| 1 | SUBROUTINE SGER(M,N,ALPHA,X,INCX,Y,INCY,A,LDA) |
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| 2 | * .. Scalar Arguments .. |
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| 3 | REAL ALPHA |
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| 4 | INTEGER INCX,INCY,LDA,M,N |
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| 5 | * .. |
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| 6 | * .. Array Arguments .. |
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| 7 | REAL A(LDA,*),X(*),Y(*) |
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| 8 | * .. |
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| 9 | * |
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| 10 | * Purpose |
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| 11 | * ======= |
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| 12 | * |
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| 13 | * SGER performs the rank 1 operation |
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| 14 | * |
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| 15 | * A := alpha*x*y' + A, |
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| 16 | * |
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| 17 | * where alpha is a scalar, x is an m element vector, y is an n element |
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| 18 | * vector and A is an m by n matrix. |
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| 19 | * |
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| 20 | * Arguments |
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| 21 | * ========== |
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| 22 | * |
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| 23 | * M - INTEGER. |
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| 24 | * On entry, M specifies the number of rows of the matrix A. |
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| 25 | * M must be at least zero. |
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| 26 | * Unchanged on exit. |
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| 27 | * |
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| 28 | * N - INTEGER. |
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| 29 | * On entry, N specifies the number of columns of the matrix A. |
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| 30 | * N must be at least zero. |
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| 31 | * Unchanged on exit. |
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| 32 | * |
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| 33 | * ALPHA - REAL . |
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| 34 | * On entry, ALPHA specifies the scalar alpha. |
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| 35 | * Unchanged on exit. |
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| 36 | * |
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| 37 | * X - REAL array of dimension at least |
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| 38 | * ( 1 + ( m - 1 )*abs( INCX ) ). |
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| 39 | * Before entry, the incremented array X must contain the m |
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| 40 | * element vector x. |
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| 41 | * Unchanged on exit. |
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| 42 | * |
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| 43 | * INCX - INTEGER. |
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| 44 | * On entry, INCX specifies the increment for the elements of |
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| 45 | * X. INCX must not be zero. |
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| 46 | * Unchanged on exit. |
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| 47 | * |
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| 48 | * Y - REAL array of dimension at least |
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| 49 | * ( 1 + ( n - 1 )*abs( INCY ) ). |
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| 50 | * Before entry, the incremented array Y must contain the n |
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| 51 | * element vector y. |
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| 52 | * Unchanged on exit. |
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| 53 | * |
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| 54 | * INCY - INTEGER. |
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| 55 | * On entry, INCY specifies the increment for the elements of |
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| 56 | * Y. INCY must not be zero. |
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| 57 | * Unchanged on exit. |
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| 58 | * |
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| 59 | * A - REAL array of DIMENSION ( LDA, n ). |
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| 60 | * Before entry, the leading m by n part of the array A must |
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| 61 | * contain the matrix of coefficients. On exit, A is |
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| 62 | * overwritten by the updated matrix. |
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| 63 | * |
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| 64 | * LDA - INTEGER. |
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| 65 | * On entry, LDA specifies the first dimension of A as declared |
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| 66 | * in the calling (sub) program. LDA must be at least |
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| 67 | * max( 1, m ). |
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| 68 | * Unchanged on exit. |
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| 69 | * |
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| 70 | * |
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| 71 | * Level 2 Blas routine. |
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| 72 | * |
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| 73 | * -- Written on 22-October-1986. |
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| 74 | * Jack Dongarra, Argonne National Lab. |
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| 75 | * Jeremy Du Croz, Nag Central Office. |
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| 76 | * Sven Hammarling, Nag Central Office. |
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| 77 | * Richard Hanson, Sandia National Labs. |
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| 78 | * |
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| 79 | * |
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| 80 | * .. Parameters .. |
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| 81 | REAL ZERO |
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| 82 | PARAMETER (ZERO=0.0E+0) |
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| 83 | * .. |
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| 84 | * .. Local Scalars .. |
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| 85 | REAL TEMP |
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| 86 | INTEGER I,INFO,IX,J,JY,KX |
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| 87 | * .. |
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| 88 | * .. External Subroutines .. |
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| 89 | EXTERNAL XERBLA |
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| 90 | * .. |
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| 91 | * .. Intrinsic Functions .. |
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| 92 | INTRINSIC MAX |
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| 93 | * .. |
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| 94 | * |
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| 95 | * Test the input parameters. |
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| 96 | * |
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| 97 | INFO = 0 |
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| 98 | IF (M.LT.0) THEN |
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| 99 | INFO = 1 |
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| 100 | ELSE IF (N.LT.0) THEN |
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| 101 | INFO = 2 |
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| 102 | ELSE IF (INCX.EQ.0) THEN |
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| 103 | INFO = 5 |
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| 104 | ELSE IF (INCY.EQ.0) THEN |
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| 105 | INFO = 7 |
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| 106 | ELSE IF (LDA.LT.MAX(1,M)) THEN |
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| 107 | INFO = 9 |
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| 108 | END IF |
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| 109 | IF (INFO.NE.0) THEN |
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| 110 | CALL XERBLA('SGER ',INFO) |
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| 111 | RETURN |
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| 112 | END IF |
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| 113 | * |
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| 114 | * Quick return if possible. |
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| 115 | * |
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| 116 | IF ((M.EQ.0) .OR. (N.EQ.0) .OR. (ALPHA.EQ.ZERO)) RETURN |
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| 117 | * |
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| 118 | * Start the operations. In this version the elements of A are |
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| 119 | * accessed sequentially with one pass through A. |
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| 120 | * |
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| 121 | IF (INCY.GT.0) THEN |
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| 122 | JY = 1 |
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| 123 | ELSE |
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| 124 | JY = 1 - (N-1)*INCY |
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| 125 | END IF |
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| 126 | IF (INCX.EQ.1) THEN |
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| 127 | DO 20 J = 1,N |
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| 128 | IF (Y(JY).NE.ZERO) THEN |
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| 129 | TEMP = ALPHA*Y(JY) |
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| 130 | DO 10 I = 1,M |
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| 131 | A(I,J) = A(I,J) + X(I)*TEMP |
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| 132 | 10 CONTINUE |
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| 133 | END IF |
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| 134 | JY = JY + INCY |
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| 135 | 20 CONTINUE |
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| 136 | ELSE |
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| 137 | IF (INCX.GT.0) THEN |
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| 138 | KX = 1 |
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| 139 | ELSE |
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| 140 | KX = 1 - (M-1)*INCX |
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| 141 | END IF |
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| 142 | DO 40 J = 1,N |
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| 143 | IF (Y(JY).NE.ZERO) THEN |
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| 144 | TEMP = ALPHA*Y(JY) |
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| 145 | IX = KX |
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| 146 | DO 30 I = 1,M |
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| 147 | A(I,J) = A(I,J) + X(IX)*TEMP |
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| 148 | IX = IX + INCX |
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| 149 | 30 CONTINUE |
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| 150 | END IF |
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| 151 | JY = JY + INCY |
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| 152 | 40 CONTINUE |
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| 153 | END IF |
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| 154 | * |
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| 155 | RETURN |
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| 156 | * |
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| 157 | * End of SGER . |
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| 158 | * |
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| 159 | END |
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