Return INFO=1 in S/DLASQ1 instead of returning via XERBLA when SIGMX is NaN (Reference-LAPACK PR 1387)

lapack-netlib/SRC/dlasq1.c

@@ -226,8 +226,6 @@ typedef struct Namelist Namelist;
 */
 
 
-
-
 /* Table of constant values */
 
 static integer c__1 = 1;
@@ -241,7 +239,6 @@ static integer c__0 = 0;
 /* Online html documentation available at */
 /*            http://www.netlib.org/lapack/explore-html/ */
 
-/* > \htmlonly */
 /* > Download DLASQ1 + dependencies */
 /* > <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/dlasq1.
 f"> */
@@ -252,7 +249,6 @@ f"> */
 /* > <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dlasq1.
 f"> */
 /* > [TXT]</a> */
-/* > \endhtmlonly */
 
 /*  Definition: */
 /*  =========== */
@@ -318,7 +314,8 @@ f"> */
 /* >        = 0: successful exit */
 /* >        < 0: if INFO = -i, the i-th argument had an illegal value */
 /* >        > 0: the algorithm failed */
-/* >             = 1, a split was marked by a positive value in E */
+/* >             = 1, a split was marked by a positive value in E, or */
+/* >                  the input contains a NaN */
 /* >             = 2, current block of Z not diagonalized after 100*N */
 /* >                  iterations (in inner while loop)  On exit D and E */
 /* >                  represent a matrix with the same singular values */
@@ -336,9 +333,7 @@ f"> */
 /* > \author Univ. of Colorado Denver */
 /* > \author NAG Ltd. */
 
-/* > \date December 2016 */
-
-/* > \ingroup auxOTHERcomputational */
+/* > \ingroup lasq1 */
 
 /*  ===================================================================== */
 /* Subroutine */ void dlasq1_(integer *n, doublereal *d__, doublereal *e, 
@@ -349,9 +344,10 @@ f"> */
     doublereal d__1, d__2, d__3;
 
     /* Local variables */
+    integer i__;
+    doublereal eps;
     extern /* Subroutine */ void dlas2_(doublereal *, doublereal *, doublereal 
 	    *, doublereal *, doublereal *);
-    integer i__;
     doublereal scale;
     integer iinfo;
     doublereal sigmn;
@@ -363,17 +359,15 @@ f"> */
     extern /* Subroutine */ void dlascl_(char *, integer *, integer *, 
 	    doublereal *, doublereal *, integer *, integer *, doublereal *, 
 	    integer *, integer *);
+    extern logical disnan_(doublereal *);
     doublereal safmin;
-    extern /* Subroutine */ void xerbla_(char *, integer *, ftnlen);
-    extern void dlasrt_(
+    extern /* Subroutine */ void xerbla_(char *, integer *, ftnlen), dlasrt_(
 	    char *, integer *, doublereal *, integer *);
-    doublereal eps;
 
 
-/*  -- LAPACK computational routine (version 3.7.0) -- */
+/*  -- LAPACK computational routine -- */
 /*  -- LAPACK is a software package provided by Univ. of Tennessee,    -- */
 /*  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- */
-/*     December 2016 */
 
 
 /*  ===================================================================== */
@@ -431,6 +425,14 @@ f"> */
 /* L20: */
     }
 
+/*     A NaN in D or E can make SIGMX a NaN, which DLASCL would reject */
+/*     by stopping in XERBLA; report it through INFO instead. */
+
+    if (disnan_(&sigmx)) {
+	*info = 1;
+	return;
+    }
+
 /*     Copy D and E into WORK (in the Z format) and scale (squaring the */
 /*     input data makes scaling by a power of the radix pointless). */
 

lapack-netlib/SRC/dlasq1.f

@@ -5,15 +5,13 @@
 * Online html documentation available at
 *            http://www.netlib.org/lapack/explore-html/
 *
-*> \htmlonly
 *> Download DLASQ1 + dependencies
 *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/dlasq1.f">
 *> [TGZ]</a>
 *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/dlasq1.f">
 *> [ZIP]</a>
 *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dlasq1.f">
 *> [TXT]</a>
-*> \endhtmlonly
 *
 *  Definition:
 *  ===========
@@ -83,7 +81,8 @@
 *>        = 0: successful exit
 *>        < 0: if INFO = -i, the i-th argument had an illegal value
 *>        > 0: the algorithm failed
-*>             = 1, a split was marked by a positive value in E
+*>             = 1, a split was marked by a positive value in E, or
+*>                  the input contains a NaN
 *>             = 2, current block of Z not diagonalized after 100*N
 *>                  iterations (in inner while loop)  On exit D and E
 *>                  represent a matrix with the same singular values
@@ -101,10 +100,11 @@
 *> \author Univ. of Colorado Denver
 *> \author NAG Ltd.
 *
-*> \ingroup auxOTHERcomputational
+*> \ingroup lasq1
 *
 *  =====================================================================
       SUBROUTINE DLASQ1( N, D, E, WORK, INFO )
+      IMPLICIT NONE
 *
 *  -- LAPACK computational routine --
 *  -- LAPACK is a software package provided by Univ. of Tennessee,    --
@@ -128,11 +128,13 @@ SUBROUTINE DLASQ1( N, D, E, WORK, INFO )
       DOUBLE PRECISION   EPS, SCALE, SAFMIN, SIGMN, SIGMX
 *     ..
 *     .. External Subroutines ..
-      EXTERNAL           DCOPY, DLAS2, DLASCL, DLASQ2, DLASRT, XERBLA
+      EXTERNAL           DCOPY, DLAS2, DLASCL, DLASQ2, DLASRT,
+     $                   XERBLA
 *     ..
 *     .. External Functions ..
       DOUBLE PRECISION   DLAMCH
-      EXTERNAL           DLAMCH
+      LOGICAL            DISNAN
+      EXTERNAL           DISNAN, DLAMCH
 *     ..
 *     .. Intrinsic Functions ..
       INTRINSIC          ABS, MAX, SQRT
@@ -176,6 +178,14 @@ SUBROUTINE DLASQ1( N, D, E, WORK, INFO )
          SIGMX = MAX( SIGMX, D( I ) )
    20 CONTINUE
 *
+*     A NaN in D or E can make SIGMX a NaN, which DLASCL would reject
+*     by stopping in XERBLA; report it through INFO instead.
+*
+      IF( DISNAN( SIGMX ) ) THEN
+         INFO = 1
+         RETURN
+      END IF
+*
 *     Copy D and E into WORK (in the Z format) and scale (squaring the
 *     input data makes scaling by a power of the radix pointless).
 *