Frequently Asked Questions

Building Enzo

Q: I’m getting a compilation error that looks something like:

Grid_ComputeCoolingTime.C(201): error: expression must have class type
   if (grackle_data.use_grackle == TRUE)

what does this mean?

A: Check what branch you are on using with Enzo ($ hg branch). This issue is likely related to a version conflict between Enzo and Grackle 2.0 and Grackle 3.0. Currently the stable branch only works with Grackle 2.0, and the development branch ($ hg checkout week-of-code) works with Grackle 3.0. We recommend switching to using the development branch and using the most recent version of Grackle 3.0 instead of using Grackle 2.0 if you need Grackle for your simulations.

Q: I’m getting a compilation error related to HDF5. What is HDF5 and how to I get it?

A: HDF5 is a data format with accompanying library for writing very large data sets. Enzo uses HFD5 for data output. If you do not have a version of HDF5 available on your machine, you can download binaries or source code for HDF5 from Once you have a version of HDF5 installed on your machine, you need to notify Enzo where it is located for the build process in the Makefile (eg. Make.mach.linux-gnu or For example, if HDF5 was installed in /home/enzo-user/local/hdf5/, you would edit the line

LOCAL_HDF5_INSTALL = /home/enzo-user/local/hdf5

then run

$ make machine-linux-gnu
$ make clean
$ make

to rebuild enzo.exe with your HDF5 installation. When running enzo.exe, make sure that the HDF5 library is in LD_LIBRARY_PATH. In this example, if you are running bash, run the command

$ export LD_LIBRARY_PATH=/home/enzo-user/local/hdf5/lib/:$LD_LIBRARY_PATH

to put the HDF5 library in the library path before running Enzo.

Running Simulations

Common Crashes


Q: What is the difference between enzo-dev (week-of-code) and the stable branch? Should I only use the stable branch?


The “week-of-code” branch of enzo-dev is the primary development branch, which is updated on a fairly regular basis (the name “week-of-code” is historical). Changes are migrated into the stable branch on a roughly annual basis. In general, if you want code that is somewhat more reliable but may be significantly behind the cutting-edge Enzo version, you should use the ‘stable’ branch. If you are comfortable with more recent (and thus possibly less reliable) code, you should use the “week-of-code” branch.