.TH "slaed4.f" 3 "Wed Oct 15 2014" "Version 3.4.2" "LAPACK" \" -*- nroff -*-
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.SH NAME
slaed4.f \- 
.SH SYNOPSIS
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.SS "Functions/Subroutines"

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.ti -1c
.RI "subroutine \fBslaed4\fP (N, I, D, Z, DELTA, RHO, DLAM, INFO)"
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.RI "\fI\fBSLAED4\fP used by sstedc\&. Finds a single root of the secular equation\&. \fP"
.in -1c
.SH "Function/Subroutine Documentation"
.PP 
.SS "subroutine slaed4 (integerN, integerI, real, dimension( * )D, real, dimension( * )Z, real, dimension( * )DELTA, realRHO, realDLAM, integerINFO)"

.PP
\fBSLAED4\fP used by sstedc\&. Finds a single root of the secular equation\&.  
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\fBPurpose: \fP
.RS 4

.PP
.nf
 This subroutine computes the I-th updated eigenvalue of a symmetric
 rank-one modification to a diagonal matrix whose elements are
 given in the array d, and that

            D(i) < D(j)  for  i < j

 and that RHO > 0.  This is arranged by the calling routine, and is
 no loss in generality.  The rank-one modified system is thus

            diag( D )  +  RHO * Z * Z_transpose.

 where we assume the Euclidean norm of Z is 1.

 The method consists of approximating the rational functions in the
 secular equation by simpler interpolating rational functions.
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.RE
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\fBParameters:\fP
.RS 4
\fIN\fP 
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          N is INTEGER
         The length of all arrays.
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\fII\fP 
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          I is INTEGER
         The index of the eigenvalue to be computed.  1 <= I <= N.
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\fID\fP 
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          D is REAL array, dimension (N)
         The original eigenvalues.  It is assumed that they are in
         order, D(I) < D(J)  for I < J.
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\fIZ\fP 
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          Z is REAL array, dimension (N)
         The components of the updating vector.
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\fIDELTA\fP 
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          DELTA is REAL array, dimension (N)
         If N .GT. 2, DELTA contains (D(j) - lambda_I) in its  j-th
         component.  If N = 1, then DELTA(1) = 1. If N = 2, see SLAED5
         for detail. The vector DELTA contains the information necessary
         to construct the eigenvectors by SLAED3 and SLAED9.
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\fIRHO\fP 
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          RHO is REAL
         The scalar in the symmetric updating formula.
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\fIDLAM\fP 
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          DLAM is REAL
         The computed lambda_I, the I-th updated eigenvalue.
.fi
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\fIINFO\fP 
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          INFO is INTEGER
         = 0:  successful exit
         > 0:  if INFO = 1, the updating process failed.
.fi
.PP
 
.RE
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\fBInternal Parameters: \fP
.RS 4

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.nf
  Logical variable ORGATI (origin-at-i?) is used for distinguishing
  whether D(i) or D(i+1) is treated as the origin.

            ORGATI = .true.    origin at i
            ORGATI = .false.   origin at i+1

   Logical variable SWTCH3 (switch-for-3-poles?) is for noting
   if we are working with THREE poles!

   MAXIT is the maximum number of iterations allowed for each
   eigenvalue.
.fi
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.RE
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\fBAuthor:\fP
.RS 4
Univ\&. of Tennessee 
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Univ\&. of California Berkeley 
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Univ\&. of Colorado Denver 
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NAG Ltd\&. 
.RE
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\fBDate:\fP
.RS 4
September 2012 
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\fBContributors: \fP
.RS 4
Ren-Cang Li, Computer Science Division, University of California at Berkeley, USA 
.RE
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Definition at line 146 of file slaed4\&.f\&.
.SH "Author"
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Generated automatically by Doxygen for LAPACK from the source code\&.