[lug] Web crawler advice

[George Sexton]

Writing multi-threaded code takes attention to detail that is beyond the 
ability of some programmers. It doesn't mean it's not useful. What's the 
point of having a nice multi-core machine if you're not using them?

It's still easier in Java than about anything else.

Nate Duehr wrote:
> George Sexton wrote:
> 
>> OTOH, threading in Java is dead easy, and this kind of app would 
>> benefit from multi-threading.
> 
> Dead-easy until it blows up.  :-)
> 
> http://www.eecs.berkeley.edu/Pubs/TechRpts/2006/EECS-2006-1.html
> 
> Threading is starting to get as bad a rap as "goto" got in the 70s.
> 
> The author specifically talks about how subtle problems will crop up on 
> multi-core machines, especially.
> 
> Had something similar lately.  The symptom was that Perl wouldn't start 
> on a 4-processor Sun box.
> 
> Perl (for some UNHOLY reason) uses floating-point math to compare the 
> main perl version number with the version numbers in any modules it 
> loads at run-time.
> 
> What had happened was that the FPU in CPU #3 on the box was flaky. Since 
> it was running very little else that required floating-point 
> calculations, the only "symptom" was, "Perl won't run consistently, or 
> dies halfway through scripts!"  (The scripts that were dying were 
> loading more modules.
> 
> Frackin' ugly troubleshooting session that was... until we "caught" the 
> FPU doing naughty things with Sun's hardware test tools.
> 
> I shudder to think how long that would have taken on PeeCee hardware 
> where such test tools simply don't (really) exist on most hardware/OS 
> combinations.
> 
> Nate
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-- 
George Sexton
MH Software, Inc.
Voice: +1 303 438 9585
URL:   http://www.mhsoftware.com/