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| # Variables: | 37 |
| # Callers: | 3 |
| # Callings: | 1 |
| # Words: | 128 |
| # Keywords: | 83 |
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..
.. Array Arguments ..
..
Purpose
=======
PSGETRS solves a system of distributed linear equations
op( sub( A ) ) * X = sub( B )
with a general N-by-N distributed matrix sub( A ) using the LU
factorization computed by PSGETRF.
sub( A ) denotes A(IA:IA+N-1,JA:JA+N-1), op( A ) = A or A**T and
sub( B ) denotes B(IB:IB+N-1,JB:JB+NRHS-1).
Notes
=====
Each global data object is described by an associated description
vector. This vector stores the information required to establish
the mapping between an object element and its corresponding process
and memory location.
Let A be a generic term for any 2D block cyclicly distributed array.
Such a global array has an associated description vector DESCA.
In the following comments, the character _ should be read as
"of the global array".
NOTATION STORED IN EXPLANATION
--------------- -------------- --------------------------------------
DTYPE_A(global) DESCA( DTYPE_ )The descriptor type. In this case,
DTYPE_A = 1.
CTXT_A (global) DESCA( CTXT_ ) The BLACS context handle, indicating
the BLACS process grid A is distribu-
ted over. The context itself is glo-
bal, but the handle (the integer
value) may vary.
M_A (global) DESCA( M_ ) The number of rows in the global
array A.
N_A (global) DESCA( N_ ) The number of columns in the global
array A.
MB_A (global) DESCA( MB_ ) The blocking factor used to distribute
the rows of the array.
NB_A (global) DESCA( NB_ ) The blocking factor used to distribute
the columns of the array.
RSRC_A (global) DESCA( RSRC_ ) The process row over which the first
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.
LLD_A (local) DESCA( LLD_ ) The leading dimension of the local
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( K ) denotes the number of elements of K that a process
would receive if K were distributed over the p processes of its
process column.
Similarly, LOCc( K ) denotes the number of elements of K that a
process would receive if K were distributed over the q processes of
its process row.
The values of LOCr() and LOCc() may be determined via a call to the
ScaLAPACK tool function, NUMROC:
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
This routine requires square block data decomposition ( MB_A=NB_A ).
Arguments
=========
TRANS (global input) CHARACTER
Specifies the form of the system of equations:
= 'N': sub( A ) * X = sub( B ) (No transpose)
= 'T': sub( A )**T * X = sub( B ) (Transpose)
= 'C': sub( A )**T * X = sub( B ) (Transpose)
N (global input) INTEGER
The number of rows and columns to be operated on, i.e. the
order of the distributed submatrix sub( A ). N >= 0.
NRHS (global input) INTEGER
The number of right hand sides, i.e., the number of columns
of the distributed submatrix sub( B ). NRHS >= 0.
A (local input) REAL pointer into the local
memory to an array of dimension (LLD_A, LOCc(JA+N-1)).
On entry, this array contains the local pieces of the factors
L and U from the factorization sub( A ) = P*L*U; the unit
diagonal elements of L are not stored.
IA (global input) INTEGER
The row index in the global array A indicating the first
row of sub( A ).
JA (global input) INTEGER
The column index in the global array A indicating the
first column of sub( A ).
DESCA (global and local input) INTEGER array of dimension DLEN_.
The array descriptor for the distributed matrix A.
IPIV (local input) INTEGER array, dimension ( LOCr(M_A)+MB_A )
This array contains the pivoting information.
IPIV(i) -> The global row local row i was swapped with.
This array is tied to the distributed matrix A.
B (local input/local output) REAL pointer into the
local memory to an array of dimension
(LLD_B,LOCc(JB+NRHS-1)). On entry, the right hand sides
sub( B ). On exit, sub( B ) is overwritten by the solution
distributed matrix X.
IB (global input) INTEGER
The row index in the global array B indicating the first
row of sub( B ).
JB (global input) INTEGER
The column index in the global array B indicating the
first column of sub( B ).
DESCB (global and local input) INTEGER array of dimension DLEN_.
The array descriptor for the distributed matrix B.
INFO (global output) INTEGER
= 0: successful exit
< 0: If the i-th argument is an array and the j-entry had
an illegal value, then INFO = -(i*100+j), if the i-th
argument is a scalar and had an illegal value, then
INFO = -i.
=====================================================================
.. Parameters ..
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001 SUBROUTINE PSGETRS( TRANS , N , NRHS , A , IA , JA , DESCA , IPIV , B ,
002 $IB , JB , DESCB , INFO )
003
004 * -- ScaLAPACK routine(version 1.7) --
005 * University of Tennessee , Knoxville , Oak Ridge National Laboratory ,
006 * and University of California , Berkeley.
007 * May 1 , 1997
008
009 * .. Scalar Arguments ..
010 CHARACTER TRANS
011 INTEGER IA , IB , INFO , JA , JB , N , NRHS
012 INTEGER BLOCK_CYCLIC_2D , CSRC_ , CTXT_ , DLEN_ , DTYPE_ ,
013 $LLD_ , MB_ , M_ , NB_ , N_ , RSRC_
014 PARAMETER( BLOCK_CYCLIC_2D = 1 , DLEN_ = 9 , DTYPE_ = 1 ,
015 $CTXT_ = 2 , M_ = 3 , N_ = 4 , MB_ = 5 , NB_ = 6 ,
016 $RSRC_ = 7 , CSRC_ = 8 , LLD_ = 9 )
017 REAL ONE
018 PARAMETER( ONE = 1.0E + 0 )
019 * ..
020 * .. Local Scalars ..
021 LOGICAL NOTRAN
022 INTEGER IAROW , IBROW , ICOFFA , ICTXT , IROFFA , IROFFB ,
023 $MYCOL , MYROW , NPCOL , NPROW
024 * ..
025 * .. Local Arrays ..
026 INTEGER DESCIP( DLEN_ ) , IDUM1( 1 ) , IDUM2( 1 )
027 * ..
028 * .. External Subroutines ..
029 EXTERNAL BLACS_GRIDINFO , CHK1MAT , DESCSET , PCHK2MAT ,
030 $PSLAPIV , PSTRSM , PXERBLA
031 * ..
032 * .. External Functions ..
033 LOGICAL LSAME
034 INTEGER INDXG2P , NUMROC
035 EXTERNAL INDXG2P , LSAME , NUMROC
036 * ..
037 * .. Intrinsic Functions ..
038 INTRINSIC ICHAR , MOD
039 * ..
040 * .. Executable Statements ..
041
042 * Get grid parameters
043
044 ICTXT = DESCA( CTXT_ )
045 CALL BLACS_GRIDINFO( ICTXT , NPROW , NPCOL , MYROW , MYCOL )
046
047 * Test the input parameters
048
049 INFO = 0
050 IF( NPROW.EQ. - 1 ) THEN
050  
051 INFO = - (700 + CTXT_)
052 ELSE
052
053 NOTRAN = LSAME( TRANS , 'N' )
054 CALL CHK1MAT( N , 2 , N , 2 , IA , JA , DESCA , 7 , INFO )
055 CALL CHK1MAT( N , 2 , NRHS , 3 , IB , JB , DESCB , 12 , INFO )
056 IF( INFO.EQ.0 ) THEN
056
057 IAROW = INDXG2P( IA , DESCA( MB_ ) , MYROW , DESCA( RSRC_ ) ,
058 $ NPROW )
059 IBROW = INDXG2P( IB , DESCB( MB_ ) , MYROW , DESCB( RSRC_ ) ,
060 $ NPROW )
061 IROFFA = MOD( IA - 1 , DESCA( MB_ ) )
062 ICOFFA = MOD( JA - 1 , DESCA( NB_ ) )
063 IROFFB = MOD( IB - 1 , DESCB( MB_ ) )
064 IF( .NOT.NOTRAN .AND. .NOT.LSAME( TRANS , 'T' ) .AND. .NOT.
065 $ LSAME( TRANS , 'C' ) ) THEN
066 INFO = - 1
067 ELSE IF( IROFFA.NE.0 ) THEN
067
068 INFO = - 5
069 ELSE IF( ICOFFA.NE.0 ) THEN
069
070 INFO = - 6
071 ELSE IF( DESCA( MB_ ).NE.DESCA( NB_ ) ) THEN
071
072 INFO = - (700 + NB_)
073 ELSE IF( IROFFB.NE.0 .OR. IBROW.NE.IAROW ) THEN
073
074 INFO = - 10
075 ELSE IF( DESCB( MB_ ).NE.DESCA( NB_ ) ) THEN
075
076 INFO = - (1200 + NB_)
077 ELSE IF( ICTXT.NE.DESCB( CTXT_ ) ) THEN
077
078 INFO = - (1200 + CTXT_)
079 END IF
080 END IF
081 IF( NOTRAN ) THEN
081
082 IDUM1( 1 ) = ICHAR( 'N' )
083 ELSE IF( LSAME( TRANS , 'T' ) ) THEN
083
084 IDUM1( 1 ) = ICHAR( 'T' )
085 ELSE
085
086 IDUM1( 1 ) = ICHAR( 'C' )
087 END IF
088 IDUM2( 1 ) = 1
089 CALL PCHK2MAT( N , 2 , N , 2 , IA , JA , DESCA , 7 , N , 2 , NRHS , 3 ,
090 $IB , JB , DESCB , 12 , 1 , IDUM1 , IDUM2 , INFO )
091 END IF
092
093 IF( INFO.NE.0 ) THEN
093
094 CALL PXERBLA( ICTXT , 'PSGETRS' , - INFO )
095 RETURN
096 END IF
097
098 * Quick return if possible
099
100 IF( N.EQ.0 .OR. NRHS.EQ.0 )
100
101 $ RETURN
102
103 CALL DESCSET( DESCIP , DESCA( M_ ) + DESCA( MB_ )*NPROW , 1 ,
104 $ DESCA( MB_ ) , 1 , DESCA( RSRC_ ) , MYCOL , ICTXT ,
105 $ DESCA( MB_ ) + NUMROC( DESCA( M_ ) , DESCA( MB_ ) ,
106 $ MYROW , DESCA( RSRC_ ) , NPROW ) )
107
108 IF( NOTRAN ) THEN
109
110 * Solve sub( A ) * X = sub( B ).
111
112 * Apply row interchanges to the right hand sides.
113
113
114 CALL PSLAPIV ( 'Forward' , 'Row' , 'Col' , N , NRHS , B , IB , JB ,
115 $ DESCB , IPIV , IA , 1 , DESCIP , IDUM1 )
116
117 * Solve L*X = sub( B ) , overwriting sub( B ) with X.
118
119 CALL PSTRSM( 'Left' , 'Lower' , 'No transpose' , 'Unit' , N , NRHS ,
120 $ ONE , A , IA , JA , DESCA , B , IB , JB , DESCB )
121
122 * Solve U*X = sub( B ) , overwriting sub( B ) with X.
123
124 CALL PSTRSM( 'Left' , 'Upper' , 'No transpose' , 'Non - unit' , N ,
125 $ NRHS , ONE , A , IA , JA , DESCA , B , IB , JB , DESCB )
126 ELSE
127
128 * Solve sub( A )' * X = sub( B ).
129
130 * Solve U'*X = sub( B ) , overwriting sub( B ) with X.
131
131
132 CALL PSTRSM( 'Left' , 'Upper' , 'Transpose' , 'Non - unit' , N , NRHS ,
133 $ ONE , A , IA , JA , DESCA , B , IB , JB , DESCB )
134
135 * Solve L'*X = sub( B ) , overwriting sub( B ) with X.
136
137 CALL PSTRSM( 'Left' , 'Lower' , 'Transpose' , 'Unit' , N , NRHS ,
138 $ ONE , A , IA , JA , DESCA , B , IB , JB , DESCB )
139
140 * Apply row interchanges to the solution vectors.
141
142 CALL PSLAPIV ( 'Backward' , 'Row' , 'Col' , N , NRHS , B , IB , JB ,
143 $ DESCB , IPIV , IA , 1 , DESCIP , IDUM1 )
144
145 END IF
146
147 RETURN
148
149 * End of PSGETRS
150
151 END29
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Variables in Routine PSGETRS()
| Summary Report |
| Data Type | Quantity | Size(byte) |
| CHARACTER | 1 | 1 |
| INTEGER | 33 | 136 |
| LOGICAL | 2 | 2 |
| REAL | 1 | 4 |
| TOTAL | 37 | 143 |
List of Variables
CHARACTER
INTEGER
| BLOCK_CYCLIC_2D | CSRC_ | CTXT_ | DESCIP( DLEN_ ) | DLEN_ |
| DTYPE_ | IA | IAROW | IB | IBROW |
| ICOFFA | ICTXT | IDUM1( 1 ) | IDUM2( 1 ) | INDXG2P |
| INFO | IROFFA | IROFFB | JA | JB |
| LLD_ | M_ | MB_ | MYCOL | MYROW |
| N | N_ | NB_ | NPCOL | NPROW |
| NRHS | NUMROC | RSRC_ | | |
LOGICAL
REAL
Variables Dependence Graph
Put the mouse over a right hand side variable to display the corresponding line of the dependence | | - | | - | - | | IAROW | <--- | INDXG2PIAROW = INDXG2P( IA, DESCA( MB_ ), MYROW, DESCA( RSRC_ ),, MB_IAROW = INDXG2P( IA, DESCA( MB_ ), MYROW, DESCA( RSRC_ ),, MYROWIAROW = INDXG2P( IA, DESCA( MB_ ), MYROW, DESCA( RSRC_ ),, NPROWIAROW = INDXG2P( IA, DESCA( MB_ ), MYROW, DESCA( RSRC_ ),, RSRC_IAROW = INDXG2P( IA, DESCA( MB_ ), MYROW, DESCA( RSRC_ ),, IAIAROW = INDXG2P( IA, DESCA( MB_ ), MYROW, DESCA( RSRC_ ), |
| IBROW | <--- | INDXG2PIBROW = INDXG2P( IB, DESCB( MB_ ), MYROW, DESCB( RSRC_ ),, MB_IBROW = INDXG2P( IB, DESCB( MB_ ), MYROW, DESCB( RSRC_ ),, MYROWIBROW = INDXG2P( IB, DESCB( MB_ ), MYROW, DESCB( RSRC_ ),, NPROWIBROW = INDXG2P( IB, DESCB( MB_ ), MYROW, DESCB( RSRC_ ),, RSRC_IBROW = INDXG2P( IB, DESCB( MB_ ), MYROW, DESCB( RSRC_ ),, IBIBROW = INDXG2P( IB, DESCB( MB_ ), MYROW, DESCB( RSRC_ ), |
| ICOFFA | <--- | JAICOFFA = MOD( JA-1, DESCA( NB_ ) ), NB_ICOFFA = MOD( JA-1, DESCA( NB_ ) ) |
| ICTXT | <--- | CTXT_ICTXT = DESCA( CTXT_ ) |
| IDUM1 | <--- | NIDUM1( 1 ) = ICHAR( 'N' ) |
| INFO | <--- | NB_INFO = -(700+NB_){2INFO = -(1200+NB_)}, CTXT_INFO = -(700+CTXT_){2INFO = -(1200+CTXT_)} |
| IROFFA | <--- | MB_IROFFA = MOD( IA-1, DESCA( MB_ ) ), IAIROFFA = MOD( IA-1, DESCA( MB_ ) ) |
| IROFFB | <--- | MB_IROFFB = MOD( IB-1, DESCB( MB_ ) ), IBIROFFB = MOD( IB-1, DESCB( MB_ ) ) |
| NOTRAN | <--- | LSAMENOTRAN = LSAME( TRANS, 'N' ), NNOTRAN = LSAME( TRANS, 'N' ), TRANSNOTRAN = LSAME( TRANS, 'N' ) |
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Analysis elements of the routine PSGETRS()
Put the mouse over each element to display detailed matching information
 Assigned variables |
| | | BLOCK_CYCLIC_2D , CSRC_ , CTXT_ , DLEN_ , DTYPE_ , IAROW , IBROW , ICOFFA , ICTXT , IDUM1 , IDUM2 , INFO , IROFFA , IROFFB , LLD_ , M_ , MB_ , N_ , NB_ , NOTRAN , ONE , RSRC_ |
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| Active variables |
| | | A , B , BLOCK_CYCLIC_2D , CSRC_ , CTXT_ , DESCA , DESCB , DESCIP , DLEN_ , DTYPE_ , IA , IAROW , IB , IBROW , ICOFFA , ICTXT , IDUM1 , IDUM2 , INDXG2P , INFO , IPIV , IROFFA , IROFFB , JA , JB , LLD_ , LSAME , M_ , MB_ , MYCOL , MYROW , N , N_ , NB_ , NOTRAN , NPCOL , NPROW , NRHS , NUMROC , ONE , RSRC_ , TRANS |
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| Accessed arrays [ array name : associated index ] |
| |  DESCA | : CTXT_ , M_ , M_ , MB_ , MB_ , MB_ , MB_ , MB_ , MB_ , NB_ , NB_ , NB_ , RSRC_ , RSRC_ , RSRC_ |
| | DESCB | : CTXT_ , MB_ , MB_ , MB_ , RSRC_ |
| | DESCIP | : DLEN_ |
| | IDUM1 | : 1 , 1 , 1 , 1 |
| | IDUM2 | : 1 , 1 |
| | LSAME | : TRANS, 'C' , TRANS, 'N' , TRANS, 'T' , TRANS, 'T' |
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| Conditional statements [ statement : associated predicate ] |
| | if | : ( NPROW.EQ. - 1 ) , ( INFO.EQ.0 ) , ( (.NOT.NOTRAN .AND. .NOT.LSAME( TRANS , 'T' ) .AND. .NOT. ) , ( IROFFA.NE.0 ) , ( ICOFFA.NE.0 ) , ( (DESCA( MB_ ).NE.DESCA( NB_ ) ) ) , ( IROFFB.NE.0 .OR. IBROW.NE.IAROW ) , ( (DESCB( MB_ ).NE.DESCA( NB_ ) ) ) , ( (ICTXT.NE.DESCB( CTXT_ ) ) ) , ( NOTRAN ) , ( (LSAME( TRANS , 'T' ) ) ) , ( INFO.NE.0 ) , ( possible ) , ( N.EQ.0 .OR. NRHS.EQ.0 ) , ( NOTRAN ) |
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| List of variables |
BLOCK_CYCLIC_2D
CSRC_
CTXT_
DESCIP( DLEN_ )
DLEN_
DTYPE_
IA
| IAROW
IB
IBROW
ICOFFA
ICTXT
IDUM1( 1 )
IDUM2( 1 )
INDXG2P
| INFO
IROFFA
IROFFB
JA
JB
LLD_
LSAME
M_
| MB_
MYCOL
MYROW
N
N_
NB_
NOTRAN
NPCOL
| NPROW
NRHS
NUMROC
ONE
RSRC_
TRANS | | close
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BLOCK_CYCLIC_2D
CSRC_
CTXT_
DESCIP( DLEN_ )
DLEN_
DTYPE_
IA
IAROW
IB
IBROW
ICOFFA
ICTXT
IDUM1( 1 )
IDUM2( 1 )
INDXG2P
INFO
IROFFA
IROFFB
JA
JB
LLD_
LSAME
M_
MB_
MYCOL
MYROW
N
N_
NB_
NOTRAN
NPCOL
NPROW
NRHS
NUMROC
ONE
RSRC_
TRANS
376
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