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  • Stretch array (Numpy, Python)

    - by Snej
    I have a numpy array [1,2,3,4,5,6,7,8,9,10,11,12,13,14] and want to have an array structured like [[1,2,3,4], [2,3,4,5], [3,4,5,6], ..., [11,12,13,14]]. Sure this is possible by looping over the large array and adding arrays of length four to the new array, but I'm curious if there is some secret 'magic' Python method doing just this :)

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  • is there a size limit to a text file?

    - by chicane
    HI All I am creating a log file for our website which will log every log-in by all the users to our orders area. I wish to know if you think its good to enter this log info in just one single file or should this be split up once the log file hits a certain size? My concern is that this file will get rather large over time, but im not certain of the size limit of a text file? thank you

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  • Publishing selection in eclipse RCP

    - by Stuart
    I'm writing an RCP application plug-in. I want to make a set of objects the global selection from a IHandler but this can be triggered from other views out of my control - it is possible that these do not have an ISelectionProvider. Is it possible to publish a selection to the eclipse selection service without going through some view site?

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  • Optimal size for Database partitions

    - by Adrian Mouat
    Hi all, I am creating a very simple, very large Postgresql database. The database will have around 10 billion rows, which means I am looking at partitioning it into several tables. However, I can't find any information on how many partitions we should break it into. I don't know what type of queries to expect as of yet, so it won't be possible to come up with a perfect partitioning scheme, but are there any rules of thumb for partition size? Cheers, Adrian.

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  • Odd behavior in Django Form (readonly field/widget)

    - by jamida
    I'm having a problem with a test app I'm writing to verify some Django functionality. The test app is a small "grade book" application that is currently using Alex Gaynor's readonly field functionality http://lazypython.blogspot.com/2008/12/building-read-only-field-in-django.html There are 2 problems which may be related. First, when I flop the comment on these 2 lines below: # myform = GradeForm(data=request.POST, instance=mygrade) myform = GradeROForm(data=request.POST, instance=mygrade) it works like I expect, except of course that the student field is changeable. When the comments are the shown way, the "studentId" field is displayed as a number (not the name, problem 1) and when I hit submit I get an error saying that studentId needs to be a Student instance. I'm at a loss as to how to fix this. I'm not wedded to Alex Gaynor's code. ANY code will work. I'm relatively new to both Python and Django, so the hints I've seen on websites that say "making a read-only field is easy" are still beyond me. // models.py class Student(models.Model): name = models.CharField(max_length=50) parent = models.CharField(max_length=50) def __unicode__(self): return self.name class Grade(models.Model): studentId = models.ForeignKey(Student) finalGrade = models.CharField(max_length=3) # testbed.grades.readonly is alex gaynor's code from testbed.grades.readonly import ReadOnlyField class GradeROForm(ModelForm): studentId = ReadOnlyField() class Meta: model=Grade class GradeForm(ModelForm): class Meta: model=Grade // views.py def modifyGrade(request,student): student = Student.objects.get(name=student) mygrade = Grade.objects.get(studentId=student) if request.method == "POST": # myform = GradeForm(data=request.POST, instance=mygrade) myform = GradeROForm(data=request.POST, instance=mygrade) if myform.is_valid(): grade = myform.save() info = "successfully updated %s" % grade.studentId else: # myform=GradeForm(instance=mygrade) myform=GradeROForm(instance=mygrade) return render_to_response('grades/modifyGrade.html',locals()) // template <p>{{ info }}</p> <form method="POST" action=""> <table> {{ myform.as_table }} </table> <input type="submit" value="Submit"> </form> // Alex Gaynor's code from django import forms from django.utils.html import escape from django.utils.safestring import mark_safe from django.forms.util import flatatt class ReadOnlyWidget(forms.Widget): def render(self, name, value, attrs): final_attrs = self.build_attrs(attrs, name=name) if hasattr(self, 'initial'): value = self.initial return mark_safe("<span %s>%s</span>" % (flatatt(final_attrs), escape(value) or '')) def _has_changed(self, initial, data): return False class ReadOnlyField(forms.FileField): widget = ReadOnlyWidget def __init__(self, widget=None, label=None, initial=None, help_text=None): forms.Field.__init__(self, label=label, initial=initial, help_text=help_text, widget=widget) def clean(self, value, initial): self.widget.initial = initial return initial

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  • Is there a list of common object that implement IDisposable for the using statement?

    - by SkippyFire
    I was wondering if there was some sort of cheat sheet for which objects go well with the using statement... SQLConnection, MemoryStream, etc. Taking it one step further, it would be great to even show the other "pieces of the puzzle", like how you should actually call connection.Close() before the closing using statement bracket. Anything like that exist? If not, maybe we should make one.

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  • Using a custom form in a modelformset factory?

    - by jamida
    I'd like to be able to use a customized form in a modelformset_factory. For example: models.py class Author(models.Model): name = models.CharField() address = models.CharField() class AuthorForm(ModelForm): class Meta: model = Author views.py def test_render(request): myModelFormset = modelformset_factory(Author) items = Author.objects.all() formsetInstance = myModelFormset(queryset = items) return render_to_response('template',locals()) The above code works just fine, but note I'm NOT using AuthorForm. The question is how can I get the modelformset_factory to use the AuthorForm (which I plan to customize later) instead of making a default Author form?

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  • Mongoid or MongoMapper?

    - by PanosJee
    I have tried MongoMapper and it is feature complete (offering almost all AR functionality) but i was not very happy with the performance when using large datasets. Has anyone compared with Mongoid? Any performance gains ?

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  • Quickest way to find the oldest file in a directory using Delphi

    - by Pieter van Wyk
    HI We have a large number of remote computers that capture video onto disk drives. Each camera has it's own unique directory and there can be up to 16 directories on any one disk. I'm trying to locate the oldest video file on the disk but using FindFirst/FindNext to compare the File Creation DateTime takes forever. Does anybody know of a more efficient way of finding the oldest file in a directory? We remotely connect to the pc's from a central HO location. Regards, Pieter

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  • What is the fastest cyclic synchronization in Java (ExecutorService vs. CyclicBarrier vs. X)?

    - by Alex Dunlop
    Which Java synchronization construct is likely to provide the best performance for a concurrent, iterative processing scenario with a fixed number of threads like the one outlined below? After experimenting on my own for a while (using ExecutorService and CyclicBarrier) and being somewhat surprised by the results, I would be grateful for some expert advice and maybe some new ideas. Existing questions here do not seem to focus primarily on performance, hence this new one. Thanks in advance! The core of the app is a simple iterative data processing algorithm, parallelized to the spread the computational load across 8 cores on a Mac Pro, running OS X 10.6 and Java 1.6.0_07. The data to be processed is split into 8 blocks and each block is fed to a Runnable to be executed by one of a fixed number of threads. Parallelizing the algorithm was fairly straightforward, and it functionally works as desired, but its performance is not yet what I think it could be. The app seems to spend a lot of time in system calls synchronizing, so after some profiling I wonder whether I selected the most appropriate synchronization mechanism(s). A key requirement of the algorithm is that it needs to proceed in stages, so the threads need to sync up at the end of each stage. The main thread prepares the work (very low overhead), passes it to the threads, lets them work on it, then proceeds when all threads are done, rearranges the work (again very low overhead) and repeats the cycle. The machine is dedicated to this task, Garbage Collection is minimized by using per-thread pools of pre-allocated items, and the number of threads can be fixed (no incoming requests or the like, just one thread per CPU core). V1 - ExecutorService My first implementation used an ExecutorService with 8 worker threads. The program creates 8 tasks holding the work and then lets them work on it, roughly like this: // create one thread per CPU executorService = Executors.newFixedThreadPool( 8 ); ... // now process data in cycles while( ...) { // package data into 8 work items ... // create one Callable task per work item ... // submit the Callables to the worker threads executorService.invokeAll( taskList ); } This works well functionally (it does what it should), and for very large work items indeed all 8 CPUs become highly loaded, as much as the processing algorithm would be expected to allow (some work items will finish faster than others, then idle). However, as the work items become smaller (and this is not really under the program's control), the user CPU load shrinks dramatically: blocksize | system | user | cycles/sec 256k 1.8% 85% 1.30 64k 2.5% 77% 5.6 16k 4% 64% 22.5 4096 8% 56% 86 1024 13% 38% 227 256 17% 19% 420 64 19% 17% 948 16 19% 13% 1626 Legend: - block size = size of the work item (= computational steps) - system = system load, as shown in OS X Activity Monitor (red bar) - user = user load, as shown in OS X Activity Monitor (green bar) - cycles/sec = iterations through the main while loop, more is better The primary area of concern here is the high percentage of time spent in the system, which appears to be driven by thread synchronization calls. As expected, for smaller work items, ExecutorService.invokeAll() will require relatively more effort to sync up the threads versus the amount of work being performed in each thread. But since ExecutorService is more generic than it would need to be for this use case (it can queue tasks for threads if there are more tasks than cores), I though maybe there would be a leaner synchronization construct. V2 - CyclicBarrier The next implementation used a CyclicBarrier to sync up the threads before receiving work and after completing it, roughly as follows: main() { // create the barrier barrier = new CyclicBarrier( 8 + 1 ); // create Runable for thread, tell it about the barrier Runnable task = new WorkerThreadRunnable( barrier ); // start the threads for( int i = 0; i < 8; i++ ) { // create one thread per core new Thread( task ).start(); } while( ... ) { // tell threads about the work ... // N threads + this will call await(), then system proceeds barrier.await(); // ... now worker threads work on the work... // wait for worker threads to finish barrier.await(); } } class WorkerThreadRunnable implements Runnable { CyclicBarrier barrier; WorkerThreadRunnable( CyclicBarrier barrier ) { this.barrier = barrier; } public void run() { while( true ) { // wait for work barrier.await(); // do the work ... // wait for everyone else to finish barrier.await(); } } } Again, this works well functionally (it does what it should), and for very large work items indeed all 8 CPUs become highly loaded, as before. However, as the work items become smaller, the load still shrinks dramatically: blocksize | system | user | cycles/sec 256k 1.9% 85% 1.30 64k 2.7% 78% 6.1 16k 5.5% 52% 25 4096 9% 29% 64 1024 11% 15% 117 256 12% 8% 169 64 12% 6.5% 285 16 12% 6% 377 For large work items, synchronization is negligible and the performance is identical to V1. But unexpectedly, the results of the (highly specialized) CyclicBarrier seem MUCH WORSE than those for the (generic) ExecutorService: throughput (cycles/sec) is only about 1/4th of V1. A preliminary conclusion would be that even though this seems to be the advertised ideal use case for CyclicBarrier, it performs much worse than the generic ExecutorService. V3 - Wait/Notify + CyclicBarrier It seemed worth a try to replace the first cyclic barrier await() with a simple wait/notify mechanism: main() { // create the barrier // create Runable for thread, tell it about the barrier // start the threads while( ... ) { // tell threads about the work // for each: workerThreadRunnable.setWorkItem( ... ); // ... now worker threads work on the work... // wait for worker threads to finish barrier.await(); } } class WorkerThreadRunnable implements Runnable { CyclicBarrier barrier; @NotNull volatile private Callable<Integer> workItem; WorkerThreadRunnable( CyclicBarrier barrier ) { this.barrier = barrier; this.workItem = NO_WORK; } final protected void setWorkItem( @NotNull final Callable<Integer> callable ) { synchronized( this ) { workItem = callable; notify(); } } public void run() { while( true ) { // wait for work while( true ) { synchronized( this ) { if( workItem != NO_WORK ) break; try { wait(); } catch( InterruptedException e ) { e.printStackTrace(); } } } // do the work ... // wait for everyone else to finish barrier.await(); } } } Again, this works well functionally (it does what it should). blocksize | system | user | cycles/sec 256k 1.9% 85% 1.30 64k 2.4% 80% 6.3 16k 4.6% 60% 30.1 4096 8.6% 41% 98.5 1024 12% 23% 202 256 14% 11.6% 299 64 14% 10.0% 518 16 14.8% 8.7% 679 The throughput for small work items is still much worse than that of the ExecutorService, but about 2x that of the CyclicBarrier. Eliminating one CyclicBarrier eliminates half of the gap. V4 - Busy wait instead of wait/notify Since this app is the primary one running on the system and the cores idle anyway if they're not busy with a work item, why not try a busy wait for work items in each thread, even if that spins the CPU needlessly. The worker thread code changes as follows: class WorkerThreadRunnable implements Runnable { // as before final protected void setWorkItem( @NotNull final Callable<Integer> callable ) { workItem = callable; } public void run() { while( true ) { // busy-wait for work while( true ) { if( workItem != NO_WORK ) break; } // do the work ... // wait for everyone else to finish barrier.await(); } } } Also works well functionally (it does what it should). blocksize | system | user | cycles/sec 256k 1.9% 85% 1.30 64k 2.2% 81% 6.3 16k 4.2% 62% 33 4096 7.5% 40% 107 1024 10.4% 23% 210 256 12.0% 12.0% 310 64 11.9% 10.2% 550 16 12.2% 8.6% 741 For small work items, this increases throughput by a further 10% over the CyclicBarrier + wait/notify variant, which is not insignificant. But it is still much lower-throughput than V1 with the ExecutorService. V5 - ? So what is the best synchronization mechanism for such a (presumably not uncommon) problem? I am weary of writing my own sync mechanism to completely replace ExecutorService (assuming that it is too generic and there has to be something that can still be taken out to make it more efficient). It is not my area of expertise and I'm concerned that I'd spend a lot of time debugging it (since I'm not even sure my wait/notify and busy wait variants are correct) for uncertain gain. Any advice would be greatly appreciated.

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  • Is that possible using "setAutoresizingMask" to make the view autoresizing after hiding/showing navi

    - by Mickey Shine
    I am doing this with the following: [[self navigationController] setNavigationBarHidden:YES animated:YES]; and also I didn't use IB to create view objects. But my view did not auto-resize after hiding navigation bar(there was a blank area where the navigation bar used to be) I am wondering if I could make it auto-resize only by "setAutoresizingMask", or do I have to use some hand-writing animation stuff?

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  • Storing a set of criteria in another table

    - by bendataclear
    I have a large table with sales data, useful data below: RowID Date Customer Salesperson Product_Type Manufacturer Quantity Value 1 01-06-2004 James Ian Taps Tap Ltd 200 £850 2 02-06-2004 Apple Fran Hats Hats Inc 30 £350 3 04-06-2004 James Lawrence Pencils ABC Ltd 2000 £980 ... Many rows later... ... 185352 03-09-2012 Apple Ian Washers Tap Ltd 600 £80 I need to calculate a large set of targets from table containing values different types, target table is under my control and so far is like: TargetID Year Month Salesperson Target_Type Quantity 1 2012 7 Ian 1 6000 2 2012 8 James 2 2000 3 2012 9 Ian 2 6500 At present I am working out target types using a view of the first table which has a lot of extra columns: SELECT YEAR(Date) , MONTH(Date) , Salesperson , Quantity , CASE WHEN Manufacturer IN ('Tap Ltd','Hats Inc') AND Product_Type = 'Hats' THEN True ELSE False END AS IsType1 , CASE WHEN Manufacturer = 'Hats Inc' AND Product_Type IN ('Hats','Coats') THEN True ELSE False END AS IsType2 ... ... , CASE WHEN Manufacturer IN ('Tap Ltd','Hats Inc') AND Product_Type = 'Hats' THEN True ELSE False END AS IsType24 , CASE WHEN Manufacturer IN ('Tap Ltd','Hats Inc') AND Product_Type = 'Hats' THEN True ELSE False END AS IsType25 FROM SalesTable WHERE [some stuff here] This is horrible to read/debug and I hate it!! I've tried a few different ways of simplifying this but have been unable to get it to work. The closest I have come is to have a third table holding the definition of the types with the values for each field and the type number, this can be joined to the tables to give me the full values but I can't work out a way to cope with multiple values for each field. Finally the question: Is there a standard way this can be done or an easier/neater method other than one column for each type of target? I know this is a complex problem so if anything is unclear please let me know. Edit - What I need to get: At the very end of the process I need to have targets displayed with actual sales: Type Year Month Salesperson TargetQty ActualQty 2 2012 8 James 2000 2809 2 2012 9 Ian 6500 6251 Each row of the sales table could potentially satisfy 8 of the types. Some more points: I have 5 different columns that need to be defined against the targets (or set to NULL to include any value) I have between 30 and 40 different types that need to be defined, several of the columns could contain as many as 10 different values For point 2, if I am using a row for each permutation of values, 2 columns with 10 values each would give me 100 rows for each sales person for each month which is a lot but if this is the only way to define multiple values I will have to do this. Sorry if this makes no sense!

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  • using distinct in django query

    - by Hulk
    There is a column as designation in the defaults table,How to get the distinct designation values from defaults table In the below the distinct applies on the id field, this need to be on designation field def = defaults.objects.filter(name=sc).distinct() And can some one explain what is flat=true condition Thanks..

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  • Django RadioButtons with icons and not label?

    - by Asinox
    Hi guy's , i have an app that have 2 fields: company_name and logo, i'm displaying the companies like radiobutton in my Form from Model, but i want to show the logo company instead of the company label (company name) Any idea ? My forms: class RecargaForm(ModelForm): compania = forms.ModelChoiceField(queryset=Compania.objects.all(), initial=0 ,empty_label='None', widget=forms.RadioSelect()) class Meta: model = Recarga Thanks :)

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  • StyleCop SA1124 DoNotUseRegions is reasonable?

    - by Yanhua
    SA1124 DoNotUseRegions suggest that region should not be used anywhere. Is it really reasonable? I think region is a way to group relative code together and make large class easy to read, for example, if you generate interface method in for class, a region will be automatically inserted by visual studio. I would like to remove this rule while checking code style. May I know your ideal on this rule?

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  • How to modify code so that it adheres to the Law of Demeter

    - by guazz
    public class BigPerformance { public decimal Value {get;set;} } public class Performance { public BigPerformance BigPerf {get; set}; } public class Category { public Performance Perf {get;set; } } If I call: Category cat = new Cateogry(); cat.Perf.BigPerf.Value = 1.0; I assume this this breaks the LoD? If so, how do I remedy this if I have a large number of inner class Properties?

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  • Developer Capacity Planning

    - by Zaff
    What product or tool do you use to do Resource Capacity planning for your development team? Currently managing a large group and trying to provide visibility into my resource availability. I am creating this in MS project, but was curious if there was a better tool/solution based off your experience.

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  • Aletrnatives to MultiView in ASP.NET

    - by remdao
    Hi The website I'm building contains a large number of views which will be displayed on the same place but hidden or shown according to how the user navigates the menu. It gets quite messy in visual studios design view when you have a MultiView with 10 different views in it. I've already separated the content of each view in several user controls. But is there an alternative to MultiView?

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  • ArrayIndexOutOfBoundsException with custom Android Adapter for multiple views in ListView

    - by Dan Watling
    I am attempting to create a custom Adapter for my ListView since each item in the list can have a different view (a link, toggle, or radio group), but when I try to run the Activity that uses the ListView I receive an error and the app stops. The application is targeted for the Android 1.6 platform. The code: public class MenuListAdapter extends BaseAdapter { private static final String LOG_KEY = MenuListAdapter.class.getSimpleName(); protected List<MenuItem> list; protected Context ctx; protected LayoutInflater inflater; public MenuListAdapter(Context context, List<MenuItem> objects) { this.list = objects; this.ctx = context; this.inflater = (LayoutInflater)this.ctx.getSystemService(Context.LAYOUT_INFLATER_SERVICE); } @Override public View getView(int position, View convertView, ViewGroup parent) { Log.i(LOG_KEY, "Position: " + position + "; convertView = " + convertView + "; parent=" + parent); MenuItem item = list.get(position); Log.i(LOG_KEY, "Item=" + item ); if (convertView == null) { convertView = this.inflater.inflate(item.getLayout(), null); } return convertView; } @Override public boolean areAllItemsEnabled() { return false; } @Override public boolean isEnabled(int position) { return true; } @Override public int getCount() { return this.list.size(); } @Override public MenuItem getItem(int position) { return this.list.get(position); } @Override public long getItemId(int position) { return position; } @Override public int getItemViewType(int position) { Log.i(LOG_KEY, "getItemViewType: " + this.list.get(position).getLayout()); return this.list.get(position).getLayout(); } @Override public int getViewTypeCount() { Log.i(LOG_KEY, "getViewTypeCount: " + this.list.size()); return this.list.size(); } } The error I receive: java.lang.ArrayIndexOutOfBoundsException at android.widget.AbsListView$RecycleBin.addScrapView(AbsListView.java:3523) at android.widget.ListView.measureHeightOfChildren(ListView.java:1158) at android.widget.ListView.onMeasure(ListView.java:1060) at android.view.View.measure(View.java:7703) I do know that the application is returning from getView and everything seems in order. Any ideas on what could be causing this would be appreciated. Thanks, -Dan

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