Good evening to the community,
I've experienced a strange behavior of FDS and, even if I tried to look around on the internet, I haven't found anything to solve this issue, so I can't understand why what I'm going to tell you happens. 
I'm trying to calculate a very simple model (two columns and a beam leaning on them) with extremely regular geometry and mesh size adequately chosen (FDS input file reported below). If I try to launch this simulation with the CMDfds, no issue seems to appear but, when I try to launch it with Pyrosim, I'm receiving back the following error:
forrtl: severe (157): Program Exception - access violation
Image              PC                Routine            Line        Source             
impi.dll           00007FFC4EE28604  Unknown               Unknown  Unknown
impi.dll           00007FFC4EC89FB7  Unknown               Unknown  Unknown
impi.dll           00007FFC4ECCE0B5  Unknown               Unknown  Unknown
impi.dll           00007FFC4ECCC1A6  Unknown               Unknown  Unknown
impi.dll           00007FFC4ECCBE40  Unknown               Unknown  Unknown
impi.dll           00007FFC4F0EE511  Unknown               Unknown  Unknown
fds.exe            00007FF7C4D8770C  MAIN__                     78  main.f90
fds.exe            00007FF7C4D48D92  Unknown               Unknown  Unknown
fds.exe            00007FF7C55D6F09  Unknown               Unknown  Unknown
KERNEL32.DLL       00007FFC9B388364  Unknown               Unknown  Unknown
ntdll.dll          00007FFC9D8870D1  Unknown               Unknown  Unknown
I know that in the reported FDS input file reactions or burners are missing but, even if adding it onto Pyrosim, I'm having back always the aforementioned error.
Does anyone could tell me the reason of this error? Thank you in advance for the helping hand.
Best regards.
Nicola Tunzi