The first step in compiling MRtrix is to invoke the configure script. This will run a series of tests to ensure the required dependencies are installed, and figure out the appropriate compilation settings. By default, this information is stored in the release/config file, ready for use with the build script.

The configure script accepts a number of options, and is influenced by a number of environment variables. These are all described in detail in configure script's online help, produced by invoking it with the -help ption:

 $ ./configure -help

These options should be self-explanatory, and will not be described any further here. This section instead focuses on describing the multi-build feature of MRtrix.

Using multiple co-existing configurations

By default, the configure script will generate a file called release/config, with the relevant settings requested by the options supplied to the configure script. This is a text file consisting of Python commands, which you're encouraged to look through. It is possible to request that the information be stored in a different folder, so that non-standard settings can be used to build a different set of binaries, without affecting the existing set. This is best illustrated with an example:

If we want to generate a configuration for a debug build, the -debug option can be passed to the configure script to generate a suitable configuration for it. If we also supply a suitable name as an argument, the settings will be stored in a file called <name>/config instead of the default release/config. In our case, we chose the name dbg:

$ ./configure -debug dbg

This generates a folder called dbg, wihtin which the new config file resides. This allows the new dbg config to co-exists with the default release build. We can then ask the build script to compile the debug version of the binaries by passing the name dbg as the target:

$ ./build dbg

To avoid naming conflicts with the existing binaries, all intermediate files generated with this command will be placed in the dbg folder instead of the default release folder. The debug version of the command can then be invoked as, for example:

$ dbg/bin/mrconvert in.mif out.nii

This allows any number of configurations to co-exist without interferring with each other. Other potentially interesting configurations include:

one that is statically linked, configured with the -static option. This makes it easy to install on target systems where the required dependencies cannot be installed.
one that does not include the GUI components, configured with the -nogui option.
one that does not include the MRtrix shared library, configured with the -noshared option.
one that is built for a generic CPU, configured by setting the ARCH environment variable. This makes it easy to deploy on other systems whose exact CPU type might not match the system on which the executable are being compiled. Note that by default, ./configure will create a configuration to compile for the native CPU using the -march=native flag to g++.

For example, this creates a static configuration for a generix 64-bit CPU without the GUI components, and creates a target build called server, which can then be compiled alongside the default release build:

$ ARCH=x86-64 ./configure -nogui -static server

MRtrix build type requested: release [command-line only]

Detecting OS: linux
Machine architecture set by ARCH environment variable to: x86-64
Checking for C++11 compliant compiler [g++]: 5.3.0 - tested ok
Detecting pointer size: 64 bit
Detecting byte order: little-endian
Checking for variable-length array support: yes
Checking for non-POD variable-length array support: yes
Checking for zlib compression library: 1.2.8
checking for Eigen 3 library: 3.2.8

writing configuration to file './server/config': ok

$ ./build server
(  1/283) [CC] server/lib/image_io/sparse.o
(  2/283) [CC] server/src/dwi/tractography/weights.o
...

If required, it is also possible to create a configuration by hand. This may be useful in cases where the configuration produced by the configure script does not work as-is, and requires manual editing.