How, why, and when to flatten your conditionals

You may be tempted to write code that looks a little like this:

for item in items:
     if not condition_1(item):
         if not condition_2(item, False):
             if not condition_3(item, 3, 3):
                 if not condition_4(item):
                     do_work(item)

But please, don’t. Flatten your conditionals instead.

How to flatten your conditionals

There is a relatively straightforward alternative to the above. Instead, we use continue expressions to short-circuit the cascade. This looks a little bit like this:

for item in items:
     if not condition_1(item): continue
     if not condition_2(item, False): continue
     if not condition_3(item, 3, 3): continue
     if not condition_4(item): continue
     do_work(item)

That’s pretty much all there’s to it.

Perhaps you’re not inside of a loop, but rather inside of a “nullable” function or method (i.e., one which may reasonably return None);  that’s okay, replace continue with return. Perhaps there’s more than one item you’re possibly shipping off to do_work on; that’s okay, wrap the conditionals in a function and use return to short-circuit evaluation. Perhaps you want to terminal the entire loop, not just this iteration thereof; that’s okay, replace continue with break.

Why to flatten your conditionals

The flattened loop is much easier to read. There is no indentation (or bracketing) to track. The fact that each of the conditional expressions is at the same indentation (bracketing) level makes it clear that we’re just dealing with a cascade of conditionals, all of which are handled the same. Realistically, one can only visually parse 3-4 levels of indentation; the Linux kernel, for example, uses an 8-character indent and forbids more than 3 levels of indentation. Flattening your conditionals means you don’t have to deal with that very often.

When to flatten your conditionals

It’s perhaps preferable to write your early code with nested conditional statements. It may turn out that you need to do some work in one of the medial else: clauses (which we’ve elided here), which can make flattening the conditionals hard. But once you’re writing comments about the conditionals in the cascade, and preparing to share your code with others, it’s time to do away with more than a few layers of indentation.

What to do about the academic brain drain

The academy-to-industry brain drain is very real. What can we do about it?

Before I begin, let me confess my biases. I work in the research division of a large tech company (and I do not represent their views). Before that, I worked on grant-funded research in the academy. I work on speech and language technologies, and I’ll largely confine my comments to that area.

[Content warnings: organized labor, name-calling.]

Salary

Fact of the matter is, industry salaries are determined by a relatively-efficient labor market. Academy salaries are compressed, with a relatively firm ceiling for all but a handful of “rock star” faculty. The vast majority of technical faculty are paid substantially less than they’d make if they just took the very next industry offer that came around. It’s even worse for research professors who depend on grant-based “salary support” in a time of unprecedented “austerity”—they can find themselves functionally unemployed any time a pack of incurious morons seem to end up in the White House (as seems to happen every eight years or so).

The solution here is political. Fund the damn NIH and NSF. Double—no, triple—their funding. Pay for it by taxing corporations and the rich, or, better yet, divert some money from the Giant Death Machines fund. Make grant support contractual, so PIs with a five-year grant are guaranteed five years of salary support and a chance to realize their vision. Insist on transparency and consistency in “indirect costs” (i.e., overhead) for grants to drain the bureaucratic swamp (more on that below). Resist the casualization of labor at universities, and do so at every level. Unionize every employee at every American university. Aggressively lobby Democrat presidential candidates to agree to appoint the National Labor Relations Board who will continue to recognize graduate students’ right to unionize.

Administration & bureaucracy

Industry has bureaucratic hurdles, of course, but they’re in no way comparable to the profound dysfunction taken for granted in the academic bureaucracy. If you or anyone you love has ever written a scientific grant, you know what I mean; if not, find a colleague who has and politely ask them to tell you their story. At the same time American universities are cutting their labor costs through casualization, they are massively increasing their administrative costs. You will not be surprised to find that this does not produce better scientific outcomes, or make it easier to submit a grant. This is a case of what Noam Chomsky has described as the “neoliberal confidence trick”. It goes a little something like this:

  1. Appoint/anoint all-powerful administrators/bureaucrats, selecting for maximal incompetence.
  2. Permit them to fail.
  3. Either GOTO #1, or use this to justify cutting investment in whatever was being administered in the first place.

I do not see any way out of this situation except class consciousness and labor organizing. Academic researchers must start seeing the administration as potentially hostile to their interests, and refuse to identify with, or (or quelle horreur, to join) the managerial classes.

Computing power & data

The big companies have more computers than universities. But in my area, speech and language technology, nearly everything worth doing can still be done with a commodity cluster (like you’d find in the average American CS departments) or a powerful desktop with a big GPU. And of those, the majority can still be done on a cheap laptop. (Unless, of course, you’re one of those deep learning eliminationist true believers, in which case, reconsider.) Quite a bit of great speech & language research—in particular, work on machine translation—has come from collaborations between the Giant Death Machines funding agencies (like DARPA) and academics, with the former usually footing the bill for computing and data (usually bought from the Linguistic Data Consortium (LDC), itself essentially a collaboration between the military-industrial complex and the Ivy League). In speech recognition, there are hundreds of hours of transcribed speech in the public domain, and hundreds more can be obtained with a LDC contract paid for by your funders. In natural language processing, it is by now almost gauche for published research to make use of proprietary data, possibly excepting the venerable Penn Treebank.

I feel the data-and-computing issue is largely a myth. I do not know where it got started, though maybe it’s this bizarre press-release-masquerading-as-an-article (and note that’s actually about leaving one megacorp for another).

Talent & culture

Movements between academy & industry have historically been cyclic. World War II and the military-industrial-consumer boom that followed siphoned off a lot of academic talent. In speech & language technologies, the Bell breakup and the resulting fragmentation of Bell Labs pushed talent back to the academy in the 1980s and 1990s; the balance began to shift back to Silicon Valley about a decade ago.

There’s something to be said for “game knows game”—i.e., the talented want to work with the talented. And there’s a more general factor—large industrial organizations engage in careful “cultural design” to keep talent happy in ways that go beyond compensation and fringe benefits. (For instance, see Fergus Henderson’s description of engineering practices at Google.) But I think it’s important to understand this as a symptom of the problem, a lagging indicator, and as part of an unpredictable cycle, not as something to optimize for.

Closing thoughts

I’m a firm believer in “you do you”. But I do have one bit of specific advice for scientists in academia: don’t pay so much damn attention to Silicon Valley. Now, if you’re training students—and you’re doing it with the full knowledge that few of them will ever be able to work in the academy, as you should—you should educate yourself and your students to prepare for this reality. Set up a little industrial advisory board, coordinate interview training, talk with hiring managers, adopt industrial engineering practices. But, do not let Silicon Valley dictate your research program. Do not let Silicon Valley tell you how many GPUs you need, or that you need GPUs at all. Do not believe the hype. Remember always that what works for a few-dozen crypto-feudo-fascisto-libertario-utopio-futurist billionaires from California may not work for you. Please, let the academy once again be a refuge from neoliberalism, capitalism, imperialism, and war. America has never needed you more than we do right now.

If you enjoyed this, you might enjoy my paper, with Richard Sproat, on an important NLP task that neural nets are really bad at.

Disfluency in children with ASD and SLI

Link

Our new article on disfluency in children with autism spectrum disorders (ASD) or specific language impairment (SLI) is now out in PLOS ONE. (The team consisted of Heather MacFarlane—who also did most of the annotation and much of the writing—myself, and Rosemary Ingham, Alison Presmanes Hill, Katina Papadakis, Géza Kiss, and Jan van Santen.)

There is a long-standing clinical impression that children with ASD are in some ways more disfluent than typically developing children, something likely related to their general difficulties with the set of abilities known as pragmatic language. We found that the few prior attempts to quantify this impression were difficult to interpret, and in some cases, put forth contradictory findings. One limitation that we observed in the prior work (other than poor controls and small samples, which one more or less expects in this area) is the lack of a well-thought-out schema for talking about different kinds of disfluency. While specialists in disfluency have largely operated “under the hypothesis that different types of disfluency manifest from different types of processing breakdowns”, so it is valuable to have a taxonomy of the types of disfluency so as to know what to count. Thus one of our goals in the paper is to adapt—to simplify, really—the schema used by Elizabeth Shriberg (in her 1995 UC Berkeley dissertation) and show that semi-skilled transcribers can achieve high rates of interannotator agreement using our schema. (We also show that much of the annotation can be automated, if one so chooses, and provide code for that.) Of course, we are even more interested in what we can learn about pragmatic language in children with ASD from our efforts at quantifying disfluency.

In in sample of 110 children with ASD, SLI, or typical development, we find two robust results. First, we found that children with ASD produced a higher ratio of content mazes (repetitions, revisions, and false starts) to fillers (e.g., uhum) compared to their typically developing peers. Secondly, we found that children with ASD produced lower ratios of cued mazes—that is, content mazes that contain a filler—than their typically developing peers. We also found a suggestive result in a follow-up exploratory analysis: the use of cued mazes is positively correlated with chronological age in typically developing children (but not in children with ASD or SLI), which at least hints at a maturational account.

If you have anything to add, please feel free to leave post-publication comments at the PLOS one website.

Classifying paraphasias with NLP

Link

I’m excited about our new article in the American Journal of Speech-Language Pathology (with Gerasimos Fergadiotis and Steven Bedrick) on automatic classification of paraphasias using basic natural language processing techniques.

Paraphasias are speech errors associated with aphasia. Roughly speaking, these errors may be phonologically similar to the target (dog for the target LOG) or dissimilar. They also may be semantically similar to the target (dog for the target CAT), or both (rat for the target CAT). Finally, they may be neologisms (tat for the target CAT). Finally, some paraphasias may be real words but neither phonologically nor semantically similar. The relative frequencies of these types of errors differ between people with aphasia. These can be measured in a confrontation naming task and, with complex and time-consuming manual error classification, used to create individualized profiles for treatment.

In the paper, we take archival data from a confrontation naming task and attempt to automate the classification of paraphasias. To quantify phonological similarity, we automate a series of baroque rules. To quantify semantic similarity, we use a computational model of semantic similarity (namely cosine similarity with word2vec embeddings). And, to identify neologisms, we use frequency in the SUBTLEX-US corpus. The results suggest that test scoring can in fact be automated with performance close to that of human annotators. With advances in speech recognition, it may soon be possible to develop a fully-automated computer-adaptive confrontation naming task in the near future!

Using the P2FA/FAVE-align SCOTUS acoustic models in Prosodylab-Aligner

Chris Landreth writes in with a tip on how to use the SCOTUS Corpus acoustic model (the one used in P2FA and FAVE-align) from within Prosodylab-Aligner. This is as simple as downloading the data and modifying the YAML configuration file and placing the model data in the right place. Here is the 16k model.

To use it, simply download into your working directory and then execute something like the following:

python3 -m aligner -r eng-SCOTUS-16k.zip -a yrdata -d eng.dict

Please let me know if you have any problems with that.

Your libfix and blend report for May 2016

Two bits of creative morphology I’ve been seeing around the city:

  • Lime-a-rita: This trademark (of Anheuser-Busch InBev) isn’t just a redundant way to refer to a margarita (which has a lime base—a non-lime “margarita” is a barbarism), but rather a “light American lager” blended with additional lime-y-ness. I have to imagine this coinage, albeit rather corporate, was helped along by the existence of the truncation ‘rita, occasionally used in casual conversation by their most comitted devotees.
  • -otto: I first came aware of this through pastotto, the suggested name for a dish of pasta (perhaps penne), fried in olive oil and butter and then cooked in stock, like risotto; according to popularizer Mark Bittman, this is an old trick. Now, that one looks a bit blend-y, given that the ris- part of risotto is really a reference to arborio rice, and that the final -a in the base pasta appears to be lost in the combination. But not so much for barleyotto, which satisfies even the most stringent criteria for libfix-hood.

Understanding text encoding in Python 2 and Python 3

Computers were rather late to the word processing game. The founding mothers and fathers of computing were primarily interested in numbers. This is fortunate: after all, computers only know about numbers. But as Brian Kunde explains in his brief history of word processing, word processing existed long before digital computing, and the text processing has always been something of an afterthought.

Humans think of text as consisting of ordered sequence of “characters” (an ill-defined Justice-Stewart-type concept which I won’t attempt to clarify here). To manipulate text in digital computers, we have to have a mapping between the character set (a finite list of the characters the system recognizes) and numbers. Encoding is the process of converting characters to numbers, and decoding is (naturally) the process of converting numbers to characters. Before we get to Python, a bit of history.

ASCII and Unicode

There are only a few character sets that have any relevance to life in 2014. The first is ASCII (American Standard Code for Information Interchange), which was first published in 1963. This character set consists of 128 characters intended for use by an English audience. Of these 95 are printable, meaning that they correspond to lay-human notions about characters. On a US keyboard, these are (approximately) the alphanumeric and punctuation characters that can be typed with a single keystroke, or with a single keystroke while holding down the Shift key, space, tab, the two newline characters (which you get when you type return), and a few apocrypha. The remaining 33 are non-printable “control characters”. For instance, the first character in the ASCII table is the “null byte”. This is indicated by a '' in C and other languages, but there’s no standard way to render it. Many control characters were designed for earlier, more innocent times; for instance, character #7 'a' tells the receiving device to ring a cute little bell (which were apparently attached to teletype terminals); today your computer might make a beep, or the terminal window might flicker once, but either way, nothing is printed.

Of course, this is completely inadequate for anything but English (not to mention those users of superfluous diaresis…e.g., the editors of the New Yorker, Motörhead). However, each ASCII character takes up only 7 bits, leaving room for another 128 characters (since a byte has an integer value between 0-255, inclusive), and so engineers could exploited the remaining 128 characters to write the characters from different alphabets, alphasyllabaries, or syllabaries. Of these ASCII-based character sets, the best-known are ISO/IEC 8859-1, also known as Latin-1, and Windows-1252, also known as CP-1252. Unfortunately, this created more problems than it solved. That last bit just didn’t leave enough space for the many languages which need a larger character set (Japanese kanji being an obvious example). And even when there are technically enough code points left over, engineers working in different languages didn’t see eye-to-eye about what to do with them. As a result, the state of affairs made it impossible to, for example, write in French (ISO/IEC 8859-1) about Ukrainian (ISO/IEC 8859-5, at least before the 1990 orthography reform).

Clearly, fighting over scraps isn’t going to cut it in the global village. Enter the Unicode standard and its Universal Character Set (UCS), first published in 1991. Unicode is the platonic ideal of an character encoding, abstracting away from the need to efficiently convert all characters to numbers. Each character is represented by a single code with various metadata (e.g., A is an “Uppercase Letter” from the “Latin” script). ASCII and its extensions map onto a small subset of this code.

Fortunately, not all encodings are merely shadows on the walls of a cave. The One True Encoding is UTF-8, which implements the entire UCS using an 8-bit code. There are other encodings, of course, but this one is ours, and I am not alone in feeling strongly that UTF-8 is the chosen encoding. At the risk of getting too far afield, here are two arguments for why you and everyone you know should just use UTF-8. First off, it is hardly matters much which UCS-compatible encoding we all use (the differences between them are largely arbitrary), but what does matter is that we all choose the same one. There is no general procedure for “sniffing” out the encoding of a file, and  there’s nothing preventing you from coming up with a file that’s a French cookbook in one encoding, and a top-secret message in another. This is good for steganographers, but bad for the rest of us, since so many text files lack encoding metadata. When it comes to encodings, there’s no question that UTF-8 is the most popular Unicode encoding scheme worldwide, and is on its way to becoming the de-facto standard. Secondly, ASCII is valid UTF-8, because UTF-8 and ASCII encode the ASCII characters in exactly the same way. What this means, practically speaking, is you can achieve nearly complete coverage of the world’s languages simply by assuming that all the inputs to your software are UTF-8. This is a big, big win for us all.

Decode early, encode late

A general rule of thumb for developers is “decode early” (convert inputs to their Unicode representation), “encode late” (convert back to bytestrings). The reason for this is that in nearly any programming language, Unicode strings behave the way our monkey brains expect them to, but bytestrings do not. To see why, try iterating over non-ASCII bytestring in Python (more on the syntax later).

>>> for byte in b"año":
...     print(byte)
...
a
?
?
o

There are two surprising things here: iterating over the bytestring returned more bytes then there are “characters” (goodbye, indexing), and furthermore the 2nd “character” failed to render properly. This is what happens when you let computers dictate the semantics to our monkey brains, rather than the other way around. Here’s what happens when we try the same with a Unicode string:

>>> for byte in u"año":
...     print(byte)
...
a
ñ
o

The Python 2 & 3 string models

Before you put this all into practice, it is important to note that Python 2 and Python 3 use very different string models. The familiar Python 2 str class is a bytestring. To convert it to a Unicode string, use the str.decode instance method, which returns a copy of the string as an instance of the unicode class. Similarly, you can make a str copy of a unicode instance with unicode.encode. Both of these functions take a single argument: a string (either kind!) representing the encoding.

Python 2 provides specific syntax for Unicode string literals (which you saw above): the a lower-case u prefix before the initial quotation mark (as in u"año").

When it comes to Unicode-awareness, Python 3 has totally flipped the script; in my opinion, it’s for the best. Instances of str are now Unicode strings (the u"" syntax still works, but is vacuous). The (reduced) functionality of the old-style strings is now just available for instances of the class bytes. As you might expect, you can create a bytes instance by using the encode method of a new-style str. Python 3 decodes bytestrings as soon as they are created, and (re)encodes Unicode strings only at the interfaces; in other words, it gets the “early/late” stuff right by default. Your APIs probably won’t need to change much, because Python 3 treats UTF-8 (and thus ASCII) as the default encoding, and this assumption is valid more often than not.

If for some reason, you want a bytestring literal, Python has syntax for that, too: prefix the quotation marks delimiting the string with a lower-case b (as in b"año"; see above also).

tl;dr

Strings are ordered sequences of characters. But computers only know about numbers, so they are encoded as byte arrays; there are many ways to do this, but UTF-8 is the One True Encoding. To get the strings to have the semantics you expect as a human, decode a string to Unicode as early as possible, and encode it as bytes as late as possible. You have to do this explicitly in Python 2; it happens automatically in Python 3.

Further reading

For more of the historical angle, see Joel Spolsky’s epic essay The absolute minimum every software developer absolutely, positively must know About Unicode and character sets (no excuses!).