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• In-memory data structure that supports boolean querying

  - by sanity

  I need to store data in memory where I map one or more key strings to an object, as follows: "green", "blue" -> object1 "red", "yellow" -> object2 I need to be able to efficiently receive a list of objects, where the strings match some boolean criteria, such as: ("red" OR "green") AND NOT "blue" I'm working in Java, so the ideal solution would be an off-the-shelf Java library. I am, however, willing to implement something from scratch if necessary. Anyone have any ideas? I'd rather avoid the overhead of an in-memory database if possible, I'm hoping for something comparable in speed to a HashMap (or at least the same order of magnitude).

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• memory access violation error - 0xC0000005

  - by nobody

  I got memory access violation error sometimes.... but I don't know where the error comes from... So I reviewed the code and I found some strange code... delete m_p1; A *a = new A(); a->b = *c; m_p1 = a; --> strange code. I think it's a little strange line.... can i use the m_p1 after delete the m_p1? It can make some memory access error??

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• About memory and delete object in c++

  - by barssala

  I will give some examples and explain. First, I declare some object like CString* param = new CString[100] And when I declare this one, my memory would increase a little bit because it's some implemented string. Then I store this object in some list of CString just like List<CString> myList = new List<CString>; // new list of CString myList.add(param); This is my question: I wanna know, when I delete myList, my param isn't deleted, right? And memory in param still exists. Do I misunderstand?

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• memory leak in Zend_Db_Table_Row?

  - by Vincenzo

  This is the code I have: <?php $start = memory_get_usage(); $table = new Zend_Db_Table('user'); for ($i = 0; $i < 5; $i++) { $row = $table->createRow(); $row->name = 'Test ' . $i; $row->save(); unset($row); echo (memory_get_usage() - $start) . "\n"; } This is what I see: 90664 93384 96056 98728 101400 Isn't it a memory leak? When I have 500 objects to insert into DB in one script I'm getting memory overflow. Can anyone help?

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• dynamic memory allocation [closed]

  - by gcc

  i wanna write a program that creates (allocating memory) and manipulates (adding elements and increasing memory etc.) integer arrays dynamically according to given input sequences. input sequence which starts with the maximum number of arrays, includes integers to be put into arrays and some one letter characters which are commands to carry out some tasks (activating next array, deleting an array etc). also, i wanna create *c_arrays which is the address of the array whose elements are the actual capacities (How many integer slots are already allocated for an array?) of arrays how should i organize(set up) the algorithm?

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• removing image tag from memory

  - by Chapsterj

  I have seen some code to check if a background image on a div is loaded. What they are doing is adding a img tag to memory but storing it in a variable and using that to see if the image is loaded with the load event. My question is does the $img tag stay in memory and how would I be able to remove that tag when the load event has been called. var $div = $('div'), bg = $div.css('background-image'); if (bg) { var src = bg.replace(/(^url\()|(\)$|[\"\'])/g, ''), $img = $('<img>').attr('src', src).on('load', function() { // do something, maybe: $div.fadeIn(); }); } }); I got this code above from this post

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• memory management question -- releasing an object which has to be returned

  - by ulag

  Hi, I have an NSMutableArray called playlist. This is in a method called getAllPlaylists. The code is something like this: -(NSMutableArray *)getAllPlaylists { //playlist is an instance variable playlist = [[NSMutableArray alloc] init]; //memory leak here . . //some code here which populates the playlist array [playlist addObject: object1]; . . return playlist; } The array allocation step of playlist is causing a memory leak. In such a scenario where can i release this array? Or can i avoid allocation n initialization of playlist here by doing something else?

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• Get size of memory used by program

  - by CarlN26

  How do you calculate the total memory used by program on stack and heap until it ends?

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• mpirun -np N, what if N is larger than my core number?

  - by Daniel

  Say I have a 4-core workstation, what would linux (Ubuntu) do if I execute mpirun -np 9 XXX Q1. Will 9 run immediately together, or they will run 4 after 4? Q2. I suppose that using 9 is not good, because the remainder 1, it will make the computer confused, (I don't know is it going to be confused at all, or the "head" of the computer will decide which core among the 4 cores will be used?) Or it will be randomly picked. Who decide which one core to call? Q3. If I feel my cpu is not bad and my ram is okay and large enough, and my case is not very big. Is it a good idea in order to fully use my cpu and ram, that I do mpirun -np 8 XXX, or even mpirun -np 12 XXX. Q4. Who decides all of these effciency optimization, Ubuntu, or linux, or motherboard or cpu? Your enlightenment would be really appreciated.

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• Speed up bitstring/bit operations in Python?

  - by Xavier Ho

  I wrote a prime number generator using Sieve of Eratosthenes and Python 3.1. The code runs correctly and gracefully at 0.32 seconds on ideone.com to generate prime numbers up to 1,000,000. # from bitstring import BitString def prime_numbers(limit=1000000): '''Prime number generator. Yields the series 2, 3, 5, 7, 11, 13, 17, 19, 23, 29 ... using Sieve of Eratosthenes. ''' yield 2 sub_limit = int(limit**0.5) flags = [False, False] + [True] * (limit - 2) # flags = BitString(limit) # Step through all the odd numbers for i in range(3, limit, 2): if flags[i] is False: # if flags[i] is True: continue yield i # Exclude further multiples of the current prime number if i <= sub_limit: for j in range(i*3, limit, i<<1): flags[j] = False # flags[j] = True The problem is, I run out of memory when I try to generate numbers up to 1,000,000,000. flags = [False, False] + [True] * (limit - 2) MemoryError As you can imagine, allocating 1 billion boolean values (1 byte 4 or 8 bytes (see comment) each in Python) is really not feasible, so I looked into bitstring. I figured, using 1 bit for each flag would be much more memory-efficient. However, the program's performance dropped drastically - 24 seconds runtime, for prime number up to 1,000,000. This is probably due to the internal implementation of bitstring. You can comment/uncomment the three lines to see what I changed to use BitString, as the code snippet above. My question is, is there a way to speed up my program, with or without bitstring?

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• iPhone - dequeueReusableCellWithIdentifier usage

  - by Jukurrpa

  Hi, I'm working on a iPhone app which has a pretty large UITableView with data taken from the web, so I'm trying to optimize its creation and usage. I found out that dequeueReusableCellWithIdentifier is pretty useful, but after seeing many source codes using this, I'm wondering if the usage I make of this function is the good one. Here is what people usually do: UITableViewCell* cell = [tableView dequeueReusableCellWithIdentifier:@"Cell"]; if (cell == nil) { cell = [[UITableViewCell alloc] initWithFrame:CGRectZero reuseIdentifier:@"Cell"]; // Add elements to the cell return cell; And here is the way I did it: NSString identifier = [NSString stringWithFormat:@"Cell @d", indexPath.row]: // The cell row UITableViewCell* cell = [tableView dequeueReusableCellWithIdentifier:identifier]; if (cell != nil) return cell; cell = [[UITableViewCell alloc] initWithFrame:CGRectZero reuseIdentifier:identifier]; // Add elements to the cell return cell; The difference is that people use the same identifier for every cell, so dequeuing one only avoids to alloc a new one. For me, the point of queuing was to give each cell a unique identifier, so when the app asks for a cell it already displayed, neither allocation nor element adding have to be done. In fine I don't know which is best, the "common" method ceils the table's memory usage to the exact number of cells it display, whislt the method I use seems to favor speed as it keeps all calculated cells, but can cause large memory consumption (unless there's an inner limit to the queue). Am I wrong to use it this way? Or is it just up to the developper, depending on his needs?

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

  - by buggedcom

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

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• Delphi fast large bitmap creation (without clearing)

  - by Ritsaert Hornstra

  When using the TBitmap wrapper for a GDI bitmap from the unit Graphics I noticed it will always clear out the bitmap (using a PatBlt call) when setting up a bitmap with SetSize( w, h ). When I copy in the bits later on (see routine below) it seems ScanLine is the fastest possibility and not SetDIBits. function ToBitmap: TBitmap; var i, N, x: Integer; S, D: PAnsiChar; begin Result := TBitmap.Create(); Result.PixelFormat := pf32bit; Result.SetSize( width, height ); S := Src; D := Result.ScanLine[ 0 ]; x := Integer( Result.ScanLine[ 1 ] ) - Integer( D ); N := width * sizeof( longword ); for i := 0 to height - 1 do begin Move( S^, D^, N ); Inc( S, N ); Inc( D, x ); end; end; The bitmaps I need to work with are quite large (150MB of RGB memory). With these iomages it takes 150ms to simply create an empty bitmap and a further 140ms to overwrite it's contents. Is there a way of initializing a TBitmap with the correct size WITHOUT initializing the pixels itself and leaving the memory of the pixels uninitialized (eg dirty)? Or is there another way to do such a thing. I know we could work on the pixels in place but this still leaves the 150ms of unnessesary initializtion of the pixels.

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• 4GB of RAM in MacOSX 10.5, only 3GB in MacOSX 10.6

  - by Albert

  Hi, I was using MacOSX 10.5 on my MacBook until today and I had 4GB of memory there. Now I have updated to MacOSX 10.6 and it only displays 3GB. Why is that? How can I fix it? Also, I am a bit wondering why most people (well, most of the Google hits explained the 3GB issue that way -- leaving out the fact that it has worked earlier) are saying that a 32bit system can under no circumstances access more than 3.2GB. Don't we have PAE nowadays in most systems? Thanks, Albert

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• Hardware error messages from syslogd

  - by Farhat

  I have a 64-core AMD server running CEntOS on which I was running a long job. In the midst of the output, I see these lines. It appears to be a memory error. How severe is this and what exactly does it indicate? Message from syslogd@heracles at Nov 7 21:00:02 ... kernel:[Hardware Error]: MC4_STATUS[Over|CE|MiscV|-|AddrV|-|-|CECC]: 0xdc10410040080a13 Message from syslogd@heracles at Nov 7 21:00:02 ... kernel:[Hardware Error]: Northbridge Error (node 4): DRAM ECC error detected on the NB. Message from syslogd@heracles at Nov 7 21:00:02 ... kernel:[Hardware Error]: cache level: L3/GEN, mem/io: MEM, mem-tx: RD, part-proc: RES (no timeout)

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• How is htop "Swp" calculated?

  - by Thomas

  When I run htop (on OS X 10.6.8), I see something like this : 1 [||||||| 20.0%] Tasks: 70 total, 0 running 2 [||| 7.2%] Load average: 1.11 0.79 0.64 3 [|||||||||||||||||||||||||||81.3%] Uptime: 00:30:42 4 [|| 5.8%] Mem[|||||||||||||||||||||3872/4096MB] Swp[ 0/0MB] PID USER PRI NI VIRT RES SHR S CPU% MEM% TIME+ Command 284 501 57 0 15.3G 1064M 0 S 0.0 6.5 0:01.26 /Applications/Firefox.app/Contents/MacOS/firefox -psn_0_90134 437 501 57 0 14.8G 785M 0 S 0.0 4.8 0:00.18 /Applications/Thunderbird.app/Contents/MacOS/thunderbird -psn_0_114716 428 501 63 0 12.8G 351M 0 S 1.0 2.1 0:00.51 /Applications/Firefox.app/Contents/MacOS/plugin-container.app/Contents/MacOS/ 696 501 63 0 11.7G 175M 0 S 0.0 1.1 0:00.02 /System/Library/Frameworks/QuickLook.framework/Resources/quicklookd.app/Conte 38 0 33 0 11.1G 422M 0 S 0.0 2.6 0:00.59 /System/Library/Frameworks/CoreServices.framework/Frameworks/Metadata.framewo 183 501 48 0 10.9G 137M 0 S 0.0 0.8 0:00.03 /System/Library/CoreServices/Finder.app/Contents/MacOS/Finder How can I have Processes using Gigabytes of VIRT memory and still 0MB of Swap used ?

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• Bank Interleave Requested but not enabled

  - by wbeard52

  I have a ECS A770M-A motherboard with a 2.2GHz Phenom 64 Quad Core processor with 4 gigs of ram. I also have a 1GB DDR3 Zotac GeForce 9500GT video card installed in the computer. I believe the main memory is DDR2. The problem I am having is that I get a "Bank Interleave Requested but not Enabled" error on startup. The computer boots up fine (no error) with the 4gigs of ram if I replace the video card with the previous 256MB video card. I have also tried placing a single gig of ram in the computer with the Zotac video card and still get the error. My question is what would typically cause this error and would a DDR3 video ram be compatible with DDR2 system ram? Thanks

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• ECC RAM in GA-G33M-DS2R? Or any Gigabyte/G33M motherboard?

  - by Gregory Hoerner

  I'm looking to retire a server which has 12GB of ECC DDR2 RAM. I'd like to upgrade my multi-purpose machine (firewall, file server, VM host for Windows Home Server, etc.) using the RAM from the server. I was just wondering: Has anyone had experience using ECC RAM in a GA-G33M-DS2R motherboard (or any Gigabyte GA-G33M-XXXX motherboard for that matter)? Has anyone had experience using ECC RAM in a motherboard with a G33M chipset. I've searched everywhere and found the attitude positive of ECC memory working in a Non-ECC board, but I would like some specific positive feedback before proceeding tonight. I have to kick the entire house offline, which I don't like to do without good reason :)

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• XDEBUG/PHP doesn't dump profile even when set up properly?

  - by John D.

  I installed xdebug from source, but also tried my package manager (separately) and they both are loaded correctly (verified by restarting Apache and seeing the xdebug copyright info in phpinfo()) but they do not dump profiling information. Out of the 40 different attempts of configuration it logged once or twice but I lost what I did, I tried with first only loading the module in php.ini with no settings, but it didn't log to /tmp/. I tried many different settings but my current is now: xdebug.profiler_enable = Off xdebug.profiler_enable_trigger = 1 xdebug.profiler_output_dir = "/tmp/" xdebug.profiler_output_name = "profiler.%t" Of course I call my script through 127.0.0.1/test.php?XDEBUG_PROFILE, which is for enable_trigger. Do you know why it would not dump profiler information? nobody (Arch Linux) can write to /tmp/ as it has before, so I'm sure it is not a permissions error. Apache's error_log does not tell me anything about xdebug either, as it has loaded correctly. It just does not "work"! EDIT: I made a subfolder "xdebug_profiles" in /tmp/ and chown'ed it to nobody, and now it works flawlessly. I'm not sure why it couldn't write before, I guess it's just a caveat with nobody on Arch. I answered my own question , not enough points to answer it or comment, so consider this answered.

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• CPU's on Hyper-V host system is just idling, even though VM's are at full throttle

  - by Bjørn

  Hello, I have a server that is running Windows 2008 64 bit Hyper-V, with 8 gigs of RAM and Intel Xeon X3440 @ 2.53 Ghz, which gives me 8 logical cores in the performance monitor on the host system. I have set up three Virtual Machines, all running Windows 2008 32 bit. Build server, running Team City Staging server SQL Server, running SQL Server 2005 These three machines are running very sluggishly, they are at 100% cpu even though the host system is barely using any cpu at all, typically below 10% total. Could anyone please give some tips as to the best setup for CPU allocating? Should I have set each server to have two cores, or should I increase this number above the total number of cores on the host? What is a good number to set on the Virtual Machine Reserve and Virtual Machine Limit? Is 8 gigs of physical RAM insufficient for 3 VM's? Thanks for reading. :)

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• Turn off the Linux OOM killer by default?

  - by Peter Eisentraut

  The OOM killer on Linux wreaks havoc with various applications every so often, and it appears that not much is really done on the kernel development side to improve this. Would it not be better, as a best practice when setting up a new server, to reverse the default on the memory overcommitting, that is, turn it off (vm.overcommit_memory=2) unless you know you want it on for your particular use? And what would those use cases be where you know you want the overcommitting on? As a bonus, since the behavior in case of vm.overcommit_memory=2 depends on vm.overcommit_ratio and swap space, what would be a good rule of thumb for sizing the latter two so that this whole setup keeps working reasonably?

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• Serving images from another hostname vs Apache overload for the rewrites

  - by luison

  We are trying to improve further the speed of some sites with older HTML in order as well to obtain better SEO results. We have now applied some minify measures, combined html, css etc. We use a small virtualized infrastructure and we've always wanted to use a light + standar http server configuration so the first one can serve images and static contents vs the other one php, rewrites, etc. We can easily do that now with a VM using the same files and conf of vhosts (bind mounts) on apache but with hardly any modules loaded. This means the light httpd will have smaller fingerprint that would allow us to serve more and quicker, have more minSpareServer running, etc. So, as browsers benefit from loading static content from different hostnames as well, we've thought about building a rewrite rule on our main server (main.com) to "redirect" all images and css *.jpg, *.gif, *.css etc to the same at say cdn.main.com thus the browser being able to have more connections. The question is, assuming we have a very complex rewrite ruleset already (we manually manipulate many old URLs for SEO) will it be worth? I mean will the additional load of main's apache to have to redirect main.com/image.jpg (I understand we'll have to do a 301) to cdn.main.com/image.jpg + then cdn.main.com having to serve it, be larger than the gain we would be archiving on the browser? Could the excess of 301s of all images on a page be penalized by google? How do large companies work this out, does the original code already include images linked from the cdn with absolute paths? EDIT Just to clarify, our concern is not to do so much with server performance or bandwith. We could obviously employ an external CDN server but we have plenty CPU and bandwith. Our concern is with how to have "old" sites with plenty semi-static HTML content benefiting from splitting connections for images and static content via apache without having to change the html to absolute paths (ie. image.jpg to cdn.main.com/image.jpg happening on the server not the code)

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• Monitoring outgoing bandwidth of application

  - by jnolte

  I currently have a VPS that is consuming a ton of outgoing bandwidth and I am trying to drill down to where this may be coming from. Does anyone know of a logical way to go about finding out which pages on the site are consuming the most outgoing data. We have done a ton of front-end optimizations to the site and our google page speed rankings ar 85% so I feel we have done a pretty great job at optimizing the site for speed. Can someone lend some insight on how they have made similar optimizations? Application / Server Stack LEMP Running Varnish Cache / PHP5-FPM WordPress running w3 Total Cache Ubuntu 12.04 LTS

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• Better way to design a database

  - by cMinor

  I have a conceptual problem and I would like to get your ideas on how I'll be able to do what I am aiming. My goal is to create a database with information of persons who work at a place depending on their profession and skills,and keep control of salary and projects (how much would cost summing all the hours of work) I have 3 categories which can have subcategories: Outsourcing Technician welder turner assistant Administrative supervisor manager So each person has its information and the projects they are working on, also one person may do several jobs... I was thinking about having 5 tables (EMPLOYEE, SKILLS, PROYECTS, SALARY, PROFESSION) but I guess there is a better way of doing this. create table Employee ( PRIMARY KEY [Person_ID] int(10), [Name] varchar(30), [sex] varchar(10), [address] varchar(10), [profession] varchar(10), [Skills_ID] int(10), [Proyect_ID] int(10), [Salary_ID] int(10), [Salary] float ) create table Skills ( PRIMARY KEY [Skills_ID] int(10), FOREIGN KEY [Skills_name] varchar(10) REFERENCES Employee(Person_ID), [Skills_pay] float(10), [Comments] varchar(50) ) create table Proyects ( PRIMARY KEY [Proyect_ID] int(10), FOREIGN KEY [Skills_name] varchar(10) REFERENCES Employee(Person_ID) [Proyect_name] varchar(10), [working_Hours] float(10), [Comments] varchar(50) ) create table Salary ( PRIMARY KEY [Salary_ID] int(10), FOREIGN KEY [Skills_name] varchar(10) REFERENCES Employee(Person_ID) [Proyect_name] varchar(10), [working_Hours] float(10), [Comments] varchar(50) ) So to get the total amount of the cost of a project I would just sum the working hours of each employee envolved and sum some extra costs in an aggregate query. Is there a way to do this in a more efficient way? What to add or delete of this small model? I guess I am missing something in the salary - maybe I need another table for that?

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• Looking for a short term solution to improve website performance with additional server

  - by Tanim Mirza

  I am working with a small team to run an internal website running with PHP 5.3.9, MySQL 5.0.77. All the files and database are hosted on a dedicated Linux machine with the following configuration: Intel Xeon E5450 8 CPU cores @3.00GHz, 2992.498 MHz, Cache 6148 KB, Cent OS – Red Hat Enterprise Linux Server release 5.4 We started small and then the database got bigger and now the website performance degraded significantly. We often get server space overrun, mysql overloaded with too many calls, etc. We don't have much experience dealing with these issues. We recently got another server that we were thinking to use to improve performance. Since it has better configuration, some of us wanted to completely move everything to the new machine. But I am trying to find out how we can utilize both machine for optimized performance. I found options such as MySQL clustering, Load balancer, etc. I was wondering if I could get any suggestion for this situation "How to utilize two machines in short term for best performance", that would be great. By short term we are looking for something that we can deploy in a month or so. Thanks in advance for your time.

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