Using MPICH in Amazon EC2
To run mpi programs on Amazon EC2, you first need to have an account to Amazon Web Services (AWS). Assume you are familiar with AWS and you know how to start/stop/terminate Amazon EC2 instances, you can follow the following steps to run mpi programs within a single Amazon EC2 region or cross regions.
Running MPI in a Single Amazon EC2 Region
Install MPI in your cluster
Start a MPI cluster using Amazon EC2 instances. Make sure MPICH2 is properly installed in your cluster. You can download MPICH2 here (http://www.mpich.org/downloads/) and follow the following steps to install.
>>> tar -xzf mpich-3.2.tar.gz >>> cd mpich-3.2 >>> ./configure >>> make >>> sudo make install
If your build was successful, you should be able to see your installed version by typing
>>> mpiexec --version
Configure your MPI cluster
You should have a keypair yourkey.pem attached to the created instances. First setup your environmental variables as follows. You can find the access key and secret key in your Amazon EC2 account.
export AWS_ACCESS_KEY_ID=[ Your access key ] export AWS_SECRET_ACCESS_KEY=[ Your access key secret ]
Try ssh to other instances in your cluster to make sure that your environmental setup is successful.
>>> ssh -i path-to-the-key/yourkey.pem username@other-instance-ip
To enable password-less ssh between instances, do the following for each instance in your cluster.
>>> cp path-to-the-key/yourkey.pem ~/.ssh/id_rsa
Then you should be able to ssh by typing
>>> ssh username@other-instance-ip
Run MPI in your cluster
Save the ip addresses of instances in a file named host_file. You can compile your mpi program and execute it as following.
>>> mpicc mpi_example.c -o example >>> mpiexec -n 2 -f host_file ./example
Running MPI across Multiple Amazon EC2 Regions
If you want to run your code across multiple cloud regions, some modifications are required to enable network communications.
Start your MPI cluster
Create instances in your prefered regions. Make sure the security groups of your instances allow inbound data transfer from other cloud regions. Install MPI as introduced above to all your cluster machines. In Amazon EC2, you can create one instance installed with all required packages and use the image of this instance to create other machines. This will save you some efforts.
Say for example you want to execute in us east and us west regions. Note that, now you should have two keys, each for one region. To enable password-less ssh between instances in different regions, configure the following files.
For instances in the us east region:
>>> cp path-to-the-key/us-east-key.pem ~/.ssh/id_rsa
Concatenate the ~/.ssh/authorized_key files in both us east and us west regions and scp the concatenated file to all instances.
>>> scp -i path-to-the-key/us-west-key.pem username@us-west-instance-ip:~/.ssh/authorized_key ~/.ssh/authorized_key_uw >>> cat ~/.ssh/authorized_key_uw >> ~/.ssh/authorized_key >>> scp -i path-to-the-key/us-west-key.pem ~/.ssh/authorized_key username@us-west-instance-ip:~/.ssh/
For instances in the us west region:
>>> cp path-to-the-key/us-west-key.pem ~/.ssh/id_rsa
Run MPI in your cluster
Save the *public* ip addresses, usually in the form 220.127.116.11 (for example) in your hostfile. Note, do not use the public DNS, which is usually in the form ec2-54-100-1-1.cpmpute-1.amazonaws.com. You can run your mpi program by typing:
>>> mpiexec -localhost host_node_ip -n 2 -f host_file ./example
The host_node_ip is the public ip address of your master node.