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different results: ftn77->ftn95

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dgurok

Joined: 26 May 2011
Posts: 66

Posted: Wed Jun 01, 2011 10:52 am Post subject: different results: ftn77->ftn95

Hello everybody,

I encountered problems whereever integer was used in instrinsic functions of typ real. this strange behavior is different compared to ftn77.

Isn�t the data type of an expression defined by the hightest order from left to right any more?

Results with ftn77

Code:

14.14214 integer 2 exponent in subroutine
14.14214 IV4 as exponent
14.14214 IV2 as exponent
14.14214 2 as exponent - not using /INTS compile option
14.14214 2.0 as exponent
14.14214 2 as exponent for negative argument - not using /INTS

Results with ftn95

Code:

10.00000 integer 2 exponent in subroutine
14.14214 IV4 as exponent
10.04988 IV2 as exponent
14.14214 2 as exponent - not using /INTS compile option
14.14214 2.0 as exponent
14.14214 2 as exponent for negative argument - not using /INTS

Source Code:

Code:

C
C Salford FTN95 evaluation
C Compile Option: set ftn95opt=/C/DEBUG/ALL_WARNINGS/UNLIMITED_ERRORS/FIXED_FORMAT/WINDOWS
C
integer*2 IV2
integer*4 IV4
real*4 x2,x4,y2,y4,W42
real*4 SQRT
x4=10.
x2=0.
y4=10.
y2=0.

call sr1(.true.,2s,x2,x4,y2,y4)
iv2=2
iv4=2
C
C Result is 0.0 due to exponent as integer
W42=SQRT((X4-X2)**IV4 +(Y4-Y2)**IV4 )
write(2,1001) w42, ' IV4 as exponent'
C
C Result is 0.0 due to exponent as integer
W42=SQRT((X4-X2)**IV2 +(Y4-Y2)**IV2 )
write(2,1001) w42, ' IV2 as exponent'
C
C Result is wrong due to exponent as integer
W42=SQRT((X4-X2)**2 +(Y4-Y2)**2 )
write(2,1001) w42,
* ' 2 as exponent - not using /INTS compile option'
C
C Proper result due to **2.0
W42=SQRT((X4-X2)**2.0+(Y4-Y2)**2.0)
write(2,1001) w42, ' 2.0 as exponent '
C
C Result invalid due to negativ value of x2-x4
W42=SQRT((X2-X4)**2 +(Y4-Y2)**2 )
write(2,1001) w42,
* ' 2 as exponent for negative argument - not using /INTS'
C
C Result invalid due to negativ value of x2-x4
C W42=SQRT((X2-X4)**2. +(Y4-Y2)**2. )
C write(2,1001) w42

1001 format(F10.5,A)
end

subroutine SR1(LOGIC,i2,x2,x4,y2,y4)
integer*2 I2
logical*4 logic
real*4 x2,x4,y2,y4
W42=SQRT((X4-X2)**i2 +(Y4-Y2)**i2 )
write(2,1001) w42,' integer 2 exponent in subroutine'
if(logic) return
return
1001 format(F10.5,A)
end

JohnCampbell

Joined: 16 Feb 2006
Posts: 2615
Location: Sydney

Posted: Thu Jun 02, 2011 3:21 am Post subject:

I changed the program slightly to free format and compiled and ran with
/ints /lgo or /intl /lgo to get significantly different results.

Code:

!
integer*2 IV2
integer*4 IV4
real*4 x2,x4,y2,y4,W42
! real*4 SQRT
x4=10.
x2=0.
y4=10.
y2=0.

call sr1(.true.,2s,x2,x4,y2,y4)
iv2=2
iv4=2
!
write (2,*) '(X4-X2)**IV2 +(Y4-Y2)**IV2 = ', (X4-X2)**IV2 + (Y4-Y2)**IV2
write (2,*) '(X4-X2)**IV4 +(Y4-Y2)**IV4 = ', (X4-X2)**IV4 + (Y4-Y2)**IV4
!
! Result is 0.0 due to exponent as integer
W42=SQRT((X4-X2)**IV4 +(Y4-Y2)**IV4 )
write(2,1001) w42, ' IV4 as exponent'
!
! Result is 0.0 due to exponent as integer
W42=SQRT((X4-X2)**IV2 +(Y4-Y2)**IV2 )
write(2,1001) w42, ' IV2 as exponent'
!
! Result is wrong due to exponent as integer
W42=SQRT((X4-X2)**2 +(Y4-Y2)**2 )
write(2,1001) w42, ' 2 as exponent - not using /INTS compile option'
!
! Proper result due to **2.0
W42=SQRT((X4-X2)**2.0+(Y4-Y2)**2.0)
write(2,1001) w42, ' 2.0 as exponent '
!
! Result invalid due to negativ value of x2-x4
W42=SQRT((X2-X4)**2 +(Y4-Y2)**2 )
write(2,1001) w42, ' 2 as exponent for negative argument - not using /INTS'
!
! Result invalid due to negativ value of x2-x4
! W42=SQRT((X2-X4)**2. +(Y4-Y2)**2. )
! write(2,1001) w42

1001 format(F10.5,A)
end

subroutine SR1(LOGIC,i2,x2,x4,y2,y4)
integer*2 I2
logical*4 logic
real*4 x2,x4,y2,y4, w42
W42=SQRT((X4-X2)**i2 +(Y4-Y2)**i2 )
write(2,1001) w42,' integer 2 exponent in subroutine'
if(logic) return
return
1001 format(F10.5,A)
end

/ints /lgo produces

Code:

[FTN95/Win32 Ver. 5.50.0 Copyright (c) Silverfrost Ltd 1993-2010]
NO ERRORS [<main program> FTN95/Win32 v5.50.0]
NO ERRORS [<SR1> FTN95/Win32 v5.50.0]
Creating executable: C:\TEMP\lgotemp@.exe
Program entered
10.00000 integer 2 exponent in subroutine
(X4-X2)**IV2 +(Y4-Y2)**IV2 = 200.000
(X4-X2)**IV4 +(Y4-Y2)**IV4 = 200.000
14.14214 IV4 as exponent
10.04988 IV2 as exponent
10.00500 2 as exponent - not using /INTS compile option
14.14214 2.0 as exponent
0.94868 2 as exponent for negative argument - not using /INTS

/intl /lgo produces

Code:

[FTN95/Win32 Ver. 5.50.0 Copyright (c) Silverfrost Ltd 1993-2010]
NO ERRORS [<main program> FTN95/Win32 v5.50.0]
NO ERRORS [<SR1> FTN95/Win32 v5.50.0]
Creating executable: C:\TEMP\lgotemp@.exe
Program entered
10.00000 integer 2 exponent in subroutine
(X4-X2)**IV2 +(Y4-Y2)**IV2 = 200.000
(X4-X2)**IV4 +(Y4-Y2)**IV4 = 200.000
14.14214 IV4 as exponent
1.04881 IV2 as exponent
14.14214 2 as exponent - not using /INTS compile option
14.14214 2.0 as exponent
14.14214 2 as exponent for negative argument - not using /INTS

JohnCampbell

Joined: 16 Feb 2006
Posts: 2615
Location: Sydney

Posted: Thu Jun 02, 2011 6:29 am Post subject:

Definately a problem in FTN95 if the expression inside SQRT uses integer*2 for exponent.

Code:

integer*2 IV2
integer*4 IV4
real*4 x2,x4,y2,y4,W42, x
! real*4 SQRT
intrinsic sqrt
!
x4=10.
x2=0.
y4=10.
y2=0.

call sr1(.true.,2s,x2,x4,y2,y4)
call sr1(.true.,2_2,x2,x4,y2,y4)
call sr1(.true.,2_3,x2,x4,y2,y4)
!
iv2=2
iv4=2
!
write (2,*) '(X4-X2)**IV2 +(Y4-Y2)**IV2 = ', (X4-X2)**IV2 + (Y4-Y2)**IV2
write (2,*) '(X4-X2)**IV4 +(Y4-Y2)**IV4 = ', (X4-X2)**IV4 + (Y4-Y2)**IV4
!
! Result is 0.0 due to exponent as integer
W42=SQRT((X4-X2)**IV4 +(Y4-Y2)**IV4 )
x = ((X4-X2)**IV4 +(Y4-Y2)**IV4 )
write(2,1001) w42, ' IV4 as exponent', x
!
! Result is 0.0 due to exponent as integer
W42=SQRT((X4-X2)**IV2 +(Y4-Y2)**IV2 )
x = ((X4-X2)**IV2 +(Y4-Y2)**IV2 )
write(2,1001) w42, ' IV2 as exponent', x
!
! Result is wrong due to exponent as integer
W42=SQRT((X4-X2)**2 +(Y4-Y2)**2 )
x = ((X4-X2)**2 +(Y4-Y2)**2 )
write(2,1001) w42, ' 2 as exponent - not using /INTS compile option', x
!
! Proper result due to **2.0
W42=SQRT((X4-X2)**2.0+(Y4-Y2)**2.0)
x = ((X4-X2)**2.0+(Y4-Y2)**2.0)
write(2,1001) w42, ' 2.0 as exponent ', x
!
! Result invalid due to negativ value of x2-x4
W42=SQRT((X2-X4)**2 +(Y4-Y2)**2 )
x = ((X2-X4)**2 +(Y4-Y2)**2 )
write(2,1001) w42, ' 2 as exponent for negative argument - not using /INTS', x
!
1001 format(F10.5,A,f10.5)
end

subroutine SR1(LOGIC,i2,x2,x4,y2,y4)
!
integer*2 I2
logical*4 logic
real*4 x2,x4,y2,y4, w42, x, y
intrinsic sqrt
!
W42=SQRT((X4-X2)**i2 + (Y4-Y2)**i2 )
x = ((X4-X2)**i2 + (Y4-Y2)**i2 )
y =SQRT(x)
write(2,1001) w42,' integer 2 exponent in subroutine', x,y
if(logic) return
return
1001 format(F10.5,A,2f10.5)
end

results of runs

Code:

using /intl /lgo
[FTN95/Win32 Ver. 5.50.0 Copyright (c) Silverfrost Ltd 1993-2010]
Creating executable: C:\TEMP\lgotemp@.exe
Program entered
10.00000 integer 2 exponent in subroutine 200.00000 14.14214
...
14.14214 IV4 as exponent 200.00000
10.04988 IV2 as exponent 200.00000
14.14214 2 as exponent - not using /INTS compile option 200.00000
14.14214 2.0 as exponent 200.00000
14.14214 2 as exponent for negative argument - not using /INTS 200.00000

using /ints /lgo
[FTN95/Win32 Ver. 5.50.0 Copyright (c) Silverfrost Ltd 1993-2010]
Creating executable: C:\TEMP\lgotemp@.exe
Program entered
10.00000 integer 2 exponent in subroutine 200.00000 14.14214
...
14.14214 IV4 as exponent 200.00000
10.00500 IV2 as exponent 200.00000
1.04881 2 as exponent - not using /INTS compile option 200.00000
14.14214 2.0 as exponent 200.00000
0.94868 2 as exponent for negative argument - not using /INTS 200.00000

PaulLaidler
Site Admin

Joined: 21 Feb 2005
Posts: 8210
Location: Salford, UK

Posted: Wed Mar 07, 2012 10:32 am Post subject:

This bug has now been fixed for the next release of FTN95.

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