daxpy example
时间: 2023-12-12 21:04:20 浏览: 33
Here is an example of the DAXPY function in Fortran:
```
program daxpy_example
implicit none
integer, parameter :: N = 5
real :: a = 2.0
real :: x(N) = [1.0, 2.0, 3.0, 4.0, 5.0]
real :: y(N) = [6.0, 7.0, 8.0, 9.0, 10.0]
print *, "Before DAXPY:"
print *, "x = ", x
print *, "y = ", y
call daxpy(N, a, x, 1, y, 1)
print *, "After DAXPY:"
print *, "x = ", x
print *, "y = ", y
contains
subroutine daxpy(n, a, x, incx, y, incy)
integer, intent(in) :: n, incx, incy
real, intent(in) :: a
real, intent(in) :: x(n)
real, inout :: y(n)
integer :: i
do i = 1, n, incx
y(i) = a * x(i) + y(i)
end do
end subroutine daxpy
end program daxpy_example
```
This program uses the DAXPY function to perform the operation y = a*x + y, where a is a scalar, x and y are vectors of length N, and the operation is performed elementwise.
In this example, we set N to 5, a to 2.0, x to [1.0, 2.0, 3.0, 4.0, 5.0], and y to [6.0, 7.0, 8.0, 9.0, 10.0]. Before calling DAXPY, we print the values of x and y. After calling DAXPY, we print the updated values of y.
The DAXPY subroutine takes in the inputs n, a, x, incx, y, and incy. In this example, incx and incy are both set to 1, which means that we are operating on every element of x and y.
The subroutine then loops over the elements of x and y, performing the DAXPY operation on each element of y. The updated value of y is stored back into the y array.
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