Thursday, October 30, 2014

My First Webcast

http://www.oreilly.com/pub/e/3255

I'm a pretty good public speaker. But I've avoided webcasting and podcasting because it's kind of daunting. In a smaller venue, the audience members are right there, and you can tell if you're not making sense. In a webcast, the feedback will be indirect. In a podcast it's seems like it would be nonexistent.

Also, I find that programming is an intensely literate experience. It's about reading and writing. A podcast -- listening and watching -- seems very un-programmerly to me. Perhaps I'm just being an old "get-off-my-lawn-you-kids" fart.

But I'll see how the webcast thing goes in January, and perhaps I'll try to do some podcasts.

Thursday, October 23, 2014

Currying and Partial Function Evaluation

Old. But still interesting.

Partial Function Application is not Currying

It seems like hair-splitting. However, the distinction between bound variables and curried functions does have some practical implications.

I'm looking closely at PyMonad and the built-in functools library.

I'm finding some benefits in understanding functional programming and how to apply functional design patterns in Python. I'm also seeing the important differences between compiled -- and optimized languages -- and Python's approach. I'm slowly coming to understand how a (simple) recursive design is flattened into a for loop as part of manual tail-recursion optimization.

The functional programming goodness is giving me first-class headaches when trying to apply the lessons learned to Java, however. I suppose I should look closely at http://www.functionaljava.org and https://code.google.com/p/functionaljava/. There are claims that it's dangerously inefficient. Also, the customer who insists on Java has a (very) limited set of allowed libraries; if this isn't on the list, then the whole concept is a non-starter.

Thursday, October 16, 2014

Using Bottle as a miniature demo server

Let's talk small.

When writing API's, it sometimes helps to have a small demo web site to show the API in a context that's easy to visualize. API's are sometimes abstract, and without an application to provide some context, it can be unclear why the path looks like that or why the JSON document has those fields.

I want to emphasize the "small" part of the small demo. A small page or two with some HTML forms and a submit button. Really small.

The actual customer-facing apps (mobile, mobile web, and full web site) are being built by lots of other people. Not us. They're big. We build the API's (there are a lot) that support the data structures that support the processing that supports the user experience.

Building fake mobile apps is right out. We're not going to lard on Android SDK or Xcode development environments to our already overburdened laptops. We build backend API's.

Building a fake mobile web or full web site is appealing. What makes it complex is the UX folks are building everything in Angular.js. If we want to properly implement a form, we would have to master Angular just to do a demo for the product owner.

No thanks. Still too far afield for API developers. We're focused on mongo and JSON and performance and scalability. Not Angular.js and the UX.

What we want to do is build a small web server which runs just a few pages plucked out of the UX demo code so that we can show how interactions with a web page put stuff in a database. And vice-versa: stuff in the database will show up on a web page.

"Really?" we get asked. Some folks look askance at us for wanting to put a small demo site together.

"Yes," we answer. "Our product owner has a big vision and we're breaking that into a bunch of little API's. It's not perfectly clear how we're building up to that vision."

It's not perfectly clear how some of this work. Folks outside the scrum team have distracting questions. We want to have a page or two where we can fill in a form and click submit and stuff happens. This is far easier to explain than showing them Postman or SoapUI and claiming that this will support some user stories.

And as we grow toward the epic, the workflow aspects of this will grow. The stuff that admin "A" does after user "U" has made an initial request. Or the stuff that internal user "I" does after external user "X" has done something. But really, it's just a few small web pages. Small.

Imagine the demo. On laptop #1, we'll show user "X". On laptop #2, we're running a Mongo shell to query what's in the db. On laptop #3 we're showing user "I". The focus is really the API's. And how the API's add up to an epic collection of stories.

Serving some HTML pages

Just to make it painful, we can't simply grab the demo web pages out of the UX team's SVN repository. Why not? First, it's an Angular app. We can't just grab some HTML and go. The demo pages are served via node.js with Bower, so it's not even clear (to us) what the complete deployment looks like.

So. We cheated. We took a screen shot. We trimmed the edges of the page as .PNG files. We wrote our own form and cobbled in enough CSS to make it look close. We're not here to fake out the UX. We just want to enter some data and have it tickle our API. (Indeed, we have a "Not The Real Experience" on some pages.)

Initially, some of the team members tried serving these small pages with WebLogic. Then Jetty. It's not bad. But it's Java. It takes forever to build and deploy something after a trivial change. There are a lot of moving parts even with Jetty, and not all of them are obvious.

Since we're building "enterprise" API's, we're deeply enmeshed with every feature of the Spring Framework. Our STS/Eclipse environments are fat with add-ons and features.

While the Spring Framework ideal is to allow a developer to focus on relevant details and have the irrelevant details handled automagically, the magic almost gets in the way. These are small applications that are little more than a few static pages with forms and a submit button. Spring can do it, of course. But we're often testing our the actual API's in a Jetty server (or two). If the demo site requires yet another instance of Jetty with yet another configuration, our ability to cope diminishes.

How can we get back to small?

Python and Bottle

Python has several web servers built-in. We can use http.server. We can use wsgiref. Both of these are almost OK for what we want to do.

We can do better with two small downloads: Bottle and Jinja2. With these, we can build simple HTML pages that show some data. We can build simple servers that collect form data, use http.client to make API requests, and write copious logging details. We can write little bottle apps that handle just GETs and POSTs simply.

This is suitably small.

We can share the module with the Bottle object and the HTML mock-up pages. We can fire up the app in an instant on anyone's laptop, no matter what else they're running. We can tweak the server to adjust the logging or the API request or the form.

We actually run the server from within Idle. Make a change and hit F5 to redeploy after a change. It's small. It's fast. And it doesn't involve the huge complexities associated with Java.

Bottle doesn't do much. But what little it does do is a pretty tidy fit with tiny little demonstrations of super-simple HTML interactions.

Thursday, October 9, 2014

Scipy.optimization.anneal Problems

Well, not really "problems" per se. More of a strange kind of whining than a solvable problem.

Here's the bottom line. Two real quotes. Unedited.

Me: "> There's a way to avoid the religious nature of the argument. "
Them: "Please suggest away."

Really. Confronted with choices between anneal and basin hopping, they could only resort to hand-waving and random utterances.

The tl;dr summary is this:
  • "scipy.optimize.anneal only has three hard-wired schedule variants: ‘fast’, ‘cauchy’ or ‘boltzmann’."
  • My initial response was "And..."? 
  • "Not being able to specify my own cooling schedule severely limits the usability of the code"
A complaint that causes me deep pain: "severely limits" with no actual evidence. And no plan to get evidence beyond a religious wars style argument.

There may have been a technical question on the class definitions inside scipy. But that question was overshadowed by the essential problems with what they were doing. Or, more properly, what they were whining about.

Did they really have a problem with a state of the art solution to optimization problems? More specifically:

1. Did they read the "Deprecated" part of the scipy documentation? This is a hint that there are better solutions available. Perhaps they could start there instead of whining.
2. Did they actually read the details of the three schedules in the "Notes" section? Do they seriously think they've got a new approach that does not fit any of the various parameters of the three installed algorithms? I don't mean to be too rude, but... Do they really think they're that scale of genius?
3. Do they have any evidence that their problem is so unlike the typical case handled by basin hopping?
4. Do they have any evidence that their solution totally crushes the already-built code?

I think the answers to all four question were "no". 

I'm not even certain that I could help them with some of the Python technology required to extend scipy. But, I'm sure I cannot actually do anything of value under the circumstances that (a) they have not really tried the established algorithms and (b) they're already sure that the established algorithms can't work based on religious-wars arguments.

It was clear that they never read the "Notes" section on this SciPy page: http://docs.scipy.org/doc/scipy/reference/generated/scipy.optimize.anneal.html#scipy.optimize.anneal

One of the emails in the exchange had a kind of hand-waving justification for the problem domain being somehow unique. Lacking any actual evidence, I'm inclined to believe they were just hoping that their problem domain was unique, allowing them to dismiss the available Python solution and do something uniquely bad. 

(Optimization is not my area of expertise. Perhaps I'm way off base; perhaps the existing solutions are so problem-domain specific that everyone has to invent new technology. Maybe established solutions really don't work.)

More importantly: there was no actual evidence that the existing optimization (either annealing or basin hopping) failed to solve their problem.

But the worst part was this:

"From, a business perspective, I need to know about SA because our competitor stole our biggest client using it."

They don't actually want to innovate. They only want to try and catch up by making religious war arguments over the deprecated simulated annealing vs. basin hopping.

Thursday, October 2, 2014

Not sure what went wrong, but...

Read this: http://quantlabs.net/blog/2014/09/here-is-why-i-gave-up-on-python-aka-dogs-breakfeast-of-a-so-called-programming-language/#sthash.Rp7pXObf.dpuf

Not sure what's going on here.

"Script I want to run" seemed clear. http://vispy.org/examples/basics/scene/surface_plot.html#sthash.kIzbd33O.dpuf

The rest seemed like ill-advised trips down numerous ratholes. In particular, anything that involved Python Tools for Visual Studio seems like a waste of time and brain calories.

It's not clear at all what's not working. That's perhaps the most frustrating thing about this kind of post.

The final note, "Decisions decisions..." pointed out a simple confusion that befuddles the technically-minded. Too many details.

The decision between Python2 and 3 is trivial. There are a lot of details, but they're irrelevant for making the decision.

What package are you trying to use? It's hard to tell, but it looks like it's vispy. If so, that's all that matters. vispy works with Python3.3, requires numpy, and a "backend." Install just that and nothing more. In particular, avoid junk like Visual Studio.

The Dog's Breakfast seems to be the result of chasing down lots of details that aren't too relevant. It's hard to tell. But a scatter-shot post claiming "all this is broken" is a hint that the author wasn't simply following the vispy installation instructions. It could be that they turned something simple into a dog's breakfast by chasing irrelevant technologies all around the garden.