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LAPACK
3.4.1
LAPACK: Linear Algebra PACKage
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00001 *> \brief \b SSWAP 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 SSWAP(N,SX,INCX,SY,INCY) 00012 * 00013 * .. Scalar Arguments .. 00014 * INTEGER INCX,INCY,N 00015 * .. 00016 * .. Array Arguments .. 00017 * REAL SX(*),SY(*) 00018 * .. 00019 * 00020 * 00021 *> \par Purpose: 00022 * ============= 00023 *> 00024 *> \verbatim 00025 *> 00026 *> interchanges two vectors. 00027 *> uses unrolled loops for increments equal to 1. 00028 *> \endverbatim 00029 * 00030 * Authors: 00031 * ======== 00032 * 00033 *> \author Univ. of Tennessee 00034 *> \author Univ. of California Berkeley 00035 *> \author Univ. of Colorado Denver 00036 *> \author NAG Ltd. 00037 * 00038 *> \date November 2011 00039 * 00040 *> \ingroup single_blas_level1 00041 * 00042 *> \par Further Details: 00043 * ===================== 00044 *> 00045 *> \verbatim 00046 *> 00047 *> jack dongarra, linpack, 3/11/78. 00048 *> modified 12/3/93, array(1) declarations changed to array(*) 00049 *> \endverbatim 00050 *> 00051 * ===================================================================== 00052 SUBROUTINE SSWAP(N,SX,INCX,SY,INCY) 00053 * 00054 * -- Reference BLAS level1 routine (version 3.4.0) -- 00055 * -- Reference BLAS is a software package provided by Univ. of Tennessee, -- 00056 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- 00057 * November 2011 00058 * 00059 * .. Scalar Arguments .. 00060 INTEGER INCX,INCY,N 00061 * .. 00062 * .. Array Arguments .. 00063 REAL SX(*),SY(*) 00064 * .. 00065 * 00066 * ===================================================================== 00067 * 00068 * .. Local Scalars .. 00069 REAL STEMP 00070 INTEGER I,IX,IY,M,MP1 00071 * .. 00072 * .. Intrinsic Functions .. 00073 INTRINSIC MOD 00074 * .. 00075 IF (N.LE.0) RETURN 00076 IF (INCX.EQ.1 .AND. INCY.EQ.1) THEN 00077 * 00078 * code for both increments equal to 1 00079 * 00080 * 00081 * clean-up loop 00082 * 00083 M = MOD(N,3) 00084 IF (M.NE.0) THEN 00085 DO I = 1,M 00086 STEMP = SX(I) 00087 SX(I) = SY(I) 00088 SY(I) = STEMP 00089 END DO 00090 IF (N.LT.3) RETURN 00091 END IF 00092 MP1 = M + 1 00093 DO I = MP1,N,3 00094 STEMP = SX(I) 00095 SX(I) = SY(I) 00096 SY(I) = STEMP 00097 STEMP = SX(I+1) 00098 SX(I+1) = SY(I+1) 00099 SY(I+1) = STEMP 00100 STEMP = SX(I+2) 00101 SX(I+2) = SY(I+2) 00102 SY(I+2) = STEMP 00103 END DO 00104 ELSE 00105 * 00106 * code for unequal increments or equal increments not equal 00107 * to 1 00108 * 00109 IX = 1 00110 IY = 1 00111 IF (INCX.LT.0) IX = (-N+1)*INCX + 1 00112 IF (INCY.LT.0) IY = (-N+1)*INCY + 1 00113 DO I = 1,N 00114 STEMP = SX(IX) 00115 SX(IX) = SY(IY) 00116 SY(IY) = STEMP 00117 IX = IX + INCX 00118 IY = IY + INCY 00119 END DO 00120 END IF 00121 RETURN 00122 END