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Everything posted by khaled

  1. The most basic NP problem is Binary-SAT, so scheduling problems that has at least 2 basic constraints are NP-Hard If there exist a scheduling problem that has 1 basic constraint, or no constraints .. these two variations are not NP
  2. 1. My citation was from Wikipedia, not from Literature 2. The word "Nurse" in NSP, is like "Salesman" in TSP .. they are just a name, each of these problems are just variations of the same problem and my speak earlier was general about scheduling problems (variations of NSP). 3. I didn't say that NSP is NP-hard, I said scheduling problems are NP-Hard, they can be reduced to CSP\SAT the changing of constraints is non-trivial - in fact it is crucial; there is also the matter of minor and major constraints, which this problem does not deal with. -- I was talking about the intractability of scheduling problems, not the scheduling constraints
  3. Is it that you disagree with me, or won't go read the references .. what I wrote in my reply is no opinion, A problem is not P or NP, intractable or tractable based on what we think .. NSP is like any scheduling problem, we just consider them nurses, they can be anything else, with any other constraints .. finding a solution for scheduling problem might sound simple if you try it on paper, but it's not easy for a computer to solve
  4. It's a huge confusion actually, Verification: check if there exist at least 1 solution for the given problem. Check: check if the input is a valid solution for the given problem. It's just like the difference between "are there BLUE balls in the box ?" and "is this a BLUE ball ?", where the given problem is "get a BLUE ball from the box". Decidability: A language is called decidable if there exists a method - any method at all - to determine whether a given word belongs to that language or not. --Wikipedia Actually decidability is not a simple concept, I know the concept but I don't understand it that I don't have enough understanding, Halting problem is undecidable, but it is partial-decidable. In Algorithms, decidability can be simple as deciding weather the input is a solution to the given problem, just like the example you gave of armstrong numbers, or can be complex as deciding weather an input is a member of the set of solutions for the given problem, which can be described in a different way to Turing Machine, saying is the state that this solution ends with exist in the set of final states F ... It's not about how much time we need to solve a problem with 10 cities for example, it's the question of how the algorithm progress with input increase [math]P[/math] denote algorithms that are polynomial-time bounded, in other words: [math]O(Time(\alpha)) \leq O(n^c) \;\;\rightarrow\;\; \alpha \;is\;P[/math] where c is a constant, n is the size of input.
  5. If you read the links, it shows how scheduling problems are intractable & NP-Hard, how to find that an NP problem is NP-Hard, what is SAT problem, what Optimization means in general context, and Dynamic Programming (Linear Optimization through optimal solutions over few variables, which result in the optimal solution for the problem) - Wikipedia:NSP - Wikipedia:NP - Wikipedia:NP-Hard - Wikipedia:Turing Reduction - Wikipedia:Optimization - Wikipedia:Dynamic Programming
  6. hey Xittenn, I'm playing Final Fantasy XIII-2 on PS3 .. It's really interesting you know,

    It has the ideas of Quantum Theory, String Theory, Relativity Theory, in a game where

    you can travel through Space-Time, where changes manipulate the flow of Time and Events

  7. It's good to be curious and it's good to think about it, These types of problems were already proven NP-Hard in the literature .. and since it can be solved by Constraint Programming, you can see that it can be reduced to the SAT problem, that how you can know it's NP-Hard, I think you should avoid using "optimization" in the context of Algorithms since it has a special meaning, I think what you wanted to say is that the question wasn't about finding an optimal algorithm to solve this problem, but a simple one Simple answers are a waste of time, either use patterns that may not work, or brute force for years to get the schedule, I think a simple answer would by reducing the problem to a simpler one that can be solved using Dynamic Programming
  8. Connector, [math]\sqrt{2} = 1.41421356237309504880168872420969807856967187537694807317667973799... \approx \frac{99}{70}[/math] The approximation differs from the correct value by less than [math]\frac{1}{10,000}[/math] --Wikipedia It has a fractional form, you know: [math][1;\bar{2}][/math] and finally, (personally I don't think you're familiar with this):
  9. Despite how trivial scheduling problems may sound, To be specific, it's NP-hard .. it's a variation of NSP (Nurse Scheduling Problem) It's usually solved using Constraint Programming or Heuristic Search
  10. I'm not sure of this, but I think that: By the definition of [math]\mathbb{R}^*[/math]: [math]\mathbb{R}^* = (\mathbb{R}^+ \cup \mathbb{R}^-) \setminus 0[/math] [math]\mathbb{R}^* = (\mathbb{R}^+ \cup \mathbb{R}^-) \setminus (\mathbb{R}^+ \cap \mathbb{R}^-)[/math] Since only 0 satisfy: [math]0 \in \mathbb{R}^+[/math] and [math]0 \in \mathbb{R}^-[/math] we get [math]0 \in (\mathbb{R}^+ \cap \mathbb{R}^-)[/math] Where [math](\mathbb{R}^+ \cap \mathbb{R}^-) = (\mathbb{R}^+ \cup \mathbb{R}^-) \setminus \mathbb{R}^*[/math]
  11. This problem is just like what DrRocket said, it's a combinatorial problem I'm not sure, but it seemed similar to knapsack problem, which can be solved using Dynamic Programming (Optimization over few variables) But this one seem to more complex than a knapsack problem
  12. I could imagine that the number system has two groups, positive numbers and negative numbers, and that they intersect at Zero
  13. Connector, [latex]\mathbb{R}[/latex] is the set of real numbers, [latex]\mathbb{R}[/latex] is closed on Multiplication, we have [math]a \times a = b[/math] where [math]a, b \in \mathbb{R}[/math], [math]a \times a = b \;\rightarrow\; a^2 = b \;\rightarrow\; a = \sqrt{b}[/math] Let's substitute b = 2, we get [math]a \times a = 2 \;\rightarrow\; a^2 = 2 \;\rightarrow\; a = \sqrt{2}[/math] where [math]a \in \mathbb{R}[/math]
  14. I think you are familiar with the term "Relative Address", which is an addressing method, where every reservation have addresses that start from 0 ~ MAX Where every reservation is given an index (a number) which is used to give the OFFSET, Example: 4 reservations on a 2 MB RAM, what is the address range for the third ? Answer: - Every reservation capacity is ( 2 MB / 4 ) = 512 KB - MAX = CAPACITY - 1 = 511 (since we start from 0) - 3rd OFFSET = (3 - 1) * CAPACITY = 2 * 512 KB = 1024 KB - 3rd Address Range = [OFFSET, OFFSET+MAX] = [1024 KB, 1535 KB] = [1048576, 1571840]
  15. Bootstrap is a process to startup an OS, Bootstrap operates using BIOS The Bootstrap works on BIOS to load the OS core, kernel, & user interface With no bootstrap the OS can never startup, so if you lose the bootstrap, you have to re-install that OS, even though your data and the OS data is still in the hard disk It's like if the OS is a TV, that can only be operated using a Remote Controller which is the Bootstrap So even if the TV is still there, it's useless in case you lost the Remote Controller
  16. It depends on what type of website you want to build: 1. Simple website (HTML, CSS, Javascript): a simple website pages .html that are linked with a single style sheet .css, java scripts enable you to do some tweaks, these websites can be built also through WYSIWYG HTML editors such as FrontPage 2. Master-detail website (HTML, CSS, Javascript, SharePoint\DreamWave\..): using SharePoint\DreamWave\..etc you can build a complete website, where the shape of your website is designed in a special html page "the master page" .master which contains a detail-containers such as content-container, now the content pages .html are substituted into the content-container in the master page to the output, it's more like a formula (master page), and input values (content pages), note also that master-detail websites are dynamic, in SharePoint you can link your page with a C# or a VB.net code ... 3. Simple Dynamic website (ASP\JSP\PHP, HTML, CSS, Javascript): a dynamic website is one where you can manage users sessions, login routines, work with the database, ..etc, for example the PHP: .php files represent the website pages, a .php file is basically an HTML page mixed with PHP code ... Example (example.html): <html> <head> <title>HTML Page Example</title> </head> <body> <div id="header" style="length:100px;width:800px;background-color:red;">header</div> <div id="content" style="length:400px;width:800px;background-color:green;">content</div> <div id="footer" style="length:40px;width:800px;background-color:blue;">footer</div> </body> </html> :: Note down here, that we used the same HTML example, but we added PHP code within <? .. ?> Example (example.php): <html> <head> <title>HTML Page Example</title> </head> <body> <div id="header" style="length:100px;width:800px;background-color:red;">header</div> <div id="content" style="length:400px;width:800px;background-color:green;"> <? // PHP CODE echo "Time: " ; // Print Date and Time echo strftime ( '%c' ) ; ?> </div> <div id="footer" style="length:40px;width:800px;background-color:blue;">footer</div> </body> </html> If you are doing this as a business, the website graphical and interactional design and structure is important, in this case you will need to work with a web graphical designer .. or learn how to design a website using Photoshop, ..etc and how to trim the website to build the pages\the master page.
  17. So you want to discuss how to build such a website\web-forum with such standards, and information legalization, rights, privacy ? Because, as a computer scientist, legalizations, rights, privacy, and civilization are related to Law, Politics, & Sociology .. not computer science How to build a web-forum where people can exchange informations in some ways is related to computer science, how those people exchange informations or set laws on how they exchange informations is not related to computer science Best Regards,
  18. I think this post should be moved to Law or Politics Forum .. since your questions are regarding legalization, standards, laws, & rights of informations exchanged within a group
  19. the title sound ambiguous to me .. this is how I parsed it "how to design a website, where alot of members can exchange & collaborate informations ?"
  20. We can talk about something, not talk about everything .. what is the point/s you wanna talk about ?
  21. khaled

    Time Travel

    I'm not good in physics, but this is what I know Time pass always .. maybe it pass faster in a frame than how it pass in another, but in the end at some point, both frames have passed the same amount of time So if we can create a Time Capsule which creates a frame that have a high time flow rate .. they won't travel into the future, they will just experience their life time faster, because their body will pass the same amount of time, in any time flow rate it goes It's like drinking glasses of beer, weather you drink the beer slower or faster, in the end all men will drink the same amount of beer eventually Another example is a movie file on your computer, you can play it slower, or 2x faster .. but in all ways, you will witness everything on that movie
  22. Let's share a fun fact: In tennis game Score zero is called 'Love' "Love is Zero", meaning "to play without any wager, for nothing" .. a Score "Zero to Zero" is called "Love for all" Source [book]: The Guinness Book of Tennis Facts & Feats and Fifteen Love
  23. khaled

    ms access

    Lazy to go google, click here then
  24. khaled

    ms access

    The name explains it actually .. design view shows the fields\columns and their data-types, & constraints. data-sheet view shows the data records.
  25. You need to clarify some things: 1. What exactly is your biological data, and how they're represented in your model\system ? 2. What is the problem you are trying to solve, elaborate in essence of input and output. 3. "Random Forest", it's Random Walk 4. "With a single classifier such as Bayesian Network or K-Nearst Neighbors", statistical classifier function learn (train the model, update the model tables) based on input sample. see Wikipedia:Statistical Classification I've worked previously on Machine Learning using Markov Chains and Dynamic Programming, if you want to know about it.
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