gpaw-plot-parallel-timings: 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/bin/gpaw-plot-parallel-timings - from package: gpaw

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

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