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• Rethinking Oracle Optimizer Statistics for P6 Part 2

  - by Brian Diehl

  In the previous post (Part 1), I tried to draw some key insights about the relationship between P6 and Oracle Optimizer Statistics.  The first is that average cardinality has the greatest impact on query optimization and that the particular queries generated by P6 are more likely to use this average during calculations. The second is that these are statistics that are unlikely to change greatly over the life of the application. Ultimately, our goal is to get the best query optimization possible.  Or is it? Stability No application administrator wants to get the call at 9am that their application users cannot get there work done because everything is running slow. This is a possibility with a regularly scheduled nightly collection of statistics. It may not just be slow performance, but a complete loss of service because one or more queries are optimized poorly. Ideally, this should not be the case. The database optimizer should make better decisions with more up-to-date data. Better statistics may give incremental performance benefit. However, this benefit must be balanced against the potential cost of system down time.  It is stability that we ultimately desire and not absolute optimal performance. We do want the benefit from more accurate statistics and better query plans, but not at the risk of an unusable system. As a result, I've developed the following methodology around managing database statistics for the P6 database.  1. No Automatic Re-Gathering - The daily, weekly, or other interval of statistic gathering is unlikely to be beneficial. Quite the opposite. It is more likely to cause problems. 2. Smart Re-Gathering - The time to collect statistics is when things have changed significantly. For a new installation of P6, this is happening more often because the data is growing from a few rows to thousands and more. But for a mature system, the data is not changing significantly from week-to-week. There are times to collect statistics: New releases of the application Changes in the underlying hardware or software versions (ex. new Oracle RDBMS version) When additional user groups are added. The new groups may use the software in significantly different ways. After significant changes in the data. This may be monthly, quarterly or yearly.  3. Always Test - If you take away one thing from this post, it would be to always have a plan to test after changing statistics. In reality, statistics can be collected as often as you desire provided there are tests in place to verify that performance is the same or better. These might be automated tests or simply a manual script of application functions. 4. Have a Way Out - Never change the statistics without a way to return to the previous set. Think of the statistics as one part of the overall application code that also includes the source code--both application and RDBMS. It would be foolish to change to the new code without a way to get back to the previous version. In the final post, I will talk about the actual script I created for P6 PMDB and possible future direction for managing query performance. 

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• return the result of a query and the total number of rows in a single function

  - by csotelo

  This is a question as might be focused on working in the best way, if there are other alternatives or is the only way: Using Codeigniter ... I have the typical 2 functions of list records and show total number of records (using the page as an alternative). The problem is that they are rather large. Sample 2 functions in my model: count Rows: function get_all_count() { $this->db->select('u.id_user'); $this->db->from('user u'); if($this->session->userdata('detail') != '1') { $this->db->join('management m', 'm.id_user = u.id_user', 'inner'); $this->db->where('id_detail', $this->session->userdata('detail')); if($this->session->userdata('management') === '1') { $this->db->or_where('detail', 1); } else { $this->db->where("id_profile IN ( SELECT e2.id_profile FROM profile e, profile e2, profile_path p, profile_path p2 WHERE e.id_profile = " . $this->session->userdata('profile') . " AND p2.id_profile = e.id_profile AND p.path LIKE(CONCAT(p2.path,'%')) AND e2.id_profile = p.id_profile )", NULL, FALSE); $this->db->where('MD5(u.id_user) <>', $this->session->userdata('id_user')); } } $this->db->where('u.id_user <>', 1); $this->db->where('flag <>', 3); $query = $this->db->get(); return $query->num_rows(); } results per page function get_all($limit, $offset, $sort = '') { $this->db->select('u.id_user, user, email, flag'); $this->db->from('user u'); if($this->session->userdata('detail') != '1') { $this->db->join('management m', 'm.id_user = u.id_user', 'inner'); $this->db->where('id_detail', $this->session->userdata('detail')); if($this->session->userdata('management') === '1') { $this->db->or_where('detail', 1); } else { $this->db->where("id_profile IN ( SELECT e2.id_profile FROM profile e, profile e2, profile_path p, profile_path p2 WHERE e.id_profile = " . $this->session->userdata('profile') . " AND p2.id_profile = e.id_profile AND p.path LIKE(CONCAT(p2.path,'%')) AND e2.id_profile = p.id_profile )", NULL, FALSE); $this->db->where('MD5(u.id_user) <>', $this->session->userdata('id_user')); } } $this->db->where('u.id_user <>', 1); $this->db->where('flag <>', 3); if($sort) $this->db->order_by($sort); $this->db->limit($limit, $offset); $query = $this->db->get(); return $query->result(); } You see, I repeat the most of the functions, the difference is that only the number of fields and management pages. I wonder if there is any alternative to get as much results as the query in a single function. I have seen many tutorials, and all create 2 functions: one to count and another to show results ... Will there be more optimal?

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• Writing a method to 'transform' an immutable object: how should I approach this?

  - by Prog

  (While this question has to do with a concrete coding dilemma, it's mostly about what's the best way to design a function.) I'm writing a method that should take two Color objects, and gradually transform the first Color into the second one, creating an animation. The method will be in a utility class. My problem is that Color is an immutable object. That means that I can't do color.setRGB or color.setBlue inside a loop in the method. What I can do, is instantiate a new Color and return it from the method. But then I won't be able to gradually change the color. So I thought of three possible solutions: 1- The client code includes the method call inside a loop. For example: int duration = 1500; // duration of the animation in milliseconds int steps = 20; // how many 'cycles' the animation will take for(int i=0; i<steps; i++) color = transformColor(color, targetColor, duration, steps); And the method would look like this: Color transformColor(Color original, Color target, int duration, int steps){ int redDiff = target.getRed() - original.getRed(); int redAddition = redDiff / steps; int newRed = original.getRed() + redAddition; // same for green and blue .. Thread.sleep(duration / STEPS); // exception handling omitted return new Color(newRed, newGreen, newBlue); } The disadvantage of this approach is that the client code has to "do part of the method's job" and include a for loop. The method doesn't do it's work entirely on it's own, which I don't like. 2- Make a mutable Color subclass with methods such as setRed, and pass objects of this class into transformColor. Then it could look something like this: void transformColor(MutableColor original, Color target, int duration){ final int STEPS = 20; int redDiff = target.getRed() - original.getRed(); int redAddition = redDiff / steps; int newRed = original.getRed() + redAddition; // same for green and blue .. for(int i=0; i<STEPS; i++){ original.setRed(original.getRed() + redAddition); // same for green and blue .. Thread.sleep(duration / STEPS); // exception handling omitted } } Then the calling code would usually look something like this: // The method will usually transform colors of JComponents JComponent someComponent = ... ; // setting the Color in JComponent to be a MutableColor Color mutableColor = new MutableColor(someComponent.getForeground()); someComponent.setForeground(mutableColor); // later, transforming the Color in the JComponent transformColor((MutableColor)someComponent.getForeground(), new Color(200,100,150), 2000); The disadvantage is - the need to create a new class MutableColor, and also the need to do casting. 3- Pass into the method the actual mutable object that holds the color. Then the method could do object.setColor or similar every iteration of the loop. Two disadvantages: A- Not so elegant. Passing in the object that holds the color just to transform the color feels unnatural. B- While most of the time this method will be used to transform colors inside JComponent objects, other kinds of objects may have colors too. So the method would need to be overloaded to receive other types, or receive Objects and have instanceof checks inside.. Not optimal. Right now I think I like solution #2 the most, than solution #1 and solution #3 the least. However I'd like to hear your opinions and suggestions regarding this.

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• How do I deploy building blocks (quick parts) for Microsoft Outlook 2007?

  - by now

  I want to deploy some building blocks for Microsoft Outlook 2007. Microsoft has put up a poor solution at http://office.microsoft.com/en-us/outlook/HA102086531033.aspx#4 that asks you to save a template. That solution would require you to distribute that template to all the clients. An optimal solution would allow you to put the template containing the building blocks somewhere on the network and simply use the ”Workgroup building blocks path” group policy setting for shared paths in Microsoft Office 2007. Sadly, Outlook doesn’t respect that policy. Also, the described solution mentioned in the article above doesn’t work. Step 4 requests you to save the template as a Word Template after first asking you to save it as an Outlook Template. It seems that they copy&pasted the steps from the Word article and forgot to check whether it worked (and adjust the steps accordingly). Anyway, does anyone have any suggestions for how to distribute the building blocks without distributing NormalEmail.dotm (which will overwrite the clients’ own building blocks each time it is updated). Thanks!

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• Selectively suppress XML Code Comments in C#?

  - by Mike Post

  We deliver a number of assemblies to external customers, but not all of the public APIs are officially supported. For example, due to less than optimal design choices sometimes a type must be publicly exposed from an assembly for the rest of our code to work, but we don't want customers to use that type. One part of communicating the lack of support is not provide any intellisense in the form of XML comments. Is there a way to selectively suppress XML comments? I'm looking for something other than ignoring warning 1591 since it's a long term maintenance issue. Example: I have an assembly with public classes A and B. A is officially supported and should have XML documentation. B is not intended for external use and should not be documented. I could turn on XML documentation and then suppress warning 1591. But when I later add the officially supported class C, I want the compiler to tell me that I've screwed up and failed to add the XML documentation. This wouldn't occur if I had suppressed 1591 at the project level. I suppose I could #pragma across entire classes, but it seems like there should be a better way to do this.

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• how to tackle this combinatorial algorithm problem

  - by Andrew Bullock

  I have N people who must each take T exams. Each exam takes "some" time, e.g. 30 min (no such thing as finishing early). Exams must be performed in front of an examiner. I need to schedule each person to take each exam in front of an examiner within an overall time period, using the minimum number of examiners for the minimum amount of time (i.e. no examiners idle) There are the following restrictions: No person can be in 2 places at once each person must take each exam once noone should be examined by the same examiner twice I realise that an optimal solution is probably NP-Complete, and that I'm probably best off using a genetic algorithm to obtain a best estimate (similar to this? http://stackoverflow.com/questions/184195/seating-plan-software-recommendations-does-such-a-beast-even-exist). I'm comfortable with how genetic algorithms work, what i'm struggling with is how to model the problem programatically such that i CAN manipulate the parameters genetically.. If each exam took the same amount of time, then i'd divide the time period up into these lengths, and simply create a matrix of time slots vs examiners and drop the candidates in. However because the times of each test are not necessarily the same, i'm a bit lost on how to approach this. currently im doing this: make a list of all "tests" which need to take place, between every candidate and exam start with as many examiners as there are tests repeatedly loop over all examiners, for each one: find an unscheduled test which is eligible for the examiner (based on the restrictions) continue until all tests that can be scheduled, are if there are any unscheduled tests, increment the number of examiners and start again. i'm looking for better suggestions on how to approach this, as it feels rather crude currently.

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• File path for J2ME FileConnection?

  - by Kilnr

  Hi, I'm writing a MIDlet which needs to write file. I'm using FileConnection from JSR-75 to accomplish this. The intention is to have this MIDlet runnning on as much devices as possible (all MIDP 2.0 devices with JSR-75 support, ideally). On several emulators and an HTC Touch Pro2, I can perfectly use the following code to get the root of the filesystem: Enumeration drives = FileSystemRegistry.listRoots(); String root = (String) drives.nextElement(); String path = "file:///" + root; However, on a Nokia S60 5th edition emulator, trying to open a FileConnection to this path throws a java.lang.SecurityException. Apparently S60 devices do not allow connections to the root of the filesystem. I realise I can use something like System.getProperty("fileconn.dir.photos"), but that isn't supported on all devices either. So, my actual question: what is the best approach to get a path to create a FileConnection with, that allows for maximum portability? Thanks. Edit: I suppose I could iterate over all the roots in the Enumeration, and check for a writable one, but that's hardly optimal for two reasons. First, there aren't necessarily any writable roots. Second, this could be the phone memory or a memory card, so the storage method wouldn't be consistent across devices, which is rather ugly.

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• How to use HTTP Live Streaming protocol in iPhone SDk 3.0

  - by Pugal Devan

  Hi Guys, i have developed on IPhone application and submitted to App store. But my application got rejected based on below criteria. Thank you for submitting your yyyyyyyy application. We have reviewed your application and have determined that it cannot be posted to the App Store at this time because it is not using the HTTP Live Streaming protocol to broadcast streaming video. HTTP Live Streaming is required when streaming video feeds over the cellular network, in order to have an optimal user experience and utilize cellular best practices. This protocol automatically determines bandwidth available to users and adjusts the bandwidth appropriately, even as bandwidth streams change. This allows you the flexibility to have as many streams as you like, as long as 64 kbps is set as the baseline feed. In my apps i have to stream prerecorded m4v and mp3 files from my server. I used MPMoviePlayerController to stream and play those videos / audio. How to implement the HTTP Live Streaming Protocol in my apps? Also can i get some sample code? Thanks in advance!

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• Determining the maximum stack depth

  - by Joa Ebert

  Imagine I have a stack-based toy language that comes with the operations Push, Pop, Jump and If. I have a program and its input is the toy language. For instance I get the sequence Push 1 Push 1 Pop Pop In that case the maximum stack would be 2. A more complicated example would use branches. Push 1 Push true If .success Pop Jump .continue .success: Push 1 Push 1 Pop Pop Pop .continue: In this case the maximum stack would be 3. However it is not possible to get the maximum stack by walking top to bottom as shown in this case since it would result in a stack-underflow error actually. CFGs to the rescue you can build a graph and walk every possible path of the basic blocks you have. However since the number of paths can grow quickly for n vertices you get (n-1)! possible paths. My current approach is to simplify the graph as much as possible and to have less possible paths. This works but I would consider it ugly. Is there a better (read: faster) way to attack this problem? I am fine if the algorithm produces a stack depth that is not optimal. If the correct stack size is m then my only constraint is that the result n is n = m. Is there maybe a greedy algorithm available that would produce a good result here?

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• Blackberry stopwatch implementation

  - by Michaela

  I'm trying to write a blackberry app that is basically a stopwatch, and displays lap times. First, I'm not sure I'm implementing the stopwatch functionality in the most optimal way. I have a LabelField (_myLabel) that displays the 'clock' - starting at 00:00. Then you hit the start button and every second the _myLabel field gets updated with how many seconds have past since the last update (should only ever increment by 1, but sometimes there is a delay and it will skip a number). I just can't think of a different way to do it - and I am new to GUI development and threads so I guess that's why. EDIT: Here is what calls the stopwatch: _timer = new Timer(); _timer.schedule(new MyTimerTask(), 250, 250); And here is the TimerTask: class MyTimerTask extends TimerTask { long currentTime; long startTime = System.currentTimeMillis(); public void run() { synchronized (Application.getEventLock()) { currentTime = System.currentTimeMillis(); long diff = currentTime - startTime; long min = diff / 60000; long sec = (diff % 60000) / 1000; String minStr = new Long(min).toString(); String secStr = new Long(sec).toString(); if (min < 10) minStr = "0" + minStr; if (sec < 10) secStr = "0" + secStr; _myLabel.setText(minStr + ":" + secStr); timerDisplay.deleteAll(); timerDisplay.add(_timerLabel); } } } Anyway when you stop the stopwatch it updates a historical table of lap time data. When this list gets long, the timer starts to degrade. If you try to scroll, then it gets really bad. Is there a better way to implement my stopwatch?

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• How to best handle exception to repeating calendar events

  - by blcArmadillo

  I'm working on a project that will require me to implement a calendar. I'm trying to come up with a system that is very flexible: can handle repeating events, exceptions to repeats, etc. I've looked at the schema for applications like iCal, Lotus Notes, and Mozilla to get an idea of how to go about implementing such a system. Currently I'm having trouble deciding what is the best way to handle exceptions to repeating events. I've used databases quite a bit but don't have a ton of experience with really optimizing everything so I'm not sure which method of the two I'm considering would be optimal in terms of overall performance and ability to query/search: Breaking the repeating event. So taking the changing the ending date on the current row for the repeating event, inserting a new row with the exception, and adding another row continuing the old sequence. Simply adding an exception. So adding a new row with some field that indicates it as an override. So here is why I can't decide. Method one will result in a lot more rows since each edit requires 2 extra rows as apposed to only one row by the second method. On the other hand I think the query to find an event would be much simper, and thus possibly faster(?) using the first method. The second method seems like it will require more calculating on the application server since once you get the data you'll have to remove the intersection of the two rows. I know databases are often the bottleneck for websites and while I'm sure a lot of you are thinking either is fine because your project will probably never get large enough for the difference in efficiency to really matter, I'd still like to implement the best solution. So what method would you guys pick, or would you do something completely different? Also, as a side note I'll be using MySQL and PHP. If there is another technology that you think would be better suited for this, especially in the database area, please mention it. Thanks for the advice.

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• Finding if a Binary Tree is a Binary Search Tree

  - by dharam

  Today I had an interview where I was asked to write a program which takes a Binary Tree and returns true if it is also a Binary Search Tree otherwise false. My Approach1: Perform an inroder traversal and store the elements in O(n) time. Now scan through the array/list of elements and check if element at ith index is greater than element at (i+1)th index. If such a condition is encountered, return false and break out of the loop. (This takes O(n) time). At the end return true. But this gentleman wanted me to provide an efficient solution. I tried but I was unsuccessfult, because to find if it is a BST I have to check each node. Moreover he was pointing me to think over recusrion. My Approach 2: A BT is a BST if for any node N N-left is < N and N-right N , and the INorder successor of left node of N is less than N and the inorder successor of right node of N is greater than N and the left and right subtrees are BSTs. But this is going to be complicated and running time doesn't seem to be good. Please help if you know any optimal solution. Thanks.

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• Remove duplicates from a sorted ArrayList while keeping some elements from the duplicates

  - by js82

  Okay at first I thought this would be pretty straightforward. But I can't think of an efficient way to solve this. I figured a brute force way to solve this but that's not very elegant. I have an ArrayList. Contacts is a VO class that has multiple members - name, regions, id. There are duplicates in ArrayList because different regions appear multiple times. The list is sorted by ID. Here is an example: Entry 0 - Name: John Smith; Region: N; ID: 1 Entry 1 - Name: John Smith; Region: MW; ID: 1 Entry 2 - Name: John Smith; Region: S; ID: 1 Entry 3 - Name: Jane Doe; Region: NULL; ID: 2 Entry 4 - Name: Jack Black; Region: N; ID: 3 Entry 6 - Name: Jack Black; Region: MW; ID: 3 Entry 7 - Name: Joe Don; Region: NE; ID: 4 I want to transform the list to below by combining duplicate regions together for the same ID. Therefore, the final list should have only 4 distinct elements with the regions combined. So the output should look like this:- Entry 0 - Name: John Smith; Region: N,MW,S; ID: 1 Entry 1 - Name: Jane Doe; Region: NULL; ID: 2 Entry 2 - Name: Jack Black; Region: N,MW; ID: 3 Entry 3 - Name: Joe Don; Region: NE; ID: 4 What are your thoughts on the optimal way to solve this? I am not looking for actual code but ideas or tips to go about the best way to get it done. Thanks for your time!!!

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• CQRS - The query side

  - by mattcodes

  A lot of the blogsphere articles related to CQRS (command query repsonsibility) seperation seem to imply that all screens/viewmodels are flat. e.g. Name, Age, Location Of Birth etc.. and thus the suggestion that implementation wise we stick them into fast read source etc.. single table per view mySQL etc.. and pull them out with something like primitive SqlDataReader, kick that nasty nhibernate ORM etc.. However, whilst I agree that domain models dont mapped well to most screens, many of the screens that I work with are more dimensional, and Im sure this is pretty common in LOB apps. So my question is how are people handling screen where by for example it displays a summary of customer details and then a list of their orders with a [more detail] link etc.... I thought about keeping with the straight forward SQL query to the Query Database breaking off the outer join so can build a suitable ViewModel to View but it seems like overkill? Alternatively (this is starting to feel yuck) in CustomerSummaryView table have a text/big (whatever the type is in your DB) column called Orders, and the columns for the Order summary screen grid are seperated by , and rows by |. Even with XML datatype it still feeel dirty. Any thoughts on an optimal practice?

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• Ascii Bytes Array To Int32 or Double

  - by Michael Covelli

  I'm re-writing alibrary with a mandate to make it totally allocation free. The goal is to have 0 collections after the app's startup phase is done. Previously, there were a lot of calls like this: Int32 foo = Int32.Parse(ASCIIEncoding.ASCII.GetString(bytes, start, length)); Which I believe is allocating a string. I couldn't find a C# library function that would do the same thing automatically. I looked at the BitConverter class, but it looks like that is only if your Int32 is encoded with the actual bytes that represent it. Here, I have an array of bytes representing Ascii characters that represent an Int32. Here's what I did public static Int32 AsciiBytesToInt32(byte[] bytes, int start, int length) { Int32 Temp = 0; Int32 Result = 0; Int32 j = 1; for (int i = start + length - 1; i >= start; i--) { Temp = ((Int32)bytes[i]) - 48; if (Temp < 0 || Temp > 9) { throw new Exception("Bytes In AsciiBytesToInt32 Are Not An Int32"); } Result += Temp * j; j *= 10; } return Result; } Does anyone know of a C# library function that already does this in a more optimal way? Or an improvement to make the above run faster (its going to be called millions of times during the day probably). Thanks!

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• Optimized graph drawing for the web

  - by Andreas Petersson

  Having seen some suggestions for graphs, I wonder what's the optimum for my problem. I want to render a directed graph to a servlet/picture that is displayed in the browser. There should be some kind of optimization of position. No dependency to Swing would be preferred. Algorithms are not important, since the structure of the graph is determined by business logic. It would be desired to be able add labels to edges as well. it would be optimal if i can serve this as png/svg. Which library/service would you recommend? clarifications: 1) The question is all about Graphs - like Directed Acyclic Graph - NOT - Charts. 2) flot, Google Charts - cannot plot graphs, only charts, or have i missed something? 3) no i do not need interactivity 4) graphviz would be nice, but the grappa java library is quite outdated and is built upon swing/awt. while it may be theoretically possible to render swing to images, it would not be my favorite way to to so in a server-app. 5) it would be fine to use an online service where the images are not hosted locally. edit: added links to Wikipedia to clarify graph/chart term

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• Worse is better. Is there an example?

  - by J.F. Sebastian

  Is there a widely-used algorithm that has time complexity worse than that of another known algorithm but it is a better choice in all practical situations (worse complexity but better otherwise)? An acceptable answer might be in a form: There are algorithms A and B that have O(N**2) and O(N) time complexity correspondingly, but B has such a big constant that it has no advantages over A for inputs less then a number of atoms in the Universe. Examples highlights from the answers: Simplex algorithm -- worst-case is exponential time -- vs. known polynomial-time algorithms for convex optimization problems. A naive median of medians algorithm -- worst-case O(N**2) vs. known O(N) algorithm. Backtracking regex engines -- worst-case exponential vs. O(N) Thompson NFA -based engines. All these examples exploit worst-case vs. average scenarios. Are there examples that do not rely on the difference between the worst case vs. average case scenario? Related: The Rise of ``Worse is Better''. (For the purpose of this question the "Worse is Better" phrase is used in a narrower (namely -- algorithmic time-complexity) sense than in the article) Python's Design Philosophy: The ABC group strived for perfection. For example, they used tree-based data structure algorithms that were proven to be optimal for asymptotically large collections (but were not so great for small collections). This example would be the answer if there were no computers capable of storing these large collections (in other words large is not large enough in this case). Coppersmith–Winograd algorithm for square matrix multiplication is a good example (it is the fastest (2008) but it is inferior to worse algorithms). Any others? From the wikipedia article: "It is not used in practice because it only provides an advantage for matrices so large that they cannot be processed by modern hardware (Robinson 2005)."

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• Django forms, inheritance and order of form fields

  - by Hannson

  I'm using Django forms in my website and would like to control the order of the fields. Here's how I define my forms: class edit_form(forms.Form): summary = forms.CharField() description = forms.CharField(widget=forms.TextArea) class create_form(edit_form): name = forms.CharField() The name is immutable and should only be listed when the entity is created. I use inheritance to add consistency and DRY principles. What happens which is not erroneous, in fact totally expected, is that the name field is listed last in the view/html but I'd like the name field to be on top of summary and description. I do realize that I could easily fix it by copying summary and description into create_form and loose the inheritance but I'd like to know if this is possible. Why? Imagine you've got 100 fields in edit_form and have to add 10 fields on the top in create_form - copying and maintaining the two forms wouldn't look so sexy then. (This is not my case, I'm just making up an example) So, how can I override this behavior? Edit: Apparently there's no proper way to do this without going through nasty hacks (fiddling with .field attribute). The .field attribute is a SortedDict (one of Django's internal datastructures) which doesn't provide any way to reorder key:value pairs. It does how-ever provide a way to insert items at a given index but that would move the items from the class members and into the constructor. This method would work, but make the code less readable. The only other way I see fit is to modify the framework itself which is less-than-optimal in most situations. In short the code would become something like this: class edit_form(forms.Form): summary = forms.CharField() description = forms.CharField(widget=forms.TextArea) class create_form(edit_form): def __init__(self,*args,**kwargs): forms.Form.__init__(self,*args,**kwargs) self.fields.insert(0,'name',forms.CharField()) That shut me up :)

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• configure batch to sent minute info instead of entire stdout

  - by Daniel

  Hi all, I am working on a RedHat server along with several other users. We use the batch utility to set a job queue. Some of the programs that I use write stuff to stdout during the run, with info on who much data has been processed to far and estimated time until completion etc. batch -q z at> myScript -i somefile -o someotherfile By default, the batch util send an email to me (since I configured it using .forward) with the entire output from stdout. Since the scripts writes something to stdout a few times each second, the amount of log-stuff I get from a two-day script can be ˜20 Mbs. Clearly not what I want. I can of course pipe stdout to a file like so batch -q z at> myScript -i somefile -o someotherfile > myscript.stdout.log but then I get a blank e-mail from the util. So to my question: Is it possible to configure batch so that it sends time the job started and ended, or run time or some oth valuable information to me, instead of a 20 Mb mail or a blank mail? Note that the scripts that I use are binaries and I cannot customize the code to output less info in the first place (which would be the optimal solution I guess). Thanks /Daniel

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• Issues in Convergence of Sequential minimal optimization for SVM

  - by Amol Joshi

  I have been working on Support Vector Machine for about 2 months now. I have coded SVM myself and for the optimization problem of SVM, I have used Sequential Minimal Optimization(SMO) by Mr. John Platt. Right now I am in the phase where I am going to grid search to find optimal C value for my dataset. ( Please find details of my project application and dataset details here http://stackoverflow.com/questions/2284059/svm-classification-minimum-number-of-input-sets-for-each-class) I have successfully checked my custom implemented SVM`s accuracy for C values ranging from 2^0 to 2^6. But now I am having some issues regarding the convergence of the SMO for C 128. Like I have tried to find the alpha values for C=128 and it is taking long time before it actually converges and successfully gives alpha values. Time taken for the SMO to converge is about 5 hours for C=100. This huge I think ( because SMO is supposed to be fast. ) though I`m getting good accuracy? I am screwed right not because I can not test the accuracy for higher values of C. I am actually displaying number of alphas changed in every pass of SMO and getting 10, 13, 8... alphas changing continuously. The KKT conditions assures convergence so what is so weird happening here? Please note that my implementation is working fine for C<=100 with good accuracy though the execution time is long. Please give me inputs on this issue. Thank You and Cheers.

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• Mac, PDFKit, PDF/X

  - by PhillipeTKern

  I'm in need of generating and viewing PDF/X-1a. After spending quite some time I came to the conclusion that the only way (hopefully someone will prove me wrong) to achieve this is to use Cocoa. More context: I need to generate PDF/X-1a, that is, all the fonts embeded, spot colors, overprint, ... preferably from Python. But the only libraries which support such things are iText and perhaps and Apache FOP. The first one could be used with Jython, which is ok but not optimal. But then, I simply could not find any viable viewer. Poppler, xpdf, Sumatra, mupdf, ghostscirpt - all of them - just cannot handle large CMYK pdfs, lots of text, ... I really would like to use open sourced libraries but unfortuntatelly the only option I see right now is to buy Mac as I saw one could print (Save-as) to built-in PDF printer under PDF/X conformance and I expect Preview to be comparable, if not better, to Acrobat. But I'm not sure if is it even possible to programmatically access the MacOS libraries responsible for generating PDF? I'm asking because I heard not everything from MacOS is available via public API... (And what Python goes, I thought I could use PyObjC..?) Any others ideas are of course very welcomed!

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• Multi-base conversion - using all combinations for URL shortener

  - by Guffa

  I am making an URL shortener, and I am struggling with the optimal way of encoding a number (id) into a character string. I am using the characters 0-9,A-Z,a-z so it will basically be a base-62 encoding. That is pretty basic, but it doesn't make use of all possible codes. The codes that it would produce would be: 0, 1, ... y, z, 10, 11, ... zy, zz, 100, 101, ... Notice that the codes 00 to 0z is not used, the same for 000 to 0zz, and so on. I would like to use all the codes, like this: 0, 1, ... y, z, 00, 01, ... zy, zz, 000, 001, ... It would be some combination of base-62 and base-63, with different bases depending on the position... Using base-62 is easy, for example: create procedure tiny_GetCode @UrlId int as set nocount on declare @Code varchar(10) set @Code = '' while (@UrlId > 0 or len(@Code) = 0) begin set @Code = substring('0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz', @UrlId % 62 + 1, 1) + @Code set @UrlId = @UrlId / 62 end select @Code But I haven't yet managed to make a multi-base conversion out of it, to make use of all the codes.

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• Spring - SessionAttribute problem

  - by Max

  Hello, I want to implement something like this: @Controller @SessionAttributes("promotion") class PromotionController { @RequestMapping("showPromo") void showPromotionInfo( @RequestParam("promId") String promotionId, @ModelAttribute Promotion promotion, Errors errors ) { promotion = Promotions.get(promotionId); if (promotion == null || promotion.validates() == false) { errors.reject("promotion.invalid"); } return "prom"; } } The code is invalid, wont work and has some bad errors, but I don't know how to write it better. When user comes to an URL "showPromo?promId=15", controller should validate if the promotion is valid (outdated/non-existent/etc.). If it is valid - it should show it's information and save the promotion to model and session. If it's not - it should show some error about promotion being invalid. Problem is, I need to save the promotion in the session (for several requests) and don't want to use direct session management. Is it currently possible with Spring? Or am I doing something wrong? Could you please provide the optimal solution to my problem using Spring 3? Thanks in advance.

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• Build System with Recursive Dependency Aggregation

  - by radman

  Hi, I recently began setting up my own library and projects using a cross platform build system (generates make files, visual studio solutions/projects etc on demand) and I have run into a problem that has likely been solved already. The issue that I have run into is this: When an application has a dependency that also has dependencies then the application being linked must link the dependency and also all of its sub-dependencies. This proceeds in a recursive fashion e.g. (For arguments sake lets assume that we are dealing exclusively with static libraries.) TopLevelApp.exe dependency_A dependency_A-1 dependency_A-2 dependency_B dependency_B-1 dependency_B-2 So in this example TopLevelApp will need to link dependency_A, dependency_A-1, dependency_A-2 etc and the same for B. I think the responsibility of remembering all of these manually in the target application is pretty sub optimal. There is also the issue of ensuring the same version of the dependency is used across all targets (assuming that some targets depend on the same things, e.g. boost). Now linking all of the libraries is required and there is no way of getting around it. What I am looking for is a build system that manages this for you. So all you have to do is specify that you depend on something and the appropriate dependencies of that library will be pulled in automatically. The build system I have been looking at is premake premake4 which doesn't handle this (as far as I can determine). Does anyone know of a build system that does handle this? and if there isn't then why not?

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• SQL Server CLR stored procedures in data processing tasks - good or evil?

  - by Gart

  In short - is it a good design solution to implement most of the business logic in CLR stored procedures? I have read much about them recently but I can't figure out when they should be used, what are the best practices, are they good enough or not. For example, my business application needs to parse a large fixed-length text file, extract some numbers from each line in the file, according to these numbers apply some complex business rules (involving regex matching, pattern matching against data from many tables in the database and such), and as a result of this calculation update records in the database. There is also a GUI for the user to select the file, view the results, etc. This application seems to be a good candidate to implement the classic 3-tier architecture: the Data Layer, the Logic Layer, and the GUI layer. The Data Layer would access the database The Logic Layer would run as a WCF service and implement the business rules, interacting with the Data Layer The GUI Layer would be a means of communication between the Logic Layer and the User. Now, thinking of this design, I can see that most of the business rules may be implemented in a SQL CLR and stored in SQL Server. I might store all my raw data in the database, run the processing there, and get the results. I see some advantages and disadvantages of this solution: Pros: The business logic runs close to the data, meaning less network traffic. Process all data at once, possibly utilizing parallelizm and optimal execution plan. Cons: Scattering of the business logic: some part is here, some part is there. Questionable design solution, may encounter unknown problems. Difficult to implement a progress indicator for the processing task. I would like to hear all your opinions about SQL CLR. Does anybody use it in production? Are there any problems with such design? Is it a good thing?

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