.TH "TESTING/EIG/dstt22.f" 3 "Version 3.12.0" "LAPACK" \" -*- nroff -*-
.ad l
.nh
.SH NAME
TESTING/EIG/dstt22.f
.SH SYNOPSIS
.br
.PP
.SS "Functions/Subroutines"

.in +1c
.ti -1c
.RI "subroutine \fBdstt22\fP (n, m, kband, ad, ae, sd, se, u, ldu, work, ldwork, result)"
.br
.RI "\fBDSTT22\fP "
.in -1c
.SH "Function/Subroutine Documentation"
.PP 
.SS "subroutine dstt22 (integer n, integer m, integer kband, double precision, dimension( * ) ad, double precision, dimension( * ) ae, double precision, dimension( * ) sd, double precision, dimension( * ) se, double precision, dimension( ldu, * ) u, integer ldu, double precision, dimension( ldwork, * ) work, integer ldwork, double precision, dimension( 2 ) result)"

.PP
\fBDSTT22\fP 
.PP
\fBPurpose:\fP
.RS 4

.PP
.nf
 DSTT22  checks a set of M eigenvalues and eigenvectors,

     A U = U S

 where A is symmetric tridiagonal, the columns of U are orthogonal,
 and S is diagonal (if KBAND=0) or symmetric tridiagonal (if KBAND=1)\&.
 Two tests are performed:

    RESULT(1) = | U' A U - S | / ( |A| m ulp )

    RESULT(2) = | I - U'U | / ( m ulp )
.fi
.PP
 
.RE
.PP
\fBParameters\fP
.RS 4
\fIN\fP 
.PP
.nf
          N is INTEGER
          The size of the matrix\&.  If it is zero, DSTT22 does nothing\&.
          It must be at least zero\&.
.fi
.PP
.br
\fIM\fP 
.PP
.nf
          M is INTEGER
          The number of eigenpairs to check\&.  If it is zero, DSTT22
          does nothing\&.  It must be at least zero\&.
.fi
.PP
.br
\fIKBAND\fP 
.PP
.nf
          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 symmetric tri-diagonal\&.
.fi
.PP
.br
\fIAD\fP 
.PP
.nf
          AD is DOUBLE PRECISION array, dimension (N)
          The diagonal of the original (unfactored) matrix A\&.  A is
          assumed to be symmetric tridiagonal\&.
.fi
.PP
.br
\fIAE\fP 
.PP
.nf
          AE is DOUBLE PRECISION array, dimension (N)
          The off-diagonal of the original (unfactored) matrix A\&.  A
          is assumed to be symmetric tridiagonal\&.  AE(1) is ignored,
          AE(2) is the (1,2) and (2,1) element, etc\&.
.fi
.PP
.br
\fISD\fP 
.PP
.nf
          SD is DOUBLE PRECISION array, dimension (N)
          The diagonal of the (symmetric tri-) diagonal matrix S\&.
.fi
.PP
.br
\fISE\fP 
.PP
.nf
          SE is DOUBLE PRECISION array, dimension (N)
          The off-diagonal of the (symmetric 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\&.
.fi
.PP
.br
\fIU\fP 
.PP
.nf
          U is DOUBLE PRECISION array, dimension (LDU, N)
          The orthogonal matrix in the decomposition\&.
.fi
.PP
.br
\fILDU\fP 
.PP
.nf
          LDU is INTEGER
          The leading dimension of U\&.  LDU must be at least N\&.
.fi
.PP
.br
\fIWORK\fP 
.PP
.nf
          WORK is DOUBLE PRECISION array, dimension (LDWORK, M+1)
.fi
.PP
.br
\fILDWORK\fP 
.PP
.nf
          LDWORK is INTEGER
          The leading dimension of WORK\&.  LDWORK must be at least
          max(1,M)\&.
.fi
.PP
.br
\fIRESULT\fP 
.PP
.nf
          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\&.
.fi
.PP
 
.RE
.PP
\fBAuthor\fP
.RS 4
Univ\&. of Tennessee 
.PP
Univ\&. of California Berkeley 
.PP
Univ\&. of Colorado Denver 
.PP
NAG Ltd\&. 
.RE
.PP

.PP
Definition at line \fB137\fP of file \fBdstt22\&.f\fP\&.
.SH "Author"
.PP 
Generated automatically by Doxygen for LAPACK from the source code\&.