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LAPACK 3.3.0
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LAPACK 3.3.0
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00001 SUBROUTINE SSPR2(UPLO,N,ALPHA,X,INCX,Y,INCY,AP) 00002 * .. Scalar Arguments .. 00003 REAL ALPHA 00004 INTEGER INCX,INCY,N 00005 CHARACTER UPLO 00006 * .. 00007 * .. Array Arguments .. 00008 REAL AP(*),X(*),Y(*) 00009 * .. 00010 * 00011 * Purpose 00012 * ======= 00013 * 00014 * SSPR2 performs the symmetric rank 2 operation 00015 * 00016 * A := alpha*x*y' + alpha*y*x' + A, 00017 * 00018 * where alpha is a scalar, x and y are n element vectors and A is an 00019 * n by n symmetric matrix, supplied in packed form. 00020 * 00021 * Arguments 00022 * ========== 00023 * 00024 * UPLO - CHARACTER*1. 00025 * On entry, UPLO specifies whether the upper or lower 00026 * triangular part of the matrix A is supplied in the packed 00027 * array AP as follows: 00028 * 00029 * UPLO = 'U' or 'u' The upper triangular part of A is 00030 * supplied in AP. 00031 * 00032 * UPLO = 'L' or 'l' The lower triangular part of A is 00033 * supplied in AP. 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 - REAL . 00043 * On entry, ALPHA specifies the scalar alpha. 00044 * Unchanged on exit. 00045 * 00046 * X - REAL 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 - REAL 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 * AP - REAL array of DIMENSION at least 00069 * ( ( n*( n + 1 ) )/2 ). 00070 * Before entry with UPLO = 'U' or 'u', the array AP must 00071 * contain the upper triangular part of the symmetric matrix 00072 * packed sequentially, column by column, so that AP( 1 ) 00073 * contains a( 1, 1 ), AP( 2 ) and AP( 3 ) contain a( 1, 2 ) 00074 * and a( 2, 2 ) respectively, and so on. On exit, the array 00075 * AP is overwritten by the upper triangular part of the 00076 * updated matrix. 00077 * Before entry with UPLO = 'L' or 'l', the array AP must 00078 * contain the lower triangular part of the symmetric matrix 00079 * packed sequentially, column by column, so that AP( 1 ) 00080 * contains a( 1, 1 ), AP( 2 ) and AP( 3 ) contain a( 2, 1 ) 00081 * and a( 3, 1 ) respectively, and so on. On exit, the array 00082 * AP is overwritten by the lower triangular part of the 00083 * updated matrix. 00084 * 00085 * Further Details 00086 * =============== 00087 * 00088 * Level 2 Blas routine. 00089 * 00090 * -- Written on 22-October-1986. 00091 * Jack Dongarra, Argonne National Lab. 00092 * Jeremy Du Croz, Nag Central Office. 00093 * Sven Hammarling, Nag Central Office. 00094 * Richard Hanson, Sandia National Labs. 00095 * 00096 * ===================================================================== 00097 * 00098 * .. Parameters .. 00099 REAL ZERO 00100 PARAMETER (ZERO=0.0E+0) 00101 * .. 00102 * .. Local Scalars .. 00103 REAL TEMP1,TEMP2 00104 INTEGER I,INFO,IX,IY,J,JX,JY,K,KK,KX,KY 00105 * .. 00106 * .. External Functions .. 00107 LOGICAL LSAME 00108 EXTERNAL LSAME 00109 * .. 00110 * .. External Subroutines .. 00111 EXTERNAL XERBLA 00112 * .. 00113 * 00114 * Test the input parameters. 00115 * 00116 INFO = 0 00117 IF (.NOT.LSAME(UPLO,'U') .AND. .NOT.LSAME(UPLO,'L')) THEN 00118 INFO = 1 00119 ELSE IF (N.LT.0) THEN 00120 INFO = 2 00121 ELSE IF (INCX.EQ.0) THEN 00122 INFO = 5 00123 ELSE IF (INCY.EQ.0) THEN 00124 INFO = 7 00125 END IF 00126 IF (INFO.NE.0) THEN 00127 CALL XERBLA('SSPR2 ',INFO) 00128 RETURN 00129 END IF 00130 * 00131 * Quick return if possible. 00132 * 00133 IF ((N.EQ.0) .OR. (ALPHA.EQ.ZERO)) RETURN 00134 * 00135 * Set up the start points in X and Y if the increments are not both 00136 * unity. 00137 * 00138 IF ((INCX.NE.1) .OR. (INCY.NE.1)) THEN 00139 IF (INCX.GT.0) THEN 00140 KX = 1 00141 ELSE 00142 KX = 1 - (N-1)*INCX 00143 END IF 00144 IF (INCY.GT.0) THEN 00145 KY = 1 00146 ELSE 00147 KY = 1 - (N-1)*INCY 00148 END IF 00149 JX = KX 00150 JY = KY 00151 END IF 00152 * 00153 * Start the operations. In this version the elements of the array AP 00154 * are accessed sequentially with one pass through AP. 00155 * 00156 KK = 1 00157 IF (LSAME(UPLO,'U')) THEN 00158 * 00159 * Form A when upper triangle is stored in AP. 00160 * 00161 IF ((INCX.EQ.1) .AND. (INCY.EQ.1)) THEN 00162 DO 20 J = 1,N 00163 IF ((X(J).NE.ZERO) .OR. (Y(J).NE.ZERO)) THEN 00164 TEMP1 = ALPHA*Y(J) 00165 TEMP2 = ALPHA*X(J) 00166 K = KK 00167 DO 10 I = 1,J 00168 AP(K) = AP(K) + X(I)*TEMP1 + Y(I)*TEMP2 00169 K = K + 1 00170 10 CONTINUE 00171 END IF 00172 KK = KK + J 00173 20 CONTINUE 00174 ELSE 00175 DO 40 J = 1,N 00176 IF ((X(JX).NE.ZERO) .OR. (Y(JY).NE.ZERO)) THEN 00177 TEMP1 = ALPHA*Y(JY) 00178 TEMP2 = ALPHA*X(JX) 00179 IX = KX 00180 IY = KY 00181 DO 30 K = KK,KK + J - 1 00182 AP(K) = AP(K) + X(IX)*TEMP1 + Y(IY)*TEMP2 00183 IX = IX + INCX 00184 IY = IY + INCY 00185 30 CONTINUE 00186 END IF 00187 JX = JX + INCX 00188 JY = JY + INCY 00189 KK = KK + J 00190 40 CONTINUE 00191 END IF 00192 ELSE 00193 * 00194 * Form A when lower triangle is stored in AP. 00195 * 00196 IF ((INCX.EQ.1) .AND. (INCY.EQ.1)) THEN 00197 DO 60 J = 1,N 00198 IF ((X(J).NE.ZERO) .OR. (Y(J).NE.ZERO)) THEN 00199 TEMP1 = ALPHA*Y(J) 00200 TEMP2 = ALPHA*X(J) 00201 K = KK 00202 DO 50 I = J,N 00203 AP(K) = AP(K) + X(I)*TEMP1 + Y(I)*TEMP2 00204 K = K + 1 00205 50 CONTINUE 00206 END IF 00207 KK = KK + N - J + 1 00208 60 CONTINUE 00209 ELSE 00210 DO 80 J = 1,N 00211 IF ((X(JX).NE.ZERO) .OR. (Y(JY).NE.ZERO)) THEN 00212 TEMP1 = ALPHA*Y(JY) 00213 TEMP2 = ALPHA*X(JX) 00214 IX = JX 00215 IY = JY 00216 DO 70 K = KK,KK + N - J 00217 AP(K) = AP(K) + X(IX)*TEMP1 + Y(IY)*TEMP2 00218 IX = IX + INCX 00219 IY = IY + INCY 00220 70 CONTINUE 00221 END IF 00222 JX = JX + INCX 00223 JY = JY + INCY 00224 KK = KK + N - J + 1 00225 80 CONTINUE 00226 END IF 00227 END IF 00228 * 00229 RETURN 00230 * 00231 * End of SSPR2 . 00232 * 00233 END
1.7.3 
