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LAPACK
3.7.0
LAPACK: Linear Algebra PACKage
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subroutine zstt22 | ( | integer | N, |
integer | M, | ||
integer | KBAND, | ||
double precision, dimension( * ) | AD, | ||
double precision, dimension( * ) | AE, | ||
double precision, dimension( * ) | SD, | ||
double precision, dimension( * ) | SE, | ||
complex*16, dimension( ldu, * ) | U, | ||
integer | LDU, | ||
complex*16, dimension( ldwork, * ) | WORK, | ||
integer | LDWORK, | ||
double precision, dimension( * ) | RWORK, | ||
double precision, dimension( 2 ) | RESULT | ||
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ZSTT22
ZSTT22 checks a set of M eigenvalues and eigenvectors, A U = U S where A is Hermitian tridiagonal, the columns of U are unitary, and S is diagonal (if KBAND=0) or Hermitian tridiagonal (if KBAND=1). Two tests are performed: RESULT(1) = | U* A U - S | / ( |A| m ulp ) RESULT(2) = | I - U*U | / ( m ulp )
[in] | N | N is INTEGER The size of the matrix. If it is zero, ZSTT22 does nothing. It must be at least zero. |
[in] | M | M is INTEGER The number of eigenpairs to check. If it is zero, ZSTT22 does nothing. It must be at least zero. |
[in] | KBAND | KBAND is INTEGER The bandwidth of the matrix S. It may only be zero or one. If zero, then S is diagonal, and SE is not referenced. If one, then S is Hermitian tri-diagonal. |
[in] | AD | AD is DOUBLE PRECISION array, dimension (N) The diagonal of the original (unfactored) matrix A. A is assumed to be Hermitian tridiagonal. |
[in] | AE | AE is DOUBLE PRECISION array, dimension (N) The off-diagonal of the original (unfactored) matrix A. A is assumed to be Hermitian tridiagonal. AE(1) is ignored, AE(2) is the (1,2) and (2,1) element, etc. |
[in] | SD | SD is DOUBLE PRECISION array, dimension (N) The diagonal of the (Hermitian tri-) diagonal matrix S. |
[in] | SE | SE is DOUBLE PRECISION array, dimension (N) The off-diagonal of the (Hermitian tri-) diagonal matrix S. Not referenced if KBSND=0. If KBAND=1, then AE(1) is ignored, SE(2) is the (1,2) and (2,1) element, etc. |
[in] | U | U is DOUBLE PRECISION array, dimension (LDU, N) The unitary matrix in the decomposition. |
[in] | LDU | LDU is INTEGER The leading dimension of U. LDU must be at least N. |
[out] | WORK | WORK is COMPLEX*16 array, dimension (LDWORK, M+1) |
[in] | LDWORK | LDWORK is INTEGER The leading dimension of WORK. LDWORK must be at least max(1,M). |
[out] | RWORK | RWORK is DOUBLE PRECISION array, dimension (N) |
[out] | RESULT | RESULT is DOUBLE PRECISION array, dimension (2) The values computed by the two tests described above. The values are currently limited to 1/ulp, to avoid overflow. |
Definition at line 147 of file zstt22.f.