127 SUBROUTINE ssytrs2( UPLO, N, NRHS, A, LDA, IPIV, B, LDB,
137 INTEGER INFO, LDA, LDB, N, NRHS
141 REAL A( lda, * ), B( ldb, * ), WORK( * )
148 parameter( one = 1.0e+0 )
152 INTEGER I, IINFO, J, K, KP
153 REAL AK, AKM1, AKM1K, BK, BKM1, DENOM
168 upper = lsame( uplo,
'U' )
169 IF( .NOT.upper .AND. .NOT.lsame( uplo,
'L' ) )
THEN
171 ELSE IF( n.LT.0 )
THEN
173 ELSE IF( nrhs.LT.0 )
THEN
175 ELSE IF( lda.LT.max( 1, n ) )
THEN
177 ELSE IF( ldb.LT.max( 1, n ) )
THEN
181 CALL xerbla(
'SSYTRS2', -info )
187 IF( n.EQ.0 .OR. nrhs.EQ.0 )
192 CALL ssyconv( uplo,
'C', n, a, lda, ipiv, work, iinfo )
200 DO WHILE ( k .GE. 1 )
201 IF( ipiv( k ).GT.0 )
THEN
206 $
CALL sswap( nrhs, b( k, 1 ), ldb, b( kp, 1 ), ldb )
212 IF( kp.EQ.-ipiv( k-1 ) )
213 $
CALL sswap( nrhs, b( k-1, 1 ), ldb, b( kp, 1 ), ldb )
220 CALL strsm(
'L',
'U',
'N',
'U',n,nrhs,one,a,lda,b,ldb)
225 DO WHILE ( i .GE. 1 )
226 IF( ipiv(i) .GT. 0 )
THEN
227 CALL sscal( nrhs, one / a( i, i ), b( i, 1 ), ldb )
228 ELSEIF ( i .GT. 1)
THEN
229 IF ( ipiv(i-1) .EQ. ipiv(i) )
THEN
231 akm1 = a( i-1, i-1 ) / akm1k
232 ak = a( i, i ) / akm1k
233 denom = akm1*ak - one
235 bkm1 = b( i-1, j ) / akm1k
236 bk = b( i, j ) / akm1k
237 b( i-1, j ) = ( ak*bkm1-bk ) / denom
238 b( i, j ) = ( akm1*bk-bkm1 ) / denom
248 CALL strsm(
'L',
'U',
'T',
'U',n,nrhs,one,a,lda,b,ldb)
253 DO WHILE ( k .LE. n )
254 IF( ipiv( k ).GT.0 )
THEN
259 $
CALL sswap( nrhs, b( k, 1 ), ldb, b( kp, 1 ), ldb )
265 IF( k .LT. n .AND. kp.EQ.-ipiv( k+1 ) )
266 $
CALL sswap( nrhs, b( k, 1 ), ldb, b( kp, 1 ), ldb )
277 DO WHILE ( k .LE. n )
278 IF( ipiv( k ).GT.0 )
THEN
283 $
CALL sswap( nrhs, b( k, 1 ), ldb, b( kp, 1 ), ldb )
289 IF( kp.EQ.-ipiv( k ) )
290 $
CALL sswap( nrhs, b( k+1, 1 ), ldb, b( kp, 1 ), ldb )
297 CALL strsm(
'L',
'L',
'N',
'U',n,nrhs,one,a,lda,b,ldb)
302 DO WHILE ( i .LE. n )
303 IF( ipiv(i) .GT. 0 )
THEN
304 CALL sscal( nrhs, one / a( i, i ), b( i, 1 ), ldb )
307 akm1 = a( i, i ) / akm1k
308 ak = a( i+1, i+1 ) / akm1k
309 denom = akm1*ak - one
311 bkm1 = b( i, j ) / akm1k
312 bk = b( i+1, j ) / akm1k
313 b( i, j ) = ( ak*bkm1-bk ) / denom
314 b( i+1, j ) = ( akm1*bk-bkm1 ) / denom
323 CALL strsm(
'L',
'L',
'T',
'U',n,nrhs,one,a,lda,b,ldb)
328 DO WHILE ( k .GE. 1 )
329 IF( ipiv( k ).GT.0 )
THEN
334 $
CALL sswap( nrhs, b( k, 1 ), ldb, b( kp, 1 ), ldb )
340 IF( k.GT.1 .AND. kp.EQ.-ipiv( k-1 ) )
341 $
CALL sswap( nrhs, b( k, 1 ), ldb, b( kp, 1 ), ldb )
350 CALL ssyconv( uplo,
'R', n, a, lda, ipiv, work, iinfo )
subroutine sswap(N, SX, INCX, SY, INCY)
SSWAP
subroutine xerbla(SRNAME, INFO)
XERBLA
subroutine ssyconv(UPLO, WAY, N, A, LDA, IPIV, WORK, INFO)
SSYCONV
subroutine ssytrs2(UPLO, N, NRHS, A, LDA, IPIV, B, LDB, WORK, INFO)
SSYTRS2
subroutine strsm(SIDE, UPLO, TRANSA, DIAG, M, N, ALPHA, A, LDA, B, LDB)
STRSM
subroutine sscal(N, SA, SX, INCX)
SSCAL