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LAPACK 3.3.1
Linear Algebra PACKage
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LAPACK 3.3.1
Linear Algebra PACKage
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00001 SUBROUTINE CHER2(UPLO,N,ALPHA,X,INCX,Y,INCY,A,LDA) 00002 * .. Scalar Arguments .. 00003 COMPLEX ALPHA 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 * CHER2 performs the hermitian rank 2 operation 00015 * 00016 * A := alpha*x*y**H + conjg( alpha )*y*x**H + A, 00017 * 00018 * where alpha is a scalar, x and y are n element vectors and A is an n 00019 * 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 * X - COMPLEX array of dimension at least 00047 * ( 1 + ( n - 1 )*abs( INCX ) ). 00048 * Before entry, the incremented array X must contain the n 00049 * element vector x. 00050 * Unchanged on exit. 00051 * 00052 * INCX - INTEGER. 00053 * On entry, INCX specifies the increment for the elements of 00054 * X. INCX must not be zero. 00055 * Unchanged on exit. 00056 * 00057 * Y - COMPLEX array of dimension at least 00058 * ( 1 + ( n - 1 )*abs( INCY ) ). 00059 * Before entry, the incremented array Y must contain the n 00060 * element vector y. 00061 * Unchanged on exit. 00062 * 00063 * INCY - INTEGER. 00064 * On entry, INCY specifies the increment for the elements of 00065 * Y. INCY must not be zero. 00066 * Unchanged on exit. 00067 * 00068 * A - COMPLEX array of DIMENSION ( LDA, n ). 00069 * Before entry with UPLO = 'U' or 'u', the leading n by n 00070 * upper triangular part of the array A must contain the upper 00071 * triangular part of the hermitian matrix and the strictly 00072 * lower triangular part of A is not referenced. On exit, the 00073 * upper triangular part of the array A is overwritten by the 00074 * upper triangular part of the updated matrix. 00075 * Before entry with UPLO = 'L' or 'l', the leading n by n 00076 * lower triangular part of the array A must contain the lower 00077 * triangular part of the hermitian matrix and the strictly 00078 * upper triangular part of A is not referenced. On exit, the 00079 * lower triangular part of the array A is overwritten by the 00080 * lower triangular part of the updated matrix. 00081 * Note that the imaginary parts of the diagonal elements need 00082 * not be set, they are assumed to be zero, and on exit they 00083 * are set to zero. 00084 * 00085 * LDA - INTEGER. 00086 * On entry, LDA specifies the first dimension of A as declared 00087 * in the calling (sub) program. LDA must be at least 00088 * max( 1, n ). 00089 * Unchanged on exit. 00090 * 00091 * Further Details 00092 * =============== 00093 * 00094 * Level 2 Blas routine. 00095 * 00096 * -- Written on 22-October-1986. 00097 * Jack Dongarra, Argonne National Lab. 00098 * Jeremy Du Croz, Nag Central Office. 00099 * Sven Hammarling, Nag Central Office. 00100 * Richard Hanson, Sandia National Labs. 00101 * 00102 * ===================================================================== 00103 * 00104 * .. Parameters .. 00105 COMPLEX ZERO 00106 PARAMETER (ZERO= (0.0E+0,0.0E+0)) 00107 * .. 00108 * .. Local Scalars .. 00109 COMPLEX TEMP1,TEMP2 00110 INTEGER I,INFO,IX,IY,J,JX,JY,KX,KY 00111 * .. 00112 * .. External Functions .. 00113 LOGICAL LSAME 00114 EXTERNAL LSAME 00115 * .. 00116 * .. External Subroutines .. 00117 EXTERNAL XERBLA 00118 * .. 00119 * .. Intrinsic Functions .. 00120 INTRINSIC CONJG,MAX,REAL 00121 * .. 00122 * 00123 * Test the input parameters. 00124 * 00125 INFO = 0 00126 IF (.NOT.LSAME(UPLO,'U') .AND. .NOT.LSAME(UPLO,'L')) THEN 00127 INFO = 1 00128 ELSE IF (N.LT.0) THEN 00129 INFO = 2 00130 ELSE IF (INCX.EQ.0) THEN 00131 INFO = 5 00132 ELSE IF (INCY.EQ.0) THEN 00133 INFO = 7 00134 ELSE IF (LDA.LT.MAX(1,N)) THEN 00135 INFO = 9 00136 END IF 00137 IF (INFO.NE.0) THEN 00138 CALL XERBLA('CHER2 ',INFO) 00139 RETURN 00140 END IF 00141 * 00142 * Quick return if possible. 00143 * 00144 IF ((N.EQ.0) .OR. (ALPHA.EQ.ZERO)) RETURN 00145 * 00146 * Set up the start points in X and Y if the increments are not both 00147 * unity. 00148 * 00149 IF ((INCX.NE.1) .OR. (INCY.NE.1)) THEN 00150 IF (INCX.GT.0) THEN 00151 KX = 1 00152 ELSE 00153 KX = 1 - (N-1)*INCX 00154 END IF 00155 IF (INCY.GT.0) THEN 00156 KY = 1 00157 ELSE 00158 KY = 1 - (N-1)*INCY 00159 END IF 00160 JX = KX 00161 JY = KY 00162 END IF 00163 * 00164 * Start the operations. In this version the elements of A are 00165 * accessed sequentially with one pass through the triangular part 00166 * of A. 00167 * 00168 IF (LSAME(UPLO,'U')) THEN 00169 * 00170 * Form A when A is stored in the upper triangle. 00171 * 00172 IF ((INCX.EQ.1) .AND. (INCY.EQ.1)) THEN 00173 DO 20 J = 1,N 00174 IF ((X(J).NE.ZERO) .OR. (Y(J).NE.ZERO)) THEN 00175 TEMP1 = ALPHA*CONJG(Y(J)) 00176 TEMP2 = CONJG(ALPHA*X(J)) 00177 DO 10 I = 1,J - 1 00178 A(I,J) = A(I,J) + X(I)*TEMP1 + Y(I)*TEMP2 00179 10 CONTINUE 00180 A(J,J) = REAL(A(J,J)) + 00181 + REAL(X(J)*TEMP1+Y(J)*TEMP2) 00182 ELSE 00183 A(J,J) = REAL(A(J,J)) 00184 END IF 00185 20 CONTINUE 00186 ELSE 00187 DO 40 J = 1,N 00188 IF ((X(JX).NE.ZERO) .OR. (Y(JY).NE.ZERO)) THEN 00189 TEMP1 = ALPHA*CONJG(Y(JY)) 00190 TEMP2 = CONJG(ALPHA*X(JX)) 00191 IX = KX 00192 IY = KY 00193 DO 30 I = 1,J - 1 00194 A(I,J) = A(I,J) + X(IX)*TEMP1 + Y(IY)*TEMP2 00195 IX = IX + INCX 00196 IY = IY + INCY 00197 30 CONTINUE 00198 A(J,J) = REAL(A(J,J)) + 00199 + REAL(X(JX)*TEMP1+Y(JY)*TEMP2) 00200 ELSE 00201 A(J,J) = REAL(A(J,J)) 00202 END IF 00203 JX = JX + INCX 00204 JY = JY + INCY 00205 40 CONTINUE 00206 END IF 00207 ELSE 00208 * 00209 * Form A when A is stored in the lower triangle. 00210 * 00211 IF ((INCX.EQ.1) .AND. (INCY.EQ.1)) THEN 00212 DO 60 J = 1,N 00213 IF ((X(J).NE.ZERO) .OR. (Y(J).NE.ZERO)) THEN 00214 TEMP1 = ALPHA*CONJG(Y(J)) 00215 TEMP2 = CONJG(ALPHA*X(J)) 00216 A(J,J) = REAL(A(J,J)) + 00217 + REAL(X(J)*TEMP1+Y(J)*TEMP2) 00218 DO 50 I = J + 1,N 00219 A(I,J) = A(I,J) + X(I)*TEMP1 + Y(I)*TEMP2 00220 50 CONTINUE 00221 ELSE 00222 A(J,J) = REAL(A(J,J)) 00223 END IF 00224 60 CONTINUE 00225 ELSE 00226 DO 80 J = 1,N 00227 IF ((X(JX).NE.ZERO) .OR. (Y(JY).NE.ZERO)) THEN 00228 TEMP1 = ALPHA*CONJG(Y(JY)) 00229 TEMP2 = CONJG(ALPHA*X(JX)) 00230 A(J,J) = REAL(A(J,J)) + 00231 + REAL(X(JX)*TEMP1+Y(JY)*TEMP2) 00232 IX = JX 00233 IY = JY 00234 DO 70 I = J + 1,N 00235 IX = IX + INCX 00236 IY = IY + INCY 00237 A(I,J) = A(I,J) + X(IX)*TEMP1 + Y(IY)*TEMP2 00238 70 CONTINUE 00239 ELSE 00240 A(J,J) = REAL(A(J,J)) 00241 END IF 00242 JX = JX + INCX 00243 JY = JY + INCY 00244 80 CONTINUE 00245 END IF 00246 END IF 00247 * 00248 RETURN 00249 * 00250 * End of CHER2 . 00251 * 00252 END
1.7.3 
