Frequently Asked Questions (FAQ)

This is a list of frequently asked questions about GaspiCxx. Please feel free to suggest new ones!

Question

How can I ssh to localhost without password?

In order to run GaspiCxx programs, you will need to be able to ssh to localhost without password. First, generate an ssh key-pair:

cd ~/.ssh
ssh-keygen

Make sure not to overwrite existing keys. When asked for a passphrase, Enter passphrase (empty for no passphrase):, simply leave empty and return with enter. Also take specific care to set correct user rights on all files in .ssh, cf. for instance here. Next, append the public key to the authorized_keys file:

cat id_rsa.pub >> authorized_keys

Install and start an ssh server, e.g., openssh-server on Fedora. More details can be found for instance here.

Question

I get an execution error GPI library initialization incorrect environment vars when trying to run my script. What shall I do?

Most likely you are running your program with ./my_executable. Please make sure to execute your code with gaspicxx_run -- ./my_executable instead.

Question

I get an execution error GPI library initialization general error. What shall I do?

This error occurs when the underlying GPI-2 library tries to connect to a previously used socket, which is not yet released. Try to re-run your code after a short while so that the port becomes available again.

Question

The execution seems to stall. What shall I do?

Please use the gaspicxx_run --cleanup command to kill any processes that might be still running from a previous (aborted) call to gaspicxx_run as shown here. Note that you can also interrupt a running GaspiCxx instance (distributed on multiple nodes) by using Ctrl+c.

Question

When trying to build GaspiCxx, CMake cannot find pybind11:

Could not find a package configuration file provided by "pybind11" with any

of the following names: [...]

What shall I do?

This error occurs when pybind11 is installed using pip. Please use conda instead, as recommended in the installation guide.

Question

When trying to build GaspiCxx, CMake does not detect the Python interpreter from the active conda environment. What shall I do?

You will need to manually add the path to the conda environment’s bin directory to your PATH. You will also need to specify the path to the python library on the command line when configuring GaspiCxx:

PATH_TO_CONDA_ENV=/path/to/conda/env
export PATH=${PATH_TO_CONDA_ENV}/bin:${PATH}
cmake -DPYTHON_EXECUTABLE=${PATH_TO_CONDA_ENV}/bin/python \
      -DPYTHON_LIBRARY=${PATH_TO_CONDA_ENV}/lib ../

Question

Can I install GaspiCxx on MacOS?

GaspiCxx is only supported on Linux systems, as its GPI-2 dependency is built on top of a Linux kernel API called epoll.