error when reading datas from a file

No it will read all the lines, as the process isn't permanently stopped with a single "wait;" statement.

There are two problems I see in that code:[list][*]if start_gen isn't initialized at '1' (and by default it will be 'U') then the process will just read all the lines from the file and do nothing with them before going even one ps into the simulation[*]you never assign any value to lnumber and pnumber. By default they will be 0 so you never read the pixel values[/list]