Update README.md

README.md

@@ -7,4 +7,18 @@
 
 ## Later evolutions
 
-* On-the-fly optimization
\ No newline at end of file
+* On-the-fly optimization
+
+## Usage
+
+Dependency: on Debian `libginac-dev ginac-tools`
+
+Compilation:
+```
+mpic++ -O3 -g -Wall -o tensormatrix_mpi tensormatrix_mpi.cpp -lginac  -Wno-unused-variable
+```
+
+Running:
+```
+mpiexec -n 17 ./tensormatrix_mpi
+```