tarch: 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 CentOS possible default full paths are:

/usr/lib64/mvapich-psm/bin/tarch - from package: mvapich-psm
/usr/lib64/mvapich/bin/tarch - from package: mvapich
/usr/lib/mvapich/bin/tarch - from package: mvapich

You may install the required package with command yum install {package}

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