# Macro "**relauncherFunctionFlowrateCJit.C**"

## Objective

The goal of this macro is to show how to handle the C++-written function using a pointer to the 
function (and not the name as for the macro in [](#use_cases_macro_relauncher_cint)). This function 
has been presented, at least its equation (see {eq}`flowrate_function`) and would be interface 
through the `TCJitEval` class in the {{Relaun}} module. A special discussion will be held in the next 
few lines about the way the compilation is done.

## Macro

{{
    "```{literalinclude} " + parent_dir
    + "/roottest/uranie/doc/relauncher/use_cases/cpp/relauncherFunctionFlowrateCJit.C"
    + "\n"
    + ":language: cpp\n"
    + "```"
}}

The very first part of the macro is slightly different from [](#use_cases_macro_relauncher_cint_macro) 
as it is now compulsory to write explicitly the include line for the pre-processors. The use of 
namespaces is declared along, but this time only because this is convenient not to recall these long 
names every time.

{{
    "```{literalinclude} " + parent_dir
    + "/roottest/uranie/doc/relauncher/use_cases/cpp/relauncherFunctionFlowrateCJit.C"
    + "\n"
    + ":language: cpp\n"
    + ":lines: 1-11\n"
    + "```"
}}

The definition of the `flowrateModel` function is then made right before entering the main function. 
At this level a break is needed to explain the risen antagonism between the two possible compilation 
and the way to call them. This issue is entirely described by the following two lines:

{{
    "```{literalinclude} " + parent_dir
    + "/roottest/uranie/doc/relauncher/use_cases/cpp/relauncherFunctionFlowrateCJit.C"
    + "\n"
    + ":language: cpp\n"
    + ":lines: 27,28\n"
    + "```"
}}

Let's talk about the two cases:
- ACLIC: one should remove the second line and put the first one instead (after commenting it out of 
course). The compilation is then done by calling: 

    ```bash
    root -l relauncherFunctionFlowrateCJit.C+
    ```

    - PROS: this will give you the hand at the end of execution, leaving the display opened to handle 
    plots for instance.
	
    - CONS: this will create several useless files and will need non-trivial manipulation if extra 
    headers and libraries are needed.

- Standalone: leaving the macro as it is, the compilation on Linux is done by writing a line such as:

    {{
        "```{literalinclude} " + parent_dir
        + "/roottest/uranie/doc/relauncher/use_cases/cpp/relauncherFunctionFlowrateCJit.sh"
        + "\n"
        + ":language: bash\n"
        + ":lines: 3\n"
        + "```"
    }}

    An equivalent command on Windows would be:

    {{
        "```{literalinclude} " + parent_dir
        + "/roottest/uranie/doc/relauncher/use_cases/cpp/relauncherFunctionFlowrateCJit.ps1"
        + "\n"
        + ":language: ps1\n"
        + ":lines: 18\n"
        + "```"
    }}

    - PROS: pure C++ compilation resulting in a single executable file (here *CJitTest*). It's easy 
    to include more headers and libraries if your code needs them.

    - CONS: this will not leave the display opened, unless you do so through a `TApplication` ({{root}}-class).

Whatever the chosen solution, the only difference with previous macro is the assessor creation: 

{{
    "```{literalinclude} " + parent_dir
    + "/roottest/uranie/doc/relauncher/use_cases/cpp/relauncherFunctionFlowrateCJit.C"
    + "\n"
    + ":language: cpp\n"
    + ":lines: 49\n"
    + "```"
}}

The rest it completely transparent and leads to the creation of the following plot.

## Graph

{{
    "```{" "figure" "} " + parent_dir +
        "/roottest/build/uranie/doc/relauncher/use_cases/cpp/cjit/relauncherFunctionFlowrateCJit.png\n"
    ":align: center\n"
    ":name: usecases_relauncherFunctionFlowrateCJit\n"
    + figure_scale + "\n"
    "\n"
    "Representation of the output as a function of the first input with a colZ option\n"
    "```"
}}