SCALAPACK 2.2.2
LAPACK: Linear Algebra PACKage
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◆ zagemv()

subroutine zagemv ( character*1  trans,
integer  m,
integer  n,
double precision  alpha,
complex*16, dimension( lda, * )  a,
integer  lda,
complex*16, dimension( * )  x,
integer  incx,
double precision  beta,
double precision, dimension( * )  y,
integer  incy 
)

Definition at line 1 of file zagemv.f.

3*
4* -- PBLAS auxiliary routine (version 2.0) --
5* University of Tennessee, Knoxville, Oak Ridge National Laboratory,
6* and University of California, Berkeley.
7* April 1, 1998
8*
9* .. Scalar Arguments ..
10 CHARACTER*1 TRANS
11 INTEGER INCX, INCY, LDA, M, N
12 DOUBLE PRECISION ALPHA, BETA
13* ..
14* .. Array Arguments ..
15 DOUBLE PRECISION Y( * )
16 COMPLEX*16 A( LDA, * ), X( * )
17* ..
18*
19* Purpose
20* =======
21*
22* ZAGEMV performs one of the matrix-vector operations
23*
24* y := abs( alpha )*abs( A )*abs( x )+ abs( beta*y ),
25*
26* or
27*
28* y := abs( alpha )*abs( A' )*abs( x ) + abs( beta*y ),
29*
30* or
31*
32* y := abs( alpha )*abs( conjg( A' ) )*abs( x ) + abs( beta*y ),
33*
34* where alpha and beta are real scalars, y is a real vector, x is a
35* vector and A is an m by n matrix.
36*
37* Arguments
38* =========
39*
40* TRANS (input) CHARACTER*1
41* On entry, TRANS specifies the operation to be performed as
42* follows:
43*
44* TRANS = 'N' or 'n':
45* y := abs( alpha )*abs( A )*abs( x )+ abs( beta*y )
46*
47* TRANS = 'T' or 't':
48* y := abs( alpha )*abs( A' )*abs( x ) + abs( beta*y )
49*
50* TRANS = 'C' or 'c':
51* y := abs( alpha )*abs( conjg( A' ) )*abs( x ) +
52* abs( beta*y )
53*
54* M (input) INTEGER
55* On entry, M specifies the number of rows of the matrix A. M
56* must be at least zero.
57*
58* N (input) INTEGER
59* On entry, N specifies the number of columns of the matrix A.
60* N must be at least zero.
61*
62* ALPHA (input) DOUBLE PRECISION
63* On entry, ALPHA specifies the real scalar alpha.
64*
65* A (input) COMPLEX*16 array of dimension ( LDA, n ).
66* On entry, A is an array of dimension ( LDA, N ). The leading
67* m by n part of the array A must contain the matrix of coef-
68* ficients.
69*
70* LDA (input) INTEGER
71* On entry, LDA specifies the leading dimension of the array A.
72* LDA must be at least max( 1, M ).
73*
74* X (input) COMPLEX*16 array of dimension at least
75* ( 1 + ( n - 1 )*abs( INCX ) ) when TRANS = 'N' or 'n' and at
76* least ( 1 + ( m - 1 )*abs( INCX ) ) otherwise. Before entry,
77* the incremented array X must contain the vector x.
78*
79* INCX (input) INTEGER
80* On entry, INCX specifies the increment for the elements of X.
81* INCX must not be zero.
82*
83* BETA (input) DOUBLE PRECISION
84* On entry, BETA specifies the real scalar beta. When BETA is
85* supplied as zero then Y need not be set on input.
86*
87* Y (input/output) DOUBLE PRECISION array of dimension at least
88* ( 1 + ( m - 1 )*abs( INCY ) ) when TRANS = 'N' or 'n' and at
89* least ( 1 + ( n - 1 )*abs( INCY ) ) otherwise. Before entry
90* with BETA non-zero, the incremented array Y must contain the
91* vector y. On exit, the incremented array Y is overwritten by
92* the updated vector y.
93*
94* INCY (input) INTEGER
95* On entry, INCY specifies the increment for the elements of Y.
96* INCY must not be zero.
97*
98* -- Written on April 1, 1998 by
99* Antoine Petitet, University of Tennessee, Knoxville 37996, USA.
100*
101* =====================================================================
102*
103* .. Parameters ..
104 DOUBLE PRECISION ONE, ZERO
105 parameter( one = 1.0d+0, zero = 0.0d+0 )
106* ..
107* .. Local Scalars ..
108 INTEGER I, INFO, IX, IY, J, JX, JY, KX, KY, LENX, LENY
109 DOUBLE PRECISION ABSX, TALPHA, TEMP
110 COMPLEX*16 ZDUM
111* ..
112* .. External Functions ..
113 LOGICAL LSAME
114 EXTERNAL lsame
115* ..
116* .. External Subroutines ..
117 EXTERNAL xerbla
118* ..
119* .. Intrinsic Functions ..
120 INTRINSIC abs, dble, dimag, max
121* ..
122* .. Statement Functions ..
123 DOUBLE PRECISION CABS1
124 cabs1( zdum ) = abs( dble( zdum ) ) + abs( dimag( zdum ) )
125* ..
126* .. Executable Statements ..
127*
128* Test the input parameters.
129*
130 info = 0
131 IF( .NOT.lsame( trans, 'N' ) .AND.
132 $ .NOT.lsame( trans, 'T' ) .AND.
133 $ .NOT.lsame( trans, 'C' ) ) THEN
134 info = 1
135 ELSE IF( m.LT.0 ) THEN
136 info = 2
137 ELSE IF( n.LT.0 ) THEN
138 info = 3
139 ELSE IF( lda.LT.max( 1, m ) ) THEN
140 info = 6
141 ELSE IF( incx.EQ.0 ) THEN
142 info = 8
143 ELSE IF( incy.EQ.0 ) THEN
144 info = 11
145 END IF
146 IF( info.NE.0 ) THEN
147 CALL xerbla( 'ZAGEMV', info )
148 RETURN
149 END IF
150*
151* Quick return if possible.
152*
153 IF( ( m.EQ.0 ).OR.( n.EQ.0 ).OR.
154 $ ( ( alpha.EQ.zero ).AND.( beta.EQ.one ) ) )
155 $ RETURN
156*
157* Set LENX and LENY, the lengths of the vectors x and y, and set
158* up the start points in X and Y.
159*
160 IF( lsame( trans, 'N' ) ) THEN
161 lenx = n
162 leny = m
163 ELSE
164 lenx = m
165 leny = n
166 END IF
167 IF( incx.GT.0 ) THEN
168 kx = 1
169 ELSE
170 kx = 1 - ( lenx - 1 )*incx
171 END IF
172 IF( incy.GT.0 ) THEN
173 ky = 1
174 ELSE
175 ky = 1 - ( leny - 1 )*incy
176 END IF
177*
178* Start the operations. In this version the elements of A are
179* accessed sequentially with one pass through A.
180*
181* First form y := abs( beta*y ).
182*
183 IF( incy.EQ.1 ) THEN
184 IF( beta.EQ.zero ) THEN
185 DO 10, i = 1, leny
186 y( i ) = zero
187 10 CONTINUE
188 ELSE IF( beta.EQ.one ) THEN
189 DO 20, i = 1, leny
190 y( i ) = abs( y( i ) )
191 20 CONTINUE
192 ELSE
193 DO 30, i = 1, leny
194 y( i ) = abs( beta * y( i ) )
195 30 CONTINUE
196 END IF
197 ELSE
198 iy = ky
199 IF( beta.EQ.zero ) THEN
200 DO 40, i = 1, leny
201 y( iy ) = zero
202 iy = iy + incy
203 40 CONTINUE
204 ELSE IF( beta.EQ.one ) THEN
205 DO 50, i = 1, leny
206 y( iy ) = abs( y( iy ) )
207 iy = iy + incy
208 50 CONTINUE
209 ELSE
210 DO 60, i = 1, leny
211 y( iy ) = abs( beta * y( iy ) )
212 iy = iy + incy
213 60 CONTINUE
214 END IF
215 END IF
216*
217 IF( alpha.EQ.zero )
218 $ RETURN
219*
220 talpha = abs( alpha )
221*
222 IF( lsame( trans, 'N' ) ) THEN
223*
224* Form y := abs( alpha ) * abs( A ) * abs( x ) + y.
225*
226 jx = kx
227 IF( incy.EQ.1 ) THEN
228 DO 80, j = 1, n
229 absx = cabs1( x( jx ) )
230 IF( absx.NE.zero ) THEN
231 temp = talpha * absx
232 DO 70, i = 1, m
233 y( i ) = y( i ) + temp * cabs1( a( i, j ) )
234 70 CONTINUE
235 END IF
236 jx = jx + incx
237 80 CONTINUE
238 ELSE
239 DO 100, j = 1, n
240 absx = cabs1( x( jx ) )
241 IF( absx.NE.zero ) THEN
242 temp = talpha * absx
243 iy = ky
244 DO 90, i = 1, m
245 y( iy ) = y( iy ) + temp * cabs1( a( i, j ) )
246 iy = iy + incy
247 90 CONTINUE
248 END IF
249 jx = jx + incx
250 100 CONTINUE
251 END IF
252*
253 ELSE
254*
255* Form y := abs( alpha ) * abs( A' ) * abs( x ) + y.
256*
257 jy = ky
258 IF( incx.EQ.1 ) THEN
259 DO 120, j = 1, n
260 temp = zero
261 DO 110, i = 1, m
262 temp = temp + cabs1( a( i, j ) ) * cabs1( x( i ) )
263 110 CONTINUE
264 y( jy ) = y( jy ) + talpha * temp
265 jy = jy + incy
266 120 CONTINUE
267 ELSE
268 DO 140, j = 1, n
269 temp = zero
270 ix = kx
271 DO 130, i = 1, m
272 temp = temp + cabs1( a( i, j ) ) * cabs1( x( ix ) )
273 ix = ix + incx
274 130 CONTINUE
275 y( jy ) = y( jy ) + talpha * temp
276 jy = jy + incy
277 140 CONTINUE
278 END IF
279 END IF
280*
281 RETURN
282*
283* End of ZAGEMV
284*
max
#define max(A, B)
Definition pcgemr.c:180
lsame
logical function lsame(ca, cb)
Definition tools.f:1724