Building Your Own Super Computer - Testing Your Linux Cluster
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The first program we will run is cpilog. From within the mpich-.2.2.3/examples/basic directory, copy the cpilog exec file (if this file isn't present, use make command again) to your top-level directory. On our cluster, this is either /root (if we are logged in as root) or /home/DevArticle, if we are logged in as DevArticle (we have installed MPICH both places).
Next, from your top directory, rcp the cpilog file to each node in your cluster, placing the file in the corresponding directory on each node. For example, if I am logged in as DevArticle on the master node, I'll issue rcp cpilog Slave:/home/ DevArticle to copy cpilog to the DevArticle directory on Slave. I'll do the same for each node (if there are more than two nodes). If I want to run a program as root, then I'll copy the cpilog file to the root directories of all nodes on the cluster.
Congratulation your supercomputer (Linux cluster) is ready to run MPI programs!
Once the files have been copied, I'll type the following from the top directory of my master node to test my cluster:
mpirun -np 1 cpilog
This will run the cpilog program on the master node to see if the program works correctly. Some MPI programs require at least two processors (-np 2), but cpilog will work with only one. The output looks like this:
pi is approximately 3.1415926535899406,
Error is 0.0000000000001474
Process 0 is running on Server.home.net
wall clock time = 0.360909
Now try all two nodes (or however many you want to try) by typing: mpirun -np 2 cpilog and you'll see something like this:
pi is approximately 3.1415926535899406,
Error is 0.0000000000001474
Process 0 is running on Master.home.net
Process 1 is running on Slave.home.net
wall clock time = 0.0611228
The number following the -np parameter corresponds with the number of processors (nodes) you want to use in running your program. This number may not exceed the number of machines listed in your machines.LINUX file plus one (the master node is not listed in the machines.LINUX file).
To see some graphics, we must run the pmandel program. Copy the pmandel exec file (from the mpich-1.2.2.3/mpe/contrib/mandel directory) to your top-level directory and then to each node (as you did for cpilog). Then, if X isn't already running, issue a startx command. From a command console, type xhost + to allow any node to use your X display, and then set your DISPLAY variable as follows:
DISPLAY=Server:0 (be sure to replace Server with the hostname of your master node). Setting the DISPLAY variable directs all graphics output to your master node. Run pmandel by typing: mpirun -np 2 pmandel
The pmandel program requires at least two processors to run correctly. You should see the Mandelbrot set rendered on your master node.
Adding more processors (mpirun -np 10 pmandel) should increase the rendering speed dramatically. The mandelbrot set graphic has been partitioned into small rectangles for rendering by the individual nodes. You can actually see the nodes working as the rectangles are filled in. If one node is a bit slow, then the rectangles from that node will be the last to fill in. It is quite fascinating to watch.
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