LAPACK  3.10.1 LAPACK: Linear Algebra PACKage

## ◆ cppt03()

 subroutine cppt03 ( character UPLO, integer N, complex, dimension( * ) A, complex, dimension( * ) AINV, complex, dimension( ldwork, * ) WORK, integer LDWORK, real, dimension( * ) RWORK, real RCOND, real RESID )

CPPT03

Purpose:
``` CPPT03 computes the residual for a Hermitian packed matrix times its
inverse:
norm( I - A*AINV ) / ( N * norm(A) * norm(AINV) * EPS ),
where EPS is the machine epsilon.```
Parameters
 [in] UPLO ``` UPLO is CHARACTER*1 Specifies whether the upper or lower triangular part of the Hermitian matrix A is stored: = 'U': Upper triangular = 'L': Lower triangular``` [in] N ``` N is INTEGER The number of rows and columns of the matrix A. N >= 0.``` [in] A ``` A is COMPLEX array, dimension (N*(N+1)/2) The original Hermitian matrix A, stored as a packed triangular matrix.``` [in] AINV ``` AINV is COMPLEX array, dimension (N*(N+1)/2) The (Hermitian) inverse of the matrix A, stored as a packed triangular matrix.``` [out] WORK ` WORK is COMPLEX array, dimension (LDWORK,N)` [in] LDWORK ``` LDWORK is INTEGER The leading dimension of the array WORK. LDWORK >= max(1,N).``` [out] RWORK ` RWORK is REAL array, dimension (N)` [out] RCOND ``` RCOND is REAL The reciprocal of the condition number of A, computed as ( 1/norm(A) ) / norm(AINV).``` [out] RESID ``` RESID is REAL norm(I - A*AINV) / ( N * norm(A) * norm(AINV) * EPS )```

Definition at line 108 of file cppt03.f.

110 *
111 * -- LAPACK test routine --
112 * -- LAPACK is a software package provided by Univ. of Tennessee, --
113 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
114 *
115 * .. Scalar Arguments ..
116  CHARACTER UPLO
117  INTEGER LDWORK, N
118  REAL RCOND, RESID
119 * ..
120 * .. Array Arguments ..
121  REAL RWORK( * )
122  COMPLEX A( * ), AINV( * ), WORK( LDWORK, * )
123 * ..
124 *
125 * =====================================================================
126 *
127 * .. Parameters ..
128  REAL ZERO, ONE
129  parameter( zero = 0.0e+0, one = 1.0e+0 )
130  COMPLEX CZERO, CONE
131  parameter( czero = ( 0.0e+0, 0.0e+0 ),
132  \$ cone = ( 1.0e+0, 0.0e+0 ) )
133 * ..
134 * .. Local Scalars ..
135  INTEGER I, J, JJ
136  REAL AINVNM, ANORM, EPS
137 * ..
138 * .. External Functions ..
139  LOGICAL LSAME
140  REAL CLANGE, CLANHP, SLAMCH
141  EXTERNAL lsame, clange, clanhp, slamch
142 * ..
143 * .. Intrinsic Functions ..
144  INTRINSIC conjg, real
145 * ..
146 * .. External Subroutines ..
147  EXTERNAL ccopy, chpmv
148 * ..
149 * .. Executable Statements ..
150 *
151 * Quick exit if N = 0.
152 *
153  IF( n.LE.0 ) THEN
154  rcond = one
155  resid = zero
156  RETURN
157  END IF
158 *
159 * Exit with RESID = 1/EPS if ANORM = 0 or AINVNM = 0.
160 *
161  eps = slamch( 'Epsilon' )
162  anorm = clanhp( '1', uplo, n, a, rwork )
163  ainvnm = clanhp( '1', uplo, n, ainv, rwork )
164  IF( anorm.LE.zero .OR. ainvnm.LE.zero ) THEN
165  rcond = zero
166  resid = one / eps
167  RETURN
168  END IF
169  rcond = ( one/anorm ) / ainvnm
170 *
171 * UPLO = 'U':
172 * Copy the leading N-1 x N-1 submatrix of AINV to WORK(1:N,2:N) and
173 * expand it to a full matrix, then multiply by A one column at a
174 * time, moving the result one column to the left.
175 *
176  IF( lsame( uplo, 'U' ) ) THEN
177 *
178 * Copy AINV
179 *
180  jj = 1
181  DO 20 j = 1, n - 1
182  CALL ccopy( j, ainv( jj ), 1, work( 1, j+1 ), 1 )
183  DO 10 i = 1, j - 1
184  work( j, i+1 ) = conjg( ainv( jj+i-1 ) )
185  10 CONTINUE
186  jj = jj + j
187  20 CONTINUE
188  jj = ( ( n-1 )*n ) / 2 + 1
189  DO 30 i = 1, n - 1
190  work( n, i+1 ) = conjg( ainv( jj+i-1 ) )
191  30 CONTINUE
192 *
193 * Multiply by A
194 *
195  DO 40 j = 1, n - 1
196  CALL chpmv( 'Upper', n, -cone, a, work( 1, j+1 ), 1, czero,
197  \$ work( 1, j ), 1 )
198  40 CONTINUE
199  CALL chpmv( 'Upper', n, -cone, a, ainv( jj ), 1, czero,
200  \$ work( 1, n ), 1 )
201 *
202 * UPLO = 'L':
203 * Copy the trailing N-1 x N-1 submatrix of AINV to WORK(1:N,1:N-1)
204 * and multiply by A, moving each column to the right.
205 *
206  ELSE
207 *
208 * Copy AINV
209 *
210  DO 50 i = 1, n - 1
211  work( 1, i ) = conjg( ainv( i+1 ) )
212  50 CONTINUE
213  jj = n + 1
214  DO 70 j = 2, n
215  CALL ccopy( n-j+1, ainv( jj ), 1, work( j, j-1 ), 1 )
216  DO 60 i = 1, n - j
217  work( j, j+i-1 ) = conjg( ainv( jj+i ) )
218  60 CONTINUE
219  jj = jj + n - j + 1
220  70 CONTINUE
221 *
222 * Multiply by A
223 *
224  DO 80 j = n, 2, -1
225  CALL chpmv( 'Lower', n, -cone, a, work( 1, j-1 ), 1, czero,
226  \$ work( 1, j ), 1 )
227  80 CONTINUE
228  CALL chpmv( 'Lower', n, -cone, a, ainv( 1 ), 1, czero,
229  \$ work( 1, 1 ), 1 )
230 *
231  END IF
232 *
233 * Add the identity matrix to WORK .
234 *
235  DO 90 i = 1, n
236  work( i, i ) = work( i, i ) + cone
237  90 CONTINUE
238 *
239 * Compute norm(I - A*AINV) / (N * norm(A) * norm(AINV) * EPS)
240 *
241  resid = clange( '1', n, n, work, ldwork, rwork )
242 *
243  resid = ( ( resid*rcond )/eps ) / real( n )
244 *
245  RETURN
246 *
247 * End of CPPT03
248 *
logical function lsame(CA, CB)
LSAME
Definition: lsame.f:53
subroutine ccopy(N, CX, INCX, CY, INCY)
CCOPY
Definition: ccopy.f:81
subroutine chpmv(UPLO, N, ALPHA, AP, X, INCX, BETA, Y, INCY)
CHPMV
Definition: chpmv.f:149
real function clange(NORM, M, N, A, LDA, WORK)
CLANGE returns the value of the 1-norm, Frobenius norm, infinity-norm, or the largest absolute value ...
Definition: clange.f:115
real function clanhp(NORM, UPLO, N, AP, WORK)
CLANHP returns the value of the 1-norm, or the Frobenius norm, or the infinity norm,...
Definition: clanhp.f:117
real function slamch(CMACH)
SLAMCH
Definition: slamch.f:68
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