SCALAPACK 2.2.2
LAPACK: Linear Algebra PACKage
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◆ pielset2()

subroutine pielset2 ( integer  alpha,
integer, dimension( * )  a,
integer  ia,
integer  ja,
integer, dimension( * )  desca,
integer  beta 
)

Definition at line 1 of file pielset2.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 ALPHA, BETA, IA, JA
10* ..
11* .. Array arguments ..
12 INTEGER A( * ), DESCA( * )
13* ..
14*
15* Purpose
16* =======
17*
18* PIELSET2 sets alpha to the distributed matrix entry A(IA,JA)
19* and A(IA,JA) to beta.
20*
21* Notes
22* =====
23*
24* Each global data object is described by an associated description
25* vector. This vector stores the information required to establish
26* the mapping between an object element and its corresponding process
27* and memory location.
28*
29* Let A be a generic term for any 2D block cyclicly distributed array.
30* Such a global array has an associated description vector DESCA.
31* In the following comments, the character _ should be read as
32* "of the global array".
33*
34* NOTATION STORED IN EXPLANATION
35* --------------- -------------- --------------------------------------
36* DTYPE_A(global) DESCA( DTYPE_ )The descriptor type. In this case,
37* DTYPE_A = 1.
38* CTXT_A (global) DESCA( CTXT_ ) The BLACS context handle, indicating
39* the BLACS process grid A is distribu-
40* ted over. The context itself is glo-
41* bal, but the handle (the integer
42* value) may vary.
43* M_A (global) DESCA( M_ ) The number of rows in the global
44* array A.
45* N_A (global) DESCA( N_ ) The number of columns in the global
46* array A.
47* MB_A (global) DESCA( MB_ ) The blocking factor used to distribute
48* the rows of the array.
49* NB_A (global) DESCA( NB_ ) The blocking factor used to distribute
50* the columns of the array.
51* RSRC_A (global) DESCA( RSRC_ ) The process row over which the first
52* row of the array A is distributed.
53* CSRC_A (global) DESCA( CSRC_ ) The process column over which the
54* first column of the array A is
55* distributed.
56* LLD_A (local) DESCA( LLD_ ) The leading dimension of the local
57* array. LLD_A >= MAX(1,LOCr(M_A)).
58*
59* Let K be the number of rows or columns of a distributed matrix,
60* and assume that its process grid has dimension p x q.
61* LOCr( K ) denotes the number of elements of K that a process
62* would receive if K were distributed over the p processes of its
63* process column.
64* Similarly, LOCc( K ) denotes the number of elements of K that a
65* process would receive if K were distributed over the q processes of
66* its process row.
67* The values of LOCr() and LOCc() may be determined via a call to the
68* ScaLAPACK tool function, NUMROC:
69* LOCr( M ) = NUMROC( M, MB_A, MYROW, RSRC_A, NPROW ),
70* LOCc( N ) = NUMROC( N, NB_A, MYCOL, CSRC_A, NPCOL ).
71* An upper bound for these quantities may be computed by:
72* LOCr( M ) <= ceil( ceil(M/MB_A)/NPROW )*MB_A
73* LOCc( N ) <= ceil( ceil(N/NB_A)/NPCOL )*NB_A
74*
75* Arguments
76* =========
77*
78* ALPHA (local output) @(typec)
79* The scalar alpha.
80*
81* A (local input/local ouput) @(typec) pointer into the
82* local memory to an array of dimension (LLD_A,*) containing
83* the local pieces of the distributed matrix A.
84*
85* IA (global input) INTEGER
86* The row index in the global array A indicating the first
87* row of sub( A ).
88*
89* JA (global input) INTEGER
90* The column index in the global array A indicating the
91* first column of sub( A ).
92*
93* DESCA (global and local input) INTEGER array of dimension DLEN_.
94* The array descriptor for the distributed matrix A.
95*
96* BETA (local input) @(typec)
97* The scalar beta.
98*
99* =====================================================================
100*
101* .. Parameters ..
102 INTEGER BLOCK_CYCLIC_2D, CSRC_, CTXT_, DLEN_, DTYPE_,
103 $ LLD_, MB_, M_, NB_, N_, RSRC_
104 parameter( block_cyclic_2d = 1, dlen_ = 9, dtype_ = 1,
105 $ ctxt_ = 2, m_ = 3, n_ = 4, mb_ = 5, nb_ = 6,
106 $ rsrc_ = 7, csrc_ = 8, lld_ = 9 )
107 INTEGER ZERO
108 parameter( zero = 0 )
109* ..
110* .. Local Scalars ..
111 INTEGER IACOL, IAROW, IIA, IOFFA, JJA, MYCOL, MYROW,
112 $ NPCOL, NPROW
113* ..
114* .. External Subroutines ..
115 EXTERNAL blacs_gridinfo, infog2l
116* ..
117* .. Executable Statements ..
118*
119* Get grid parameters.
120*
121 CALL blacs_gridinfo( desca( ctxt_ ), nprow, npcol, myrow, mycol )
122*
123 CALL infog2l( ia, ja, desca, nprow, npcol, myrow, mycol, iia, jja,
124 $ iarow, iacol )
125*
126 IF( myrow.EQ.iarow .AND. mycol.EQ.iacol ) THEN
127 ioffa = iia+(jja-1)*desca( lld_ )
128 alpha = a( ioffa )
129 a( ioffa ) = beta
130 ELSE
131 alpha = zero
132 END IF
133*
134 RETURN
135*
136* End of PIELSET2
137*
infog2l
subroutine infog2l(grindx, gcindx, desc, nprow, npcol, myrow, mycol, lrindx, lcindx, rsrc, csrc)
Definition infog2l.f:3
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