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• How do I swap two objects in C# (specifically Mono) without triggering GC?

  - by TenFour04

  I have two array lists. that I want to swap each frame. My question is, does the variable 'temp' need to be a member variable to avoid triggering GC, assuming this method is called on dozens of objects each frame? I'm not creating a new object, just a new reference to an object. public void LateUpdate(){ ArrayList<int> temp = previousFrameCollisions; previousFrameCollisions = currentFrameCollisions; currentFrameCollisions = temp; currentFrameCollisions.clear(); } I've been told there's no reason to make a primitive into a member variable just to avoid GC, so my best guess is that this also applies to object references.

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• Minimizing use of paper

  - by Abody97

  I've recently faced this problem in a dynamic programming curriculum, and I honestly have no idea about how to determine the appropriate state. You're given N (1 <= N <= 70) paragraphs and M (1 <= M <= N) figures. Each paragraph i requires PL_i (1 <= PL_i <= 100) lines and references at most one figure. Each figure is referenced exactly once (i.e., no two paragraphs can reference the same figure, and for each figure there's a paragraph that references it.) Each figure requires PF_i (1 <= PF_i <= 100) lines. The task is to distribute those figures and paragraphs on paper in the order they're given, where one paper fits for L lines at most. No paragraph or figure is too large to fit on one paper. If a paragraph x placed on paper x_p references a figure y then y must be placed on either the paper x_p - 1 or x_p or x_p + 1. We have to find the minimum number of lines (and thus pages) to allocate in order to distribute all the figures and paragraphs. Any help would be extremely appreciated. Thanks in advance!

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• Where can I get the 10k common English dictionary words which Stack overflow uses in related question? [migrated]

  - by itpian.com

  Where can I get the 10k common English dictionary words which Stack overflow uses in related question? Here in SE podcast - http://blog.stackoverflow.com/2008/12/podcast-32/ One of our major performance optimizations for the “related questions” query is removing the top 10,000 most common English dictionary words (as determined by Google search) before submitting the query to the SQL Server 2008 full text engine. It’s shocking how little is left of most posts once you remove the top 10k English dictionary words. This helps limit and narrow the returned results, which makes the query dramatically faster.

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• Which is more expensive multiple conditional branches or multiple relational expression in a single condition?

  - by bman

  Which is more expensive in terms of processing costs if ( x < 20 && z == "M") { // statements 3 } if ( x >= 20 && w && x <= 65) { // statements 1 } if( x >= 20 &&z != "M"){ // statements 2 } or this if ( x < 20 ) { if( z == 'M') // statements 3; } else if ( x <= 65 && w == true ) // statements 1; if ( z == 'F' ) // statements 2; }

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• gDatabase Optimization: Need a really big database to test some of the features of sql server

  - by user299404

  I have done database optimization for dbs upto 3GB size. Need a really large database to test optimization.

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• linux hardware raid 10 / lvm / virtual machine partition alignment and filesystem optimization

  - by Jason Ward

  I've been reading everything I can find about partition alignment and filesystem optimization (ext4 and xfs) but still don't know enough to be confident in setting up my current configuration. My remaining confusion comes from the LVM layer and if I should use raid parameters on the filesystem in guest os'es. My main questions are: When I use 'pvcreate --dataalignment' do I use the stripe-width as calculated for a filesystem on RAID (128kB for ext4 in my situation), the Stripe size of the RAID set (256kB), something else altogether, or do I not need this? When I create ext2/3/4 or xfs filesystems in guests on the Logical Volumes, should I add the settings for the underlying RAID (e.g. mkfs.ext4 -b 4096 -E stride=64,stripe-width=128)? Does anyone see any glaring errors in my set up below? I'm running some benchmarks now but haven't done enough to start comparing results. I have four drives in RAID 10 on a 3ware 9750-4i controller (more details on the settings below) giving me a 6.0TB device at /dev/sda. Here is my partition table: Model: LSI 9750-4i DISK (scsi) Disk /dev/sda: 5722024MiB Sector size (logical/physical): 512B/512B Partition Table: gpt Number Start End Size File system Name Flags 1 1.00MiB 257MiB 256MiB ext4 BOOTPART boot 2 257MiB 4353MiB 4096MiB linux-swap(v1) 3 4353MiB 266497MiB 262144MiB ext4 4 266497MiB 4460801MiB 4194304MiB Partition 1 is to be the /boot partition for my xen host. Partition 2 is swap. Partition 3 is to be the root (/) for my xen host. Partition 4 is to be (the only) physical volume to be used by LVM (for those who are counting, I left about 1.2TB unallocated for now) For my Xen guests, I usually create a Logical Volume of the needed size and present it to the guests for them to partition as needed. I know there are other ways of handling that but this method works best for my situation. Here's the hardware of interest on my CentOS 6.3 Xen Host: 4x Seagate Barracuda 3TB ST3000DM001 Drives (sector size: 512 logical/4096 physical) 3ware 9750-4i w/BBU (sector size reported: 512 logical/512 physical) All four drives make up a RAID 10 array. Stripe: 256kB Write Cache enabled Read Cache: intelligent StoreSave: Balance Thanks!

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• Changes in gcc/persistence of optimization flags gcc/C

  - by gnometorule

  Just curious. Using gcc/gdb under Ubuntu 9.10. Reading a C book that also often gives the disassembly of the object file. When reading in January, my disassembly looks a lot like the book's; now, it's quite different - possibly more optimized (I notice some re-arrangements in the assembly code now that, at least in the files I checked, look optimized). I have used optimization options -O1 - -O3 for gcc between the first and second read, but not before the first. (1) Is the use of optimization options persistent, aka, if you use them once, you'll use them until switching them off? That would be weird (browsed man file and at least did not see anything to that sort). In the unlikely case that it is true, how do you switch them off? (2) Has gcc's assembly changed through any recent upgrade? (3) Does gcc sometimes produce (significantly) different assembly code although same compile options are chosen? Thanks much.

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• ICC vs GCC - Optimization and CPU architecture

  - by Rayne

  Hi all, I'm interested in knowing how GCC differs from Intel's ICC in terms of the optimization levels and catering to specific processor architecture. I'm using GCC 4.1.2 20070626 and ICC v11.1 for Linux. How does ICC's optimization levels (O1 to O3) differ from GCC, if they differ at all? The ICC is able to cater specifically to different architectures (IA-32, intel64 and IA-64). I've read that GCC has the -march compiler option which I think is similar, but I can't find a list of the options to use. I'm using Intel Xeon X5570, which is 64-bit. Are there any other GCC compiler options I could use that would cater my applications for 64-bit Intel CPUs? Thank you. Regards, Rayne

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• Query optimization

  - by Lijo

  Hi Team, I am trying to learn SQL query optimization using SQL Server 2005. However, I did not find any practical example where I can improve performance by tweaking query alone. Can you please list some example queries - prior and after optimization? It has to be query tuning – not adding index, not making covering index, not making any alteration to table. No change is supposed to be done on table and index. [ I understand that indexes are important. This is only for learning purpose] It would be great if you can exaplain using temp table instead of refering any sample databases like adventureworks. Expecting your support... Thanks Lijo

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• small string optimization for vector?

  - by BuschnicK

  I know several (all?) STL implementations implement a "small string" optimization where instead of storing the usual 3 pointers for begin, end and capacity a string will store the actual character data in the memory used for the pointers if sizeof(characters) <= sizeof(pointers). I am in a situation where I have lots of small vectors with an element size <= sizeof(pointer). I cannot use fixed size arrays, since the vectors need to be able to resize dynamically and may potentially grow quite large. However, the median (not mean) size of the vectors will only be 4-12 bytes. So a "small string" optimization adapted to vectors would be quite useful to me. Does such a thing exist? I'm thinking about rolling my own by simply brute force converting a vector to a string, i.e. providing a vector interface to a string. Good idea?

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• Will spreading your servers load not just consume more recourses

  - by Saif Bechan

  I am running a heavy real-time updating website. The amount of recourses needed per user are quite high, ill give you an example. Setup Every visit The application is php/mysql so on every visit static and dynamic content is loaded. Recourses: apache,php,mysql Every second (no more than a second will just be too long) The website needs to be updated real-time so every second there is an ajax call thats updates the website. Recourses: jQuery,apache,php,mysql Avarage spending for single user (spending one minute and visited 3 pages) Apache: +/- 63 requests / responsess serving static and dynamic content (img,css,js,html) php: +/- 63 requests / responses mysql: +/- 63 requests / responses jquery: +/- 60 requests / responses Optimization I want to optimize this process, but I think that maybe it would be just the same in the end. Before implementing and testing (which will take weeks) I wanted to have some second opinions from you guys. Every visit I want to start off with having nginx in the front and work as a proxy to deliver the static content. Recources: Dynamic: apache,php,mysql Static: nginx This will spread the load on apache a lot. Every Second For the script that loads every second I want to set up Node.js server side javascript with nginx in te front. I want to set it up that jquery makes a request ones a minute, and node.js streams the data to the client every second. Recources: jQuery,nginx,node.js,mysql Avarage spending for single user (spending one minute and visited 3 pages) Nginx: 4 requests / responsess serving mostly static conetent(img,css,js) Apache: 3 requests only the pages php: 3 requests only the pages node.js: 1 request / 60 responses jquery: 1 request / 60 responses mysql: 63 requests / responses Optimization As you can see in the optimisation the load from Apache and PHP are lifted and places on nginx and node.js. These are known for there light footprint and good performance. But I am having my doubts, because there are still 2 programs extra loaded in the memory and they consume cpu. So it it better to have less programs that do the job, or more. Before I am going to spend a lot of time setting this up I would like to know if it will be worth the while.

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• Drop caches in Linux

  - by BerserkEVA

  I have an embedded Geode-based application server with 512MB RAM and I'm about to try to maximize free memory during applications workload, which uses MySQL database 5.5 with InnoDB quite aggressively. As part of the whole optimization I'd want to introduce echo 1 > /proc/sys/vm/drop_caches sleep 5 echo 0 > /proc/sys/vm/drop_caches in crontab. How often is it safe to execute something like this? Any other observation/suggestion is welcome.

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• Big O, how do you calculate/approximate it?

  - by Sven

  Most people with a degree in CS will certainly know what Big O stands for. It helps us to measure how (in)efficient an algorithm really is and if you know in what category the problem you are trying to solve lays in you can figure out if it is still possible to squeeze out that little extra performance.* But I'm curious, how do you calculate or approximate the complexity of your algorithms? *: but as they say, don't overdo it, premature optimization is the root of all evil, and optimization without a justified cause should deserve that name as well.

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• how to see the optimized code in c

  - by sganesh

  I can examine the optimization using profiler, size of the executable file and time to take for the execution. I can get the result of the optimization. But I have these questions, How to get the optimized C code. Which algorithm or method used by C to optimize a code. Thanks in advance.

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• Does Your Business Really Need a Search Engine Optimization Specialist?

  If you're an individual or an organization planning to employ a search engine optimization professional, you might first want to consider the possibility of doing this work yourself. Certainly, a search engine optimization consultant can boost your site and perhaps help save you time and effort, yet the fact is that SEO is hardly an advanced science, and there are just a handful of authentic professionals within the field. So, if you depend on somebody else to be in charge of your search engine optimization, there's a high probability that the person will not possess a great deal more knowledge than you. And if you lack any knowledge, all the relevant information is easy to obtain.

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• Performance problems when running Java desktop applications on Citrix Metaframe

  - by demetriusnunes

  We have a desktop Java application running within a Citrix Metaframe server farm and the performance, specially while starting up the app, is very unreliable. Sometimes it takes 15 seconds and sometimes it takes over a minute. It's really unpredicatable. Is there any way to optimize running Java desktop applications within Citrix Metaframe Terminal server sessions to a more reliable performance level? Are there any optimization directed specifically toward Java, such as pre-load JVMs or something like that? Any help would be greatly appreciated.

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• Options to optimize lotus notes 8.5.X

  - by Jakub

  Has anyone found actually useful optimization methods for the bulky, fat, eclipse giant, nuissance that is Lotus Notes 8.5? I want it to be fast, and not eat up system resources like crazy while I run it ALL day (as it is my company's corporate mail / cal / scheduling solution). I've tried various hacks for the JVM heap size (if I recall correctly). None really bring a performance improvement. I have a dual core cpu, if that helps (I tried going the route of optimizing JAVA for 2 cores in hopes it would work, but seen no speed improvement). Notes is just sooo bloated, anyone have any suggestions to optimize/mod this thing so it is more responsive and less of a resource hog. Note: I don't want to switch to the web version, or the standard stripped down versions, I am aware of those, I just cannot since we don't run those internally for the company.

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• Fusion 3.1 and Parallels 6 for Win7 x64

  - by Ronnie

  I read in a recent article that Parallels Desktop 6 is faster almost everywhere than VMware Fusion. I was originally using Parallels 4 before passing to VMware due to the frequent Parallels crashes. As now I am using a lot Fusion on my Macbook on a big Win7 x64 virtualized development machine that I find too slow I am wondering if the announced speed up of Parallels V6 is justified to come back to it. As a test I converted my Fusion 3.1 to a trial of Parallels Desktop 6 and my Windows Experience Index passed from 4.7 of Fusion to 4.5 on Parallels 6 so apparently the virtualized machine is not seeing that speed benefit. Is there any optimization to set up on Parallels to increase the WEI or should I stay with Fusion (and in this case this kind of articles is just marketing stuff)?

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• Does anyone still use Iometer?

  - by Brian T Hannan

  "Iometer is an I/O subsystem measurement and characterization tool for single and clustered systems. It is used as a benchmark and troubleshooting tool and is easily configured to replicate the behaviour of many popular applications." link text Does anyone still use this tool? It seems helpful, but I'm not sure if it's for the thing I am trying to work on. I am trying create a benchmark computer performance test that can be run before and after a Windows Optimization program does its stuff (ex: PC Optimizer Pro or CCleaner). I want to be able to make a quick statement like CCleaner makes the computer run 50% faster or something along those lines. Are there any newer tools like this one?

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• ILOG CPLEX: how to populate IloLPMatrix while using addGe to set up the model?

  - by downer

  I have a queatoin about IloLPMatrix and addGe. I was trying to follow the example of AdMIPex5.java to generate user defined cutting planes based on the solution to the LP relaxation. The difference is that eh initial MIP model is not read in from a mps file, but set up in the code using methods like addGe, addLe etc. I think this is why I ran into problems while copying the exampe to do the following. IloLPMatrix lp = (IloLPMatrix)cplex.LPMatrixIterator().next(); lp from the above line turns to be NULL. I am wondering 1. What is the relationship between IloLPMatrix and the addLe, addGe commands? I tried to addLPMatrix() to the model, and then used model.addGe methods. but the LPMatrix seems to be empty still. How do I populate the IloLPMatrix of the moel according to the value that I had set up using addGe and addLe. Is the a method to this easily, or do I have to set them up row by row myself? I was doing this to get the number of variables and their values by doing lp.getNumVars(). Is there other methods that I can use to get the number of variables and their values wihout doing these, since my system is set up by addLe, addGe etc? Thanks a lot for your help on this.

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• What are the practical differences between an IP address and a server?

  - by JMC Creative

  My understanding of IPs and other DNS-type server-related issues really falls short (read: exteme noob). I know a dedicated server would increase speed. What, if any, difference in speed would a dedicated IP make? Am I correct in understanding the Best Practices from Yahoo that I could use the second IP to serve up some content, which would increase the number of parallel downloads for the user? Or are both IPs (purchase from same hosting account) going to point to the same server? Or how does it work? Are there other optimization things I should be aware of when thinking of purchasing a dedicated IP? Clarification I am talking about the speed of serving the webpages, i.e. the speed of my website. Yes, I know that IP and server are completely different, not even opposites, just different. But this, indeed, is my question! The Question Reformulated: Will having a second (dedicated) IP on my website speed up the time that it will load and display for the user? Or does that have nothing at all to do with IP, and is only a server issue? I'm sorry if this is still unclear. This is a real question though, I may just not be wording it well.

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• .NET Runtime Optimization Service

  - by Velika

  I see that the Service ".NET Runtime Optimization Service v2.0.50727_X86" is disabled C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\mscorsvw.exe I guess I probably did that, not sure. Do I need it/Should it be running?

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• Blit Queue Optimization Algorithm

  - by martona

  I'm looking to implement a module that manages a blit queue. There's a single surface, and portions of this surface (bounded by rectangles) are copied to elsewhere within the surface: add_blt(rect src, point dst); There can be any number of operations posted, in order, to the queue. Eventually the user of the queue will stop posting blits, and ask for an optimal set of operations to actually perform on the surface. The task of the module is to ensure that no pixel is copied unnecessarily. This gets tricky because of overlaps of course. A blit could re-blit a previously copied pixel. Ideally blit operations would be subdivided in the optimization phase in such a way that every block goes to its final place with a single operation. It's tricky but not impossible to put this together. I'm just trying to not reinvent the wheel. I looked around on the 'net, and the only thing I found was the SDL_BlitPool Library which assumes that the source surface differs from the destination. It also does a lot of grunt work, seemingly unnecessarily: regions and similar building blocks are a given. I'm looking for something higher-level. Of course, I'm not going to look a gift horse in the mouth, and I also don't mind doing actual work... If someone can come forward with a basic idea that makes this problem seem less complex than it does right now, that'd be awesome too. EDIT: Thinking about aaronasterling's answer... could this work? Implement customized region handler code that can maintain metadata for every rectangle it contains. When the region handler splits up a rectangle, it will automatically associate the metadata of this rectangle with the resulting sub-rectangles. When the optimization run starts, create an empty region handled by the above customized code, call this the master region Iterate through the blt queue, and for every entry: Let srcrect be the source rectangle for the blt beng examined Get the intersection of srcrect and master region into temp region Remove temp region from master region, so master region no longer covers temp region Promote srcrect to a region (srcrgn) and subtract temp region from it Offset temp region and srcrgn with the vector of the current blt: their union will cover the destination area of the current blt Add to master region all rects in temp region, retaining the original source metadata (step one of adding the current blt to the master region) Add to master region all rects in srcrgn, adding the source information for the current blt (step two of adding the current blt to the master region) Optimize master region by checking if adjacent sub-rectangles that are merge candidates have the same metadata. Two sub-rectangles are merge candidates if (r1.x1 == r2.x1 && r1.x2 == r2.x2) | (r1.y1 == r2.y1 && r1.y2 == r2.y2). If yes, combine them. Enumerate master region's sub-rectangles. Every rectangle returned is an optimized blt operation destination. The associated metadata is the blt operation`s source.

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• Looking for libraries which implement sequential minimal optimization in C++

  - by Anton

  I want to use SMO (Sequential Minimal Optimization) in order to train an SVM (Support Vector Machine). Can anyone suggest existing C++ libraries which implement SMO? I plan to use this to train an SVM to find an object in a picture (probably a human).

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• PostgreSQL 8.4 - Tablespace Optimization

  - by FloE

  I'm currently running a PostgreSQL Database with about 1.5 billion rows / 500 GB of data (including indices). There are several schemata: on for the (read only, irregular changes / updates) 'core-model' and one for every user (about 20 persons). The users can access the core and store data in their own schema, so everything is located in one database. The server runs with CentOS and PostgreSQL 8.4 and is used for scientific studies, exploration etc and is running quite well. These days an upgrade of the DB storage hard disks arrive - all with the same performance as the old ones. I'm looking for the best way to distribute the data on these disks. It would be possible to separate frequently used objects (the core-data) from the user schemata, but I'm not sure if this is really worth the effort. It seems to be a much better idea to move the WAL files (pg_xlog directory) to its own partition. http://www.postgresql.org/docs/8.4/static/wal-internals.html What are your opinions? Are there any tablespace- or partitioning-related performance documentations / benchmarks?

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