumption
 * needed is that elements are stored columnwise and that a pointer
 * into the jth column of elements can be obtained via the BAND_COL
 * macro. The BAND_COL_ELEM macro selects an element from a column
 * which has already been isolated via BAND_COL. The macro
 * BAND_COL_ELEM allows the user to avoid the translation
 * from the matrix location (i,j) to the index in the array returned
 * by BAND_COL at which the (i,j)th element is stored.
 * -----------------------------------------------------------------
 */

typedef struct _DlsMat {
  int type;
  sunindextype M;
  sunindextype N;
  sunindextype ldim;
  sunindextype mu;
  sunindextype ml;
  sunindextype s_mu;
  realtype *data;
  sunindextype ldata;
  realtype **cols;
} *DlsMat;

/*
 * ==================================================================
 * Data accessor macros
 * ==================================================================
 */

/*
 * -----------------------------------------------------------------
 * DENSE_COL and DENSE_ELEM
 * -----------------------------------------------------------------
 *
 * DENSE_COL(A,j) references the jth column of the M-by-N dense
 * matrix A, 0 <= j < N. The type of the expression DENSE_COL(A,j)
 * is (realtype *). After the assignment col_j = DENSE_COL(A,j),
 * col_j may be treated as an array indexed from 0 to M-1.
 * The (i,j)-th element of A is thus referenced by col_j[i].
 *
 * DENSE_ELEM(A,i,j) references the (i,j)th element of the dense
 * M-by-N matrix A, 0 <= i < M ; 0 <= j < N.
 *
 * -----------------------------------------------------------------
 */

#define DENSE_COL(A,j) ((A->cols)[j])
#define DENSE_ELEM(A,i,j) ((A->cols)[j][i])

/*
 * -----------------------------------------------------------------
 * BAND_COL, BAND_COL_ELEM, and BAND_ELEM
 * -----------------------------------------------------------------
 *
 * BAND_COL(A,j) references the diagonal element of the jth column
 * of the N by N band matrix A, 0 <= j <= N-1. The type of the
 * expression BAND_COL(A,j) is realtype *. The pointer returned by
 * the call BAND_COL(A,j) can be treated as an array which is
 * indexed from -(A->mu) to (A->ml).
 *
 * BAND_COL_ELEM references the (i,j)th entry of the band matrix A
 * when used in conjunction with BAND_COL. The index (i,j) should
 * satisfy j-(A->mu) <= i <= j+(A->ml).
 *
 * BAND_ELEM(A,i,j) references the (i,j)th element of the M-by-N
 * band matrix A, where 0 <= i,j <= N-1. The location (i,j) should
 * further satisfy j-(A->mu) <= i <= j+(A->ml).
 *
 * -----------------------------------------------------------------
 */

#define BAND_COL(A,j) (((A->cols)[j])+(A->s_mu))
#define BAND_COL_ELEM(col_j,i,j) (col_j[(i)-(j)])
#define BAND_ELEM(A,i,j) ((A->cols)[j][(i)-(j)+(A->s_mu)])

/*
 * ==================================================================
 * Exported function prototypes (functions working on dlsMat)
 * ==================================================================
 */

/*
 * -----------------------------------------------------------------
 * Function: NewDenseMat
 * -----------------------------------------------------------------
 * NewDenseMat allocates memory for an M-by-N dense matrix and
 * returns the storage allocated (type DlsMat). NewDenseMat
 * returns NULL if the request for matrix storage cannot be
 * satisfied. See the above documentation for the type DlsMat
 * for matrix storage details.
 * -----------------------------------------------------------------
 */

SUNDIALS_EXPORT DlsMat NewDenseMat(sunindextype M, sunindextype N);

/*
 * -----------------------------------------------------------------
 * Function: NewBandMat
 * -----------------------------------------------------------------
 * NewBandMat allocates memory for an M-by-N band matrix
 * with upper bandwidth mu, lower bandwidth ml, and storage upper
 * bandwidth smu. Pass smu as follows depending on whether A will
 * be LU factored:
 *
 * (1) Pass smu = mu if A will not be factored.
 *
 * (2) Pass smu = MIN(N-1,mu+ml) if A will be factored.
 *
 * NewBandMat returns the storage allocated (type DlsMat) or
 * NULL if the request for matrix storage cannot be satisfied.
 * See the documentation for the type DlsMat for matrix storage
 * details.
 * -----------------------------------------------------------------
 */

SUNDIALS_EXPORT DlsMat NewBandMat(sunindextype N, sunindextype mu,
                                  sunindextype ml, sunindextype smu);

/*
 * -----------------------------------------------------------------
 * Functions: DestroyMat
 * -----------------------------------------------------------------
 * DestroyMat frees the memory allocated by NewDenseMat or NewBandMat
 * -----------------------------------------------------------------
 */

SUNDIALS_EXPORT void DestroyMat(DlsMat A);

/*
 * -----------------------------------------------------------------
 * Function: NewIntArray
 * -----------------------------------------------------------------
 * NewIntArray allocates memory an array of N int's and returns
 * the pointer to the memory it allocates. If the request for
 * memory storage cannot be satisfied, it returns NULL.
 * -----------------------------------------------------------------
 */

SUNDIALS_EXPORT int *NewIntArray(int N);

/*
 * -----------------------------------------------------------------
 * Function: NewIndexArray
 * -----------------------------------------------------------------
 * NewIndexArray allocates memory an array of N sunindextype's and
 * returns the pointer to the memory it allocates. If the request
 * for memory storage cannot be satisfied, it returns NULL.
 * -----------------------------------------------------------------
 */

SUNDIALS_EXPORT sunindextype *NewIndexArray(sunindextype N);

/*
 * -----------------------------------------------------------------
 * Function: NewRealArray
 * -----------------------------------------------------------------
 * NewRealArray allocates memory an array of N realtype and returns
 * the pointer to the memory it allocates. If the request for
 * memory storage cannot be satisfied, it returns NULL.
 * -----------------------------------------------------------------
 */

SUNDIALS_EXPORT realtype *NewRealArray(sunindextype N);

/*
 * -----------------------------------------------------------------
 * Function: DestroyArray
 * -----------------------------------------------------------------
 * DestroyArray frees memory allocated by NewIntArray, NewIndexArray,
 * or NewRealArray.
 * -----------------------------------------------------------------
 */

SUNDIALS_EXPORT void DestroyArray(void *p);

/*
 * -----------------------------------------------------------------
 * Function : AddIdentity
 * -----------------------------------------------------------------
 * AddIdentity adds 1.0 to the main diagonal (A_ii, i=0,1,...,N-1) of
 * the M-by-N matrix A (M>= N) and stores the result back in A.
 * AddIdentity is typically used with square matrices.
 * AddIdentity does not check for M >= N and therefore a segmentation
 * fault will occur if M < N!
 * -----------------------------------------------------------------
 */

SUNDIALS_EXPORT void AddIdentity(DlsMat A);

/*
 * -----------------------------------------------------------------
 * Function : SetToZero
 * -----------------------------------------------------------------
 * SetToZero sets all the elements of the M-by-N matrix A to 0.0.
 * -----------------------------------------------------------------
 */

SUNDIALS_EXPORT void SetToZero(DlsMat A);

/*
 * -----------------------------------------------------------------
 * Functions: PrintMat
 * -----------------------------------------------------------------
 * This function prints the M-by-N (dense or band) matrix A to
 * outfile as it would normally appear on paper.
 * It is intended as debugging tools with small values of M and N.
 * The elements are printed using the %g/%lg/%Lg option.
 * A blank line is printed before and after the matrix.
 * -----------------------------------------------------------------
 */

SUNDIALS_EXPORT void PrintMat(DlsMat A, FILE *outfile);


/*
 * ==================================================================
 * Exported function prototypes (functions working on realtype**)
 * ==================================================================
 */

SUNDIALS_EXPORT realtype **newDenseMat(sunindextype m, sunindextype n);
SUNDIALS_EXPORT realtype **newBandMat(sunindextype n, sunindextype smu,
                                      sunindextype ml);
SUNDIALS_EXPORT void destroyMat(realtype **a);
SUNDIALS_EXPORT int *newIntArray(int n);
SUNDIALS_EXPORT sunindextype *newIndexArray(sunindextype n);
SUNDIALS_EXPORT realtype *newRealArray(sunindextype m);
SUNDIALS_EXPORT void destroyArray(void *v);


#ifdef __cplusplus
}
#endif

#endif
