Tag Archives: first

ant dependency graphing with graphviz

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In 2007, I wrote an article about ant dependency graphing in the JavaRanch Journal.  I had cause to try it again to visualize the FIRST robotics complex build scripts.  This time, I’m on Mac.  At the moment, the MacOS version of Graphviz is in beta.  This isn’t critical so giving it a try.

It was easy to install with a wizard to accept license, choose location, etc.  Installation was successful and less than a minute.

The contenders from 2007

  • Ant2Dot – hasn’t changed since 2007
  • Visant – hasn’t changed since 2002
  • Grand – hasn’t change since 2005

Since there haven’t been any updates, my analysis should still be the same.  Since Grand generated the most useful output then, I went with it.

Grand

<?xml version="1.0"?>
<project name="Grand" basedir="." default="grand">

	<typedef resource="net/ggtools/grand/antlib.xml" classpath="grand-1.8.jar" />

	<target name="grand">
		<grand output="grand-build.dot" buildfile="/Users/nyjeanne/sunspotfrcsdk/build.xml" />
	</target>

</project>

Graphviz

  1. File > Open – choose grand-build.dot
  2. As before, I can navigate around the file.  This time the graph is ugly.  But I was doing this because the build file was so large and complex it was hard to understand so I’m glad I visualized it.
  3. File > Export
Not sure why Graphiz is still in beta; it worked perfectly.  Maybe for more complex operations there are problems?

The image
This series of Ant builds has a really large number of targets and dependencies so it makes for a complicated graph. A snippet is at the top of this post. The full one is available online:
pdf (decent number of bytes – still tiny so you’ll want to soom in and scroll around)
gif (the file is a large – 1MB download – which is why I’m not including it in the main blog entry. It’s also tiny, so you’ll want to zoom in and scroll around)

3 plus/3 minus in WPILibj robotics library

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WPILibJ is a library used for FIRST robotics code when programming in Java.  Helping the Stuypulse team gave me the opportunity to look at some of the code.  In honor of ship date this year, I decided to blog some thoughts on the library.  You can see the JavaDoc to follow along.

Good design point #1
The class names have strong ties to the “business.”  Class names like Joystick , DigitalInput and SpeedController are very clear and provide a mapping to a good concept.  They also encourage good object oriented code.

Good design point #2
For the most part the documentation is good and the classes logical.  Many classes have useful comments and tips on usage.

Good design point #3
There are patches released through the competition season.  Care is taken for changes to be backward compatible and not break existing code.  Much appreciated on a six week project.

Surprise #1
In the Image class, care appears to be taken for immutability (classes that cannot be changed.)  It has a package private constructor.  Only getters are provided.  The object can be written to a file, but you need to create a new object if you want to read from a file.  Then comes the surprise.  The image instance field is public!  And that public field is of type Pointer – a wrapper to native memory.   Eek.  Memory leak if you mess with it without being careful?

Surprise #2
The CANJaguar class had the biggest surprise.   When you instantiate an object, you pass the control mode.  Straightforward.  I expect the code to behave differently when different modes are passed.  Then you try to call setVoltageRampRate.  The JavaDoc clearly states what it does:

Set the maximum voltage change rate. When in percent voltage output mode, the rate at which the voltage changes can be limited to reduce current spikes. Set this to 0.0 to disable rate limiting.

Then there is what it does in reality.  If the control mode is kPercentVBus or kVoltage, a formula is used to set the ramp rate.  For the other three modes, the method does nothing.  That’s right nothing.  It doesn’t throw an exception or set it to zero or log an error or anything.  Which means you don’t realize it doesn’t do anything without reading the code.

Surprise #3
I can’t really call this a surprise as I’ve known about it since beta testing.  But I was surprised then.  Last year, there was a Dashboard class for custom output.  It was hard to use and they added a SmartDashboard class this year.  And logically, they added an interface IDashboard for the commonalities between them.  There aren’t many commonalities, but that’s not what I find surprising about the interface.

To use the old Dashboard, you write:


Dashboard d = DriverStation.getInstance().getDashboardPackerLow()
d.addXXX();

To use the new SimpleDashboard, you write:
SmartDashboard.init();
SmartDashboard.logXXX();
That’s right – the new one uses statics. This is where the interface becomes confusing. If we are calling static methods, an interface doesn’t make sense.

The worst bug
The worst bug we encountered wasn’t actually in the WPILib code.  It was in the underlying National Instruments code and affected all three wrapper APIs (Java, C++ and LabView.)  The Encoder class works in an illogical manner. In particular, it only lets you use the first, third, fifth and eighth encoders to get the rate of movement.  (No, that isn’t a typo.  It is a seemingly random collection of orders rather than every other.)  That’s if you are in one mode.  In another mode, the working encoders change.  We have to fool the low level code by creating dummy ones to the “real” encoders get the proper constructor call ordering.  While this was documented on chief delphi (the unofficial FIRST robotics forums), we wasted a lot of time assuming we were doing something wrong.

Conclusion
The longer text for the surprises doesn’t mean that the code is bad.  Just that there is more to write about unexpected things. All in all, I appreciate all the API gives us. Congratulations to team #694 (Stuypulse) on a great build season and for completing an awesome robot on time!

ipad FIRST robotics update

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In early January, I blogged about Getting my iPad ready for FIRST robotics season.  It’s now enough later to revisit that and see how things worked out.

Overall, things have gone better than expected.  For the most part, the internet has been available making searching the internet easy.

Gmail

Now that I’m relying on the iPad more to check my e-mail, I’m hitting the limitations of the built in mail client.  I learned that gmail’s web application is much better.  It lets me both trash and archive, easily view labels, etc

Dropbox/GoodReader

Having the manual on hand in a searchable format has been great!  I was surprised how helpful it was to be able to zoom in on the diagrams – can’t do that with paper.  We also had to remember not to touch when pointing and discussing things.  Wouldn’t want the screen to move.  I downloaded a bunch of other documents to the iPad as well that I might want to reference.

Git Hub Viewer Lite

I’m not sure if Git Hub Viewer Lite or JDocReader is my favorite app.  Git Hub makes it easy and fast to view the code.  Looking at older code while being near the laptop with the new code has been very effective.

JDocReader

My other candidate for favorite application is JDocReader.  Having the robotics documentation on hand without having to changes streams from development has been great.  I don’t need to disrupt the main flow to test a theory.

iUnarchive

iUnarchive is just a utility but it works for what I need it to.

WordPress

There weren’t any lulls yet. We have a bigger group this year and there is another stream of work to jump to if one has a lull. Hence I haven’t used this application beyond trying it out.