PZLARFG(l) | LAPACK auxiliary routine (version 1.5) | PZLARFG(l) |
NAME¶
PZLARFG - generate a complex elementary reflector H of order n, such that H * sub( X ) = H * ( x(iax,jax) ) = ( alpha ), H' * H = ISYNOPSIS¶
- SUBROUTINE PZLARFG(
- N, ALPHA, IAX, JAX, X, IX, JX, DESCX, INCX, TAU )
PURPOSE¶
PZLARFG generates a complex elementary reflector H of order n, such that( x ) ( 0 )
H = I - tau * ( 1 ) * ( 1 v' ) ,
( v )
DTYPE_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 global order of the elementary reflector. N >= 0.
- ALPHA (local output) COMPLEX*16
- On exit, alpha is computed in the process scope having the vector sub( X ).
- IAX (global input) INTEGER
- The global row index in X of X(IAX,JAX).
- JAX (global input) INTEGER
- The global column index in X of X(IAX,JAX).
- X (local input/local output) COMPLEX*16, pointer into the
- local memory to an array of dimension (LLD_X,*). This array contains the local pieces of the distributed vector sub( X ). Before entry, the incremented array sub( X ) must contain the vector x. On exit, it is overwritten with the vector v.
- 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.
- INCX (global input) INTEGER
- The global increment for the elements of X. Only two values of INCX are supported in this version, namely 1 and M_X. INCX must not be zero.
- TAU (local output) COMPLEX*16, array, dimension LOCc(JX)
- if INCX = 1, and LOCr(IX) otherwise. This array contains the Householder scalars related to the Householder vectors. TAU is tied to the distributed matrix X.
12 May 1997 | LAPACK version 1.5 |