dlagv2.c

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        *snr = 0.;
/*<          CALL DROT( 2, A( 1, 1 ), LDA, A( 2, 1 ), LDA, CSL, SNL ) >*/
        drot_(&c__2, &a[a_dim1 + 1], lda, &a[a_dim1 + 2], lda, csl, snl);
/*<          CALL DROT( 2, B( 1, 1 ), LDB, B( 2, 1 ), LDB, CSL, SNL ) >*/
        drot_(&c__2, &b[b_dim1 + 1], ldb, &b[b_dim1 + 2], ldb, csl, snl);
/*<          A( 2, 1 ) = ZERO >*/
        a[a_dim1 + 2] = 0.;
/*<          B( 1, 1 ) = ZERO >*/
        b[b_dim1 + 1] = 0.;
/*<          B( 2, 1 ) = ZERO >*/
        b[b_dim1 + 2] = 0.;

/*<       ELSE IF( ABS( B( 2, 2 ) ).LE.ULP ) THEN >*/
    } else if ((d__1 = b[(b_dim1 << 1) + 2], abs(d__1)) <= ulp) {
/*<          CALL DLARTG( A( 2, 2 ), A( 2, 1 ), CSR, SNR, T ) >*/
        dlartg_(&a[(a_dim1 << 1) + 2], &a[a_dim1 + 2], csr, snr, &t);
/*<          SNR = -SNR >*/
        *snr = -(*snr);
/*<          CALL DROT( 2, A( 1, 1 ), 1, A( 1, 2 ), 1, CSR, SNR ) >*/
        drot_(&c__2, &a[a_dim1 + 1], &c__1, &a[(a_dim1 << 1) + 1], &c__1, csr,
                 snr);
/*<          CALL DROT( 2, B( 1, 1 ), 1, B( 1, 2 ), 1, CSR, SNR ) >*/
        drot_(&c__2, &b[b_dim1 + 1], &c__1, &b[(b_dim1 << 1) + 1], &c__1, csr,
                 snr);
/*<          CSL = ONE >*/
        *csl = 1.;
/*<          SNL = ZERO >*/
        *snl = 0.;
/*<          A( 2, 1 ) = ZERO >*/
        a[a_dim1 + 2] = 0.;
/*<          B( 2, 1 ) = ZERO >*/
        b[b_dim1 + 2] = 0.;
/*<          B( 2, 2 ) = ZERO >*/
        b[(b_dim1 << 1) + 2] = 0.;

/*<       ELSE >*/
    } else {

/*        B is nonsingular, first compute the eigenvalues of (A,B) */

/*<    >*/
        dlag2_(&a[a_offset], lda, &b[b_offset], ldb, &safmin, &scale1, &
                scale2, &wr1, &wr2, &wi);

/*<          IF( WI.EQ.ZERO ) THEN >*/
        if (wi == 0.) {

/*           two real eigenvalues, compute s*A-w*B */

/*<             H1 = SCALE1*A( 1, 1 ) - WR1*B( 1, 1 ) >*/
            h1 = scale1 * a[a_dim1 + 1] - wr1 * b[b_dim1 + 1];
/*<             H2 = SCALE1*A( 1, 2 ) - WR1*B( 1, 2 ) >*/
            h2 = scale1 * a[(a_dim1 << 1) + 1] - wr1 * b[(b_dim1 << 1) + 1];
/*<             H3 = SCALE1*A( 2, 2 ) - WR1*B( 2, 2 ) >*/
            h3 = scale1 * a[(a_dim1 << 1) + 2] - wr1 * b[(b_dim1 << 1) + 2];

/*<             RR = DLAPY2( H1, H2 ) >*/
            rr = dlapy2_(&h1, &h2);
/*<             QQ = DLAPY2( SCALE1*A( 2, 1 ), H3 ) >*/
            d__1 = scale1 * a[a_dim1 + 2];
            qq = dlapy2_(&d__1, &h3);

/*<             IF( RR.GT.QQ ) THEN >*/
            if (rr > qq) {

/*              find right rotation matrix to zero 1,1 element of */
/*              (sA - wB) */

/*<                CALL DLARTG( H2, H1, CSR, SNR, T ) >*/
                dlartg_(&h2, &h1, csr, snr, &t);

/*<             ELSE >*/
            } else {

/*              find right rotation matrix to zero 2,1 element of */
/*              (sA - wB) */

/*<                CALL DLARTG( H3, SCALE1*A( 2, 1 ), CSR, SNR, T ) >*/
                d__1 = scale1 * a[a_dim1 + 2];
                dlartg_(&h3, &d__1, csr, snr, &t);

/*<             END IF >*/
            }

/*<             SNR = -SNR >*/
            *snr = -(*snr);
/*<             CALL DROT( 2, A( 1, 1 ), 1, A( 1, 2 ), 1, CSR, SNR ) >*/
            drot_(&c__2, &a[a_dim1 + 1], &c__1, &a[(a_dim1 << 1) + 1], &c__1, 
                    csr, snr);
/*<             CALL DROT( 2, B( 1, 1 ), 1, B( 1, 2 ), 1, CSR, SNR ) >*/
            drot_(&c__2, &b[b_dim1 + 1], &c__1, &b[(b_dim1 << 1) + 1], &c__1, 
                    csr, snr);

/*           compute inf norms of A and B */

/*<    >*/
/* Computing MAX */
            d__5 = (d__1 = a[a_dim1 + 1], abs(d__1)) + (d__2 = a[(a_dim1 << 1)
                     + 1], abs(d__2)), d__6 = (d__3 = a[a_dim1 + 2], abs(d__3)
                    ) + (d__4 = a[(a_dim1 << 1) + 2], abs(d__4));
            h1 = max(d__5,d__6);
/*<    >*/
/* Computing MAX */
            d__5 = (d__1 = b[b_dim1 + 1], abs(d__1)) + (d__2 = b[(b_dim1 << 1)
                     + 1], abs(d__2)), d__6 = (d__3 = b[b_dim1 + 2], abs(d__3)
                    ) + (d__4 = b[(b_dim1 << 1) + 2], abs(d__4));
            h2 = max(d__5,d__6);

/*<             IF( ( SCALE1*H1 ).GE.ABS( WR1 )*H2 ) THEN >*/
            if (scale1 * h1 >= abs(wr1) * h2) {

/*              find left rotation matrix Q to zero out B(2,1) */

/*<                CALL DLARTG( B( 1, 1 ), B( 2, 1 ), CSL, SNL, R ) >*/
                dlartg_(&b[b_dim1 + 1], &b[b_dim1 + 2], csl, snl, &r__);

/*<             ELSE >*/
            } else {

/*              find left rotation matrix Q to zero out A(2,1) */

/*<                CALL DLARTG( A( 1, 1 ), A( 2, 1 ), CSL, SNL, R ) >*/
                dlartg_(&a[a_dim1 + 1], &a[a_dim1 + 2], csl, snl, &r__);

/*<             END IF >*/
            }

/*<             CALL DROT( 2, A( 1, 1 ), LDA, A( 2, 1 ), LDA, CSL, SNL ) >*/
            drot_(&c__2, &a[a_dim1 + 1], lda, &a[a_dim1 + 2], lda, csl, snl);
/*<             CALL DROT( 2, B( 1, 1 ), LDB, B( 2, 1 ), LDB, CSL, SNL ) >*/
            drot_(&c__2, &b[b_dim1 + 1], ldb, &b[b_dim1 + 2], ldb, csl, snl);

/*<             A( 2, 1 ) = ZERO >*/
            a[a_dim1 + 2] = 0.;
/*<             B( 2, 1 ) = ZERO >*/
            b[b_dim1 + 2] = 0.;

/*<          ELSE >*/
        } else {

/*           a pair of complex conjugate eigenvalues */
/*           first compute the SVD of the matrix B */

/*<    >*/
            dlasv2_(&b[b_dim1 + 1], &b[(b_dim1 << 1) + 1], &b[(b_dim1 << 1) + 
                    2], &r__, &t, snr, csr, snl, csl);

/*           Form (A,B) := Q(A,B)Z' where Q is left rotation matrix and */
/*           Z is right rotation matrix computed from DLASV2 */

/*<             CALL DROT( 2, A( 1, 1 ), LDA, A( 2, 1 ), LDA, CSL, SNL ) >*/
            drot_(&c__2, &a[a_dim1 + 1], lda, &a[a_dim1 + 2], lda, csl, snl);
/*<             CALL DROT( 2, B( 1, 1 ), LDB, B( 2, 1 ), LDB, CSL, SNL ) >*/
            drot_(&c__2, &b[b_dim1 + 1], ldb, &b[b_dim1 + 2], ldb, csl, snl);
/*<             CALL DROT( 2, A( 1, 1 ), 1, A( 1, 2 ), 1, CSR, SNR ) >*/
            drot_(&c__2, &a[a_dim1 + 1], &c__1, &a[(a_dim1 << 1) + 1], &c__1, 
                    csr, snr);
/*<             CALL DROT( 2, B( 1, 1 ), 1, B( 1, 2 ), 1, CSR, SNR ) >*/
            drot_(&c__2, &b[b_dim1 + 1], &c__1, &b[(b_dim1 << 1) + 1], &c__1, 
                    csr, snr);

/*<             B( 2, 1 ) = ZERO >*/
            b[b_dim1 + 2] = 0.;
/*<             B( 1, 2 ) = ZERO >*/
            b[(b_dim1 << 1) + 1] = 0.;

/*<          END IF >*/
        }

/*<       END IF >*/
    }

/*     Unscaling */

/*<       A( 1, 1 ) = ANORM*A( 1, 1 ) >*/
    a[a_dim1 + 1] = anorm * a[a_dim1 + 1];
/*<       A( 2, 1 ) = ANORM*A( 2, 1 ) >*/
    a[a_dim1 + 2] = anorm * a[a_dim1 + 2];
/*<       A( 1, 2 ) = ANORM*A( 1, 2 ) >*/
    a[(a_dim1 << 1) + 1] = anorm * a[(a_dim1 << 1) + 1];
/*<       A( 2, 2 ) = ANORM*A( 2, 2 ) >*/
    a[(a_dim1 << 1) + 2] = anorm * a[(a_dim1 << 1) + 2];
/*<       B( 1, 1 ) = BNORM*B( 1, 1 ) >*/
    b[b_dim1 + 1] = bnorm * b[b_dim1 + 1];
/*<       B( 2, 1 ) = BNORM*B( 2, 1 ) >*/
    b[b_dim1 + 2] = bnorm * b[b_dim1 + 2];
/*<       B( 1, 2 ) = BNORM*B( 1, 2 ) >*/
    b[(b_dim1 << 1) + 1] = bnorm * b[(b_dim1 << 1) + 1];
/*<       B( 2, 2 ) = BNORM*B( 2, 2 ) >*/
    b[(b_dim1 << 1) + 2] = bnorm * b[(b_dim1 << 1) + 2];

/*<       IF( WI.EQ.ZERO ) THEN >*/
    if (wi == 0.) {
/*<          ALPHAR( 1 ) = A( 1, 1 ) >*/
        alphar[1] = a[a_dim1 + 1];
/*<          ALPHAR( 2 ) = A( 2, 2 ) >*/
        alphar[2] = a[(a_dim1 << 1) + 2];
/*<          ALPHAI( 1 ) = ZERO >*/
        alphai[1] = 0.;
/*<          ALPHAI( 2 ) = ZERO >*/
        alphai[2] = 0.;
/*<          BETA( 1 ) = B( 1, 1 ) >*/
        beta[1] = b[b_dim1 + 1];
/*<          BETA( 2 ) = B( 2, 2 ) >*/
        beta[2] = b[(b_dim1 << 1) + 2];
/*<       ELSE >*/
    } else {
/*<          ALPHAR( 1 ) = ANORM*WR1 / SCALE1 / BNORM >*/
        alphar[1] = anorm * wr1 / scale1 / bnorm;
/*<          ALPHAI( 1 ) = ANORM*WI / SCALE1 / BNORM >*/
        alphai[1] = anorm * wi / scale1 / bnorm;
/*<          ALPHAR( 2 ) = ALPHAR( 1 ) >*/
        alphar[2] = alphar[1];
/*<          ALPHAI( 2 ) = -ALPHAI( 1 ) >*/
        alphai[2] = -alphai[1];
/*<          BETA( 1 ) = ONE >*/
        beta[1] = 1.;
/*<          BETA( 2 ) = ONE >*/
        beta[2] = 1.;
/*<       END IF >*/
    }

/*<    10 CONTINUE >*/
/* L10: */

/*<       RETURN >*/
    return 0;

/*     End of DLAGV2 */

/*<       END >*/
} /* dlagv2_ */

#ifdef __cplusplus
        }
#endif