zgeev function

Implementation

void zgeev(
  final String JOBVL,
  final String JOBVR,
  final int N,
  final Matrix<Complex> A_,
  final int LDA,
  final Array<Complex> W_,
  final Matrix<Complex> VL_,
  final int LDVL,
  final Matrix<Complex> VR_,
  final int LDVR,
  final Array<Complex> WORK_,
  final int LWORK,
  final Array<double> RWORK_,
  final Box<int> INFO,
) {
  final A = A_.having(ld: LDA);
  final VL = VL_.having(ld: LDVL);
  final VR = VR_.having(ld: LDVR);
  final W = W_.having();
  final WORK = WORK_.having();
  final RWORK = RWORK_.having();

  const ZERO = 0.0, ONE = 1.0;
  bool LQUERY, SCALEA, WANTVL, WANTVR;
  String SIDE = '';
  int HSWORK,
      I,
      IBAL,
      IRWORK = 0,
      ITAU,
      IWRK,
      K,
      LWORK_TREVC,
      MAXWRK = 0,
      MINWRK = 0;
  double ANRM, BIGNUM, CSCALE = 0, EPS, SCL, SMLNUM;
  Complex TMP;
  final SELECT = Array<bool>(1);
  final DUM = Array<double>(1);
  final IERR = Box(0), IHI = Box(0), ILO = Box(0), NOUT = Box(0);

  // Test the input arguments

  INFO.value = 0;
  LQUERY = (LWORK == -1);
  WANTVL = lsame(JOBVL, 'V');
  WANTVR = lsame(JOBVR, 'V');
  if (!WANTVL && !lsame(JOBVL, 'N')) {
    INFO.value = -1;
  } else if (!WANTVR && !lsame(JOBVR, 'N')) {
    INFO.value = -2;
  } else if (N < 0) {
    INFO.value = -3;
  } else if (LDA < max(1, N)) {
    INFO.value = -5;
  } else if (LDVL < 1 || (WANTVL && LDVL < N)) {
    INFO.value = -8;
  } else if (LDVR < 1 || (WANTVR && LDVR < N)) {
    INFO.value = -10;
  }

  // Compute workspace
  //  (Note: Comments in the code beginning "Workspace:" describe the
  //   minimal amount of workspace needed at that point in the code,
  //   as well as the preferred amount for good performance.
  //   CWorkspace refers to complex workspace, and RWorkspace to real
  //   workspace. NB refers to the optimal block size for the
  //   immediately following subroutine, as returned by ILAENV.
  //   HSWORK refers to the workspace preferred by ZHSEQR, as
  //   calculated below. HSWORK is computed assuming ILO=1 and IHI=N,
  //   the worst case.)

  if (INFO.value == 0) {
    if (N == 0) {
      MINWRK = 1;
      MAXWRK = 1;
    } else {
      MAXWRK = N + N * ilaenv(1, 'ZGEHRD', ' ', N, 1, N, 0);
      MINWRK = 2 * N;
      if (WANTVL) {
        MAXWRK =
            max(MAXWRK, N + (N - 1) * ilaenv(1, 'ZUNGHR', ' ', N, 1, N, -1));
        ztrevc3('L', 'B', SELECT, N, A, LDA, VL, LDVL, VR, LDVR, N, NOUT, WORK,
            -1, RWORK, -1, IERR);
        LWORK_TREVC = WORK[1].toInt();
        MAXWRK = max(MAXWRK, N + LWORK_TREVC);
        zhseqr('S', 'V', N, 1, N, A, LDA, W, VL, LDVL, WORK, -1, INFO);
      } else if (WANTVR) {
        MAXWRK =
            max(MAXWRK, N + (N - 1) * ilaenv(1, 'ZUNGHR', ' ', N, 1, N, -1));
        ztrevc3('R', 'B', SELECT, N, A, LDA, VL, LDVL, VR, LDVR, N, NOUT, WORK,
            -1, RWORK, -1, IERR);
        LWORK_TREVC = WORK[1].toInt();
        MAXWRK = max(MAXWRK, N + LWORK_TREVC);
        zhseqr('S', 'V', N, 1, N, A, LDA, W, VR, LDVR, WORK, -1, INFO);
      } else {
        zhseqr('E', 'N', N, 1, N, A, LDA, W, VR, LDVR, WORK, -1, INFO);
      }
      HSWORK = WORK[1].toInt();
      MAXWRK = max(MAXWRK, max(HSWORK, MINWRK));
    }
    WORK[1] = MAXWRK.toComplex();

    if (LWORK < MINWRK && !LQUERY) {
      INFO.value = -12;
    }
  }

  if (INFO.value != 0) {
    xerbla('ZGEEV', -INFO.value);
    return;
  } else if (LQUERY) {
    return;
  }

  // Quick return if possible

  if (N == 0) return;

  // Get machine constants

  EPS = dlamch('P');
  SMLNUM = dlamch('S');
  BIGNUM = ONE / SMLNUM;
  SMLNUM = sqrt(SMLNUM) / EPS;
  BIGNUM = ONE / SMLNUM;

  // Scale A if max element outside range [SMLNUM,BIGNUM]

  ANRM = zlange('M', N, N, A, LDA, DUM);
  SCALEA = false;
  if (ANRM > ZERO && ANRM < SMLNUM) {
    SCALEA = true;
    CSCALE = SMLNUM;
  } else if (ANRM > BIGNUM) {
    SCALEA = true;
    CSCALE = BIGNUM;
  }
  if (SCALEA) zlascl('G', 0, 0, ANRM, CSCALE, N, N, A, LDA, IERR);

  // Balance the matrix
  // (CWorkspace: none)
  // (RWorkspace: need N)

  IBAL = 1;
  zgebal('B', N, A, LDA, ILO, IHI, RWORK(IBAL), IERR);

  // Reduce to upper Hessenberg form
  // (CWorkspace: need 2*N, prefer N+N*NB)
  // (RWorkspace: none)

  ITAU = 1;
  IWRK = ITAU + N;
  zgehrd(N, ILO.value, IHI.value, A, LDA, WORK(ITAU), WORK(IWRK),
      LWORK - IWRK + 1, IERR);

  if (WANTVL) {
    // Want left eigenvectors
    // Copy Householder vectors to VL

    SIDE = 'L';
    zlacpy('L', N, N, A, LDA, VL, LDVL);

    // Generate unitary matrix in VL
    // (CWorkspace: need 2*N-1, prefer N+(N-1)*NB)
    // (RWorkspace: none)

    zunghr(N, ILO.value, IHI.value, VL, LDVL, WORK(ITAU), WORK(IWRK),
        LWORK - IWRK + 1, IERR);

    // Perform QR iteration, accumulating Schur vectors in VL
    // (CWorkspace: need 1, prefer HSWORK (see comments) )
    // (RWorkspace: none)

    IWRK = ITAU;
    zhseqr('S', 'V', N, ILO.value, IHI.value, A, LDA, W, VL, LDVL, WORK(IWRK),
        LWORK - IWRK + 1, INFO);

    if (WANTVR) {
      // Want left and right eigenvectors
      // Copy Schur vectors to VR

      SIDE = 'B';
      zlacpy('F', N, N, VL, LDVL, VR, LDVR);
    }
  } else if (WANTVR) {
    // Want right eigenvectors
    // Copy Householder vectors to VR

    SIDE = 'R';
    zlacpy('L', N, N, A, LDA, VR, LDVR);

    // Generate unitary matrix in VR
    // (CWorkspace: need 2*N-1, prefer N+(N-1)*NB)
    // (RWorkspace: none)

    zunghr(N, ILO.value, IHI.value, VR, LDVR, WORK(ITAU), WORK(IWRK),
        LWORK - IWRK + 1, IERR);

    // Perform QR iteration, accumulating Schur vectors in VR
    // (CWorkspace: need 1, prefer HSWORK (see comments) )
    // (RWorkspace: none)

    IWRK = ITAU;
    zhseqr('S', 'V', N, ILO.value, IHI.value, A, LDA, W, VR, LDVR, WORK(IWRK),
        LWORK - IWRK + 1, INFO);
  } else {
    // Compute eigenvalues only
    // (CWorkspace: need 1, prefer HSWORK (see comments) )
    // (RWorkspace: none)

    IWRK = ITAU;
    zhseqr('E', 'N', N, ILO.value, IHI.value, A, LDA, W, VR, LDVR, WORK(IWRK),
        LWORK - IWRK + 1, INFO);
  }

  // If INFO != 0 from ZHSEQR, then quit

  if (INFO.value == 0) {
    if (WANTVL || WANTVR) {
      // Compute left and/or right eigenvectors
      // (CWorkspace: need 2*N, prefer N + 2*N*NB)
      // (RWorkspace: need 2*N)

      IRWORK = IBAL + N;
      ztrevc3(SIDE, 'B', SELECT, N, A, LDA, VL, LDVL, VR, LDVR, N, NOUT,
          WORK(IWRK), LWORK - IWRK + 1, RWORK(IRWORK), N, IERR);
    }

    if (WANTVL) {
      // Undo balancing of left eigenvectors
      // (CWorkspace: none)
      // (RWorkspace: need N)

      zgebak('B', 'L', N, ILO.value, IHI.value, RWORK(IBAL), N, VL, LDVL, IERR);

      // Normalize left eigenvectors and make largest component real

      for (I = 1; I <= N; I++) {
        SCL = ONE / dznrm2(N, VL(1, I).asArray(), 1);
        zdscal(N, SCL, VL(1, I).asArray(), 1);
        for (K = 1; K <= N; K++) {
          RWORK[IRWORK + K - 1] =
              pow(VL[K][I].real, 2).toDouble() + pow(VL[K][I].imaginary, 2);
        }
        K = idamax(N, RWORK(IRWORK), 1);
        TMP = VL[K][I].conjugate() / sqrt(RWORK[IRWORK + K - 1]).toComplex();
        zscal(N, TMP, VL(1, I).asArray(), 1);
        VL[K][I] = VL[K][I].real.toComplex();
      }
    }

    if (WANTVR) {
      // Undo balancing of right eigenvectors
      // (CWorkspace: none)
      // (RWorkspace: need N)

      zgebak('B', 'R', N, ILO.value, IHI.value, RWORK(IBAL), N, VR, LDVR, IERR);

      // Normalize right eigenvectors and make largest component real

      for (I = 1; I <= N; I++) {
        SCL = ONE / dznrm2(N, VR(1, I).asArray(), 1);
        zdscal(N, SCL, VR(1, I).asArray(), 1);
        for (K = 1; K <= N; K++) {
          RWORK[IRWORK + K - 1] =
              pow(VR[K][I].real, 2).toDouble() + pow(VR[K][I].imaginary, 2);
        }
        K = idamax(N, RWORK(IRWORK), 1);
        TMP = VR[K][I].conjugate() / sqrt(RWORK[IRWORK + K - 1]).toComplex();
        zscal(N, TMP, VR(1, I).asArray(), 1);
        VR[K][I] = VR[K][I].real.toComplex();
      }
    }

    // Undo scaling if necessary
  }
  if (SCALEA) {
    zlascl(
        'G',
        0,
        0,
        CSCALE,
        ANRM,
        N - INFO.value,
        1,
        W(INFO.value + 1).asMatrix(max(N - INFO.value, 1)),
        max(N - INFO.value, 1),
        IERR);
    if (INFO.value > 0) {
      zlascl('G', 0, 0, CSCALE, ANRM, ILO.value - 1, 1, W.asMatrix(N), N, IERR);
    }
  }

  WORK[1] = MAXWRK.toComplex();
}