Tips for Debugging

  1. Look at the full output. The final error raised by yggdrasil may not contain all of the informations provided by errors that were raised within a model due to limitations of error forwarding between the different languages. It is important to look at the full output from a failed run. Usually the first error encountered or the error raised within the model’s language will be the most relevant and be the most useful for debugging.

  2. Check for known errors. The list below includes several errors that have already been encountered by yggdrasil users and the method used to solve the issue.

  3. Turn on debugging log messages. This will increase the number of log messages greatly and help you track down any issues. Debug messages can be enabled by setting the ygg and client debug options in your config file to DEBUG (see Configuration Options for details on the location of the user config file and additional logging options).

  4. Trace the flow of data. Use the debug messages to trace the flow of data from one model to the next and determine where the failure is occuring.

  5. Check |yggdrasil| summary. yggdrasil includes a command line utility, ygginfo that will print out relevent information about yggdrasil, the languages it supports, and the operating system. This information can be useful for running down conflicting dependencies or determining why yggdrasil thinks a language is or isn’t install. Additional information about the system can be display by adding the --verbose flag, including the current conda environment information (if you are using a conda environment) and informaiton about the current R installation (if R is installed). This information should be included in any Github issues opened related to bugs in order to help us assist you.

Possible Errors

General Errors

  • You get errors that look like zmq.error.ZMQError: Too many open files when running integrations.

    Possible Cause: The limit on the number of file identifiers that can be open is too low (the default on Mac is 256) and yggdrasil is trying to use more than this limit (file identifiers are opened for multiprocessing objects, ZeroMQ sockets, files, etc.). Solution: Check what the limit is via ulimit -n. If it is of order 100 (as on Mac by default), this is likely the cause and you can fix it by increasing the limit via ulimit -n 1024.

  • You get an error that starts with the line:

    OMP: Error #15: Initializing libomp.dylib, but found libiomp5.dylib already initialized.

    Possible Cause: You have multiple version of OpenMP installed and the model is trying to load more than one. This is most likely to occur if 1) you use conda to install yggdrasil and its dependencies as many conda dependencies use the Intel Math Kernel library for optimization which are threaded via OpenMP (See discussion here) and 2) your model includes threading or has an dependency/interpreter that is using a different version of OpenMP (e.g. Matlab also installs its own version of libiomp5).


    1. [RECOMMENDED] Set the KMP_DUPLICATE_LIB_OK environment variable to disable this error (e.g. via export KMP_DUPLICATE_LIB_OK=1). This works in most cases, but may cause unexpected behavior as described in the error message. You can also have yggdrasil set the environment variable any time it runs a model by running yggconfig --allow-multiple-omp so that you don’t need to set in each time you open a new terminal/command prompt (or in your startup script, e.g. .bashrc).

    2. [MATLAB ONLY] Try hidding the Matlab version of libiomp by running yggconfig --hide-matlab-libiomp, which will slightly modify the name of the libiomp installed by Matlab so that Matlab uses the conda version of OpenMP during runtime. This solution is not recommended if you use Matlab outside of conda environments and can be reversed via yggconfig --restore-matlab-libiomp.

    3. Re-install yggdrasil in a clean conda environment after installing the nomkl conda package to ensure that versions of yggdrasil’s dependencies are installed that don’t use Intel’s Math Kernel Library. If this does not work, it is likely that other dependencies require the OpenMP library.

    4. Uninstall all but one of the conflicting versions of OpenMP. This can be tricky to do and should be approached with caution as removing libraries without understanding how/why they were installed can cause unintended consequences if it is required by another application.

Linux Errors

  • Importing yggdrasil installed using conda causes ImportError: /usr/lib/x86_64-linux-gnu/ version 'GLIBCXX_3.4.22' not found (required by <some python package>)

    Possible Cause: For some reason (e.g. path modification), the Python package raising the import error is trying to use the system version of libstdc++ rather than the conda version that the package was compiled against. Solutions:

    1. Add the conda library path so that libraries installed by conda are found before the system libraries: export LD_LIBRARY_PATH=$CONDA_PREFIX/lib:$LD_LIBRARY_PATH.

    2. Preload the conda libstdc++ after verifying the path to your conda install’s libstdc++ shared object library: export LD_PRELOAD=$CONDA_PREFIX/lib/

MacOS Errors

  • You get Undefined symbol errors following a warning similar to:

    ld: warning: ignoring file /Library/Developer/CommandLineTools/SDKs/MacOSX10.14.sdk/usr/lib/libSystem.tbd, file was built for unsupported file format ( 0x2D 0x2D 0x2D 0x20 0x21 0x74 0x61 0x70 0x69 0x2D 0x74 0x62 0x64 0x2D 0x76 0x33 ) which is not the architecture being linked (x86_64): /Library/Developer/CommandLineTools/SDKs/MacOSX10.14.sdk/usr/lib/libSystem.tbd

    or you get an error about a missing locale.h header like:

    /Users/langmm/miniconda3/envs/pyrj/bin/../include/c++/v1/locale.h:46:15: fatal error: 'locale.h' file not found
    #include_next <locale.h>

    Possible Cause: You are trying to use the conda-forge supplied compilers on a newer Mac OS (see discussion here). The newer Mac SDKs cannot be packaged by conda-forge due to licensing issues. As a result, the libraries are not correctly linked and you will get the above warning and Undefined symbol or missing header errors.

    Solution: Download an older SDK (10.9 works well for pre-Apple silicon Macs, but 11.0 should be used for Macs with the M1/M2 chips and arm64 architechture) and point the conda compilers to it using the steps below. If you use a version other than 11.0, check the location of that release’s download directly at to verify what the directory containing it is as it will be version dependent (step 3).:

    $ export CONDA_BUILD_SYSROOT="$(xcode-select -p)/SDKs/MacOSX${MACOSX_DEPLOYMENT_TARGET}.sdk"
    $ curl -L -O${MACOSX_DEPLOYMENT_TARGET}.sdk.tar.xz
    $ tar -xf MacOSX${MACOSX_DEPLOYMENT_TARGET}.sdk.tar.xz -C "$(dirname "$CONDA_BUILD_SYSROOT")"  # This may require sudo

    You will need to set the CONDA_BUILD_SYSROOT environment variable in every process in which you will be running yggdrasil. Alternatively, you can permanently add it to your yggdrasil configuration file using the following command:

    $ yggconfig --macos-sdkroot <path to sdk>
  • When compiling a model using CMake you get ld: library not found for -lintl Possible Causes:

    1. The libintl cannot be found because it is not installed.

  1. The -lintl library is linked via the LDFLAGS environment variable, but the directory containing the library is not added to the list of paths searched for libraries (typically /usr/lib or /usr/local/lib).

Solution: Verify that libintl is installed and install it if it is not (it can be installed via brew reinstall gettext). If you still get the error, report it via an issue on the `yggdrasil Github repository<>`_ as yggdrasil should be able to add the appropriate paths that CMake misses. In the meantime, you can manually add the path via the environment variable (e.g. LDFLAGS="$LDFLAGS -L/path/to/directory/containing/libintl").

Matlab Errors

  • The MATLAB model hangs for a long time during startup and then times out.

    Possible Cause: If MATLAB has trouble accessing the license server, it can hang for a long time during startup. yggdrasil has a config parameter that controls how long it will wait for MATLAB to start. If it takes longer than that amount of time, it will kill the process and report an error.

    Solution: Verify that you have access to the MATLAB license server (e.g. an internet connection and, if appropriate, the correct VPN). If you do (i.e. you can start the MATLAB application independent of yggdrasil), increase the startup_waittime_s config parameter described here.

  • The MATLAB model seems to run, but does not output anything to stdout or to any output comms.

    Possible Cause: Another error is occuring, but you are using the MATLAB engine for Python to run models and the error is not being redirected to the Python output. Solution: Try running your model without the MATLAB engine for Python by setting the disable_engine config parameter in the matlab section of your yggdrasil config file to True by running yggconfig --disable-matlab-engine-for-python or editting the file directly (see here).

C++ Errors

  • The received message size is always 0, but the message is not empty.

    Possible Cause: Some C++ compilers will incorrectly pass the size_t reference such that it is copied and set to zero as it is passed.

    Solution: Use strlen to get the actual size of the received string rather than relying on the size returned by the yggdrasil receive call.

  • You are sending/receiving from/into a character array (e.g. char x[100];), and the received message is always empty even through the received message size may or may not be 0.

    Possible Cause: Some C++ compilers will incorrectly pass the reference to the character array such that is is copied and, therefore, not assigned to during the receive call.

    Solution: Dynamically allocate a variable on heap (e.g. char *x = (char*)malloc(100)) to use when receiving a character array, just be sure to free the variable at the end.

R Errors

  • You get an error message along the lines of:

    ImportError: /usr/lib/x86_64-linux-gnu/ version `GLIBCXX_3.4.20' not found

    Possible Causes: This error usually results from a conflict in the shared libraries available during R calls to Python as handled through the reticulate package. The reticulate development team is aware of this (see this issue and the issues it references), but has not yet taken steps to address it as of writing this (2019/06/20). This error is most likely to occur if you are using a conda environment to manage yggdrasil, but are using a version of R that was not installed via conda.


    1. Install R using conda (e.g. conda install r-base).

    2. Install the missing shared library on your local machine (i.e. outside the conda environment) so that it is available when using R.

  • You get a segfault when calling one of the Python object methods.

    Possible Cause: The Python and R packages are using different C/C++ libraries. This error can result from using conda to manage the Python packages, but using a version of R and R packages that were installed outside the conda environment using locally installed versions of the libraries.

    Solution: Use conda to install R and the R dependencies.

  • When running an R model, you get an R error message that looks like:

    Error in .simplify_units(NextMethod(), .symbolic_units(numerator, denominator)) :
      could not find function "isFALSE"
    Calls: %<-% ... multi_assign -> modelB_function2 -> Ops.units -> .simplify_units
    Execution halted

    Possible Causes: You are using version 0.6-6 of the R units package, but an older version of R (<3.5). This error is more likely if you installed R on Ubuntu Linux using apt as the default version is 3.2.3 (as of 2020/4/14).


    1. [RECOMMENDED] Install a newer version of R. See Additional Steps for R Models for details on installing a more recent version of R on Linux.

    2. Install a new version of units (if one is available).

    3. Intall units version 0.6-5 (be sure to uninstall the existing version of units first).