Error running Demo code

1

I installed Fenics on Windows Subsystem for Linux (Ubuntu 18.04), using

sudo apt-get install software-properties-common
sudo add-apt-repository ppa:fenics-packages/fenics
sudo apt-get update
sudo apt-get install --no-install-recommends fenics

I tried to run demo code ft01_poisson.py

from fenics import *
import matplotlib.pyplot as plt
mesh = UnitSquareMesh(8, 8)
V = FunctionSpace(mesh, 'P', 1)
u_D = Expression('1 + x[0]*x[0] + 2*x[1]*x[1]', degree=2)

but first I got an error importing matplotlib, which I solved by installing it through

sudo apt-get install python3-matplotlib

(I’m running the demo code in Python3).
Then I got and error with FunctionSpace, which was solved adding

from dolfin import *

in the preamble (I don’t know if it was the right way to solve it).
After that I got the following error at Expression line

>>> u_D = Expression('1 + x[0]*x[0] + 2*x[1]*x[1]', degree=2)
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/dolfin/jit/jit.py", line 167, in compile_class
    mpi_comm=mpi_comm)
  File "/usr/lib/python3/dist-packages/dolfin/jit/jit.py", line 47, in mpi_jit
    return local_jit(*args, **kwargs)
  File "/usr/lib/python3/dist-packages/dolfin/jit/jit.py", line 103, in dijitso_jit
    return dijitso.jit(*args, **kwargs)
  File "/usr/lib/python3/dist-packages/dijitso/jit.py", line 178, in jit
    params)
  File "/usr/lib/python3/dist-packages/dijitso/build.py", line 153, in build_shared_library
    status, output = get_status_output(cmd)
  File "/usr/lib/python3/dist-packages/dijitso/system.py", line 41, in _get_status_output_subprocess
    stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
  File "/usr/lib/python3.6/subprocess.py", line 709, in __init__
    restore_signals, start_new_session)
  File "/usr/lib/python3.6/subprocess.py", line 1344, in _execute_child
    raise child_exception_type(errno_num, err_msg, err_filename)
FileNotFoundError: [Errno 2] No such file or directory: 'c++': 'c++'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python3/dist-packages/dolfin/function/expression.py", line 376, in __init__
    self._cpp_object = jit.compile_expression(cpp_code, params)
  File "/usr/lib/python3/dist-packages/dolfin/function/jit.py", line 158, in compile_expression
    expression = compile_class(cpp_data, mpi_comm=mpi_comm)
  File "/usr/lib/python3/dist-packages/dolfin/jit/jit.py", line 170, in compile_class
    raise RuntimeError("Unable to compile C++ code with dijitso")
RuntimeError: Unable to compile C++ code with dijitso

Thanks in advance for any clue.

2

It looks like you do not have a C++ compiler installed on your system. Try running sudo apt install build-essential to install it.

1 Like
3

Thank you.
I faced the same error, and it is solved via your answer.

4

To get rid of this error you can try using os.listdir() function to check that at least python sees the file exists or not.