Thu 12 Mar 2009

The Not So Super, Super API

Posted by Steve Knight under programming
[2] Comments

Now and again you come across the ‘one size fits all’ of computer programming the ‘Super API’. It derives its name from the fact that it tries to act as a superset of a bunch of other platform-specific APIs. One good example of this is JDBC/ODBC, but there are many others. JDBC/ODBC allow access to many many database servers because they’ve normalised the API so that you can write code that doesn’t care which database it is connected to.

Now and again, though, I find myself requiring features that are not exposed in a Super API. They’re not exposed because the feature is either too niche or because it is not standard across implementations. Creating a Super API is in some ways like plastering. Once you’ve created that nice even finish across an entire wall you might find that you’re missing a few light switches.

I was reminded of this the other day when one particular super SQL API: CLSQL uses another super API: UFFI, what they do and how they do it is largely irrelevant. The important point is that I’m only going to be concerned about the operation of one of the combination of technologies (MySQL with SBCL:SB-ALIEN). I’m concerned because there is a particular SBCL feature that I want CLSQL to make use of when it calls SBCL:LOAD-SHARED-OBJECT from via UFFI. Confused? Don’t worry, it’s not that important.

In the end I found a (most heinous) way to do what I want but it occurred to me that there has to be a better way. I appreciate that there is no way that the library writer could know what I want before I want it and neither could they potentially anticipate future underlying API changes to provide for them. However, what if the library writer gave me the option of registering a per-API first-chance callback function? This function could then perform custom processing for my platform combination and then yield control back to the library when it was completed. That way I could inject any code I wanted at potentially any supported depth.

I don’t doubt that it would be difficult to produce an API like this. Certain classes of API (non reentrant APIs being one that jumps to mind) could potentially break in new and unforseen ways and library maintainers would have to be creative about how they detect and cope with errors happening in and around user injected code.

But if the injected code was simply a one-line replacement for the one-line that would otherwise have be called then it might work. Perhaps it might even be fun to try it.

 

Wed 18 Feb 2009

Look Ma! No F9!

Posted by Steve Knight under programming
1 Comment

More people should read the Design of Everyday Things. I couldn’t do the book justice but it did explain something to me that I’d never seen written down anywhere else before and was sorely reminded of today.

It seems that everyday things have something called ‘affordances’ which should give us mental clues about how they work. The design of everyday things attempts to teach us that poorly designed things lead us down wrong mental-paths and make mistakes when using those things. Mistakes that at best might get our fingers burnt or at worst cost lives.

So far so good. What do you do then when the mental-paths that people are sent down get so worn that they can’t think straight anymore? Of course, I’m talking about spreadsheets again. It seems spreadsheets are so ubiquitous and are so well understood by so many people that some people when faced with technology view it as one enormous spreadsheet. Which is ironic because we know by now that spreadsheets simply can’t be enormous because they don’t scale.

I really don’t think technologists should beat non-technologists up about their lack of technical expertise. That’s just counter-productive and plain wrong. But what do you do when you are faced with someone who has convinced themselves that it’s all one big spreadsheet? How do you explain to them that in my world there is no F9? Where’s that pencil …

 

Tue 6 Jan 2009

The Spread-able System

Posted by Steve Knight under article, programming
[2] Comments

Spreadsheets are everywhere. They are simple to create and are an immensely powerful tool. Unsurprisingly then this means that a lot of areas of business rely on spreadsheets to function correctly. But spreadsheets are dangerous too. They suffer from, well-known, fundamental flaws.

The problem is that spreadsheets are a special type of code, and I’m not talking about the Excel ‘macros’ I’m talking about the formulas. As such they probably need to be treated the same way as other types of code, but their very nature makes this difficult. But I’m getting ahead of myself, let’s first look at some of what is good and bad about spreadsheets.

Pros

Spreadsheets are remarkable for their:

  • Utility – we can bend them into almost any shape we want because they give one way to represent almost any business process;
  • Portability – we can pick up our little gobbets of data and logic and relocate them to almost anywhere inside or outside the company, in file-systems, mail servers and web-sites;
  • Simplicity – you don’t have to explain a spreadsheet to anyone. They might have to be a proto-genius to figure out how it works but the working knowledge they would need to get started is pre-loaded in their heads and ready-to-run.

Cons

So they sound pretty useful, and I like to think that I’m a pragmatic guy, so why do I hate them so much? Many have noted about the shortcomings of spreadsheets. The page on spreadsheets at Wikipedia spells it out clearly enough so I’ll paraphrase:

  1. Productivity – Working with spreadsheets requires a lot of “sheet-shuffling” to reach the required goal. The bigger the sheet, the more time is spent copying, cutting and pasting cells around.
  2. Reliability – Although what consitutes an error in a spreadsheet is subjective, the paper A Critical Review of the Literature on Spreadsheet Errors” (pdf) reveals a series of studies (some more recent than others) that have shown that approximately 5% of cells contain errors.
  3. Collaboration – Sharing a spreadsheet is difficult. Having two independent people working on the same sheet and merging their results is as far as I know impossible.

The first two items don’t bother me overly. Yes, it’s a problem but then the alternatives aren’t that great either. Consider what you would do if you didn’t have a spreadsheet to fulfill the task. You’d either do it with a bit of paper and a calculator (i.e. simulate a spreadsheet) or get a programmer to do the task for you. Either way the amount of productivity loss/gain and the amount of errors aren’t going to be that significantly different from using a spreadsheet. Don’t get me wrong, I love my fellow programmer, but we make a LOT of mistakes too. The difference perhaps is that bespoke systems usually end up getting audited (and hence fixed) and spreadsheets often don’t. Although this point is probably moot.

Good + Bad = Too Bad

My real beef is with what happens when you have the ‘pro’ of high portability with the ‘con’ of low collaborative power. You have no way of knowing which version of the spreadsheet you have is the “true” one, and which version is duff. Every copy, whether it be inadvertently through forwarding a sheet by email to someone else or explicitly by taking a ‘backup’ is a 12 foot tall baby-eating, business-crushing monster waiting to rip you and everyone you love apart.

Hug the Monster, Then Run

The thing is we kind of have to embrace the baby-business-beating monster because it’s about all we’ve got. There are some tasks, as a programmer, that I’m really happy that you as the non-programmer don’t bother me with and solve yourself in sheets. Want to set-up an intra-company phone-book as a spreadsheet so you don’t have to bother will all that “Access” voodoo? Be my guest, but I’m watching you. Want to set-up a spreadsheet to run your fantasy football so you don’t have to add two numbers together? Go right ahead, I’ll even drive you to the game so you don’t miss the turn. Want to set up a spreadsheet to calculate payments and and do a mail-merge with the results … STOP. RIGHT. NOW.

The truth is though that you might not know that you’re creating the mother-of-all spreadsheets when you start. I might not know it either but there will probably come a time when a line is crossed and then I will want to know what you’ve been doing and who you’ve been doing it with. I’m just like that.

Unless you are small company (and hence don’t have a lot of choice) you have to be very afraid of trusting anything that might lose you money to a spreadsheet. You need to be very aware of the risks and the potential-costs you are letting yourself in for. Here in Europe there is even a special interest group dedicated to highlighting the risks of spreadsheets. Those guys must throw wild parties …

The Missing Links

In my opinion there is something missing, something that can fill the gap between spreadsheet and system.

I think we need something that can:

  1. Track spreadsheet changes – Not knowing which spreadsheet is “true” and which lies (by being able to identify revisions of the sheet that have happened after yours was ‘branched’), and not being able to merge sheets is a problem. Perhaps someone solved it already, if they had that would be great.
  2. Track spreadsheets themselves – Having some more information about what sort of corporate-data was being accessed, who was using it and how frequently they ran it might alert us to potential spreadsheet monsters being born.
  3. Narrow the gap – Making spreadsheets more like traditional software systems, without significantly castrating the usefulness of the spreadsheet, would be great too. This is a little like asking for the moon on a stick though.

Perhaps I’ll make something like this one day. I have to admit it’s not a terribly exciting project but it has some potential I think. Perhaps I could spice it up by throwing a party and invite the guys from the “European Spreadsheet Risks Interest Group”. Now we’re talking. How will I budget for the 7-up, party hats and streamers? In a spreadsheet of course.

 

Fri 5 Dec 2008

The Ever Diminishing Deliverable

Posted by Steve Knight under programming
No Comments

When you’re making software in-house you can largely ship what you want, within reason. Conversely, when you’re making software for customers or clients I’m guessing you owe it to your customer, and perhaps your bottom-line, that what you produce is of the very best quality. If you don’t your customer goes somewhere else. However, the additional effort required in producing the quality software for customers can be substantial. Since you want to keep your customer, and attract new ones, you must expend the effort at a potentially large personal cost.

When you’re making software in-house there is a well-known danger of gilding the lilly. Indeed, in-house the law of diminishing returns comes into force if you spend too much time making your in-house project of the very highest quality. The law of diminishing returns can best be described as:

… in a production system with fixed and variable inputs (say factory size and labor), beyond some point, each additional unit of variable input yields less and less output. Conversely, producing one more unit of output costs more and more in variable inputs.

Since I don’t work for a software house, if I can release my code in-house when it is only partially complete, then I should be able to get a lot more stuff done for less cost.

So far so good. A problem arises, though, because I have observed that different programmers place different levels of importance on software quality. This is as probably as you’d expect, one thing we have in common is that we’re all individuals.

The sad truth is that, based on someone’s own personal standards, the bare minimum of what is required to get a job done is usually all that is done. This probably goes someway to explaining the appalling state of some of the in-house software I’ve seen, and written myself. It’s understandable because often, once the main problem has been solved the other issues like usability, maintainability, extensibility and support can be overlooked without any immediately dire consequences.

But here’s the sting, once you release something you usually have to support it too. That’s just the way in-house software works (sucks?), I guess. If you made a poor job of it then you’ll probably pay for it many many times over in support queries. In the end it seems to me that unless you quit (or are fired!) the diminishing deliverable cost turns into a potentially huge support cost. Especially if you end up layering new solutions on to an originally broken solution.

All, in all, you might as well have tried to make something a little more durable and complete at the outset. Sure you can re-factor your mistakes later, but even refactoring costs a lot more to do later than it does to get it ‘right’ at the beginning.

It seems to me that it is essentially a problem of planning. In-house software projects, big and small, aren’t usually planned properly. As a result secondary factors that would improve the overall quality are not included in any estimates. As a result of this bad planning those in-house projects are often late and buggy.

This problem is not getting any better. Years of software-development in an in-house setting have shown me that where in-house plans & design meetings exist issues of usability, maintainability and support are very minor concerns if they are concerns at all. Perhaps that should change. Just a little …

 

Sat 18 Oct 2008

Choosing a Common Lisp Unit Testing Framework

Posted by Steve Knight under lisp
1 Comment

I have recently become dissatisfied with the unit testing framework I was using: LIFT. After reading Phil Gold’s fairly comprehensive Common Lisp Testing Frameworks I decided to switch to Stefil.

So what’s so wrong with LIFT? Whilst I don’t want to detract from metabangs efforts, LIFT was annoying me enough that I was considering writing my own unit-testing framework! No one wants YAUTF (yet another unit testing framework), especially mine, so I went shopping. I should also say that I’m overjoyed with other metabang creations like bind and log5 but LIFT doesn’t seem to elevate me much any more (groan).

In my experience, your mileage might vary, LIFT seems slow for what it does. Yes, my machine is a little old and beat-up but still, the unit-testing machinery should not be a significant burden to the unit testing process itself! To illustrate this point look let’s look at a highly subjective example. Suppose I want to test the plain and simple truth, but I want to do it 10,000 times – I do this because I never take “yes” for an answer. Here’s a REPL snippet doing just that in LIFT

CL-USER> (lift:deftestsuite test-lift () ()
	     (:tests
	       (test-true
		(lift:ensure t))))

Start: TEST-LIFT#<Results for TEST-LIFT [1 Successful test]>
CL-USER> (time (loop for i from 1 to 10000 do (lift:run-tests :suite 'test-lift)))

Start: TEST-LIFT
Start: TEST-LIFT
<snip 9,997 lines;>
Start: TEST-LIFT
Evaluation took:
  4.029 seconds of real time
  2.100131 seconds of user run time
  0.076005 seconds of system run time
  [Run times include 0.06 seconds GC run time.]
  0 calls to %EVAL
  0 page faults and
  60,780,256 bytes consed.

And then let’s do the same for Stefil

CL-USER> (stefil:defsuite* test-stefil)
#<test TEST-STEFIL>
CL-USER> (stefil:deftest test-true ()
	   (stefil:is t))
.
<snip 9,997 lines;>
.
Evaluation took:
  1.238 seconds of real time
  0.932059 seconds of user run time
  0.116008 seconds of system run time
  [Run times include 0.357 seconds GC run time.]
  0 calls to %EVAL
  0 page faults and
  88,813,344 bytes consed.

Part of the slowness might be that LIFT prints “Start: TEST-LIFT” 10,000 times, but I didn’t dig any deeper. LIFT seems slow when just running a handful of suites. Apart from the slowness the output produced by LIFT isn’t really particularly useful, it’s better than nothing, but I can’t really be sure of the testing progress within a suite. Ideally I would just like to see some incremental idea of progress, and a single “.” per test and a new line after each suite, like Stefil does, is much cleaner.

Secondly, and this is the kicker, I find it difficult with LIFT to find out what went wrong and where. Which is surely the whole point of unit-testing. We expect stuff to fail and hunting down the causes of failure in LIFT is a bit tiresome via the inspector. Conversely, Stefil supports test failures by dropping you straight into the debugger when an assertion fails. Which is perfect because you can look at the code that caused the error, dig about in the source, fix it and continue the test. This is a natural way to go about developing test driven software. It also leverages the REPL making it a far more interactive experience. The only snag is that this sort of behaviour is not always what you want if you want to run automated test & build environments. Stefil provides a special variable *debug-on-assertion-failure* which registers the failure but doesn’t drop you in the debugger. It seems that LIFT does have a testing parameter break-on-error? however this only catches errors, but it probably also needs a break-on-assertion? as well.

Finally, Stefil just seems more concise & natural. Since what we’re doing here is creating functions that test other functions surely we should be able call tests like functions. In my view classes are not the primary units of a test, functions are. And so it is in Stefil because every suite & test are callable functions. In LIFT you have to tell the function lift:run-test to find you a test/suite class with a specific name and then run it.

I didn’t want this blog entry to be a ‘hatchet-job’ on LIFT. I don’t want that because that’s not constructive, and there’s already too much way-too much ranting on the internet. However, in the final analysis, LIFT could be made to be a lot better than it is. Since the effort in switching wasn’t really that great I decided to switch to Stefil rather than persevere and try to directly improve LIFT.


Phil Gold actually makes two conclusions in Common Lisp Testing Frameworks , Stefil and fiveam. I would have tried fiveam, which was Phil’s framework of choice, but it wouldn’t install via asdf. Whilst not being asdf installable isn’t a huge barrier to entry it suggests something (perhaps wrongly) about the quality of the solution. So I skipped it.

 

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