Re: Simple Program, Lots of Issues (F90)

On Jul 25, 7:57 am, e p chandler <e...@[EMAIL PROTECTED]
> wrote:

> seeftp://ftp.swcp.com/pub/walt/F/Examples/sieve.f95


I tried this simple program using six Fortran compilers but setting
the integer parameter last_number to 10000000 (10 million). All
compiled but four of the six had problems during exection.


  Sun f90:
    signal SEGV (no mapping at the fault address) in MAIN at line 24
in file "primes2.f90"
       24     nums=(/0,(ic,ic=2,mxn)/)


  gfortran:
    Segmentation fault
    Program received signal SIGSEGV, Segmentation fault.
    0x08048875 in MAIN__ () at primes2.f90:29
    29            nums(2*i:mxn:i)=0


  PGI pgf95:
    Segmentation fault
    Program received signal SIGSEGV, Segmentation fault.
    0x08049939 in sieve_of_eratosthenes () at primes2.f90:24
    24        nums=(/0,(ic,ic=2,mxn)/)


  Intel ifort:
    Segmentation fault
    Program received signal SIGSEGV, Segmentation fault.
    0x0000000000402909 in sieve_of_eratosthenes () at primes2.f90:1
    1       program Sieve_Of_Eratosthenes


  Lahey lf95:
    (worked correctly)


  IBM xlf90:
    (worked correctly)


After re-writing the code to introduce DO-loops everywhere, all six
compilers worked correctly and got the same printed output.

My conclusion: DO-loops still work better than array syntax.

Andy



For those who might care, here is my cleaned up version of the
program:

program Sieve_Of_Eratosthenes
implicit none

  integer, parameter :: mxn=10000000

  integer, dimension(mxn) :: nums
  integer :: i,ic,npr

! ..Initialize NUMBERS to 0,2,3,...,MXN (1 is a special case)
  nums(1)=0
  do ic=2,mxn
    nums(ic)=ic
  enddo

! ..The sieve of Eratosthenes: if this number is prime, eliminate all
multiples
  do i=2,mxn
    if (nums(i) /= 0) then
      do ic=2*i,mxn,i
        nums(ic)=0
      enddo
    endif
  enddo

! ..Gather them into the front of the array
  npr=0
  do i=1,mxn
    if (nums(i) /= 0) then
      npr=npr+1
      nums(npr)=nums(i)
    endif
  enddo

! ..Print them out
  print'(a,i0,a,i0)',' There are ', npr,' prime numbers less than ',
mxn
  print'(5i10)',nums(1:npr)

print*,'Normal termination'
end program Sieve_Of_Eratosthenes