1 /* ---------------------------------------------------------------------
2 *
3 * -- PBLAS auxiliary routine (version 2.0) --
4 * University of Tennessee, Knoxville, Oak Ridge National Laboratory,
5 * and University of California, Berkeley.
6 * April 1, 1998
7 *
8 * ---------------------------------------------------------------------
9 */
10 /*
11 * Include files
12 */
13 #include "../pblas.h"
14 #include "../PBpblas.h"
15 #include "../PBtools.h"
16 #include "../PBblacs.h"
17 #include "../PBblas.h"
18
19 #ifdef __STDC__
PB_Cdescset(int * DESC,int M,int N,int IMB,int INB,int MB,int NB,int RSRC,int CSRC,int CTXT,int LLD)20 void PB_Cdescset( int * DESC, int M, int N, int IMB, int INB, int MB, int NB,
21 int RSRC, int CSRC, int CTXT, int LLD )
22 #else
23 void PB_Cdescset( DESC, M, N, IMB, INB, MB, NB, RSRC, CSRC, CTXT, LLD )
24 /*
25 * .. Scalar Arguments ..
26 */
27 int CSRC, CTXT, IMB, INB, LLD, M, MB, N, NB, RSRC;
28 /*
29 * .. Array Arguments ..
30 */
31 int * DESC;
32 #endif
33 {
34 /*
35 * Purpose
36 * =======
37 *
38 * PB_Cdescset uses its 10 input arguments M, N, IMB, INB, MB, NB,
39 * RSRC, CSRC, CTXT and LLD to initialize a descriptor vector of type
40 * BLOCK_CYCLIC_2D_INB.
41 *
42 * Notes
43 * =====
44 *
45 * A description vector is associated with each 2D block-cyclicly dis-
46 * tributed matrix. This vector stores the information required to
47 * establish the mapping between a matrix entry and its corresponding
48 * process and memory location.
49 *
50 * In the following comments, the character _ should be read as
51 * "of the distributed matrix". Let A be a generic term for any 2D
52 * block cyclicly distributed matrix. Its description vector is DESC_A:
53 *
54 * NOTATION STORED IN EXPLANATION
55 * ---------------- --------------- ------------------------------------
56 * DTYPE_A (global) DESCA[ DTYPE_ ] The descriptor type.
57 * CTXT_A (global) DESCA[ CTXT_ ] The BLACS context handle, indicating
58 * the NPROW x NPCOL BLACS process grid
59 * A is distributed over. The context
60 * itself is global, but the handle
61 * (the integer value) may vary.
62 * M_A (global) DESCA[ M_ ] The number of rows in the distribu-
63 * ted matrix A, M_A >= 0.
64 * N_A (global) DESCA[ N_ ] The number of columns in the distri-
65 * buted matrix A, N_A >= 0.
66 * IMB_A (global) DESCA[ IMB_ ] The number of rows of the upper left
67 * block of the matrix A, IMB_A > 0.
68 * INB_A (global) DESCA[ INB_ ] The number of columns of the upper
69 * left block of the matrix A,
70 * INB_A > 0.
71 * MB_A (global) DESCA[ MB_ ] The blocking factor used to distri-
72 * bute the last M_A-IMB_A rows of A,
73 * MB_A > 0.
74 * NB_A (global) DESCA[ NB_ ] The blocking factor used to distri-
75 * bute the last N_A-INB_A columns of
76 * A, NB_A > 0.
77 * RSRC_A (global) DESCA[ RSRC_ ] The process row over which the first
78 * row of the matrix A is distributed,
79 * NPROW > RSRC_A >= 0.
80 * CSRC_A (global) DESCA[ CSRC_ ] The process column over which the
81 * first column of A is distributed.
82 * NPCOL > CSRC_A >= 0.
83 * LLD_A (local) DESCA[ LLD_ ] The leading dimension of the local
84 * array storing the local blocks of
85 * the distributed matrix A,
86 * IF( Lc( 1, N_A ) > 0 )
87 * LLD_A >= MAX( 1, Lr( 1, M_A ) )
88 * ELSE
89 * LLD_A >= 1.
90 *
91 * Let K be the number of rows of a matrix A starting at the global in-
92 * dex IA,i.e, A( IA:IA+K-1, : ). Lr( IA, K ) denotes the number of rows
93 * that the process of row coordinate MYROW ( 0 <= MYROW < NPROW ) would
94 * receive if these K rows were distributed over NPROW processes. If K
95 * is the number of columns of a matrix A starting at the global index
96 * JA, i.e, A( :, JA:JA+K-1, : ), Lc( JA, K ) denotes the number of co-
97 * lumns that the process MYCOL ( 0 <= MYCOL < NPCOL ) would receive if
98 * these K columns were distributed over NPCOL processes.
99 *
100 * The values of Lr() and Lc() may be determined via a call to the func-
101 * tion PB_Cnumroc:
102 * Lr( IA, K ) = PB_Cnumroc( K, IA, IMB_A, MB_A, MYROW, RSRC_A, NPROW )
103 * Lc( JA, K ) = PB_Cnumroc( K, JA, INB_A, NB_A, MYCOL, CSRC_A, NPCOL )
104 *
105 * Arguments
106 * =========
107 *
108 * DESC (global and local output) INTEGER array
109 * On entry, DESC is an array of dimension DLEN_. DESC is the
110 * array descriptor to be set.
111 *
112 * M (global input) INTEGER
113 * On entry, M specifies the number of rows of the matrix.
114 * M must be at least zero.
115 *
116 * N (global input) INTEGER
117 * On entry, N specifies the number of columns of the matrix.
118 * N must be at least zero.
119 *
120 * IMB (global input) INTEGER
121 * On entry, IMB specifies the row size of the first block of
122 * the global matrix distribution. IMB must be at least one.
123 *
124 * INB (global input) INTEGER
125 * On entry, INB specifies the column size of the first block
126 * of the global matrix distribution. INB must be at least one.
127 *
128 * MB (global input) INTEGER
129 * On entry, MB specifies the row size of the blocks used to
130 * partition the matrix. MB must be at least one.
131 *
132 * NB (global input) INTEGER
133 * On entry, NB specifies the column size of the blocks used to
134 * partition the matrix. NB must be at least one.
135 *
136 * RSRC (global input) INTEGER
137 * On entry, RSRC specifies the row coordinate of the process
138 * that possesses the first row of the matrix. When RSRC = -1,
139 * the data is not distributed but replicated, otherwise RSRC
140 * must be at least zero and strictly less than NPROW.
141 *
142 * CSRC (global input) INTEGER
143 * On entry, CSRC specifies the column coordinate of the pro-
144 * cess that possesses the first column of the matrix. When
145 * CSRC = -1, the data is not distributed but replicated, other-
146 * wise CSRC must be at least zero and strictly less than NPCOL.
147 *
148 * CTXT (local input) INTEGER
149 * On entry, CTXT specifies the BLACS context handle, indicating
150 * the global communication context. The value of the context
151 * itself is local.
152 *
153 * LLD (local input) INTEGER
154 * On entry, LLD specifies the leading dimension of the local
155 * array storing the local entries of the matrix. LLD must be at
156 * least MAX( 1, Lr(1,M) ).
157 *
158 * -- Written on April 1, 1998 by
159 * Antoine Petitet, University of Tennessee, Knoxville 37996, USA.
160 *
161 * ---------------------------------------------------------------------
162 */
163 /* ..
164 * .. Executable Statements ..
165 *
166 */
167 DESC[DTYPE_] = BLOCK_CYCLIC_2D_INB;
168 DESC[CTXT_ ] = CTXT;
169 DESC[M_ ] = M;
170 DESC[N_ ] = N;
171 DESC[IMB_ ] = IMB;
172 DESC[INB_ ] = INB;
173 DESC[MB_ ] = MB;
174 DESC[NB_ ] = NB;
175 DESC[RSRC_ ] = RSRC;
176 DESC[CSRC_ ] = CSRC;
177 DESC[LLD_ ] = LLD;
178 /*
179 * End of PB_Cdescset
180 */
181 }
182