Remove manipulation of lamda due to missing guard digit

Author: angsch

SRC/dlaed3.f

@@ -44,12 +44,6 @@
 *> being combined by the matrix of eigenvectors of the K-by-K system
 *> which is solved here.
 *>
-*> This code makes very mild assumptions about floating point
-*> arithmetic. It will work on machines with a guard digit in
-*> add/subtract, or on those binary machines without guard digits
-*> which subtract like the Cray X-MP, Cray Y-MP, Cray C-90, or Cray-2.
-*> It could conceivably fail on hexadecimal or decimal machines
-*> without guard digits, but we know of none.
 *> \endverbatim
 *
 *  Arguments:
@@ -104,14 +98,12 @@
 *>          RHO >= 0 required.
 *> \endverbatim
 *>
-*> \param[in,out] DLAMDA
+*> \param[in] DLAMDA
 *> \verbatim
 *>          DLAMDA is DOUBLE PRECISION array, dimension (K)
 *>          The first K elements of this array contain the old roots
 *>          of the deflated updating problem.  These are the poles
-*>          of the secular equation. May be changed on output by
-*>          having lowest order bit set to zero on Cray X-MP, Cray Y-MP,
-*>          Cray-2, or Cray C-90, as described above.
+*>          of the secular equation.
 *> \endverbatim
 *>
 *> \param[in] Q2
@@ -240,26 +232,6 @@ SUBROUTINE DLAED3( K, N, N1, D, Q, LDQ, RHO, DLAMDA, Q2, INDX,
       IF( K.EQ.0 )
      $   RETURN
 *
-*     Modify values DLAMDA(i) to make sure all DLAMDA(i)-DLAMDA(j) can
-*     be computed with high relative accuracy (barring over/underflow).
-*     This is a problem on machines without a guard digit in
-*     add/subtract (Cray XMP, Cray YMP, Cray C 90 and Cray 2).
-*     The following code replaces DLAMDA(I) by 2*DLAMDA(I)-DLAMDA(I),
-*     which on any of these machines zeros out the bottommost
-*     bit of DLAMDA(I) if it is 1; this makes the subsequent
-*     subtractions DLAMDA(I)-DLAMDA(J) unproblematic when cancellation
-*     occurs. On binary machines with a guard digit (almost all
-*     machines) it does not change DLAMDA(I) at all. On hexadecimal
-*     and decimal machines with a guard digit, it slightly
-*     changes the bottommost bits of DLAMDA(I). It does not account
-*     for hexadecimal or decimal machines without guard digits
-*     (we know of none). We use a subroutine call to compute
-*     2*DLAMBDA(I) to prevent optimizing compilers from eliminating
-*     this code.
-*
-      DO 10 I = 1, K
-         DLAMDA( I ) = DLAMC3( DLAMDA( I ), DLAMDA( I ) ) - DLAMDA( I )
-   10 CONTINUE
 *
       DO 20 J = 1, K
          CALL DLAED4( K, J, DLAMDA, W, Q( 1, J ), RHO, D( J ), INFO )

SRC/slaed3.f

@@ -44,12 +44,6 @@
 *> being combined by the matrix of eigenvectors of the K-by-K system
 *> which is solved here.
 *>
-*> This code makes very mild assumptions about floating point
-*> arithmetic. It will work on machines with a guard digit in
-*> add/subtract, or on those binary machines without guard digits
-*> which subtract like the Cray X-MP, Cray Y-MP, Cray C-90, or Cray-2.
-*> It could conceivably fail on hexadecimal or decimal machines
-*> without guard digits, but we know of none.
 *> \endverbatim
 *
 *  Arguments:
@@ -104,14 +98,12 @@
 *>          RHO >= 0 required.
 *> \endverbatim
 *>
-*> \param[in,out] DLAMDA
+*> \param[in] DLAMDA
 *> \verbatim
 *>          DLAMDA is REAL array, dimension (K)
 *>          The first K elements of this array contain the old roots
 *>          of the deflated updating problem.  These are the poles
-*>          of the secular equation. May be changed on output by
-*>          having lowest order bit set to zero on Cray X-MP, Cray Y-MP,
-*>          Cray-2, or Cray C-90, as described above.
+*>          of the secular equation.
 *> \endverbatim
 *>
 *> \param[in] Q2
@@ -239,27 +231,6 @@ SUBROUTINE SLAED3( K, N, N1, D, Q, LDQ, RHO, DLAMDA, Q2, INDX,
 *
       IF( K.EQ.0 )
      $   RETURN
-*
-*     Modify values DLAMDA(i) to make sure all DLAMDA(i)-DLAMDA(j) can
-*     be computed with high relative accuracy (barring over/underflow).
-*     This is a problem on machines without a guard digit in
-*     add/subtract (Cray XMP, Cray YMP, Cray C 90 and Cray 2).
-*     The following code replaces DLAMDA(I) by 2*DLAMDA(I)-DLAMDA(I),
-*     which on any of these machines zeros out the bottommost
-*     bit of DLAMDA(I) if it is 1; this makes the subsequent
-*     subtractions DLAMDA(I)-DLAMDA(J) unproblematic when cancellation
-*     occurs. On binary machines with a guard digit (almost all
-*     machines) it does not change DLAMDA(I) at all. On hexadecimal
-*     and decimal machines with a guard digit, it slightly
-*     changes the bottommost bits of DLAMDA(I). It does not account
-*     for hexadecimal or decimal machines without guard digits
-*     (we know of none). We use a subroutine call to compute
-*     2*DLAMBDA(I) to prevent optimizing compilers from eliminating
-*     this code.
-*
-      DO 10 I = 1, K
-         DLAMDA( I ) = SLAMC3( DLAMDA( I ), DLAMDA( I ) ) - DLAMDA( I )
-   10 CONTINUE
 *
       DO 20 J = 1, K
          CALL SLAED4( K, J, DLAMDA, W, Q( 1, J ), RHO, D( J ), INFO )