tutorials/foam/index.md

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\defgroup tutorial_FOAM FOAM tutorials
\ingroup Tutorials
\brief Examples showing how to use FOAM.

### What is FOAM ?

FOAM is simplified version of multi-dimensional general
purpose Monte Carlo event generator (integrator) with hyper-cubical
"foam of cells". Certain features of full version of FOAM are omitted.
mFOAM is intended  as an easy to use tool for MC
simulation/integration in few dimensions. It relies heavily on ROOT package,
borrowing persistency of classes from ROOT. mFOAM can be easily used from
the ROOT shell. For more difficult problems the full FOAM may be better.

### How to run application programs ?

The application program can be run in two modes: it can be simply
intepreted by CINT or compiled. The first method is simpler but
results in slower execution. The second method employs ACLiC -
The Automatic Compiler of Libraries, which automaticates the
process of compilation and linking.

In $(ROOTSYS)/tutorials there are 3 demonstration programs:

#### foam_kanwa.C
is a simple example how to run FOAM in interactive
mode. To run this macro issue the  following simple command from the
Linux shell:

```cpp
  root foam_kanwa.C
```

or from CINT:

```cpp
  root [0] .x foam_kanwa.C
```

Simulation will start and graphical canvas with plot
of the distribution function appear. In this example
we defined the distribution function simply as a global
function function Camel2.

#### foam_demo.C
shows usage of FOAM in compiled mode, which is
the preferred method.  The integrand function is defined
now as a Density method from class TFDISTR inheriting from
abstract class  TFoamIntegrand. User can modify interface to
integrand function according to their needs but they should
always remember to define Density  method which provides the
density distribution.
Enter CINT interpreter and type:

```cpp
  root [0] gSystem->Load("libFoam.so")
  root [1] .x foam_demo.C+
```

to load FOAM library, compile and execute macro foam_demo.C.
A shared object foam_demo_C.so is created in the current
directory. At the end of exploration phase FOAM object
including distribution function will be written to disk.

#### foam_demopers.C
demonstrates persistency of FOAM classes.
To run this macro type:

```cpp
  root [0] .x foam_demopers.C
```

Program reads the FOAM object from disk, checks its
consistency and prints geometry of cells. Next starts the
the generation. It can be interpreted directly by CINT
because compiled TFDISTR class is already available in
foam_demo_C.so library.