Running and Verifying Code_Saturne on Multiple Nodes

Use PuTTY to log in to the server as the root user.

Create a case directory and go to the directory.

cd /path/to/CODE_SATURNE/
mkdir TESTCASE
cd TESTCASE

Run the following command to create a case:
```
code_saturne create -s test -c case1
```
In the previous command, test indicates the user-defined study name and case1 indicates the user-defined case name. You can change them based on the actual situation. After this command is run, a test directory is generated in the current directory, and the case1, MESH, and POST directories are generated in the test directory.

Run the following command to copy the test case file:

cp /path/to/CODE_SATURNE/code_saturne-6.0.2/examples/1-simple_junction/mesh/*  test/MESH -rf
cp /path/to/CODE_SATURNE/code_saturne-6.0.2/examples/1-simple_junction/case1/setup.xml test/case1/DATA -rf

Run the following command to set the MPI environment variable:

export CS_MPIEXEC_OPTIONS="--allow-run-as-root --mca btl ^openib"

Run the following command to initialize the case:

code_saturne run --initialize --param=/path/to/CODE_SATURNE /TESTCASE/test/case1/DATA/setup.xml --case=/path/to/CODE_SATURNE /TESTCASE/test/case1

If the following information is displayed, the initialization is successful:

***************************** 
  Preprocessing calculation 
*****************************

Run the following command to create the hostfile file and add node information:
```
echo -e 'node1\nnode2\n…\nnodex' > /path/to/HOSTFILE
```
In the previous command, node1, node2, ..., and nodex indicate the host names of the nodes. You can run the hostname command to query the host names. \n indicates a newline character.
Run the following command to go to the directory of test cases:
```
cd /path/to/CODE_SATURNE/TESTCASE/test/case1/RESU/year+month+day-hour+minute_round
```
A log is generated in the RESU directory each time a job is run. The log directory format is YearMonthDay-HourMinute_Sequence number of job executions in the same minute. For example, the 20200330-2104 directory contains the log of the first job execution at 21:04 on March 30, 2020, and the 20200330-2104_1 directory contains the log of the second job execution at 21:04 on March 30, 2020.
Run the following command to run the test case on multiple nodes:
```
time mpirun --allow-run-as-root --mca btl ^openib -N 96 -x OMP_NUM_THREADS=1 --hostfile /path/to/HOSTFILE ./cs_solver --mpi
```
Elapsed time: XX s in the performance.log file indicates the performance. A smaller value indicates a better performance.

Figure 1 shows the command output:

Figure 1 An example result

Parent topic: Running and Verifying Code_Saturne