How to solve the same numerical Problem in 7 different Programming Languages

10

I tried to improve his code
Compiler: ifort
Flags: -O3

  1. I didn’t understand why he needed two subroutines
  2. He also adds some overhead with the subroutine call inside a loop
  3. I added some comments and spaces to make the code readable
  4. I also graph the data at the end
    If possible, how can I improve his code further ?
program simple_num_prob
  implicit none

  integer :: i
  integer,parameter :: tf=25,n=10000
  real,allocatable :: t(:),u(:)
  real :: dt
  real(kind=8) :: t1,t2
  character(len=*),parameter :: plt_file='simple_num_prob.gp'

  call cpu_time(t1)
  allocate(t(n))
  allocate(u(n))

  ! Assigning step value
  dt=real(tf)/real(n)


  ! Initial u value assigned
  u(1)=1.0E-5


  ! Population of t vector
  do i=1,n
     t(i)=real(i)
  end do

  ! Calculating and populating the function vector
  do i=1,n-1
     u(i+1) = u(i) + (dt*(u(i)*(1.0-u(i))))
  end do

  call cpu_time(t2)

  print *, "Elapsed time",t2-t1

  !writing to file
  open (unit=1,file='simple_num_prob.dat')
  do i=1,n
     write(1,*) t(i),' ',u(i)
  end do
  close(1)
  print *, "File written !"

  call cpu_time(t2)
  print *, "Elapsed time with writing to file",t2-t1

  !deallocation
  deallocate(t)
  deallocate(u)

  call execute_command_line('gnuplot ' // plt_file)

end program simple_num_prob

Gnuplot file:

plot 'simple_num_prob.dat' using 1:2
 pause -1
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