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• Hidden controls, iframes or divs

  - by user287745

  What happens to the controls or the iframe or the div, which are hidden? Do they get transferred to the user side? Disabled: does it get transferred to the user side? What I want is, an aspx page will be having many iframes to display different pages. There will be many div tags to display CSS formatted information. To understand what I mean by many:- I have to transfer a complete website with 30 aspx pages into one single page! I have simply combined everything resulting in one extremely huge page. My concern is that on local host it loads fast, but when on online server accessed by numerous people for education purposes, the site (ONE PAGE) WILL SLOW DOWN terribly. To overcome this I thought of using hidden and disable options. What is an improved way of achieving the above? Yes, it sounds silly but this is the requirement. Edit: Yes, I know id and server tag must be set, but what I am asking will the div tag be sent to the user's browser? One answer is no. So can I enable them using JavaScript? Like document.getElementById(id).style.visibility="visible" What if I disable them, and from coding of JavaScript enable them? Will they be loaded at the time of enabling?

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• C# .NET: Descending comparison of a SortedDictionary?

  - by Rosarch

  I'm want a IDictionary<float, foo> that returns the larges values of the key first. private IDictionary<float, foo> layers = new SortedDictionary<float, foo>(new DescendingComparer<float>()); class DescendingComparer<T> : IComparer<T> where T : IComparable<T> { public int Compare(T x, T y) { return -y.CompareTo(x); } } However, this returns values in order of the smallest first. I feel like I'm making a stupid mistake here. Just to see what would happen, I removed the - sign from the comparator: public int Compare(T x, T y) { return y.CompareTo(x); } But I got the same result. This reinforces my intuition that I'm making a stupid error. This is the code that accesses the dictionary: foreach (KeyValuePair<float, foo> kv in sortedLayers) { // ... } UPDATE: This works, but is too slow to call as frequently as I need to call this method: IOrderedEnumerable<KeyValuePair<float, foo>> sortedLayers = layers.OrderByDescending(kv => kv.Key); foreach (KeyValuePair<float, ICollection<IGameObjectController>> kv in sortedLayers) { // ... } UPDATE: I put a break point in the comparator that never gets hit as I add and remove kv pairs from the dictionary. What could this mean?

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• SQL Where Clause Against View

  - by Adam Carr

  I have a view (actually, it's a table valued function, but the observed behavior is the same in both) that inner joins and left outer joins several other tables. When I query this view with a where clause similar to SELECT * FROM [v_MyView] WHERE [Name] like '%Doe, John%' ... the query is very slow, but if I do the following... SELECT * FROM [v_MyView] WHERE [ID] in ( SELECT [ID] FROM [v_MyView] WHERE [Name] like '%Doe, John%' ) it is MUCH faster. The first query is taking at least 2 minutes to return, if not longer where the second query will return in less than 5 seconds. Any suggestions on how I can improve this? If I run the whole command as one SQL statement (without the use of a view) it is very fast as well. I believe this result is because of how a view should behave as a table in that if a view has OUTER JOINS, GROUP BYS or TOP ##, if the where clause was interpreted prior to vs after the execution of the view, the results could differ. My question is why wouldn't SQL optimize my first query to something as efficient as my second query?

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• Query optimization (OR based)

  - by john194

  I have googled but I can't find answers for these questions. Your advice is appreciated. centOS on vps with 512MB RAM, nginx, php5 (fastcgi), mysql5 (myisam, not innodb). I need to optimize this app created by some ex-employee. This app is working, but it's slow. Table: t1(id[bigint(20)],c1[mediumtext],c2[mediumtext],c3[mediumtext],c4[mediumtext]) id is some random big number, and is PK Those mediumtext rows look like this: c1="|box-002877|" c2="|ct-2348|rd-11124854|hw-3949|wd-8872|hw-119037736|...etc.. " c3="|fg-2448|wd-11172|hw-1656|...etc.. " c4="|hg-2448|qd-16667|...etc." (some columns contain a lot of data, around 900 KiB, database around 300 MiB) Yes, mediumtext "is bad", and (20) is too big... but I didn't create this. Those codes can be found on any of those 4 mediumtext's... //he needs all the columns of the row containing $code, so he wrote this: function f1($code) { SELECT * FROM t1 WHERE c1 LIKE '%$code%' OR c2 LIKE '%$code%' OR c3 LIKE '%$code%' OR c4 LIKE '%$code%'; Questions: Q1. If $code is found on c1... mysql automatically stops checking and returns row=id+c1+c2+c3+c4? or it will continue (wasting time) checking c2, c3 and c4?... Q2. Mysql is working with this table on disk (not RAM) because of the mediumtext, right? is this the primary cause of slowness? Q3. That query can be cached by mysql (if using a big query_cache_size=128M value on the my.cnf)? or that's not cacheable due to the mediumtexts, or due to the "OR LIKE"...? Q4. Do you recommend rewriting this with mysql's INSTR() / LOCATE() / MATCH..AGAINST [FULLTEXT]?

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• Formatting inline many-to-many related models presented in django admin

  - by Jonathan

  I've got two django models (simplified): class Product(models.Model): name = models.TextField() price = models.IntegerField() class Invoice(models.Model): company = models.TextField() customer = models.TextField() products = models.ManyToManyField(Product) I would like to see the relevant products as a nice table (of product fields) in an Invoice page in admin and be able to link to the individual respective Product pages. My first thought was using the admin's inline - but django used a select box widget per related Product. This isn't linked to the Product pages, and also as I have thousands of products, and each select box independently downloads all the product names, it quickly becomes unreasonably slow. So I turned to using ModelAdmin.filter_horizontal as suggested here, which used a single instance of a different widget, where you have a list of all Products and another list of related Products and you can add\remove products in the later from the former. This solved the slowness, but it still doesn't show the relevant Product fields, and it ain't linkable. So, what should I do? tweak views? override ModelForms? I Googled around and couldn't find any example of such code...

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• Better ways to implement a modulo operation (algorithm question)

  - by ryxxui

  I've been trying to implement a modular exponentiator recently. I'm writing the code in VHDL, but I'm looking for advice of a more algorithmic nature. The main component of the modular exponentiator is a modular multiplier which I also have to implement myself. I haven't had any problems with the multiplication algorithm- it's just adding and shifting and I've done a good job of figuring out what all of my variables mean so that I can multiply in a pretty reasonable amount of time. The problem that I'm having is with implementing the modulus operation in the multiplier. I know that performing repeated subtractions will work, but it will also be slow. I found out that I could shift the modulus to effectively subtract large multiples of the modulus but I think there might still be better ways to do this. The algorithm that I'm using works something like this (weird pseudocode follows): result,modulus : integer (n bits) (previously defined) shiftcount : integer (initialized to zero) while( (modulus<result) and (modulus(n-1) != 1) ){ modulus = modulus << 1 shiftcount++ } for(i=shiftcount;i>=0;i++){ if(modulus<result){result = result-modulus} if(i!=0){modulus = modulus << 1} } So...is this a good algorithm, or at least a good place to start? Wikipedia doesn't really discuss algorithms for implementing the modulo operation, and whenever I try to search elsewhere I find really interesting but incredibly complicated (and often unrelated) research papers and publications. If there's an obvious way to implement this that I'm not seeing, I'd really appreciate some feedback.

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• Locating memory leak in Apache httpd process, PHP/Doctrine-based application

  - by Sam

  I have a PHP application using these components: Apache 2.2.3-31 on Centos 5.4 PHP 5.2.10 Xdebug 2.0.5 with Remote Debugging enabled APC 3.0.19 Doctrine ORM for PHP 1.2.1 using Query Caching and Results Caching via APC MySQL 5.0.77 using Query Caching I've noticed that when I start up Apache, I eventually end up 10 child processes. As time goes on, each process will grow in memory until each one approaches 10% of available memory, which begins to slow the server to a crawl since together they grow to take up 100% of memory. Here is a snapshot of my top output: PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 1471 apache 16 0 626m 201m 18m S 0.0 10.2 1:11.02 httpd 1470 apache 16 0 622m 198m 18m S 0.0 10.1 1:14.49 httpd 1469 apache 16 0 619m 197m 18m S 0.0 10.0 1:11.98 httpd 1462 apache 18 0 622m 197m 18m S 0.0 10.0 1:11.27 httpd 1460 apache 15 0 622m 195m 18m S 0.0 10.0 1:12.73 httpd 1459 apache 16 0 618m 191m 18m S 0.0 9.7 1:13.00 httpd 1461 apache 18 0 616m 190m 18m S 0.0 9.7 1:14.09 httpd 1468 apache 18 0 613m 190m 18m S 0.0 9.7 1:12.67 httpd 7919 apache 18 0 116m 75m 15m S 0.0 3.8 0:19.86 httpd 9486 apache 16 0 97.7m 56m 14m S 0.0 2.9 0:13.51 httpd I have no long-running scripts (they all terminate eventually, the longest being maybe 2 minutes long), and I am working under the assumption that once each script terminates, the memory it uses gets deallocated. (Maybe someone can correct me on that). My hunch is that it could be APC, since it stores data between requests, but at the same time, it seems weird that it would store data inside the httpd process. How can I track down which part of my app is causing the memory leak? What tools can I use to see how the memory usage is growing inside the httpd process and what is contributing to it?

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• Efficient alternative to merge() when building dataframe from json files with R?

  - by Bryan

  I have written the following code which works, but is painfully slow once I start executing it over thousands of records: require("RJSONIO") people_data <- data.frame(person_id=numeric(0)) json_data <- fromJSON(json_file) n_people <- length(json_data) for(lender in 1:n_people) { person_dataframe <- as.data.frame(t(unlist(json_data[[person]]))) people_data <- merge(people_data, person_dataframe, all=TRUE) } output_file <- paste("people_data",".csv") write.csv(people_data, file=output_file) I am attempting to build a unified data table from a series of json-formated files. The fromJSON() function reads in the data as lists of lists. Each element of the list is a person, which then contains a list of the attributes for that person. For example: [[1]] person_id name gender hair_color [[2]] person_id name location gender height [[...]] structure(list(person_id = "Amy123", name = "Amy", gender = "F", hair_color = "brown"), .Names = c("person_id", "name", "gender", "hair_color")) structure(list(person_id = "matt53", name = "Matt", location = structure(c(47231, "IN"), .Names = c("zip_code", "state")), gender = "M", height = 172), .Names = c("person_id", "name", "location", "gender", "height")) The end result of the code above is matrix where the columns are every person-attribute that appears in the structure above, and the rows are the relevant values for each person. As you can see though, some data is missing for some of the people, so I need to ensure those show up as NA and make sure things end up in the right columns. Further, location itself is a vector with two components: state and zip_code, meaning it needs to be flattened to location.state and location.zip_code before it can be merged with another person record; this is what I use unlist() for. I then keep the running master table in people_data. The above code works, but do you know of a more efficient way to accomplish what I'm trying to do? It appears the merge() is slowing this to a crawl... I have hundreds of files with hundreds of people in each file. Thanks! Bryan

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• Updating permissions on Amazon S3 files that were uploaded via JungleDisk

  - by Simon_Weaver

  I am starting to use Jungle Disk to upload files to an Amazon S3 bucket which corresponds to a Cloudfront distribution. i.e. I can access it via an http:// URL and I am using Amazon as a CDN. The problem I am facing is that Jungle Disk doesn't set 'read' permissions on the files so when I go to the corresponding URL in a browser I get an Amazon 'AccessDenied' error. If I use a tool like BucketExplorer to set the ACL then that URL now returns a 200. I really really like the simplicity of dragging files to a network drive. JungleDisk is the best program I've found to do this reliably without tripping over itself and getting confused. However it doesn't seem to have an option to make the files read-able. I really don't want to have to go to a different tool (especially if i have to buy it) to just change the permissions - and this seems really slow anyway because they generally seem to traverse the whole directory structure. JungleDisk provides some kind of 'web access' - but this is a paid feature and I'm not sure if it will work or not. S3 doesn't appear to propagate permissions down which is a real pain. I'm considering writing a manual tool to traverse my tree and set everything to 'read' but I'd rather not do this if this is a problem someone else has already solved.

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• Serialization Performance and Google Android

  - by Jomanscool2

  I'm looking for advice to speed up serialization performance, specifically when using the Google Android. For a project I am working on, I am trying to relay a couple hundred objects from a server to the Android app, and am going through various stages to get the performance I need. First I tried a terrible XML parser that I hacked together using Scanner specifically for this project, and that caused unbelievably slow performance when loading the objects (~5 minutes for a 300KB file). I then moved away from that and made my classes implement Serializable and wrote the ArrayList of objects I had to a file. Reading that file into the objects the Android, with the file already downloaded mind you, was taking ~15-30 seconds for the ~100KB serialized file. I still find this completely unacceptable for an Android app, as my app requires loading the data when starting the application. I have read briefly about Externalizable and how it can increase performance, but I am not sure as to how one implements it with nested classes. Right now, I am trying to store an ArrayList of the following class, with the nested classes below it. public class MealMenu implements Serializable{ private String commonsName; private long startMillis, endMillis, modMillis; private ArrayList<Venue> venues; private String mealName; } And the Venue class: public class Venue implements Serializable{ private String name; private ArrayList<FoodItem> foodItems; } And the FoodItem class: public class FoodItem implements Serializable{ private String name; private boolean vegan; private boolean vegetarian; } IF Externalizable is the way to go to increase performance, is there any information as to how java calls the methods in the objects when you try to write it out? I am not sure if I need to implement it in the parent class, nor how I would go about serializing the nested objects within each object.

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• Optimizing PHP require_once's for low disk i/o?

  - by buggedcom

  Q1) I'm designing a CMS (-who isn't!) but priority is being given to caching. Literally everything is cached. DB rows, DB id queries, Configuration data, processed data, compiled templates. Currently it has two layers of caching. The first is a opcode cache or memory cache such as apc, eaccelerator, xcache or memcached. If an entry is not found in there it is then searched for in the secondary slow cache, ie php includes. Are the opcode caches actually faster than doing a require_once to a php file with a var_export'd array of data in it? My tests are inconclusive as my development box (5.3 of XAMPP) keeps throwing errors installing any of the aforementioned programs. Q2) The CMS has numerous helper classes that are autoloaded on demand instead of loading all files. Mostly each has a require before it so no autoloading needs to take place, however this is not the question. Because a page script can have up to 50/60 helper files included I have a feeling that if the site was under pressure it would buckle because of all the i/o that this incurs. Ignore for the moment that there is output cache in place that would remove the need for what I am about to suggest, and also that opcode caches would render this moot. What I have tried to do is join all the helper files required for the scripts execution in one single file. This is achievable and works well, however it has a side effect of greatly increasing the memory usage dramatically even though technically the same code is being used. What are your thoughts and opinions on this?

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• How do we greatly optimize our MySQL database (or replace it) when using joins?

  - by jkaz

  Hi there, This is the first time I'm approaching an extremely high-volume situation. This is an ad server based on MySQL. However, the query that is used incorporates a lot of JOINs and is generally just slow. (This is Rails ActiveRecord, btw) sel = Ads.find(:all, :select = '*', :joins = "JOIN campaigns ON ads.campaign_id = campaigns.id JOIN users ON campaigns.user_id = users.id LEFT JOIN countries ON countries.campaign_id = campaigns.id LEFT JOIN keywords ON keywords.campaign_id = campaigns.id", :conditions = [flashstr + "keywords.word = ? AND ads.format = ? AND campaigns.cenabled = 1 AND (countries.country IS NULL OR countries.country = ?) AND ads.enabled = 1 AND campaigns.dailyenabled = 1 AND users.uenabled = 1", kw, format, viewer['country'][0]], :order = order, :limit = limit) My questions: Is there an alternative database like MySQL that has JOIN support, but is much faster? (I know there's Postgre, still evaluating it.) Otherwise, would firing up a MySQL instance, loading a local database into memory and re-loading that every 5 minutes help? Otherwise, is there any way I could switch this entire operation to Redis or Cassandra, and somehow change the JOIN behavior to match the (non-JOIN-able) nature of NoSQL? Thank you!

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• Open source file upload with no timeout on IIS6 with ASP, ASP.NET 2.0 or PHP5

  - by Christopher Done

  I'm after a cross-platform cross-browser way of uploading files such that there is no timeout. Uploads aren't necessarily huge -- some just take a long time to upload because of the uploader's slow connection -- but the server times out anyway. I hear that there are methods to upload files in chunks so that somehow the server decides not to timeout the upload. After searching around all I can see is proprietary upload helpers and Java and Flash (SWFUpload) widgets that aren't cross-platform, don't upload in chunks, or aren't free. I'd like a way to do it in any of these platforms (ASP, ASP.NET 2.0 or PHP5), though I am not very clued up on all this .NET class/controller/project/module/visual studio/compile/etc stuff, so some kind of runnable complete project that runs on .NET 2.0 would be helpful. PHP and ASP I can assume will be more straight-forward. Unless I am completely missing something, which I suspect/hope I am, reasonable web uploads are bloody hard work in any language or platform. So my question is: how can I perform web browser uploads, cross-platform, so that they don't timeout, using free software? Is it possible at all?

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• What is the correct way to implement a massive hierarchical, geographical search for news?

  - by Philip Brocoum

  The company I work for is in the business of sending press releases. We want to make it possible for interested parties to search for press releases based on a number of criteria, the most important being location. For example, someone might search for all news sent to New York City, Massachusetts, or ZIP code 89134, sent from a governmental institution, under the topic of "traffic". Or whatever. The problem is, we've sent, literally, hundreds of thousands of press releases. Searching is slow and complex. For example, a press release sent to Queens, NY should show up in the search I mentioned above even though it wasn't specifically sent to New York City, because Queens is a subset of New York City. We may also want to implement "and" and "or" and negation and text search to the query to create complex searches. These searches also have to be fast enough to function as dynamic RSS feeds. I really don't know anything about search theory, or how it's properly done. The way we are getting by right now is using a data mart to store the locations the releases were sent to in a single table. However, because of the subset thing mentioned above, the data mart is gigantic with millions of rows. And we haven't even implemented cities yet, and there are about 50,000 cities in the United States, which will exponentially increase the size of the data mart by so much I'm afraid it just won't work anymore. Anyway, I realize this is not a simple question and there won't be a "do this" answer. However, I'm hoping one of you can point me in the right direction where I can learn about how massive searches are done? Because I really know nothing about it. And such a search engine is turning out to be incredibly difficult to make. Thanks! I know there must be a way because if Google can search the entire internet we must be able to search our own database :-)

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• Porting an IBXpress Interbase 6 app to the current Firebird platform, on Delphi 7?

  - by robsoft

  Just wondering if there are any gotchas to be wary of here. We have a legacy D7 app that we developed several years ago for a client, which uses IBXpress to talk to the open source Interbase 6 build. We're having a number of issues with that platform these days (very slow to connect/start-up on new hardware being the chief one) and the client has okayed spending some time/money moving the database over to Firebird. We really DON'T want to embark upon moving it to D2010 (or D2007 which would be my preference right now) as we figure that we might have to move the database layer from IBXpress to something else to best suit Firebird anyway. And at the end of the day, the client is only looking to lessen the database pain, not overhaul/upgrade/rewrite the app. Given the ancestry of Firebird, is it a fairly painless, well-understood path from IBXpress Interbase 6 to (whatever) with Firebird? We have quite a number of sprocs, triggers (and even datatypes) etc in the existing IB database already (and the client has a number of paying customers all using this platform) so we felt that going to Firebird was more likely to be a smoother move than moving to SQL Express (or another flavour of DB entirely). Note that we're not looking for 'embedded' DB advocacy - in many of our client's customers' installations, the software is used in a multi-user client-server way so keeping that kind of approach is important.

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• Overlaying 2D paths on UIImage without scaling artifacts

  - by tat0

  I need to draw a path along the shape of an image in a way that it is always matching its position on the image independent of the image scale. Think of this like the hybrid view of Google Maps where streets names and roads are superimposed on top of the aerial pictures. Furthermore, this path will be drawn by the user's finger movements and I need to be able to retrieve the path keypoints on the image pixel coordinates. The user zooms-in in order to more precisely set the paths location. I manage to somehow make it work using this approach: -Create a custom UIView called CanvasView that handles touches interaction and delivers scaling, rotation, translation values to either the UIImageView or PathsView (see bellow) depending on a flag: deliverToImageOrPaths. -Create a UIImageView holding the base image. This is set as a children of CanvasView -Create a custom UIView called PathsView that keeps track of the 2D paths geometry and draws itself with a custom drawRect. This is set as children of the UIImageView. So hierarchy: CanvasView - UIImageView -PathsView In this way when deliverToImageOrPaths is YES, finger gestures transforms both the UIImageView and its child PathsView. When deliverToImageOrPaths is NO the gestures affect only the PathsView altering its geometry. So far so good. QUESTION: The problem I have is that when scaling the base UIImageView (via its .transform property) the PathsView is scaled with aliasing artifacts. drawRect is still being called on the PathsView but I guess it's performing the drawing using the original buffer size and then interpolating. How can I solve this issue? Are there better ways to implement these features? PS: I tried changing the PathsView layer class to CATiledLayer with levelsOfDetailBias 4 and levelsOfDetail 4. It solves the aliasing problem to some extent but it's unacceptable slow to render.

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• Thumbnails fadein fadeout specific div fade issues

  - by Omikron

  I am using this code to hide and show a div based on which thumbnail you rollover; $(document).ready(function(){ $('div.infodiv').hide(); $(".website_thumbs a").hover( function(){ var name = $(this).attr("name"); $(".infodiv").stop(); $("."+name).fadeIn(); }, function(){ var name = $(this).attr("name"); $("."+name).fadeTo(7000,1).fadeOut(); }); }); The script gets the name attribute from the thumbnail and displays the div with the corresponding class. Each div shares the .infodiv class but also has a class unique to each thumbnail. The functionality is basically where I want it but when you scroll over the thumbnails fast some of the divs get stuck in a kind of half faded-in state and stop working unless i roll over them once - then they slow fade in and they are usable again. I am a bit new to jQuery and would appreciate any help.

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• Fast JSON serialization (and comparison with Pickle) for cluster computing in Python?

  - by user248237

  I have a set of data points, each described by a dictionary. The processing of each data point is independent and I submit each one as a separate job to a cluster. Each data point has a unique name, and my cluster submission wrapper simply calls a script that takes a data point's name and a file describing all the data points. That script then accesses the data point from the file and performs the computation. Since each job has to load the set of all points only to retrieve the point to be run, I wanted to optimize this step by serializing the file describing the set of points into an easily retrievable format. I tried using JSONpickle, using the following method, to serialize a dictionary describing all the data points to file: def json_serialize(obj, filename, use_jsonpickle=True): f = open(filename, 'w') if use_jsonpickle: import jsonpickle json_obj = jsonpickle.encode(obj) f.write(json_obj) else: simplejson.dump(obj, f, indent=1) f.close() The dictionary contains very simple objects (lists, strings, floats, etc.) and has a total of 54,000 keys. The json file is ~20 Megabytes in size. It takes ~20 seconds to load this file into memory, which seems very slow to me. I switched to using pickle with the same exact object, and found that it generates a file that's about 7.8 megabytes in size, and can be loaded in ~1-2 seconds. This is a significant improvement, but it still seems like loading of a small object (less than 100,000 entries) should be faster. Aside from that, pickle is not human readable, which was the big advantage of JSON for me. Is there a way to use JSON to get similar or better speed ups? If not, do you have other ideas on structuring this? (Is the right solution to simply "slice" the file describing each event into a separate file and pass that on to the script that runs a data point in a cluster job? It seems like that could lead to a proliferation of files). thanks.

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• F#: Tell me what I'm missing about using Async.Parallel

  - by JBristow

  ok, so I'm doing ProjectEuler Problem #14, and I'm fiddling around with optimizations in order to feel f# out. in the following code: let evenrule n = n / 2L let oddrule n = 3L * n + 1L let applyRule n = if n % 2L = 0L then evenrule n else oddrule n let runRules n = let rec loop a final = if a = 1L then final else loop (applyRule a) (final + 1L) n, loop (int64 n) 1L let testlist = seq {for i in 3 .. 2 .. 1000000 do yield i } let getAns sq = sq |> Seq.head let seqfil (a,acc) (b,curr) = if acc = curr then (a,acc) else if acc < curr then (b,curr) else (a,acc) let pmap f l = seq { for a in l do yield async {return f a} } |> Seq.map Async.RunSynchronously let pmap2 f l = seq { for a in l do yield async {return f a} } |> Async.Parallel |> Async.RunSynchronously let procseq f l = l |> f runRules |> Seq.reduce seqfil |> fst let timer = System.Diagnostics.Stopwatch() timer.Start() let ans1 = testlist |> procseq Seq.map // 837799 00:00:08.6251990 printfn "%A\t%A" ans1 timer.Elapsed timer.Reset() timer.Start() let ans2 = testlist |> procseq pmap printfn "%A\t%A" ans2 timer.Elapsed // 837799 00:00:12.3010250 timer.Reset() timer.Start() let ans3 = testlist |> procseq pmap2 printfn "%A\t%A" ans3 timer.Elapsed // 837799 00:00:58.2413990 timer.Reset() Why does the Async.Parallel code run REALLY slow in comparison to the straight up map? I know I shouldn't see that much of an effect, since I'm only on a dual core mac. Please note that I do NOT want help solving problem #14, I just want to know what's up with my parallel code.

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• Should Development / Testing / QA / Staging environments be similar?

  - by Walter White

  Hi all, After much time and effort, we're finally using maven to manage our application lifecycle for development. We still unfortunately use ANT to build an EAR before deploying to Test / QA / Staging. My question is, while we made that leap forward, developers are still free to do as they please for testing their code. One issue that we have is half our team is using Tomcat to test on and the other half is using Jetty. I prefer Jetty slightly over Tomcat, but regardless we using WAS for all the other environments. My question is, should we develop on the same application server we're deploying to? We've had numerous bugs come up from these differences in environments. Tomcat, Jetty, and WAS are different under the hood. My opinion is that we all should develop on what we're deploying to production with so we don't have the problem of well, it worked fine on my machine. While I prefer Jetty, I just assume we all work on the same environment even if it means deploying to WAS which is slow and cumbersome. What are your team dynamics like? Our lead developers stepped down from the team and development has been a free for all since then. Walter

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• priority queue with limited space: looking for a good algorithm

  - by SigTerm

  This is not a homework. I'm using a small "priority queue" (implemented as array at the moment) for storing last N items with smallest value. This is a bit slow - O(N) item insertion time. Current implementation keeps track of largest item in array and discards any items that wouldn't fit into array, but I still would like to reduce number of operations further. looking for a priority queue algorithm that matches following requirements: queue can be implemented as array, which has fixed size and _cannot_ grow. Dynamic memory allocation during any queue operation is strictly forbidden. Anything that doesn't fit into array is discarded, but queue keeps all smallest elements ever encountered. O(log(N)) insertion time (i.e. adding element into queue should take up to O(log(N))). (optional) O(1) access for *largest* item in queue (queue stores *smallest* items, so the largest item will be discarded first and I'll need them to reduce number of operations) Easy to implement/understand. Ideally - something similar to binary search - once you understand it, you remember it forever. Elements need not to be sorted in any way. I just need to keep N smallest value ever encountered. When I'll need them, I'll access all of them at once. So technically it doesn't have to be a queue, I just need N last smallest values to be stored. I initially thought about using binary heaps (they can be easily implemented via arrays), but apparently they don't behave well when array can't grow anymore. Linked lists and arrays will require extra time for moving things around. stl priority queue grows and uses dynamic allocation (I may be wrong about it, though). So, any other ideas?

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• Why can't I fade out this table row in IE using jQuery?

  - by George Edison

  I can't get the table row to fade out in IE. It works in Chrome, but not IE. It just becomes really 'light' and stays on the screen. I tried IE8 with and without compatibility mode. <html> <head> <script type="text/javascript" src="jquery.js"></script> <script type="text/javascript"> function hideIt() { $('#hideme').fadeTo("slow", 0.0); } </script> </head> <body> <table> <tr id='hideme'> <td>Hide me!</td> </tr> </table> <button onclick='hideIt();'>Hide</button> </body> </html> Is there a workaround/solution for a smooth fade?

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• Solving problems involving more complex data structures with CUDA

  - by Nils

  So I read a bit about CUDA and GPU programming. I noticed a few things such that access to global memory is slow (therefore shared memory should be used) and that the execution path of threads in a warp should not diverge. I also looked at the (dense) matrix multiplication example, described in the programmers manual and the nbody problem. And the trick with the implementation seems to be the same: Arrange the calculation in a grid (which it already is in case of the matrix mul); then subdivide the grid into smaller tiles; fetch the tiles into shared memory and let the threads calculate as long as possible, until it needs to reload data from the global memory into shared memory. In case of the nbody problem the calculation for each body-body interaction is exactly the same (page 682): bodyBodyInteraction(float4 bi, float4 bj, float3 ai) It takes two bodies and an acceleration vectors. The body vector has four components it's position and the weight. When reading the paper, the calculation is understood easily. But what is if we have a more complex object, with a dynamic data structure? For now just assume that we have an object (similar to the body object presented in the paper) which has a list of other objects attached and the number of objects attached is different in each thread. How could I implement that without having the execution paths of the threads to diverge? I'm also looking for literature which explains how different algorithms involving more complex data structures can be effectively implemented in CUDA.

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• faster way to draw an image

  - by iHorse

  im trying to combine two images into a single image. unfortunately this has to be done very quickly in response to a user sliding a UISlider. i can combine the two images into a single image no problem. but the way I'm doing it is horribly slow. the sliders stick and jump rather frustratingly. i don't think i can throw the code into a background thread because i would run out of threads to quickly. i haven't actually tired that yet. below is my code. any ideas on how to speed it up would be helpful. UIGraphicsBeginImageContext(CGSizeMake(bodyImage.theImage.image.size.width * 1.2, bodyImage.theImage.image.size.height * 1.2)); [bodyImage.theImage.image drawInRect: CGRectMake(-2 + ((bodyImage.theImage.image.size.width * 1.2) - bodyImage.theImage.image.size.width)/2, kHeadAdjust, bodyImage.theImage.image.size.width * bodyImage.currentScale, bodyImage.theImage.image.size.height * bodyImage.currentScale)]; if(isCustHead) { [Head.theImage.image drawInRect: CGRectMake((bodyImage.theImage.image.size.width * 1.2 - headWidth)/2 - 11, 0, headWidth * 0.92, headWidth * (Head.theImage.image.size.height/Head.theImage.image.size.width) * 0.92)]; } else { [Head.theImage.image drawInRect: CGRectMake((bodyImage.theImage.image.size.width * 1.2 - (headWidth * defaultHeadAdjust))/2 - 10, 0, (headWidth * defaultHeadAdjust * 0.92), (headWidth * defaultHeadAdjust) * (Head.theImage.image.size.height/Head.theImage.image.size.width) * 0.92)]; } drawSurface.theImage.image = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext();

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• rs232 communication, general timing question

  - by Sunny Dee

  Hi, I have a piece of hardware which sends out a byte of data representing a voltage signal at a frequency of 100Hz over the serial port. I want to write a program that will read in the data so I can plot it. I know I need to open the serial port and open an inputstream. But this next part is confusing me and I'm having trouble understanding the process conceptually: I create a while loop that reads in the data from the inputstream 1 byte at a time. How do I get the while loop timing so that there is always a byte available to be read whenever it reaches the readbyte line? I'm guessing that I can't just put a sleep function inside the while loop to try and match it to the hardware sample rate. Is it just a matter of continuing reading the inputstream in the while loop, and if it's too fast then it won't do anything (since there's no new data), and if it's too slow then it will accumulate in the inputstream buffer? Like I said, i'm only trying to understand this conceptually so any guidance would be much appreciated! I'm guessing the idea is independent of which programming language I'm using, but if not, assume it is for use in Java. Thanks!

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