8. Batch jobs and logs

march will also run as a batch job, its output written to a log file: there, a bar that redraws its line would leave every frame in the file, carriage returns and escape sequences included. forbear knows where it writes:

call bar%initialize(prefix_string='march ', bracket_left_string='[', bracket_right_string=']',  &
                    filled_char_string='#', empty_char_string='.', add_progress_percent=.true.,&
                    add_progress_count=.true., add_eta=.true., add_summary=.true.,            &
                    progress_percent_color_fg='yellow', eta_color_fg='blue',                  &
                    width=30, max_value=real(steps, R8P))

On a terminal:

$ march
march [##############################] 100% 50/50 ETA hh:mm:ss
[done in n.nn s, nn.nn/s]
march: done

With the output sent to a file:

$ march > run.log; cat run.log
march [..............................]   0%  0/50 ETA --:--:--
march [###...........................]  10%  5/50 ETA hh:mm:ss
march [######........................]  20% 10/50 ETA hh:mm:ss
march [#########.....................]  30% 15/50 ETA hh:mm:ss
march [############..................]  40% 20/50 ETA hh:mm:ss
march [###############...............]  50% 25/50 ETA hh:mm:ss
march [##################............]  60% 30/50 ETA hh:mm:ss
march [#####################.........]  70% 35/50 ETA hh:mm:ss
march [########################......]  80% 40/50 ETA hh:mm:ss
march [###########################...]  90% 45/50 ETA hh:mm:ss
march [##############################] 100% 50/50 ETA hh:mm:ss
[done in n.nn s, nn.nn/s]
march: done

• initialize looks at the unit of the bar: when it is the standard output or error and that is a terminal, the bar is interactive, and animates; otherwise it writes a plain line at every 10% (at every frequency% if larger than 1), with no colours, no carriage returns and no escape sequences, then the date and time and the summary lines. The same program, the same calls, a readable log.
• interactive=.true. or .false. forces either mode; the environment variable FORBEAR_INTERACTIVE=1 or 0 does the same for every bar, when the keyword is not passed.
• Bars below the current line (position larger than 0) write nothing in a log.

Signs of life in long jobs

A line every 10% is a fine log for a job of an hour; for a job of two days, ten lines leave hours of silence, and an indeterminate bar writes nothing between its first and last lines. log_interval adds a line whenever that many seconds have passed since the last one:

call bar%initialize(template='solve {count} iterations, {elapsed} elapsed', indeterminate=.true., &
                    log_interval=0.3_R8P) ! in a log, a line at least every 0.3 s (in a real job: minutes)

$ march > run.log; cat run.log
solve 0 iterations, hh:mm:ss elapsed
solve 2 iterations, hh:mm:ss elapsed
solve 4 iterations, hh:mm:ss elapsed
solve 6 iterations, hh:mm:ss elapsed
solve 8 iterations, hh:mm:ss elapsed
solve 10 iterations, hh:mm:ss elapsed

Each iteration of this solver takes 0.2 s: a line every 0.3 s comes every other iteration. In a real job, log_interval=600 gives a line every ten minutes; FORBEAR_LOG_INTERVAL=600 in the job script does it for every bar, without recompiling. On a terminal, log_interval does nothing.

Turning the bars off

disabled=.true. turns a bar off: start and update draw nothing, write still prints its lines. The environment variable FORBEAR_DISABLE=1 turns every bar of the program off, without recompiling:

$ FORBEAR_DISABLE=1 march
march: done

Under MPI every process would draw its own bar on the same terminal: draw the bar of one process only,

call bar%initialize(max_value=real(steps, R8P), disabled=(rank /= 0)) ! rank from MPI_Comm_rank

What you learned

Interactive and log modes, log_interval, interactive, disabled, the FORBEAR_* environment variables, one bar under MPI. Reference: Terminals and logs.

Next: 9. Layout templates.