On entry: if
JCEVAL='S',
'F' or
'D',
JA must contain details of the sparsity pattern to be used for the Jacobian.
JA contains the row indices where nonzero elements occur, reading in column-wise order, and
IA contains the starting locations in
JA of the descriptions of columns
1,2,…,NEQ in that order, with
IA1=1. Thus for each column index
j=1,2,…,NEQ, the values of the row index
i in column
j where a nonzero element may occur are given by
where
IAj≤k<IAj+1.
Thus the total number of nonzeros,
nelement, must be
IANEQ+1-1. For example, for the following matrix
where
x represents nonzero elements (13 in all) the arrays
IA and
JA should be
JA is not used if
JCEVAL='N' or
'A'.