How to Execute an Nbody Simulation in Fortran Without Prior Experience?

[trelek2]

Hi!

I've never done any programming in fortran and got stuck trying to test run a program.
Note that I am not learning how to program in fortran, this is for an astrophysics course.

Basically what I need is an instruction how to run a fortran code if I have some .f files and .o files as well as an input file.

The detailed description of what I'm trying to do:

I'm trying to run the code Nbody1 from this http://www.ast.cam.ac.uk/~sverre/web/pages/nbody.htm"
The first problem is making the file. After I download and uncompressed nbody1.tar.Z I can't really make the file since I'm a Mac user and I don't have the f77 compiler (I have g77). So I edited Makefile in dir /nbody1/Real8 by changing line fortran compiler = f77 to FC = g77.
When I make file I then get an error:

O3 nbody1.o block.o bodies.o cmcorr.o check.o cputim.o data.o define.o energy.o escape.o fpoly1.o fpoly2.o frame.o input.o intgrt.o modify.o mydump.o nbint.o output.o ran2.o remove.o scale.o start.o stepi.o steps.o subsys.o verify.o xvpred.o zero.o -o nbody1
make: O3: No such file or directory
make: [nbody1] Error 1 (ignored)

Which might not be relevant since all object files seem to be created. I then try to run nbody1 using "intest" input file. I get really stuck here. In the instructions from the lecturer it says that the command to run is: 3. Run the code (“../Real8/nbody1 < intest”) I have no idea how this should work. If I type the above in I always get bash: no such file or directory. If I indeed have to type that in, which directory should I be in when typing that in?

I tried going to Real8 and typing ./nbody1.o or ./nbody1.f but I always get :

MacBook-Pro-Jan-Zaucha:Real8 janzaucha$ ./nbody1.f < intest
./nbody1.f: line 1: Makefile: command not found
./nbody1.f: line 2: Makefile: command not found
./nbody1.f: line 3: Makefile: command not found
./nbody1.f: line 4: Makefile: command not found
./nbody1.f: line 5: Makefile: command not found
./nbody1.f: line 6: Makefile: command not found
./nbody1.f: line 7: Makefile: command not found
./nbody1.f: line 8: Makefile: command not found
./nbody1.f: line 9: Makefile: command not found
./nbody1.f: line 10: Makefile: command not found
./nbody1.f: line 11: Makefile: command not found
./nbody1.f: line 12: PROGRAM: command not found
./nbody1.f: line 13: Makefile: command not found
./nbody1.f: line 14: INCLUDE: command not found
./nbody1.f: line 15: Makefile: command not found
./nbody1.f: line 16: Makefile: command not found
./nbody1.f: line 17: Makefile: command not found
./nbody1.f: line 18: syntax error near unexpected token `('
./nbody1.f: line 18: ` CALL CPUTIM(CPU0) '

or:

MacBook-Pro-Jan-Zaucha:Real8 janzaucha$ ./nbody1.o < intest
Illegal instruction: 4

Fortran users please help me, I don't have time to learn fortran now, as I'm supposed to perform some Nbody simulations and write a report. If I don't figure out how to make this work quick, I'll run out of time!

Great thanks in advance!

 

[trelek2]

Actually I figured it out, I had to change one more thing in the Makefile. Now everything runs fine!