Swap Two Vectors

Calling Sequence

CALL DSWAP	(N, DX, INCX, DY, INCY)
CALL SSWAP	(N, SX, INCX, SY, INCY)
CALL ZSWAP	(N, ZX, INCX, ZY, INCY)
CALL CSWAP	(N, CX, INCX, CY, INCY)
void dswap	(int n, double *dx, int incx, double *dy, int incy)
void sswap	(int n, float *sx, int incx, float *sy, int incy)
void zswap	(int n, doublecomplex *zx, int incx, doublecomplex *zy, int incy)
void cswap	(int n, complex *cx, int incx, complex *cy, int incy)

Arguments

N	Number of elements in the vector. N 0.
xX	Input vector X; the size of array X must be at least max(1,N*|INCX|).
INCX	Specifies the storage spacing between successive elements of the vector X. A value of one indicates that the elements of the vector are consecutive in memory.
	If X refers to a two-dimensional array and the value of INCX is equal to the leading dimension of X then the elements of the vector will be a row of X.
	If X refers to a two-dimensional array and the value of INCX is equal to the leading dimension of X plus one then the elements of the vector will be a diagonal of X.
xY	Result vector Y; the size of array Y must be at least max(1,N*|INCY|).
INCY	Specifies the storage spacing between successive elements of the vector Y. A value of one indicates that the elements of the vector are consecutive in memory.
	If Y refers to a two-dimensional array and the value of INCY is equal to the leading dimension of Y then the elements of the vector will be a row of Y.
	If Y refers to a two-dimensional array and the value of INCY is equal to the leading dimension of Y plus one then the elements of the vector will be a diagonal of Y.

Sample Program

PROGRAM TEST

IMPLICIT NONE

INTEGER N

PARAMETER (N = 3)

INTEGER I, INCX, INCY, J, LARGE

DOUBLE PRECISION A(N,N)

INTEGER IDAMAX

EXTERNAL DSWAP, IDAMAX

C

C Initialize the array A to store the matrix A shown below.

C

C 1.0 1.5 4.5

C A = 3.0 2.5 9.5

C 2.0 3.5 5.5

C

DATA A / 1.0D0, 3.0D0, 2.0D0, 1.5D0, 2.5D0, 3.5D0,

$ 4.5D0, 9.5D0, 5.5D0 /

C

PRINT 1000

PRINT 1010, ((A(I,J), J = 1, N), I = 1, N)

C

C Find the largest element in column 1.

C

INCX = 1

LARGE = IDAMAX (N, A, INCX)

C

C Swap the first row with the row containing the largest

C element in column 1.

C

INCX = N

INCY = N

CALL DSWAP (N, A(1,1), INCX, A(LARGE,1), INCY)

PRINT 1020

PRINT 1010, ((A(I,J), J = 1, N), I = 1, N)

C

1000 FORMAT (1X, 'A:')

1010 FORMAT (3(3(2X, F3.1) / ))

1020 FORMAT (1X, 'A'':')

C

END

Sample Output

A:
1.0 1.5 4.5
3.0 2.5 9.5
2.0 3.5 5.5
A':
3.0 2.5 9.5
1.0 1.5 4.5
2.0 3.5 5.5