changed matrix norm to 'M' (max) from 'I' (inf) for scaling of input matrix

and added check for zero norm in xSTERF (the xSTEQR already had this check)
this fixes the issue reported in bug0036

diff --git a/SRC/dsteqr.f b/SRC/dsteqr.f
index a0ec5cdb523644fd51281a1c93a9b3352ed23623..17a17468a9c8589e89ede6cbfacb8df8ad6ef9f4 100644 (file)
--- a/SRC/dsteqr.f
+++ b/SRC/dsteqr.f
@@ -195,7 +195,7 @@
 *
 *     Scale submatrix in rows and columns L to LEND
 *
-      ANORM = DLANST( 'I', LEND-L+1, D( L ), E( L ) )
+      ANORM = DLANST( 'M', LEND-L+1, D( L ), E( L ) )
       ISCALE = 0
       IF( ANORM.EQ.ZERO )
      $   GO TO 10

diff --git a/SRC/dsterf.f b/SRC/dsterf.f
index 4f2a9bcf677c6cebf892db0797c11525042ed49b..74f289b645044bcd71c0f35e8b1b7623c5698a25 100644 (file)
--- a/SRC/dsterf.f
+++ b/SRC/dsterf.f
@@ -54,7 +54,7 @@
      $                   NMAXIT
       DOUBLE PRECISION   ALPHA, ANORM, BB, C, EPS, EPS2, GAMMA, OLDC,
      $                   OLDGAM, P, R, RT1, RT2, RTE, S, SAFMAX, SAFMIN,
-     $                   SIGMA, SSFMAX, SSFMIN
+     $                   SIGMA, SSFMAX, SSFMIN, RMAX
 *     ..
 *     .. External Functions ..
       DOUBLE PRECISION   DLAMCH, DLANST, DLAPY2
@@ -90,6 +90,7 @@
       SAFMAX = ONE / SAFMIN
       SSFMAX = SQRT( SAFMAX ) / THREE
       SSFMIN = SQRT( SAFMIN ) / EPS2
+      RMAX = DLAMCH( 'O' )
 *
 *     Compute the eigenvalues of the tridiagonal matrix.
 *
@@ -128,9 +129,11 @@
 *
 *     Scale submatrix in rows and columns L to LEND
 *
-      ANORM = DLANST( 'I', LEND-L+1, D( L ), E( L ) )
+      ANORM = DLANST( 'M', LEND-L+1, D( L ), E( L ) )
       ISCALE = 0
-      IF( ANORM.GT.SSFMAX ) THEN
+      IF( ANORM.EQ.ZERO )
+     $   GO TO 10      
+      IF( (ANORM.GT.SSFMAX) ) THEN
          ISCALE = 1
          CALL DLASCL( 'G', 0, 0, ANORM, SSFMAX, LEND-L+1, 1, D( L ), N,
      $                INFO )

diff --git a/SRC/ssteqr.f b/SRC/ssteqr.f
index 952fb5021252a6482c46b7873cc3f99eca2532ff..835c82fc1aea42cf4111a8b3dc40a2af348fd9c7 100644 (file)
--- a/SRC/ssteqr.f
+++ b/SRC/ssteqr.f
@@ -195,7 +195,7 @@
 *
 *     Scale submatrix in rows and columns L to LEND
 *
-      ANORM = SLANST( 'I', LEND-L+1, D( L ), E( L ) )
+      ANORM = SLANST( 'M', LEND-L+1, D( L ), E( L ) )
       ISCALE = 0
       IF( ANORM.EQ.ZERO )
      $   GO TO 10

diff --git a/SRC/ssterf.f b/SRC/ssterf.f
index a51c379da47498512563002ecd3ec02cc7341253..b9110dd61a10db3b54548a1bf00ad0dc2be597c8 100644 (file)
--- a/SRC/ssterf.f
+++ b/SRC/ssterf.f
@@ -128,8 +128,10 @@
 *
 *     Scale submatrix in rows and columns L to LEND
 *
-      ANORM = SLANST( 'I', LEND-L+1, D( L ), E( L ) )
+      ANORM = SLANST( 'M', LEND-L+1, D( L ), E( L ) )
       ISCALE = 0
+      IF( ANORM.EQ.ZERO )
+     $   GO TO 10      
       IF( ANORM.GT.SSFMAX ) THEN
          ISCALE = 1
          CALL SLASCL( 'G', 0, 0, ANORM, SSFMAX, LEND-L+1, 1, D( L ), N,