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• What is microbenchmarking?

  - by polygenelubricants

  I've heard this term used, but I'm not entirely sure what it means, so: What DOES it mean and what DOESN'T it mean? What are some examples of what IS and ISN'T microbenchmarking? What are the dangers of microbenchmarking and how do you avoid it? (or is it a good thing?)

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• SQL Server - how to determine if indexes aren't being used?

  - by rwmnau

  I have a high-demand transactional database that I think is over-indexed. Originally, it didn't have any indexes at all, so adding some for common processes made a huge difference. However, over time, we've created indexes to speed up individual queries, and some of the most popular tables have 10-15 different indexes on them, and in some cases, the indexes are only slightly different from each other, or are the same columns in a different order. Is there a straightforward way to watch database activity and tell if any indexes are not hit anymore, or what their usage percentage is? I'm concerned that indexes were created to speed up either a single daily/weekly query, or even a query that's not being run anymore, but the index still has to be kept up to date every time the data changes. In the case of the high-traffic tables, that's a dozen times/second, and I want to eliminate indexes that are weighing down data updates while providing only marginal improvement.

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• Best way to get distinct values from large table

  - by derivation

  I have a db table with about 10 or so columns, two of which are month and year. The table has about 250k rows now, and we expect it to grow by about 100-150k records a month. A lot of queries involve the month and year column (ex, all records from march 2010), and so we frequently need to get the available month and year combinations (ie do we have records for april 2010?). A coworker thinks that we should have a separate table from our main one that only contains the months and years we have data for. We only add records to our main table once a month, so it would just be a small update on the end of our scripts to add the new entry to this second table. This second table would be queried whenever we need to find the available month/year entries on the first table. This solution feels kludgy to me and a violation of DRY. What do you think is the correct way of solving this problem? Is there a better way than having two tables?

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• Dynamic class_name for has_many relations

  - by vooD

  I'm trying to make has_many relation with dynamic class_name attribute class Category < ActiveRecord::Base has_many :ads, :class_name => ( lambda { return self.item_type } ) end or class Category < ActiveRecord::Base has_many :ads, :class_name => self.item_type end But i got errors: can't convert Proc into String or undefined method `item_type' for #<Class:0xb62c6c88> Thank you for any help!

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• Any method to denote object assignment?

  - by Droogans

  I've been studying magic methods in Python, and have been wondering if there's a way to outline the specific action of: a = MyClass(*params).method() versus: MyClass(*params).method() In the sense that, perhaps, I may want to return a list that has been split on the '\n' character, versus dumping the raw list into the variable a that keeps the '\n' intact. Is there a way to ask Python if its next action is about to return a value to a variable, and change action, if that's the case? I was thinking: class MyClass(object): def __init__(*params): self.end = self.method(*params) def __asgn__(self): return self.method(*params).split('\n') def __str__(self): """this is the fallback if __asgn__ is not called""" return self.method(*params)

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• F# why my recursion is faster than Seq.exists?

  - by user38397

  I am pretty new to F#. I'm trying to understand how I can get a fast code in F#. For this, I tried to write two methods (IsPrime1 and IsPrime2) for benchmarking. My code is: // Learn more about F# at http://fsharp.net open System open System.Diagnostics #light let isDivisible n d = n % d = 0 let IsPrime1 n = Array.init (n-2) ((+) 2) |> Array.exists (isDivisible n) |> not let rec hasDivisor n d = match d with | x when x < n -> (n % x = 0) || (hasDivisor n (d+1)) | _ -> false let IsPrime2 n = hasDivisor n 2 |> not let SumOfPrimes max = [|2..max|] |> Array.filter IsPrime1 |> Array.sum let maxVal = 20000 let s = new Stopwatch() s.Start() let valOfSum = SumOfPrimes maxVal s.Stop() Console.WriteLine valOfSum Console.WriteLine("IsPrime1: {0}", s.ElapsedMilliseconds) ////////////////////////////////// s.Reset() s.Start() let SumOfPrimes2 max = [|2..max|] |> Array.filter IsPrime2 |> Array.sum let valOfSum2 = SumOfPrimes2 maxVal s.Stop() Console.WriteLine valOfSum2 Console.WriteLine("IsPrime2: {0}", s.ElapsedMilliseconds) Console.ReadKey() IsPrime1 takes 760 ms while IsPrime2 takes 260ms for the same result. What's going on here and how I can make my code even faster?

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• SQL Server - Missing Indexes - What would use the index?

  - by BankZ

  I am using SQL Server 2008 and we are using the DMV's to find missing indexes. However, before I create the new index I am trying to figure out what proc/query is wanting that index. I want the most information I can get so I can make informed decision on my indexes. Sometimes the indexes SQL Server wants does not make sense to me. Does anyone know how I can figure out what wants it?

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• Makefile won't copy .o to obj/ and target to bin/ folders

  - by about blank

  I'm trying to write a Makefile which will copy its target and objects to bin/ and obj/ directories, respectively. Yet, when I try to run it I get the following error: nasm -f elf64 -g -F stabs main.asm -l spacelander.lst ld -o spacelander obj/main.o ld: cannot find obj/main.o: No such file or directory make: *** [spacelander] Error 1 Why is this happening? Update I noticed when I posted the error that it was due to white spacing errors. After taking care of those, I still get the new error I replaced with the old one I mentioned prior. What is this?? Update 2 Posted -d flag output below Makefile source. Source ASM := nasm ARGS := -f FMT := elf64 OPT := -g -F stabs SRC := main.asm OBJDIR := obj TARGETDIR := bin OBJ := $(addprefix $(OBJDIR)/,$(patsubst %.asm, %.o, $(wildcard *.asm))) TARGET := spacelander .PHONY: all clean all: $(OBJDIR) $(TARGET) $(OBJDIR): mkdir $(OBJDIR) $(OBJDIR)/%.o: $(SRC) $(ASM) $(ARGS) $(FMT) $(OPT) $(SRC) -l $(TARGET).lst $(TARGET): $(OBJ) ld -o $(TARGET) $(OBJ) clean: @rm -f $(TARGET) $(wildcard *.o) @rm -rf $(OBJDIR) make -d Output - NOTE: output is too many characters for body, thus is pastebinned http://pastebin.com/3bctGJxs

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• Does beginTransaction in Hibernate allocate a new DB connection?

  - by illscience

  Hi folks - Just wondering if beginning a new transaction in Hibernate actually allocates a connection to the DB? I'm concerned b/c our server begins a new transaction for each request received, even if that request doesn't interact with the DB. We're seeing DB connections as a major bottleneck, so I'm wondering if I should take the time narrow the scope of my transactions. Searched everywhere and haven't been able to find a good answer. The very simple code is here: SessionFactory sessionFactory = (SessionFactory) Context.getContext().getBean("sessionFactory"); sessionFactory.getCurrentSession().beginTransaction(); sessionFactory.getCurrentSession().setFlushMode(FlushMode.AUTO); thanks very much! a

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• Asp.net static object behaviour

  - by Circadian

  I have the following class as part of an asp.net application. public sealed class SomeClass { private static string appId = Guid.NewGuid().ToString(); public static ReadSomethingFromDb(){} public static WriteSomethingToDb(){} } There are more than one application instances in the same application pool, and they all access the same database. I want the operations performed by the above class to be uniquely tied to the instance that performed it, hence the use of the appId. So adding a record to the database would for example contain a name, address and appId. This has been simplified for discussion purposes. Assuming that I have two instances running at mysite.a and mysite.b the above class would generate two different guids. My problem is that mysite.a sometimes produces more than one guid, which is unexpected. Thank you in advance

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• syntax problem crating a method that returns an object (java)

  - by David

  I'm trying to create a method that will sum two timeO objects and return a new TimeO object called sum. Here is the relevant code snippet: public static TimeO add (TimeO t1, TimeO t2) { TimeO sum = new TimeO ; ... } When i try to compile it i get this error message: TimeO.java:15: '(' or '[' expected TimeO sum = new TimeO ; ^ 1 error i cant think of any reason why it would want me to open a set of parenthasies or brackets here but its possible that i dont' quite understand the syntax. Whats going wrong here?

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• Ruby on Rails - can't access datetime model object

  - by NomadicRiley

  I've created a model that has 3 string columns and a datetime. Everything is running in SQLite3 and I can view the records in my table just fine using Lita. I'm trying to display the values in a page (index action) using code like this: <% @details.each do |lifeCycle| % <%= debug(lifeCycle)% <%= lifeCycle.lifeCycleId % <%= lifeCycle.eventType % <%= debug(lifeCycle.timeId) % <% end % From the debug I get a result like this: --- !ruby/object:LifeCycle attributes: eventType: Order created_at: "2111359287.23037" timeId: "2455364.89983796" eventId: "98765" updated_at: "2111359287.23037" lifeCycleId: "12345" id: "1" attributes_cache: {} But whenever I try to access the event timeId - i' getting a nil value. This is true if i try to run debug on just that field debug(lifeCycle.timeId), or call a function on it. Is there something obvious I'm missing here?

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• Enums and inheritance

  - by devoured elysium

  I will use (again) the following class hierarchy: Event and all the following classes inherit from Event: SportEventType1 SportEventType2 SportEventType3 SportEventType4 I have originally designed the Event class like this: public abstract class Event { public abstract EventType EventType { get; } public DateTime Time { get; protected set; } protected Event(DateTime time) { Time = time; } } with EventType being defined as: public enum EventType { Sport1, Sport2, Sport3, Sport4 } The original idea would be that each SportEventTypeX class would set its correct EventType. Now that I think of it, I think this approach is totally incorrect for two reasons: If I want to later add a new SportEventType class I will have to modify the enum If I later decide to remove one SportEventType that I feel I won't use I'm also in big trouble with the enum. I have a class variable in the Event class that makes, afterall, assumptions about the kind of classes that will inherit from it, which kinda defeats the purpose of inheritance. How would you solve this kind of situation? Define in the Event class an abstract "Description" property, having each child class implement it? Having an Attribute(Annotation in Java!) set its Description variable instead? What would be the pros/cons of having a class variable instead of attribute/annotation in this case? Is there any other more elegant solution out there? Thanks

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• One UI for two business objects

  - by JC

  I have an order edit and quote edit screen that are very similar. I want to try to avoid code like this: if (order is Order) SetupScreenForOrder(); if (order is Quote) SetupScreenForQuote(); But maintaining two screens is not good either. If I create some common interface between a Quote and Order then how do you deal with fields like OrderNumber or QuoteDate? What's the best way to handle this?

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• Fastest way to read/store lots of multidimensional data? (Java)

  - by RemiX

  I have three questions about three nested loops: for (int x=0; x<400; x++) { for (int y=0; y<300; y++) { for (int z=0; z<400; z++) { // compute and store value } } } And I need to store all computed values. My standard approach would be to use a 3D-array: values[x][y][z] = 1; // test value but this turns out to be slow: it takes 192 ms to complete this loop, where a single int-assignment int value = 1; // test value takes only 66 ms. 1) Why is an array so relatively slow? 2) And why does it get even slower when I put this in the inner loop: values[z][y][x] = 1; // (notice x and z switched) This takes more than 4 seconds! 3) Most importantly: Can I use a data structure that is as quick as the assignment of a single integer, but can store as much data as the 3D-array?

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• Should I share UI for objects that use common fields?

  - by wb

  I have a parent class that holds all of the fields that are common between all device types. From that, I have a few derived classes that each hold their unique fields. Say I have device type "Switch" and "Transformer". Both derived classes only have 2-3 of their own unique fields. When doing the UI design (windows forms) in this case. Should I create two separate forms for each device type or create a user control with all fields that are shared among all devices? Thank you.

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• Start all tab's activities for pre-cache

  - by Pentium10

  I have a TabActivity with three tabs defined. The first tab is light-weight and renders in acceptable time. But the 2nd and 3rd tab, does need a couple of seconds to get visually rendered, after I click them. I would like to launch them, after I've loaded my first tab, in background for pre-cache. Once they are loaded, I can switch quickly between them. So I am wondering how can I launch the 2nd and 3rd tab. They are intents loaded in the view area.

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• How do I execute some code in a superclass after all the subclasses have been constructed?

  - by Thiado de Arruda

  Is there a way to do this in C#? I know that the subclass will call the superclass constructor before calling its own constructor, but what If I have some code on the superclass that should only be executed after all the subclasses constructors have been called?

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• Can I just release the top object (iPhone)?

  - by yar

  If I release the object that's holding a reference to the variable that I need to release, is that sufficient? Or must I release at every level of the containment hierarchy? I fear that my logic comes from working with a garbage collector for too long. For instance, I assigned to this property of a UIPickerView instance by hand instead of using IB @property(nonatomic, assign) id<UIPickerViewDelegate> delegate Since it's an assign property, I can't just release the reference after I assign it. When I finally release my UIPickerView instance, do I need to do this: [singlePicker.delegate release]; [singlePicker release]; or is the second line sufficient? Also: Are these assign properties the norm, or is that mostly for Interface Builder? I thought that retain properties were the normal thing to expect.

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• Using a string as an object reference

  - by user317362

  I currently have a Javascript function that uses a string to reference an object name and acces its properties. I'm currently using eval() to get the the desired effect which I know is very, very wrong. Here is an example of how I'm currently achieving what I want: var stringToObjectRef = function() { var myTestVar = "myTestObject"; var myTestObject = { 'item1' : 100, 'item2' : 12, 'item4' : 18 }; var myValue = eval(myTestVar + '.item1'); alert(myValue); }(); I've tried using something like [myTestVar].item1, but this returns undefined. What is the correct syntax to achieve this? Thanks in advance.

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• Object directing to a property when accessed as an iterable

  - by ThE_JacO

  I'm trying to figure out if there's an elegant and concise way to have a class accessing one of its own properties when "used" as a dictionary, basically redirecting all the methods that'd be implemented in an ordered dictionary to one of its properties. Currently I'm inheriting from IterableUserDict and explicitly setting its data to another property, and it seems to be working, but I know that UserDict is considered sort of old, and I'm concerned I might be overlooking something. What I have: class ConnectionInterface(IterableUserDict): def __init__(self, hostObject): self._hostObject= hostObject self.ports= odict.OrderedDict() self.inputPorts= odict.OrderedDict() self.outputPorts= odict.OrderedDict() self.data= self.ports This way I expect the object to behave and respond (and be used) the way I mean it to, except I want to get a freebie ordered dictionary behaviour on its property "ports" when it's iterated, items are gotten by key, something is looked up ala if this in myObject, and so on. Any advice welcome, the above seems to be working fine, but I have an odd itch that I might be missing something. Thanks in advance.

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• What is the time complexity of LinkedList.getLast() in Java?

  - by i.

  I have a private LinkedList in a Java class & will frequently need to retrieve the last element in the list. The lists need to scale, so I'm trying to decide whether I need to keep a reference to the last element when I make changes (to achieve O(1)) or if the LinkedList class does that already with the getLast() call. What is the big-O cost of LinkedList.getLast() and is it documented? (i.e. can I rely on this answer or should I make no assumptions & cache it even if it's O(1)?)

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• Why is Python so slow?

  - by Riemannliness

  Why is Python such a slow language, on average, compared to C/C++? I learned Python as my first programming language, but I've only just started with C and already I can feel and see the difference.

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• How can I use Amazon's API in PHP to search for books?

  - by TerranRich

  I'm working on a Facebook app for book sharing, reviewing, and recommendations. I've scoured the web, searched Google using every search phrase I could think of, but I could not find any tutorials on how to access the Amazon.com API for book information. I signed up for an AWS account, but even the tutorials on their website didn't help me one bit. They're all geared toward using cloud computing for file storage and processing, but that's not what I want. I just want to access their API to search info on books. Kind of like how http://openlibrary.org/ does it, where it's a simple URL call to get information on a book (but their databases aren't nearly as populated as Amazon's). Why is it so hard to find the information I need on Amazon's AWS site? If anybody could help, I would greatly appreciate it.

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• Is it possible to put a form control on its own thread?

  - by BVernon

  I'm using a DataGridView and some operations that I do cause it to become unresponsive for periods of time. Normally I would put data processing in its own thread to make the form more responsive, but in this case it's the DataGridView itself that's taking so long. This leads me to wonder whether it's possible to have the main form on one thread and the DataGridView on another thread so it doesn't prevent the main form from responding. I completely understand that doing so is probably not 'safe' and likely opens up a can of worms that makes it hardly worth trying and I fully expect this post will be getting down votes for merely suggesting such a ridiculous idea. Is this possible? And if so how would you go about it?

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