SCons

SCons (from Software Construction) is a superior alternative to the classic make utility.

SCons is implemented as a Python script, its "configuration files" (SConstruct files) are also Python scripts. Madagascar uses SCons to compile software, to manage data processing flowing, and to assemble reproducible documents.

• SCons documentation

Useful SCons options

scons -h (help) displays a help message.

scons -Q (quiet) suppresses progress messages.

scons -n (no exec) outputs the commands required for building the specified target (or the default targets if no target is specified) without actually executing them. It can be used to generate a shell script out of SConstruct script, as follows: <bash> scons -nQ [target] > script.sh </bash>

Compilation

SCons was designed primarily for compiling software code. An SConstruct file for compilation may look like <python> env = Environment() env.Append(CPPFLAGS=['-Wall','-g']) env.Program('hello',['hello.c', 'main.c']) </python>

Data processing flows with rsf.proj

The rsf.proj module provides SCons rules for Madagascar data processing workflows. An example SConstruct file is shown below and can be found in bei/sg/denmark <python> from rsf.proj import *

Fetch('wz.35.H','wz')

Flow('wind','wz.35.H','dd form=native | window n1=400 j1=2 | smooth rect1=3') Plot('wind','pow pow1=2 | grey wanttitle=n')

Flow('mute','wind','mutter v0=0.31 half=n') Plot('mute','pow pow1=2 | grey wanttitle=n')

Result('denmark','wind mute','SideBySideAniso')

End() </python> Note that SConstruct by itself does not do any job other than setting rules for building different targets. The targets get built when one executes scons on the command line. Running scons produces

bash$ scons
scons: Reading SConscript files ...
scons: done reading SConscript files.
scons: Building targets ...
retrieve(["wz.35.H"], [])
< wz.35.H /RSF/bin/sfdd form=native | /RSF/bin/sfwindow n1=400 j1=2 | /RSF/bin/sfsmooth rect1=3 > wind.rsf
< wind.rsf /RSF/bin/sfpow pow1=2 | /RSF/bin/sfgrey wanttitle=n > wind.vpl
< wind.rsf /RSF/bin/sfmutter v0=0.31 half=n > mute.rsf
< mute.rsf /RSF/bin/sfpow pow1=2 | /RSF/bin/sfgrey wanttitle=n > mute.vpl
/RSF/bin/vppen yscale=2 vpstyle=n gridnum=2,1 wind.vpl mute.vpl > Fig/denmark.vpl
scons: done building targets.

Obviously, one could also run similar commands with a shell script. What makes SCons convenient is the way it behaves when we make changes in the input files or in the script. Let us change, for example, the smoothing radius in the first Flow command. You can do it with an editor or on the command line...

Command-line options

Command-line options
Name	Meaning
TIMER	Whether to time execution
CHECKPAR	Whether to check parameters
ENVIRON	Additional environment settings
CLUSTER	Nodes available on a cluster
MPIRUN	mpirun command