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  • Windows 2003 Server Caching

    - by pablomedok
    We're experiencing almost everyday table index corruption on Windows Server 2003. We are running an old application which uses DBF/CDX tables. Everything was fine for ages, but 6 months after we've installed Advantage Database Server (which allows access to some tables to our website) we started to get index corruption problems. And we don't know whom to blame. We've tried to exclude all possible causes of this corruption. Now all users work in terminal mode - so no network problems can cause that, OpLocks also can't be a reason. We changed hardware, network cards, switches, reainstalled Server and even moved to new dedicated server. The only thing we can't exclude is ADS - because it should be working. Is that possible that local read/write caching that causes that problem? E.g. one user or process uses cached data, later another user/process changes it, and later the first user changes it again without knowing about the first change. Is it possible theoretically? Is it possible that this problem is caused by imporper file server or caching settings? Is it possible that normal users use non-cached data and ADS is using cached data? Or vice versa? Is it possible that each terminal user has its own cache? Or maybe the problem is about RAID caching somehow interfering with Windows Server caching? Or maybe there are some special settings for Windows Server for working with DBF tables that are being written simultaneously by several terminal users? Maybe there is a way to turn off caching for some certain files to check it? Sometimes we get index crash twice a day, sometimes everything is fine for 5 days in a row. Today only one user was working in the evening with the database (usually there are 30-50 users are working simultaneously on working hours). So it's almost zero load on server. , Syncronization with website is performed every 5 minutes during work hours and every 15 minutes in the evening and on weekend. We've done file access auditing and it shows that during website syncroniztions ADS server opens the table and index files for ReadEA and WriteEA though it performs only SELECT queries. ADS does UPDATE/INSERT queries but less freqently - not during regular synchronizations, but only when an order is placed by website visitor). Please help me. We are struggling with this problem for almost a year and still can't find any pattern or any clue about this problem. Here is my previous qestion about this issue on DBA: http://dba.stackexchange.com/questions/8646/foxpro-dbf-index-corruption

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  • Cache Simulator in C

    - by DuffDuff
    Ok this is only my second question, and it's quite a doozy. It's for a school assignment, but no one (including the TAs) seems to be able to help me. It's kind of a tall order but I'm not sure where else to turn. Essentially the assignment was to make a cache simulator. This version is direct mapping and is actually only a small portion of the whole project, but if I can't even get this down I have no chance with other associativities. I'm posting my whole code because I don't want to make any assumptions about where the problem is. This is the test case: http://www.mediafire.com/?ty5dnihydnw And you run the following command: ./sims 512 direct 32 fifo wt pinatrace.out You're supposed to get: hits: 604037 misses 138349 writes: 239269 reads: 138349 But I get: Hits: 587148 Misses: 155222 Writes: 239261 Reads: 155222 If anyone could at least point me in the right direction it would be greatly appreciated. I've been stuck on this for about 12 hours. #include <stdio.h> #include <stdlib.h> #include <string.h> #include <math.h> struct myCache { int valid; char *tag; char *block; }; /* sim [-h] <cache size> <associativity> <block size> <replace alg> <write policy> <trace file> */ //God willing I come up with a better Hex to Bin convertion that maintains the beginning 0s... void hex2bin(char input[], char output[]) { int i; int a = 0; int b = 1; int c = 2; int d = 3; int x = 4; int size; size = strlen(input); for (i = 0; i < size; i++) { if (input[i] =='0') { output[i*x +a] = '0'; output[i*x +b] = '0'; output[i*x +c] = '0'; output[i*x +d] = '0'; } else if (input[i] =='1') { output[i*x +a] = '0'; output[i*x +b] = '0'; output[i*x +c] = '0'; output[i*x +d] = '1'; } else if (input[i] =='2') { output[i*x +a] = '0'; output[i*x +b] = '0'; output[i*x +c] = '1'; output[i*x +d] = '0'; } else if (input[i] =='3') { output[i*x +a] = '0'; output[i*x +b] = '0'; output[i*x +c] = '1'; output[i*x +d] = '1'; } else if (input[i] =='x') { output[i*x +a] = '0'; output[i*x +b] = '1'; output[i*x +c] = '0'; output[i*x +d] = '0'; } else if (input[i] =='5') { output[i*x +a] = '0'; output[i*x +b] = '1'; output[i*x +c] = '0'; output[i*x +d] = '1'; } else if (input[i] =='6') { output[i*x +a] = '0'; output[i*x +b] = '1'; output[i*x +c] = '1'; output[i*x +d] = '0'; } else if (input[i] =='7') { output[i*x +a] = '0'; output[i*x +b] = '1'; output[i*x +c] = '1'; output[i*x +d] = '1'; } else if (input[i] =='8') { output[i*x +a] = '1'; output[i*x +b] = '0'; output[i*x +c] = '0'; output[i*x +d] = '0'; } else if (input[i] =='9') { output[i*x +a] = '1'; output[i*x +b] = '0'; output[i*x +c] = '0'; output[i*x +d] = '1'; } else if (input[i] =='a') { output[i*x +a] = '1'; output[i*x +b] = '0'; output[i*x +c] = '1'; output[i*x +d] = '0'; } else if (input[i] =='b') { output[i*x +a] = '1'; output[i*x +b] = '0'; output[i*x +c] = '1'; output[i*x +d] = '1'; } else if (input[i] =='c') { output[i*x +a] = '1'; output[i*x +b] = '1'; output[i*x +c] = '0'; output[i*x +d] = '0'; } else if (input[i] =='d') { output[i*x +a] = '1'; output[i*x +b] = '1'; output[i*x +c] = '0'; output[i*x +d] = '1'; } else if (input[i] =='e') { output[i*x +a] = '1'; output[i*x +b] = '1'; output[i*x +c] = '1'; output[i*x +d] = '0'; } else if (input[i] =='f') { output[i*x +a] = '1'; output[i*x +b] = '1'; output[i*x +c] = '1'; output[i*x +d] = '1'; } } output[32] = '\0'; } int main(int argc, char* argv[]) { FILE *tracefile; char readwrite; int trash; int cachesize; int blocksize; int setnumber; int blockbytes; int setbits; int blockbits; int tagsize; int m; int count = 0; int count2 = 0; int count3 = 0; int i; int j; int xindex; int jindex; int kindex; int lindex; int setadd; int totalset; int writeMiss = 0; int writeHit = 0; int cacheMiss = 0; int cacheHit = 0; int read = 0; int write = 0; int size; int extra; char bbits[100]; char sbits[100]; char tbits[100]; char output[100]; char input[100]; char origtag[100]; if (argc != 7) { if (strcmp(argv[0], "-h")) { printf("./sim2 <cache size> <associativity> <block size> <replace alg> <write policy> <trace file>\n"); return 0; } else { fprintf(stderr, "Error: wrong number of parameters.\n"); return -1; } } tracefile = fopen(argv[6], "r"); if(tracefile == NULL) { fprintf(stderr, "Error: File is NULL.\n"); return -1; } //Determining size of sbits, bbits, and tag cachesize = atoi(argv[1]); blocksize = atoi(argv[3]); setnumber = (cachesize/blocksize); printf("setnumber: %d\n", setnumber); setbits = (round((log(setnumber))/(log(2)))); printf("sbits: %d\n", setbits); blockbits = log(blocksize)/log(2); printf("bbits: %d\n", blockbits); tagsize = 32 - (blockbits + setbits); printf("t: %d\n", tagsize); struct myCache newCache[setnumber]; //Allocating Space for Tag Bits, initiating tag and valid to 0s for(i=0;i<setnumber;i++) { newCache[i].tag = (char *)malloc(sizeof(char)*(tagsize+1)); for(j=0;j<tagsize;j++) { newCache[i].tag[j] = '0'; } newCache[i].valid = 0; } while(fgetc(tracefile)!='#') { setadd = 0; totalset = 0; //read in file fseek(tracefile,-1,SEEK_CUR); fscanf(tracefile, "%x: %c %s\n", &trash, &readwrite, origtag); //shift input Hex size = strlen(origtag); extra = (10 - size); for(i=0; i<extra; i++) input[i] = '0'; for(i=extra, j=0; i<(size-(2-extra)); j++, i++) input[i]=origtag[j+2]; input[8] = '\0'; // Convert Hex to Binary hex2bin(input, output); //Resolving the Address into tbits, sbits, bbits for (xindex=0, jindex=(32-blockbits); jindex<32; jindex++, xindex++) { bbits[xindex] = output[jindex]; } bbits[xindex]='\0'; for (xindex=0, kindex=(32-(blockbits+setbits)); kindex<32-(blockbits); kindex++, xindex++){ sbits[xindex] = output[kindex]; } sbits[xindex]='\0'; for (xindex=0, lindex=0; lindex<(32-(blockbits+setbits)); lindex++, xindex++){ tbits[xindex] = output[lindex]; } tbits[xindex]='\0'; //Convert set bits from char array into ints for(xindex = 0, kindex = (setbits -1); xindex < setbits; xindex ++, kindex--) { if (sbits[xindex] == '1') setadd = 1; if (sbits[xindex] == '0') setadd = 0; setadd = setadd * pow(2, kindex); totalset += setadd; } //Calculating Hits and Misses if (newCache[totalset].valid == 0) { newCache[totalset].valid = 1; strcpy(newCache[totalset].tag, tbits); } else if (newCache[totalset].valid == 1) { if(strcmp(newCache[totalset].tag, tbits) == 0) { if (readwrite == 'W') { cacheHit++; write++; } if (readwrite == 'R') cacheHit++; } else { if (readwrite == 'R') { cacheMiss++; read++; } if (readwrite == 'W') { cacheMiss++; read++; write++; } strcpy(newCache[totalset].tag, tbits); } } } printf("Hits: %d\n", cacheHit); printf("Misses: %d\n", cacheMiss); printf("Writes: %d\n", write); printf("Reads: %d\n", read); }

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  • Axis Aligned Billboard: how to make the object look at camera

    - by user19787
    I am trying to make an Axis Aligned Billboard with Pyglet. I have looked at several tutorials, but they only show me how to get the Up,Right,and Look vectors. So far this is what I have: target = cam.pos look = norm( target - billboard.pos ) right = norm( Vector3(0,1,0)*look ) up = look*right gluLookAt( look.x, look.y, look.z, self.pos.x, self.pos.y, self.pos.z, up.x, up.y, up.z ) This does nothing for me visibly. Any idea what I'm doing wrong?

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  • Load and Web Performance Testing using Visual Studio Ultimate 2010-Part 3

    - by Tarun Arora
    Welcome back once again, in Part 1 of Load and Web Performance Testing using Visual Studio 2010 I talked about why Performance Testing the application is important, the test tools available in Visual Studio Ultimate 2010 and various test rig topologies, in Part 2 of Load and Web Performance Testing using Visual Studio 2010 I discussed the details of web performance & load tests as well as why it’s important to follow a goal based pattern while performance testing your application. In part 3 I’ll be discussing Test Result Analysis, Test Result Drill through, Test Report Generation, Test Run Comparison, Asp.net Profiler and some closing thoughts. Test Results – I see some creepy worms! In Part 2 we put together a web performance test and a load test, lets run the test to see load test to see how the Web site responds to the load simulation. While the load test is running you will be able to see close to real time analysis in the Load Test Analyser window. You can use the Load Test Analyser to conduct load test analysis in three ways: Monitor a running load test - A condensed set of the performance counter data is maintained in memory. To prevent the results memory requirements from growing unbounded, up to 200 samples for each performance counter are maintained. This includes 100 evenly spaced samples that span the current elapsed time of the run and the most recent 100 samples.         After the load test run is completed - The test controller spools all collected performance counter data to a database while the test is running. Additional data, such as timing details and error details, is loaded into the database when the test completes. The performance data for a completed test is loaded from the database and analysed by the Load Test Analyser. Below you can see a screen shot of the summary view, this provides key results in a format that is compact and easy to read. You can also print the load test summary, this is generated after the test has completed or been stopped.         Analyse the load test results of a previously run load test – We’ll see this in the section where i discuss comparison between two test runs. The performance counters can be plotted on the graphs. You also have the option to highlight a selected part of the test and view details, drill down to the user activity chart where you can hover over to see more details of the test run.   Generate Report => Test Run Comparisons The level of reports you can generate using the Load Test Analyser is astonishing. You have the option to create excel reports and conduct side by side analysis of two test results or to track trend analysis. The tools also allows you to export the graph data either to MS Excel or to a CSV file. You can view the ASP.NET profiler report to conduct further analysis as well. View Data and Diagnostic Attachments opens the Choose Diagnostic Data Adapter Attachment dialog box to select an adapter to analyse the result type. For example, you can select an IntelliTrace adapter, click OK and open the IntelliTrace summary for the test agent that was used in the load test.   Compare results This creates a set of reports that compares the data from two load test results using tables and bar charts. I have taken these screen shots from the MSDN documentation, I would highly recommend exploring the wealth of knowledge available on MSDN. Leaving Thoughts While load testing the application with an excessive load for a longer duration of time, i managed to bring the IIS to its knees by piling up a huge queue of requests waiting to be processed. This clearly means that the IIS had run out of threads as all the threads were busy processing existing request, one easy way of fixing this is by increasing the default number of allocated threads, but this might escalate the problem. The better suggestion is to try and drill down to the actual root cause of the problem. When ever the garbage collection runs it stops processing any pages so all requests that come in during that period are queued up, but realistically the garbage collection completes in fraction of a a second. To understand this better lets look at the .net heap, it is divided into large heap and small heap, anything greater than 85kB in size will be allocated to the Large object heap, the Large object heap is non compacting and remember large objects are expensive to move around, so if you are allocating something in the large object heap, make sure that you really need it! The small object heap on the other hand is divided into generations, so all objects that are supposed to be short-lived are suppose to live in Gen-0 and the long living objects eventually move to Gen-2 as garbage collection goes through.  As you can see in the picture below all < 85 KB size objects are first assigned to Gen-0, when Gen-0 fills up and a new object comes in and finds Gen-0 full, the garbage collection process is started, the process checks for all the dead objects and assigns them as the valid candidate for deletion to free up memory and promotes all the remaining objects in Gen-0 to Gen-1. So in the future when ever you clean up Gen-1 you have to clean up Gen-0 as well. When you fill up Gen – 0 again, all of Gen – 1 dead objects are drenched and rest are moved to Gen-2 and Gen-0 objects are moved to Gen-1 to free up Gen-0, but by this time your Garbage collection process has started to take much more time than it usually takes. Now as I mentioned earlier when garbage collection is being run all page requests that come in during that period are queued up. Does this explain why possibly page requests are getting queued up, apart from this it could also be the case that you are waiting for a long running database process to complete.      Lets explore the heap a bit more… What is really a case of crisis is when the objects are living long enough to make it to Gen-2 and then dying, this is definitely a high cost operation. But sometimes you need objects in memory, for example when you cache data you hold on to the objects because you need to use them right across the user session, which is acceptable. But if you wanted to see what extreme caching can do to your server then write a simple application that chucks in a lot of data in cache, run a load test over it for about 10-15 minutes, forcing a lot of data in memory causing the heap to run out of memory. If you get to such a state where you start running out of memory the IIS as a mode of recovery restarts the worker process. It is great way to free up all your memory in the heap but this would clear the cache. The problem with this is if the customer had 10 items in their shopping basket and that data was stored in the application cache, the user basket will now be empty forcing them either to get frustrated and go to a competitor website or if the customer is really patient, give it another try! How can you address this, well two ways of addressing this; 1. Workaround – A x86 bit processor only allows a maximum of 4GB of RAM, this means the machine effectively has around 3.4 GB of RAM available, the OS needs about 1.5 GB of RAM to run efficiently, the IIS and .net framework also need their share of memory, leaving you a heap of around 800 MB to play with. Because Team builds by default build your application in ‘Compile as any mode’ it means the application is build such that it will run in x86 bit mode if run on a x86 bit processor and run in a x64 bit mode if run on a x64 but processor. The problem with this is not all applications are really x64 bit compatible specially if you are using com objects or external libraries. So, as a quick win if you compiled your application in x86 bit mode by changing the compile as any selection to compile as x86 in the team build, you will be able to run your application on a x64 bit machine in x86 bit mode (WOW – By running Windows on Windows) and what that means is, you could use 8GB+ worth of RAM, if you take away everything else your application will roughly get a heap size of at least 4 GB to play with, which is immense. If you need a heap size of more than 4 GB you have either build a software for NASA or there is something fundamentally wrong in your application. 2. Solution – Now that you have put a workaround in place the IIS will not restart the worker process that regularly, which means you can take a breather and start working to get to the root cause of this memory leak. But this begs a question “How do I Identify possible memory leaks in my application?” Well i won’t say that there is one single tool that can tell you where the memory leak is, but trust me, ‘Performance Profiling’ is a great start point, it definitely gets you started in the right direction, let’s have a look at how. Performance Wizard - Start the Performance Wizard and select Instrumentation, this lets you measure function call counts and timings. Before running the performance session right click the performance session settings and chose properties from the context menu to bring up the Performance session properties page and as shown in the screen shot below, check the check boxes in the group ‘.NET memory profiling collection’ namely ‘Collect .NET object allocation information’ and ‘Also collect the .NET Object lifetime information’.    Now if you fire off the profiling session on your pages you will notice that the results allows you to view ‘Object Lifetime’ which shows you the number of objects that made it to Gen-0, Gen-1, Gen-2, Large heap, etc. Another great feature about the profile is that if your application has > 5% cases where objects die right after making to the Gen-2 storage a threshold alert is generated to alert you. Since you have the option to also view the most expensive methods and by capturing the IntelliTrace data you can drill in to narrow down to the line of code that is the root cause of the problem. Well now that we have seen how crucial memory management is and how easy Visual Studio Ultimate 2010 makes it for us to identify and reproduce the problem with the best of breed tools in the product. Caching One of the main ways to improve performance is Caching. Which basically means you tell the web server that instead of going to the database for each request you keep the data in the webserver and when the user asks for it you serve it from the webserver itself. BUT that can have consequences! Let’s look at some code, trust me caching code is not very intuitive, I define a cache key for almost all searches made through the common search page and cache the results. The approach works fine, first time i get the data from the database and second time data is served from the cache, significant performance improvement, EXCEPT when two users try to do the same operation and run into each other. But it is easy to handle this by adding the lock as you can see in the snippet below. So, as long as a user comes in and finds that the cache is empty, the user locks and starts to get the cache no more concurrency issues. But lets say you are processing 10 requests per second, by the time i have locked the operation to get the results from the database, 9 other users came in and found that the cache key is null so after i have come out and populated the cache they will still go in to get the results again. The application will still be faster because the next set of 10 users and so on would continue to get data from the cache. BUT if we added another null check after locking to build the cache and before actual call to the db then the 9 users who follow me would not make the extra trip to the database at all and that would really increase the performance, but didn’t i say that the code won’t be very intuitive, may be you should leave a comment you don’t want another developer to come in and think what a fresher why is he checking for the cache key null twice !!! The downside of caching is, you are storing the data outside of the database and the data could be wrong because the updates applied to the database would make the data cached at the web server out of sync. So, how do you invalidate the cache? Well if you only had one way of updating the data lets say only one entry point to the data update you can write some logic to say that every time new data is entered set the cache object to null. But this approach will not work as soon as you have several ways of feeding data to the system or your system is scaled out across a farm of web servers. The perfect solution to this is Micro Caching which means you cache the query for a set time duration and invalidate the cache after that set duration. The advantage is every time the user queries for that data with in the time span for which you have cached the results there are no calls made to the database and the data is served right from the server which makes the response immensely quick. Now figuring out the appropriate time span for which you micro cache the query results really depends on the application. Lets say your website gets 10 requests per second, if you retain the cache results for even 1 minute you will have immense performance gains. You would reduce 90% hits to the database for searching. Ever wondered why when you go to e-bookers.com or xpedia.com or yatra.com to book a flight and you click on the book button because the fare seems too exciting and you get an error message telling you that the fare is not valid any more. Yes, exactly => That is a cache failure! These travel sites or price compare engines are not going to hit the database every time you hit the compare button instead the results will be served from the cache, because the query results are micro cached, its a perfect trade-off, by micro caching the results the site gains 100% performance benefits but every once in a while annoys a customer because the fare has expired. But the trade off works in the favour of these sites as they are still able to process up to 30+ page requests per second which means cater to the site traffic by may be losing 1 customer every once in a while to a competitor who is also using a similar caching technique what are the odds that the user will not come back to their site sooner or later? Recap   Resources Below are some Key resource you might like to review. I would highly recommend the documentation, walkthroughs and videos available on MSDN. You can always make use of Fiddler to debug Web Performance Tests. Some community test extensions and plug ins available on Codeplex might also be of interest to you. The Road Ahead Thank you for taking the time out and reading this blog post, you may also want to read Part I and Part II if you haven’t so far. If you enjoyed the post, remember to subscribe to http://feeds.feedburner.com/TarunArora. Questions/Feedback/Suggestions, etc please leave a comment. Next ‘Load Testing in the cloud’, I’ll be working on exploring the possibilities of running Test controller/Agents in the Cloud. See you on the other side! Thank You!   Share this post : CodeProject

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  • How do I draw a border around a display object in Corona Lua?

    - by Greg
    What would be the easiest way to draw a thin border around a display object in Corona Lua? You could assume it's rectangular image display object. EDIT - re "this question shows no research effort. You should tell us what you've tried and how it didn't work" Reviewed API and could not find a "border" method/property on displayObject Have tried creating a black box slightly bigger behind object, however can not see how to place object behind an existing object hence question How do I move an existing display object behind another in Corona Lua? Google results for putting a border around a display object in corona didn't help

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  • CacheManager.getCacheFileBaseDir() always returns null

    - by Leon
    Hi, I've been trying to use the CacheManager for caching some http requests but it failed every time with a nullpointer exception. After some digging I believe I found out why: CacheManager.getCacheFileBaseDir() always returns null so when I try to use CacheManager.getCacheFile() or CacheManager.saveCacheFile() they fail. CacheManager.cacheDisabled() returns false :S I hadn 't created a cache partition via the AVD manager so I thought the problem lie there. But after creating a cache partition getCacheFile() still return null: 03-16 00:25:16.321: ERROR/AndroidRuntime(296): Caused by: java.lang.NullPointerException 03-16 00:25:16.321: ERROR/AndroidRuntime(296): at android.webkit.CacheManager.getCacheFile(CacheManager.java:296) What could be the problem? I've got the code posted here: http://pastebin.com/eaJwfXEK But it's a bit messy because I've been trying tons of stuff. Why does CacheManager.getCacheFileBaseDir() return null and not a File object? Thanks in advance! Leon

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  • How to prevent caching from jQuery Ajax?

    - by cynwong
    Hi, Could anyone please help me with this? I have a web page using .manifest for offline storage caching. In that page, I use jQuery ajax call to get the data from the server. If I first load the page, it is OK. I can switch between Online and Offline. But the problem is when I go back online and refresh the page. jQuery ajax cannot be able to talk to server anymore. Is there a way to for ajax to talk to the server or clear offline cache? My ajax call is as such: $.ajax({ type: "GET", url: requestUrl, success: localSuccess, error: error, dataType: "text", cache:false });

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  • Getting Started with CacheMoney

    - by Matt Grande
    I recently installed cache-money. After some difficulties getting memcached and cache-money set up, I thought I had it working. It cached the one query on my login page fine. I login, and go to my message index page and get this error: indices delegated to @cache_config.indices, but @cache_config is nil: Slug(id: integer, name: string, sluggable_id: integer, sequence: integer, sluggable_type: string, scope: string, created_at: datetime) Searching for the first part of that error message returns 0 hits on Google, so I'm at a loss on where to even begin. Any suggestions?

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  • Convert your Hash keys to object properties in Ruby

    - by kerry
    Being a Ruby noob (and having a background in Groovy), I was a little surprised that you can not access hash objects using the dot notation.  I am writing an application that relies heavily on XML and JSON data.  This data will need to be displayed and I would rather use book.author.first_name over book[‘author’][‘first_name’].  A quick search on google yielded this post on the subject. So, taking the DRYOO (Don’t Repeat Yourself Or Others) concept.  I came up with this: 1: class ::Hash 2:  3: # add keys to hash 4: def to_obj 5: self.each do |k,v| 6: if v.kind_of? Hash 7: v.to_obj 8: end 9: k=k.gsub(/\.|\s|-|\/|\'/, '_').downcase.to_sym 10: self.instance_variable_set("@#{k}", v) ## create and initialize an instance variable for this key/value pair 11: self.class.send(:define_method, k, proc{self.instance_variable_get("@#{k}")}) ## create the getter that returns the instance variable 12: self.class.send(:define_method, "#{k}=", proc{|v| self.instance_variable_set("@#{k}", v)}) ## create the setter that sets the instance variable 13: end 14: return self 15: end 16: end This works pretty well.  It converts each of your keys to properties of the Hash.  However, it doesn’t sit very well with me because I probably will not use 90% of the properties most of the time.  Why should I go through the performance overhead of creating instance variables for all of the unused ones? Enter the ‘magic method’ #missing_method: 1: class ::Hash 2: def method_missing(name) 3: return self[name] if key? name 4: self.each { |k,v| return v if k.to_s.to_sym == name } 5: super.method_missing name 6: end 7: end This is a much cleaner method for my purposes.  Quite simply, it checks to see if there is a key with the given symbol, and if not, loop through the keys and attempt to find one. I am a Ruby noob, so if there is something I am overlooking, please let me know.

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  • Snap to object layout in SSIS

    - by simonsabin
    If you’ve ever used SSIS you will have found that getting a decent layout is a pain. It would be nice to have more features to help layout things nicely. Jamie has proposed such a suggestion to allow you to align objects to each other, a bit like what you get with reporting services. Have a look at Jamie’s suggestion and vote for it if you agree https://connect.microsoft.com/SQLServer/feedback/details/644668/ssis-snap-to...(read more)

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  • How to CompareTo two Object without known about their real type

    - by Kamil
    I have to implement a one linked list but it should put object in appropriate position. Everything was OK when I use it in conjunction with specific class, but when I tried make it universal and argument of method insert was Object some problem appeared. When I want to input Object in right position I should use CompareTo method, but there isn't method in Object class! The problem is how to compare two object elements without known about their real types. Maybe I should use generic class type? But what about CompareTo? Or maybe combine with Element class and place CompareTo there? I suppose it is feasible. :) public void insert(Object o) { Element el = new Element(o); // initializing and setting iterators while(!it.isDone() && ((it.current().getValue())).CompareTo(o)<0) // it.current() returns Element of List { //move interators } //... }

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  • Memory mapped files causes low physical memory

    - by harik
    I have a 2GB RAM and running a memory intensive application and going to low available physical memory state and system is not responding to user actions, like opening any application or menu invocation etc. How do I trigger or tell the system to swap the memory to pagefile and free physical memory? I'm using Windows XP. If I run the same application on 4GB RAM machine it is not the case, system response is good. After getting choked of available physical memory system automatically swaps to pagefile and free physical memory, not that bad as 2GB system. To overcome this problem (on 2GB machine) attempted to use memory mapped files for large dataset which are allocated by application. In this case virtual memory of the application(process) is fine but system cache is high and same problem as above that physical memory is less. Even though memory mapped file is not mapped to process virtual memory system cache is high. why???!!! :( Any help is appreciated. Thanks.

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  • NSObject release destroys local copy of object's data

    - by Spider-Paddy
    I know this is something stupid on my part but I don't get what's happening. I create an object that fetches data & puts it into an array in a specific format, since it fetches asynchronously (has to download & parse data) I put a delegate method into the object that needs the data so that the data fetching object copies it's formatted array into an array in the calling object. The problem is that when the data fetching object is released, the copy it created in the caller is being erased, code is: In .h file @property (nonatomic, retain) NSArray *imagesDataSource; In .m file // Fetch item details ImagesParser *imagesParserObject = [[ImagesParser alloc] init:self]; [imagesParserObject getArticleImagesOfArticleId:(NSInteger)currentArticleId]; [imagesParserObject release] <-- problematic release // Called by parser when images parsing is finished -(void)imagesDataTransferComplete:(ImagesParser *)imagesParserObject { self.imagesDataSource = [ImagesParserObject.returnedArray copy]; // copy array to local variable // If there are more pics, they must be assembled in an array for possible UIImageView animation NSInteger picCount = [imagesDataSource count]; if(picCount > 1) // 1 image is assumed to be the pic already displayed { // Build image array NSMutableArray *tempPicArray = [[NSMutableArray alloc] init]; // Temp space to hold images while building for(int i = 0; i < picCount; i++) { // Get Nr from only article in detailDataSource & pic name (Small) from each item in imagesDataSource NSString *picAddress = [NSString stringWithFormat:@"http://some.url.com/shopdata/image/article/%@/%@", [[detailDataSource objectAtIndex:0] objectForKey:@"Nr"], [[imagesDataSource objectAtIndex:i] objectForKey:@"Small"]]; NSURL *picURL = [NSURL URLWithString:picAddress]; NSData *picData = [NSData dataWithContentsOfURL:picURL]; [tempPicArray addObject:[UIImage imageWithData:picData]]; } imagesArray = [tempPicArray copy]; // copy makes immutable copy of array [tempPicArray release]; currentPicIndex = 0; // Assume first pic is pic already being shown } else imagesArray = nil; // No need for a needless pic array // Remove please wait message [pleaseWaitViewControllerObject.view removeFromSuperview]; } I put in tons of NSLog lines to keep track of what was going on & self.imagesDataSource is populated with the returned array but when the parser object is released self.imagesDataSource becomes empty. I thought self.imagesDataSource = [ImagesParserObject.returnedArray copy]; is supposed to make an independant object, like as if it was alloc, init'ed, so that self.imagesDataSource is not just a pointer to the parser's array but is it's own array. So why does the release of the parser object clear the copy of the array. (I checked & double checked that it's not something overwriting self.imagesDataSource, commenting out [imagesParserObject release] consistently fixes the problem) Also, I have exactly the same problem with self.detailDataSource which is declared & populated in the exact same way as self.imagesDataSource I thought that once I call the parser I could release it because the caller no longer needs to refer to it, all further activity is carried out by the parser object through it's delegate method, what am I doing wrong?

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  • Best practise when using httplib2.Http() object

    - by tomaz
    I'm writing a pythonic web API wrapper with a class like this import httplib2 import urllib class apiWrapper: def __init__(self): self.http = httplib2.Http() def _http(self, url, method, dict): ''' Im using this wrapper arround the http object all the time inside the class ''' params = urllib.urlencode(dict) response, content = self.http.request(url,params,method) as you can see I'm using the _http() method to simplify the interaction with the httplib2.Http() object. This method is called quite often inside the class and I'm wondering what's the best way to interact with this object: create the object in the __init__ and then reuse it when the _http() method is called (as shown in the code above) or create the httplib2.Http() object inside the method for every call of the _http() method (as shown in the code sample below) import httplib2 import urllib class apiWrapper: def __init__(self): def _http(self, url, method, dict): '''Im using this wrapper arround the http object all the time inside the class''' http = httplib2.Http() params = urllib.urlencode(dict) response, content = http.request(url,params,method)

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  • How to retrieve only updated/new records since the last query in SQL?

    - by William Choi
    Hi all, I was asked to design a class for caching SQL query results. Calling the class' query method will query and cache the entire set of results at the first time; afterward, each subsequence query will retrieve only the updated portion, and will merge the result into the cache. If the class is required to be generic, i.e. NO knowledge about the db and the tables, do you have any idea? Is it possible, and how to retrieve only updated/new records since the last query? Thanks! William

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  • Python C API return more than one value / object without building a tuple [migrated]

    - by Grisu
    I got the following problem. I have written a C-Extension to Python(2.7 / 3.2) to interface a self written software library. Unfortunately I need to return two values from the function where the last one is optional. In Python I tried def func(x,y): return x+y, x-y test = func(13,4) but test is a tuple. If I write test1,test2 = func(13,4) I got both values separated. Is there a possibility to return only one value without unpacking the tuple, i.e. the second(,.. third, ..fourth) value gets neglected? And if such a solution existst, how does it look for the C-API? Because return Py_BuildValue("ii",x+y,x-y); results in a tuple as well.

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  • Scene Graph as Object Container?

    - by Bunkai.Satori
    Scene graph contains game nodes representing game objects. At a first glance, it might seem practical to use Scene Graph as physical container for in game objects, instead of std::vector< for example. My question is, is it practical to use Scene Graph to contain the game objects, or should it be used only to define scene objects/nodes linkages, while keepig the objects stored in separate container, such as std::vector<?

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  • Getting a sphere to roll down a .FBX object Unity3D/C#

    - by Timothy Williams
    I'm working on a little ramp and ball game in Unity, I modeled the ramp outside Unity and exported it to a .FBX file, then I imported the ramp in to Unity. I set up the ball and ramp, both have Rigidbodies, Ramp is set to isKinematic = true, yet when I play the game the ball just falls right through the ramp and hits the floor below it fine. So it's something wrong with the ramp. Am I doing something wrong? Are .FBX files unable to apply physics? Thanks, Tim.

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  • JavaScript-like Object in Python standard library?

    - by David Wolever
    Quite often, I find myself wanting a simple, "dump" object in Python which behaves like a JavaScript object (ie, its members can be accessed either with .member or with ['member']). Usually I'll just stick this at the top of the .py: class DumbObject(dict): def __getattr__(self, attr): return self[attr] def __stattr__(self, attr, value): self[attr] = value But that's kind of lame, and there is at least one bug with that implementation (although I can't remember what it is). So, is there something similar in the standard library? And, for the record, simply instanciating object doesn't work: obj = object() obj.airspeed = 42 Traceback (most recent call last): File "", line 1, in AttributeError: 'object' object has no attribute 'airspeed' Thanks, David

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  • Python C API return more than one value / object

    - by Grisu
    I got the following problem. I have written a C-Extension to Python to interface a self written software library. Unfortunately I need to return two values from the C function where the last one is optional. In Python the equivalent is def func(x,y): return x+y, x-y test = func(13,4) #only the first value is used In my C extension I use return Py_BuildValue("ii",x+y,x-y); which results in a tuple. If I now try to access the return value from Python via test2 = cfunc(13,4) print(test2) I got a tuple instead of only the first return value. How is possible to build the same behavior as in Python from C Extension?

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  • projection / view matrix: the object is bigger than it should and depth does not affect vertices

    - by Francesco Noferi
    I'm currently trying to write a C 3D software rendering engine from scratch just for fun and to have an insight on what OpenGL does behind the scene and what 90's programmers had to do on DOS. I have written my own matrix library and tested it without noticing any issues, but when I tried projecting the vertices of a simple 2x2 cube at 0,0 as seen by a basic camera at 0,0,10, the cube seems to appear way bigger than the application's window. If I scale the vertices' coordinates down by 8 times I can see a proper cube centered on the screen. This cube doesn't seem to be in perspective: wheen seen from the front, the back vertices pe rfectly overlap with the front ones, so I'm quite sure it's not correct. this is how I create the view and projection matrices (vec4_initd initializes the vectors with w=0, vec4_initw initializes the vectors with w=1): void mat4_lookatlh(mat4 *m, const vec4 *pos, const vec4 *target, const vec4 *updirection) { vec4 fwd, right, up; // fwd = norm(pos - target) fwd = *target; vec4_sub(&fwd, pos); vec4_norm(&fwd); // right = norm(cross(updirection, fwd)) vec4_cross(updirection, &fwd, &right); vec4_norm(&right); // up = cross(right, forward) vec4_cross(&fwd, &right, &up); // orientation and translation matrices combined vec4_initd(&m->a, right.x, up.x, fwd.x); vec4_initd(&m->b, right.y, up.y, fwd.y); vec4_initd(&m->c, right.z, up.z, fwd.z); vec4_initw(&m->d, -vec4_dot(&right, pos), -vec4_dot(&up, pos), -vec4_dot(&fwd, pos)); } void mat4_perspectivefovrh(mat4 *m, float fovdegrees, float aspectratio, float near, float far) { float h = 1.f / tanf(ftoradians(fovdegrees / 2.f)); float w = h / aspectratio; vec4_initd(&m->a, w, 0.f, 0.f); vec4_initd(&m->b, 0.f, h, 0.f); vec4_initw(&m->c, 0.f, 0.f, -far / (near - far)); vec4_initd(&m->d, 0.f, 0.f, (near * far) / (near - far)); } this is how I project my vertices: void device_project(device *d, const vec4 *coord, const mat4 *transform, int *projx, int *projy) { vec4 result; mat4_mul(transform, coord, &result); *projx = result.x * d->w + d->w / 2; *projy = result.y * d->h + d->h / 2; } void device_rendervertices(device *d, const camera *camera, const mesh meshes[], int nmeshes, const rgba *color) { int i, j; mat4 view, projection, world, transform, projview; mat4 translation, rotx, roty, rotz, transrotz, transrotzy; int projx, projy; // vec4_unity = (0.f, 1.f, 0.f, 0.f) mat4_lookatlh(&view, &camera->pos, &camera->target, &vec4_unity); mat4_perspectivefovrh(&projection, 45.f, (float)d->w / (float)d->h, 0.1f, 1.f); for (i = 0; i < nmeshes; i++) { // world matrix = translation * rotz * roty * rotx mat4_translatev(&translation, meshes[i].pos); mat4_rotatex(&rotx, ftoradians(meshes[i].rotx)); mat4_rotatey(&roty, ftoradians(meshes[i].roty)); mat4_rotatez(&rotz, ftoradians(meshes[i].rotz)); mat4_mulm(&translation, &rotz, &transrotz); // transrotz = translation * rotz mat4_mulm(&transrotz, &roty, &transrotzy); // transrotzy = transrotz * roty = translation * rotz * roty mat4_mulm(&transrotzy, &rotx, &world); // world = transrotzy * rotx = translation * rotz * roty * rotx // transform matrix mat4_mulm(&projection, &view, &projview); // projview = projection * view mat4_mulm(&projview, &world, &transform); // transform = projview * world = projection * view * world for (j = 0; j < meshes[i].nvertices; j++) { device_project(d, &meshes[i].vertices[j], &transform, &projx, &projy); device_putpixel(d, projx, projy, color); } } } this is how the cube and camera are initialized: // test mesh cube = &meshlist[0]; mesh_init(cube, "Cube", 8); cube->rotx = 0.f; cube->roty = 0.f; cube->rotz = 0.f; vec4_initw(&cube->pos, 0.f, 0.f, 0.f); vec4_initw(&cube->vertices[0], -1.f, 1.f, 1.f); vec4_initw(&cube->vertices[1], 1.f, 1.f, 1.f); vec4_initw(&cube->vertices[2], -1.f, -1.f, 1.f); vec4_initw(&cube->vertices[3], -1.f, -1.f, -1.f); vec4_initw(&cube->vertices[4], -1.f, 1.f, -1.f); vec4_initw(&cube->vertices[5], 1.f, 1.f, -1.f); vec4_initw(&cube->vertices[6], 1.f, -1.f, 1.f); vec4_initw(&cube->vertices[7], 1.f, -1.f, -1.f); // main camera vec4_initw(&maincamera.pos, 0.f, 0.f, 10.f); maincamera.target = vec4_zerow; and, just to be sure, this is how I compute matrix multiplications: void mat4_mul(const mat4 *m, const vec4 *va, vec4 *vb) { vb->x = m->a.x * va->x + m->b.x * va->y + m->c.x * va->z + m->d.x * va->w; vb->y = m->a.y * va->x + m->b.y * va->y + m->c.y * va->z + m->d.y * va->w; vb->z = m->a.z * va->x + m->b.z * va->y + m->c.z * va->z + m->d.z * va->w; vb->w = m->a.w * va->x + m->b.w * va->y + m->c.w * va->z + m->d.w * va->w; } void mat4_mulm(const mat4 *ma, const mat4 *mb, mat4 *mc) { mat4_mul(ma, &mb->a, &mc->a); mat4_mul(ma, &mb->b, &mc->b); mat4_mul(ma, &mb->c, &mc->c); mat4_mul(ma, &mb->d, &mc->d); }

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