Merge pull request #1290 from jschueller/issue938

slarfgp/dlarfgp: avoid overflow when computing 1/ALPHA
2026-07-13 03:07:53 -06:00
parent 552873f0a9 72b151245e
commit 76bb13e396
2 changed files with 12 additions and 2 deletions
@@ -220,7 +220,12 @@
 *
 *           This is the general case.
 *
-            CALL DSCAL( N-1, ONE / ALPHA, X, INCX )
+            IF( ABS( ALPHA ).LT.SMLNUM ) THEN
+               CALL DSCAL( N-1, ONE / SMLNUM, X, INCX )
+               CALL DSCAL( N-1, SMLNUM / ALPHA, X, INCX )
+            ELSE
+               CALL DSCAL( N-1, ONE / ALPHA, X, INCX )
+            END IF
 *
         END IF
 *
@@ -220,7 +220,12 @@
 *
 *           This is the general case.
 *
-            CALL SSCAL( N-1, ONE / ALPHA, X, INCX )
+            IF( ABS( ALPHA ).LT.SMLNUM ) THEN
+               CALL SSCAL( N-1, ONE / SMLNUM, X, INCX )
+               CALL SSCAL( N-1, SMLNUM / ALPHA, X, INCX )
+            ELSE
+               CALL SSCAL( N-1, ONE / ALPHA, X, INCX )
+            END IF
 *
         END IF
 *