Wednesday, May 13, 2015

Course Design Series (Post 1 of N): Why Study Programming Languages

Obviously, there are some practitioners and researchers who base their living on programming language design.  But what of the rest of us?  The Communications of the ACM ran a short article on why: Teach foundational language principles.  Language design is increasingly focused on programmer productivity and correctness.  As programmers, are we aware of the new features and programming paradigms?

Particularly, let's look at three aspects of programming languages: contracts, functional languages, and type systems.  By introducing each to budding programmers, we improve their habits, just as presently I include comments and other style components in project grades.  First, contracts provide a well defined mechanism for specifying the requirements of each component in a system.  Not just commenting each component and interface, but doing so in a manner that permits the compiler / runtime system to verify and enforce it.

Functional languages are well known, and whether or not you may ever use one, they teach valuable techniques and mental models regarding programming.  A programmer should use pure and side-effect free procedures, rather than interleaving logic across different components.  Other practices, such as unit testing, also trend toward clean interfaces; however, being forced to obey these rules via the underlying language is great practice.

Type systems are treated by the authors as a panacea, as they call for language designers to be "educated in the formal foundations of safe programming languages - type systems."  Panacea or not, reasoning about functionality within the bounds of types leads to code that is clearer and more maintainable.  Even in a weak language, such as C, one can use enums rather than everything being "int".

As these aspects are being increasingly used in various forms in current language design, programmers need to be knowledgeable of them in order to be effective and use the languages to their full potential.  It is therefore incumbent on me, and other educators, to appropriately include these aspects when we teach about programming languages.

Which leads me back to writing a course description and learning objectives for my fall course.  Maybe later this month once I figure out why one of the textbooks still hasn't arrived.

Friday, April 17, 2015

Repost: Code Quality

xkcd had a great comic today about the code quality of self-taught programmers.  While there are technically trained programmers that write poor quality code, my impression is that this is more common with self-taught programmers as well as programmers who are only taught programming itself.  Basically as part of the technical training, someone learns more than just programming.  They learn about CS theory, data structures, multiple programming languages, and are more often exposed to well written / designed programs.  Learning to program at a high quality is similar to learning a natural language, in that you study grammar and spelling, you read great works of literature and analyze them, and you practice reading / writing / speaking.

Each month I understand better what it takes to be competent in my field and also respect more the idea that curriculum is established by experts for a purpose, whether or not I may like certain topics.

Monday, April 13, 2015

Book Review: Structured Parallel Programming

At SIGCSE this year, I spoke with several publishers about possible textbooks.  Primarily, for ones that would work in the different classes that I might teach.  As well as those that relate to my present research.  In this case, I received a copy of Structured Parallel Programming: Patterns for Efficient Computation from the publisher to review and consider for possible future use in a course.

This work is in three parts: the basics of parallelism and performance, the common patterns in which parallelism is expressed, and example implementations of several algorithms.  The second part is the core of the work.  To show maps, reduce, scatter and gather, stencil, fork-join, and pipeline.  But before we learned those details, we would come to key quotes for all that I do:
You cannot neglect the performance of serial code, hoping to make up the difference with parallelism.
[The] performance of scalar processing is important; if it is slow it can end up dominating performance.
Therefore, parallelism is a method for improving the performance of already efficient code.

With both the common patterns, as well as the example implementations, the authors generally provide the source code for each pattern and implementation using Cilk, TBB, and OpenMP.  This source is not for casual readers.  More involved implementations can stretch for several pages, as the initial implementation and then subsequent refinements are explored.  While it serves well as a reference, it may have worked better to focus on one parallelism approach for each section and therefore give further explanation to the code, especially the language features used.  And thereby retain the pattern itself rather than becoming a practitioners' reference.

The example implementations (the third part) are perhaps the least interesting for the classroom and potentially the most interesting for practitioners.  Clearly, if I was trying to write code similar to one of these problems, I would have an excellent reference and starting point.  However, that is quite rarely the case for myself and I suspect most people as well.

If I was teach a parallel programming course, I might consider using this work (although I still have other, similar textbooks to review); however, were I to do so I would be confining my teaching to the first two parts and may even to just 1 parallel programming paradigm.  Yes, I will admit that the last parallel programming course I took covered a diversity of paradigms (Cilk, vectorization, GPUs, OpenMP, MPI), yet I would have preferred to focus more on what one or two paradigms are capable of rather than just the taste of many.  Parallel programming takes a lot of work to learn and this book is one piece in that effort.

Thursday, April 2, 2015

Course Design Series (Post 0 of N): A New Course

This fall I will again be Instructor of Record.  My appointment is to teach CS 4392 - Programming Languages.  This is an unusual situation in that the course has not been taught for over 5 years (last time was Fall 2009).  Effectively, the course will have to be designed afresh.

The first step in course design (following L. Dee Fink and McKeachie's Teaching Tips: Chapter 2) is to write the learning objectives using the course description, along with prerequisites and courses that require this one.  Let's review what we have:

Course Description: none

Undergraduate Semester level CS 2340 (which has the following description)
Object-oriented programming methods for dealing with large programs. Focus on quality processes, effective debugging techniques, and testing to assure a quality product.

Courses depending on this: none

Alright.  Now I will turn to the CS curriculum at Georgia Tech.  Georgia Tech uses a concept they call "threads", which are sets of related courses.  CS 4392 is specifically in the Systems and Architecture thread.  This provides several related courses:

CS 4240 - Compilers, Interpreters, and Program Analyzers
Study of techniques for the design and implementation of compilers, interpreters, and program analyzers, with consideration of the particular characteristics of widely used programming languages.

CS 6241 - Compiler Design
Design and implementation of modern compilers, focusing upon optimization and code generation.

CS 6390 -  Programming Languages
Design, structure, and goals of programming languages. Object-oriented, logic, functional, and traditional languages. Semantic models. Parallel programming languages.

Finally, the ACM has provided guidelines for the CS curriculum.  Not only does this provide possible options for what material I should include, but they have also provided several ACM exemplar courses (c.f., and

To summarize, if my first step is to write the learning objectives, then I am on step 0: write the course description.  In a couple of weeks, I plan on finishing my initial review of potential textbooks as well as the other materials covered above.  That will provide me the groundwork for the description and then objectives.

Friday, March 27, 2015

PhD Seminar - teaching, writing and oral presentation skills

Every month, here are Georgia Tech we are getting together to cover some of the things that PhD students should know / learn during their studies.  This month we gathered to cover various communication skills.  I have copied the points from today's seminar:

Teaching Advice
  • Strive for engagement
  • Trust your expertise
  • Conference Talk != Teaching
  • Get Students to Talk
Writing Advice
  • Write for a general audience occasionally
  • Read to find models of writing
  • Book Recs: Oxford Guide to Plain English / Bugs in Writing
  • It is a process
  • Find out what motivates you to write
  • Inside-Out style
  • Pay attention to copyediting and learn
Presentation Advice
  • Motivate them to want to read the paper
  • The audience doesn't know what you don't tell them
  • Toastmasters (or Techmasters at GT)
  • Slides as a reminder
  • Eye contact
  • Repeat the question (everyone has heard it and you know what is being asked)

Tuesday, March 10, 2015

Book Review: Geek Sublime: The Beauty of Code, the Code of Beauty

A book of such promise is Geek Sublime: The Beauty of Code, the Code of Beauty, yet it fails.  The first third of this work followed the hopeful theme, intertwining the story of programming, its style, and the author's complex relationship with his Indian heritage, desire to be an artist (writer, etc), and his ability to make money programming.  An interesting twining that continued to encourage me to read, yet some worrisome signs developed.

The first worry was skipping a long section on how computers work.  This *is* my field of Computer Science, so I wasn't interested in reading the basics.  Yet worse was noticing some inaccuracies.  They established a certain level of understanding in Computer Science that was concerning, particularly in light of the author's non-technical background.  Livable, er readable, sure.

It was then the author's intent to show the great intellectual contributions made by Indians.  I have no dispute of this point, except that it wasn't actually fitting with the established theme of the work.  Finding that Sanskrit has a codified language of great antiquity enabled the author in this quest.  Alas, it was long pages that grew increasingly divorced with the first part of the title, "The Beauty of Code" and further focus on the later, "The Code of Beauty".  And this code deriving from Indian literary traditions.

In the end, the book concluded.  A crescendo of final claims that each read like next page would be the last, until such time as there was really no text left.  I learned something about Indian culture by reading this book, except that was not why I read it.  I did not gain in what I sought, so I cannot recommend reading it, nor care to provide a link to it.

Saturday, March 7, 2015

Conference Attendance SIGCSE 2015 - Day 2 / 3

I recognize that Day 1 afternoon went “missing”.  I presented my poster and that consumed the sum total of my time.  While I am happy with all that I achieved with my poster (writing IRB protocol, independent work, analyzing my teaching, et cetera), it was not considered as a finalist for the student research competition (SRC). Yet I received significant feedback and a number of follow-ons that I will have to try to evaluate the next time(s) I teach.  I have been doing an excellent job of networking and speaking with my colleagues.  And I have seen several exciting techniques to improve my teaching.

This was a small Bird of the Feather (BoF), but we discussed some approaches and things to know before attending your first conference, and not just for undergraduates.  However, in some cases, undergraduates are attending their local institution and may never have traveled any significant distance.  What do they really need to bring?

In traveling, take some time to prepare students.  Let them know what to expect.  For example, it is okay to miss some paper sessions, and even return to your room entirely.  It is okay to ask questions 1:1.  Find groups where people are being introduced and join in.  Student volunteering, while takes time, also gives an additional individuals that you will know.  Use the people you know to introduce you to others at the conference.

This is just what it sounds.  A Ruby based framework that enables writing simple unit tests that will then be applied to a full simulation of the assembly executed.

The presenter(s) were not at this poster, but it showed a high quality interface for seeing the scheduling of threads according to different scheduling policies.  The intent here was not to explore races and parallelism, but rather see how scheduling decisions are made in an OS.

I was not expecting this poster.  You are walking along and then see 4 Raspberry Pi's all networked together.  Raspberry Pis and HPC?!  A small setup, but it is an interesting development that takes advantage of the low cost Pi and still provide an HPC platform for students.

Plastic parts all worked together to form replicas of Pascal's mechanical calculator.  Interesting and student assembled.

Teams of 4 students, approach is evaluated on courses from three years of major (sophomore on up).  Teams are formed with CATME (particularly using dissimilar GPAs in a group), as well as partner selection (when possible).  Students provide peer evaluations after each stage of the project.  Significant data collection looking particularly at what students prefer for to be the evaluation policy (between 100% of grade for the group’s work to 100% of the grade for the individual’s contribution).  This question was taken repeatedly throughout the semester, which leads to whether student preferences change?  More senior students prefer more weight being attributed to group.  The predictor for what grade split is at what point in the course is this surveyed, and effectively as soon as the teams are formed the students prefer to be graded primarily as a group.  Follow on study is looking at experience with team projects, trust in the ability to evaluate individual contribution, and other questions.  This is a hopeful data point.

How do faculty become aware and why do they try out teaching practices?  66 participants in CS, including chairs, tenure-track faculty, teaching faculty, and Ph.D. student instructors across 36 institutions.  First, the mental model of what an instructor does can differ significantly from what the instructor is actually doing.  Second, faculty can find out about practices through a variety of approaches, such as self-identifying that there is possible improvement in their teaching.  Faculty often trust other faculty like them (researchers to researches, lecturers to lecturers).  Third, when adopting a practice, faculty need to evaluate the effectiveness (see also my poster, student feedback, etc).  -- My efforts in this have been having different faculty (my recommendation letter writers) view my lectures / teaching, and thereby giving them demonstrations of different practices.
"We lost the war on cheating"  Instead, we have to meet with students such that they are demonstrating their understanding of the code.  The requirements of submissions: attribute your sources and understand your submission.  Enables students to work together, use all sources, develop interview skills.  Enables reuse of assignments.  Grading is now 40% correctness / 60% code interview.  Rubric for each interview.  Students should arrive early and have their laptop ready to present / explain.  Students were better able to learn and complete the assignments, as well as feedback for improvement.  Students also felt better able to learn the material by being able to collaborate and not constrained by a collaboration policy.  There are some stressors, such as TAs having to meet with hundreds of students, as well as their inconsistencies.  -- This was perhaps the most exciting new technique that I saw / heard about.