Handle corner cases of LWORK (Reference-LAPACK PR 942)

lapack-netlib/SRC/cgemqr.f

@@ -111,16 +111,17 @@
 *>
 *> \param[out] WORK
 *> \verbatim
-*>         (workspace) COMPLEX array, dimension (MAX(1,LWORK))
+*>          (workspace) COMPLEX array, dimension (MAX(1,LWORK))
+*>          On exit, if INFO = 0, WORK(1) returns the minimal LWORK.
 *> \endverbatim
 *>
 *> \param[in] LWORK
 *> \verbatim
 *>          LWORK is INTEGER
-*>          The dimension of the array WORK.
+*>          The dimension of the array WORK. LWORK >= 1.
 *>          If LWORK = -1, then a workspace query is assumed. The routine
 *>          only calculates the size of the WORK array, returns this
-*>          value as WORK(1), and no error message related to WORK 
+*>          value as WORK(1), and no error message related to WORK
 *>          is issued by XERBLA.
 *> \endverbatim
 *>
@@ -144,7 +145,7 @@
 *>
 *> \verbatim
 *>
-*> These details are particular for this LAPACK implementation. Users should not 
+*> These details are particular for this LAPACK implementation. Users should not
 *> take them for granted. These details may change in the future, and are not likely
 *> true for another LAPACK implementation. These details are relevant if one wants
 *> to try to understand the code. They are not part of the interface.
@@ -166,6 +167,8 @@
 *>
 *> \endverbatim
 *>
+*> \ingroup gemqr
+*>
 *  =====================================================================
       SUBROUTINE CGEMQR( SIDE, TRANS, M, N, K, A, LDA, T, TSIZE,
      $                   C, LDC, WORK, LWORK, INFO )
@@ -187,11 +190,12 @@
 *     ..
 *     .. Local Scalars ..
       LOGICAL            LEFT, RIGHT, TRAN, NOTRAN, LQUERY
-      INTEGER            MB, NB, LW, NBLCKS, MN
+      INTEGER            MB, NB, LW, NBLCKS, MN, MINMNK, LWMIN
 *     ..
 *     .. External Functions ..
       LOGICAL            LSAME
-      EXTERNAL           LSAME
+      REAL               SROUNDUP_LWORK
+      EXTERNAL           LSAME, SROUNDUP_LWORK
 *     ..
 *     .. External Subroutines ..
       EXTERNAL           CGEMQRT, CLAMTSQR, XERBLA
@@ -203,7 +207,7 @@
 *
 *     Test the input arguments
 *
-      LQUERY  = LWORK.EQ.-1
+      LQUERY  = ( LWORK.EQ.-1 )
       NOTRAN  = LSAME( TRANS, 'N' )
       TRAN    = LSAME( TRANS, 'C' )
       LEFT    = LSAME( SIDE, 'L' )
@@ -218,6 +222,13 @@
         LW = MB * NB
         MN = N
       END IF
+*
+      MINMNK = MIN( M, N, K )
+      IF( MINMNK.EQ.0 ) THEN
+         LWMIN = 1
+      ELSE
+         LWMIN = MAX( 1, LW )
+      END IF
 *
       IF( ( MB.GT.K ) .AND. ( MN.GT.K ) ) THEN
         IF( MOD( MN - K, MB - K ).EQ.0 ) THEN
@@ -251,7 +262,7 @@
       END IF
 *
       IF( INFO.EQ.0 ) THEN
-        WORK( 1 ) = LW
+        WORK( 1 ) = SROUNDUP_LWORK( LWMIN )
       END IF
 *
       IF( INFO.NE.0 ) THEN
@@ -263,7 +274,7 @@
 *
 *     Quick return if possible
 *
-      IF( MIN( M, N, K ).EQ.0 ) THEN
+      IF( MINMNK.EQ.0 ) THEN
         RETURN
       END IF
 *
@@ -276,7 +287,7 @@
      $                 NB, C, LDC, WORK, LWORK, INFO )
       END IF
 *
-      WORK( 1 ) = LW
+      WORK( 1 ) = SROUNDUP_LWORK( LWMIN )
 *
       RETURN
 *