table of contents
PCLACON(l) | LAPACK auxiliary routine (version 1.5) | PCLACON(l) |
NAME¶
PCLACON - estimate the 1-norm of a square, complex distributed matrix ASYNOPSIS¶
- SUBROUTINE PCLACON(
- N, V, IV, JV, DESCV, X, IX, JX, DESCX, EST, KASE )
PURPOSE¶
PCLACON estimates the 1-norm of a square, complex distributed matrix A. Reverse communication is used for evaluating matrix-vector products. X and V are aligned with the distributed matrix A, this information is implicitly contained within IV, IX, DESCV, and DESCX. NotesDTYPE_A = 1.
the BLACS process grid A is distribu-
ted over. The context itself is glo-
bal, but the handle (the integer
value) may vary.
array A.
array A.
the rows of the array.
the columns of the array.
row of the array A is distributed. CSRC_A (global) DESCA( CSRC_ ) The process column over which the
first column of the array A is
distributed.
array. LLD_A >= MAX(1,LOCr(M_A)). Let K be the number of rows or columns of a distributed matrix, and assume that its process grid has dimension p x q.
LOCr( M ) = NUMROC( M, MB_A, MYROW, RSRC_A, NPROW ),
LOCc( N ) = NUMROC( N, NB_A, MYCOL, CSRC_A, NPCOL ). An upper bound for these quantities may be computed by:
LOCr( M ) <= ceil( ceil(M/MB_A)/NPROW )*MB_A
LOCc( N ) <= ceil( ceil(N/NB_A)/NPCOL )*NB_A
ARGUMENTS¶
- N (global input) INTEGER
- The length of the distributed vectors V and X. N >= 0.
- V (local workspace) COMPLEX pointer into the local
- memory to an array of dimension LOCr(N+MOD(IV-1,MB_V)). On the final return, V = A*W, where EST = norm(V)/norm(W) (W is not returned).
- IV (global input) INTEGER
- The row index in the global array V indicating the first row of sub( V ).
- JV (global input) INTEGER
- The column index in the global array V indicating the first column of sub( V ).
- DESCV (global and local input) INTEGER array of dimension DLEN_.
- The array descriptor for the distributed matrix V.
- X (local input/local output) COMPLEX pointer into the
- local memory to an array of dimension LOCr(N+MOD(IX-1,MB_X)). On an intermediate return, X should be overwritten by A * X, if KASE=1, A' * X, if KASE=2, where A' is the conjugate transpose of A, and PCLACON must be re-called with all the other parameters unchanged.
- IX (global input) INTEGER
- The row index in the global array X indicating the first row of sub( X ).
- JX (global input) INTEGER
- The column index in the global array X indicating the first column of sub( X ).
- DESCX (global and local input) INTEGER array of dimension DLEN_.
- The array descriptor for the distributed matrix X.
- EST (global output) REAL
- An estimate (a lower bound) for norm(A).
- KASE (local input/local output) INTEGER
- On the initial call to PCLACON, KASE should be 0. On an intermediate return, KASE will be 1 or 2, indicating whether X should be overwritten by A * X or A' * X. On the final return from PCLACON, KASE will again be 0.
FURTHER DETAILS¶
The serial version CLACON has been contributed by Nick Higham, University of Manchester. It was originally named SONEST, dated March 16, 1988.12 May 1997 | LAPACK version 1.5 |