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  • How to insert a list of data files(described in CSV file) from client location into database using PHP programming?

    - by Golam Mustafa
    We have some DVD. Each of them contain ---A CSV file containing some information about the documents. ---The list of pdf file(Scanned document). Example of CSV file Title,Author,FileName Design Document 0455, Eric Clipton,ds0455.pdf Tesign Document 0511,Johanson E,td0511.pdf I want to write PHP code that would read the CSV file , insert each information to database table as record. Can anybody help me to provide any idea about ---- How to select individual file from the client location on the basis of file name in the CSV file using PHP script. Thanks Golam

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  • New i7 is slower than old Core 2 Duo? Why? (BIOS programming)

    - by DrChase
    I've always wondered why the companies who make BIOS' either have terrible engineering psychologists or none at all. But without wasting your time further with random speculative questions, my real question is as follows: Why does my new computer run slower than my old computer? Old Computer: Intel Core 2 Duo CPU @ 3.0 Ghz (stock) 4GB OCZ DDR2 800 RAM Wolfdale E8400 mb nVidia GeForce 8600 GT New Computer: Intel Core i7 920 @ ~3.2 Ghz 6 GB OCZ DDR3 1066 RAM EVGA x58 SLI LE motherboard nVidia GeForce GTX 275 Vista x64 Home Premium on both. "Run slower" is defined as: - poorer FPS performance in the same games, applications - takes longer to start up - general desktop usage (checking email, opening up files, running exe's) is noticeably slower At first I thought I must've not set something up in the BIOS or something. But I have no idea how to set anything in the bios except for "Dummy O.C.", which brought me to ~3.2 Ghz. But beyond that I have no idea. I've been reading stuff about "ram timing" and voltages and the like but I really have no idea about that stuff. I'm a psychologist who has a basic understanding in building his own computers, not a computer scientist. Can someone give me some wisdom that might guide me to the reason my new computer is worse than my older one? I'm sorry if this is a bad question, or not appropriate to SO. I'm just pretty frustrated now and you all have helped me in the past so I figured I'd give it a shot. Thanks for your time.

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  • Puppet inheritance of parametrized classes

    - by paweloque
    I have a situation in puppet where I want to inherit from a parametrized class: class base ($basepath) { ... } class extends_base ($ext_param) inherits base { ... } Now trying to instantiate the extends_base class I get the following error message: Must pass basepath to Class[Base] However, I don't see a way how to pass the basepath parameter to the Base class.. I tried to pass the param in the Class[Extends_base] definition, puppet doesn't like this either.

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  • Delphi 2009 MS Build headaches

    - by X-Ray
    does anyone know of any good description of delphi's build system? (i know it's using MS Build.) i'm using delphi 2009. i wanted to set up a variation of the Debug build configuration that (often) has different defines (d2009 seems to call them "preprocessor symbols"). the problem i'm having is that--even though i turned off "inherit" for "Base" and "Debug"--have only very limited control. for example, i can't get rid of FastMM_. <PropertyGroup> <ProjectGuid>{D7FE7347-8E2C-438C-A275-38B8DA9244B0}</ProjectGuid> <ProjectVersion>12.0</ProjectVersion> <MainSource>oca.dpr</MainSource> <Config Condition="'$(Config)'==''">Debug</Config> <DCC_DCCCompiler>DCC32</DCC_DCCCompiler> </PropertyGroup> <PropertyGroup Condition="'$(Config)'=='Base' or '$(Base)'!=''"> <Base>true</Base> </PropertyGroup> <PropertyGroup Condition="'$(Config)'=='Release' or '$(Cfg_1)'!=''"> <Cfg_1>true</Cfg_1> <CfgParent>Base</CfgParent> <Base>true</Base> </PropertyGroup> <PropertyGroup Condition="'$(Config)'=='Debug' or '$(Cfg_2)'!=''"> <Cfg_2>true</Cfg_2> <CfgParent>Base</CfgParent> <Base>true</Base> </PropertyGroup> <PropertyGroup Condition="'$(Base)'!=''"> <DCC_StringChecks>off</DCC_StringChecks> <DCC_MinimumEnumSize>4</DCC_MinimumEnumSize> <DCC_RangeChecking>true</DCC_RangeChecking> <DCC_IntegerOverflowCheck>true</DCC_IntegerOverflowCheck> <DCC_UNIT_PLATFORM>false</DCC_UNIT_PLATFORM> <DCC_SYMBOL_PLATFORM>false</DCC_SYMBOL_PLATFORM> <DCC_DcuOutput>.\dcu</DCC_DcuOutput> <DCC_UnitSearchPath>C:\Prj\Lib\AutoQADocking\Delphi2009.Win32\Lib;$(BDS)\Source\DUnit\src;$(DCC_UnitSearchPath)</DCC_UnitSearchPath> <DCC_Optimize>false</DCC_Optimize> <DCC_DependencyCheckOutputName>oca.exe</DCC_DependencyCheckOutputName> <DCC_ImageBase>00400000</DCC_ImageBase> <DCC_UnitAlias>WinTypes=Windows;WinProcs=Windows;DbiTypes=BDE;DbiProcs=BDE;DbiErrs=BDE;$(DCC_UnitAlias)</DCC_UnitAlias> <DCC_Platform>x86</DCC_Platform> <DCC_E>false</DCC_E> <DCC_N>false</DCC_N> <DCC_S>false</DCC_S> <DCC_F>false</DCC_F> <DCC_K>false</DCC_K> </PropertyGroup> <PropertyGroup Condition="'$(Cfg_1)'!=''"> <DCC_PentiumSafeDivide>true</DCC_PentiumSafeDivide> <DCC_Optimize>true</DCC_Optimize> <DCC_IntegerOverflowCheck>false</DCC_IntegerOverflowCheck> <BRCC_Defines>MadExcept;FastMM;$(BRCC_Defines)</BRCC_Defines> <DCC_AssertionsAtRuntime>false</DCC_AssertionsAtRuntime> <DCC_LocalDebugSymbols>false</DCC_LocalDebugSymbols> <DCC_Define>RELEASE;$(DCC_Define)</DCC_Define> <DCC_SymbolReferenceInfo>0</DCC_SymbolReferenceInfo> <DCC_DebugInformation>false</DCC_DebugInformation> </PropertyGroup> <PropertyGroup Condition="'$(Cfg_2)'!=''"> <DCC_DebugInfoInExe>true</DCC_DebugInfoInExe> <BRCC_Defines>FastMM</BRCC_Defines> <DCC_DebugDCUs>true</DCC_DebugDCUs> <DCC_MapFile>3</DCC_MapFile> <DCC_Define>DEBUG;FastMM_;madExcept;$(DCC_Define)</DCC_Define> </PropertyGroup> i even had to edit it today with notepad to get rid of a DCC define that the delphi UI doesn't seem to give access to. (it said "From Delphi Compiler" for the item i couldn't remove.) does anyone know a good primer on the use of this feature in delphi? thank you!

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  • C socket programming: calling recv() changes my socket file descriptor?

    - by fourier
    Hey all, I have this strange problem with recv(). I'm programming client/server where client send() a message (a structure to be exact) and server recv() it. I am also working with multiple sockets and select(). while(1) { readset = info->read_set; info->copy_set = info->read_set; timeout.tv_sec = 1; timeout.tv_usec = 0; // 0.5 seconds ready = select(info->max_fd+1, &readset, NULL, NULL, &timeout); if (ready == -1) { printf("S: ERROR: select(): %s\nEXITING...", strerror(errno)); exit(1); } else if (ready == 0) { continue; } else { printf("S: oh finally you have contacted me!\n"); for(i = 0; i < (info->max_fd+1); i++) { if(FD_ISSET(i, &readset)) //this is where problem begins { printf("S: %i is set\n", i); printf("S: we talking about socket %i son\n", i); // i = 4 num_bytes = recv(i, &msg, MAX_MSG_BYTE, 0); printf("S: number of bytes recieved in socket %i is %i\n", i, num_bytes); // prints out i = 0 what?? if (num_bytes == 0) { printf("S: socket has been closed\n"); break; } else if (num_bytes == -1) { printf("S: ERROR recv: %d %s \n", i, strerror(errno)); continue; } else { handle_request(arg, &msg); printf("S: msg says %s\n", msg->_payload); } } // if (FD_ISSET(i, &readset) else printf("S: %i is not set\n", i); } // for (i = 0; i < maxfd+1; i++) to check sockets for msg } // if (ready == -1) info->read_set = info->copy_set; printf("S: copied\n"); } the problem I have is that in read_set, 0~3 aren't set and 4 is. That is fine. But when i call recv(), i suddently becomes 0. Why is that? It doesn't make sense to me why recv() would take an socket file descriptor number and modify to another number. Is that normal? Am I missing something? S: 0 is not set S: 1 is not set S: 2 is not set S: 3 is not set S: 4 is set S: we talking about socket 4 son S: i is strangely or unstrangely 0 S: number of bytes recieved in socket 0 is 40 That's what it prints out.

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  • How do I achieve a 'select or insert' task using LINQ to EF?

    - by ProfK
    I have an import process with regions, locations, and shifts, where a Shift object has a Location property, and a Location object has a Region property. If a region name does not exist, I create the region, and like wise a location. I thought I could neatly encapsulate the 'Select if exists, or create' logic into helper classes for Region and Location, but if I use local data contexts in these classes I run into attach and detach overheads that become unpleasent. If I include a data context dependency in these classes, my encapsulation feels broken. What is the ideal method for achieving this, or where is the ideal place to place this functionality? In my example I have leaned heavily on the foreign key crutch provided with .NET 4.0, and simply avoided using entities in favour of direct foreign key values, but this is starting to smell. Example: public partial class ActivationLocation { public static int GetOrCreate(int regionId, string name) { using (var ents = new PvmmsEntities()) { var loc = ents.ActivationLocations.FirstOrDefault(x => x.RegionId == regionId && x.Name == name); if (loc == null) { loc = new ActivationLocation {RegionId = regionId, Name = name}; ents.AddToActivationLocations(loc); ents.SaveChanges(SaveOptions.AcceptAllChangesAfterSave); } return loc.LocationId; } } }

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  • Trapping Error Status in MSBuild

    - by Ruben Bartelink
    As part of some build automation of running xUnit.net tests with MSBuild, I'm running into a case where I need to loop over a batch of items. Inside the loop, I need to detect whether an iteration failed, but I want to continue executing regardless. Then after the batched bit, I need to know whether one or more errors have occurred in order to report the outcome to TeamBuild. IOW, in pseudocode: Task Name=RunTests CreateItems ForEach item CallTarget Target=RunTest ContinueOnError=true CombineNUnitResults Report success/failure Task Name=RunTest XUnit item I'm hoping this can be achieved without a custom task (or hacking the xunit.net MSBuild task as Jonne did). (But willing to use MSBuild Community or Sdc tasks) And @BradWilson: I this is isnt possible to do cleanly, I'll be looking for Jonne's change a la the NUnit task to also make it into the xunit task See also: http://stackoverflow.com/questions/517560/how-do-i-get-team-build-to-show-test-results-and-coverage-for-xunit-net-test-suit

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  • REST API Help in Rails

    - by dannymcc
    Hi Everyone, I am trying to get some information posted using our accountancy package (FreeAgentCentral) using their API via a GEM. http://github.com/aaronrussell/freeagent_api/ I have the following code to get it working (supposedly): Kase Controller def create @kase = Kase.new(params[:kase]) @company = Company.find(params[:kase][:company_id]) @kase = @company.kases.create!(params[:kase]) respond_to do |format| if @kase.save UserMailer.deliver_makeakase("[email protected]", "Highrise", @kase) @kase.create_freeagent_project(current_user) #flash[:notice] = 'Case was successfully created.' flash[:notice] = fading_flash_message("Case was successfully created & sent to Highrise.", 5) format.html { redirect_to(@kase) } format.xml { render :xml => @kase, :status => :created, :location => @kase } else format.html { render :action => "new" } format.xml { render :xml => @kase.errors, :status => :unprocessable_entity } end end end To save you looking through, the important part is: @kase.create_freeagent_project(current_user) Kase Model # FreeAgent API Project Create # Required attribues # :contact_id # :name # :payment_term_in_days # :billing_basis # must be 1, 7, 7.5, or 8 # :budget_units # must be Hours, Days, or Monetary # :status # must be Active or Completed def create_freeagent_project(current_user) p = Freeagent::Project.create( :contact_id => 0, :name => "#{jobno} - #{highrisesubject}", :payment_terms_in_days => 5, :billing_basis => 1, :budget_units => 'Hours', :status => 'Active' ) user = Freeagent::User.find_by_email(current_user.email) Freeagent::Timeslip.create( :project_id => p.id, :user_id => user.id, :hours => 1, :new_task => 'Setup', :dated_on => Time.now ) end lib/freeagent_api.rb require 'rubygems' gem 'activeresource', '< 3.0.0.beta1' require 'active_resource' module Freeagent class << self def authenticate(options) Base.authenticate(options) end end class Error < StandardError; end class Base < ActiveResource::Base def self.authenticate(options) self.site = "https://#{options[:domain]}" self.user = options[:username] self.password = options[:password] end end # Company class Company def self.invoice_timeline InvoiceTimeline.find :all, :from => '/company/invoice_timeline.xml' end def self.tax_timeline TaxTimeline.find :all, :from => '/company/tax_timeline.xml' end end class InvoiceTimeline < Base self.prefix = '/company/' end class TaxTimeline < Base self.prefix = '/company/' end # Contacts class Contact < Base end # Projects class Project < Base def invoices Invoice.find :all, :from => "/projects/#{id}/invoices.xml" end def timeslips Timeslip.find :all, :from => "/projects/#{id}/timeslips.xml" end end # Tasks - Complete class Task < Base self.prefix = '/projects/:project_id/' end # Invoices - Complete class Invoice < Base def mark_as_draft connection.put("/invoices/#{id}/mark_as_draft.xml", encode, self.class.headers).tap do |response| load_attributes_from_response(response) end end def mark_as_sent connection.put("/invoices/#{id}/mark_as_sent.xml", encode, self.class.headers).tap do |response| load_attributes_from_response(response) end end def mark_as_cancelled connection.put("/invoices/#{id}/mark_as_cancelled.xml", encode, self.class.headers).tap do |response| load_attributes_from_response(response) end end end # Invoice items - Complete class InvoiceItem < Base self.prefix = '/invoices/:invoice_id/' end # Timeslips class Timeslip < Base def self.find(*arguments) scope = arguments.slice!(0) options = arguments.slice!(0) || {} if options[:params] && options[:params][:from] && options[:params][:to] options[:params][:view] = options[:params][:from]+'_'+options[:params][:to] options[:params].delete(:from) options[:params].delete(:to) end case scope when :all then find_every(options) when :first then find_every(options).first when :last then find_every(options).last when :one then find_one(options) else find_single(scope, options) end end end # Users class User < Base self.prefix = '/company/' def self.find_by_email(email) users = User.find :all users.each do |u| u.email == email ? (return u) : next end raise Error, "No user matches that email!" end end end config/initializers/freeagent.rb Freeagent.authenticate({ :domain => 'XXXXX.freeagentcentral.com', :username => '[email protected]', :password => 'XXXXXX' }) The above render the following error when trying to create a new Case and send the details to FreeAgent: ActiveResource::ResourceNotFound in KasesController#create Failed with 404 Not Found and ActiveResource::ResourceNotFound (Failed with 404 Not Found): app/models/kase.rb:56:in `create_freeagent_project' app/controllers/kases_controller.rb:96:in `create' app/controllers/kases_controller.rb:93:in `create' Rendered rescues/_trace (176.5ms) Rendered rescues/_request_and_response (1.1ms) Rendering rescues/layout (internal_server_error) If anyone can shed any light on this problem it would be greatly appreciated! Thanks, Danny

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  • How to start and stop jboss server using Ant task ?

    - by Purushotham
    I need to stop, deploy my ear file and start Jboss server using the Ant tasks. I am able to compile, build and deploy my J2EE application as an ear file into the JBoss server successfully using Ant tasks. We can see the redeployment of my application in the jboss console. I want to stop the server before deployment and start the server. Is there any way to do this ?

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  • Is there a rake task for advancing or retreating your schema version by exactly one?

    - by user30997
    Back when migration version numbers were simply incremented as you created migrations, it was easy enough to do: rake migrate VERSION=097 rake migrate VERSION=098 rake migrate VERSION=099 rake migrate VERSION=100 ...but we now have migration numbers that are something like YYYYMMDDtimeofday. Not that this is a bad thing - it keeps the migration version collisions to a minimum - but when I have 50 migrations and want to step through them one-at-a-time, it is a hassle: rake migrate VERSION=20090129215142 rake migrate VERSION=20090129219783 ...etc. I have to have a list of all the migrations open in front of me, typing out the version numbers to advance by one. Is there anything that would have an easier syntax, like: rake migrate VERSION=NEXT or rake migrate VERSION=PREV ?

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  • How to show an animated spinner while a background task is processing in nested rails model using aj

    - by Globalkeith
    My specific example is highly complex, so I will use the example shown by Ryan from Railscasts to discuss this: http://railscasts.com/episodes/197-nested-model-form-part-2 Background I have a form, let's say "Survey", which contains an arbitrary number of "Questions". Senario Give i am on the "Edit Survey" page. I would like to add a button to each "Question" field which calls a remote_function, which in turn queue's up a delayed_job to execute some processing on the "Question". To give feedback to the user, i would like to disable the button, and show an animated spinner, which remains until the delayed_job has processed the "Question". Hint - I can add methods to the "Question" model to indicate the status of the delayed_job. So, with best practices in mind, what is the best way to achieve this?

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  • where should we send notification for updating many views?

    - by Thanh-Cong Vo
    Hi all, I want to ask about software design. I have a task, the view controller handles UI event for calling a model manger to perform that task. After finishing, the model manager will callback to update the view. There have also other views who care about that task, and also want to update its own view when that task is finished. So I register a Notification for that task in each views. The problem is defining where should I send Notification, in Model manager or in the View who handles event and receives the callback from Model manager? What is better design? Shoud the model care about send this "common" task, or shoud the view? Thanks

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  • database design in google app engine

    - by iamgopal
    hi , i am designing a simple project based to do list. the idea is to define tasks under project ( no workflow - just "task is completed" or not is required. ) in a hirarchial way. i.e. each task has multiple task and that task may have other multiple task. a project can be said to be completed if all task under that project are completed. , i tought of using refrenceproeperty to create hirarchy , but could not figure out easy way ( which do not take more than 30 seconds to find all the children of a project and check weather it is completed or not ) . to detect if project is complete or not. how to design database for such job ? and also , if i need to copy the project in order to define another project , how to copy hierarchical data ?

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  • Using implicit conversion as a substitute for multiple inheritance in .NET

    - by Daniel Plaisted
    I have a situation where I would like to have objects of a certain type be able to be used as two different types. If one of the "base" types was an interface this wouldn't be an issue, but in my case it is preferable that they both be concrete types. I am considering adding copies of the methods and properties of one of the base types to the derived type, and adding an implicit conversion from the derived type to that base type. Then users will be able treat the derived type as the base type by using the duplicated methods directly, by assigning it to a variable of the base type, or by passing it to a method that takes the base type. It seems like this solution will fit my needs well, but am I missing anything? Is there a situation where this won't work, or where it is likely to add confusion instead of simplicity when using the API?

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  • Table-level diff and sync procedure for T-SQL

    - by Ville Koskinen
    I'm interested in T-SQL source code for synchronizing a table (or perhaps a subset of it) with data from another similar table. The two tables could contain any variables, for example I could have base table source table ========== ============ id val id val ---------- ------------ 0 1 0 3 1 2 1 2 2 3 3 4 or base table source table =================== ================== key val1 val2 key val1 val2 ------------------- ------------------ A 1 0 A 1 1 B 2 1 C 2 2 C 3 3 E 4 0 or any two tables containing similar columns with similar names. I'd like to be able to check that the two tables have matching columns: the source table has exactly the same columns as the base table and the datatypes match make a diff from the base table to the source table do the necessary updates, deletes and inserts to change the data in the base table to correspond the source table optionally limit the diff to a subset of the base table, preferrably with a stored procedure. Has anyone written a stored proc for this or could you point to a source?

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  • How to use less memory while running a task in Symfony 1.4?

    - by Guillaume Flandre
    I'm using Symfony 1.4 and Doctrine. So far I had no problem running tasks with Symfony. But now that I have to import a pretty big amount of data and save them in the database, I get the infamous "Fatal Error: Allowed memory size of XXXX bytes exhausted" During this import I'm only creating new objects, setting a few fields and saving them. I'm pretty sure it has something to do with the number of objects I'm creating when saving data. Unsetting those objects doesn't do anything though. Are there any best practices to limit memory usage in Symfony?

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  • Programming graphics and sound on PC - Total newbie questions, and lots of them!

    - by Russel
    Hello, This isn't exactly specifically a programming question (or is it?) but I was wondering: How are graphics and sound processed from code and output by the PC? My guess for graphics: There is some reserved memory space somewhere that holds exactly enough room for a frame of graphics output for your monitor. IE: 800 x 600, 24 bit color mode == 800x600x3 = ~1.4MB memory space Between each refresh, the program writes video data to this space. This action is completed before the monitor refresh. Assume a simple 2D game: the graphics data is stored in machine code as many bytes representing color values. Depending on what the program(s) being run instruct the PC, the processor reads the appropriate data and writes it to the memory space. When it is time for the monitor to refresh, it reads from each memory space byte-for-byte and activates hardware depending on those values for each color element of each pixel. All of this of course happens crazy-fast, and repeats x times a second, x being the monitor's refresh rate. I've simplified my own likely-incorrect explanation by avoiding talk of double buffering, etc Here are my questions: a) How close is the above guess (the three steps)? b) How could one incorporate graphics in pure C++ code? I assume the practical thing that everyone does is use a graphics library (SDL, OpenGL, etc), but, for example, how do these libraries accomplish what they do? Would manual inclusion of graphics in pure C++ code (say, a 2D spite) involve creating a two-dimensional array of bit values (or three dimensional to include multiple RGB values per pixel)? Is this how it would be done waaay back in the day? c) Also, continuing from above, do libraries such as SDL etc that use bitmaps actual just build the bitmap/etc files into machine code of the executable and use them as though they were build in the same matter mentioned in question b above? d) In my hypothetical step 3 above, is there any registers involved? Like, could you write some byte value to some register to output a single color of one byte on the screen? Or is it purely dedicated memory space (=RAM) + hardware interaction? e) Finally, how is all of this done for sound? (I have no idea :) )

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  • Does a recursive Ant task exist to recover properties from external file?

    - by Julia2020
    Hi, I ve got a problem in getting properties with ant from a properties file. With a simple target like this in my build.xml, i'd like to get at least two properties path1 and path2. I'd like to have a generic target to get this two properties.... in order to avoid modifying the build.xml (just adding a new prop) Any suggestions? Thanks in advance ! build.xml : <target name="TEST" description="test ant"> <property file="dependencies.properties"/> <svn> <export srcUrl="${path.prop}" destPath="${workspace}/rep/" /> </svn> </target> dependencies.properties : path1.prop = /path/to/src1 path2.prop = /path/to/src2

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  • Make Ant's delete task fail when a directory exists and is not deleted but not when it doesn't exist

    - by Tim Visher
    I have tho following clean function in my build script and I'd like to know how I can improve it. <target name="clean" description="Clean output directories."> <!-- Must not fail on error because it fails if directories don't exist. Is there really no better way to do this? --> <delete includeEmptyDirs="true" failonerror="false"> <fileset dir="${main.build.directory}" /> <fileset dir="dist" /> <fileset dir="${documentation.build.directory}" /> <fileset dir="/build-testing" /> </delete> </target> Specifically regarding my comment, I'm unhappy with the fact that I can't run this on a fresh box because the directory structure hasn't been set up yet by the other targets. We run the build in such a way that it entirely recreates the structures necessary for testing and deployment every time to avoid stale class files and such. With the way that delete currently is set up, a failure to delete a file does not fail the build and I'd like it to. I don't want it to fail the build if the file doesn't exist though. If it doesn't exist then what I'm asking it to do has already happened. Thoughts?

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  • Inheriting and static members

    - by Bruce
    Here is my code - #include <iostream> #include <conio.h> using namespace std; class Base { public: int a; }; //int Base::a = 5; class Derived : public Base { public: int static a; }; int main() { Derived d; cout<<d.a; getch(); return 0; } I get a linker error here. But when I do it the other way round - class Base { public: int static a; }; int Base::a = 5; class Derived : public Base { public: int a; }; I get no error. Can someone please explain what is happening here.

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  • Is there a way to achieve covariance of generic types in C# 3.0?

    - by nullDev
    This has been introduced in C# 4.0, but is there a way to achieve this in c# 3.0? For e.g., consider the following code: class Base { } class Derived1 : Base { } class Derived2 : Base { } class User<T> where T : Base { } class User1 : User<Derived1> { } Now, I would like to have a list of User<T>, in which I can store User<Derived1> as well as User<Derived2>, but the following code fails to compile in C# 3.0: List<User<Base>> users = new List<User<Base>>(); users.Add(new User1()); Any ideas?

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  • Optimizing tasks to reduce CPU in a trading application

    - by Joel
    Hello, I have designed a trading application that handles customers stocks investment portfolio. I am using two datastore kinds: Stocks - Contains unique stock name and its daily percent change. UserTransactions - Contains information regarding a specific purchase of a stock made by a user : the value of the purchase along with a reference to Stock for the current purchase. db.Model python modules: class Stocks (db.Model): stockname = db.StringProperty(multiline=True) dailyPercentChange=db.FloatProperty(default=1.0) class UserTransactions (db.Model): buyer = db.UserProperty() value=db.FloatProperty() stockref = db.ReferenceProperty(Stocks) Once an hour I need to update the database: update the daily percent change in Stocks and then update the value of all entities in UserTransactions that refer to that stock. The following python module iterates over all the stocks, update the dailyPercentChange property, and invoke a task to go over all UserTransactions entities which refer to the stock and update their value: Stocks.py # Iterate over all stocks in datastore for stock in Stocks.all(): # update daily percent change in datastore db.run_in_transaction(updateStockTxn, stock.key()) # create a task to update all user transactions entities referring to this stock taskqueue.add(url='/task', params={'stock_key': str(stock.key(), 'value' : self.request.get ('some_val_for_stock') }) def updateStockTxn(stock_key): #fetch the stock again - necessary to avoid concurrency updates stock = db.get(stock_key) stock.dailyPercentChange= data.get('some_val_for_stock') # I get this value from outside ... some more calculations here ... stock.put() Task.py (/task) # Amount of transaction per task amountPerCall=10 stock=db.get(self.request.get("stock_key")) # Get all user transactions which point to current stock user_transaction_query=stock.usertransactions_set cursor=self.request.get("cursor") if cursor: user_transaction_query.with_cursor(cursor) # Spawn another task if more than 10 transactions are in datastore transactions = user_transaction_query.fetch(amountPerCall) if len(transactions)==amountPerCall: taskqueue.add(url='/task', params={'stock_key': str(stock.key(), 'value' : self.request.get ('some_val_for_stock'), 'cursor': user_transaction_query.cursor() }) # Iterate over all transaction pointing to stock and update their value for transaction in transactions: db.run_in_transaction(updateUserTransactionTxn, transaction.key()) def updateUserTransactionTxn(transaction_key): #fetch the transaction again - necessary to avoid concurrency updates transaction = db.get(transaction_key) transaction.value= transaction.value* self.request.get ('some_val_for_stock') db.put(transaction) The problem: Currently the system works great, but the problem is that it is not scaling well… I have around 100 Stocks with 300 User Transactions, and I run the update every hour. In the dashboard, I see that the task.py takes around 65% of the CPU (Stock.py takes around 20%-30%) and I am using almost all of the 6.5 free CPU hours given to me by app engine. I have no problem to enable billing and pay for additional CPU, but the problem is the scaling of the system… Using 6.5 CPU hours for 100 stocks is very poor. I was wondering, given the requirements of the system as mentioned above, if there is a better and more efficient implementation (or just a small change that can help with the current implemntation) than the one presented here. Thanks!! Joel

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