/* Single Author Info:
*  abpatwar Aditya B Patwardhan
*/

Introduction:
-------------
The synchronization primitive 'barrier' has been implemented using UNIX signals.

Files provided in the implementation:
-> mybarrier.h
-> mybarrier.c


mybarrier.c contains the following methods:
-> mybarrier_init()
-> mybarrier_wait()
-> mybarrier_destroy()


Barrier:
--------
The barrier provides mechanism to block all threads till all threads reach the barrier.
When all threads reach the barrier, the threads are unblocked.


Implementation details:
----------------------

The barrier is based on the sleep function. 
If the thread is not the last thread, the thread is put to sleep till it is signalled by the last thread.
A dynamically created array stores the TID of the threads put to sleep.
The last thread sends SIGUSR1 signals to the threads that sleep at the barrier.
The last thread re-initilizes the barrier to be reused.

Test Case:
----------
A test file test.c tests the implementation of the barrier.

The program tests 10 threads over 2 barriers.
Each thread adds it's own thread number into an array and then waits at the barrier.
Once all the threads have reached the barrier, the threads proceed to calculate the sum of the elements in the array.
If sum = 45 (sum of all numbers from 0 to 9), then all the threads have successfully waited at the barrier and then calculated the sum.


How to Build:
------------

Refer to the following commands for building ->
Compiling:
     $ make
# This is equivalent to "make all".
# It compiles all the code files, creates the corresponding object files. 
# It also builds the test.c file - a sample test program provided - which tests out the methods in mybarrier.c.

Cleaning:
     $ make clean

Test file:
     $ make test