SCALAPACK 2.2.2
LAPACK: Linear Algebra PACKage
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◆ pcelset()

subroutine pcelset ( complex, dimension( * )  a,
integer  ia,
integer  ja,
integer, dimension( * )  desca,
complex  alpha 
)

Definition at line 1 of file pcelset.f.

2*
3* -- ScaLAPACK tools routine (version 1.7) --
4* University of Tennessee, Knoxville, Oak Ridge National Laboratory,
5* and University of California, Berkeley.
6* May 1, 1997
7*
8* .. Scalar Arguments ..
9 INTEGER IA, JA
10 COMPLEX ALPHA
11* ..
12* .. Array arguments ..
13 INTEGER DESCA( * )
14 COMPLEX A( * )
15* ..
16*
17* Purpose
18* =======
19*
20* PCELSET sets the distributed matrix entry A( IA, JA ) to ALPHA.
21*
22* Notes
23* =====
24*
25* Each global data object is described by an associated description
26* vector. This vector stores the information required to establish
27* the mapping between an object element and its corresponding process
28* and memory location.
29*
30* Let A be a generic term for any 2D block cyclicly distributed array.
31* Such a global array has an associated description vector DESCA.
32* In the following comments, the character _ should be read as
33* "of the global array".
34*
35* NOTATION STORED IN EXPLANATION
36* --------------- -------------- --------------------------------------
37* DTYPE_A(global) DESCA( DTYPE_ )The descriptor type. In this case,
38* DTYPE_A = 1.
39* CTXT_A (global) DESCA( CTXT_ ) The BLACS context handle, indicating
40* the BLACS process grid A is distribu-
41* ted over. The context itself is glo-
42* bal, but the handle (the integer
43* value) may vary.
44* M_A (global) DESCA( M_ ) The number of rows in the global
45* array A.
46* N_A (global) DESCA( N_ ) The number of columns in the global
47* array A.
48* MB_A (global) DESCA( MB_ ) The blocking factor used to distribute
49* the rows of the array.
50* NB_A (global) DESCA( NB_ ) The blocking factor used to distribute
51* the columns of the array.
52* RSRC_A (global) DESCA( RSRC_ ) The process row over which the first
53* row of the array A is distributed.
54* CSRC_A (global) DESCA( CSRC_ ) The process column over which the
55* first column of the array A is
56* distributed.
57* LLD_A (local) DESCA( LLD_ ) The leading dimension of the local
58* array. LLD_A >= MAX(1,LOCr(M_A)).
59*
60* Let K be the number of rows or columns of a distributed matrix,
61* and assume that its process grid has dimension p x q.
62* LOCr( K ) denotes the number of elements of K that a process
63* would receive if K were distributed over the p processes of its
64* process column.
65* Similarly, LOCc( K ) denotes the number of elements of K that a
66* process would receive if K were distributed over the q processes of
67* its process row.
68* The values of LOCr() and LOCc() may be determined via a call to the
69* ScaLAPACK tool function, NUMROC:
70* LOCr( M ) = NUMROC( M, MB_A, MYROW, RSRC_A, NPROW ),
71* LOCc( N ) = NUMROC( N, NB_A, MYCOL, CSRC_A, NPCOL ).
72* An upper bound for these quantities may be computed by:
73* LOCr( M ) <= ceil( ceil(M/MB_A)/NPROW )*MB_A
74* LOCc( N ) <= ceil( ceil(N/NB_A)/NPCOL )*NB_A
75*
76* Arguments
77* =========
78*
79* A (local output) COMPLEX pointer into the local memory
80* to an array of dimension (LLD_A,*) containing the local
81* pieces of the distributed matrix A.
82*
83* IA (global input) INTEGER
84* The row index in the global array A indicating the first
85* row of sub( A ).
86*
87* JA (global input) INTEGER
88* The column index in the global array A indicating the
89* first column of sub( A ).
90*
91* DESCA (global and local input) INTEGER array of dimension DLEN_.
92* The array descriptor for the distributed matrix A.
93*
94* ALPHA (local input) COMPLEX
95* The scalar alpha.
96*
97* =====================================================================
98*
99* .. Parameters ..
100 INTEGER BLOCK_CYCLIC_2D, CSRC_, CTXT_, DLEN_, DTYPE_,
101 $ LLD_, MB_, M_, NB_, N_, RSRC_
102 parameter( block_cyclic_2d = 1, dlen_ = 9, dtype_ = 1,
103 $ ctxt_ = 2, m_ = 3, n_ = 4, mb_ = 5, nb_ = 6,
104 $ rsrc_ = 7, csrc_ = 8, lld_ = 9 )
105* ..
106* .. Local Scalars ..
107 INTEGER IACOL, IAROW, IIA, JJA, MYCOL, MYROW, NPCOL,
108 $ NPROW
109* ..
110* .. External Subroutines ..
111 EXTERNAL blacs_gridinfo, infog2l
112* ..
113* .. Executable Statements ..
114*
115* Get grid parameters.
116*
117 CALL blacs_gridinfo( desca( ctxt_ ), nprow, npcol, myrow, mycol )
118*
119 CALL infog2l( ia, ja, desca, nprow, npcol, myrow, mycol, iia, jja,
120 $ iarow, iacol )
121*
122 IF( myrow.EQ.iarow .AND. mycol.EQ.iacol )
123 $ a( iia+(jja-1)*desca( lld_ ) ) = alpha
124*
125 RETURN
126*
127* End of PCELSET
128*
infog2l
subroutine infog2l(grindx, gcindx, desc, nprow, npcol, myrow, mycol, lrindx, lcindx, rsrc, csrc)
Definition infog2l.f:3
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