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Exploring Solution Spaces, Keith Ray's blog on Software development and other topics.
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2004.Jul.31 Sat
Alistair Cockburn's chapter on project-tracking using burn-up charts, burn-down charts, "iceberg lists", and earned-value: http://alistair.cockburn.us/crystal/articles/evabc/earnedvalueandburncharts.htm
2004.Jul.27 TueAn alternative implementation of the function alloc(size_t size) could be defined to return a pointer to a block of memory that has the size at the front of it. In fact, this is how many implementations of these library functions are implemented -- but it wasn't standardized, and it wasn't made typesafe -- on those implementations where this was done, alloc would return a pointer to the data portion of the block, and you would have to "back up" and typecast the pointer to get the length portion of the block. A semi-typesafe example:
struct MemoryBlock
{
size_t block_size;
unsigned char block_data[]; // unbounded array
};
MemoryBlock* Alloc( size_t sizeIn );
void Free( MemoryBlock* blockIn );
While this has the benefit of less space on the "client" side of the function (retaining one pointer instead of a struct with two fields) the danger of this style is that heap corruption is more likely - bad code writing past either end of the data field can erase those block_size fields.
Consider all the debugging tools we have today - would we need Purify, SmartHeap, and all those other tools as much if library functions like alloc and free had been implemented in a more object-oriented fashion?
I'm currently trying to debug some code (not written by me) that mixed C and C++ memory-management: it used "free" on memory allocated by "new char[]" and "delete []" on memory allocated by "alloc". I think these functions were smart enough not to work with memory that the other set of functions allocated, so there were memory leaks. In some implementations, these functions might be safely interchangeable for non-object allocations, in other implementations you can expect crashes.
So I fixed the code to be consistent, but I'm also getting crashes because some C++ objects are being deleted more than once [messing up the heap]. Apple's DebugMalloc provides some help in determining when the heap is messed up, but the irony is that DebugMalloc's leak detection feature works by implementing a form of garbage collection - it reports a leak when a memory allocation is no longer being pointed to. If I had real garbage collection, (or if the original coder had used boost::shared_ptr) I wouldn't have to worry about double-deletes.
2004.Jul.26 MonBad APIs start at the very beginning. For example, the C function alloc(size_t size) - a function to allocate memory in the heap - creates a block of memory; but what does it return? Not a data-structure describing the block, but half of that information, just the pointer. Imagine what could have happened if that function has been defined correctly:
struct MemoryBlock
{
char* block_start;
size_t block_size;
};
MemoryBlock Alloc( size_t sizeIn );
void Free( MemoryBlock * blockIn );
If these two pieces -- pointer and length -- were always kept together, then other data-types implemented in C, like strings could have been safer...
void StringCopy( MemoryBlock* destString, MemoryBlock* sourceString );2004.Jul.20 Tue
Eventually, every programmer has to learn to make sustainable improvements in code that maintain or improve the goodness of its design, rather than unsustainable "patching" of code, which degrades the goodness of its design.
Someone complains that members of his team are patching code instead of improving it, and therefore Extreme Programming isn't "scalable". The fact is, this lesson about the inappropriate use of "patching" is something that needs to be learned even if the team isn't doing XP. If it is doing XP, they are going to learn this lesson more quickly and more obviously than they would in a non-XP environment: their velocity is going to slow down over time until they can't create any new user-value within a single iteration. They will be forced to start refactoring ("refactoring" means improving the design of the code, not "rewriting" as many people seem to think). It seems that many if not most first-time XP teams have to learn the importance of refactoring from experience.
How do people know when a chicken or some other bird has avian flu? Does it get a runny beak? Can chickens sneeze?
2004.Jul.13 Tue
Notes From the WWDC Keynote (seen on video)
WWDC 2004 - 3500 developers attending - 17% increase over last year
Apple Stores - started 3 years - now have 80 stores
20 million visitors per year
250 million $ sales of third-party software
ginza store in tokyo
itunes music store - 70% market share for legal downloads, europe 62% of sales, 700,000 songs
ipod = 50% market share by units sold
airport express & airtunes - rendezvous for your home stereo - lossless compression and encryption - itunes streaming to target base station
BMW - 3 series, minicoopers, etc., dealer-installed connection for ipod (in glove box) and car stereo/stereo-controls.
all powermacs are dual processor now.
1.25 gigahertz bus - faster than pcs
ibm = 2.0 to 2.5 gigahertz - 25.% increase
intel = 3.2 to 3.6 gigahertz - 12% increase
LCD displays - competitors buy the panels that apple rejects
20-inch, 23-inch aluminum, connect to pcs, macs, powerbooks, and 30-inch aluminum (g5 only with special video card using two dual-dvi connections). G5 can drive two 30-inch displays - 8 million pixels (single display) 2500x1600 4.1 million pixels 77% more than the 23-inch, $3299 ; all have dual firewire and usb ports built in - single cable that splits, dvi connection.
panther - pixlet? - 12 million users - 50% of installed base - no other "new OS" has this many users, - 12,000 applications "transition is now over"
industry has had only three major OS transitions so far
apple II to MacOS 1984
DOS to Win95 - 1995
MacOS to MacOS X - 2000
Win95 +etc to Longhorn - 2007
microsoft office 2004 - "better than windows version"
borland - java tools
quark
oracle - 10g database
peoplesoft
sun - java tools
alias - bob bennet - maya complete - 25% of maya sales are for mac - alias sketchbook pro - 70% of downloads are for mac - maya unlimited "cloth, hair, fluid" effects used in games and movies - Lord of the Rings
MYST IV - Revelation - simultaneous release on Mac and PC - music by peter gabriel
guitar rig - low-latency audio - daniel haver - garage band plugin (and stand-alone) - foot controller to step through pre-sets, custom tones, sounds like analog instruments/amps/etc. studio and live-stage performances
orbit - aran anderson - satellite simulations - 650 actual unclassified sats - computations to locate these used to take super-computer, developed in 3 months using xcode (one developer) - free freefall screen saver to ship
macos x 10.4 tiger - ship 2005 "first half of year" - apple is again innovator and others will be following ('other people still trying to copy panther') - 150+ new features - OS X is #1 "unix" os by unit shipments - new feature 64-bit for any process, 64-bit system library, can also run 32-bit processes, LP64 GCC support, better SMP fine-grain locking, XGRID built-in, access control lists
improved SMB performance, home directories, Kerberos and NTLMv2 authentication, HTML email, word tables in TextEdit
search - itunes search is fast, now do the same thing in the rest of OS - "spotlight" - standard files formats, extensible, works with current apps, spotlight integrated into address book, mail, system preferences, and finder, search copyright metadata, search fields built into finder window, search by "color space" to find CMYK images, save queries as "smart folders"
spotlight addressbook - save a query as a "smart group", search birthday "within next seven days"
spotlight mail - search 50,000 messages instantly, save a query as a "smart mailbox"
spotlight prefers - removed "favorites" bar - search for prefs related to "keyboard" or "desktop" including synonyms for microsoft terms ilke "wallpaper". ("wifi" = "airport" = "802.11")
search for "everything abuot bertrand" across multiple apps - system-wide search in menu bar - shows pop-down list for images, movies, mail messages, address book contacts, pdf documents (like "half dome" in a PDF map), can show in window for complete lists, sort by kind/date/people
spotlight sdk "today"
H.264 - quicktime video - standard codec from MPEG group for high-def DVDs, scalable from high-def down to "3G" cell phone - open industry standard, frank casanova - 250 million copies of QuickTime shipped, can display high-def image as same data-rate as today's std-def DVD rates, will be built into DVDs soon.
safari web browser - RSS and Atom support - "personal clipping service" - searching "tons of rss feeds" and save queries as bookmarks, sort by date or "this week", time, source of article, change length of articles to display in list format, i-tunes store has RSS feed of "top ten songs", group feeds together in 'tabs'
"core audio" already shipping - "core image" & "core video" to ship in tiger - uses "GPU" to do graphics processing in floating-point. allows real-time filters, 100+ filters built-in. extensions via "image units" and "video units"
phil schiller - "fun-house" demo app - over a billion floating-point calcs per second - "stack many effects" on top of each other - built on top of quartz - effects can be applied to text, non-destructive, live, active - any of the stacked filters can be tweaked independently, apply filters to quicktime video, implemented in one person-week in xcode
".mac" - half a million subscribers - sync engine built-into tiger, .mac preference panel, sync email, calendars, address boosk, etc., across .mac and multiple macs - sync sdk for other apps to use.
dashboard - "expose for widgets" - built on webkit - javascript - little accessory apps - calculator, address book, itunes, stickie, stock tracker, web-cam viewers, and others. one button to bring up the widget collection, single-key-press to show/hide all the widgets - sdk available today
automator - visual scripting - interactive scripts, 100 actions built-in, share and email scripts, iLife, email and access to other apps - sal soghoian - script to grab images from web (.mac home pages) - icons for various popular 'categories', list of actions for each category - drag action to "work-flow area" - automatically link actions together, click various settings for each action [radio buttons, pop-up menus, etc.], looks like this 'settings' GUI may be generated from applescript 'dictionary' of various apps. save "work-flow" scripts "into" various applications like Safari - makes scripting about as easy as hypercard, but different UI - SDK shipping today
ichat - personal video conferences that "just worked" - now using H.264 - multiple users - 10 chatters for audio + 3 with video/audio - the 3 video feeds are joined into a single image/window - the 2nd and 3rd video feeds have a "perspective" look to them. [actually 4 videos - yourself is shown in small image]
developer copy of Tiger today
Brad Appleton wrote a very good post on the XP mailing list about his experience with a Little-League baseball coach who collected a lot of metrics, using them to improve the kids' game, but not using them as rewards or incentives (or blaming/dis-incentives.) A few quotes:
I used to play little-league baseball. Overzealous parents and coaches were too often the norm, and made it be so much about winning-vs-losing that it sucked a lot of the fun and learning/improving right out of it.
Then one year I played for a team that had a manager that was different. He abhorred all that other stuff. He was big on strategy and using data. [...] He used a lot of that to help him come up with the batting line-up, which people were best at fielding which positions, pinch-hitting and relief-pitching.
He shared the info with the assistant coaches. The info was not shared with us kids. For starters, we were possibly a bit young to try and make sense of it, but he also didn't want to see it used to try and rank people as better/worse than one another.
[...]
Anyway, with all that data-gathering going on, and the way it was shared, it was NEVER used as reward/incentive. We all knew what our win/loss record was. After each game (win or lose) the very next practice the manager led a discussion about things that we did well, and then areas for improvement - which usually became our "drills" for the rest of that practice session.
Whenever we played a particularly significant game, at the very beginning, the manager would tell us we were going out for ice-cream afterward REGARDLESS of whether we won or lost. Other teams and managers never did that. They only went out to the ice-cream parlor if they won. [...]
I was never before on a little-league team that was so motivated, and enjoyed playing so much, and that so actively encouraged other team members (especially the weaker players, who needed it much more than our "all-stars"). All in all it was a great season, and the best I recall in my own little-league "career". We lost only one game all season. [...]
I have a feeling we wouldn't have done as well if rewards like "ice-cream" had been conditional upon winning. I know we certainly wouldn't have enjoyed it as much. [...]