Ep. 12: Grounded

Notes from the 10th-16th of April

On gallivanting

Back in October I did many things, one of which was to book flights to Indiana, out of Indiana, and back home again. Why three legs? With the Purdue semester finishing at the start of May and the next Monash semester not starting until the last week of July, I had about three months of holidays lined up. And I was sure as hell not going to be spending that in the dreary Melbourne Winter. So, to Europe it was.

But in October, I had no idea conception of where I might wish to start and finish this trip. So I just made them up. My choices? Start in Rome, finish in Frankfurt¹. Within a few weeks of arriving at Purdue, however, a more alluring start location emerged - Lisbon. Given I was planning on training between cities and taking no internal flights, the start location would have an incredibly oversized effect on the eventual path that I would take. So, since I wanted to visit a few places in Portugal anyway, and since Portugal/Spain form somewhat of a 'dead end' on the map of Europe, why not start there and work my way into the 'heart' of Europe²?

Fast forward to April. I now begin to go through the process of changing the USA-Europe leg. Should be easy, right? Especially since we intentionally booked a flexible fare back in October with the foresight that such a situation might arise.

Issue 1: United Airlines do not have an email/chat help desk; queries can only be made by phone. And my AT&T SIM card³ cannot make or receive phone calls in America. No problem, my roommate let me borrow his phone whenever I needed to make a call.

Great. So I call United, give them my flight details and explain my situation. "No worries", comes the reply, "You will be able to receive a full refund for the Indianapolis-Rome leg and book a new flight". With the green light, I could now start exploring flights into Lisbon.

Issue 2: My friend I was travelling home with booked did not, as discussed, book onto my United flight from Frankfurt, instead finding a cheaper one with Vietnam Airlines⁴. Given I was not that keen on flying back solo if it were avoidable, this meant I now needed to cancel both remaining flights and reschedule. Shouldn't be a problem, according to the lady at United I spoke to.

Issue 3: I called United back a few days later to cancel and receive my refund. Only this time I was informed it was not fully refundable, that it was impossible to say how much I could be refunded without going through the calculus since I had booked all flights as one trip, just with months and months in between flights⁵. This annoyed me greatly. So be it. I got them to cancel my reservation anyway and was directed to a website link through which I could request a refund.

Issue 4: I had to call back a third time to be given my reservation numbers for the flights since upon cancelling the booking I could no longer access them. But finally, I had everything in hand and submitted my refund request. A few days passed. No response, then...

...I ended up receiving a full refund for not only the two remaining flights to and from Europe, but the original flight from Melbourne to Indianapolis too. You know, the one I had already taken way back in January.

I don't know what happened at the United refunds office, but I was thanking my lucky stars. Part of it I suspect lay in the slightly deceitful nature of my refund request message, which essentially stated that on the basis of the first call I had already booked new flights to replace them and then received the news about a partial refund subsequently. All's well that ends well.

Abroad-ening

Don't get me wrong, I was really looking forward to backpacking around Europe. But planning a trip there is really, really difficult for me. First, there are a functionally infinite number of cities/towns you can visit, and asking people for recommendations not only doesn't clarify existing options, but will reveal countless more. Secondly, I have grown very comfortable here at Purdue (see On familiarity). And I kind of don't want to leave.

On the topic of overseas travel. It is well-documented the common perception that many Americans lack awareness and knowledge of other countries that others may take for granted, however maybe, just maybe, in some instances this is understandable. I have met many a people here who are from Indiana that fall into one of the following categories:

1. They have never left the state of Indiana before.
2. They have never left the United States before.
3. They have never been on a plane.
4. They have never been overseas. Particularly for members of 1., a lack of geographical basics should perhaps not surprise as much as it does. Remember, Indiana is not just any state. One wouldn't have to leave a place like New York or California to sample a proportionate slice of the global pie. Not so here. For many, I am the first person from the Southern hemisphere they've ever met.

The solution to perceived American insularity does not admit of an easy solution, but surely offering more accessible exchange programs like mine to college students would not hurt. Someone down the hall to me who belonged to both 1. and 4. above was busily packing for her first trip abroad: a 3-week tour of Egypt. What a first foreign country to visit!

Whether weather

As I flagged last week, the weather has taken a marked turn towards Spring. Long gone are the biting winds sweeping across campus as we trudged to classes in the morning. In their place, one finds now basking sunshine warmth. Depending on the time of day, Purdue used to feel utterly abandoned and desolate. Now, even the rabbits are beginning to emerge and litter the campus streets. It is truly marvellous.

Back home in Melbourne, Spring is normally my favourite time of year. If anything, I have found the olfactory experience in this period to be so vividly attached to a great deal of important and cherished memories of mine. Interestingly enough, in an entirely different country removed of the familiar flora, the content of memories evoked shifted markedly. In fact, most often I noticed my mind wandering back to the July week I had spent in Maryland way back in 2017 on a school trip. Then, too, I found myself on a college campus⁶, surrounded by a number of new, international friends. There is a great deal of literature on such evocative effects of scents on nostalgia. What I find counter-intuitive about this, despite my direct experiences of it, is that in any given moment, scent is perhaps the sense we pay least attention to. Intriguing, to say the least.

With the sun coming out more and more, there is a new favourite spot for me to pass my afternoons.

There is a lovely, tree-lined walkway that runs from the fountain in the Engineering Mall to the steps of the Electrical Engineering building. Under the mottled cover of the leaves, leaning back against one of the pillars is a delightfully comfortable way to spend the afternoon. Even in the last week, I have spent many an hour here reading a book, whiling away the time. And I wouldn't have it any other way.

On familiarity

I have now been at Purdue for some 13 weeks. Wow. What has become increasingly apparent to me is that I am no longer the lost soul I was when I first arrived. Whereas each building once looked the same, each passing face blending into every other, through daily exposure the place has become...familiar. And it is a process that when you step back and examine it is rather puzzling.

Nothing at the objective level has changed. The bricks of concrete of the centres I had once been lost in, the paving of streets whose names I could never remember, they have remained the same. All changes, then, have taken place at the subjective level.

A fact whose significance we perhaps do not appreciate enough is that we do not "see" the outside world. Rather, we 'see', and therefore interact with, the version of the outside world as captured by our eyes. If you don't believe me, consider the fact that, staring at whatever is currently in your field of view, you can think of any particular object, say a red ball, and it will appear as if said ball becomes layered on top of whatever you were looking at.

Familiarity should be another example of this phenomenon. Notice that when you look at an object, you don't really see the object. What you see is a function, a symbolic representation of the object. I look at my keyboard and I see something I can type with. I look outside my room and see a doorway to walk through. In the same way, when I look at buildings around Purdue, they are no longer foreign precisely because they have assimilated symbolism in my mental map of the world. From my memories, they have taken on their own respective purposes.

So, with all that in mind, take a look at the following picture and tell me what it is you really see. I suspect our answers may differ wildly.

On Cadence

Lastly, a technical aside. I am currently taking a class on integrated circuit analysis and design, and since there is no final exam the majority of the mark consists of two large projects - one of which I have just completed, the other I am just starting.

The relevant preliminaries for this section are not extensive. In essence, the brains of a computer, known as a Central Processing Unit (CPU) contains the basic building blocks like adders that make everything else go. To this point in my studies, we generally treat these adders as black-boxes, only interested in the fact that if you provide it with two numbers $x$ and $y$, the adder will return $x+y$. However, chip designers have a lot of technicalities to consider when designing such a block. At the level of 1's and 0's, there are many, many optimisations that can be made for addition. And moreover, one cannot just give importance to the logical architecture of the gate, but also the physical, too. The length of a given wire, the number of wires running parallel to a wire, these are all considerations that we gloss over in theory but in reality can entirely ruin the performance of the adder.

In this class' projects, therefore, we are tasked with designing basic blocks like an adder or multiplier that can run as fast as possible⁷. The catch is we are designing these at the level of transistors, the atoms of a computer chip. Clearly it is infeasible to do such modelling practically, so instead we use software like Cadence. Initially, I didn't like the program at all, but I have to say in recent days it has really been growing on me. It is super, super powerful.

I can make a basic NAND gate using complimentary CMOS logic with a 45nm technology as such:

Which, with some other basic logic gates can be treated as "blocks" in a 1-bit adder:

Which become the blocks of a full 3-bit adder with carry-in:

And finally, stacking a bunch of full-adders together yields a 4x12 multiplier, that is, it can compute the result of a 4-bit number multiplied by a 12-bit number.

This is all super easy with Cadence because it allows you to define these low-level components/modules like NAND gates and then cascade the gates up to the level of operators like multipliers and adders. Even better, we can test key metrics like high-low or low-high propagation delay, average power consumption and verify correctness of the operators through test harnesses:

If you are still reading, and still care, you can read the two reports I wrote on designing full adders and carry-save multipliers.

Footnotes