 LAPACK 3.11.0 LAPACK: Linear Algebra PACKage
Searching...
No Matches

## ◆ zlaptm()

 subroutine zlaptm ( character UPLO, integer N, integer NRHS, double precision ALPHA, double precision, dimension( * ) D, complex*16, dimension( * ) E, complex*16, dimension( ldx, * ) X, integer LDX, double precision BETA, complex*16, dimension( ldb, * ) B, integer LDB )

ZLAPTM

Purpose:
``` ZLAPTM multiplies an N by NRHS matrix X by a Hermitian tridiagonal
matrix A and stores the result in a matrix B.  The operation has the
form

B := alpha * A * X + beta * B

where alpha may be either 1. or -1. and beta may be 0., 1., or -1.```
Parameters
 [in] UPLO ``` UPLO is CHARACTER Specifies whether the superdiagonal or the subdiagonal of the tridiagonal matrix A is stored. = 'U': Upper, E is the superdiagonal of A. = 'L': Lower, E is the subdiagonal of A.``` [in] N ``` N is INTEGER The order of the matrix A. N >= 0.``` [in] NRHS ``` NRHS is INTEGER The number of right hand sides, i.e., the number of columns of the matrices X and B.``` [in] ALPHA ``` ALPHA is DOUBLE PRECISION The scalar alpha. ALPHA must be 1. or -1.; otherwise, it is assumed to be 0.``` [in] D ``` D is DOUBLE PRECISION array, dimension (N) The n diagonal elements of the tridiagonal matrix A.``` [in] E ``` E is COMPLEX*16 array, dimension (N-1) The (n-1) subdiagonal or superdiagonal elements of A.``` [in] X ``` X is COMPLEX*16 array, dimension (LDX,NRHS) The N by NRHS matrix X.``` [in] LDX ``` LDX is INTEGER The leading dimension of the array X. LDX >= max(N,1).``` [in] BETA ``` BETA is DOUBLE PRECISION The scalar beta. BETA must be 0., 1., or -1.; otherwise, it is assumed to be 1.``` [in,out] B ``` B is COMPLEX*16 array, dimension (LDB,NRHS) On entry, the N by NRHS matrix B. On exit, B is overwritten by the matrix expression B := alpha * A * X + beta * B.``` [in] LDB ``` LDB is INTEGER The leading dimension of the array B. LDB >= max(N,1).```

Definition at line 127 of file zlaptm.f.

129*
130* -- LAPACK test routine --
131* -- LAPACK is a software package provided by Univ. of Tennessee, --
132* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
133*
134* .. Scalar Arguments ..
135 CHARACTER UPLO
136 INTEGER LDB, LDX, N, NRHS
137 DOUBLE PRECISION ALPHA, BETA
138* ..
139* .. Array Arguments ..
140 DOUBLE PRECISION D( * )
141 COMPLEX*16 B( LDB, * ), E( * ), X( LDX, * )
142* ..
143*
144* =====================================================================
145*
146* .. Parameters ..
147 DOUBLE PRECISION ONE, ZERO
148 parameter( one = 1.0d+0, zero = 0.0d+0 )
149* ..
150* .. Local Scalars ..
151 INTEGER I, J
152* ..
153* .. External Functions ..
154 LOGICAL LSAME
155 EXTERNAL lsame
156* ..
157* .. Intrinsic Functions ..
158 INTRINSIC dconjg
159* ..
160* .. Executable Statements ..
161*
162 IF( n.EQ.0 )
163 \$ RETURN
164*
165 IF( beta.EQ.zero ) THEN
166 DO 20 j = 1, nrhs
167 DO 10 i = 1, n
168 b( i, j ) = zero
169 10 CONTINUE
170 20 CONTINUE
171 ELSE IF( beta.EQ.-one ) THEN
172 DO 40 j = 1, nrhs
173 DO 30 i = 1, n
174 b( i, j ) = -b( i, j )
175 30 CONTINUE
176 40 CONTINUE
177 END IF
178*
179 IF( alpha.EQ.one ) THEN
180 IF( lsame( uplo, 'U' ) ) THEN
181*
182* Compute B := B + A*X, where E is the superdiagonal of A.
183*
184 DO 60 j = 1, nrhs
185 IF( n.EQ.1 ) THEN
186 b( 1, j ) = b( 1, j ) + d( 1 )*x( 1, j )
187 ELSE
188 b( 1, j ) = b( 1, j ) + d( 1 )*x( 1, j ) +
189 \$ e( 1 )*x( 2, j )
190 b( n, j ) = b( n, j ) + dconjg( e( n-1 ) )*
191 \$ x( n-1, j ) + d( n )*x( n, j )
192 DO 50 i = 2, n - 1
193 b( i, j ) = b( i, j ) + dconjg( e( i-1 ) )*
194 \$ x( i-1, j ) + d( i )*x( i, j ) +
195 \$ e( i )*x( i+1, j )
196 50 CONTINUE
197 END IF
198 60 CONTINUE
199 ELSE
200*
201* Compute B := B + A*X, where E is the subdiagonal of A.
202*
203 DO 80 j = 1, nrhs
204 IF( n.EQ.1 ) THEN
205 b( 1, j ) = b( 1, j ) + d( 1 )*x( 1, j )
206 ELSE
207 b( 1, j ) = b( 1, j ) + d( 1 )*x( 1, j ) +
208 \$ dconjg( e( 1 ) )*x( 2, j )
209 b( n, j ) = b( n, j ) + e( n-1 )*x( n-1, j ) +
210 \$ d( n )*x( n, j )
211 DO 70 i = 2, n - 1
212 b( i, j ) = b( i, j ) + e( i-1 )*x( i-1, j ) +
213 \$ d( i )*x( i, j ) +
214 \$ dconjg( e( i ) )*x( i+1, j )
215 70 CONTINUE
216 END IF
217 80 CONTINUE
218 END IF
219 ELSE IF( alpha.EQ.-one ) THEN
220 IF( lsame( uplo, 'U' ) ) THEN
221*
222* Compute B := B - A*X, where E is the superdiagonal of A.
223*
224 DO 100 j = 1, nrhs
225 IF( n.EQ.1 ) THEN
226 b( 1, j ) = b( 1, j ) - d( 1 )*x( 1, j )
227 ELSE
228 b( 1, j ) = b( 1, j ) - d( 1 )*x( 1, j ) -
229 \$ e( 1 )*x( 2, j )
230 b( n, j ) = b( n, j ) - dconjg( e( n-1 ) )*
231 \$ x( n-1, j ) - d( n )*x( n, j )
232 DO 90 i = 2, n - 1
233 b( i, j ) = b( i, j ) - dconjg( e( i-1 ) )*
234 \$ x( i-1, j ) - d( i )*x( i, j ) -
235 \$ e( i )*x( i+1, j )
236 90 CONTINUE
237 END IF
238 100 CONTINUE
239 ELSE
240*
241* Compute B := B - A*X, where E is the subdiagonal of A.
242*
243 DO 120 j = 1, nrhs
244 IF( n.EQ.1 ) THEN
245 b( 1, j ) = b( 1, j ) - d( 1 )*x( 1, j )
246 ELSE
247 b( 1, j ) = b( 1, j ) - d( 1 )*x( 1, j ) -
248 \$ dconjg( e( 1 ) )*x( 2, j )
249 b( n, j ) = b( n, j ) - e( n-1 )*x( n-1, j ) -
250 \$ d( n )*x( n, j )
251 DO 110 i = 2, n - 1
252 b( i, j ) = b( i, j ) - e( i-1 )*x( i-1, j ) -
253 \$ d( i )*x( i, j ) -
254 \$ dconjg( e( i ) )*x( i+1, j )
255 110 CONTINUE
256 END IF
257 120 CONTINUE
258 END IF
259 END IF
260 RETURN
261*
262* End of ZLAPTM
263*
logical function lsame(CA, CB)
LSAME
Definition: lsame.f:53
Here is the caller graph for this function: