zlar1v.f.html

来自「famous linear algebra library (LAPACK) p」· HTML 代码 · 共 396 行 · 第 1/2 页

         WORK( INDS+B1-1 ) = LLD( B1-1 )
      END IF

<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Compute the stationary transform (using the differential form)
</span><span class="comment">*</span><span class="comment">     until the index R2.
</span><span class="comment">*</span><span class="comment">
</span>      SAWNAN1 = .FALSE.
      NEG1 = 0
      S = WORK( INDS+B1-1 ) - LAMBDA
      DO 50 I = B1, R1 - 1
         DPLUS = D( I ) + S
         WORK( INDLPL+I ) = LD( I ) / DPLUS
         IF(DPLUS.LT.ZERO) NEG1 = NEG1 + 1
         WORK( INDS+I ) = S*WORK( INDLPL+I )*L( I )
         S = WORK( INDS+I ) - LAMBDA
 50   CONTINUE
      SAWNAN1 = <a name="DISNAN.197"></a><a href="disnan.f.html#DISNAN.1">DISNAN</a>( S )
      IF( SAWNAN1 ) GOTO 60
      DO 51 I = R1, R2 - 1
         DPLUS = D( I ) + S
         WORK( INDLPL+I ) = LD( I ) / DPLUS
         WORK( INDS+I ) = S*WORK( INDLPL+I )*L( I )
         S = WORK( INDS+I ) - LAMBDA
 51   CONTINUE
      SAWNAN1 = <a name="DISNAN.205"></a><a href="disnan.f.html#DISNAN.1">DISNAN</a>( S )
<span class="comment">*</span><span class="comment">
</span> 60   CONTINUE
      IF( SAWNAN1 ) THEN
<span class="comment">*</span><span class="comment">        Runs a slower version of the above loop if a NaN is detected
</span>         NEG1 = 0
         S = WORK( INDS+B1-1 ) - LAMBDA
         DO 70 I = B1, R1 - 1
            DPLUS = D( I ) + S
            IF(ABS(DPLUS).LT.PIVMIN) DPLUS = -PIVMIN
            WORK( INDLPL+I ) = LD( I ) / DPLUS
            IF(DPLUS.LT.ZERO) NEG1 = NEG1 + 1
            WORK( INDS+I ) = S*WORK( INDLPL+I )*L( I )
            IF( WORK( INDLPL+I ).EQ.ZERO )
     $                      WORK( INDS+I ) = LLD( I )
            S = WORK( INDS+I ) - LAMBDA
 70      CONTINUE
         DO 71 I = R1, R2 - 1
            DPLUS = D( I ) + S
            IF(ABS(DPLUS).LT.PIVMIN) DPLUS = -PIVMIN
            WORK( INDLPL+I ) = LD( I ) / DPLUS
            WORK( INDS+I ) = S*WORK( INDLPL+I )*L( I )
            IF( WORK( INDLPL+I ).EQ.ZERO )
     $                      WORK( INDS+I ) = LLD( I )
            S = WORK( INDS+I ) - LAMBDA
 71      CONTINUE
      END IF
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Compute the progressive transform (using the differential form)
</span><span class="comment">*</span><span class="comment">     until the index R1
</span><span class="comment">*</span><span class="comment">
</span>      SAWNAN2 = .FALSE.
      NEG2 = 0
      WORK( INDP+BN-1 ) = D( BN ) - LAMBDA
      DO 80 I = BN - 1, R1, -1
         DMINUS = LLD( I ) + WORK( INDP+I )
         TMP = D( I ) / DMINUS
         IF(DMINUS.LT.ZERO) NEG2 = NEG2 + 1
         WORK( INDUMN+I ) = L( I )*TMP
         WORK( INDP+I-1 ) = WORK( INDP+I )*TMP - LAMBDA
 80   CONTINUE
      TMP = WORK( INDP+R1-1 )
      SAWNAN2 = <a name="DISNAN.247"></a><a href="disnan.f.html#DISNAN.1">DISNAN</a>( TMP )

      IF( SAWNAN2 ) THEN
<span class="comment">*</span><span class="comment">        Runs a slower version of the above loop if a NaN is detected
</span>         NEG2 = 0
         DO 100 I = BN-1, R1, -1
            DMINUS = LLD( I ) + WORK( INDP+I )
            IF(ABS(DMINUS).LT.PIVMIN) DMINUS = -PIVMIN
            TMP = D( I ) / DMINUS
            IF(DMINUS.LT.ZERO) NEG2 = NEG2 + 1
            WORK( INDUMN+I ) = L( I )*TMP
            WORK( INDP+I-1 ) = WORK( INDP+I )*TMP - LAMBDA
            IF( TMP.EQ.ZERO )
     $          WORK( INDP+I-1 ) = D( I ) - LAMBDA
 100     CONTINUE
      END IF
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Find the index (from R1 to R2) of the largest (in magnitude)
</span><span class="comment">*</span><span class="comment">     diagonal element of the inverse
</span><span class="comment">*</span><span class="comment">
</span>      MINGMA = WORK( INDS+R1-1 ) + WORK( INDP+R1-1 )
      IF( MINGMA.LT.ZERO ) NEG1 = NEG1 + 1
      IF( WANTNC ) THEN
         NEGCNT = NEG1 + NEG2
      ELSE
         NEGCNT = -1
      ENDIF
      IF( ABS(MINGMA).EQ.ZERO )
     $   MINGMA = EPS*WORK( INDS+R1-1 )
      R = R1
      DO 110 I = R1, R2 - 1
         TMP = WORK( INDS+I ) + WORK( INDP+I )
         IF( TMP.EQ.ZERO )
     $      TMP = EPS*WORK( INDS+I )
         IF( ABS( TMP ).LE.ABS( MINGMA ) ) THEN
            MINGMA = TMP
            R = I + 1
         END IF
 110  CONTINUE
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Compute the FP vector: solve N^T v = e_r
</span><span class="comment">*</span><span class="comment">
</span>      ISUPPZ( 1 ) = B1
      ISUPPZ( 2 ) = BN
      Z( R ) = CONE
      ZTZ = ONE
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Compute the FP vector upwards from R
</span><span class="comment">*</span><span class="comment">
</span>      IF( .NOT.SAWNAN1 .AND. .NOT.SAWNAN2 ) THEN
         DO 210 I = R-1, B1, -1
            Z( I ) = -( WORK( INDLPL+I )*Z( I+1 ) )
            IF( (ABS(Z(I))+ABS(Z(I+1)))* ABS(LD(I)).LT.GAPTOL )
     $           THEN
               Z( I ) = ZERO
               ISUPPZ( 1 ) = I + 1
               GOTO 220
            ENDIF
            ZTZ = ZTZ + DBLE( Z( I )*Z( I ) )
 210     CONTINUE
 220     CONTINUE
      ELSE
<span class="comment">*</span><span class="comment">        Run slower loop if NaN occurred.
</span>         DO 230 I = R - 1, B1, -1
            IF( Z( I+1 ).EQ.ZERO ) THEN
               Z( I ) = -( LD( I+1 ) / LD( I ) )*Z( I+2 )
            ELSE
               Z( I ) = -( WORK( INDLPL+I )*Z( I+1 ) )
            END IF
            IF( (ABS(Z(I))+ABS(Z(I+1)))* ABS(LD(I)).LT.GAPTOL )
     $           THEN
               Z( I ) = ZERO
               ISUPPZ( 1 ) = I + 1
               GO TO 240
            END IF
            ZTZ = ZTZ + DBLE( Z( I )*Z( I ) )
 230     CONTINUE
 240     CONTINUE
      ENDIF

<span class="comment">*</span><span class="comment">     Compute the FP vector downwards from R in blocks of size BLKSIZ
</span>      IF( .NOT.SAWNAN1 .AND. .NOT.SAWNAN2 ) THEN
         DO 250 I = R, BN-1
            Z( I+1 ) = -( WORK( INDUMN+I )*Z( I ) )
            IF( (ABS(Z(I))+ABS(Z(I+1)))* ABS(LD(I)).LT.GAPTOL )
     $         THEN
               Z( I+1 ) = ZERO
               ISUPPZ( 2 ) = I
               GO TO 260
            END IF
            ZTZ = ZTZ + DBLE( Z( I+1 )*Z( I+1 ) )
 250     CONTINUE
 260     CONTINUE
      ELSE
<span class="comment">*</span><span class="comment">        Run slower loop if NaN occurred.
</span>         DO 270 I = R, BN - 1
            IF( Z( I ).EQ.ZERO ) THEN
               Z( I+1 ) = -( LD( I-1 ) / LD( I ) )*Z( I-1 )
            ELSE
               Z( I+1 ) = -( WORK( INDUMN+I )*Z( I ) )
            END IF
            IF( (ABS(Z(I))+ABS(Z(I+1)))* ABS(LD(I)).LT.GAPTOL )
     $           THEN
               Z( I+1 ) = ZERO
               ISUPPZ( 2 ) = I
               GO TO 280
            END IF
            ZTZ = ZTZ + DBLE( Z( I+1 )*Z( I+1 ) )
 270     CONTINUE
 280     CONTINUE
      END IF
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     Compute quantities for convergence test
</span><span class="comment">*</span><span class="comment">
</span>      TMP = ONE / ZTZ
      NRMINV = SQRT( TMP )
      RESID = ABS( MINGMA )*NRMINV
      RQCORR = MINGMA*TMP
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">
</span>      RETURN
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment">     End of <a name="ZLAR1V.369"></a><a href="zlar1v.f.html#ZLAR1V.1">ZLAR1V</a>
</span><span class="comment">*</span><span class="comment">
</span>      END

</pre>

 </body>
</html>