Another restriction is that the width of memory addresses in Tcl/Tk and OOMMF must match. Most general-purpose operating systems today use primarily 64-bit memory addresses, but for backwards compatibility can also run programs using 32-bit memory addresses. However, a 64-bit executable cannot link against a 32-bit library, or vice versa. Therefore, if you have a 64-bit Tcl/Tk installed, then you will need a 64-bit OOMMF, and likewise a 32-bit Tcl/Tk needs a 32-bit OOMMF.
Another restriction is that while OOMMF can be built to run in parallel across multiple cpu cores on a shared memory machine using threads, to do this requires that the installed Tcl/Tk be thread-enabled. Typical Tcl/Tk installs on Windows and macOS are thread-enabled. Tcl/Tk installs on recent releases of Unix also tend to be thread-enabled, but some older versions have non-threaded Tcl/Tk installs. If your system Tcl/Tk install is non-threaded, then you can either build a non-threaded version of OOMMF, or else you can make an additional, threaded Tcl/Tk install, for example under your home directory or /usr/local. Be aware that if you have multiple Tcl/Tk installations on your system then you need to be careful to use the proper tclsh whenever you build or launch OOMMF.
If you download OOMMF with pre-built binaries, then it is imperative that you select the download that matches the major+minor release number and memory address width of the Tcl/Tk you want to run OOMMF with. On the other hand, if you build OOMMF from source, then the tclsh you use to run the build process is inspected to determine relevant information about the local Tcl/Tk environment. Some adjustment of the platform configuration file, as described in the next section, may be necessary. Also, in many cases the compilers used to build 32-bit and 64-bit executables are different--if you encounter build problems, double-check that the proper compiler is being used.
All of the OOMMF downloads containing pre-built binaries are built for use with thread-enabled Tcl/Tk. You will need to build from source if you want a non-threaded OOMMF. The build scripts will detect if the tclsh running the build procedure is non-threaded and will build OOMMF appropriately.
In all cases, use the platform configuration check described in the next section to verify the compatibility of your Tcl/Tk and OOMMF installs.