LAPACK  3.10.0
LAPACK: Linear Algebra PACKage

◆ sswap()

subroutine sswap ( integer  N,
real, dimension(*)  SX,
integer  INCX,
real, dimension(*)  SY,
integer  INCY 
)

SSWAP

Purpose:
    SSWAP interchanges two vectors.
    uses unrolled loops for increments equal to 1.
Parameters
[in]N
          N is INTEGER
         number of elements in input vector(s)
[in,out]SX
          SX is REAL array, dimension ( 1 + ( N - 1 )*abs( INCX ) )
[in]INCX
          INCX is INTEGER
         storage spacing between elements of SX
[in,out]SY
          SY is REAL array, dimension ( 1 + ( N - 1 )*abs( INCY ) )
[in]INCY
          INCY is INTEGER
         storage spacing between elements of SY
Author
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Further Details:
     jack dongarra, linpack, 3/11/78.
     modified 12/3/93, array(1) declarations changed to array(*)

Definition at line 81 of file sswap.f.

82 *
83 * -- Reference BLAS level1 routine --
84 * -- Reference BLAS is a software package provided by Univ. of Tennessee, --
85 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
86 *
87 * .. Scalar Arguments ..
88  INTEGER INCX,INCY,N
89 * ..
90 * .. Array Arguments ..
91  REAL SX(*),SY(*)
92 * ..
93 *
94 * =====================================================================
95 *
96 * .. Local Scalars ..
97  REAL STEMP
98  INTEGER I,IX,IY,M,MP1
99 * ..
100 * .. Intrinsic Functions ..
101  INTRINSIC mod
102 * ..
103  IF (n.LE.0) RETURN
104  IF (incx.EQ.1 .AND. incy.EQ.1) THEN
105 *
106 * code for both increments equal to 1
107 *
108 *
109 * clean-up loop
110 *
111  m = mod(n,3)
112  IF (m.NE.0) THEN
113  DO i = 1,m
114  stemp = sx(i)
115  sx(i) = sy(i)
116  sy(i) = stemp
117  END DO
118  IF (n.LT.3) RETURN
119  END IF
120  mp1 = m + 1
121  DO i = mp1,n,3
122  stemp = sx(i)
123  sx(i) = sy(i)
124  sy(i) = stemp
125  stemp = sx(i+1)
126  sx(i+1) = sy(i+1)
127  sy(i+1) = stemp
128  stemp = sx(i+2)
129  sx(i+2) = sy(i+2)
130  sy(i+2) = stemp
131  END DO
132  ELSE
133 *
134 * code for unequal increments or equal increments not equal
135 * to 1
136 *
137  ix = 1
138  iy = 1
139  IF (incx.LT.0) ix = (-n+1)*incx + 1
140  IF (incy.LT.0) iy = (-n+1)*incy + 1
141  DO i = 1,n
142  stemp = sx(ix)
143  sx(ix) = sy(iy)
144  sy(iy) = stemp
145  ix = ix + incx
146  iy = iy + incy
147  END DO
148  END IF
149  RETURN
150 *
151 * End of SSWAP
152 *