Plotting Data in GDB

Using GDB to debug programs is great and all, but if you work with Scientific data then one really critical function is the ability to plot a long array or vector, to see how the solution is evolving at various stages.

After a bit of tinkering, I was able to take this code snippet and modify it for my needs. It had just a few problems:

The syntax they used for labeling things fell apart when I was using Eigen vectors, the -> became shell redirects.

It didn’t link very long (100+) entry arrays.

So I modified it like so:


# plot1d.gdb
#
# Copyright (C) 2008 Florian Lorenzen
# - Taken from https://sourceware.org/gdb/wiki/PlottingFromGDB
# Modified by Randall Hand to actually make it work.
# original version seemed to badly handle variable names
# like esf->data[0]@1024 (turning the > into a pipe redirect)
#
# Plot an expression that expands to {x1, x2, ..., xN}, i. e.
# N numbers using gnuplot.
#
# This file is for the GNU debugger 6.x.
#
# It writes temporary files named __plot1d.dump, __plot1d.dat, __plot1d.gp, so
# you should not have files of the same name in the working directory.
#
# It requires sed, awk, and gnuplot available in the $PATH.
# plot1d_opt_range <expr> <opt> <range>
#
# Plot the points of <expr> passing <opt> as plot options using
# <range> in the set yrange command.
define plot1d_opt_range
shell rm -f /tmp/__plot1d.dump /tmp/__plot1d.dat /tmp/__plot1d.gp
set logging file /tmp/__plot1d.dump
set logging on
set logging redirect on
set height 0
set print elements unlimited
output $arg0
set logging off
set logging redirect off
shell awk '{printf("%s", $0)}' < /tmp/__plot1d.dump | \
sed 's/^{\(.*\)}$/\1/;s/, */\n/g' > /tmp/__plot1d.dat
shell echo 'plot "/tmp/__plot1d.dat" title "$arg0"; pause -1 "Press enter to continue"' > /tmp/__plot1d.gp
shell gnuplot /tmp/__plot1d.gp
# shell rm -f /tmp/__plot1d.dump /tmp/__plot1d.dat /tmp/__plot1d.gp
end
# plot1d <expr>
#
# Just plot the points of <expr>.
define plot1d
plot1d_opt_range $arg0 "" "[*:*]"
end
# plot1d_opt <expr> <opt>
#
# Plot the points of <expr> passing <opt> to the
# plot command after the datafile. So, one can pass
# "with lines" here.
define plot1d_opt
plot1d_opt_range $arg0 $arg1 "[*:*]"
end

With this file placed somewhere and executed, you can then simply do plot1d data[0]@128 to get a nice plot of the first 128 values of `data`.

And if you like it so much you want to keep it, simply add source plot1d.gdb (which a path to wherever you put it) to your ~/.gdbinit