mpireconfig.dat: 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/mpireconfig.dat - from package: mvapich-psm
/usr/lib64/mvapich/bin/mpireconfig.dat - from package: mvapich
/usr/lib/mvapich/bin/mpireconfig.dat - from package: mvapich

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

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