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FTN95 does not process ASSOCIATE construct correctly

 
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mecej4



Joined: 31 Oct 2006
Posts: 1886
PostPosted: Sun Jan 07, 2024 6:49 pm    Post subject: FTN95 does not process ASSOCIATE construct correctly Reply with quote
Paul, I do not have much experience using ASSOCIATE, and my expectations regarding what the following test program should do may be unjustified.

Code:
program cubesift

  implicit none
  integer, parameter :: IMAX = 4
  integer            :: year, i, bits
  integer, parameter :: cubes(IMAX) = [ (i*i*i, i = 1, IMAX) ]

  bits = 1
  associate (bmask => btest(bits,[(i-1, i = 1, IMAX)]))
     year = sum(cubes, mask = bmask)
     print '(i5, 4x,4L2)',year,bmask
  end associate

end program


FTN95 gives the output

Code:
  100     T


whereas other compilers give

Code:
    1     T F F F


The array "cubes" contains [1^3, 2^3, 3^3, 4^3]. The mask array "bmask" has only the first element set to .T., so "sum" should be applied to just [1^3], yielding 1.

The FTN95-compiled code appears to make "bmask" a scalar 'T', which then gets replicated three times in the expression sum(cubes, mask = bmask). As a result, "year" is evaluated as sum([1^3, 2^3, 3^3, 4^3]), i.e., 100.
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PaulLaidler
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Joined: 21 Feb 2005
Posts: 7927
Location: Salford, UK
PostPosted: Mon Jan 08, 2024 10:06 am    Post subject: Reply with quote
mecej4

Thank you for the bug report. I have logged this for investigation.
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PaulLaidler
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Joined: 21 Feb 2005
Posts: 7927
Location: Salford, UK
PostPosted: Thu Feb 01, 2024 12:22 pm    Post subject: Reply with quote
This failure has now been fixed for the next release of FTN95.
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mecej4



Joined: 31 Oct 2006
Posts: 1886
PostPosted: Thu Feb 01, 2024 1:57 pm    Post subject: Reply with quote
Thanks.

Here is the program from which the bug reproducer of this thread was created, if you wish to verify that the fix works on it, too.

Code:

! Given a range of years between 1 and 13^3-1, list years that may be
! expressed as the sum of cubes of integers with no repetitions allowed/
! Pipe the output of the program through the system SORT utility
program cubem

  implicit none
  integer, parameter :: YLOW = 2020, YHIGH = 2030
  integer, parameter :: IMAX = 12          ! smallest possible I s.t. (I+1)^3 > YHIGH
  integer            :: year, i, nk, bits
  integer, parameter :: cubes(IMAX) = [ (i*i*i, i = 1, IMAX) ]

  nk = 0
  do bits = 1, ishft (1, IMAX)-1
     associate (bmask => btest(bits,[(i-1, i = 1, IMAX)]))
        year = sum(cubes, mask = bmask)
        if (year < YLOW .or. year > YHIGH) cycle
        nk = nk+1
        print '(i6,4x,10i3)',year,pack([(i, i = 1, IMAX)], mask=bmask)
     end associate
  end do
  print '(/,A,i4,A)','Found ',nk,' years that are sums of cubes'

end program


The expected output:

Code:
  2024      2  3  4  5  6  7  8  9
  2025      1  2  3  4  5  6  7  8  9
  2023      2  5  6  7 11
  2024      1  2  5  6  7 11

Found    4 years that are sums of cubes
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PaulLaidler
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Joined: 21 Feb 2005
Posts: 7927
Location: Salford, UK
PostPosted: Thu Feb 01, 2024 2:37 pm    Post subject: Reply with quote
mecej4

Thanks. That also works.
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