PDLANHS(l) | LAPACK auxiliary routine (version 1.5) | PDLANHS(l) |
NAME¶
PDLANHS - return the value of the one norm, or the Frobenius norm,SYNOPSIS¶
- DOUBLE PRECISION
- FUNCTION PDLANHS( NORM, N, A, IA, JA, DESCA,WORK )
PURPOSE¶
PDLANHS returns the value of the one norm, or the Frobenius norm, or the infinity norm, or the element of largest absolute value of a Hessenberg distributed matrix sub( A ) = A(IA:IA+N-1,JA:JA+N-1). PDLANHS returns the value( max(abs(A(i,j))), NORM = 'M' or 'm' with IA <= i <= IA+N-1,
( and JA <= j <= JA+N-1,
(
( norm1( sub( A ) ), NORM = '1', 'O' or 'o'
(
( normI( sub( A ) ), NORM = 'I' or 'i'
(
( normF( sub( A ) ), NORM = 'F', 'f', 'E' or 'e'
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¶
- NORM (global input) CHARACTER
- Specifies the value to be returned in PDLANHS as describedabove.
- N (global input) INTEGER
- The number of rows and columns to be operated on i.e thenumber of rows and columns of the distributed submatrix sub( A ). When N = 0, PDLANHS is set to zero. N >= 0.
- A (local input) DOUBLE PRECISION pointer into the local memory
- to an array of dimension (LLD_A, LOCc(JA+N-1) ) containingthe local pieces of sub( A ).
- IA (global input) INTEGER
- The row index in the global array A indicating the firstrow of sub( A ).
- JA (global input) INTEGER
- The column index in the global array A indicating thefirst column of sub( A ).
- DESCA (global and local input) INTEGER array of dimension DLEN_.
- The array descriptor for the distributed matrix A.
- WORK (local workspace) DOUBLE PRECISION array dimension (LWORK)
- LWORK >= 0 if NORM = 'M' or 'm' (not referenced),Nq0 if NORM = '1', 'O' or 'o', Mp0 if NORM = 'I' or 'i', 0 if NORM = 'F', 'f', 'E' or 'e' (not referenced), where IROFFA = MOD( IA-1, MB_A ), ICOFFA = MOD( JA-1, NB_A ), IAROW = INDXG2P( IA, MB_A, MYROW, RSRC_A, NPROW ), IACOL = INDXG2P( JA, NB_A, MYCOL, CSRC_A, NPCOL ), Np0 = NUMROC( N+IROFFA, MB_A, MYROW, IAROW, NPROW ), Nq0 = NUMROC( N+ICOFFA, NB_A, MYCOL, IACOL, NPCOL ), INDXG2P and NUMROC are ScaLAPACK tool functions; MYROW, MYCOL, NPROW and NPCOL can be determined by calling the subroutine BLACS_GRIDINFO.
12 May 1997 | LAPACK version 1.5 |