f11zpf takes a symmetric coordinate storage (SCS) representation (see
Section 2.1.2 in the F11 Chapter Introduction) of a sparse
by
complex 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.
f11zpf also returns a pointer array
istr to the starting address of each row in
.
None.
- 1: – IntegerInput
-
On entry: , the order of the matrix .
Constraint:
.
- 2: – IntegerInput/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 (Kind=nag_wp) arrayInput/Output
-
Note: the dimension of the array
a
must be at least
.
On entry: the nonzero elements of the lower triangular part of the complex matrix . These may be in any order and there may be multiple nonzero elements with the same row and column indices.
On exit: the lower triangular 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 arrayInput/Output
-
Note: the dimension 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 arrayInput/Output
-
Note: the dimension 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: – Character(1)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 routine fails with on detecting a duplicate.
Constraint:
, or .
- 7: – Character(1)Input
-
On entry: indicates how elements in
a with zero values are to be treated.
- The entries are removed.
- The entries are kept.
- The routine fails with on detecting a zero.
Constraint:
, or .
- 8: – Integer arrayOutput
-
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: – Integer arrayWorkspace
-
- 10: – IntegerInput/Output
-
On entry:
ifail must be set to
,
. If you are unfamiliar with this argument you should refer to
Section 3.4 in How to Use the NAG Library and its Documentation for details.
For environments where it might be inappropriate to halt program execution when an error is detected, the value
is recommended. If the output of error messages is undesirable, then the value
is recommended. Otherwise, if you are not familiar with this argument, the recommended value is
.
When the value is used it is essential to test the value of ifail on exit.
On exit:
unless the routine detects an error or a warning has been flagged (see
Section 6).
If on entry
or
, explanatory error messages are output on the current error message unit (as defined by
x04aaf).
Not applicable.
The time taken for a call to
f11zpf 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 .
Two sparse matrices can be added by concatenating the three pairs of SCS format arrays, representing the two matrices, and passing these new arrays to
f11zpf, specifying that duplicates should be summed. This functionality is illustrated in
Section 10 in
f11zaf.