DLAHQRRun Method

public void Run(
	bool WANTT,
	bool WANTZ,
	int N,
	int ILO,
	int IHI,
	ref double[] H,
	int offset_h,
	int LDH,
	ref double[] WR,
	int offset_wr,
	ref double[] WI,
	int offset_wi,
	int ILOZ,
	int IHIZ,
	ref double[] Z,
	int offset_z,
	int LDZ,
	ref int INFO
)

Public Sub Run ( 
	WANTT As Boolean,
	WANTZ As Boolean,
	N As Integer,
	ILO As Integer,
	IHI As Integer,
	ByRef H As Double(),
	offset_h As Integer,
	LDH As Integer,
	ByRef WR As Double(),
	offset_wr As Integer,
	ByRef WI As Double(),
	offset_wi As Integer,
	ILOZ As Integer,
	IHIZ As Integer,
	ByRef Z As Double(),
	offset_z As Integer,
	LDZ As Integer,
	ByRef INFO As Integer
)

Parameters

WANTT  Boolean

(input) LOGICAL = .TRUE. : the full Schur form T is required; = .FALSE.: only eigenvalues are required.

WANTZ  Boolean

(input) LOGICAL = .TRUE. : the matrix of Schur vectors Z is required; = .FALSE.: Schur vectors are not required.

N  Int32

(input) INTEGER The order of the matrix H. N .GE. 0.

ILO  Int32

(input) INTEGER

IHI  Int32

(input) INTEGER It is assumed that H is already upper quasi-triangular in rows and columns IHI+1:N, and that H(ILO,ILO-1) = 0 (unless ILO = 1). DLAHQR works primarily with the Hessenberg submatrix in rows and columns ILO to IHI, but applies transformations to all of H if WANTT is .TRUE.. 1 .LE. ILO .LE. max(1,IHI); IHI .LE. N.

H  Double

(input/output) DOUBLE PRECISION array, dimension (LDH,N) On entry, the upper Hessenberg matrix H. On exit, if INFO is zero and if WANTT is .TRUE., H is upper quasi-triangular in rows and columns ILO:IHI, with any 2-by-2 diagonal blocks in standard form. If INFO is zero and WANTT is .FALSE., the contents of H are unspecified on exit. The output state of H if INFO is nonzero is given below under the description of INFO.

offset_h  Int32

 

LDH  Int32

(input) INTEGER The leading dimension of the array H. LDH .GE. max(1,N).

WR  Double

(output) DOUBLE PRECISION array, dimension (N)

offset_wr  Int32

 

WI  Double

(output) DOUBLE PRECISION array, dimension (N) The real and imaginary parts, respectively, of the computed eigenvalues ILO to IHI are stored in the corresponding elements of WR and WI. If two eigenvalues are computed as a complex conjugate pair, they are stored in consecutive elements of WR and WI, say the i-th and (i+1)th, with WI(i) .GT. 0 and WI(i+1) .LT. 0. If WANTT is .TRUE., the eigenvalues are stored in the same order as on the diagonal of the Schur form returned in H, with WR(i) = H(i,i), and, if H(i:i+1,i:i+1) is a 2-by-2 diagonal block, WI(i) = sqrt(H(i+1,i)*H(i,i+1)) and WI(i+1) = -WI(i).

offset_wi  Int32

 

ILOZ  Int32

(input) INTEGER

IHIZ  Int32

(input) INTEGER Specify the rows of Z to which transformations must be applied if WANTZ is .TRUE.. 1 .LE. ILOZ .LE. ILO; IHI .LE. IHIZ .LE. N.

Z  Double

(input/output) DOUBLE PRECISION array, dimension (LDZ,N) If WANTZ is .TRUE., on entry Z must contain the current matrix Z of transformations accumulated by DHSEQR, and on exit Z has been updated; transformations are applied only to the submatrix Z(ILOZ:IHIZ,ILO:IHI). If WANTZ is .FALSE., Z is not referenced.

offset_z  Int32

 

LDZ  Int32

(input) INTEGER The leading dimension of the array Z. LDZ .GE. max(1,N).

INFO  Int32

(output) INTEGER = 0: successful exit .GT. 0: If INFO = i, DLAHQR failed to compute all the eigenvalues ILO to IHI in a total of 30 iterations per eigenvalue; elements i+1:ihi of WR and WI contain those eigenvalues which have been successfully computed. If INFO .GT. 0 and WANTT is .FALSE., then on exit, the remaining unconverged eigenvalues are the eigenvalues of the upper Hessenberg matrix rows and columns ILO thorugh INFO of the final, output value of H. If INFO .GT. 0 and WANTT is .TRUE., then on exit (*) (initial value of H)*U = U*(final value of H) where U is an orthognal matrix. The final value of H is upper Hessenberg and triangular in rows and columns INFO+1 through IHI. If INFO .GT. 0 and WANTZ is .TRUE., then on exit (final value of Z) = (initial value of Z)*U where U is the orthogonal matrix in (*) (regardless of the value of WANTT.)

Reference