IBAM, the Intelligent Battery Monitor
http://ibam.sourceforge.net/
1. Description
IBAM is an advanced battery monitor for laptops, which uses statistical and
adaptive linear methods to provide accurate estimations of minutes of
battery left or of the time needed until full recharge. It is available as
shell utility, gkrellm plugin and is included in pbbuttons.berlios.de .
Your system needs to have a proc-filesystem and either apmd, acpi, pmu or
sysfs to be installed.
IBAM is a GPLed Open Source Project. You are coordinally invited to join!
2. Building the shell utility
First steps with IBAM:
To build IBAM simply enter:
make
Then you need to build initial statistics, so enter (*)
watch -n10 ./ibam
and unplug the power source from your laptop. IBAM will now save the time
intervals between changes in battery status, by reading /proc/apm (or the
acpi or the pmu interface). IBAM will already tell you about its
estimations, but they will be as inaccurate as the information of the apmd
or apm-bios. Wait and drink coffee. It should be noted that using one of the
gkrellm-plugins is an alternative to using the watch-statement.
As soon your battery is empty (hope you didn't lose any data.. ;), replug
the power and let ibam continue recording the characteristics of your
system. Meanwhile you may invoke
./ibam -ra --plot
to get some statistics.
The more often you run or watch ibam, the smoother the statistics will get
and the more accurate ibam will be. If you enabled the additional profiling
by "--profile", then you can also compare the statistics to the latest
measurements, i.e. the last 10 samples (if there are that many):
./ibam -r --plot=10
IBAM assumes, that the BIOS will at least be able to report a remaining
battery level percentage of 5 percent- for some laptops this is already the
point of shutdown, so this will be taken into consideration via the so
called "soft low limit". As soon IBAM sees a lower percentage, this "soft"
limit decreses to the lowest seen (and therefore somewhat safe) value. If
your laptop shuts down well above 5 percent, you may increase this soft
limit using
./ibam --softlowlimit=10
but this will only work, if IBAM has not seen lower values before. But if
IBAM is in error, or if you prefer staying away from such low value, you
may set a hard limit for your lowest safe percentage via:
./ibam --hardlowlimit=10
To disable the limits, just specify a limit of 0%.
3.1. Building the gkrellm2 plugin
If you have the appropriate libraries (gtk+-2, gkrellm-devel)
installed, you may also build the krell-plugin of ibam by entering
make krell
You can test this plugin using
gkrellm -p ibam-krell.so
or copying the library ibam-krell.so into your ~/.gkrellm/plugins/ and
enabling the plugin within gkrellm after you had restarted it.
3.2. Building the gkrellm1 plugin
If you have the appropriate libraries (gtk, imllib, gkrellm-devel)
installed, you may also build the krell-plugin of ibam by entering
make krell1
You can test this plugin using
gkrellm -p ibam-krell1.so
or copying the library ibam-krell1.so into your ~/.gkrellm/plugins/ and
enabling the plugin within gkrellm after you had restarted it.
3.3. Using the gkrellm-plugin
On the plugin the marker will always show the battery percentage. When
running on batteries, it will show "batt" and the adaptively computed time
left. When charging it will show "chrg" and the adaptively computed time
left until full charge. If the battery is full, the text will be "full" with
the total battery time.
The gkrell-plugin will read the current profile only once at start and
update the profile when necessary. Thus you may also create the initial
profile with this plugin. You can always use the ibam-command to get more
detailed statistics.
You can find gkrellm at:
http://www.gkrellm.net/
4. Installing
You may install ibam using the
make install
command. This will install ibam into /usr/local/bin and the gkrellm-plugin
in /usr/local/libs/gkrellm/plugins if you had built the plugin as well. You
may also create a RPM with
make rpm
which can be installed as root using the rpm utility
rpm -Uvh ibam-(VERSION)-1.i386.rpm
It is planned to create a debian package by
make deb
"which will compile a debian package including debian source packages,
all of them unsigned (-us unsigned source -uc unsigned compiled) using
fakeroot as get_root_cmd. dpkg-buildpackage checks for build-depends,
however fakeroot will not be in the build-depends since anyone is free to
use su, sudo, super...."- the latter was contributed by Martin Wuertele. But
yet it's untested and I don't know how to do it... ;)
5. File formats
The file formats changed since 0.1, but you may import the old profiles
using the --import option in the directory the 0.1 version was started in.
IBAM will now save the profiles and other informations in the directory
~/.ibam where you will find the files ibam.rc, battery.rc and charge.rc.
Thus if you plan to use the same statistics for different users, make sure
that this directory is soft-linked to all participants and with appropriate
permissions on it. Here are the current file structures:
ibam.rc: (current ibam status)
0.5 1131300315 97 1.0523 2 2 1 23 0 1 5 0
The first number describes the version of IBAM that create this file. The
next is the time-stamp when IBAM noticed the last change in APM status. The
third number shows the last recorded APM battery percentage. The fourth
number shows the current adaptivity factor, followed by the number of
measurements that were taken into consideration. The sixth shows the last
status (charging, on battery or undefined). The seventh number defines
whether profiles should be recorded, followed by the number of the current
profile and the next says if this profile is active right now. The last two
numbers are the soft and hard lowest safe limits for battery percentages,
zero if they are disabled.
battery.rc and charge.rc: (battery and charge profiles)
[...]
94 109.852 26.4915 25
93 109.992 26.3673 25
[...]
Here you can see the average number in the second column of seconds per
percentage unit in first column. The third column shows the standard
derivation (sqrt(s^2)) the fourth the number of samples the statistics in
these lines are based on.
6. ALPHA status
This software is in alpha-status, please tell me about your experiences and
send me your battery and charge profiles for further analysis. Thanks to
profiles that were sent to me, it turned out that the accuracy can even be
increased by more intelligent profiling. So far you may alread start
creating the profiles by enabling the additional per cycle profiling, but
yet this information will not be used by the current version, but hopefully
in one of the future releases.
7. Future Plans and Optional Profiling
Ibam gains its accuracy by collecting statistics about (dis)charge time for
each percentage. You may visualize this as simple table where each
percentage is mapped to a time period. Yet there are different "profiles"
one cannot neglect, such as different power saving modes. Currently ibam
tries to deal with this by means of linear adaption: On each percentage
step the ratio of expected to estimated time is computed and averaged
over the cycle so far. This averaged ratio is used as an adaption to
different power demands- but as batteries are highly unlinear, this is just
a rough estimate.
The mathematical solution is to introduce statistics based on current
percentage and history. The tables would grow huge, but may stay managable
by means of compression of sparse matrices. Yet each estimate computation
would yield up to a hundred matrix multiplications with approximately
100x100 cell matrices. This gets to a point where the measurement may even
influence power consumption due to excessive cpu usage... ;)
But looking at the sparsity of the matrices, which we should assume, we
recognize the profiles mentioned before: These will be certain paths the
(dis)charge will follow more or less accurately. Thus it's reasonable just
to record a sufficiently high number of paths and compute the distance of
the current measurements to the paths we saw before and take a
"distance-weighted average" of our memory as an estimation. This method
incorporates the advantages of the old method, but uses the information of
the more general method, yet using far less computational power- limited by
the number of profile-realizations we are keeping.
Therefore enable (./ibam --profile) the additional profiling of ibam to
already collect data for the next-generation ibam, which will then give you
even far more accurate results than the current version.
8. Author and Contact address
Sebastian Ritterbusch, IBAM@ritterbusch.de
Special thanks go to:
Mohanty Mitrabhanu for his scientific paper mentioning ibam
Dan Egnor for his sweetcode article
Martin Wuertele for the debian port
Seth Golub for code improvements
Misha Nasledov for the gkrellm2-patch
Matthew Richardson for the gentoo support
Florian Ragwitz for the PMU support
Matthias Grimm for the extended PMU support and pbbuttons.berlios.de
Peter Gaal for testing and the APM bugfix
Brad Sawatzky for the same APM bugfix
and all others for their motivating mails! :)
9. Footnote
(*) On some RedHat and Mandrake Distributions (as of Aug 2001) "watch"
shows redraw errors in the KDE terminal. You can prevent this from happening
by changing the TERM variable before:
export TERM=xterm-color