
0. Introduction

BART has a build system based on GNU Make. The build system
offers many features for users and developers: BART can be
built on different architectures, with different compilers,
and with various optional features. This makes it easy
to use BART in different environments, on a laptop, a
multi-GPU system, a HPC cluster, or in the cloud. The build
system also supports running system and unit tests.

To make developing more fun, the makefile is optimized for
extremely fast builds. Using parallel builds, BART can be built
from scratch in about five seconds. After changing a single
source code file it is usually possible to rebuild the binary in 
less than a second. This is accomplished by automatically
maintaining dependencies between object files and incrementally
updating the binaries from object stored in libraries.


1. Building BART

1.2. Main Build Targets

1.2.1. Default

By default, the main 'bart' binary will be built with:

	make

or

	make bart


1.2.1. Building Individual Commands


Individual BART commands can be built as standalone binaries:

	make <command>

All BART commands can be built with:

	make all


Attention: If the BART_TOOLBOX_PATH is set, the 'bart' tool will call
the standalone tool and not the built-in tool. This can be used
to selectively update individual tools, but can also cause
confusion.



1.2.2. Testing

System and unit tests can be build and run with:

	make test
	make utest

To run individual tests:

	make tests/test-pics-cs


1.2.3. Cleaning Up

To clean up working directory, run:

	make clean

To also remove all built commands, run:

	make allclean



1.3. Libraries

As a side effect of build the main 'bart' tool, static libraries
are generated in 'lib/'.



2. Local Configuration

The build can be configured by setting or adding variables.

2.1. Makefile.local

It is recommended to put this variables into a file called
'Makefile.local' in the main BART directory. This file is
then automatically included. By having local configuration
is a separate file, local changes are not overwritten when
BART is updated and do not cause conflicts when using a
version control system.


2.2. Makefile.<machinename>

It is also possible to put machine-specific configurations
variables in a Makefile.<machinename> where <machinename>
is the name of the machine as returned by 'uname -n'.


2.3 Custom Makefiles directory

Additional Makefiles can be included by placing them in the
Makefiles directory. All files matching the expansion
Makefiles/Makefile.* are automatically included in the build.
See Makefiles/README.md for example files.



3. Build Options

3.1. Adding New BART Commands

	# add new tool (src/foo.c) to list of targets
	XTARGETS += foo

	# dependencies for foo
	MODULES_foo += -llowrank


3.2. Build Flags

3.2.1. Silent Builds

Silent builds can be activated with the following option:

	MAKEFLAGS += --silent


3.3.2. Parallel Build

Parallel builds can be activated with the following option:

	PARALLEL=1



3.3. Optional Features

Some BART features are optional, because they depend on the other
libraries or features which are not available everywhere.

3.3.1. CUDA

Support for CUDA can be turned on. It may be necessary to also
provide the base path for CUDA installation.
CUDA is supported starting with version 8, however, newer versions
are recommended.

	CUDA=1
	CUDA_BASE=/usr/


3.3.2. OpenMP

OpenMP can be turned off for compilers which do not support
it properly (.e.g. clang):

	OMP=0


3.3.3. FFTW Threads

It is possible to turn off FFTW threads if the library is
not available:

	FFTWTHREADS=0


3.3.4. ISMRM Raw Data Format

If the ISMRMRD library is installed, preliminary support for 
the ISMRM raw data format can be activated:
	
	ISMRMRD=1

3.3.5. TensorFlow

Integration with TensorFlow is possible using the
C API of TensorFlow, which can be downloaded from
here:

https://www.tensorflow.org/install/lang_c

See tensorflow.txt for more information on conventions used.

TensorFlow support can then be activated with:

	TENSORFLOW=1
	TENSORFLOW_BASE=/opt/tensorflow/

3.3.6 MPI

Support for MPI can be turned on. It is recommended to use Open MPI as
MPI implementation as this enables automatic detection of CUDA-aware 
MPI. Moreover BART reads environment variables exported by the Open MPI
implementation of mpirun to automatically activate run-time support for MPI.

	MPI=1



3.4. Compiler

3.4.1. Different Compiler

If different compilers or compiler versions are installed,
it is possible to override the default compiler:

	CC = gcc-4.8
	#CC = gcc-5
	#CC = clang-3.5


3.4.2. Different CFLAGS

Different CFLAGS can be set like this:

	CFLAGS= -g -O2 -ffast-math


3.4.3. Static Linking

Static linking can be used to build binaries which do not
depend on external shared libraries. This might be useful if
BART is to be deployed on a different machine where it is
difficult to install required dependencies.

	SLINK=1



