#cptnHook

##Abstract

cptnHook is a tool which is able to display the values of the arguments passed to mathematical functions in a scientific application (currently exp(x), sqrt(x), sin(x), cos(x), tan(x), asin(x), acos(x), atan(x)).

The initiative to build such a tool is based on the pressing need optimize scientific programs. In more detail, the extensive use of transcendental mathematical functions in scientific applications leads to them accounting for a big portion of the programs' runtime.

The objective is to achieve a drastic optimization of such programs with ad hoc approximations of the mentioned mathematical functions (e.g. polynomial approximations, Pade's approximation). The approximations will depend on the needed precision of the result and the domain of the input parameter.

To achieve this goal it's necessary to have a clear overview of the usage of the mathematical functions in the program. For this purpose the present tool has been implemented. cptnHook provides a measurement of the use of mathematical functions in a program without modifying the application's source code but rather by hooking into the machine code and probing the arguments of the functions.

cptnHook has been implemented with C++ and uses PIN (https://software.intel.com/en-us/articles/pintool) - a dynamic binary instrumentation framework that enables the creation of dynamic program analysis tools - for the purposes of probing the values inserted in mathematical functions and obtaining the stack trace of each mathematical function that is used. The tool is still in beta stage and further development is taking place.

The outputs of the tool are provided in ROOT (https://root.cern.ch/drupal/) format for further on analysis.

##Istallation

###Prerequisites:

1. You need to install ROOT

   go here: https://root.cern.ch/drupal/

   for further documentation on how to install ROOT

###Steps:

1. Simply run the getStarted.sh file with the following command

   sh getStarted.sh

This file will generate all required files and will construct a library called "libcptnHook.so" which you will later on use to hook your program.

2. You can now run this library along any executable. You can try it out with an example that exists in the folder Tests. Simply run the script "Compile_and_Run_Test.sh" with the following command:

   sh Compile_and_Run_Test.sh

For general use remember to set the PINDIR env variable to $PINDIR.

`PINDIR=[directory_where_the_cptnHook_file_was_downloaded]/cptnHook/pin-2.14-71313-gcc.4.4.7-linux`   
`export PINDIR`   
`echo PINDIR`

In order to use the library along a program named "myProg.cpp" you need to first compile it:

`g++ -o myProg myProg.cpp`

and then run it alongside PIN and the cptnHook library:

`$PINDIR/pin -t libcptnHook.so -- ../myProg`