f11znc takes a coordinate storage (CS) representation (see
Section 2.1.1 in the
F11 Chapter Introduction) of a sparse
by
complex non-Hermitian matrix
, and reorders the nonzero elements by increasing row index and increasing column index within each row. Entries with duplicate row and column indices may be removed. Alternatively, duplicate entries may be summed, which facilitates spare matrix addition (see
Section 9). Any entries with zero values may optionally be removed.
f11znc also returns a pointer array
istr to the starting address of each row in
. This can be used to construct a compressed column storage (CCS) representation of the matrix (see
Section 9).
None.
-
1:
– Integer
Input
-
On entry: , the order of the matrix .
Constraint:
.
-
2:
– Integer *
Input/Output
-
On entry: the number of elements supplied in the array
a.
Constraint:
.
On exit: the number of elements with unique row and column indices.
-
3:
– Complex
Input/Output
-
Note: the dimension,
dim, of the array
a
must be at least
.
On entry: the nonzero elements of the matrix . These may be in any order and there may be multiple nonzero elements with the same row and column indices.
On exit: the nonzero elements ordered by increasing row index, and by increasing column index within each row. Each nonzero element has a unique row and column index.
-
4:
– Integer
Input/Output
-
Note: the dimension,
dim, of the array
irow
must be at least
.
On entry: the row indices corresponding to the elements supplied in the array
a.
Constraint:
, for .
On exit: the first
nnz elements contain the row indices corresponding to the elements returned in the array
a.
-
5:
– Integer
Input/Output
-
Note: the dimension,
dim, of the array
icol
must be at least
.
On entry: the column indices corresponding to the elements supplied in the array
a.
Constraint:
, for .
On exit: the first
nnz elements contain the column indices corresponding to the elements returned in the array
a.
-
6:
– Nag_SparseNsym_Dups
Input
-
On entry: indicates how elements in
a with duplicate row and column indices are to be treated.
- Duplicate entries are removed, only the first entry is kept.
- The relevant values in a are summed.
- The function fails with NE_NON_ZERO_DUP on detecting a duplicate.
Constraint:
, or .
-
7:
– Nag_SparseNsym_Zeros
Input
-
On entry: indicates how elements in
a with zero values are to be treated.
- The entries are removed.
- The entries are kept.
- The function fails with NE_ZERO_COEFF on detecting a zero.
Constraint:
, or .
-
8:
– Integer
Output
-
On exit:
, for
, is the starting address in the arrays
a,
irow and
icol of row
of the matrix
.
is the address of the last element in
a plus one.
-
9:
– NagError *
Input/Output
-
The NAG error argument (see
Section 7 in the Introduction to the NAG Library CL Interface).
- NE_ALLOC_FAIL
-
Dynamic memory allocation failed.
See
Section 3.1.2 in the Introduction to the NAG Library CL Interface for further information.
- NE_BAD_PARAM
-
On entry, argument had an illegal value.
- NE_INT
-
On entry, .
Constraint: .
On entry, .
Constraint: .
- NE_INTERNAL_ERROR
-
An internal error has occurred in this function. Check the function call and any array sizes. If the call is correct then please contact
NAG for assistance.
See
Section 7.5 in the Introduction to the NAG Library CL Interface for further information.
- NE_INVALID_CS
-
On entry, , and .
Constraint: and .
On entry, , and .
Constraint: and .
- NE_NO_LICENCE
-
Your licence key may have expired or may not have been installed correctly.
See
Section 8 in the Introduction to the NAG Library CL Interface for further information.
- NE_NON_ZERO_DUP
-
On entry, a duplicate entry has been found in row and column : , .
- NE_ZERO_COEFF
-
On entry, a zero entry has been found in row and column : , .
Not applicable.
The time taken for a call to
f11znc is the sum of two contributions, where one is proportional to
nnz and the other is proportional to
n.
Note that the resulting matrix may have either rows or columns with no entries. If row has no entries then .
To transpose a matrix in CS format simply interchange
irow and
icol. If you need the elements to be sorted, then pass these interchanged arrays to
f11znc.
Two sparse matrices can be added by concatenating the three pairs of CS format arrays, representing the two matrices, and passing these new arrays to
f11znc, specifying that duplicates should be summed. This functionality is illustrated in
Section 10 in
f11zac.
It is also possible to use this function to convert between coordinate storage (CS) and compressed column storage (CCS) formats. To achieve this the CS format array holding the row indices must be passed as
icol and the array holding the column indices must be passed as
irow in a call to
f11znc. On exit from
f11znc, the CCS representation of the matrix is given by the output arrays
a,
icol, and
istr, where
icol holds
irowix and
istr holds
icolzp as described in
Section 2.1.3 in the
F11 Chapter Introduction. This is illustrated in
Section 10 in
f11zac.