matlab - Function returns different answers with same arguments -

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i'm transitioning matlab fortran , encountering sorts of weird behaviors i'd never expect matlab. here's 1 that's got me puzzled:

program pruebanormal  double precision :: g01eaf, x, y  character :: t*1  integer :: iffail  iffail = 0  t = 'l'  x = 0.0  y = g01eaf('l',0.0,iffail)  write(*,*) 'y = ',y  end program pruebanormal

i have simple program in i'm trying find pdf @ x=0 of standard n(0,1) variable (should 0.5). g01eaf() nag library function me. i'm using gfortran compile.

leaving rest of program unchanged, depending on how write arguments in g01eaf(), different answers:

a) g01eaf(t,x,iffail)  b) g01eaf(t,0.0,iffail)  c) g01eaf(t,x,0)

now, under matlab, same (correct) answer either way: y = 0.500000. under fortran, however, get:

a) y = 0.500000  b) y = 1.000000  c) program received signal sigsegv: segmentation fault - invalid memory reference.  backtrace error: #0  0xb766c163 #1  0xb766c800 #2  0xb77763ff #3  0x804982e in g01eafn_ violación de segmento (`core' generado)

i have no words answer in (b) , no clue (c) means.

the quick answer "wrong result" in

y = g01eaf('l',0.0,iffail)

you passing different type of real variable in

double precision x x = 0.0   ! x still double precision. y = g01eaf('l',x,iffail)

the function g01eaf expects double precision: should read nag's documentation.

y = g01eaf('l', 0d0, iffail)

now elaborate.

you don't want these problems come often. want ensure interface available function call g01eaf. compiler complain passing real of default kind function.

assuming have up-to-date version of library, want like

use nag_library, : g01eaf, nag_wp implicit none  integer iffail real(kind=nag_wp) y y = g01eaf('l', 0._nag_wp, iffail)  end

again, see documentation. both library, , meaning of modules, etc.

for older versions, 1 should still have module available, may called different, , nag_wp may not defined (meaning must choose kinds).

the module lead complaint iffail requires able set, must variable, not 0. explains (c).


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