Visual Compaq and Intel Linux fortran comparision

Visual Compaq and Intel Linux fortran comparision

I have translated my programme with Visual Compaq Fortran 6.6 for Windows and with Intel Linux Fortran options -Vaxlib -O0 -tpp6. My application is in DEM (Discrete Element Method ). On a different operation systems i become different results. Why happens so.

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Actually u are not the only one. I have written a DEM program and compiled it with the following compilers:

Digital Fortran Version 6
GFortran for Windows
Gfortran for Linux
G95 for windows
G95 for linux
Salford Compiler (Personal Version, Windows)
Intel Fortran Compiler (Linux)

Believe it or not, for the same source files and input files, I get different answers for each of the compilers. However, I noticed that the difference between these results decrease if the time interval is decreased. Also the difference between the results is very less for the initial calculations, but as the program proceeds, the difference blows up. I beleive that this is due to the small numerical errors that are inherent in any calculation, but is getting added up as the calculation proceeds. Ultimately, the net error in position of each particle becomes more than the diameter of the particle, indicating a completely different position of the particle.

I have asked other people using other DEM codes, but u are only one, as yet, to acknowledge this problem with your code.

Feel free to reply,
Abhishek Basak

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