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LAPACK
3.4.1
LAPACK: Linear Algebra PACKage
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00001 *> \brief \b SAXPY 00002 * 00003 * =========== DOCUMENTATION =========== 00004 * 00005 * Online html documentation available at 00006 * http://www.netlib.org/lapack/explore-html/ 00007 * 00008 * Definition: 00009 * =========== 00010 * 00011 * SUBROUTINE SAXPY(N,SA,SX,INCX,SY,INCY) 00012 * 00013 * .. Scalar Arguments .. 00014 * REAL SA 00015 * INTEGER INCX,INCY,N 00016 * .. 00017 * .. Array Arguments .. 00018 * REAL SX(*),SY(*) 00019 * .. 00020 * 00021 * 00022 *> \par Purpose: 00023 * ============= 00024 *> 00025 *> \verbatim 00026 *> 00027 *> SAXPY constant times a vector plus a vector. 00028 *> uses unrolled loops for increments equal to one. 00029 *> \endverbatim 00030 * 00031 * Authors: 00032 * ======== 00033 * 00034 *> \author Univ. of Tennessee 00035 *> \author Univ. of California Berkeley 00036 *> \author Univ. of Colorado Denver 00037 *> \author NAG Ltd. 00038 * 00039 *> \date November 2011 00040 * 00041 *> \ingroup single_blas_level1 00042 * 00043 *> \par Further Details: 00044 * ===================== 00045 *> 00046 *> \verbatim 00047 *> 00048 *> jack dongarra, linpack, 3/11/78. 00049 *> modified 12/3/93, array(1) declarations changed to array(*) 00050 *> \endverbatim 00051 *> 00052 * ===================================================================== 00053 SUBROUTINE SAXPY(N,SA,SX,INCX,SY,INCY) 00054 * 00055 * -- Reference BLAS level1 routine (version 3.4.0) -- 00056 * -- Reference BLAS is a software package provided by Univ. of Tennessee, -- 00057 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- 00058 * November 2011 00059 * 00060 * .. Scalar Arguments .. 00061 REAL SA 00062 INTEGER INCX,INCY,N 00063 * .. 00064 * .. Array Arguments .. 00065 REAL SX(*),SY(*) 00066 * .. 00067 * 00068 * ===================================================================== 00069 * 00070 * .. Local Scalars .. 00071 INTEGER I,IX,IY,M,MP1 00072 * .. 00073 * .. Intrinsic Functions .. 00074 INTRINSIC MOD 00075 * .. 00076 IF (N.LE.0) RETURN 00077 IF (SA.EQ.0.0) RETURN 00078 IF (INCX.EQ.1 .AND. INCY.EQ.1) THEN 00079 * 00080 * code for both increments equal to 1 00081 * 00082 * 00083 * clean-up loop 00084 * 00085 M = MOD(N,4) 00086 IF (M.NE.0) THEN 00087 DO I = 1,M 00088 SY(I) = SY(I) + SA*SX(I) 00089 END DO 00090 END IF 00091 IF (N.LT.4) RETURN 00092 MP1 = M + 1 00093 DO I = MP1,N,4 00094 SY(I) = SY(I) + SA*SX(I) 00095 SY(I+1) = SY(I+1) + SA*SX(I+1) 00096 SY(I+2) = SY(I+2) + SA*SX(I+2) 00097 SY(I+3) = SY(I+3) + SA*SX(I+3) 00098 END DO 00099 ELSE 00100 * 00101 * code for unequal increments or equal increments 00102 * not equal to 1 00103 * 00104 IX = 1 00105 IY = 1 00106 IF (INCX.LT.0) IX = (-N+1)*INCX + 1 00107 IF (INCY.LT.0) IY = (-N+1)*INCY + 1 00108 DO I = 1,N 00109 SY(IY) = SY(IY) + SA*SX(IX) 00110 IX = IX + INCX 00111 IY = IY + INCY 00112 END DO 00113 END IF 00114 RETURN 00115 END