Re: [racket-users] How to find most efficient constructs/instructions beside benchmarking?
On 4/12/2015 10:22 AM, Lux wrote: For future reference for who will read this topic: This announcement on sqlite mailinglist seems to at least partially prove my point for usefulness of "micro-optimization", something valuable to research from my point of view. """50% faster than 3.7.17""" """ This is 50% faster at the low-level grunt work of moving bits on and off disk and search b-trees. We have achieved this by incorporating hundreds of micro-optimizations. Each micro-optimization might improve the performance by as little as 0.05%. If we get one that improves performance by 0.25%, that is considered a huge win. Each of these optimizations is unmeasurable on a real-world system (we have to use cachegrind to get repeatable run-times) but if you do enough of them, they add up.""" Read the rest on: http://permalink.gmane.org/gmane.comp.db.sqlite.general/90549 Somebody doesn't understand fractions: the numbers show a 33% improvement, not 50%. 3.7 is 50% slower, but 3.8 is only 33% faster. And the conclusion about improved code efficiency is ... not wrong per se, but not exactly correct either ... because cachegrind doesn't measure code efficiency, but rather it profiles memory accesses. A lot of that speed improvement can be explained simply by elimination of redundant data movement. SQL operations generally are hostile to CPU cache optimizations, so the objective always is to reduce overall data movement within the system. Clever implementations of set and bag operations which avoid unnecessary copying is what separates commercial quality RDBMS from toys. Note that 3.7 added major new features which slowed it wrt previous versions and many of the optimizations in 3.8 were to fix performance issues in the 3.7 functionality. Note also that they spent 16 months doing it and that 3.8 consequently has introduced only 1 significant new feature. I mentioned previously that I have done HRT programming, so I understand the urge to make code as efficient as possible. But you can spend months or years tweaking a program, only to find that the next generation CPU (or DDR4 memory system or SSD storage or ... ) makes a lot of your hard work superfluous. Most programs simply can't justify the developer time to micro optimize them. Most of the time micro optimization a waste of developer effort that would be better spent devising better algorithms and data structures - it only makes a difference where you can't squeeze anything more out of you algorithm ... a situation which is quite rare. There are some obvious cases, but most programmer guesses at where high optimization is needed are simply wrong - you really have to profile execution using representative data. In those cases where tweaking is warranted: e.g., programs with humongous data sets or requiring real time results, etc., the optimizations typically can be confined to less than 2% of the code (the other 98% of the program will not measurably benefit). In contrast, all code benefits from more efficient algorithms and data structures. George -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
[racket-users] pict3d
1) pict3d is Totally magnificent. Think I said this before. 2) New OS X mouse controls are excellent. 3) Doc bug (I think). You write "Shapes: visible 2D surfaces in 3D space. Surfaces are visible on only one side.” I believe the first word and the first word of the second sentence should be the same, e.g.: Shapes: visible 2D surfaces in 3D space. Shapes are visible on only one side. or Surfaces: visible 2D surfaces in 3D space. Surfaces are visible on only one side. John -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
Re: [racket-users] DrRacket plugin to remove trailing whitespace on save?
If you mean: "don't remove entire lines that consist of only whitespace," then I agree. If you mean: "don't remove any trailing whitespace from lines that consist only of whitespace," then I do not. -Jon On Sun, Apr 12, 2015 at 7:01 PM, Alexis King wrote: > If you decide to do this, please make it so it doesn’t trim whitespace from > whitespace-only lines. For some reason a lot of IDEs do this, and it’s a pet > peeve of mine. > > On Apr 12, 2015, at 15:14, Robby Findler > wrote: > > No but Max changed the way return works so there should be less whitespace > added going forward. > > Writing a script to trim whitespace from line-endings would work well if it > were to use text% IMO. Use load-file to get a file and then the paragraph > methods to find line endings and then delete stuff and ace the file again. > > Robby > > On Sunday, April 12, 2015, Jon Zeppieri wrote: >> >> Does such a think already exist? >> >> -Jon >> >> -- >> You received this message because you are subscribed to the Google Groups >> "Racket Users" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to racket-users+unsubscr...@googlegroups.com. >> For more options, visit https://groups.google.com/d/optout. > > > -- > You received this message because you are subscribed to the Google Groups > "Racket Users" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to racket-users+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout. > > -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
Re: [racket-users] DrRacket plugin to remove trailing whitespace on save?
No but Max changed the way return works so there should be less whitespace added going forward. Writing a script to trim whitespace from line-endings would work well if it were to use text% IMO. Use load-file to get a file and then the paragraph methods to find line endings and then delete stuff and ace the file again. Robby On Sunday, April 12, 2015, Jon Zeppieri wrote: > Does such a think already exist? > > -Jon > > -- > You received this message because you are subscribed to the Google Groups > "Racket Users" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to racket-users+unsubscr...@googlegroups.com . > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
[racket-users] DrRacket plugin to remove trailing whitespace on save?
Does such a think already exist? -Jon -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
Re: [racket-users] How to find most efficient constructs/instructions beside benchmarking?
For future reference for who will read this topic: This announcement on sqlite mailinglist seems to at least partially prove my point for usefulness of "micro-optimization", something valuable to research from my point of view. """50% faster than 3.7.17""" """ This is 50% faster at the low-level grunt work of moving bits on and off disk and search b-trees. We have achieved this by incorporating hundreds of micro-optimizations. Each micro-optimization might improve the performance by as little as 0.05%. If we get one that improves performance by 0.25%, that is considered a huge win. Each of these optimizations is unmeasurable on a real-world system (we have to use cachegrind to get repeatable run-times) but if you do enough of them, they add up.""" Read the rest on: http://permalink.gmane.org/gmane.comp.db.sqlite.general/90549 -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
[racket-users] modifying readtable entry for `(` breaks reading #hash() ?
For something like this:
#lang racket
(define orig-readtable (current-readtable))
(parameterize ([current-readtable
(make-readtable orig-readtable
#\( 'terminating-macro
(λ (c in src ln col pos)
(read-syntax/recursive src in c
orig-readtable)))])
(println (read (open-input-string "()"))) ; ’()
(println (read (open-input-string "#hash()" ; . read: bad syntax `#hash('
I can understand why this could be a problem, but why doesn't it work so that
if reading the () produces the correct association list, it still works?
Otherwise is there any way around it without just reimplementing #hash(),
#hasheq(), #hasheqv(), #(), etc. ?
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