1: SUBROUTINE ZGEMV(TRANS,M,N,ALPHA,A,LDA,X,INCX,BETA,Y,INCY)
2: * .. Scalar Arguments ..
3: DOUBLE COMPLEX ALPHA,BETA
4: INTEGER INCX,INCY,LDA,M,N
5: CHARACTER TRANS
6: * ..
7: * .. Array Arguments ..
8: DOUBLE COMPLEX A(LDA,*),X(*),Y(*)
9: * ..
10: *
11: * Purpose
12: * =======
13: *
14: * ZGEMV performs one of the matrix-vector operations
15: *
16: * y := alpha*A*x + beta*y, or y := alpha*A**T*x + beta*y, or
17: *
18: * y := alpha*A**H*x + beta*y,
19: *
20: * where alpha and beta are scalars, x and y are vectors and A is an
21: * m by n matrix.
22: *
23: * Arguments
24: * ==========
25: *
26: * TRANS - CHARACTER*1.
27: * On entry, TRANS specifies the operation to be performed as
28: * follows:
29: *
30: * TRANS = 'N' or 'n' y := alpha*A*x + beta*y.
31: *
32: * TRANS = 'T' or 't' y := alpha*A**T*x + beta*y.
33: *
34: * TRANS = 'C' or 'c' y := alpha*A**H*x + beta*y.
35: *
36: * Unchanged on exit.
37: *
38: * M - INTEGER.
39: * On entry, M specifies the number of rows of the matrix A.
40: * M must be at least zero.
41: * Unchanged on exit.
42: *
43: * N - INTEGER.
44: * On entry, N specifies the number of columns of the matrix A.
45: * N must be at least zero.
46: * Unchanged on exit.
47: *
48: * ALPHA - COMPLEX*16 .
49: * On entry, ALPHA specifies the scalar alpha.
50: * Unchanged on exit.
51: *
52: * A - COMPLEX*16 array of DIMENSION ( LDA, n ).
53: * Before entry, the leading m by n part of the array A must
54: * contain the matrix of coefficients.
55: * Unchanged on exit.
56: *
57: * LDA - INTEGER.
58: * On entry, LDA specifies the first dimension of A as declared
59: * in the calling (sub) program. LDA must be at least
60: * max( 1, m ).
61: * Unchanged on exit.
62: *
63: * X - COMPLEX*16 array of DIMENSION at least
64: * ( 1 + ( n - 1 )*abs( INCX ) ) when TRANS = 'N' or 'n'
65: * and at least
66: * ( 1 + ( m - 1 )*abs( INCX ) ) otherwise.
67: * Before entry, the incremented array X must contain the
68: * vector x.
69: * Unchanged on exit.
70: *
71: * INCX - INTEGER.
72: * On entry, INCX specifies the increment for the elements of
73: * X. INCX must not be zero.
74: * Unchanged on exit.
75: *
76: * BETA - COMPLEX*16 .
77: * On entry, BETA specifies the scalar beta. When BETA is
78: * supplied as zero then Y need not be set on input.
79: * Unchanged on exit.
80: *
81: * Y - COMPLEX*16 array of DIMENSION at least
82: * ( 1 + ( m - 1 )*abs( INCY ) ) when TRANS = 'N' or 'n'
83: * and at least
84: * ( 1 + ( n - 1 )*abs( INCY ) ) otherwise.
85: * Before entry with BETA non-zero, the incremented array Y
86: * must contain the vector y. On exit, Y is overwritten by the
87: * updated vector y.
88: *
89: * INCY - INTEGER.
90: * On entry, INCY specifies the increment for the elements of
91: * Y. INCY must not be zero.
92: * Unchanged on exit.
93: *
94: * Further Details
95: * ===============
96: *
97: * Level 2 Blas routine.
98: * The vector and matrix arguments are not referenced when N = 0, or M = 0
99: *
100: * -- Written on 22-October-1986.
101: * Jack Dongarra, Argonne National Lab.
102: * Jeremy Du Croz, Nag Central Office.
103: * Sven Hammarling, Nag Central Office.
104: * Richard Hanson, Sandia National Labs.
105: *
106: * =====================================================================
107: *
108: * .. Parameters ..
109: DOUBLE COMPLEX ONE
110: PARAMETER (ONE= (1.0D+0,0.0D+0))
111: DOUBLE COMPLEX ZERO
112: PARAMETER (ZERO= (0.0D+0,0.0D+0))
113: * ..
114: * .. Local Scalars ..
115: DOUBLE COMPLEX TEMP
116: INTEGER I,INFO,IX,IY,J,JX,JY,KX,KY,LENX,LENY
117: LOGICAL NOCONJ
118: * ..
119: * .. External Functions ..
120: LOGICAL LSAME
121: EXTERNAL LSAME
122: * ..
123: * .. External Subroutines ..
124: EXTERNAL XERBLA
125: * ..
126: * .. Intrinsic Functions ..
127: INTRINSIC DCONJG,MAX
128: * ..
129: *
130: * Test the input parameters.
131: *
132: INFO = 0
133: IF (.NOT.LSAME(TRANS,'N') .AND. .NOT.LSAME(TRANS,'T') .AND.
134: + .NOT.LSAME(TRANS,'C')) THEN
135: INFO = 1
136: ELSE IF (M.LT.0) THEN
137: INFO = 2
138: ELSE IF (N.LT.0) THEN
139: INFO = 3
140: ELSE IF (LDA.LT.MAX(1,M)) THEN
141: INFO = 6
142: ELSE IF (INCX.EQ.0) THEN
143: INFO = 8
144: ELSE IF (INCY.EQ.0) THEN
145: INFO = 11
146: END IF
147: IF (INFO.NE.0) THEN
148: CALL XERBLA('ZGEMV ',INFO)
149: RETURN
150: END IF
151: *
152: * Quick return if possible.
153: *
154: IF ((M.EQ.0) .OR. (N.EQ.0) .OR.
155: + ((ALPHA.EQ.ZERO).AND. (BETA.EQ.ONE))) RETURN
156: *
157: NOCONJ = LSAME(TRANS,'T')
158: *
159: * Set LENX and LENY, the lengths of the vectors x and y, and set
160: * up the start points in X and Y.
161: *
162: IF (LSAME(TRANS,'N')) THEN
163: LENX = N
164: LENY = M
165: ELSE
166: LENX = M
167: LENY = N
168: END IF
169: IF (INCX.GT.0) THEN
170: KX = 1
171: ELSE
172: KX = 1 - (LENX-1)*INCX
173: END IF
174: IF (INCY.GT.0) THEN
175: KY = 1
176: ELSE
177: KY = 1 - (LENY-1)*INCY
178: END IF
179: *
180: * Start the operations. In this version the elements of A are
181: * accessed sequentially with one pass through A.
182: *
183: * First form y := beta*y.
184: *
185: IF (BETA.NE.ONE) THEN
186: IF (INCY.EQ.1) THEN
187: IF (BETA.EQ.ZERO) THEN
188: DO 10 I = 1,LENY
189: Y(I) = ZERO
190: 10 CONTINUE
191: ELSE
192: DO 20 I = 1,LENY
193: Y(I) = BETA*Y(I)
194: 20 CONTINUE
195: END IF
196: ELSE
197: IY = KY
198: IF (BETA.EQ.ZERO) THEN
199: DO 30 I = 1,LENY
200: Y(IY) = ZERO
201: IY = IY + INCY
202: 30 CONTINUE
203: ELSE
204: DO 40 I = 1,LENY
205: Y(IY) = BETA*Y(IY)
206: IY = IY + INCY
207: 40 CONTINUE
208: END IF
209: END IF
210: END IF
211: IF (ALPHA.EQ.ZERO) RETURN
212: IF (LSAME(TRANS,'N')) THEN
213: *
214: * Form y := alpha*A*x + y.
215: *
216: JX = KX
217: IF (INCY.EQ.1) THEN
218: DO 60 J = 1,N
219: IF (X(JX).NE.ZERO) THEN
220: TEMP = ALPHA*X(JX)
221: DO 50 I = 1,M
222: Y(I) = Y(I) + TEMP*A(I,J)
223: 50 CONTINUE
224: END IF
225: JX = JX + INCX
226: 60 CONTINUE
227: ELSE
228: DO 80 J = 1,N
229: IF (X(JX).NE.ZERO) THEN
230: TEMP = ALPHA*X(JX)
231: IY = KY
232: DO 70 I = 1,M
233: Y(IY) = Y(IY) + TEMP*A(I,J)
234: IY = IY + INCY
235: 70 CONTINUE
236: END IF
237: JX = JX + INCX
238: 80 CONTINUE
239: END IF
240: ELSE
241: *
242: * Form y := alpha*A**T*x + y or y := alpha*A**H*x + y.
243: *
244: JY = KY
245: IF (INCX.EQ.1) THEN
246: DO 110 J = 1,N
247: TEMP = ZERO
248: IF (NOCONJ) THEN
249: DO 90 I = 1,M
250: TEMP = TEMP + A(I,J)*X(I)
251: 90 CONTINUE
252: ELSE
253: DO 100 I = 1,M
254: TEMP = TEMP + DCONJG(A(I,J))*X(I)
255: 100 CONTINUE
256: END IF
257: Y(JY) = Y(JY) + ALPHA*TEMP
258: JY = JY + INCY
259: 110 CONTINUE
260: ELSE
261: DO 140 J = 1,N
262: TEMP = ZERO
263: IX = KX
264: IF (NOCONJ) THEN
265: DO 120 I = 1,M
266: TEMP = TEMP + A(I,J)*X(IX)
267: IX = IX + INCX
268: 120 CONTINUE
269: ELSE
270: DO 130 I = 1,M
271: TEMP = TEMP + DCONJG(A(I,J))*X(IX)
272: IX = IX + INCX
273: 130 CONTINUE
274: END IF
275: Y(JY) = Y(JY) + ALPHA*TEMP
276: JY = JY + INCY
277: 140 CONTINUE
278: END IF
279: END IF
280: *
281: RETURN
282: *
283: * End of ZGEMV .
284: *
285: END
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