--- rpl/lapack/lapack/zlansb.f	2018/05/29 07:18:27	1.17
+++ rpl/lapack/lapack/zlansb.f	2020/05/21 21:46:08	1.18
@@ -135,6 +135,7 @@
 *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
 *     December 2016
 *
+      IMPLICIT NONE
 *     .. Scalar Arguments ..
       CHARACTER          NORM, UPLO
       INTEGER            K, LDAB, N
@@ -152,14 +153,17 @@
 *     ..
 *     .. Local Scalars ..
       INTEGER            I, J, L
-      DOUBLE PRECISION   ABSA, SCALE, SUM, VALUE
+      DOUBLE PRECISION   ABSA, SUM, VALUE
+*     ..
+*     .. Local Arrays ..
+      DOUBLE PRECISION   SSQ( 2 ), COLSSQ( 2 )
 *     ..
 *     .. External Functions ..
       LOGICAL            LSAME, DISNAN
       EXTERNAL           LSAME, DISNAN
 *     ..
 *     .. External Subroutines ..
-      EXTERNAL           ZLASSQ
+      EXTERNAL           ZLASSQ, DCOMBSSQ
 *     ..
 *     .. Intrinsic Functions ..
       INTRINSIC          ABS, MAX, MIN, SQRT
@@ -227,29 +231,47 @@
       ELSE IF( ( LSAME( NORM, 'F' ) ) .OR. ( LSAME( NORM, 'E' ) ) ) THEN
 *
 *        Find normF(A).
+*        SSQ(1) is scale
+*        SSQ(2) is sum-of-squares
+*        For better accuracy, sum each column separately.
+*
+         SSQ( 1 ) = ZERO
+         SSQ( 2 ) = ONE
+*
+*        Sum off-diagonals
 *
-         SCALE = ZERO
-         SUM = ONE
          IF( K.GT.0 ) THEN
             IF( LSAME( UPLO, 'U' ) ) THEN
                DO 110 J = 2, N
+                  COLSSQ( 1 ) = ZERO
+                  COLSSQ( 2 ) = ONE
                   CALL ZLASSQ( MIN( J-1, K ), AB( MAX( K+2-J, 1 ), J ),
-     $                         1, SCALE, SUM )
+     $                         1, COLSSQ( 1 ), COLSSQ( 2 ) )
+                  CALL DCOMBSSQ( SSQ, COLSSQ )
   110          CONTINUE
                L = K + 1
             ELSE
                DO 120 J = 1, N - 1
-                  CALL ZLASSQ( MIN( N-J, K ), AB( 2, J ), 1, SCALE,
-     $                         SUM )
+                  COLSSQ( 1 ) = ZERO
+                  COLSSQ( 2 ) = ONE
+                  CALL ZLASSQ( MIN( N-J, K ), AB( 2, J ), 1,
+     $                         COLSSQ( 1 ), COLSSQ( 2 ) )
+                  CALL DCOMBSSQ( SSQ, COLSSQ )
   120          CONTINUE
                L = 1
             END IF
-            SUM = 2*SUM
+            SSQ( 2 ) = 2*SSQ( 2 )
          ELSE
             L = 1
          END IF
-         CALL ZLASSQ( N, AB( L, 1 ), LDAB, SCALE, SUM )
-         VALUE = SCALE*SQRT( SUM )
+*
+*        Sum diagonal
+*
+         COLSSQ( 1 ) = ZERO
+         COLSSQ( 2 ) = ONE
+         CALL ZLASSQ( N, AB( L, 1 ), LDAB, COLSSQ( 1 ), COLSSQ( 2 ) )
+         CALL DCOMBSSQ( SSQ, COLSSQ )
+         VALUE = SSQ( 1 )*SQRT( SSQ( 2 ) )
       END IF
 *
       ZLANSB = VALUE