1       SUBROUTINE CTPMV(UPLO,TRANS,DIAG,N,AP,X,INCX)
  2 *     .. Scalar Arguments ..
  3       INTEGER INCX,N
  4       CHARACTER DIAG,TRANS,UPLO
  5 *     ..
  6 *     .. Array Arguments ..
  7       COMPLEX AP(*),X(*)
  8 *     ..
  9 *
 10 *  Purpose
 11 *  =======
 12 *
 13 *  CTPMV  performs one of the matrix-vector operations
 14 *
 15 *     x := A*x,   or   x := A**T*x,   or   x := A**H*x,
 16 *
 17 *  where x is an n element vector and  A is an n by n unit, or non-unit,
 18 *  upper or lower triangular matrix, supplied in packed form.
 19 *
 20 *  Arguments
 21 *  ==========
 22 *
 23 *  UPLO   - CHARACTER*1.
 24 *           On entry, UPLO specifies whether the matrix is an upper or
 25 *           lower triangular matrix as follows:
 26 *
 27 *              UPLO = 'U' or 'u'   A is an upper triangular matrix.
 28 *
 29 *              UPLO = 'L' or 'l'   A is a lower triangular matrix.
 30 *
 31 *           Unchanged on exit.
 32 *
 33 *  TRANS  - CHARACTER*1.
 34 *           On entry, TRANS specifies the operation to be performed as
 35 *           follows:
 36 *
 37 *              TRANS = 'N' or 'n'   x := A*x.
 38 *
 39 *              TRANS = 'T' or 't'   x := A**T*x.
 40 *
 41 *              TRANS = 'C' or 'c'   x := A**H*x.
 42 *
 43 *           Unchanged on exit.
 44 *
 45 *  DIAG   - CHARACTER*1.
 46 *           On entry, DIAG specifies whether or not A is unit
 47 *           triangular as follows:
 48 *
 49 *              DIAG = 'U' or 'u'   A is assumed to be unit triangular.
 50 *
 51 *              DIAG = 'N' or 'n'   A is not assumed to be unit
 52 *                                  triangular.
 53 *
 54 *           Unchanged on exit.
 55 *
 56 *  N      - INTEGER.
 57 *           On entry, N specifies the order of the matrix A.
 58 *           N must be at least zero.
 59 *           Unchanged on exit.
 60 *
 61 *  AP     - COMPLEX          array of DIMENSION at least
 62 *           ( ( n*( n + 1 ) )/2 ).
 63 *           Before entry with  UPLO = 'U' or 'u', the array AP must
 64 *           contain the upper triangular matrix packed sequentially,
 65 *           column by column, so that AP( 1 ) contains a( 1, 1 ),
 66 *           AP( 2 ) and AP( 3 ) contain a( 1, 2 ) and a( 2, 2 )
 67 *           respectively, and so on.
 68 *           Before entry with UPLO = 'L' or 'l', the array AP must
 69 *           contain the lower triangular matrix packed sequentially,
 70 *           column by column, so that AP( 1 ) contains a( 1, 1 ),
 71 *           AP( 2 ) and AP( 3 ) contain a( 2, 1 ) and a( 3, 1 )
 72 *           respectively, and so on.
 73 *           Note that when  DIAG = 'U' or 'u', the diagonal elements of
 74 *           A are not referenced, but are assumed to be unity.
 75 *           Unchanged on exit.
 76 *
 77 *  X      - COMPLEX          array of dimension at least
 78 *           ( 1 + ( n - 1 )*abs( INCX ) ).
 79 *           Before entry, the incremented array X must contain the n
 80 *           element vector x. On exit, X is overwritten with the
 81 *           tranformed vector x.
 82 *
 83 *  INCX   - INTEGER.
 84 *           On entry, INCX specifies the increment for the elements of
 85 *           X. INCX must not be zero.
 86 *           Unchanged on exit.
 87 *
 88 *  Further Details
 89 *  ===============
 90 *
 91 *  Level 2 Blas routine.
 92 *  The vector and matrix arguments are not referenced when N = 0, or M = 0
 93 *
 94 *  -- Written on 22-October-1986.
 95 *     Jack Dongarra, Argonne National Lab.
 96 *     Jeremy Du Croz, Nag Central Office.
 97 *     Sven Hammarling, Nag Central Office.
 98 *     Richard Hanson, Sandia National Labs.
 99 *
100 *  =====================================================================
101 *
102 *     .. Parameters ..
103       COMPLEX ZERO
104       PARAMETER (ZERO= (0.0E+0,0.0E+0))
105 *     ..
106 *     .. Local Scalars ..
107       COMPLEX TEMP
108       INTEGER I,INFO,IX,J,JX,K,KK,KX
109       LOGICAL NOCONJ,NOUNIT
110 *     ..
111 *     .. External Functions ..
112       LOGICAL LSAME
113       EXTERNAL LSAME
114 *     ..
115 *     .. External Subroutines ..
116       EXTERNAL XERBLA
117 *     ..
118 *     .. Intrinsic Functions ..
119       INTRINSIC CONJG
120 *     ..
121 *
122 *     Test the input parameters.
123 *
124       INFO = 0
125       IF (.NOT.LSAME(UPLO,'U'.AND. .NOT.LSAME(UPLO,'L')) THEN
126           INFO = 1
127       ELSE IF (.NOT.LSAME(TRANS,'N'.AND. .NOT.LSAME(TRANS,'T'.AND.
128      +         .NOT.LSAME(TRANS,'C')) THEN
129           INFO = 2
130       ELSE IF (.NOT.LSAME(DIAG,'U'.AND. .NOT.LSAME(DIAG,'N')) THEN
131           INFO = 3
132       ELSE IF (N.LT.0THEN
133           INFO = 4
134       ELSE IF (INCX.EQ.0THEN
135           INFO = 7
136       END IF
137       IF (INFO.NE.0THEN
138           CALL XERBLA('CTPMV ',INFO)
139           RETURN
140       END IF
141 *
142 *     Quick return if possible.
143 *
144       IF (N.EQ.0RETURN
145 *
146       NOCONJ = LSAME(TRANS,'T')
147       NOUNIT = LSAME(DIAG,'N')
148 *
149 *     Set up the start point in X if the increment is not unity. This
150 *     will be  ( N - 1 )*INCX  too small for descending loops.
151 *
152       IF (INCX.LE.0THEN
153           KX = 1 - (N-1)*INCX
154       ELSE IF (INCX.NE.1THEN
155           KX = 1
156       END IF
157 *
158 *     Start the operations. In this version the elements of AP are
159 *     accessed sequentially with one pass through AP.
160 *
161       IF (LSAME(TRANS,'N')) THEN
162 *
163 *        Form  x:= A*x.
164 *
165           IF (LSAME(UPLO,'U')) THEN
166               KK = 1
167               IF (INCX.EQ.1THEN
168                   DO 20 J = 1,N
169                       IF (X(J).NE.ZERO) THEN
170                           TEMP = X(J)
171                           K = KK
172                           DO 10 I = 1,J - 1
173                               X(I) = X(I) + TEMP*AP(K)
174                               K = K + 1
175    10                     CONTINUE
176                           IF (NOUNIT) X(J) = X(J)*AP(KK+J-1)
177                       END IF
178                       KK = KK + J
179    20             CONTINUE
180               ELSE
181                   JX = KX
182                   DO 40 J = 1,N
183                       IF (X(JX).NE.ZERO) THEN
184                           TEMP = X(JX)
185                           IX = KX
186                           DO 30 K = KK,KK + J - 2
187                               X(IX) = X(IX) + TEMP*AP(K)
188                               IX = IX + INCX
189    30                     CONTINUE
190                           IF (NOUNIT) X(JX) = X(JX)*AP(KK+J-1)
191                       END IF
192                       JX = JX + INCX
193                       KK = KK + J
194    40             CONTINUE
195               END IF
196           ELSE
197               KK = (N* (N+1))/2
198               IF (INCX.EQ.1THEN
199                   DO 60 J = N,1,-1
200                       IF (X(J).NE.ZERO) THEN
201                           TEMP = X(J)
202                           K = KK
203                           DO 50 I = N,J + 1,-1
204                               X(I) = X(I) + TEMP*AP(K)
205                               K = K - 1
206    50                     CONTINUE
207                           IF (NOUNIT) X(J) = X(J)*AP(KK-N+J)
208                       END IF
209                       KK = KK - (N-J+1)
210    60             CONTINUE
211               ELSE
212                   KX = KX + (N-1)*INCX
213                   JX = KX
214                   DO 80 J = N,1,-1
215                       IF (X(JX).NE.ZERO) THEN
216                           TEMP = X(JX)
217                           IX = KX
218                           DO 70 K = KK,KK - (N- (J+1)),-1
219                               X(IX) = X(IX) + TEMP*AP(K)
220                               IX = IX - INCX
221    70                     CONTINUE
222                           IF (NOUNIT) X(JX) = X(JX)*AP(KK-N+J)
223                       END IF
224                       JX = JX - INCX
225                       KK = KK - (N-J+1)
226    80             CONTINUE
227               END IF
228           END IF
229       ELSE
230 *
231 *        Form  x := A**T*x  or  x := A**H*x.
232 *
233           IF (LSAME(UPLO,'U')) THEN
234               KK = (N* (N+1))/2
235               IF (INCX.EQ.1THEN
236                   DO 110 J = N,1,-1
237                       TEMP = X(J)
238                       K = KK - 1
239                       IF (NOCONJ) THEN
240                           IF (NOUNIT) TEMP = TEMP*AP(KK)
241                           DO 90 I = J - 1,1,-1
242                               TEMP = TEMP + AP(K)*X(I)
243                               K = K - 1
244    90                     CONTINUE
245                       ELSE
246                           IF (NOUNIT) TEMP = TEMP*CONJG(AP(KK))
247                           DO 100 I = J - 1,1,-1
248                               TEMP = TEMP + CONJG(AP(K))*X(I)
249                               K = K - 1
250   100                     CONTINUE
251                       END IF
252                       X(J) = TEMP
253                       KK = KK - J
254   110             CONTINUE
255               ELSE
256                   JX = KX + (N-1)*INCX
257                   DO 140 J = N,1,-1
258                       TEMP = X(JX)
259                       IX = JX
260                       IF (NOCONJ) THEN
261                           IF (NOUNIT) TEMP = TEMP*AP(KK)
262                           DO 120 K = KK - 1,KK - J + 1,-1
263                               IX = IX - INCX
264                               TEMP = TEMP + AP(K)*X(IX)
265   120                     CONTINUE
266                       ELSE
267                           IF (NOUNIT) TEMP = TEMP*CONJG(AP(KK))
268                           DO 130 K = KK - 1,KK - J + 1,-1
269                               IX = IX - INCX
270                               TEMP = TEMP + CONJG(AP(K))*X(IX)
271   130                     CONTINUE
272                       END IF
273                       X(JX) = TEMP
274                       JX = JX - INCX
275                       KK = KK - J
276   140             CONTINUE
277               END IF
278           ELSE
279               KK = 1
280               IF (INCX.EQ.1THEN
281                   DO 170 J = 1,N
282                       TEMP = X(J)
283                       K = KK + 1
284                       IF (NOCONJ) THEN
285                           IF (NOUNIT) TEMP = TEMP*AP(KK)
286                           DO 150 I = J + 1,N
287                               TEMP = TEMP + AP(K)*X(I)
288                               K = K + 1
289   150                     CONTINUE
290                       ELSE
291                           IF (NOUNIT) TEMP = TEMP*CONJG(AP(KK))
292                           DO 160 I = J + 1,N
293                               TEMP = TEMP + CONJG(AP(K))*X(I)
294                               K = K + 1
295   160                     CONTINUE
296                       END IF
297                       X(J) = TEMP
298                       KK = KK + (N-J+1)
299   170             CONTINUE
300               ELSE
301                   JX = KX
302                   DO 200 J = 1,N
303                       TEMP = X(JX)
304                       IX = JX
305                       IF (NOCONJ) THEN
306                           IF (NOUNIT) TEMP = TEMP*AP(KK)
307                           DO 180 K = KK + 1,KK + N - J
308                               IX = IX + INCX
309                               TEMP = TEMP + AP(K)*X(IX)
310   180                     CONTINUE
311                       ELSE
312                           IF (NOUNIT) TEMP = TEMP*CONJG(AP(KK))
313                           DO 190 K = KK + 1,KK + N - J
314                               IX = IX + INCX
315                               TEMP = TEMP + CONJG(AP(K))*X(IX)
316   190                     CONTINUE
317                       END IF
318                       X(JX) = TEMP
319                       JX = JX + INCX
320                       KK = KK + (N-J+1)
321   200             CONTINUE
322               END IF
323           END IF
324       END IF
325 *
326       RETURN
327 *
328 *     End of CTPMV .
329 *
330       END