Fix the left-looking variant of geqrf following #638 thanks to @angsch.

Author: weslleyspereira

SRC/VARIANTS/qr/LL/cgeqrf.f

@@ -81,7 +81,8 @@
 C>          LWORK is INTEGER
 C> \endverbatim
 C> \verbatim
-C>          The dimension of the array WORK. The dimension can be divided into three parts.
+C>          The dimension of the array WORK. LWORK >= 1 if MIN(M,N) = 0,
+C>          otherwise the dimension can be divided into three parts.
 C> \endverbatim
 C> \verbatim
 C>          1) The part for the triangular factor T. If the very last T is not bigger
@@ -212,7 +213,13 @@ SUBROUTINE CGEQRF ( M, N, A, LDA, TAU, WORK, LWORK, INFO )
       LLWORK = MAX (MAX((N-M)*K, (N-M)*NB), MAX(K*NB, NB*NB))
       LLWORK = SCEIL(REAL(LLWORK)/REAL(NB))
 
-      IF ( NT.GT.NB ) THEN
+      IF( K.EQ.0 ) THEN
+
+         LBWORK = 0
+         LWKOPT = 1
+         WORK( 1 ) = LWKOPT
+
+      ELSE IF ( NT.GT.NB ) THEN
 
           LBWORK = K-NT
 *
@@ -239,8 +246,9 @@ SUBROUTINE CGEQRF ( M, N, A, LDA, TAU, WORK, LWORK, INFO )
          INFO = -2
       ELSE IF( LDA.LT.MAX( 1, M ) ) THEN
          INFO = -4
-      ELSE IF( LWORK.LT.MAX( 1, N ) .AND. .NOT.LQUERY ) THEN
-         INFO = -7
+      ELSE IF ( .NOT.LQUERY ) THEN
+         IF( LWORK.LE.0 .OR. ( M.GT.0 .AND. LWORK.LT.MAX( 1, N ) ) )
+     $      INFO = -7
       END IF
       IF( INFO.NE.0 ) THEN
          CALL XERBLA( 'CGEQRF', -INFO )
@@ -252,7 +260,6 @@ SUBROUTINE CGEQRF ( M, N, A, LDA, TAU, WORK, LWORK, INFO )
 *     Quick return if possible
 *
       IF( K.EQ.0 ) THEN
-         WORK( 1 ) = 1
          RETURN
       END IF
 *

SRC/VARIANTS/qr/LL/dgeqrf.f

@@ -81,7 +81,8 @@
 C>          LWORK is INTEGER
 C> \endverbatim
 C> \verbatim
-C>          The dimension of the array WORK. The dimension can be divided into three parts.
+C>          The dimension of the array WORK. LWORK >= 1 if MIN(M,N) = 0,
+C>          otherwise the dimension can be divided into three parts.
 C> \endverbatim
 C> \verbatim
 C>          1) The part for the triangular factor T. If the very last T is not bigger
@@ -212,7 +213,13 @@ SUBROUTINE DGEQRF ( M, N, A, LDA, TAU, WORK, LWORK, INFO )
       LLWORK = MAX (MAX((N-M)*K, (N-M)*NB), MAX(K*NB, NB*NB))
       LLWORK = SCEIL(REAL(LLWORK)/REAL(NB))
 
-      IF ( NT.GT.NB ) THEN
+      IF( K.EQ.0 ) THEN
+
+         LBWORK = 0
+         LWKOPT = 1
+         WORK( 1 ) = LWKOPT
+
+      ELSE IF ( NT.GT.NB ) THEN
 
           LBWORK = K-NT
 *
@@ -239,8 +246,9 @@ SUBROUTINE DGEQRF ( M, N, A, LDA, TAU, WORK, LWORK, INFO )
          INFO = -2
       ELSE IF( LDA.LT.MAX( 1, M ) ) THEN
          INFO = -4
-      ELSE IF( LWORK.LT.MAX( 1, N ) .AND. .NOT.LQUERY ) THEN
-         INFO = -7
+      ELSE IF ( .NOT.LQUERY ) THEN
+         IF( LWORK.LE.0 .OR. ( M.GT.0 .AND. LWORK.LT.MAX( 1, N ) ) )
+     $      INFO = -7
       END IF
       IF( INFO.NE.0 ) THEN
          CALL XERBLA( 'DGEQRF', -INFO )
@@ -252,7 +260,6 @@ SUBROUTINE DGEQRF ( M, N, A, LDA, TAU, WORK, LWORK, INFO )
 *     Quick return if possible
 *
       IF( K.EQ.0 ) THEN
-         WORK( 1 ) = 1
          RETURN
       END IF
 *

SRC/VARIANTS/qr/LL/sgeqrf.f

@@ -81,7 +81,8 @@
 C>          LWORK is INTEGER
 C> \endverbatim
 C> \verbatim
-C>          The dimension of the array WORK. The dimension can be divided into three parts.
+C>          The dimension of the array WORK. LWORK >= 1 if MIN(M,N) = 0,
+C>          otherwise the dimension can be divided into three parts.
 C> \endverbatim
 C> \verbatim
 C>          1) The part for the triangular factor T. If the very last T is not bigger
@@ -212,7 +213,13 @@ SUBROUTINE SGEQRF ( M, N, A, LDA, TAU, WORK, LWORK, INFO )
       LLWORK = MAX (MAX((N-M)*K, (N-M)*NB), MAX(K*NB, NB*NB))
       LLWORK = SCEIL(REAL(LLWORK)/REAL(NB))
 
-      IF ( NT.GT.NB ) THEN
+      IF( K.EQ.0 ) THEN
+
+         LBWORK = 0
+         LWKOPT = 1
+         WORK( 1 ) = LWKOPT
+
+      ELSE IF ( NT.GT.NB ) THEN
 
           LBWORK = K-NT
 *
@@ -239,8 +246,9 @@ SUBROUTINE SGEQRF ( M, N, A, LDA, TAU, WORK, LWORK, INFO )
          INFO = -2
       ELSE IF( LDA.LT.MAX( 1, M ) ) THEN
          INFO = -4
-      ELSE IF( LWORK.LT.MAX( 1, N ) .AND. .NOT.LQUERY ) THEN
-         INFO = -7
+      ELSE IF ( .NOT.LQUERY ) THEN
+         IF( LWORK.LE.0 .OR. ( M.GT.0 .AND. LWORK.LT.MAX( 1, N ) ) )
+     $      INFO = -7
       END IF
       IF( INFO.NE.0 ) THEN
          CALL XERBLA( 'SGEQRF', -INFO )
@@ -252,7 +260,6 @@ SUBROUTINE SGEQRF ( M, N, A, LDA, TAU, WORK, LWORK, INFO )
 *     Quick return if possible
 *
       IF( K.EQ.0 ) THEN
-         WORK( 1 ) = 1
          RETURN
       END IF
 *

SRC/VARIANTS/qr/LL/zgeqrf.f

@@ -81,7 +81,8 @@
 C>          LWORK is INTEGER
 C> \endverbatim
 C> \verbatim
-C>          The dimension of the array WORK. The dimension can be divided into three parts.
+C>          The dimension of the array WORK. LWORK >= 1 if MIN(M,N) = 0,
+C>          otherwise the dimension can be divided into three parts.
 C> \endverbatim
 C> \verbatim
 C>          1) The part for the triangular factor T. If the very last T is not bigger
@@ -212,7 +213,13 @@ SUBROUTINE ZGEQRF ( M, N, A, LDA, TAU, WORK, LWORK, INFO )
       LLWORK = MAX (MAX((N-M)*K, (N-M)*NB), MAX(K*NB, NB*NB))
       LLWORK = SCEIL(REAL(LLWORK)/REAL(NB))
 
-      IF ( NT.GT.NB ) THEN
+      IF( K.EQ.0 ) THEN
+
+         LBWORK = 0
+         LWKOPT = 1
+         WORK( 1 ) = LWKOPT
+
+      ELSE IF ( NT.GT.NB ) THEN
 
           LBWORK = K-NT
 *
@@ -239,8 +246,9 @@ SUBROUTINE ZGEQRF ( M, N, A, LDA, TAU, WORK, LWORK, INFO )
          INFO = -2
       ELSE IF( LDA.LT.MAX( 1, M ) ) THEN
          INFO = -4
-      ELSE IF( LWORK.LT.MAX( 1, N ) .AND. .NOT.LQUERY ) THEN
-         INFO = -7
+      ELSE IF ( .NOT.LQUERY ) THEN
+         IF( LWORK.LE.0 .OR. ( M.GT.0 .AND. LWORK.LT.MAX( 1, N ) ) )
+     $      INFO = -7
       END IF
       IF( INFO.NE.0 ) THEN
          CALL XERBLA( 'ZGEQRF', -INFO )
@@ -252,7 +260,6 @@ SUBROUTINE ZGEQRF ( M, N, A, LDA, TAU, WORK, LWORK, INFO )
 *     Quick return if possible
 *
       IF( K.EQ.0 ) THEN
-         WORK( 1 ) = 1
          RETURN
       END IF
 *