Hi, I am writing a function that takes in a real data array and a key partition value, which will rearrange the array so that elements with a lower value than x are placed before the elements with values >= the partition value. It then returns the index of the last element of the array with a value less than the partition value.
We were given some pseudo-code which uses the idea that we start from the left and right and simultaneously switch elements using two loops excited together.
CODE
integer function partition_data( xdata, xmiddle )
implicit none
real, dimension(:) :: xdata
real :: xmiddle !INTENT?
integer :: l = 1
integer :: r = 16
real :: temp
do
if (xdata(l) < xmiddle) then
if (l == r) then
partition_data = l
exit
end if
l = l + 1
else
do
if (xdata(r) >= xmiddle) then
if (l == r) then
partition_data = l - 1
exit
end if
r = r - 1
else
temp = xdata(l)
xdata(l) = xdata(r)
xdata(r) = temp
exit
end if
end do
end if
end do
end function partition_data
With the xdata array
xdata = (/ 0.00392, 0.0251, 0.453, 0.667, 0.963, 0.838, 0.335, 0.975, &
0.796, 0.833, 0.345, 0.871, 0.0899, 0.888, 0.701, 0.735 /)
The xmiddle was set to 0.5 in the main test program.
When I compile, I seem to get an infinite loop and I cannot find where it is.
If anyone can spot where I went wrong, that would be great.
Thanks in advance!
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