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  • RSA_sign and RSACryptoProvider.VerifySignature

    - by Miky D
    I'm trying to get up to speed on how to get some code that uses OpenSSL for cryptography, to play nice with another program that I'm writing in C#, using the Microsoft cryptography providers available in .NET. More to the point, I'm trying to have the C# program verify an RSA message signature generated by the OpenSSL code. The code that generates the signature looks something like this: // Code in C, using the OpenSSL RSA implementation char msgToSign[] = "Hello World"; // the message to be signed char signature[RSA_size(rsa)]; // buffer that will hold signature int slen = 0; // will contain signature size // rsa is an OpenSSL RSA context, that's loaded with the public/private key pair memset(signature, 0, sizeof(signature)); RSA_sign(NID_sha1 , (unsigned char*)msgToSign , strlen(msgToSign) , signature , &slen , rsa); // now signature contains the message signature // and can be verified using the RSA_verify counterpart // .. I would like to verify the signature in C# In C#, I would do the following: import the other side's public key into an RSACryptoServiceProvider object receive the message and it's signature try to verify the signature I've got the first two parts working (I've verified that the public key is loading properly because I managed to send an RSA encrypted text from the C# code to the OpenSSL code in C and successfully have it decrypted) In order to verify the signature in C#, I've tried using the: VerifySignature method of the RSACryptoServiceProvider but that didn't work. And digging around the internet I was only able to find some vague information pointing out that .NET uses a different method for generating the signature than OpenSSL does. So, does anybody know how to accomplish this?

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  • C# vs C - Big performance difference

    - by John
    I'm finding massive performance differences between similar code in C anc C#. The C code is: #include <stdio.h> #include <time.h> #include <math.h> main() { int i; double root; clock_t start = clock(); for (i = 0 ; i <= 100000000; i++){ root = sqrt(i); } printf("Time elapsed: %f\n", ((double)clock() - start) / CLOCKS_PER_SEC); } And the C# (console app) is: using System; using System.Collections.Generic; using System.Text; namespace ConsoleApplication2 { class Program { static void Main(string[] args) { DateTime startTime = DateTime.Now; double root; for (int i = 0; i <= 100000000; i++) { root = Math.Sqrt(i); } TimeSpan runTime = DateTime.Now - startTime; Console.WriteLine("Time elapsed: " + Convert.ToString(runTime.TotalMilliseconds/1000)); } } } With the above code, the C# completes in 0.328125 seconds (release version) and the C takes 11.14 seconds to run. The c is being compiled to a windows executable using mingw. I've always been under the assumption that C/C++ were faster or at least comparable to C#.net. What exactly is causing the C to run over 30 times slower? EDIT: It does appear that the C# optimizer was removing the root as it wasn't being used. I changed the root assignment to root += and printed out the total at the end. I've also compiled the C using cl.exe with the /O2 flag set for max speed. The results are now: 3.75 seconds for the C 2.61 seconds for the C# The C is still taking longer, but this is acceptable

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  • Handling learning curve for new developers

    - by pete the pagan-gerbil
    Our company likes to hire new developers, with no experience. We have a core set of skills that we try to get them up to speed with, like ASP.NET and WinForms - to teach basic programming, the .NET languages, and the things they'll need to maintain and write. We also try and mentor them through early projects, so they can learn from someone more experienced. Recently, we've been seeing the benefits of new frameworks like MVC and ideas like Unit Testing and TDD (by extension, dependancy injection and IoC), and we'd like to start using these in the team. However, this increases the time that a junior would have before they can get started on a new project - because doing something like unit tests wrong could cause major headaches months or years later in maintenance, especially if we believe unit tests to be comprehensive. How do you handle the huge amount of things that a junior will need to take on, acknowledging that the business wants them working independantly as soon as possible? Is it acceptable to tell them not to unit test till a while after they are independant (and give them small, simpler projects in the meantime) before taking them to 'level 2' of the core skills?

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  • What do you use to play sound in iPhone games?

    - by zoul
    Hello! I have a performance-intensive iPhone game I would like to add sounds to. There seem to be about three main choices: (1) AVAudioPlayer, (2) Audio Queues and (3) OpenAL. I’d hate to write pages of low-level code just to play a sample, so that I would like to use AVAudioPlayer. The problem is that it seems to kill the performace – I’ve done a simple measuring using CFAbsoluteTimeGetCurrent and the play message seems to take somewhere from 9 to 30 ms to finish. That’s quite miserable, considering that 25 ms == 40 fps. Of course there is the prepareToPlay method that should speed things up. That’s why I wrote a simple class that keeps several AVAudioPlayers at its disposal, prepares them beforehand and then plays the sample using the prepared player. No cigar, still it takes the ~20 ms I mentioned above. Such performance is unusable for games, so what do you use to play sounds with a decent performance on iPhone? Am I doing something wrong with the AVAudioPlayer? Do you play sounds with Audio Queues? (I’ve written something akin to AVAudioPlayer before 2.2 came out and I would love to spare that experience.) Do you use OpenAL? If yes, is there a simple way to play sounds with OpenAL, or do you have to write pages of code? Update: Yes, playing sounds with OpenAL is fairly simple.

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  • Best strategy for synching data in iPhone app

    - by iamj4de
    I am working on a regular iPhone app which pulls data from a server (XML, JSON, etc...), and I'm wondering what is the best way to implement synching data. Criteria are speed (less network data exchange), robustness (data recovery in case update fails), offline access and flexibility (adaptable when the structure of the database changes slightly, like a new column). I know it varies from app to app, but can you guys share some of your strategy/experience? For me, I'm thinking of something like this: 1) Store Last Modified Date in iPhone 2) Upon launching, send a message like getNewData.php?lastModifiedDate=... 3) Server will process and send back only modified data from last time. 4) This data is formatted as so: <+><data id="..."></data></+> // add this to SQLite/CoreData <-><data id="..."></data></-> // remove this <%><data id="..."><attribute>newValue</attribute></data></%> // new modified value I don't want to make <+, <-, <%... for each attribute as well, because it would be too complicated, so probably when receive a <% field, I would just remove the data with the specified id and then add it again (assuming id here is not some automatically auto-incremented field). 5) Once everything is downloaded and updated, I will update the Last Modified Date field. The main problem with this strategy is: If the network goes down when I am updating something = the Last Modified Date is not yet updated = next time I relaunch the app, I will have to go through the same thing again. Not to mention potential inconsistent data. If I use a temporary table for update and make the whole thing atomic, it would work, but then again, if the update is too long (lots of data change), the user has to wait a long time until new data is available. Should I use Last-Modified-Date for each of the data field and update data gradually?

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  • How can I initialize a QTMovie object with certain attributes using writable data?

    - by c-had
    I'm trying to create an empty QTMovie object that I can add segments to, and then play. This is easy to do with something like: movie = [[QTMovie alloc] initToWritableData:[NSMutableData dataWithCapacity:1048576] error:&error]; I can then use -insertSegmentOfMovie to insert segments from other movies into this one so I can play it back. The problem is that I also need to set a certain attribute when creating the QTMovie object. In particular, I need to set the QTMovieRateChangesPreservePitchAttribute attribute, so that I can alter playback speed during playback without changing pitch. This attribute cannot be written after the movie is initialized. So, I can create the QTMovie object like this: movie = [[QTMovie alloc] initWithAttributes:[NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithBool:YES], QTMovieRateChangesPreservePitchAttribute, nil] error:&error]; Unfortunately, this is not editable. I've tried setting the QTMovieEditableAttribute as well on creation, but it does not help. I still get an exception when I try to insert anything into this movie. I presume this is because there is no writable file or data reference associated with the QTMovie. Any ideas on how to solve this?

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  • MS Query Analizer/Management Studio replacement?

    - by kprobst
    I've been using SQL Server since version 6.5 and I've always been a bit amazed at the fact that the tools seem to be targeted to DBAs rather than developers. I liked the simplicity and speed of the Query Analizer for example, but hated the built-in editor, which was really no better than a syntax coloring-capable Notepad. Now that we have Management Studio the management part seems a bit better but from a developer standpoint the tools is even worse. Visual Studio's excellent text editor... without a way to customize keyboard bindings!? Don't get me started on how unusable is the tree-based management hierarchy. Why can't I re-root the tree on a list of stored procs for example the way the Enterprise Manager used to allow? Now I have a treeview that needs to be scrolled horizontally, which makes it eminently useless. The SQL server support in Visual Studio is fantastic for working with stored procedures and functions, but it's terrible as a general ad hoc data query tool. I've tried various tools over the years but invariably they seem to focus on the management side and shortchange the developer in me. I just want something with basic admin capabilities, good keyboard support and requisite DDL functionality (ideally something like the Query Analyzer). At this point I'm seriously thinking of using vim+sqlcmd and a console... I'm that desperate :) Those of you who work day in and day out with SQL Server and Visual Studio... do you find the tools to be adequate? Have you ever wished they were better and if you have found something better, could you share please? Thanks!

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  • Hiring my first employee

    - by Ady
    A few years ago I moved to a new job having been programming for 2 years using C#, however this new company was mainly using VB6. I made the case for .NET and won, but one of the consessions I had to make was to use VB.NET and not C# (understandable as most of the other developers were already using VB). Three years later it was time to move on, but when applying for jobs I couldn't get past the recruitment agents. I realised that when they were looking at the basic requirements (5 years experience) that they could not add 2 and 3 together to make 5. They were looking for 5 years in VB or C# not across both. Frustrated I decided to combine my skills with a designer friend and start my own company. After two years of hard graft we are now looking for our first employee (a programmer), and this question has hit me again, but now I see the employers perspective. Why take the risk of someone getting up to speed when you have thousands of applicants to choose from. So my question is this, if I define the requirements to be too narrow, I could miss the really great candidates. But if they are too broad it's going to take ages to go through them all. This will be our first 'employee' so the choice needs to be good, I can't afford to make a mistake and employ someone naff. Another option would be to choose a bright university graduate, and train them up (less of a risk because we can pay them less). What have others done in this situation, and what would you recommend I do?

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  • Poor DB4O performance - What am I doing wrong?

    - by Jon
    I read Rob Conery's post about Object databases and thought I'd give it a go. I have a class lets say Book with 15 properties mostly string, some int, one Datetime and 2 decimals. I used Rob's code to open the database file etc to test on a Winforms project not a Web project. So I did the following: for(int i = 0; i < 1000000; i++) { var Book = new Book(); //Assign variables s.Save(Book); } s.CommitChanges(); This took at least a couple of minutes. I then tried to retrieve all data to test speed: var spp = s.All<Passports>(); This one line was quick, however, then doing: sppp.Count() as well as a seperate test doing a foreach loop and incrementing a counter took a couple of minutes. This seems quite slow to me. Am I doing something wrong or am I expecting too much?

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  • Are there any configurable parameters to the gpsd?

    - by danatel
    I use the gpsd daemon with my application. Sometimes, the gpsd ceases to work with no apparent reason (clean sky). Even the gpsmon monitor shows no fix. Are there any parameters which must be set? Or is it a hardware problem? I am surprissed that many satellites are visible but the "Stat" bitmap does not contain the bit 7 - ephemeris data available. Should i somewhat pre-configure my position to allow for correct ephemeris data? Here is my gpsmon screen: 127.0.0.1:2947:/dev/ttyS3 SiRF binary> ^[[4~ -¦¦¦¦¦¦¦¦¦¦¦ X ¦¦¦¦¦¦ Y ¦¦¦¦¦¦ Z ¦¦¦¦¦¦¦¦¦¦ North ¦¦¦¦ East ¦¦¦¦¦ Alt ¦¦¦¦¦¦¦¦¦¬ -Pos: 3949260 1166016 4856299 m 49.89411° 16.44920° 1379 m - -Vel: 0.0 0.0 0.0 m/s 0.0 0.0 0.0 climb m/s- -Week+TOW:1578+224837.06 Day: 2 14:27:17.06 Heading: 0.0° 0.0 speed m/s- -Skew: -13.025817 TZ: -7200 HDOP: 0.0 M1:00 M2: 00 - -Fix: 0 = - L¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦ Packet type 2 (0x02) ¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦- -¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¬-¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¬ -Ch PRN Az El Stat C/N ? A --Version: - - 0 2 243 19 003f 40.4 -L¦¦¦¦¦¦¦ Packet Type 6 (0x06) ¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦- - 1 10 249 68 003f 43.0 --¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¬ - 2 13 90 30 003f 40.9 --SVs: 0 Drift: 96506 Bias: 135976716 - - 3 7 66 67 003f 39.8 --Estimated GPS Time: 224837059 - - 4 5 295 49 003d 39.7 -L¦¦¦¦¦¦¦ Packet type 7 (0x07) ¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦- - 5 8 210 69 003f 41.0 --¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¬ - 6 23 96 5 002d 28.0 --Max: 167.570Lat: 132.129Time: 0.075 MS: 02 - - 7 6 43 3 002d 23.1 -L¦¦¦¦¦¦¦ Packet type 9 (0x09) ¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦- - 8 28 163 16 003f 39.8 --¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¬ - 9 0 0 0 0000 0.0 --SVs: 11 = 8 10 7 5 13 2 28 23 3 6 4 - -10 3 55 4 002d 24.7 -L¦¦¦¦¦¦¦ Packet type 13 (0x0D) ¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦- -11 0 0 0 0000 0.0 --¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¬ L¦¦¦ Packet Type 4 (0x04) ¦¦¦--DGPS source: 1 (SBAS) Corrections: 12 - L¦¦¦¦¦¦¦ Packet type 27 (0x1B) ¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦-q

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  • Using Partitions for a large MySQL table

    - by user293594
    An update on my attempts to implement a 505,000,000-row table on MySQL on my MacBook Pro: Following the advice given, I have partitioned my table, tr: i UNSIGNED INT NOT NULL, j UNSIGNED INT NOT NULL, A FLOAT(12,8) NOT NULL, nu BIGINT NOT NULL, KEY (nu), key (A) with a range on nu. nu ought to be a real number, but because I only have 6-d.p. accuracy and the maximum value of nu is 30000. I multiplied it by 10^8 made it a BIGINT - I gather one can't use FLOAT or DOUBLE values to PARTITION a MySQL table. Anyway, I have 15 partitions (p0: nu<25,000,000,000, p1: nu<50,000,000,000, etc.). I was thinking that this should speed up a typical to SELECT: SELECT * FROM tr WHERE nu>95000000000 AND nu<100000000000 AND A.>1. to something of the order of the same query on a table consisting of only the data in the relevant partition (<30 secs). But it's taking 30mins+ to return rows for queries within a partition and double that if the query is for rows spanning two (contiguous) partitions. I realise I could just have 15 different tables, and query them separately, but is there a way to do this 'automatically' with partitions? Has anyone got any suggestions?

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  • Play! Framework 1.2.4 --- C3P0 settings to avoid Communications link failure do to idle time

    - by HelpMeStackOverflowMyOnlyHope
    I'm trying to customize my C3P0 settings to avoid the error shown at the bottom of this post. It was suggested at this url --- http://make-it-open.blogspot.com/2008/12/sql-error-0-sqlstate-08s01.html --- to adjust the settings as follows: In hibernate.cfg.xml, write <property name="c3p0.min_size">5</property> <property name="c3p0.max_size">20</property> <property name="c3p0.timeout">1800</property> <property name="c3p0.max_statements">50</property> Then create "c3p0.properties" in your root classpath folder and write c3p0.testConnectionOnCheckout=true c3p0.acquireRetryDelay=1000 c3p0.acquireRetryAttempts=1 I've tried to make those adjustments following the direction of the Play! Framework documentation, where they say use "db.pool..." as follows: db.pool.timeout=1800 db.pool.maxSize=15 db.pool.minSize=5 db.pool.initialSize=5 db.pool.acquireRetryAttempts=1 db.pool.preferredTestQuery=SELECT 1 db.pool.testConnectionOnCheckout=true db.pool.acquireRetryDelay=1000 db.pool.maxStatements=50 Are those settings not going to work? Should I be trying to set them in a different way? With those settings I still get the error shown below, that is due to to long of a idle time. Complete Stack Trace of Error: 23:00:44,932 WARN ~ SQL Error: 0, SQLState: 08S01 2012-04-13T23:00:44+00:00 app[web.1]: 23:00:44,932 ERROR ~ Communications link failure 2012-04-13T23:00:44+00:00 app[web.1]: 2012-04-13T23:00:44+00:00 app[web.1]: The last packet successfully received from the server was 274,847 milliseconds ago. The last packet sent successfully to the server was 7 milliseconds ago. 2012-04-13T23:00:44+00:00 app[web.1]: 23:00:44,934 ERROR ~ Why the driver complains here? 2012-04-13T23:00:44+00:00 app[web.1]: com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: No operations allowed after connection closed.Connection was implicitly closed by the driver. 2012-04-13T23:00:44+00:00 app[web.1]: at com.mysql.jdbc.Util.handleNewInstance(Util.java:407) 2012-04-13T23:00:44+00:00 app[web.1]: at com.mysql.jdbc.Util.getInstance(Util.java:382) 2012-04-13T23:00:44+00:00 app[web.1]: at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1013) 2012-04-13T23:00:44+00:00 app[web.1]: at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:987) 2012-04-13T23:00:44+00:00 app[web.1]: at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:982) 2012-04-13T23:00:44+00:00 app[web.1]: at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:927) 2012-04-13T23:00:44+00:00 app[web.1]: at com.mysql.jdbc.ConnectionImpl.throwConnectionClosedException(ConnectionImpl.java:1213) 2012-04-13T23:00:44+00:00 app[web.1]: at com.mysql.jdbc.ConnectionImpl.getMutex(ConnectionImpl.java:3101) 2012-04-13T23:00:44+00:00 app[web.1]: at com.mysql.jdbc.ConnectionImpl.setAutoCommit(ConnectionImpl.java:4975) 2012-04-13T23:00:44+00:00 app[web.1]: at org.hibernate.jdbc.BorrowedConnectionProxy.invoke(BorrowedConnectionProxy.java:74) 2012-04-13T23:00:44+00:00 app[web.1]: at $Proxy49.setAutoCommit(Unknown Source) 2012-04-13T23:00:44+00:00 app[web.1]: at play.db.jpa.JPAPlugin.closeTx(JPAPlugin.java:368) 2012-04-13T23:00:44+00:00 app[web.1]: at play.db.jpa.JPAPlugin.onInvocationException(JPAPlugin.java:328) 2012-04-13T23:00:44+00:00 app[web.1]: at play.plugins.PluginCollection.onInvocationException(PluginCollection.java:447) 2012-04-13T23:00:44+00:00 app[web.1]: at play.Invoker$Invocation.onException(Invoker.java:240) 2012-04-13T23:00:44+00:00 app[web.1]: at play.jobs.Job.onException(Job.java:124) 2012-04-13T23:00:44+00:00 app[web.1]: at play.jobs.Job.call(Job.java:163) 2012-04-13T23:00:44+00:00 app[web.1]: at play.jobs.Job$1.call(Job.java:66) 2012-04-13T23:00:44+00:00 app[web.1]: at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334) 2012-04-13T23:00:44+00:00 app[web.1]: at java.util.concurrent.FutureTask.run(FutureTask.java:166) 2012-04-13T23:00:44+00:00 app[web.1]: at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$101(ScheduledThreadPoolExecutor.java:165) 2012-04-13T23:00:44+00:00 app[web.1]: at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:266) 2012-04-13T23:00:44+00:00 app[web.1]: at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110) 2012-04-13T23:00:44+00:00 app[web.1]: at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603) 2012-04-13T23:00:44+00:00 app[web.1]: at java.lang.Thread.run(Thread.java:636) 2012-04-13T23:00:44+00:00 app[web.1]: Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

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  • Save memory in Python. How to iterate over the lines and save them efficiently with a 2million line

    - by skyl
    I have a tab-separated data file with a little over 2 million lines and 19 columns. You can find it, in US.zip: http://download.geonames.org/export/dump/. I started to run the following but with for l in f.readlines(). I understand that just iterating over the file is supposed to be more efficient so I'm posting that below. Still, with this small optimization, I'm using 10% of my memory on the process and have only done about 3% of the records. It looks like, at this pace, it will run out of memory like it did before. Also, the function I have is very slow. Is there anything obvious I can do to speed it up? Would it help to del the objects with each pass of the for loop? def run(): from geonames.models import POI f = file('data/US.txt') for l in f: li = l.split('\t') try: p = POI() p.geonameid = li[0] p.name = li[1] p.asciiname = li[2] p.alternatenames = li[3] p.point = "POINT(%s %s)" % (li[5], li[4]) p.feature_class = li[6] p.feature_code = li[7] p.country_code = li[8] p.ccs2 = li[9] p.admin1_code = li[10] p.admin2_code = li[11] p.admin3_code = li[12] p.admin4_code = li[13] p.population = li[14] p.elevation = li[15] p.gtopo30 = li[16] p.timezone = li[17] p.modification_date = li[18] p.save() except IndexError: pass if __name__ == "__main__": run()

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  • MsSql Server high Resource Waits and Head Blocker

    - by MartinHN
    Hi I have a MS SQL Server 2008 Standard installation running a database for a webshop. The current size of the database is 2.5 GB. Running on Windows 2008 Standard. Dual Intel Xeon X5355 @ 2.00 GHz. 4 GB RAM. When I open the Activity Monitor, I see that I have a Wait Time (ms/sec) of 5000 in the "Other" category. In the Processes list, all connections from the webshop, the Head Blocker value is 1. I see every day that when I try to access the website, it can take 20-30 secs before it even starts to "work". I know that it is not network latency. (I have a 301 redirect from the same server that is executed instantly). When the first request has been served, it seems as if it's not a sleep anymore and every subsequent request is served instantly with the speed of light. The problem was worse two weeks ago, until I changed every query to include WITH (NOLOCK). But I still experience the problem, and the Wait times in the Activity Monitor is about the same. The largest table (Images) has 32764 rows (448576 KB). Some tables exceed 300000 rows, thought they're much smaller in size than the Images table. I have the default clustered index for every primary key column, only. Any ideas?

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  • Combining cache methods - memcache/disk based

    - by Industrial
    Hi! Here's the deal. We would have taken the complete static html road to solve performance issues, but since the site will be partially dynamic, this won't work out for us. What we have thought of instead is using memcache + eAccelerator to speed up PHP and take care of caching for the most used data. Here's our two approaches that we have thought of right now: Using memcache on all<< major queries and leaving it alone to do what it does best. Usinc memcache for most commonly retrieved data, and combining with a standard harddrive-stored cache for further usage. The major advantage of only using memcache is of course the performance, but as users increases, the memory usage gets heavy. Combining the two sounds like a more natural approach to us, even though the theoretical compromize in performance. Memcached appears to have some replication features available as well, which may come handy when it's time to increase the nodes. What approach should we use? - Is it stupid to compromize and combine the two methods? Should we insted be focusing on utilizing memcache and instead focusing on upgrading the memory as the load increases with the number of users? Thanks a lot!

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  • Android Google-Shopping API force closes while parsing

    - by Sam Jackson
    I'm trying to send a request to the Google-Shopping API with the following static method which I think is working: public static String GET_TITLE(String url) throws JSONException { InputStream is = null; String result = ""; JSONObject jArray = null; // http post try { HttpClient httpclient = new DefaultHttpClient(); HttpPost httppost = new HttpPost(url); HttpResponse response = httpclient.execute(httppost); HttpEntity entity = response.getEntity(); is = entity.getContent(); } catch(Exception e) { Log.e("log_tag", "Error in http connection "+e.toString()); } The URL I'm passing is this BTW: https://www.googleapis.com/shopping/search/v1/public/products/country=US&q=shirts&alt=json &rankBy=relevancy&key=AIzaSyDRKgGmJrdG6pV6DIg2m-nmIbXydxvpjww Next I try to parse this response (where I think the problem comes in) in the same method: try { jArray = new JSONObject(result); } catch(JSONException e){ Log.e("log_tag", "Error parsing data "+e.toString()); } JSONObject itemObject = jArray.getJSONObject("items"); JSONObject productObject = itemObject.getJSONObject("product"); String attributeGoogleId = productObject.getString("googleId"); String attributeProviderId = productObject.getString("providerId"); String attributeTitle = productObject.getString("title");*/ String attributePrice = productObject.getString("price"); JSONObject popupObject = productObject.getJSONObject("popup"); return attributeTitle; } This has been so frustrating, I know it should be simple but everywhere I look I just can't quite get it to work, I'm not exactly sure what the error is since I'm testing it on my HTC Desire because my emulator gives an 'invalid command-line parameter' error when starting, but that's a different issue, anyway, thanks in advance! EDIT: The first one makes it look like there's a problem with the URL, should I change it and see if it makes a difference? 04-01 12:09:05.142: ERROR/log_tag(24968): Error in http connection java.net.UnknownHostException: www.googleapis.com 04-01 12:09:05.142: ERROR/log_tag(24968): Error converting result java.lang.NullPointerException 04-01 12:09:05.142: ERROR/log_tag(24968): Error parsing data org.json.JSONException: End of input at character 0 of 04-01 12:09:05.142: DEBUG/AndroidRuntime(24968): Shutting down VM 04-01 12:09:05.142: WARN/dalvikvm(24968): threadid=1: thread exiting with uncaught exception (group=0x400259f8) 04-01 12:09:05.152: ERROR/AndroidRuntime(24968): FATAL EXCEPTION: main 04-01 12:09:05.152: ERROR/AndroidRuntime(24968): java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=0, result=-1, data=Intent { act=com.google.zxing.client.android.SCAN flg=0x80000 (has extras) }} to activity {com.spectrum.stock/com.spectrum.stock.CaptureActivity}: java.lang.NullPointerException 04-01 12:09:05.152: ERROR/AndroidRuntime(24968): at android.app.ActivityThread.deliverResults(ActivityThread.java:3734) 04-01 12:09:05.152: ERROR/AndroidRuntime(24968): at android.app.ActivityThread.handleSendResult(ActivityThread.java:3776) 04-01 12:09:05.152: ERROR/AndroidRuntime(24968): at android.app.ActivityThread.access$2800(ActivityThread.java:135) 04-01 12:09:05.152: ERROR/AndroidRuntime(24968): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2166) 04-01 12:09:05.152: ERROR/AndroidRuntime(24968): at android.os.Handler.dispatchMessage(Handler.java:99) 04-01 12:09:05.152: ERROR/AndroidRuntime(24968): at android.os.Looper.loop(Looper.java:144) 04-01 12:09:05.152: ERROR/AndroidRuntime(24968): at android.app.ActivityThread.main(ActivityThread.java:4937) 04-01 12:09:05.152: ERROR/AndroidRuntime(24968): at java.lang.reflect.Method.invokeNative(Native Method) 04-01 12:09:05.152: ERROR/AndroidRuntime(24968): at java.lang.reflect.Method.invoke(Method.java:521) 04-01 12:09:05.152: ERROR/AndroidRuntime(24968): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868) 04-01 12:09:05.152: ERROR/AndroidRuntime(24968): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626) 04-01 12:09:05.152: ERROR/AndroidRuntime(24968): at dalvik.system.NativeStart.main(Native Method) 04-01 12:09:05.152: ERROR/AndroidRuntime(24968): Caused by: java.lang.NullPointerException 04-01 12:09:05.152: ERROR/AndroidRuntime(24968): at com.spectrum.stock.JSONResponse.GET_TITLE(JSONResponse.java:61) 04-01 12:09:05.152: ERROR/AndroidRuntime(24968): at com.spectrum.stock.CaptureActivity.onActivityResult(CaptureActivity.java:78) 04-01 12:09:05.152: ERROR/AndroidRuntime(24968): at android.app.Activity.dispatchActivityResult(Activity.java:3931) 04-01 12:09:05.152: ERROR/AndroidRuntime(24968): at android.app.ActivityThread.deliverResults(ActivityThread.java:3730) 04-01 12:09:05.152: ERROR/AndroidRuntime(24968): ... 11 more 04-01 12:09:05.162: WARN/ActivityManager(96): Force finishing activity com.spectrum.stock/.CaptureActivity

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  • Is it wise to use temporary tables?

    - by Industrial
    Hi guys, We have a mySQL database table for products. We are utilizing a cache layer to reduce database load, but we think that it's a good idea to minimize the actual data needed to be stored in the cache layer to speed up the application further. All the products in the database, that is visible to visitors have a price attached to them: The prices are stored in a different table, called prices . There are multiple price categories depending on which discount level each visitor (customer) applies to. From time to time, there are campaigns which means that a special price for each product is available. The special prices are stored in a table called specials. Is it a bad to make a temp table that binds the tables together? It would only have the neccessary information and would ofcourse be cached. -------------|-------------|------------ | productId | hasPrice | hasSpecial -------------|-------------|------------ 1 | 1 | 0 2 | 1 | 1 By doing such, it would be super easy to know if the specific product really has a price, without having to iterate through the complete prices or specials table each time a product should be listed or presented. Are temp tables a common thing for web applications or is it just bad design?

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  • NHibernate slow mapping

    - by Rob A
    My question is what can I do to determine the cause of the slowness, or what can I do to speed it up without knowing the exact cause. I am running a simple query and it appears that the mapping back to the entities is taking taking forever. The result set is 350, which is not much data in my opinion. IRepository repo = ObjectFactory.GetInstance<IRepository>(); var q = repo.Query<Order>(item => item.Ordereddate > DateTime.Now.AddDays(-40)); foreach (var order in q) { Console.WriteLine(order.TransactionNumber); } The profiler is telling me it is executing the query 7ms / 35257ms, I am assuming that the former is the actual response from the db and the latter is the time it takes NH to do it's magic. 35 seconds is too long. This is a simple mapping, one table, nested components, using fluent interface to do mappings. I just start up a simple console app and run the one query, the slowness is measured after the SessionFactory is initialized, there should only be one session, and I am not using a transaction. Thanks

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  • How can I superimpose modified loess lines on a ggplot2 qplot?

    - by briandk
    Background Right now, I'm creating a multiple-predictor linear model and generating diagnostic plots to assess regression assumptions. (It's for a multiple regression analysis stats class that I'm loving at the moment :-) My textbook (Cohen, Cohen, West, and Aiken 2003) recommends plotting each predictor against the residuals to make sure that: The residuals don't systematically covary with the predictor The residuals are homoscedastic with respect to each predictor in the model On point (2), my textbook has this to say: Some statistical packages allow the analyst to plot lowess fit lines at the mean of the residuals (0-line), 1 standard deviation above the mean, and 1 standard deviation below the mean of the residuals....In the present case {their example}, the two lines {mean + 1sd and mean - 1sd} remain roughly parallel to the lowess {0} line, consistent with the interpretation that the variance of the residuals does not change as a function of X. (p. 131) How can I modify loess lines? I know how to generate a scatterplot with a "0-line,": # First, I'll make a simple linear model and get its diagnostic stats library(ggplot2) data(cars) mod <- fortify(lm(speed ~ dist, data = cars)) attach(mod) str(mod) # Now I want to make sure the residuals are homoscedastic qplot (x = dist, y = .resid, data = mod) + geom_smooth(se = FALSE) # "se = FALSE" Removes the standard error bands But does anyone know how I can use ggplot2 and qplot to generate plots where the 0-line, "mean + 1sd" AND "mean - 1sd" lines would be superimposed? Is that a weird/complex question to be asking?

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  • Reading same file from multiple threads in C#

    - by Gustavo Rubio
    Hi. I was googling for some advise about this and I found some links. The most obvious was this one but in the end what im wondering is how well my code is implemented. I have basically two classes. One is the Converter and the other is ConverterThread I create an instance of this Converter class that has a property ThreadNumber that tells me how many threads should be run at the same time (this is read from user) since this application will be used on multi-cpu systems (physically, like 8 cpu) so it is suppossed that this will speed up the import The Converter instance reads a file that can range from 100mb to 800mb and each line of this file is a tab-delimitted value record that is imported to another destination like a database. The ConverterThread class simply runs inside the thread (new Thread(ConverterThread.StartThread)) and has event notification so when its work is done it can notify the Converter class and then I can sum up the progress for all these threads and notify the user (in the GUI for example) about how many of these records have been imported and how many bytes have been read. It seems, however that I'm having some trouble because I get random errors about the file not being able to be read or that the sum of the progress (percentage) went above 100% which is not possible and I think that happens because threads are not being well managed and probably the information returned by the event is malformed (since it "travels" from one thread to another) Do you have any advise on better practices of implementation of threads so I can accomplish this? Thanks in advance.

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  • HttpClient multithread performance

    - by pepper
    I have an application which downloads more than 4500 html pages from 62 target hosts using HttpClient (4.1.3 or 4.2-beta). It runs on Windows 7 64-bit. Processor - Core i7 2600K. Network bandwidth - 54 Mb/s. At this moment it uses such parameters: DefaultHttpClient and PoolingClientConnectionManager; Also it hasIdleConnectionMonitorThread from http://hc.apache.org/httpcomponents-client-ga/tutorial/html/connmgmt.html; Maximum total connections = 80; Default maximum connections per route = 5; For thread management it uses ForkJoinPool with the parallelism level = 5 (Do I understand correctly that it is a number of working threads?) In this case my network usage (in Windows task manager) does not rise above 2.5%. To download 4500 pages it takes 70 minutes. And in HttpClient logs I have such things: DEBUG ForkJoinPool-2-worker-1 [org.apache.http.impl.conn.PoolingClientConnectionManager]: Connection released: [id: 209][route: {}-http://stackoverflow.com][total kept alive: 6; route allocated: 1 of 5; total allocated: 10 of 80] Total allocated connections do not raise above 10-12, in spite of that I've set it up to 80 connections. If I'll try to rise parallelism level to 20 or 80, network usage remains the same but a lot connection time-outs will be generated. I've read tutorials on hc.apache.org (HttpClient Performance Optimization Guide and HttpClient Threading Guide) but they does not help. Task's code looks like this: public class ContentDownloader extends RecursiveAction { private final HttpClient httpClient; private final HttpContext context; private List<Entry> entries; public ContentDownloader(HttpClient httpClient, List<Entry> entries){ this.httpClient = httpClient; context = new BasicHttpContext(); this.entries = entries; } private void computeDirectly(Entry entry){ final HttpGet get = new HttpGet(entry.getLink()); try { HttpResponse response = httpClient.execute(get, context); int statusCode = response.getStatusLine().getStatusCode(); if ( (statusCode >= 400) && (statusCode <= 600) ) { logger.error("Couldn't get content from " + get.getURI().toString() + "\n" + response.toString()); } else { HttpEntity entity = response.getEntity(); if (entity != null) { String htmlContent = EntityUtils.toString(entity).trim(); entry.setHtml(htmlContent); EntityUtils.consumeQuietly(entity); } } } catch (Exception e) { } finally { get.releaseConnection(); } } @Override protected void compute() { if (entries.size() <= 1){ computeDirectly(entries.get(0)); return; } int split = entries.size() / 2; invokeAll(new ContentDownloader(httpClient, entries.subList(0, split)), new ContentDownloader(httpClient, entries.subList(split, entries.size()))); } } And the question is - what is the best practice to use multi threaded HttpClient, may be there is a some rules for setting up ConnectionManager and HttpClient? How can I use all of 80 connections and raise network usage? If necessary, I will provide more code.

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  • Unable to browse some pdfs and docs.

    - by JamesEggers
    I have a web site that uses Microsoft Indexing Service to index and query a directory that holds various documents of type pdf, rtf, mht, and doc. The indexing and querying works well (for the most part); however, some files will load while others will not. This is a Windows Server 2003 box running the site using IIS 6. The indexed directory is a sub directory off of the site's root directory (i.e. http://my.domain.com/files/). The file paths are accurate in the URL; however, I can only access some of the files of each file type. The files that I cannot access give a 404 File Not Found. I am able to open all files via windows explorer;however, attempting to open them via a browser over http is hit and miss. Has anyone experienced this issue and know how to resolve it? Anyone have any idea why I could access some files but not others? Does anyone have any recommendations on what to look into to try this (i.e. does owner matter or something like that?)? EDIT: Here is the Request and Response Headers for a bad file: GET /files/file1.pdf HTTP/1.1 Accept: image/gif, image/jpeg, image/pjpeg, image/pjpeg, application/x-shockwave-flash, application/xaml+xml, application/vnd.ms-xpsdocument, application/x-ms-xbap, application/x-ms-application, application/x-silverlight, application/vnd.ms-excel, application/vnd.ms-powerpoint, application/msword, / Accept-Language: en-us User-Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.04506.30; .NET CLR 3.0.04506.590; .NET CLR 3.0.04506.648; .NET CLR 3.5.21022; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729) Accept-Encoding: gzip, deflate Proxy-Connection: Keep-Alive Host: my.domain.com HTTP/1.1 404 Not Found Content-Length: 1635 Content-Type: text/html Server: Microsoft-IIS/6.0 X-Powered-By: ASP.NET Date: Mon, 01 Jun 2009 15:38:54 GMT [typical 404 page markup excluded] Here is the Request/Response headers for the good file: GET /files/file2.pdf HTTP/1.1 Accept: image/gif, image/jpeg, image/pjpeg, image/pjpeg, application/x-shockwave-flash, application/xaml+xml, application/vnd.ms-xpsdocument, application/x-ms-xbap, application/x-ms-application, application/x-silverlight, application/vnd.ms-excel, application/vnd.ms-powerpoint, application/msword, / Accept-Language: en-us User-Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.04506.30; .NET CLR 3.0.04506.590; .NET CLR 3.0.04506.648; .NET CLR 3.5.21022; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729) Accept-Encoding: gzip, deflate Proxy-Connection: Keep-Alive Host: my.domain.com HTTP/1.1 200 OK Content-Length: 352464 Content-Type: application/pdf Last-Modified: Tue, 13 Jan 2009 15:27:35 GMT Accept-Ranges: bytes ETag: "74ccc5759375c91:2a47" Server: Microsoft-IIS/6.0 X-Powered-By: ASP.NET Date: Mon, 01 Jun 2009 15:50:33 GMT

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  • jQuery Cycle : Multiple Instances, detect end of each instance

    - by guylabbe.ca
    I am using multiple instances of Cycle for a portfolio; Only one is shown and the others are hidden. Each Cycle is a project with multiple images. The only thing I can't figure out is how to detect the end of the « current » Cycle instance. with after: function, it is triggered for all instances at once, impossible to get « local » events. Here is my code : $('.sldr_closeup').each(function() { var currId = $(this).attr('id'); window['num_'+currId] = 0; $(this).cycle({ timeout:0, speed:500, fx:'fade', next:'.nextimages', prev:'.previmages', fit:1, nowrap:1, autstop:0, after : function(c,n,o,f) { var currId = $(this).parent('div').attr('id'); (f) ? window['num_'+currId] ++ : window['num_'+currId] --; if ((o.slideCount == window['num_'+currId] )) { alert(currId); $('.nextimages').stop().fadeTo(400,0,function(){ if(currId != $('.projectList .projet').last().find('a').attr('rel')) $('.nextproject').stop().fadeTo(400,1); $(this).hide(); }); } } }).cycle('pause'); });

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  • How do I use IPTC/EXIF metadata to categorise photos?

    - by kbro
    Many photo viewing and editing applications allow you to examine and change EXIF and IPTC data in JPEG and other image files. For example, I can see things like shutter speed, aperture and orientation in the picture files that come off my Canon A430. There are many, many name/value pairs in all this metadata. But... What do I do if I want to store some data that doesn't have a build-in field name. Let's say I'm photographing an athletics competition and I want to tag every photo with the competitor's bib number. Can I create a "bib_number" field and assign it a values of "0001", "5478", "8124" etc, and then search for all photos with bib_number="5478"? I've spent a few hours searching and the best I can come up with is to put this custom information in the "keywords" field but this isn't quite what I'm after. With this socution I'd have to craft a query like "keywords contains bib_number_5478" whereas what I want it "bib_number is 5478". So do the EXIF and/or IPTC standards allow addtional user-defined field names? Thanks Kev

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  • Helping Rails Newbies identify version-specific information on web pages

    - by corprew
    I am trying to help some people getting started programming on rails identify which version that advice found on web pages corresponds to, and am seeking advice and/or guides on how to do it so they don't have to rely on me and/or waste time trying outdated advice. Narrative: I am helping some people get up to speed on rails development, and their stock response to running into problems is searching google for advice. They're using 2.3.5 and thinking of moving to 3. The problem they're running into is that there's a lot of advice out there specific to older rails versions (2.2 for example being popular) that isn't identified. I can usually figure out when the pages are old pretty easily, but they can't (yet.) It seems like random web page authors don't identify which version they're using when they're using the current version, and not all pages are dated. This seems to be a general problem that will get worse -- current unadorned advice is usually 2.3.5 and older unadorned advice is 2.2.x at this point, but people are moving / will be moving to version 3 over the next while and newbies will be stuck looking at a bunch of deprecated/incompatible 2.3.x advice without realizing which version it is. Any advice / pointers / telltales?

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