polarssl_mpi_demo: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/polarssl_mpi_demo - from package: libpolarssl-runtime

You may install the required package with command apt-get install {package}

Error in other languages:
polarssl_mpi_demo: bevel nie gevind nie
polarssl_mpi_demo: comandă negăsită
polarssl_mpi_demo: comando não encontrado
polarssl_mpi_demo: commande introuvable
polarssl_mpi_demo: command not found
polarssl_mpi_demo: käsku ei ole
polarssl_mpi_demo: không tìm thấy lệnh
polarssl_mpi_demo: komanda nerasta
polarssl_mpi_demo: Kommando nicht gefunden.
polarssl_mpi_demo: kommandot finns inte
polarssl_mpi_demo: komut yok
polarssl_mpi_demo: nie znaleziono polecenia
polarssl_mpi_demo: níor aimsíodh an t-ordú
polarssl_mpi_demo: no se encontró la orden
polarssl_mpi_demo: no s'ha trobat l'ordre
polarssl_mpi_demo: opdracht niet gevonden
polarssl_mpi_demo: parancs nem található
polarssl_mpi_demo: perintah tidak ditemukan
polarssl_mpi_demo: príkaz nenájdený
polarssl_mpi_demo: příkaz nenalezen
polarssl_mpi_demo: команда не найдена
polarssl_mpi_demo: командата не е открита
polarssl_mpi_demo: 命令找不到
polarssl_mpi_demo: コマンドが見つかりません