[Beowulf] how to run HPL on a single machine

I tried to run HPL on a single machine, but it always fails rtes1:/.../hpl/bin/RTES/ mpirun -np 4 xhpl p0_30424: p4_error: Path to program is invalid while starting /.../hpl/bin/RTES/xhpl with rsh on rtes1: -1 p4_error: latest msg from perror: No such file or directory p0_30235: (45.056821)

[Beowulf] a question about running HPL

I am a newbie in distributed computing... I have a problem of running HPL on a single machine. Hope I can get help here. Thanks. After I install HPL on the machine, I try to run it in the bin dir of HPL by "mpirun -np 1 xhpl". But it reports "cannot find mpirun command". Actually I have installed