Using the Bresenham algorithm it's safe to assume that if the axis
with the most steps is done, all other axes are done, too.
This way we save a lot of variable loading in dda_step(). We also
save this very expensive comparison of all axis counters against
zero. Minor drawback: update_current_position() is now even slower.
About performance. The slowest step decreased from 719 to 604
clocks, which is quite an improvement. Average step time increased
for single axis movements by 16 clocks and decreased for multi-
axis movements. At the bottom line this should improve real-world
performance quite a bit, because a printer movement speed isn't
limited by average timings, but by the time needed for the slowest
step.
Along the way, binary size dropped by nice 244 bytes, RAM usage by
also nice 16 bytes.
ATmega sizes '168 '328(P) '644(P) '1280
Program: 19564 bytes 137% 64% 31% 16%
Data: 2175 bytes 213% 107% 54% 27%
EEPROM: 32 bytes 4% 2% 2% 1%
short-moves.gcode statistics:
LED on occurences: 888.
LED on time minimum: 326 clock cycles.
LED on time maximum: 595 clock cycles.
LED on time average: 333.62 clock cycles.
smooth-curves.gcode statistics:
LED on occurences: 23648.
LED on time minimum: 318 clock cycles.
LED on time maximum: 604 clock cycles.
LED on time average: 333.311 clock cycles.
triangle-odd.gcode statistics:
LED on occurences: 1636.
LED on time minimum: 318 clock cycles.
LED on time maximum: 585 clock cycles.
LED on time average: 335.233 clock cycles.
##############################################################################
# #
# Teacup - lean and efficient firmware for RepRap printers #
# #
# by Triffid Hunter, Traumflug, jakepoz, many others. #
# #
##############################################################################
For installation instructions, see
http://reprap.org/wiki/Teacup_Firmware#Simple_Installation and/or
http://reprap.org/wiki/Teacup_Firmware#Developer_Installation
For documentation, see
http://reprap.org/wiki/Teacup_Firmware
##############################################################################
# #
# This firmware is Copyright (c) ... #
# 2009 - 2010 Michael Moon aka Triffid_Hunter #
# 2010 - 2013 Markus "Traumflug" Hitter <mah@jump-ing.de> #
# #
# This program is free software; you can redistribute it and/or modify #
# it under the terms of the GNU General Public License as published by #
# the Free Software Foundation; either version 2 of the License, or #
# (at your option) any later version. #
# #
# This program is distributed in the hope that it will be useful, #
# but WITHOUT ANY WARRANTY; without even the implied warranty of #
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the #
# GNU General Public License for more details. #
# #
# You should have received a copy of the GNU General Public License #
# along with this program; if not, write to the Free Software #
# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA #
# #
##############################################################################
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