xGEQP3 changes July 2024

Author: frjohnst

SRC/cgeqp3.f

@@ -249,6 +249,11 @@ SUBROUTINE CGEQP3( M, N, A, LDA, JPVT, TAU, WORK, LWORK, RWORK,
             JPVT( J ) = J
          END IF
    10 CONTINUE
+*
+*     Quick return if possible.
+*
+      IF( M.EQ.0 ) RETURN
+*
       NFXD = NFXD - 1
 *
 *     Factorize fixed columns

SRC/dgeqp3.f

@@ -240,6 +240,11 @@ SUBROUTINE DGEQP3( M, N, A, LDA, JPVT, TAU, WORK, LWORK, INFO )
             JPVT( J ) = J
          END IF
    10 CONTINUE
+*
+*     Quick return if possible
+*
+      IF( M.EQ.0 ) RETURN
+*
       NFXD = NFXD - 1
 *
 *     Factorize fixed columns
@@ -290,14 +295,14 @@ SUBROUTINE DGEQP3( M, N, A, LDA, JPVT, TAU, WORK, LWORK, INFO )
 *
 *              Determine if workspace is large enough for blocked code.
 *
-               MINWS = 2*SN + ( SN+1 )*NB
+               MINWS = 2*N + ( SN+1 )*NB
                IWS = MAX( IWS, MINWS )
                IF( LWORK.LT.MINWS ) THEN
 *
 *                 Not enough workspace to use optimal NB: Reduce NB and
 *                 determine the minimum value of NB.
 *
-                  NB = ( LWORK-2*SN ) / ( SN+1 )
+                  NB = ( LWORK-2*N ) / ( SN+1 )
                   NBMIN = MAX( 2, ILAENV( INBMIN, 'DGEQRF', ' ', SM,
      $                         SN,
      $                    -1, -1 ) )

SRC/sgeqp3.f

@@ -237,6 +237,11 @@ SUBROUTINE SGEQP3( M, N, A, LDA, JPVT, TAU, WORK, LWORK, INFO )
             JPVT( J ) = J
          END IF
    10 CONTINUE
+*
+*     Quick return if possible.
+*
+      IF( M.EQ.0 ) RETURN
+*
       NFXD = NFXD - 1
 *
 *     Factorize fixed columns
@@ -287,14 +292,14 @@ SUBROUTINE SGEQP3( M, N, A, LDA, JPVT, TAU, WORK, LWORK, INFO )
 *
 *              Determine if workspace is large enough for blocked code.
 *
-               MINWS = 2*SN + ( SN+1 )*NB
+               MINWS = 2*N + ( SN+1 )*NB
                IWS = MAX( IWS, MINWS )
                IF( LWORK.LT.MINWS ) THEN
 *
 *                 Not enough workspace to use optimal NB: Reduce NB and
 *                 determine the minimum value of NB.
 *
-                  NB = ( LWORK-2*SN ) / ( SN+1 )
+                  NB = ( LWORK-2*N ) / ( SN+1 )
                   NBMIN = MAX( 2, ILAENV( INBMIN, 'SGEQRF', ' ', SM,
      $                         SN,
      $                    -1, -1 ) )

SRC/zgeqp3.f

@@ -249,6 +249,11 @@ SUBROUTINE ZGEQP3( M, N, A, LDA, JPVT, TAU, WORK, LWORK, RWORK,
             JPVT( J ) = J
          END IF
    10 CONTINUE
+*
+*     Quick return if possible.
+*
+      IF( M.EQ.0 ) RETURN
+*
       NFXD = NFXD - 1
 *
 *     Factorize fixed columns