--- rpl/lapack/lapack/zlangb.f	2018/05/29 07:18:26	1.17
+++ rpl/lapack/lapack/zlangb.f	2020/05/21 21:46:07	1.18
@@ -130,6 +130,7 @@
 *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
 *     December 2016
 *
+      IMPLICIT NONE
 *     .. Scalar Arguments ..
       CHARACTER          NORM
       INTEGER            KL, KU, LDAB, N
@@ -147,14 +148,17 @@
 *     ..
 *     .. Local Scalars ..
       INTEGER            I, J, K, L
-      DOUBLE PRECISION   SCALE, SUM, VALUE, TEMP
+      DOUBLE PRECISION   SUM, VALUE, TEMP
+*     ..
+*     .. 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
@@ -207,15 +211,22 @@
       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.
 *
-         SCALE = ZERO
-         SUM = ONE
+         SSQ( 1 ) = ZERO
+         SSQ( 2 ) = ONE
          DO 90 J = 1, N
             L = MAX( 1, J-KU )
             K = KU + 1 - J + L
-            CALL ZLASSQ( MIN( N, J+KL )-L+1, AB( K, J ), 1, SCALE, SUM )
+            COLSSQ( 1 ) = ZERO
+            COLSSQ( 2 ) = ONE
+            CALL ZLASSQ( MIN( N, J+KL )-L+1, AB( K, J ), 1,
+     $                   COLSSQ( 1 ), COLSSQ( 2 ) )
+            CALL DCOMBSSQ( SSQ, COLSSQ )
    90    CONTINUE
-         VALUE = SCALE*SQRT( SUM )
+         VALUE = SSQ( 1 )*SQRT( SSQ( 2 ) )
       END IF
 *
       ZLANGB = VALUE