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  • ASP.NET MVC View ReRenders Part of Itself

    - by Jason
    In all my years of .NET programming I have not run across a bug as weird as this one. I discovered the problem because some elements on the page were getting double-bound by jQuery. After some (ridiculous) debugging, I finally discovered that once the view is completely done rendering itself and all its children partial views, it goes back to an arbitrary yet consistent location and re-renders itself. I have been pulling my hair out about this for two days now and I simply cannot get it to render itself only once! For lack of any better debugging idea, I've painstakingly added logging tracers throughout the HTML just so I can pin down what may be causing this. For instance, this code ($log just logs to the console): ... <script type="text/javascript">var x = 0; $log('1');</script> <div id="new-ad-form"> <script type="text/javascript">x++;$log('1.5', x);</script> ... will yield ... <--- this happens before this snippet 1 1.5 1 ... 10 <--- bottom of my form, after snippet 1.5 2 <--- beginning of part that runs again! ... 9 <--- this happens after this snippet I've searched my codebase high and low, but there is NOTHING that says that it should re-render part of a page. I'm wondering if the jQueryUI has anything to do with it, as #new-ad-form is the container for a jQueryUI dialog box. If this is potentially the case, here's my init code for that: $('#new-ad-form').dialog({ autoOpen: false, modal: true, width: 470, title: 'Create A New Ad', position: ['center', 35], close: AdEditor.reset });

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  • Is there a good way to QuickCheck Happstack.State methods?

    - by Paul Kuliniewicz
    I have a set of Happstack.State MACID methods that I want to test using QuickCheck, but I'm having trouble figuring out the most elegant way to accomplish that. The problems I'm running into are: The only way to evaluate an Ev monad computation is in the IO monad via query or update. There's no way to create a purely in-memory MACID store; this is by design. Therefore, running things in the IO monad means there are temporary files to clean up after each test. There's no way to initialize a new MACID store except with the initialValue for the state; it can't be generated via Arbitrary unless I expose an access method that replaces the state wholesale. Working around all of the above means writing methods that only use features of MonadReader or MonadState (and running the test inside Reader or State instead of Ev. This means forgoing the use of getRandom or getEventClockTime and the like inside the method definitions. The only options I can see are: Run the methods in a throw-away on-disk MACID store, cleaning up after each test and settling for starting from initialValue each time. Write the methods to have most of the code run in a MonadReader or MonadState (which is more easily testable), and rely on a small amount of non-QuickCheck-able glue around it that calls getRandom or getEventClockTime as necessary. Is there a better solution that I'm overlooking?

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  • Throttling CPU/Memory usage of a Thread in Java?

    - by Nalandial
    I'm writing an application that will have multiple threads running, and want to throttle the CPU/memory usage of those threads. There is a similar question for C++, but I want to try and avoid using C++ and JNI if possible. I realize this might not be possible using a higher level language, but I'm curious to see if anyone has any ideas. EDIT: Added a bounty; I'd like some really good, well thought out ideas on this. EDIT 2: The situation I need this for is executing other people's code on my server. Basically it is completely arbitrary code, with the only guarantee being that there will be a main method on the class file. Currently, multiple completely disparate classes, which are loaded in at runtime, are executing concurrently as separate threads. I inherited this code (the original author is gone). The way it's written, it would be a pain to refactor to create separate processes for each class that gets executed. If that's the only good way to limit memory usage via the VM arguments, then so be it. But I'd like to know if there's a way to do it with threads. Even as a separate process, I'd like to be able to somehow limit its CPU usage, since as I mentioned earlier, several of these will be executing at once. I don't want an infinite loop to hog up all the resources. EDIT 3: An easy way to approximate object size is with java's Instrumentation classes; specifically, the getObjectSize method. Note that there is some special setup needed to use this tool.

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  • Alternate widgets and logic for ManyToManyField with Django forms

    - by Jaearess
    In my Django project, I have a simple ticket system. When creating a ticket, certain users have the ability to assign the ticket to other users, and to email the ticket to other users as well (this is used as an FYI for those users, so they're aware of the ticket, even though it's not assigned to them.) At the moment, the form for adding a ticket is simply the default Django form, with the "assigned_to" and "email_to" fields being ManyToManyFields, and therefore displayed as MultipleSelect widgets, each with a list of all users. Due to the relatively large number of users, and general awkwardness of the MultipleSelect widget, and alternate layout is now required. The desired layout is a pair of simple Select widgets side-by-side. The first has the option of "Assign to" or "Email to" and the second is a list of the users. Essentially, like this: [Assign to] [John Doe] [Email to] [Jane Roe] [Jack Smith], etc. Of course, since an arbitrary number of users can be assigned or emailed a ticket, there's a simple button that runs some Javascript to add another set of widgets, to allow the user to assign and email as many people as they need to. So far all of that is fairly simple and straight forward. However, the problem I have is using this widget setup/logic setup with Django forms. Instead of lists of users to assign to and email, instead we're getting back pairs of information, one a user and the other which list that user should be placed in. What I'm looking for, but have yet to find, is a way to offload the translation between how the user uses the form, and how Django understands the model to the form itself, so I don't have to manually do the processing of the data before passing it to the form in each place this form is used. Additionally, there's a review screen with the option to go back and change the form before submitting it, so a way to have the form translate both to and from this format would be extremely helpful.

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  • How can I build the Boost.Python example on Ubuntu 9.10?

    - by Gatlin
    I am using Ubuntu 9.10 beta, whose repositories contain boost 1.38. I would like to build the hello-world example. I followed the instructions here (http://www.boost.org/doc/libs/1%5F40%5F0/libs/python/doc/tutorial/doc/html/python/hello.html), found the example project, and issued the "bjam" command. I have installed bjam and boost-build. I get the following output: Jamroot:18: in modules.load rule python-extension unknown in module Jamfile</usr/share/doc/libboost1.38-doc/examples/libs/python/example>. /usr/share/boost-build/build/project.jam:312: in load-jamfile /usr/share/boost-build/build/project.jam:68: in load /usr/share/boost-build/build/project.jam:170: in project.find /usr/share/boost-build/build-system.jam:248: in load /usr/share/boost-build/kernel/modules.jam:261: in import /usr/share/boost-build/kernel/bootstrap.jam:132: in boost-build /usr/share/doc/libboost1.38-doc/examples/libs/python/example/boost-build.jam:7: in module scope I do not know enough about Boost (this is an exploratory exercise for myself) to understand why the python-extension macro in the included Jamroot is not valid. I am running this example from the install directory, so I have not altered the Jamroot's use-project setting. As a side question, if I were to just willy-nilly start a project in an arbitrary directory, how would I write my jamroot?

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  • NetworkStream.Read delay .Net

    - by Gilbes
    I have a class that inherits from TcpClient. In that class I have a method to process responses. In that method I call I get the NetworkStream with MyBase.GetStream and call Read on it. This works fine, excpet the first call to read blocks too long. And by too long I mean that the socket has recieved plenty of data, but won't read it until some arbitrary limit is reached. I can see that it has recieved plenty of data using the packet sniffer WireShark. I have set the recieve buffer to small amounts, and very small amounts (like just a few bytes) to no avail. I have done the same with the buffer byte array I pass to the read method, and it still delays. Or to put it another way. I am download 600k. The download takes 5 seconds (at a little over 100k/second connection to the server which makes sense). The initial Read call takes 2-3 seconds and tells me only 256 bytes are availble (256 is the Recieve buffer and the size of the array I read in to). Then magically, the other few hundred thousand bytes can be read in 256 byte chunks in only a few process ticks each. Using a packet sniffer, I know that during those initial 2-3 seconds, the socket has recieved much more than just 256 bytes. My connection wasn't .25k/second for 3 seconds and then 400k for 2 seconds. How do I get the bytes from a socket as they come in?

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  • Oracle output: cursor, file, or very long string?

    - by Klay
    First, the setup: I have a table in an Oracle10g database with spatial columns. I need to be able to pass in a spatial reference so that I can reproject the geometry into an arbitrary coordinate system. Ultimately, I need to compress the results of this projection to a zip file and make it available for download through a Silverlight project. I would really appreciate ideas as to the best way to accomplish this. In the examples below, the SRID is the Spatial reference ID integer used to convert the geometric points into a new coordinate system. In particular, I can see a couple of possibilities. There are many more, but this is an idea of how I'm thinking: a) Pass SRID to a dynamic view -- perform projection, output a cursor -- send cursor to UTL_COMPRESS -- write output to a file (somehow) -- send URL to Silverlight app b) Use SRID to call Oracle function from Silverlight app -- perform projection, output a string -- build strings into a file -- compress file using SharpZipLib library in .NET -- send bytestream back to Silverlight app I've done the first two steps of b), and the conversion of 100 points took about 7 seconds, which is unacceptably slow. I'm hoping it would be faster doing the processing totally in Oracle. If anyone can see potential problems with either way of doing this, or can suggest a better way, it would be very helpful. Thanks!

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  • How do I prevent a C# method from executing using an attribute validator?

    - by Boydski
    I'd like to create an attribute-based validator that goes a few steps beyond what I've seen in examples. It'll basically prevent methods or other functionality from executing. Please be aware that I'm having to use AzMan since I have no availability to Active Directory in this scenario. Here's some pseudo code of what what I'm looking for: // Attribute validator class AttributeUsage is arbitrary at this point and may include other items [AttributeUsage( AttributeTargets.Method | AttributeTargets.Property, AllowMultiple = true, Inherited = true )] public class PermissionsValidatorAttribute : Attribute { public PermissionsValidatorAttribute(PermissionEnumeration permission){...} public bool UserCanCreateAndEdit(){...} public bool UserCanDelete(){...} public bool UserCanUpload(){...} } Here's a sample of a class/member that'll be decorated. The method will not be executed at all if the PermissionValidator.UserCanDelete() doesn't return true from wherever it's executed: public class DoStuffNeedingPermissions { [PermissionValidator(PermissionEnumeration.MustHaveDeletePermission)] public void DeleteSomething(){...} } I know this is a simple, incomplete example. But you should get the gist of what I'm needing. Make the assumption that DeleteSomething() already exists and I'm preferring to NOT modify the code within the method at all. I'm currently looking at things like the Validation Application Block and am messing with custom attribute POC's. But I'd love to hear opinions with code samples from everyone out there. I'm also certainly not opposed to other methods of accomplishing the same thing such as extension methods or whatever may work to accomplish the same thing. Please remember I'm making the attempt to minimize changes to existing DoStuffNeedingPermissions code. Thanks everyone!

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  • What's the standard convention for creating a new NSArray from an existing NSArray?

    - by Prairiedogg
    Let's say I have an NSArray of NSDictionaries that is 10 elements long. I want to create a second NSArray with the values for a single key on each dictionary. The best way I can figure to do this is: NSMutableArray *nameArray = [[NSMutableArray alloc] initWithCapacity:[array count]]; for (NSDictionary *p in array) { [nameArray addObject:[p objectForKey:@"name"]]; } self.my_new_array = array; [array release]; [nameArray release]; } But in theory, I should be able to get away with not using a mutable array and using a counter in conjunction with [nameArray addObjectAtIndex:count], because the new list should be exactly as long as the old list. Please note that I am NOT trying to filter for a subset of the original array, but make a new array with exactly the same number of elements, just with values dredged up from the some arbitrary attribute of each element in the array. In python one could solve this problem like this: new_list = [p['name'] for p in old_list] or if you were a masochist, like this: new_list = map(lambda p: p['name'], old_list) Having to be slightly more explicit in objective-c makes me wonder if there is an accepted common way of handling these situations.

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  • How to represent and insert into an ordered list in SQL?

    - by Travis
    I want to represent the list "hi", "hello", "goodbye", "good day", "howdy" (with that order), in a SQL table: pk | i | val ------------ 1 | 0 | hi 0 | 2 | hello 2 | 3 | goodbye 3 | 4 | good day 5 | 6 | howdy 'pk' is the primary key column. Disregard its values. 'i' is the "index" that defines that order of the values in the 'val' column. It is only used to establish the order and the values are otherwise unimportant. The problem I'm having is with inserting values into the list while maintaining the order. For example, if I want to insert "hey" and I want it to appear between "hello" and "goodbye", then I have to shift the 'i' values of "goodbye" and "good day" (but preferably not "howdy") to make room for the new entry. So, is there a standard SQL pattern to do the shift operation, but only shift the elements that are necessary? (Note that a simple "UPDATE table SET i=i+1 WHERE i=3" doesn't work, because it violates the uniqueness constraint on 'i', and also it updates the "howdy" row unnecessarily.) Or, is there a better way to represent the ordered list? I suppose you could make 'i' a floating point value and choose values between, but then you have to have a separate rebalancing operation when no such value exists. Or, is there some standard algorithm for generating string values between arbitrary other strings, if I were to make 'i' a varchar? Or should I just represent it as a linked list? I was avoiding that because I'd like to also be able to do a SELECT .. ORDER BY to get all the elements in order.

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  • Hibernate query for multiple items in a collection

    - by aarestad
    I have a data model that looks something like this: public class Item { private List<ItemAttribute> attributes; // other stuff } public class ItemAttribute { private String name; private String value; } (this obviously simplifies away a lot of the extraneous stuff) What I want to do is create a query to ask for all Items with one OR MORE particular attributes, ideally joined with arbitrary ANDs and ORs. Right now I'm keeping it simple and just trying to implement the AND case. In pseudo-SQL (or pseudo-HQL if you would), it would be something like: select all items where attributes contains(ItemAttribute(name="foo1", value="bar1")) AND attributes contains(ItemAttribute(name="foo2", value="bar2")) The examples in the Hibernate docs didn't seem to address this particular use case, but it seems like a fairly common one. The disjunction case would also be useful, especially so I could specify a list of possible values, i.e. where attributes contains(ItemAttribute(name="foo", value="bar1")) OR attributes contains(ItemAttribute(name="foo", value="bar2")) -- etc. Here's an example that works OK for a single attribute: return getSession().createCriteria(Item.class) .createAlias("itemAttributes", "ia") .add(Restrictions.conjunction() .add(Restrictions.eq("ia.name", "foo")) .add(Restrictions.eq("ia.attributeValue", "bar"))) .list(); Learning how to do this would go a long ways towards expanding my understanding of Hibernate's potential. :)

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  • Recognize Dates In A String

    - by Tim Scott
    I want a class something like this: public interface IDateRecognizer { DateTime[] Recognize(string s); } The dates might exist anywhere in the string and might be any format. For now, I could limit to U.S. culture formats. The dates would not be delimited in any way. They might have arbitrary amounts of whitespace between parts of the date. The ideas I have are: ANTLR Regex Hand rolled I have never used ANTLR, so I would be learning from scratch. I wonder if there are libraries or code samples out there that do something similar that could jump start me. Is ANTLR too heavy for such a narrow use? I have used Regex a lot before, but I hate it for all the reasons that most people hate it. I could certainly hand roll it but I'd rather not re-solve a solved problem. Suggestions? UPDATE: Here is an example. Given this input: This is a date 11/3/63. Here is another one: November 03, 1963; and another one Nov 03, 63 and some more (11/03/1963). The dates could be in any U.S. format. They might have dashes like 11-2-1963 or weird extra whitespace inside like this: Nov   3,   1963, and even maybe the comma is missing like [Nov 3 63] but that's an edge case. The output should be an array of seven DateTimes. Each date would be the same: 11/03/1963 00:00:00.

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  • What are some good ways to store performance statistics in a database for querying later?

    - by Nathan
    Goal: Store arbitrary performance statistics of stuff that you care about (how many customers are currently logged on, how many widgets are being processed, etc.) in a database so that you can understand what how your servers are doing over time. Assumptions: A database is already available, and you already know how to gather the information you want and are capable of putting it in the database however you like. Some Ideal Attributes of a Solution Causes no noticeable performance hit on the server being monitored Has a very high precision of measurement Does not store useless or redundant information Is easy to query (lends itself to gathering/displaying useful information) Lends itself to being graphed easily Is accurate Is elegant Primary Questions 1) What is a good design/method/scheme for triggering the storing of statistics? 2) What is a good database design for how to actually store the data? Example answers...that are sort of vague and lame... 1) I could, once per [fixed time interval], store a row of data with all the performance measurements I care about in each column of one big flat table indexed by timestamp and/or server. 2) I could have a daemon monitoring performance stuff I care about, and add a row whenever something changes (instead of at fixed time intervals) to a flat table as in #1. 3) I could trigger either as in #2, but I could store information about each aspect of performance that I'm measuring in separate tables, opening up the possibility of adding tons of rows for often-changing items, and few rows for seldom-changing items. Etc. In the end, I will implement something, even if it's some super-braindead approach I make up myself, but I'm betting there are some really smart people out there willing to share their experiences and bright ideas!

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  • Oracle command hangs when using view for "WHILE x IN..." subquery

    - by Calvin Fisher
    I'm working on a web service that fetches data from an oracle data source in chunks and passes it back to an indexing/search tool in XML format. I'm the C#/.NET guy, and am kind of fuzzy on parts of Oracle. Our Oracle team gave us the following script to run, and it works well: SELECT ROWID, [columns] FROM [table] WHERE ROWID IN ( SELECT ROWID FROM ( SELECT ROWID FROM [table] WHERE ROWID > '[previous_batch_last_rowid]' ORDER BY ROWID ) WHERE ROWNUM <= 10000 ) ORDER BY ROWID 10,000 rows is an arbitrary but reasonable chunk size and ROWID is sufficiently unique for our purposes to use as a UID since each indexing run hits only one table at a time. Bracketed values are filled in programmatically by the web service. Now we're going to start adding views to the indexing, each of which will union a few separate tables. Since ROWID would no longer function as a unique identifier, they added a column to the views (VIEW_UNIQUE_ID) that concatenates the ROWIDs from the component tables to construct a UID for each union. But this script does not work, even though it follows the same form as the previous one: SELECT VIEW_UNIQUE_ID, [columns] FROM [view] WHERE VIEW_UNIQUE_ID IN ( SELECT VIEW_UNIQUE_ID FROM ( SELECT VIEW_UNIQUE_ID FROM [view] WHERE ROWID > '[previous_batch_last_view_unique_id]' ORDER BY VIEW_UNIQUE_ID ) WHERE ROWNUM <= 10000 ) ORDER BY VIEW_UNIQUE_ID It hangs indefinitely with no response from the Oracle server. I've waited 20+ minutes and the SQLTools dialog box indicating a running query remains the same, with no progress or updates. I've tested each subquery independently and each works fine and takes a very short amount of time (<= 1 second), so the view itself is sound. But as soon as the inner two SELECT queries are added with "WHERE VIEW_UNIQUE_ID IN...", it hangs. Why doesn't this query work for views? In what important way are they not interchangeable here?

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  • Modify static variables while debugging in Eclipse

    - by sleske
    As an extension the the question "Modify/view static variables while debugging in Eclipse", I'd like to be able to modify static variables while debugging in Eclipse. For instance and local variables, I can just choose the variable in the "Variables" view of Eclipse, and use the context menu "Change value..." to change the value. This is not possible for arbitrary static variables, because they do not appear in the "Variables" view. What I tried: If you choose "Java / Show static variables" from the triangle menu in the "Variables" view, you can see and modify static member variables of the variables listed in the "Variables view". However, I did not find how to access a static member of a class whose instance does not appear in the "Variables view". You can of course enter a static member as an expression into the "Expression view" (using fully qualified name). Then you can see the value, but the "Expression view" does not have an option to modify the value (it does allow to modify members of an expression, but not the expression itself, even if the expression is a field). So, if I have a static variable like a boolean MyClass.disableAllBugs, is there a way to change MyClass.disableAllBugs during debugging? As an aside: I realize that even having public mutable static fields (i.e. mutable global variables) is very bad style. But some codebases have it, and then it's sometimes useful to modify it while debugging.

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  • Combinatorial optimisation of a distance metric

    - by Jose
    I have a set of trajectories, made up of points along the trajectory, and with the coordinates associated with each point. I store these in a 3d array ( trajectory, point, param). I want to find the set of r trajectories that have the maximum accumulated distance between the possible pairwise combinations of these trajectories. My first attempt, which I think is working looks like this: max_dist = 0 for h in itertools.combinations ( xrange(num_traj), r): for (m,l) in itertools.combinations (h, 2): accum = 0. for ( i, j ) in itertools.izip ( range(k), range(k) ): A = [ (my_mat[m, i, z] - my_mat[l, j, z])**2 \ for z in xrange(k) ] A = numpy.array( numpy.sqrt (A) ).sum() accum += A if max_dist < accum: selected_trajectories = h This takes forever, as num_traj can be around 500-1000, and r can be around 5-20. k is arbitrary, but can typically be up to 50. Trying to be super-clever, I have put everything into two nested list comprehensions, making heavy use of itertools: chunk = [[ numpy.sqrt((my_mat[m, i, :] - my_mat[l, j, :])**2).sum() \ for ((m,l),i,j) in \ itertools.product ( itertools.combinations(h,2), range(k), range(k)) ]\ for h in itertools.combinations(range(num_traj), r) ] Apart from being quite unreadable (!!!), it is also taking a long time. Can anyone suggest any ways to improve on this?

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  • How do tools like Hiphop for PHP deal with heterogenous arrays?

    - by Derek Thurn
    I think HipHop for PHP is an interesting tool. It essentially converts PHP code into C++ code. Cross compiling in this manner seems like a great idea, but I have to wonder, how do they overcome the fundamental differences between the two type systems? One specific example of my general question is heterogeneous data structures. Statically typed languages don't tend to let you put arbitrary types into an array or other container because they need to be able to figure out the types on the other end. If I have a PHP array like this: $mixedBag = array("cat", 42, 8.5, false); How can this be represented in C++ code? One option would be to use void pointers (or the superior version, boost::any), but then you need to cast when you take stuff back out of the array... and I'm not at all convinced that the type inferencer can always figure out what to cast to at the other end. A better option, perhaps, would be something more like a union (or boost::variant), but then you need to enumerate all possible types at compile time... maybe possible, but certainly messy since arrays can contain arbitrarily complex entities. Does anyone know how HipHop and similar tools which go from a dynamic typing discipline to a static discipline handle these types of problems?

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  • Autodiscovery for inclusion tags

    - by Ludwik Trammer
    The title may be a little confusing, but I don't know how else to call it. I would like to create a Django project with a large set of applications you could arbitrary turn on or off using INSTALLED_APPS option in settings.py (you would obviously also need to edit urls.py and run syncdb). After being turned on an app should be able to automatically: Register it's content in site-wide search. Luckily django-haystack has this built-in, so it's not a problem. Register cron jobs. django-cron does exactly that. Not a problem. Register a widget that should be displayed on the homepage. The homepage should include a list of boxes with widgets form different applications. I thought about inclusion tags, because you can put them anywhere on a page and they control both content and presentation. The problem is I don't know how to automatically get a list of inclusion tags provided by my applications, and display them one by one on a homepage. I need a way to register them somehow, and then display all registered tags.

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  • PHP: Next Available Value in an Array, starting with a non-indexed value

    - by Erik Smith
    I've been stumped on this PHP issue for about a day now. Basically, we have an array of hours formatted in 24-hour format, and an arbitrary value ($hour) (also a 24-hour). The problem is, we need to take $hour, and get the next available value in the array, starting with the value that immediately proceeds $hour. The array might look something like: $goodHours = array('8,9,10,11,12,19,20,21). Then the hour value might be: $hour = 14; So, we need some way to know that 19 is the next best time. Additionally, we might also need to get the second, third, or fourth (etc) available value. The issue seems to be that because 14 isn't a value in the array, there is not index to reference that would let us increment to the next value. To make things simpler, I've taken $goodHours and repeated the values several times just so I don't have to deal with going back to the start (maybe not the best way to do it, but a quick fix). I have a feeling this is something simple I'm missing, but I would be so appreciative if anyone could shed some light. Erik

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  • Python and a "time value of money" problem.

    - by jamieb
    (I asked this question earlier today, but I did a poor job of explaining myself. Let me try again) I have a client who is an industrial maintenance company. They sell service agreements that are prepaid 20 hour blocks of a technician's time. Some of their larger customers might burn through that agreement in two weeks while customers with fewer problems might go eight months on that same contract. I would like to use Python to help model projected sales revenue and determine how many billable hours per month that they'll be on the hook for. If each customer only ever bought a single service contract (never renewed) it would be easy to figure sales as monthly_revenue = contract_value * qty_contracts_sold. Billable hours would also be easy: billable_hrs = hrs_per_contract * qty_contracts_sold. However, how do I account for renewals? Assuming that 90% (or some other arbitrary amount) of customers renew, then their monthly revenue ought to grow geometrically. Another important variable is how long the average customer burns through a contract. How do I determine what the revenue and billable hours will be 3, 6, or 12 months from now, based on various renewal and burn rates? I assume that I'd use some type of recursive function but math was never one of my strong points. Any suggestions please? Edit: I'm thinking that the best way to approach this is to think of it as a "time value of money" problem. I've retitled the question as such. The problem is probably a lot more common if you think of "monthly sales" as something similar to annuity payments.

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  • Binary files printing and desired precision

    - by yCalleecharan
    Hi, I'm printing a variable say z1 which is a 1-D array containing floating point numbers to a text file so that I can import into Matlab or GNUPlot for plotting. I've heard that binary files (.dat) are smaller than .txt files. The definition that I currently use for printing to a .txt file is: void create_out_file(const char *file_name, const long double *z1, size_t z_size){ FILE *out; size_t i; if((out = _fsopen(file_name, "w+", _SH_DENYWR)) == NULL){ fprintf(stderr, "***> Open error on output file %s", file_name); exit(-1); } for(i = 0; i < z_size; i++) fprintf(out, "%.16Le\n", z1[i]); fclose(out); } I have three questions: Are binary files really more compact than text files?; If yes, I would like to know how to modify the above code so that I can print the values of the array z1 to a binary file. I've read that fprintf has to be replaced with fwrite. My output file say dodo.dat should contain the values of array z1 with one floating number per line. I have %.16Le up in my code but I think that %.15Le is right as I have 15 precision digits with long double. I have put a dot (.) in the width position as I believe that this allows expansion to an arbitrary field to hold the desired number. Am I right? As an example with %.16Le, I can have an output like 1.0047914240730432e-002 which gives me 16 precision digits and the width of the field has the right width to display the number correctly. Is placing a dot (.) in the width position instead of a width value a good practice? Thanks a lot...

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  • heterogeneous comparisons in python3

    - by Matt Anderson
    I'm 99+% still using python 2.x, but I'm trying to think ahead to the day when I switch. So, I know that using comparison operators (less/greater than, or equal to) on heterogeneous types that don't have a natural ordering is no longer supported in python3.x -- instead of some consistent (but arbitrary) result we raise TypeError instead. I see the logic in that, and even mostly think its a good thing. Consistency and refusing to guess is a virtue. But what if you essentially want the python2.x behavior? What's the best way to go about getting it? For fun (more or less) I was recently implementing a Skip List, a data structure that keeps its elements sorted. I wanted to use heterogeneous types as keys in the data structure, and I've got to compare keys to one another as I walk the data structure. The python2.x way of comparing makes this really convenient -- you get an understandable ordering amongst elements that have a natural ordering, and some ordering amongst those that don't. Consistently using a sort/comparison key like (type(obj).__name__, obj) has the disadvantage of not interleaving the objects that do have a natural ordering; you get all your floats clustered together before your ints, and your str-derived class separates from your strs. I came up with the following: import operator def hetero_sort_key(obj): cls = type(obj) return (cls.__name__+'_'+cls.__module__, obj) def make_hetero_comparitor(fn): def comparator(a, b): try: return fn(a, b) except TypeError: return fn(hetero_sort_key(a), hetero_sort_key(b)) return comparator hetero_lt = make_hetero_comparitor(operator.lt) hetero_gt = make_hetero_comparitor(operator.gt) hetero_le = make_hetero_comparitor(operator.le) hetero_ge = make_hetero_comparitor(operator.gt) Is there a better way? I suspect one could construct a corner case that this would screw up -- a situation where you can compare type A to B and type A to C, but where B and C raise TypeError when compared, and you can end up with something illogical like a > b, a < c, and yet b > c (because of how their class names sorted). I don't know how likely it is that you'd run into this in practice.

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  • Throwing a C++ exception after an inline-asm jump

    - by SoapBox
    I have some odd self modifying code, but at the root of it is a pretty simple problem: I want to be able to execute a jmp (or a call) and then from that arbitrary point throw an exception and have it caught by the try/catch block that contained the jmp/call. But when I do this (in gcc 4.4.1 x86_64) the exception results in a terminate() as it would if the exception was thrown from outside of a try/catch. I don't really see how this is different than throwing an exception from inside of some far-flung library, yet it obviously is because it just doesn't work. How can I execute a jmp or call but still throw an exception back to the original try/catch? Why doesn't this try/catch continue to handle these exceptions as it would if the function was called normally? The code: #include <iostream> #include <stdexcept> using namespace std; void thrower() { cout << "Inside thrower" << endl; throw runtime_error("some exception"); } int main() { cout << "Top of main" << endl; try { asm volatile ( "jmp *%0" // same thing happens with a call instead of a jmp : : "r"((long)thrower) : ); } catch (exception &e) { cout << "Caught : " << e.what() << endl; } cout << "Bottom of main" << endl << endl; } The expected output: Top of main Inside thrower Caught : some exception Bottom of main The actual output: Top of main Inside thrower terminate called after throwing an instance of 'std::runtime_error' what(): some exception Aborted

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  • Recycle Freed Objects

    - by uray
    suppose I need to allocate and delete object on heap frequently (of arbitrary size), is there any performance benefit if instead of deleting those objects, I will return it back to some "pool" to be reused later? would it give benefit by reduce heap allocation/deallocation?, or it will be slower compared to memory allocator performance, since the "pool" need to manage a dynamic collection of pointers. my use case: suppose I create a queue container based on linked list, and each node of that list are allocated on the heap, so every call to push() and pop() will allocate and deallocate that node: ` template <typename T> struct QueueNode { QueueNode<T>* next; T object; } template <typename T> class Queue { void push(T object) { QueueNode<T>* newNode = QueueNodePool<T>::get(); //get recycled node if(!newNode) { newNode = new QueueNode<T>(object); } // push newNode routine here.. } T pop() { //pop routine here... QueueNodePool<T>::store(unusedNode); //recycle node return unusedNode->object; } } `

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  • How to use a Base ViewModel in Asp.net MVC 2

    - by Picflight
    As I familiarize myself with Asp.Net MVC, I am using MVC 2, I have noticed the use of a BaseViewData class in the Kigg project which I am unsure how to implement. I want each of my ViewModels to have certain values available. Using an iterface comes to mind but I am wondering what the best practice is and how does Kigg do it? Kigg public abstract class BaseViewData { public string SiteTitle { get; set; } // ...other properties } public class UserListViewData : BaseViewData { public string Title { get; set; } // .. other stuff } In my WebForms application I use a BasePage that inherits from System.Web.UI.Page. So, in my MVC project, I have this: public abstract class BaseViewModel { public int SiteId { get; set; } } public class UserViewModel : BaseViewModel { // Some arbitrary ViewModel } Referencing the Kigg methodology, how do I make sure that each of my ViewModel that inherits from the BaseViewModel have the SiteId property? What is the best practice, samples or patterns I should be using?

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