On entry: if
${\mathbf{JCEVAL}}=\text{'S'}$,
$\text{'F'}$ or
$\text{'D'}$,
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
$1,2,\dots ,{\mathbf{NEQ}}$ in that order, with
${\mathbf{IA}}\left(1\right)=1$. Thus for each column index
$j=1,2,\dots ,{\mathbf{NEQ}}$, the values of the row index
$i$ in column
$j$ where a nonzero element may occur are given by
where
${\mathbf{IA}}\left(j\right)\le k<{\mathbf{IA}}\left(j+1\right)$.
Thus the total number of nonzeros,
$\mathit{nelement}$, must be
${\mathbf{IA}}\left({\mathbf{NEQ}}+1\right)-1$. 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
${\mathbf{JCEVAL}}=\text{'N'}$ or
$\text{'A'}$.