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  • What is the logic behind this C Program?

    - by iamanimesh19
    Here is a small piece of program (14 lines of program) which counts the number of bits set in a number. Input-Output -- 0--0(0000000), 5--2(0000101), 7--3(0000111) int CountBits (unsigned int x) { static unsigned int mask[] = { 0x55555555, 0x33333333, 0x0F0F0F0F, 0x00FF00FF, 0x0000FFFF } ; int i ; int shift ; /* Number of positions to shift to right*/ for (i =0, shift =1; i < 5; i ++, shift *= 2) x = (x & mask[i ])+ ( ( x >> shift) & mask[i]); return x; } Can someone explain the algorithm used here/why this works?

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  • Wavefront mesh: determine which face a point belongs to?

    - by Mina Samy
    I have a 3D mesh Wavefront .obj file. Is there any algorithm that takes an arbitrary point coordinates as input and determines which face of the mesh that point belongs to ?? The mesh is rendered on the screen, then the user clicks on it, I want to determine which part of the mesh the user has clicked on ? Here's the code using LibGDX: Vector3 intersection=new Vector3(); Ray ray=camera.getPickRay(x, y); //vertices is an array that hold the coordinates of the mesh boolean ok=Intersector.intersectRayTriangles(ray, vertices, intersection); Thanks

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  • with dash or not in domain [closed]

    - by menardmam
    Possible Duplicate: Is it better to put hyphens in a domain name ? I have to buy a domain it can be : somebigcompany.com or some-big-company.com I know, it's not a sample answer... but i like to know your point of view... the client what with no dash, i think for Google, and readability the dash is better... i have talk to a expert SEO that sait since panda update of the google algorithm it will be punish to have dash.. i don't believe it ! after your answer, i go to godaddy to buy it thanks in advance

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  • The how of a collision engine

    - by JXPheonix
    This is a very, very broad question - what is the general algorithm of how a collision engine works? No code in specific, but rather, just a general idea of how a collision engine does what it does, constantly refreshing the points of an object and comparing it to other objects? (see, I have the general gist of it here.) A collision engine is basically an engine used in games (generally) so that your player (call him Bob), whenever bob moves into a wall, Bob stops, Bob does not walk through the wall. They also generally handle the gravity in a game and environmental things like that.

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  • Caching strategies - LRU, MRU, Clock-Pro

    - by golgofa
    I am going to write a bachelor's science work on caching strategies and really, can't find any links to specifications or full descriptions of some of them. Only something like summaries from wikipedia. Please, help with some links on LRU, MRU caching and new-one - Clock Pro. Thanks a lot. All links are very useful for me. The purpose of work - is to compare different cache strategies to get more effiency. It based on WebApplication with ejb 2.0, so algorithm's will be implemented there, espesially in ejbLoad() and ejbFindByPrimarKey(). Also, one of aspects of this application - it will use not common scheme of tables in database - it based on metamodel. So, if you had any experience on this topic, i would be grateful to take some of your knowledge)

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  • How do I balance program CPU reverse compatibility whist still being able to use cutting edge features?

    - by TheLQ
    As I learn more about C and C++ I'm starting to wonder: How can a compiler use newer features of processors without limiting it just to people with, for example, Intel Core i7's? Think about it: new processors come out every year with lots of new technologies. However you can't just only target them since a significant portion of the market will not upgrade to the latest and greatest processors for a long time. I'm more or less wondering how this is handled in general by C and C++ devs and compilers. Do compilers make code similar to if SSE is supported, do this using it, else do that using the slower way or do developers have to implement their algorithm twice, or what? More or less how do you release software that takes advantage of newer processor technologies while still keeping a low common denominator?

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  • Algorithms for positioning rectangles evenly spaced with unknown connecting lines

    - by MacGyver
    I'm new to game development, but I'm trying to figure out a good algorithm for positioning rectangles (of any width and height) in a given surface area, and connecting them with any variation of lines. Two rectangles will never have more than one line connecting them. Where would I begin working on a problem like this? This is only a 2 dimensional surface. I read about graph theory, and it seems like this is a close representation of that. The rectangles would be considered a node, and the lines connecting them would be considered an edge in graph theory.

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  • How to understand Linux kernel source code for a beginner?

    - by user16867
    I am a student interested in working on Memory Management, particularly the page replacement component of the linux kernel. What are the different guides that can help me to begin understanding the kernel source? I have tried to read the book Understanding the Linux Virutal Memory Manager by Mel Gorman and Understanding the Linux Kernel by Cesati and Bovet, but they do not explain the flow of control through the code. They only end up explaining various data structures used and the work various functions perform. This makes the code more confusing. My project deals with tweaking the page replacement algorithm in a mainstream kernel and analyse its performance for a set of workloads. Is there a flavor of the linux kernel that would be easier to understand(if not the linux-2.6.xx kernel)?

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  • Is acousting fingerprinting too broad for one audio file only?

    - by IBG
    So we were looking for some topics related to audio analysis and found acoustic fingerprinting. As it is, it seems like the most famous application for it is for identification of music. Enter our manager, who requested us to research and possible find an algorithm or existing code that we can use for this very simple approach (like it's easy, source codes don't show up like mushrooms): Always-on app for listening Compare the audio patterns to a single audio file (assume sound is a simple beep) If beep is detected, send notification to server With a flow this simple, do you think acousting fingerprinting is a broad approach to use? Should we stop and take another approach? Where to best start? We haven't started anything yet (on the development side) on this regard, so I want to get other opinion if this is pursuit is worth it or moot.

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  • How to document and teach others "optimized beyond recognition" computationally intensive code?

    - by rwong
    Occasionally there is the 1% of code that is computationally intensive enough that needs the heaviest kind of low-level optimization. Examples are video processing, image processing, and all kinds of signal processing, in general. The goals are to document, and to teach the optimization techniques, so that the code does not become unmaintainable and prone to removal by newer developers. (*) (*) Notwithstanding the possibility that the particular optimization is completely useless in some unforeseeable future CPUs, such that the code will be deleted anyway. Considering that software offerings (commercial or open-source) retain their competitive advantage by having the fastest code and making use of the newest CPU architecture, software writers often need to tweak their code to make it run faster while getting the same output for a certain task, whlist tolerating a small amount of rounding errors. Typically, a software writer can keep many versions of a function as a documentation of each optimization / algorithm rewrite that takes place. How does one make these versions available for others to study their optimization techniques?

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  • How are trajectories calculated and transmitted to other players in Multi-Player ?

    - by giulio
    I play alot of COD4. And can see tracers for gunfire, missles, care packages fall from helicopters etc. There is alot of activity. I am curious to know the algorithm (at a high level) that manages all this action when you have 20 people on a map shooting each other to death ? This question touches on the subject but doesn't ask for a more in-depth answer as to how you the developers go about calculating and transmitting movement and collision detection for projectiles, be it missles/bullets or any other object that is flying through the air in real-time.

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  • Azure Task Scheduling Options

    - by charlie.mott
    Currently, the Azure PaaS does not offer a distributed\resilient task scheduling service.  If you do want to host a task scheduling product\solution off-premise (and ideally use Azure), what are your options? PaaS Option 1: Worker Roles Use a worker role to schedule and execute actions at specific time periods.  There are a few frameworks available to assist with this: http://azuretoolkit.codeplex.com https://github.com/Lokad/lokad-cloud/wiki/TaskScheduler http://blog.smarx.com/posts/building-a-task-scheduler-in-windows-azure - This addresses a slightly different set of requirements. It’s a more dynamic approach for queuing up tasks, but not repeatable tasks (e.g. daily). I found the Azure Toolkit option the most simple to implement.  Step 1 : Create a domain entity implementing IJob for each job to schedule.  In this sample, I asynchronously call a WCF service method. 1: namespace Acme.WorkerRole.Jobs 2: { 3: using AzureToolkit; 4: using ScheduledTasksService; 5: 6: public class UploadEmployeesJob : IJob 7: { 8: public void Run() 9: { 10: // Call Tasks Service 11: var client = new ScheduledTasksServiceClient("BasicHttpBinding_IScheduledTasksService"); 12: client.UploadEmployees(); 13: client.Close(); 14: } 15: } 16: } Step 2 : In the worker role run method, add the jobs to the toolkit engine. 1: namespace Acme.WorkerRole 2: { 3: using AzureToolkit.Engine; 4: using Jobs; 5:   6: public class WorkerRole : WorkerRoleEntryPoint 7: { 8: public override void Run() 9: { 10: var engine = new CloudEngine(); 11:   12: // Add Scheduled Jobs (using CronJob syntax - see http://www.adminschoice.com/crontab-quick-reference). 13:   14: // 1. Upload Employee job - 8.00 PM every weekday (Mon-Fri) 15: engine.WithJobScheduler().ScheduleJob<UploadEmployeesJob>(c => { c.CronSchedule = "0 20 * * 1-5"; }); 16: // 2. Purge Data job - 10 AM every Saturday 17: engine.WithJobScheduler().ScheduleJob<PurgeDataJob>(c => { c.CronSchedule = "0 10 * * 6"; }); 18: // 3. Process Exceptions job - Every 5 minutes 19: engine.WithJobScheduler().ScheduleJob<ProcessExceptionsJob>(c => { c.CronSchedule = "*/5 * * * *"; }); 20:   21: engine.Run(); 22: base.Run(); 23: } 24: } 25: } Pros Cons Azure Toolkit option is simple to implement. For the AzureToolkit option, you are limited to a single worker role.  Otherwise, the jobs will be executed multiple times, once for each worker role instance.   Paying for a continuously running worker role, even if it just processes a single job once a week.  If you only have a few scheduled tasks to run calling asynchronous services hosted in different web roles, an extra small worker role likely to be sufficient.  However, for an extra small worker role this still costs $14.40/month (03/09/2012). Option 2: Use Scheduled Task on Azure Web Role calling a console app Setup a Windows Scheduled Task on the Azure Web Role. This calls a console application that calls the WCF service methods that run the task actions. This design is described here: http://www.ronaldwidha.net/2011/02/23/cron-job-on-azure-using-scheduled-task-on-a-web-role-to-replace-azure-worker-role-for-background-job/ http://www.voiceoftech.com/swhitley/index.php/2011/07/windows-azure-task-scheduler/ http://devlicio.us/blogs/vinull/archive/2011/10/23/moving-to-azure-worker-roles-for-nothing-and-tasks-for-free.aspx Pros Cons Fairly easy to implement. Supportability - I RDC’ed onto the Azure server and stopped the scheduled task. I then rebooted the machine and the task was re-started. I also tried deleting the task and rebooting, the same thing occurred. The only way to permanently guarantee that a task is disabled is to do a fresh deployment. I think this is a major supportability concern.   Saleability - multiple instances would trigger multiple tasks. You can only have one instance for the scheduled task web role. The guidance implements setup of the scheduled task as part of a web role instance. But if you have more than one instance in a web role, the task will be triggered multiple times for each scheduled action (once per machine). Workaround: If we wanted to use scheduled tasks for another client with a saleable WCF service, then we could include the console & tasks scripts in a separate web role (e.g. a empty WCF service with no real purpose to it). SaaS Option 3: Azure Marketplace I thought that someone might be offering this type of service via the Azure marketplace. At the point of writing this blog post, I did not find anyone doing so. https://datamarket.azure.com/ Pros Cons   Nobody currently offers this on the Azure Marketplace. Option 4: Online Job Scheduling Service Provider There are plenty of online providers that offer this type of service on a pay-as-you-go approach.  Some of these are free for small usage.   Many of these providers are listed here: http://en.wikipedia.org/wiki/Webcron Pros Cons No bespoke development for scheduler. Reliance on third party. IaaS Option 5: Setup Scheduling Software on Azure IaaS VM’s One of job scheduling software offerings could be installed and configured on Azure VM’s.  A list of software options is listed here: http://en.wikipedia.org/wiki/List_of_job_scheduler_software Pros Cons Enterprise distributed\resilient task scheduling service VM Setup and maintenance   Software Licence Costs Option 6: VM Gallery A the time of writing this blog post, I did not spot a VM in the gallery that included pre-installation of any of the above software options. Pros Cons   No current VM template. Summary For my current project that had a small handful of tasks to schedule with a limited project budget I chose option 1 (a worker role using the Azure Toolkit to schedule tasks).  If I was building an enterprise scale solution for the future, options 4 and 5 are currently worthy of consideration. Hopefully, Microsoft will include tasks scheduling in the future as part of their PaaS offerings.

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  • How to make my sprite jump properly?

    - by Matthew Morgan
    I'm currently working on a 2D platformer in XNA. I have, however been having some trouble with creating a fully functional jumping algorithm. This is what I have so far: if (keystate.IsKeyDown(Keys.W)) if (onGround = true) //"onground" is true when the collision between the main sprite and the ground is detected { spritePosition.Y = velocity.Y = -5; } So, the problem I am now having is that as soon as the jump starts the variable "onGround" = false and the sprite is brought back the ground by the simple gravity I have implemented. The other problem I have is creating a limit to the height after which the sprite should automatically return to the ground. Any advice or suggestions would be greatly appreciated.

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  • What web oriented language would work best with binary data?

    - by Qqwy
    I want to create a service where people can upload files. However, since file storage costs money, I want to compress the files so they take less space. I would want to write my own compression algorithm, however, PHP doesn't have good ways to handle binary data (which is needed for many compression algorithms). So I wondered, what would be a better language to create such a website in? I have knowledge of PHP (and Javascript, HTML and CSS) but no experience with other things like Ruby, Perl, Python, and other web development languages.

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  • Map, Set use cases in a general web app

    - by user2541902
    I am currently working on my own Java web app (to be shown in interview to get a Java job). So I've not worked on Java in professional environment, so no guidance. I have database, entity classes, JPA relationships. Use cases are like, user has albums, album has pics, user has locations, location has co-ordinates etc. I used List (ArrayList) everywhere. I can do anything with List and DB, get some entry, find etc. For example, I will keep the list of users in List, then use queries to get some entry (why would I keep them in Map with id/email as key?). I know very well the working and features, implementing classes of Map, Set. I can use them for solving some algorithm, processing some data etc. In interviews, I get asked have you worked with these, where have you used them etc. So, Please tell me cases where they should be used (DB or any popular real use case).

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  • k-d tree implementation [closed]

    - by user466441
    when i run my code and debugged,i got this error - this 0x00093584 {_Myproxy=0x00000000 _Mynextiter=0x00000000 } std::_Iterator_base12 * const - _Myproxy 0x00000000 {_Mycont=??? _Myfirstiter=??? } std::_Container_proxy * _Mycont CXX0017: Error: symbol "" not found _Myfirstiter CXX0030: Error: expression cannot be evaluated + _Mynextiter 0x00000000 {_Myproxy=??? _Mynextiter=??? } std::_Iterator_base12 * but i dont know what does it means,code is this #include<iostream> #include<vector> #include<algorithm> using namespace std; struct point { float x,y; }; vector<point>pointleft(4); vector<point>pointright(4); //we are going to implement two comparison function for x and y coordinates,we need it in calculation of median (we should sort vector //by x or y according to depth informaton,is depth even or odd. bool sortby_X(point &a,point &b) { return a.x<b.x; } bool sortby_Y(point &a,point &b) { return a.y<b.y; } //so i am going to implement to median finding algorithm,one for finding median by x and another find median by y point medianx(vector<point>points) { point temp; sort(points.begin(),points.end(),sortby_X); temp=points[(points.size()/2)]; return temp; } point mediany(vector<point>points) { point temp; sort(points.begin(),points.end(),sortby_Y); temp=points[(points.size()/2)]; return temp; } //now construct basic tree structure struct Tree { float x,y; Tree(point a) { x=a.x; y=a.y; } Tree *left; Tree *right; }; Tree * build_kd( Tree *root,vector<point>points,int depth) { point temp; if(points.size()==1)// that point is as a leaf { if(root==NULL) root=new Tree(points[0]); return root; } if(depth%2==0) { temp=medianx(points); root=new Tree(temp); for(int i=0;i<points.size();i++) { if (points[i].x<temp.x) pointleft[i]=points[i]; else pointright[i]=points[i]; } } else { temp=mediany(points); root=new Tree(temp); for(int i=0;i<points.size();i++) { if(points[i].y<temp.y) pointleft[i]=points[i]; else pointright[i]=points[i]; } } return build_kd(root->left,pointleft,depth+1); return build_kd(root->right,pointright,depth+1); } void print(Tree *root) { while(root!=NULL) { cout<<root->x<<" " <<root->y; print(root->left); print(root->right); } } int main() { int depth=0; Tree *root=NULL; vector<point>points(4); float x,y; int n=4; for(int i=0;i<n;i++) { cin>>x>>y; points[i].x=x; points[i].y=y; } root=build_kd(root,points,depth); print(root); return 0; } i am trying ti implement in c++ this pseudo code tuple function build_kd_tree(int depth, set points): if points contains only one point: return that point as a leaf. if depth is even: Calculate the median x-value. Create a set of points (pointsLeft) that have x-values less than the median. Create a set of points (pointsRight) that have x-values greater than or equal to the median. else: Calculate the median y-value. Create a set of points (pointsLeft) that have y-values less than the median. Create a set of points (pointsRight) that have y-values greater than or equal to the median. treeLeft = build_kd_tree(depth + 1, pointsLeft) treeRight = build_kd_tree(depth + 1, pointsRight) return(median, treeLeft, treeRight) please help me what this error means?

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  • Is acoustic fingerprinting too broad for one audio file only?

    - by IBG
    We were looking for some topics related to audio analysis and found acoustic fingerprinting. As it is, it seems like the most famous application for it is for identification of music. Enter our manager, who requested us to research and possible find an algorithm or existing code that we can use for this very simple approach (like it's easy, source codes don't show up like mushrooms): Always-on app for listening Compare the audio patterns to a single audio file (assume sound is a simple beep) If beep is detected, send notification to server With a flow this simple, do you think acoustic fingerprinting is a broad approach to use? Should we stop and take another approach? Where to best start? We haven't started anything yet (on the development side) on this regard, so I want to get other opinion if this is pursuit is worth it or moot.

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  • Redirect from the main page on multilanguage site

    - by Pluto
    I've decided to start developing multilingual web site. Now I'm thinking about the structure. The idea is to use a simple algorithm to find out what language is most interesting to the visitor when he makes his first visit to the root page, and then forward him to the corresponding address, for example, http://example.com/en/ for English-speaking audience and http://example.com/ru/ for Russians. The question is, how search engines react on such redirect? If this approach does not take away site's reputation, which redirects should I choose: 301 or 302? I would be very grateful for the reasoned response.

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  • How to tile multiple procedurally generated textures?

    - by Burhuc
    I'm trying to develop a procedural tile generator for a game, mostly for the ground tiles, instead of using "hand-drawn" tiles. To achieve this I'm using Perlin noise and a sine wave with multiple parameters, which already gives me pretty nice results. I don't want to generate 1 tile and repeat that one forever for one ground type, but I want to avoid recurrences, so I'm generating n different tiles. The problem I'm having now is that I want to tile the generated textures (smooth transitions). At the moment I have this: 4 256x256 textures. I thought a simple method would be to just add the positions of the different tiles to the noise generation algorithm, so that, when creating the 4 256x256 textures, it would behave like it would create a 512x512 texture, but that somehow didn't work as intented. So how can I tile those textures?

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  • How to implement the setup rules like Clash of Clan?

    - by user25959
    Now I'm already implement the setup build rules which the building could move by unit grid width and height. But the validation detection is poor efficiency. The algorithm cost me 10~12(ms) in average when I move the building. Here is my approach to that: 1.Basic Grid, it is a two dimensional array. Grid[row][column], so that I can save info for each grid. Like whether is it in occupied or excluded. 2.Exclude Space, this is a space which limit same building numbers in space.

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  • Interview question ranking FizzBuzz (1), implementing malloc (10)

    - by blrs
    I'd like to have your opinion on the difficulty of the following interview question: Find the subarray with maximum sum in an array of integers in O(n) time. This trivial sounding problem was made famous by Jon Bentley in his Programming Pearls where he uses it to demonstrate algorithm design techniques. On a scale of 1-10, 1 being the FizzBuzz (or HoppityHop) test and 10 being implement the C stdlib function malloc(), how would you rank the above problem? I think the people who can best answer this question are those who have read Programming Pearls and have tried to solve this problem on their own. To motivate those who haven't, 'Programming Pearls' gets featured many times in the 'Top 10 programming books' list.

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  • Optimization of time-varying parameters

    - by brama
    I need to find an optimal set of "n" parameter values that minimize an objective function (a 2-hr simulation of a system). I have looked at genetic algorithm and simulated annealing methods, but was wondering if there are any better algorithms and guidance on their merits and limitations. With the above optimization methods I can find the optimal parameter values that hold true for the entire simulation duration. Incase, I want to find the optimal "time varying" parameter values (parameter values change with time during the 2-hr simulation), are there any methods/ideas other than making each time varying parameter value a variable to optimize? Any thoughts?

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  • Updated copy of the OBIEE Tuning whitepaper

    - by inowodwo
    The Product Assurance team have released an updated copy of the OBIEE Tuning Whitepaper. You can find it on the PA blog https://blogs.oracle.com/pa/entry/test or via Support note OBIEE 11g Infrastructure Performance Tuning Guide (Doc ID 1333049.1) https://support.us.oracle.com/oip/faces/secure/km/DocumentDisplay.jspx?id=1333049.1&recomm=Y This new revised document contains following useful tuning items: 1.    New improved HTTP Server caching algorithm. 2.    Oracle iPlanet Web Server tuning parameters. 3.    New tuning parameters settings / values for OPIS/OBIS components.

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  • Removing surrounding noises from voice recording

    - by Peak Reconstruction Wavelength
    I have a wave file whose frequency spectrum looks like this. http://i.stack.imgur.com/2rRaS.png It contains audio, which I want to keep while removing the rest. The problem is that the surround noise changes, just those distinct voice patterns remain. I marked the voice patterns for clarity: http://i.stack.imgur.com/eLkBl.png What could an algorithm look like / a workflow in adobe audition look like that removes everything but the voice patterns? I think that the main characteristic is the line-shaped form over time. Loudness alone is not enough as the noise is loud aswell.

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  • Developing an AI opponent for Monopoly

    - by Bernhard Zürn
    i want to develop an AI opponent for the Board Game Monopoly. I want to implement the whole Game with Prolog (XPCE). The probability for a field on the Board being hit, can be computed with Markov Chains. I already know some "best practices" like "after 50% of the playing time it does not make sense to buy out of jail because in jail you get renting fees for your fields but you don't have to pay for other fields as long as you stay in prison". The interesting question always is: buy a streetfield ? buy houses / hotels ? how much ? so i think i would have to compute some kind of future liquidity .. does anyone know how to pack that into an algorithm or how to translate it to prolog ?

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