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LAPACK 3.3.0
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LAPACK 3.3.0
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00001 SUBROUTINE CHEMV(UPLO,N,ALPHA,A,LDA,X,INCX,BETA,Y,INCY) 00002 * .. Scalar Arguments .. 00003 COMPLEX ALPHA,BETA 00004 INTEGER INCX,INCY,LDA,N 00005 CHARACTER UPLO 00006 * .. 00007 * .. Array Arguments .. 00008 COMPLEX A(LDA,*),X(*),Y(*) 00009 * .. 00010 * 00011 * Purpose 00012 * ======= 00013 * 00014 * CHEMV performs the matrix-vector operation 00015 * 00016 * y := alpha*A*x + beta*y, 00017 * 00018 * where alpha and beta are scalars, x and y are n element vectors and 00019 * A is an n by n hermitian matrix. 00020 * 00021 * Arguments 00022 * ========== 00023 * 00024 * UPLO - CHARACTER*1. 00025 * On entry, UPLO specifies whether the upper or lower 00026 * triangular part of the array A is to be referenced as 00027 * follows: 00028 * 00029 * UPLO = 'U' or 'u' Only the upper triangular part of A 00030 * is to be referenced. 00031 * 00032 * UPLO = 'L' or 'l' Only the lower triangular part of A 00033 * is to be referenced. 00034 * 00035 * Unchanged on exit. 00036 * 00037 * N - INTEGER. 00038 * On entry, N specifies the order of the matrix A. 00039 * N must be at least zero. 00040 * Unchanged on exit. 00041 * 00042 * ALPHA - COMPLEX . 00043 * On entry, ALPHA specifies the scalar alpha. 00044 * Unchanged on exit. 00045 * 00046 * A - COMPLEX array of DIMENSION ( LDA, n ). 00047 * Before entry with UPLO = 'U' or 'u', the leading n by n 00048 * upper triangular part of the array A must contain the upper 00049 * triangular part of the hermitian matrix and the strictly 00050 * lower triangular part of A is not referenced. 00051 * Before entry with UPLO = 'L' or 'l', the leading n by n 00052 * lower triangular part of the array A must contain the lower 00053 * triangular part of the hermitian matrix and the strictly 00054 * upper triangular part of A is not referenced. 00055 * Note that the imaginary parts of the diagonal elements need 00056 * not be set and are assumed to be zero. 00057 * Unchanged on exit. 00058 * 00059 * LDA - INTEGER. 00060 * On entry, LDA specifies the first dimension of A as declared 00061 * in the calling (sub) program. LDA must be at least 00062 * max( 1, n ). 00063 * Unchanged on exit. 00064 * 00065 * X - COMPLEX array of dimension at least 00066 * ( 1 + ( n - 1 )*abs( INCX ) ). 00067 * Before entry, the incremented array X must contain the n 00068 * element vector x. 00069 * Unchanged on exit. 00070 * 00071 * INCX - INTEGER. 00072 * On entry, INCX specifies the increment for the elements of 00073 * X. INCX must not be zero. 00074 * Unchanged on exit. 00075 * 00076 * BETA - COMPLEX . 00077 * On entry, BETA specifies the scalar beta. When BETA is 00078 * supplied as zero then Y need not be set on input. 00079 * Unchanged on exit. 00080 * 00081 * Y - COMPLEX array of dimension at least 00082 * ( 1 + ( n - 1 )*abs( INCY ) ). 00083 * Before entry, the incremented array Y must contain the n 00084 * element vector y. On exit, Y is overwritten by the updated 00085 * vector y. 00086 * 00087 * INCY - INTEGER. 00088 * On entry, INCY specifies the increment for the elements of 00089 * Y. INCY must not be zero. 00090 * Unchanged on exit. 00091 * 00092 * Further Details 00093 * =============== 00094 * 00095 * Level 2 Blas routine. 00096 * 00097 * -- Written on 22-October-1986. 00098 * Jack Dongarra, Argonne National Lab. 00099 * Jeremy Du Croz, Nag Central Office. 00100 * Sven Hammarling, Nag Central Office. 00101 * Richard Hanson, Sandia National Labs. 00102 * 00103 * ===================================================================== 00104 * 00105 * .. Parameters .. 00106 COMPLEX ONE 00107 PARAMETER (ONE= (1.0E+0,0.0E+0)) 00108 COMPLEX ZERO 00109 PARAMETER (ZERO= (0.0E+0,0.0E+0)) 00110 * .. 00111 * .. Local Scalars .. 00112 COMPLEX TEMP1,TEMP2 00113 INTEGER I,INFO,IX,IY,J,JX,JY,KX,KY 00114 * .. 00115 * .. External Functions .. 00116 LOGICAL LSAME 00117 EXTERNAL LSAME 00118 * .. 00119 * .. External Subroutines .. 00120 EXTERNAL XERBLA 00121 * .. 00122 * .. Intrinsic Functions .. 00123 INTRINSIC CONJG,MAX,REAL 00124 * .. 00125 * 00126 * Test the input parameters. 00127 * 00128 INFO = 0 00129 IF (.NOT.LSAME(UPLO,'U') .AND. .NOT.LSAME(UPLO,'L')) THEN 00130 INFO = 1 00131 ELSE IF (N.LT.0) THEN 00132 INFO = 2 00133 ELSE IF (LDA.LT.MAX(1,N)) THEN 00134 INFO = 5 00135 ELSE IF (INCX.EQ.0) THEN 00136 INFO = 7 00137 ELSE IF (INCY.EQ.0) THEN 00138 INFO = 10 00139 END IF 00140 IF (INFO.NE.0) THEN 00141 CALL XERBLA('CHEMV ',INFO) 00142 RETURN 00143 END IF 00144 * 00145 * Quick return if possible. 00146 * 00147 IF ((N.EQ.0) .OR. ((ALPHA.EQ.ZERO).AND. (BETA.EQ.ONE))) RETURN 00148 * 00149 * Set up the start points in X and Y. 00150 * 00151 IF (INCX.GT.0) THEN 00152 KX = 1 00153 ELSE 00154 KX = 1 - (N-1)*INCX 00155 END IF 00156 IF (INCY.GT.0) THEN 00157 KY = 1 00158 ELSE 00159 KY = 1 - (N-1)*INCY 00160 END IF 00161 * 00162 * Start the operations. In this version the elements of A are 00163 * accessed sequentially with one pass through the triangular part 00164 * of A. 00165 * 00166 * First form y := beta*y. 00167 * 00168 IF (BETA.NE.ONE) THEN 00169 IF (INCY.EQ.1) THEN 00170 IF (BETA.EQ.ZERO) THEN 00171 DO 10 I = 1,N 00172 Y(I) = ZERO 00173 10 CONTINUE 00174 ELSE 00175 DO 20 I = 1,N 00176 Y(I) = BETA*Y(I) 00177 20 CONTINUE 00178 END IF 00179 ELSE 00180 IY = KY 00181 IF (BETA.EQ.ZERO) THEN 00182 DO 30 I = 1,N 00183 Y(IY) = ZERO 00184 IY = IY + INCY 00185 30 CONTINUE 00186 ELSE 00187 DO 40 I = 1,N 00188 Y(IY) = BETA*Y(IY) 00189 IY = IY + INCY 00190 40 CONTINUE 00191 END IF 00192 END IF 00193 END IF 00194 IF (ALPHA.EQ.ZERO) RETURN 00195 IF (LSAME(UPLO,'U')) THEN 00196 * 00197 * Form y when A is stored in upper triangle. 00198 * 00199 IF ((INCX.EQ.1) .AND. (INCY.EQ.1)) THEN 00200 DO 60 J = 1,N 00201 TEMP1 = ALPHA*X(J) 00202 TEMP2 = ZERO 00203 DO 50 I = 1,J - 1 00204 Y(I) = Y(I) + TEMP1*A(I,J) 00205 TEMP2 = TEMP2 + CONJG(A(I,J))*X(I) 00206 50 CONTINUE 00207 Y(J) = Y(J) + TEMP1*REAL(A(J,J)) + ALPHA*TEMP2 00208 60 CONTINUE 00209 ELSE 00210 JX = KX 00211 JY = KY 00212 DO 80 J = 1,N 00213 TEMP1 = ALPHA*X(JX) 00214 TEMP2 = ZERO 00215 IX = KX 00216 IY = KY 00217 DO 70 I = 1,J - 1 00218 Y(IY) = Y(IY) + TEMP1*A(I,J) 00219 TEMP2 = TEMP2 + CONJG(A(I,J))*X(IX) 00220 IX = IX + INCX 00221 IY = IY + INCY 00222 70 CONTINUE 00223 Y(JY) = Y(JY) + TEMP1*REAL(A(J,J)) + ALPHA*TEMP2 00224 JX = JX + INCX 00225 JY = JY + INCY 00226 80 CONTINUE 00227 END IF 00228 ELSE 00229 * 00230 * Form y when A is stored in lower triangle. 00231 * 00232 IF ((INCX.EQ.1) .AND. (INCY.EQ.1)) THEN 00233 DO 100 J = 1,N 00234 TEMP1 = ALPHA*X(J) 00235 TEMP2 = ZERO 00236 Y(J) = Y(J) + TEMP1*REAL(A(J,J)) 00237 DO 90 I = J + 1,N 00238 Y(I) = Y(I) + TEMP1*A(I,J) 00239 TEMP2 = TEMP2 + CONJG(A(I,J))*X(I) 00240 90 CONTINUE 00241 Y(J) = Y(J) + ALPHA*TEMP2 00242 100 CONTINUE 00243 ELSE 00244 JX = KX 00245 JY = KY 00246 DO 120 J = 1,N 00247 TEMP1 = ALPHA*X(JX) 00248 TEMP2 = ZERO 00249 Y(JY) = Y(JY) + TEMP1*REAL(A(J,J)) 00250 IX = JX 00251 IY = JY 00252 DO 110 I = J + 1,N 00253 IX = IX + INCX 00254 IY = IY + INCY 00255 Y(IY) = Y(IY) + TEMP1*A(I,J) 00256 TEMP2 = TEMP2 + CONJG(A(I,J))*X(IX) 00257 110 CONTINUE 00258 Y(JY) = Y(JY) + ALPHA*TEMP2 00259 JX = JX + INCX 00260 JY = JY + INCY 00261 120 CONTINUE 00262 END IF 00263 END IF 00264 * 00265 RETURN 00266 * 00267 * End of CHEMV . 00268 * 00269 END
1.7.3 
