A multi-process program to solve an exponential function using a master-worker architecture.
The program uses the following algorithm to calculate e^x
e^x = 1 + x^1/1! + x^2/2! + x^3/3! + ... + x^n/n!
It adopts the master-worker architecture, which populates multiple child processes to calculate each individual (x^n/n!). The master program waits for the progress of each worker program using epoll() or select().
worker.c describes the worker model, and master.c describes how master interacts with worker instances.
In worker.c, exponentiate() calculates the value of (x^n/n!) and convert it into a double. Noe that in 64-bit systems, the largest double is 2^53. Hence this program does not work for (x^n)s or (n!)s that is larger than 2^53.
In master.c, spawn_a_worker() describes how master spawns a new child worker; scan_workers() determins whether any reading end of a pipe is ready; on_rfd_ready() reads data from the ready read files and spawns a new child process if necessary.
System calls pipe(), fork(), execl(), dup2() are used in this program.
To build, use:
make
You may want to use
make clean
to clean up the previous compilation.
Use
make worker
to make the worker executable.
Use
make master
to compile the master executable, together with the worker executable.
To run, use
./master --worker_path <WORKER_PATH> --num_workers <NUM_WORKERS> --wait_mechanism <MECHANISM> -x <X> -n <N>
where
- WORKER_PATH is the path of the worker executable (see below for detail);
- NUM_WORKERS is the maximum number of child worker processes that can be spawned simultaneously;
- MECHANISM is the mechanism used by master to wait for worker processes, right now it supports 'select' and 'epoll';
- X is the power in the exponential expression of number e;
- N is the number of components in the polynomial function;
On success of the master execution, you will see the message Final Result : <value> appear after a series of worker messages.
Use
./worker -x <X> -n <N>
where
- X is x in the (x^n/n!) expression;
- N is n in the (x^n/n!) expression;
On success of the master execution, you will see the message x^n / n! : <value> appear.
To test, use
make test-epoll
to test the master program with x value 2, n value 12, and 5 workers using epoll mechanism
Use
make test-select
to test the same call with select mechanism
Note that make check directly points to make test-epoll.
The program cannot calculate any single expression that is bigger than 2^53 in 64-bit systems.
For example, when x is 2, and n is 60, the single expression x^n is bigger than 2^53. The resulting value from master program would be far from e^2.