gecode: 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/mp/bin/gecode - from package: mp
/usr/lib/mp/bin/gecode - from package: mp

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

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