Mittwoch, 16.05.2012
dungeon keys but what irquote ve seen
an increase in main memory is an inexpensive experiment that often yields dramatic results. that, then is the second easy principle: get more memory, and make better use of what you have. lots of people, including managers, seem to appreciate that memory matters. disk drives deserve doubt a final tip for the performance-hungry is to be suspicious of disk drives. mass storage has made amazing strides in density and reliability over the last few decades, but what irquote ve seen lately is that at least some manufacturers appear to be stretching the quality of their operations too thin. results include some units that fail outright and far more that simply give variable results.
unless you measure carefully, you donrquote t know the true average access time or throughput of your disk subsystems. this can be particularly frustrating when mass storage is configured as raid, san, or other modern technologies. a particular unit might fail frequently, but the only consequence apparent at the application level is spooky variations in over-all performance. it can easily happen, for example, that most of the elapsed time of a particular program goes to error-correction within a raid unit that has effectively lost one entire spindle. what can you do about this?
plenty of remedies are possible, but theyrquote re poorly documented; i know them largely as the folklore that system administrators pass on in person. here are a few highlights: buy equipment you trust. mass storage is a domain where you can pay for dependable products rather than accepting lowest bids. donrquote t push the envelope. let others shake down sans, the latest-generation scsi, gigaether storage, and other offerings. look for measurability in the products you buy. find disk drives that monitor their own performance and circumstances, including temperature. keep records so you know what to expect from your equipment. if your projects are big enough, you willrun into disk mysteries. yourquote ll be far better off with a documented baseline than trying to track down a failure after it has begun to happen.
experienced an even more dramatic wow eu gold
pythonrquote s list comprehensions make this particularly economical to express; the same principle applies in any language you might have at hand, though: listing 3. minimal decorate-sort-undecorate illustration, in python sorting the derived dataset can easily accelerate the overall operation by an order of magnitude or more. calculations of computational complexity seem to be one of the harder subjects for students; thererquote s no doubt of their value, though, when they lead to such speedups.
500 times as quick independent consultant alex martelli experienced an even more dramatic breakthrough just last year. as he related in the python business forum mailing list, he had implemented an xml processor that required eight hours to complete its task. that was unacceptable; end-users simply couldnrquote t wait that long. he combined several fixes to bring the time down to one minute emdash a factor of 500 over where he started!
first, he switched from the built-in python xml libraries to the specialized pyrxp parser. this is the same pyrxp that made an appearance in a previous developerworks article on the performance of xml processing; see resources for a link to the article. along with its thriftier use of processing cycles, pyrxp also dramatically slashes memory footprint, when compared to other python-bound xml engines. this makes an enormous difference, and is typical of many performance bottlenecks: applications are starved for memory. even formally favorable algorithms can slow catastrophically if they use so much memory as to require swapping. that was martellirquote s biggest problem. so, when evaluating alternative products or algorithms, benchmark not just their apparent throughput but also their memory impact. the latter often dominates the effective scalability of production applications. moreover, if you decide to try solving a performance problem by throwing hardware at it, as is often wise, start by considering more memory.
Montag, 14.05.2012
your company is up to aion leveling
this is vital in your editorrquote s note. your note focuses too much on what your company is doing. you have to assume that people are more interested in their homes and remodeling than on what your company is up to. limit yourself to one paragraph that talks about you. trust that the expertise exhibited in your article will convince people to contact you. also, the note shifts back and forth from ldblquote irdblquote to ldblquote we.rdblquote who am i actually dealing with? beef up your calls to reader actions too emdash especially those that focus on reader response. be sure that any calls to action occur in their own, short, paragraph. those are my thoughts, carol. let me know what you think and if you need any clarification.
best wishes, garrett the extraordinary homes newsletter excerpted subject line: may 2003: more about extraordinary homesrquote convenience built-ins you are receiving this email because you subscribed to our extraordinary homes quarterly e-newsletter about home design ideas and trends. in this interim email you will learn about more of our collectionrquote s convenience built-ins. the bottom of this email describes subscribing, unsubscribing, changing your contact/email information and our privacy policy. contents: carolrquote s comments article endash aging in place: fabulous features that make it easy to remain in your home as you age article summaries: 1. housing features: what baby-boomer buyers want 2. bomb shelters updated: safe at home 3.
all clear: add space, light and brightness to your home with a touch of glass 4. rooms for your wish list: new homes, new flexibility with floor plans 5. high-speed internet at home: broadband gets built in 6. remodel rather than relocate: boomers remodel empty nests their way 7. a caution about safe rooms: a war room at home 8. humble no more: bathrooms are bigger and glitzier dear fans of our high-wow!-factor convenience built-ins, a recent national association of homebuilders survey revealed that one-fourth of the 26 million home remodeling projects completed yearly involve at least one improvement that relates to the aging of the adults in the household. none of us wants to move into a retirement home or in with our kids. aarp and others publish long lists of well-known characteristics that make homes livable well into their ownersrquote retirement years. but i have over 100 less-well-known possibilities in my collection that also dramatically improve a homerquote s ability to support our living in it well beyond our 60s and 70s.