How to Berkeley: Linear System Theory Prelim

Having just spent the last 3.5 weeks doing not much other than prepare for prelims, I thought I would summarize my experience and give some insights.

Introduction
For starters, prelims are short for preliminary examination, an oral exam that is one of many requirements in your PhD journey at Berkeley (in EECS). The pass rate for this exam is on the order of 70-85%, though you are allowed to take it twice (or thrice, with a petition), and the overall pass rate is about 95%. [Disclaimer: these numbers are 2nd hand. They are approximate.] The exam takes place over 1 hour, with 3 professors. Each professor gives you 20 minutes (though it has been 16 minutes the last couple years) to solve some problems on the board. The topic of my prelim exam was linear system theory, meaning linear algebra and linear control theory. The highest order bit for success on this exam is taking EE221A (or already knowing the material).

Why take the prelim? What is it useful for?
Here are some perspectives I found interesting from some of the older (and wiser) students.
– “You’ll never feel as smart as you did when you took your prelim. That is the culmination of your expertise.” – Roy Dong
– “There is almost no correlation between how much of the question you get through and whether or not you pass. The thing to keep in mind for how they determine your score is ‘would you benefit from taking the prelim again?'”
In some sense, the prelim is as much testing your mastery of the content as it is testing how much you can think on the spot (and take hints/guidance from the committee), explain concepts, and present on the board.

Focused learning
Never in my life have I been so free for so long to focus on one thing. There have always been extra curriculars, homework, classes, social obligations, miscellaneous other responsibilities that chip away at life, hour by hour. 4 weeks ago, I wondered: “how long can you focus?” And it is amazing how much you can do and learn when you put your heart/mind into something. So, what can I accomplish if I put the same amount of focus into something else? I don’t know that a pure focus approach is suitable always, but it really is a key part of grad school and doing research.

Being healthy
This is actually just a continuation of things I’m learning after college. 🙂 Oddly, there was never much incentive in my life to be healthy. Over the last month, I was healthier than I ever was. I took the time to eat enough, sleep enough, relax enough, and even exercise! I told most people ‘sorry, I’m MIA this month, poke me in September?’ There was nothing but prelims and me time (okay, and also a journal paper deadline 3 days after the prelim). Pushing everything else aside, reminded that I can be free (aside from prelims).

Now, without prelims, can I still be free?

How do you prepare for the prelim?
I stumbled around a bit at the beginning, not knowing quite where to start, how to split my time between the paper and studying, and being irked by the typeset of the Callier and Desoer book. Eventually (by the last week), I fell into a nice routine of:

1. Do old prelim problems.
2. Note down confusions. Note down topics to learn/review.
3. Discuss confusions with study group.
5. Repeat.

I recommend getting into that routine sooner. I also spent the last 2 days before the exam going through the lecture notes from EE221A, to pick up anything I might have missed in ad hoc studying, which I also recommend. Preparation will vary from person to person, but the general advice for preparation seems to be:

• Get a good study group and study with them. Early and often.
• Ask older students for help, e.g. through mock exams.
• Relax the day before the exam. (And have great friends who convince you to do so. 🙂 )

The actual prelim
You study for a few weeks, discussing question after question, reviewing topic after topic. It all seems to be building up to something grand. You calm yourself the couple hours before the exam with some hot tea and a good book, unsure how you’ll perform when it matters. But then you go in to the examination room, a professor hands you a question and tells you you have 16 minutes, and you get started just like that. You cite theorems, sketch some proofs, and describe your intuition. You remain brief because there’s a lot to get through. You work out small examples when you are unsure of the full approach. Along the way, the professors attempt to hint you along. And you chug chug chug along. 48 minutes later, you thank the committee and leave the room. That’s it. The prelim exam itself is fully expected, almost routine. The bulk of the gains (learning, making friends, etc.) happen beforehand. So, don’t have too high expectations for the prelim exam itself. 🙂

– Modern Control System Engineering, in particular Chapters 3,5,10 [link] — great for perspective on modern vs classical control, control tools
– Linear Algebra Done Right — self-explanatory

Special thanks to Eric Kim for feedback on this post. Also thanks to all the friends who helped us prepare!

Update: average rating of the overall prelim experience this year is 7.8/10. Caution: statistics is dangerous, sample may be biased.

How to Berkeley: Establishing Residency

Actually, step 0 is to negotiate with your advisor to split the difference in the  that the department/someone saves by establishing residency. It could be a pretty great side-income. ..Just kidding.

The guidance / explanation they sent us is okay, but I just want to know exactly what steps are needed to get it done. Here I’ve included their guidance + annotated with my process. I also recorded the amount of time it took me to figure each step out, which should be an upper bound on the time it takes someone following these steps.

1) Submit your Statement of Legal Residence in BearFacts available NOW.

[15 minutes] It’s abbreviated as “SLR” in BearFacts. Go here and fill out the forms.

2) Please upload the following documents at: or.berkeley.edu/myresidency. PLEASE REDACT ANY SENSITIVE INFORMATION (account numbers, SSN, etc.) FOR SECURITY REASONS.

This means you have to collect a bunch of information. If you’re like me and waited until July to do this, then most of it should be done already by accident. Except for the driver’s license.

WARNING: they seem to do some sort of greedy evaluation, i.e. they evaluated my residency before I even finished submitting all my documents. To avoid this (and the subsequent petition process..), I recommend submitting all your documents at once.

– California driver’s license or state ID

[15 minutes on website, 90 minutes reviewing rules, 30 minutes transit, 60 minutes to get new license] If you have an existing driver’s license, you need to take the written driving test at the DMV to exchange it for a CA driver’s license. The website’s not the easiest to navigate, so I included some useful links here. Instructions are here.
1) Go to the CA DMV website to schedule an appointment. You want to select the “Office visit” option. To build in redundancy (since it’s nearing the deadline), I scheduled 3 appointments on 3 consecutive day. Just in case.
2) Materials for the written test are here. The test is ~30-40 questions and you are allowed 6 incorrect.
3) Stuff to bring to the DMV
– $33 Fees documented here. Bring cash because sometimes the DMV loses credit card information to hackers. – Application form DL 44 (you fill this one out there) – Social security card (you don’t actually need this, but you do need to know your SSN) – Passport or birth certificate – California voter’s registration [10 minutes] Check your registration for Alameda here. There you can enter your address and get a pdf of your voter status. For other counties, go here. – California motor vehicle registration (if you own a vehicle) [0 minutes] – 2013 federal and state taxes and W2s (for the 2013 filing year, we recommend that you file California part-year returns if you were not in the state for the entire year) [25 minutes] Depending on how careful you want to be, you can probably skip some of these steps. Instructions are geared for OSX. 1) Redact sensitive info: Open up your tax returns and search for your social security number. Use your favorite PDF tool (e.g. Preview, Adobe Acrobat) to draw black boxes over those fields. Also search for your bank account numbers. 2) Convert to jpg: Download imagemagick (available at least for Ubuntu and OSX). Go to the directory and run: convert -density 400 -scale 2000x1545 {FILENAME}.pdf {FILENAME}.jpg 3) Convert back to pdf: convert {FILENAME}*.jpg {FILENAME}-jpg.pdf – Evidence of your arrival date in CA prior to August 28, 2013 (plane ticket and/or credit card statement) [7 minutes] I uploaded my boarding pass for my one-way flight out from Boston to SFO. Sniffle. – Evidence of your Summer 2014 whereabouts (this can be a memo from your department indicating your summer research plans; a letter from your employer indicating your employment status, etc.). Please note that depending on your circumstances we may pend your file for evidence of your summer whereabouts. [5 minutes] I uploaded the NSF “Certification of Appropriate Fellowship Activities” form, which certifies NSF to pay me for the summer because I’m doing research. – For students born in 1991 or later and you were claimed by your parents on their taxes: documentation that you are employed 49% or more time or equivalent in university-administered funds (e.g. grants, fellowships, stipends, etc.). [0 minutes] 3) Please note that after receiving ALL of the documents requested, it will take three to four weeks to make a final evaluation and residency determination. If you do not submit all of your documents by the documentation deadline of August 15, 2014, you will be considered a non-resident for the purposes of tuition and fees for Fall 2014. Annnnd recording the process took about 45 minutes, for a grand total of 5 hours.. sigh. How to Berkeley, v2 The first 10 seconds is how I feel. Berkeley should hire a couple software engineers to fix their online interfaces (e.g. for class registration). People have obviously noticed the problem and now there are layers and layers of web pages / services maintained by different organizations / departments that each contain different amounts of information. It’s all very confusing, disorganized, and arduous, and I miss MIT WebSIS. Here is a guide with some simplified steps for paying fees at Berkeley and class registration for EECS graduate classes: Shortcut for paying bills/fees: 1. Login to e-bill/e-check. Scroll to the bottom and click “I agree.” 2. Click “Pay now” and follow instructions from there. Methodology for class registration: 1. Browse for possible classes of interest: Look through the relevant listings [CS, EE, CS-next, EE-next]. This just gives you the names of the courses offered this/next semester. To get the description of the classes, you’ll need to follow the links to the general catalog, but even then, they are probably out of date because the process for faculty to update it is arduous. Good luck finding any descriptions for the special seminars (e.g. CS 294). You might have to be on some mailing list at the right time to get these, so try searching your inbox… 2. Create a schedule of your classes: Go to ScheduleBuilder and start adding your classes of interest. In the first field, type the department (“EE” or “CS”) and in the next field type the number of the course. When you’re done, click “Generate Schedules.” Select “Save as Main Schedule.” Next, view your Saved Schedules. Optionally export the calendar by selecting “Download iCal.” (From there, you can import this into gCalendar, iCal, etc.) Take note of the CCN numbers displayed to the right side of the interface. You’ll need these for the actual registration step. 3. An alternative to the previous step is to build the schedule in your head and get the CCN numbers straight from [EE Fall, CS Fall, Stat Fall] [EE Spring, CS Spring, Stat Spring]. Apparently, some of the classes have a direct link to register a class from this interface, but it seems inconsistent. 4. Finally, login to TeleBEARS to actually register your classes. Be sure to do this outside of its schedule maintenance hours of 6-7am M-F, 6-noon Su, and some Saturdays. I don’t know what this means, but if your appointment has expired, forget about accessing TeleBEARS at normal hours. Here are the available “Open Hours”: 7-8am, 7pm-12am M-F, and 12pm-12am Sa-Su. WTF. Also FYI, you can’t register for more than 1 seminar (i.e. CS 294) because the registrar thinks they are all the same class. Okay, anyway. First, click on the top tab for the semester that you’re registering for. To the left, click “Add class,” and enter in the CCN from the previous step. Repeat for all your classes. Links: Bear Facts [link]: student homepage (i.e. websis) TeleBEARS [link]: pre-registration, current class list, registration change, there is a tab for each semester General class catalog [EECS, EE, CS]: usually out of date and doesn’t contain information about special seminars Class listings [EE Fall, CS Fall] [EE Spring, CS Spring]: contains CCN and enrollment status for graduate classes Class schedule [CS, EE, CS-next, EE-next]: includes class time, lists special classes (CS 298 = Seminars, CS 294 = Courses, not sure where the descriptions are though) Class schedule [link, ScheduleBuilder]: printable class schedules, clunky searchable interface for classes EECS Grad Info [link] EECS Grad Handbook [link] Transfer Credit Petition [link] Add/Drop Form [link] Please feel free to comment with suggestions on what else to include in this reference. Optimizing for happiness [latexpage] Let$f(x)$be a convex mood function, with happiness at its minimum. With all the swings of moods,$f(x)$is not necessarily differentiable, and although it may be steep at parts, we assume it is continuous. Then, we wish to solve the minimization problem $\min_x f(x)$ We propose to use a subgradient method. The intuition is that you may pick a direction for your mood to change. Any subgradient at your current point$x$will point upwards of the curve (less happy), so we take a step towards the opposite direction. There are a variety of ways to select a time step, e.g. exact line search, backtracking. Without loss of generality and for simplicity, we use a constant step size. Bottom line: If you just smile a little more, you’ll end up happier. Subgradient method for convergence on happiness given a starting point$x \in \text{dom } f$given an error parameter$\epsilon \ll 1\text{stop} = \text{false}$while$! \text{ stop}$do $\Delta x \leftarrow -\partial f(x)$% Select a subgradient$t \leftarrow \epsilon$% Line search if$x + t\Delta < x$and$\abs{t \Delta x} \leq \epsilon$then$\text{stop} = \text{true}x \leftarrow \min(x, x + t\Delta x)\$ % Update 

end while 

(Thanks, Pranjal, for the inspiration.)

Curiosity

2 months into the PhD now, and we are very much still exploring this grand academic environment at Berkeley. Here are a few of the questions that many of us are asking ourselves and one another. And even though we fully realize that our answers will develop, warp, and combust over the course of the next half decade, we at least have some established prior from which we can begin our journey. The discussions have been extremely insightful and provocative, and I look forward to many more.

• How did you get here? Why are you here, at Berkeley? Perhaps differently, why do you think they admitted you?
• How do you value money? What is your cost for agreeing to not pursue a PhD? 20 million vs 500 billion?

• What would you consider to be the biggest problem for society?
• Do you consider your role in society? What do you consider it to be? Do you feel an obligation to serve society in the way that you are best suited? How does happiness factor in?
• Do you think your time is best spent via a career in academia? Via research? In industry? As a parent?
• Do you want to become a professor?

And about the present, quite literally

• How many projects are you working on now? Which of them with professors?
• How many group meetings of different professors are you attending?
• What’s your plan for this semester? For the first year?

How to Berkeley

Berkeley’s online interfaces (e.g. for class registration) are very confusing as compared to what I’m used to at MIT. In case I’m not the only crazy person, here is a reference:

Bear Facts [link]: student homepage (i.e. websis)
TeleBEARS [link]: pre-registration, current class list, registration change
Class listings [EECS, EE, CS]