#include "BSprivate.h"

/*@ BSback_solve1 - Backward triangular matrix solution on a 
                   single vector

    Input Parameters:
.   A - The sparse matrix
.   x - The rhs
.   comm - The communication structure for A
.   procinfo - the usual processor information

    Output Parameters:
.   x - on exit contains the solution vector

    Returns:
    void

	Notes:
    We assume that A has no i-nodes or cliques

 @*/
void BSback_solve1(BSpar_mat *A, FLOAT *x, BScomm *comm, BSprocinfo *procinfo)
{
	BMcomp_msg *from_msg, *to_msg;
	BMphase *to_phase, *from_phase;
	BMmsg *msg;
	int	i, j, k;
	int	cl_ind, in_ind;
	int	count, size, ind;
	int *row;
	FLOAT *nz;
	BScl_2_inode *clique2inode = A->clique2inode;
	BSnumbering *color2clique = A->color2clique;
	BSinode *inodes = A->inodes->list;
	int	*in_index = clique2inode->inode_index;
	int	*proc = clique2inode->proc;
	BSdense	*d_mats = clique2inode->d_mats;
	int	*data_ptr, msg_len;
	FLOAT *msg_buf;
	int	my_id = procinfo->my_id;
	int	*col2cl = color2clique->numbers;
	int	length = color2clique->length;
	int	start, finish, symmetric;
	FLOAT	t;
	int *gnum = A->global_row_num->numbers;
	int *iperm = A->inv_perm->perm;

	/* Is the symmetric data structure used? */
	symmetric = A->icc_storage;

	/*
	if(!symmetric) {
		BSILUback_solve1(A,x,comm,procinfo);
		return;
	}
	*/

	if(symmetric) {
		from_msg = comm->to_msg; /* we do mean to switch these */
		to_msg = comm->from_msg;
	} else {
		from_msg = comm->from_msg; /* do not switch for ILU case */
		to_msg = comm->to_msg;
	}

	/* post for all messages */
	BMinit_comp_msg(from_msg,procinfo); CHKERR(0);

	/* now do this phase by phase */
	for (i=length-2;i>=0;i--) {
		start = col2cl[i];
		finish = col2cl[i+1];

		if(!symmetric) {
			/* invert the diagonals and find the answers */
			for (cl_ind=start;cl_ind<finish;cl_ind++) {
				if (my_id == proc[cl_ind]) {
					/* first, multiply the clique */
					/* only do the strictly upper triangular part */
					x[d_mats[cl_ind].local_ind] *= *(d_mats[cl_ind].matrix);
				}
			}
		}

		/* first send my messages */
		/* this will involve computing partial sums */
		to_phase = BMget_phase(to_msg,i); CHKERR(0);
		msg = NULL;
		while ((msg = BMnext_msg(to_phase,msg)) != NULL) {
			CHKERR(0);
			msg_buf = (FLOAT *) BMget_msg_ptr(msg); CHKERR(0);
			data_ptr = BMget_user(msg,&msg_len); CHKERR(0);
			if(symmetric) {
				count = 0;
				for (cl_ind=data_ptr[0];cl_ind<=data_ptr[1];cl_ind++) {
					in_ind=in_index[cl_ind];
					size = inodes[in_ind].length;
					if (size > 0) {
						row = inodes[in_ind].row_num;
						nz = inodes[in_ind].nz;
						t = 0.0;
						for (k=0;k<size;k++) t += nz[k]*x[row[k]];
						msg_buf[count] = t;
					}
					count++;
				}
			} else {
				for (j=0; j<msg_len; j++)
					msg_buf[j] = x[data_ptr[j]];
			}
			BMsendf_msg(msg,procinfo); CHKERR(0);
		}
		CHKERR(0);

		/* do some local work, multiply by the i-nodes */
		for (cl_ind=start;cl_ind<finish;cl_ind++) {
			if (my_id == proc[cl_ind]) {
				in_ind=in_index[cl_ind];
				size = inodes[in_ind].length;
				if (size > 0) {
					ind = d_mats[cl_ind].local_ind;
					row = inodes[in_ind].row_num;
					nz = inodes[in_ind].nz;
					if(symmetric) {
						t = 0.0;
						for (k=0;k<size;k++) t += nz[k]*x[row[k]];
						x[ind] -= t;
					} else {
						t = x[ind];
						for (k=0;k<size;k++) {
							if (gnum[iperm[row[k]]] < inodes[in_ind].gcol_num) {
								x[row[k]] -= t*nz[k];
							}
						}
					}
				}
			}
		}

		/* receive my messages and update my rhs */
		from_phase = BMget_phase(from_msg,i); CHKERR(0);
		while ((msg = BMrecv_msg(from_phase)) != NULL) {
			CHKERR(0);
			msg_buf = (FLOAT *) BMget_msg_ptr(msg); CHKERR(0);
			data_ptr = BMget_user(msg,&msg_len); CHKERR(0);
			if(symmetric) {
				msg_len = BMget_msg_size(msg); CHKERR(0);
				for (j=0;j<msg_len;j++) x[data_ptr[j]] -= msg_buf[j];
			} else {
				count = 0;
				for (cl_ind=data_ptr[0];cl_ind<=data_ptr[1];cl_ind++) {
					in_ind=in_index[cl_ind];
					size = inodes[in_ind].length;
					if (size > 0) {
						row = inodes[in_ind].row_num;
						nz = inodes[in_ind].nz;
						t = msg_buf[count];
						for (k=0;k<size;k++) {
							if (gnum[iperm[row[k]]] < inodes[in_ind].gcol_num) {
								x[row[k]] -= t*nz[k];
							}
						}
					}
					count++;
				}
			}
			BMfree_msg(msg); CHKERR(0);
		}
		CHKERR(0);

		if(symmetric) {
			/* invert the diagonals and find the answers */
			for (cl_ind=start;cl_ind<finish;cl_ind++) {
				if (my_id == proc[cl_ind]) {
					/* first, multiply the clique */
					/* only do the strictly upper triangular part */
					/* we ASSUME the diagonal is all 1's */
					x[d_mats[cl_ind].local_ind] *= *(d_mats[cl_ind].matrix);
				}
			}
		}

	}
	/* wait for all of the sent messages to finish */
	BMfinish_comp_msg(to_msg,procinfo); CHKERR(0);
	MLOG_flop((2*A->local_nnz));
}