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  • In Bjarne's book.

    - by atch
    Guys in one of excersises (ch.5,e.8) from TC++PL Bjarne asks to do following: '"Run some tests to see if your compiler really generates equivalent code for iteration using pointers and iteration using indexing. If different degrees of optimization can be requested, see if and how that affects the quality of the generated code"' Any idea how to eat it and with what? Thanks in advice.

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  • An extended Bezier Library or Algorithms of bezier operations

    - by Sorush Rabiee
    Hi, Is there a library of data structures and operations for quadratic bezier curves? I need to implement: bezier to bitmap converting with arbitrary quality optimizing bezier curves common operations like subtraction, extraction, rendering etc. languages: c,c++,.net,python Algorithms without implementation (pseudocode or etc) could be useful too. (especially optimization)

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  • Is there any working implementation of reverse mode automatic differentiation for Haskell?

    - by Ian Fiske
    The closest-related implementation in Haskell I have seen is the forward mode at http://hackage.haskell.org/packages/archive/fad/1.0/doc/html/Numeric-FAD.html. The closest related related research appears to be reverse mode for another functional language related to Scheme at http://www.bcl.hamilton.ie/~qobi/stalingrad/. I see reverse mode in Haskell as kind of a holy grail for a lot of tasks, with the hopes that it could use Haskell's nested data parallelism to gain a nice speedup in heavy numerical optimization.

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  • C#: Shift left assignment operator behavior

    - by Austin Salonen
    I'm running code that sometimes yields this: UInt32 current; int left, right; ... //sometimes left == right and no shift occurs current <<= (32 + left - right); //this works current <<= (32 - right); current <<= left; It appears for any value = 32, only the value % 32 is shifted. Is there some "optimization" occurring in the framework?

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  • How to convert closed bezier curves to Bitmaps?

    - by Sorush Rabiee
    I need an algorithm to convert a closed bezier curve (perhaps self-crossing) to a binary bitmap: 0 for inside pixels and 1 for outside. I'm writing a code that needs to implement some operations on bezier curves, could anybody give me some resources or tutorials about beziere? Wikipedia and others didn't say anything about optimization, subtracting, union, knot insertion and deletion and other operations :-)

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  • Are GUIDs the ultimate ID?

    - by mafutrct
    I noticed some people don't bother having the usual incremented number as ID but instead simply generate a GUID. The advantages include: Quick and easy No need to keep track of previous IDs Guaranteed to be unique even across machines without knowledge of each other Some disadvantages are: Possibly performance bottleneck Uses a large number of bytes My understanding is that using a GUID is beneficial in most cases, except if optimization for time or space is an issue. Did I miss something? Or do you agree with this idea?

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  • NHibernate: inserting additional calculated column

    - by Andrey Shchekin
    What would be your approach with NHibernate to do the following: When Comment is inserted into DB, and its property Text is inserted into column Text (due to a mapping), insert into column TextHash a hash of this property value. It seems trivial if I map TextHash, but how should I do this without mapping it? I do not need it in the domain model, its a DB-level optimization (I would use computed HashBytes if not for the length limit).

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  • C++ Program Always Crashes While doing a std::string assign

    - by bbazso
    I have been trying to debug a crash in my application that crashes (i.e. asserts a * glibc detected free(): invalid pointer: 0x000000000070f0c0 **) while I'm trying to do a simple assign to a string. Note that I'm compiling on a linux system with gcc 4.2.4 with an optimization level set to -O2. With -O0 the application no longer crashes. E.g. std::string abc; abc = "testString"; but if I changed the code as follows it no longer crashes std::string abc("testString"); So again I scratched my head! But the interesting pattern was that the crash moved later on in the application, AGAIN at another string. I found it weird that the application was continuously crashing on a string assign. A typical crash backtrace would look as follows: #0 0x00007f2c2663bfb5 in raise () from /lib64/libc.so.6 (gdb) bt #0 0x00007f2c2663bfb5 in raise () from /lib64/libc.so.6 #1 0x00007f2c2663dbc3 in abort () from /lib64/libc.so.6 #2 0x00000000004d8cb7 in people_streamingserver_sighandler (signum=6) at src/peoplestreamingserver.cpp:487 #3 <signal handler called> #4 0x00007f2c2663bfb5 in raise () from /lib64/libc.so.6 #5 0x00007f2c2663dbc3 in abort () from /lib64/libc.so.6 #6 0x00007f2c26680ce0 in ?? () from /lib64/libc.so.6 #7 0x00007f2c270ca7a0 in std::string::assign (this=0x7f2c21bc8d20, __str=<value optimized out>) at /home/bbazso/ThirdParty/sources/gcc-4.2.4/x86_64-pc-linux-gnu/libstdc++-v3/include/bits/basic_string.h:238 #8 0x00007f2c21bd874a in PEOPLESProtocol::GetStreamName (this=<value optimized out>, pRawPath=0x2342fd8 "rtmp://127.0.0.1/mp4:pop.mp4", lStreamName=@0x7f2c21bc8d20) at /opt/trx-HEAD/gcc/4.2.4/lib/gcc/x86_64-pc-linux-gnu/4.2.4/../../../../include/c++/4.2.4/bits/basic_string.h:491 #9 0x00007f2c21bd9daa in PEOPLESProtocol::SignalProtocolCreated (pProtocol=0x233a4e0, customParameters=@0x7f2c21bc8de0) at peoplestreamer/src/peoplesprotocol.cpp:240 This was really weird behavior and so I started to poke around further in my application to see if there was some sort of memory corruption (either heap or stack) error that could be occurring that could be causing this weird behavior. I even checked for ptr corruptions and came up empty handed. In addition to visual inspection of the code I also tried the following tools: Valgrind using both memcheck and exp-ptrcheck electric fence libsafe I compiled with -fstack-protector-all in gcc I tried MALLOC_CHECK_ set to 2 I ran my code through lint checks as well as cppcheck (to check for mistakes) And I stepped through the code using gdb So I tried a lot of stuff and still came up empty handed. So I was wondering if it could be something like a linker issue or a library issue of some sort that could be causing this problem. Are there any know issues with the std::string that make is susceptible to crashing in -O2 or maybe it has nothing to do with the optimization level? But the only pattern that I can see thus far in my problem is that it always seems to crash on a string and so I was wondering if anyone knew of any issues that my be causing this type of behavior. Thanks a lot!

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  • Breakpoints dont work

    - by Ann
    Hi, All. When I set break point at some line and press Build&Go my breakpoints become yellow and my program continues. Nothing happens. I`ve unchecked Object Lazy ..., optimization levels, active target is Debug, load debugging symbols is checked. I also want to mention that my debugger never worked before.

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  • ASP.net Interview Question

    - by Amutha
    Recently i was asked (1) "How will you do performance optimization over your jQuery in ASP.net ?" (2) "How many script manager can we have in ASP.net Application?" why? (Ajax related). I have no ideas on both.Help me to grow.

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  • Comparison of algorithmic approaches to the N queens problem

    - by iceman
    I wanted to evaluate performance comparisons for various approaches to solving the N queens problem. Mainly AI metaheuristics based algorithms like simulated annealing, tabu search and genetic algorithm etc compared to exact methods(like backtracking). Is there any code available for study? A lot of real-world optimization problems like it consider cooperative schemes between exact methods and metaheuristics.

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  • Does anyone use AMPL anymore

    - by steven
    I took a class on "Intelligent Decision Making" (which was mostly an Problem Optimization class). In the class we learned about AMPL and how to extend the solvers. I haven't heard much about it lately, nor have I seen job listings for it. My question is: Is AMPL still in use anymore? If so what is it being used for? Yes, I do understand that AMPL can be replaced with Matlab, however AMPL is free and Matlab isn't even close.

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  • mysql query optimisation

    - by Bharanikumar
    i have around (1,049,906 total, Query took 0.0005 sec) in my x table , If i simply retrieve trying to retrive the particular field records , Its tooks hardly 6 mins , This is my query SELECT CUSTOMER_CODE FROM X_TBL ; CUSTOMER_CODE = UNIQUE THE ABOVE QUERY TOOK 6MIN , Tel me optimization tips for this , Also in some situation to search customer , i used the CUSTOMER_CODE in like , select CUSTOMER_CODE from X_TBL WHERE CUSTOMER_CODE LIKE "$KEY_WORD%" Regards Bharanikumar

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  • What is a good platform for building a game framework targetting both web and native languages?

    - by fuzzyTew
    I would like to develop (or find, if one is already in development) a framework with support for accelerated graphics and sound built on a system flexible enough to compile to the following: native ppc/x86/x86_64/arm binaries or a language which compiles to them javascript actionscript bytecode or a language which compiles to it (actionscript 3, haxe) optionally java I imagine, for example, creating an API where I can open windows and make OpenGL-like calls and the framework maps this in a relatively efficient manner to either WebGL with a canvas object, 3d graphics in Flash, OpenGL ES 2 with EGL, or desktop OpenGL in an X11, Windows, or Cocoa window. I have so far looked into these avenues: Building the game library in haXe Pros: Targets exist for php, javascript, actionscript bytecode, c++ High level, object oriented language Cons: No support for finally{} blocks or destructors, making resource cleanup difficult C++ target does not allow room for producing highly optimized libraries -- the foreign function interface requires all primitive types be boxed in a wrapper object, as if writing bindings for a scripting language; these feel unideal for real-time graphics and audio, especially exporting low-level functions. Doesn't seem quite yet mature Using the C preprocessor to create a translator, writing programs entirely with macros Pros: CPP is widespread and simple to use Cons: This is an arduous task and probably the wrong tool for the job CPP implementations differ widely in support for features (e.g. xcode cpp has no variadic macros despite claiming C99 compliance) There is little-to-no room for optimization in this route Using llvm's support for multiple backends to target c/c++ to web languages Pros: Can code in c/c++ LLVM is a very mature highly optimizing compiler performing e.g. global inlining Targets exist for actionscript (alchemy) and javascript (emscripten) Cons: Actionscript target is closed source, unmaintained, and buggy. Javascript targets do not use features of HTML5 for appropriate optimization (e.g. linear memory with typed arrays) and are immature An LLVM target must convert from low-level bytecode, so high-level constructs are lost and bloated unreadable code is created from translating individual instructions, which may be more difficult for an unprepared JIT to optimize. "jump" instructions cause problems for languages with no "goto" statements. Using libclang to write a translator from C/C++ to web languages Pros: A beautiful parsing library providing easy access to the code structure Can code in C/C++ Has sponsored developer effort from Apple Cons: Incomplete; current feature set targets IDEs. Basic operators are unexposed and must be manually parsed from the returned AST element to be identified. Translating code prior to compilation may forgo optimizations assumed in c/c++ such as inlining. Creating new code generators for clang to translate into web languages Pros: Can code in C/C++ as libclang Cons: There is no API; code structure is unstable A much larger job than using libclang; the innards of clang are complex Building the game library in Common Lisp Pros: Flexible, ancient, well-developed language Extensive introspection should ease writing translators Translators exist for at least javascript Cons: Unfamiliar language No standardized library functions, widely varying implementations Which of these avenues should I pursue? Do you know of any others, or any systems that might be useful? Does a general project like this exist somewhere already? Thank you for any input.

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  • What's wrong with Bundler working with RubyGems to push a Git repo to Heroku?

    - by stanigator
    I've made sure that all the files are in the root of the repository as recommended in this discussion. However, as I follow the instructions in this section of the book, I can't get through the section without the problems. What do you think is happening with my system that's causing the error? I have no clue at the moment of what the problem means despite reading the following in the log. Thanks in advance for your help! stanley@ubuntu:~/rails_sample/first_app$ git push heroku master Warning: Permanently added the RSA host key for IP address '50.19.85.156' to the list of known hosts. Counting objects: 96, done. Compressing objects: 100% (79/79), done. Writing objects: 100% (96/96), 28.81 KiB, done. Total 96 (delta 22), reused 0 (delta 0) -----> Heroku receiving push -----> Ruby/Rails app detected -----> Installing dependencies using Bundler version 1.2.0.pre Running: bundle install --without development:test --path vendor/bundle --binstubs bin/ --deployment Fetching gem metadata from https://rubygems.org/....... Installing rake (0.9.2.2) Installing i18n (0.6.0) Installing multi_json (1.3.5) Installing activesupport (3.2.3) Installing builder (3.0.0) Installing activemodel (3.2.3) Installing erubis (2.7.0) Installing journey (1.0.3) Installing rack (1.4.1) Installing rack-cache (1.2) Installing rack-test (0.6.1) Installing hike (1.2.1) Installing tilt (1.3.3) Installing sprockets (2.1.3) Installing actionpack (3.2.3) Installing mime-types (1.18) Installing polyglot (0.3.3) Installing treetop (1.4.10) Installing mail (2.4.4) Installing actionmailer (3.2.3) Installing arel (3.0.2) Installing tzinfo (0.3.33) Installing activerecord (3.2.3) Installing activeresource (3.2.3) Installing coffee-script-source (1.3.3) Installing execjs (1.3.2) Installing coffee-script (2.2.0) Installing rack-ssl (1.3.2) Installing json (1.7.3) with native extensions Installing rdoc (3.12) Installing thor (0.14.6) Installing railties (3.2.3) Installing coffee-rails (3.2.2) Installing jquery-rails (2.0.2) Using bundler (1.2.0.pre) Installing rails (3.2.3) Installing sass (3.1.18) Installing sass-rails (3.2.5) Installing sqlite3 (1.3.6) with native extensions Gem::Installer::ExtensionBuildError: ERROR: Failed to build gem native extension. /usr/local/bin/ruby extconf.rb checking for sqlite3.h... no sqlite3.h is missing. Try 'port install sqlite3 +universal' or 'yum install sqlite-devel' and check your shared library search path (the location where your sqlite3 shared library is located). *** extconf.rb failed *** Could not create Makefile due to some reason, probably lack of necessary libraries and/or headers. Check the mkmf.log file for more details. You may need configuration options. Provided configuration options: --with-opt-dir --without-opt-dir --with-opt-include --without-opt-include=${opt-dir}/include --with-opt-lib --without-opt-lib=${opt-dir}/lib --with-make-prog --without-make-prog --srcdir=. --curdir --ruby=/usr/local/bin/ruby --with-sqlite3-dir --without-sqlite3-dir --with-sqlite3-include --without-sqlite3-include=${sqlite3-dir}/include --with-sqlite3-lib --without-sqlite3-lib=${sqlite3-dir}/lib --enable-local --disable-local Gem files will remain installed in /tmp/build_3tplrxvj7qa81/vendor/bundle/ruby/1.9.1/gems/sqlite3-1.3.6 for inspection. Results logged to /tmp/build_3tplrxvj7qa81/vendor/bundle/ruby/1.9.1/gems/sqlite3-1.3.6/ext/sqlite3/gem_make.out An error occurred while installing sqlite3 (1.3.6), and Bundler cannot continue. Make sure that `gem install sqlite3 -v '1.3.6'` succeeds before bundling. ! ! Failed to install gems via Bundler. ! ! Heroku push rejected, failed to compile Ruby/rails app To [email protected]:growing-mountain-2788.git ! [remote rejected] master -> master (pre-receive hook declined) error: failed to push some refs to '[email protected]:growing-mountain-2788.git' ------Gemfile------------------------ As requested, here's the auto-generated gemfile: source 'https://rubygems.org' gem 'rails', '3.2.3' # Bundle edge Rails instead: # gem 'rails', :git => 'git://github.com/rails/rails.git' gem 'sqlite3' gem 'json' # Gems used only for assets and not required # in production environments by default. group :assets do gem 'sass-rails', '~> 3.2.3' gem 'coffee-rails', '~> 3.2.1' # See https://github.com/sstephenson/execjs#readme for more supported runtimes # gem 'therubyracer', :platform => :ruby gem 'uglifier', '>= 1.0.3' end gem 'jquery-rails' # To use ActiveModel has_secure_password # gem 'bcrypt-ruby', '~> 3.0.0' # To use Jbuilder templates for JSON # gem 'jbuilder' # Use unicorn as the app server # gem 'unicorn' # Deploy with Capistrano # gem 'capistrano' # To use debugger # gem 'ruby-debug'

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  • What are the DB smells?

    - by Jonas Byström
    We all know 'code smells', but what are the fundamental 'database smells'? I'm a DB n00b, but I'll give an example of something that I find fishy. It seems to me like when I have to join 6-8 tables together to optimize our loading that we have a DB smell? Or would that be a pretty 'normal' database layout? (Sure, early optimization is the root of all evil, but this seems to me like early pessimisation, not to mention the cumbersomeness?)

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  • MonoTouch - foreach vs for loops (performance)

    - by ifwdev
    Normally I'm well aware that a consideration like this is premature optimization. Right now I have some event handlers being attached inside a foreach loop. I am wondering if this style might be prone to leaks or inefficient memory use due to closures being created. Is there any validity to this thinking?

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  • When should I use temporary variables?

    - by Kyle
    Specifically, I'm wondering which of these I should write: shared_ptr<GuiContextMenu> subMenu = items[j].subMenu.lock(); if (subMenu) subMenu->setVisible(false); or: if (items[j].subMenu.lock() items[j].subMenu.lock()->setVisible(false); I am not required to follow any style guidelines. After optimization, I don't think either choice makes a difference in performance. What is generally the preferred style and why?

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  • Which programming language to choose? (for a specific problem/domain, details inside)

    - by Bijan
    I am building a trading portfolio management system that is responsible for production, optimization, and simulation of non-high frequency trading portfolios (dealing with 1min or 3min bars of data, not tick data). I plan on employing Amazon web services to take on the entire load of the application. I have four choices that I am considering as language. a) Java b) C++ c) C# d) Python Here is the scope of the extremes of the project scope. This isn't how it will be, maybe ever, but it's within the scope of the requirements: Weekly simulation of 10,000,000 trading systems. (Each trading system is expected to have its own data mining methods, including feature selection algorithms which are extremely computationally-expensive. Imagine 500-5000 features using wrappers. These are not run often by any means, but it's still a consideration) Real-time production of portfolio w/ 100,000 trading strategies Taking in 1 min or 3 min data from every stock/futures market around the globe (approx 100,000) Portfolio optimization of portfolios with up to 100,000 strategies. (rather intensive algorithm) Speed is a concern, but I believe that Java can handle the load. I just want to make sure that Java CAN handle the above requirements comfortably. I don't want to do the project in C++, but I will if it's required. The reason C# is on there is because I thought it was a good alternative to Java, even though I don't like Windows at all and would prefer Java if all things are the same. Python - I've read somethings on PyPy and pyscho that claim python can be optimized with JIT compiling to run at near C-like speeds.... That's pretty much the only reason it is on this list, besides that fact that Python is a great language and would probably be the most enjoyable language to code in, which is not a factor at all for this project, but a perk. To sum up: - real time production - weekly simulations of a large number of systems - weekly/monthly optimizations of portfolios - large numbers of connections to collect data from There is no dealing with millisecond or even second based trades. The only consideration is if Java can possibly deal with this kind of load when spread out of a necessary amount of EC2 servers. Thank you guys so much for your wisdom.

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  • [objective C] IPhone question about UIImageView memory menagement

    - by BQuadra
    Hi, i have a UIImageView of 1024x768 (the room of my game) and other various UIIMageView on it (the object of my game). The iPhone screen is smaller than the room (UIImageView 1024x768) .. i want to understand if the iPhone's system automatically intercepts the graphic elements outside the visible area of Room (the player's view) and unload temporarily (for memory optimization) or i must do this by hand?? thanks

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  • Are +=, |=, &= etc atomic?

    - by SF.
    Are the "modify" operators like +=, |=, &= etc atomic? I know ++ is atomic (if you perform x++; in two different threads "simultaneously", you will always end up with x increased by 2, as opposed to x=x+1 with optimization switched off.) What I wonder is whether variable |= constant, and the likes are thread-safe or do I have to protect them with a mutex? (...or is it CPU-dependent? In this case, how is it on ARM?)

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