The Null Device
Posts matching tags 'c++'
2013/9/20
Edward C++hands, or an essay by Bartosz Milewski on why C++ is harmful to progress:
I’ve been looking for a good analogy of what programming in C++ feels like and I remembered this 1990 Tim Burton movie, Edward Scissorhands.
Having scissors for hands in not all that bad. Edward has many talents: he can, for instance, create stunning dog hairdos.
I often have these kinds of thoughts after attending C++ conferences: this time it was Going Native 2013. The previous year, the excitement was all about the shiny new C++11 Standard. This year it was more of a reality check. Don’t get me wrong — there were many stunning dog hairdos on display (I mean C++ code that was elegant and simple) but the bulk of the conference was about how to avoid mutilation and how to deliver first aid in case of accidental amputation.The gist of the article is that, because of backward compatibility requirements with C (also known as “high-level assembly language”), C++ is a deathtrap, with numerous potential pitfalls and even more schemes to mitigate them, each with its own flaws and shortcomings:
The C++ lore is that you should avoid naked pointers, avoid arrays, avoid delete. So the remedy for the lameness of malloc is operator new, which is also broken because it returns a dangerous pointer and pointers are bad. We all know (and have scars on our faces to prove it) that you should use the Standard Library containers and smart pointers whenever possible. Oh, and use value semantics for passing things around. No wait! Value semantics comes with a performance penalty because of excessive copying. So what about shared_ptr and vectors of shared_ptr? But that adds the overhead of reference counting! No, here’s a new idea: move semantics and rvalue references.Milewski's solution is to move to a functional language like Haskell, or if you can't, write your C++ code as if it were in Haskell:
Of course, you might recognize all these pro-concurrency and parallelism features as functional programming — immutability and pure functions in particular. At the risk of sounding repetitive: Haskell is way ahead of the curve with respect to parallelism, including GPU programming. That was the reason I so easily converted to Haskell after years of evangelizing good programming practices in C++. Every programmer who’s serious about concurrency and parallelism should learn enough Haskell to understand how it deals with it. There is an excellent book by Simon Marlow, Parallel and Concurrent Programming in Haskell. After you read it, you will either start using functional techniques in your C++ programming, or realize what an impedance mismatch there is between parallel programming and an imperative language, and you will switch to Haskell.
2009/11/5
This juxtaposition between content and automatically served ads has recently been brought to my attention:
It would appear that the culprit is Google's ad-serving algorithm, which seems to be based on keywords or word frequencies in the content; in this case, I'm guessing that it noticed that the page was about strings, and it had an ad targetted at a number of keywords, including "string". And, hence, we have an illustration of why naïve keyword-based content matching can fail.
I imagine that Google could do better than this. They have (a) a copy of the entire Web, stored and indexed as they see fit, and (b) huge quantities of parallel-processing power to crunch through this and data derived from this. They have already used this to great effect in building statistical models of language, which they use in things like their language tools and the context-sensitive spelling correction in Wave. I imagine, though, that it could be used to implement a machine-learning system, taking content classification beyond word frequencies.
Imagine, for example, if there were a classification engine, trained on millions of web pages (and auxilliary data about them) that, when fed a web page or document, could assign it a score along several axes with some degree of accuracy. Some axes could be the obvious things: a "sex" axis, for example (with thongs falling on one side and C++ classes well on the other) could be used for things like SafeSearch. An "emotional response" axis could be used to classify how likely content is to arouse strong emotions; on one end would be accounts of lurid violence and depravity, and on the other end things like source code and stationery catalogues, with art, celebrity gossip and LiveJournal angst falling in the spaces between. As soon as a page crossed a certain point on the axis, the ad-serving algorithm could stop matching ads by keywords (you don't want ads for airfares next to a piece about an air crash, for example), or even reverse them (so that topical ads aren't shown).
In fact, one need not restrict oneself to pre-imagined axes; it's conceivable that an ad serving company with Google's resources could set up a learning engine, program it to categorise pages according to a dozen arbitrary axes, and see what comes about and what it's useful for, in turn coming up with a model for clustering web content into crisply defined categories that no human would think of. Of course, for all I know, someone at Google (or Microsoft or Facebook) could be doing this right now.
2004/11/1
The latest thing to come out of Iceland, following Björk, Múm and Sigur Rós, is a patch to allow C++ in the Linux kernel. It appears to be quite well optimised (the runtime library has been modified, bringing the cost of throwing an exception below that of calling good old printk() in the plain-C kernel). As such, it looks like it could be good for performance and stability; Darwin (the MacOS X kernel) is written in (a somewhat stripped-down) C++, and seems a lot more solid than Linux, and less likely to be destabilised by unforeseen conditions (i.e., devices/filesystems/&c. suddenly disappearing); I suspect that C++'s exception handling has something to do with this.