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• How to put 1000 lightweight server applications in the cloud

  - by Dan Bird

  The company I work for sells a commercial desktop/server app that runs on any non dedicated Windows PC or server and uses Tomcat for all interactions with the application. Customers are asking that we host their instance of the application so they don't have to run it locally on their own servers. The app is lightweight and an average server, in theory, could handle 25-50 instances before users would notice a slowdown. However only 1 instance can run per Windows instance (because the application writes to a common registry branch) so we'd need something like VMWare to create 25-50 Windows instances. We know we eventually need to reprogram to make it truly cloud-worthy but what would you recommend for a server farm or whatever for this? We don't have the setup to purchase our own servers so we must use a 3rd party. We have budgeted $500 - $1000 per year per customer for this service. Thanks in advance for your suggestions, experiences and guidance.

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• Quels sont les avantages du Cloud Computing pour votre entreprise ? Google lance "Go Google Cloud Ca

  Quels sont les avantages du Cloud Computing pour votre entreprise ? Google lance "Go Google Cloud Calculator" pour en appréhender les bénéfices Le cloud computing intéresse de plus en plus d'entreprises, et des millions d'entre elles se sont tournées vers Google en migrant vers les Google Apps. Une décision encore audacieuse, tant il est difficile d'imaginer ce que le travail « dans le nuage » signifie vraiment et quels en sont les véritables avantages. Quel est l'impact de la collaboration en ligne sur votre lieu de travail ? Comment une capacité de stockage d'email accrue ou une messagerie instantanée intégrée et le chat vidéo pourraient avoir un impact sur la productivité de votre entreprise ?

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• Les personnels IT pas assez qualifiés ? Oui, pour 93% des employeurs d'après un rapport de la Computing Technology Industry Association

  Les employés en informatique pas assez qualifiés pour 93% des employeurs Selon un rapport établi par la Computing Technology Industry Association La Computing Technology Industry Association, CompTIA, est un organisme à but non lucratif fondé en 1982 par 5 professionnels de l'industrie informatique. L'association s'est intéressée dans son dernier rapport aux employés travaillant dans le domaine des technologies de l'information et de la communication. Pour ce faire, elle a interrogé 500 patrons et responsables informatiques de grandes, moyennes et petites entreprises sur les compétences de leurs employés en informatique. Des employeurs du Canada, du Japon, de l'Afrique du ...

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• What are the challenges when my enterprise desires to move the processing component of an applicatio

  - by Berkay

  Assume that i have an enterprise accounting application that consists of a front-end interface, a processing tier, and a back-end database. This is an application that contains private business data, and thus is traditionally run in a secure private network environment within the enterprise. What are the challenges that appear when my enterprise desires to move the processing component of this application to a cloud computing data center in order to achieve greater scalability or to reduce IT costs ? Pls note: do i have to make significant changes to my own infrastructure to enable external access to formerly private resources? do i have to modify the application code to handle new network topology ? thanks, if you give your answers in a simple manner, really appreciated.

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• Real-time threat finder

  - by Rohit

  I want to make a small program that is capable to download files from the cloud onto my system. As the file reaches my system, another program on my system will analyze the file and try to find suspicious behaviors in it. I want to make a system similar to ThreatExpert (www.threatexpert.com). The suspicious data gathered by my program will be sent to Anti-Virus companies for analysis. I want to know whether this program can be written in .NET or as a PHP website. I have no experience of Cloud computing. How to retrieve files from the cloud?

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• Setup local EC2 style cloud?

  - by John Kramlich

  I was recently given 3 dual opteron 2400 servers with 4GB of RAM and 120GB hard drives. I am interested in setting up something similar to Amazon's EC2 for my own personal web development use. Basically, I would like to spin up instances from an ISO or other disk images and have them available to test and develop software. Are there open source solutions I can use to accomplish this? I am assuming one of the machines will need to act as a controller of some sort for the other two. I use Sun's VirtualBox on my local development machine to virtualize various versions of Microsoft Windows. However, I'm not sure if that's the best tool for what I am trying to achieve. I apologize in advance if this question is to vague to get meaningful responses. I am new to cloud computing and fairly new at server administration.

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• Cloud hosting and single hardware point of failure?

  - by PeterB

  From talking to sales I thought Rackspace Cloud was running on a SAN and compute nodes (as VMWare's offerings do), only to find out it doesn't, so when the host server goes down for maintenance all cloud servers on the server go down (in our case for 2.5 hours). I understand Amazon EC2 also has this single-server point of failure. Which cloud hosting solutions don't rely on a single server? I've yet to find a list by architecture Is there a term that distinguishes between these types of 'cloud'? Is one of these 'grid computing' and the other 'virtualisation'? Can a SAN backed solution provide the same reliability as 2 mirrored cloud servers on (say) Rackspace Cloud? I am more familiar with the VMWare architecture and would like to understand the advantages and disadvantages of each approach. I understand the standard architecture is to have multiple cloud servers and mirrored data between them; until we need multiple database servers I'm wondering if a SAN/node hosting solution would provide the lack of downtime we need without the added complexity.

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• What relationship do software Scrum or Lean have to industrial engineering concepts like theory of constraints?

  - by DeveloperDon

  In Scrum, work is delivered to customers through a series of sprints in which project work is time boxed to a fixed number of days or weeks, usually 30 days. In lean software development, the goal is to deliver as soon as possible, permitting early feedback for the next iteration. Both techniques stress the importance of workflow in which software work product does not accumulate in development awaiting release at some future date. Both permit new or refined requirements and feedback from QA and customers to be acted on with as little delay as possible based on priority. A few years ago I heard a lecture where the speaker talked briefly about a family of concepts from industrial engineering called theory of constraints. In the factory, they use an operations model based on three components: drum, buffer, and rope. The drum synchronizes work product as it flows through the system. Buffers that protect the system by holding output from one stage as it waits to be consumed by the next. The rope pulls product from one work station to the next. Historically, are these ideas part of the heritage of Scrum and Lean, or are they on a separate track? It we wanted to think about Scrum and Lean in terms of drum-buffer-rope, what are the parts? Drum = {daily scrum meeting, monthly release)? Buffer = {burn down list, source control system)? Rope = { daily meeting, constant integration server, monthly releases}? Industrial engineers define work flow in terms of different kinds of factories. I-Factories: straight pipeline. One input, one output. A-Factories: many inputs and one output. V-Factories: one input, many output products. T-Plants: many inputs, many outputs. If it applies, what kind of factory is most like Scrum or Lean and why?

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• What type of lambda calculus would Lisp loosely be an example of?

  - by Jason Baker

  I'm trying to get a better grip on how types come into play in lambda calculus. Admittedly, a lot of the type theory stuff is over my head. Lisp is a dynamically typed language, would that roughly correspond to untyped lambda calculus? Or is there some kind of "dynamically typed lambda calculus" that I'm unaware of?

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• graph algorithms on GPU

  - by scatman

  the current GPU threads are somehow limited (memory limit, limit of data structures, no recursion...). do you think it would be feasible to implement a graph theory problem on GPU. for example vertex cover? dominating set? independent set? max clique?.... is it also feasible to have branch-and-bound algorithms on GPUs? Recursive backtracking?

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• Balancing a Binary Tree (AVL)

  - by Gustavo Carreno

  Ok, this is another one in the theory realm for the CS guys around. In the 90's I did fairly well in implementing BST's. The only thing I could bever get my head around was the intricacy of the algorithm to balance a Binary Tree (AVL). Can you guys help me on this?

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• How to adjust the distribution of values in a random data stream?

  - by BCS

  Given a infinite stream of random 0's and 1's that is from a biased (e.g. 1's are more common than 0's by a know factor) but otherwise ideal random number generator, I want to convert it into a (shorter) infinite stream that is just as ideal but also unbiased. Looking up the definition of entropy finds this graph showing how many bits of output I should, in theory, be able to get from each bit of input. The question: Is there any practical way to actually implement a converter that is nearly ideally efficient?

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• What practical use/benefit does a ternary 'bit' based computer have?

  - by John

  Prototype working ternary device Quantum computing with qbits and so on is one thing, but what exactly do we stand to gain from a CPU which works on a ternary basis, where each 'bit' is ether yes/no/maybe (or true/false/filenotfound)? Is it simply an academic exercise or could it change processor design?

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• MS Access Premiere Products Exercise

  - by rynwtts

  I am working with Microsoft Access, Premiere Products Exercises for a college course. I can't seem to get past a specific question. We are working with DBDL and E-R Diagrams. The question is here. Indicate the changes you need to make to the design of the Premiere Products database to support the following situation. A customer is not necessarily represented by a single sales rep but can be represented by several sales reps. when a customer places an order, the sales rep who gets the commission on the order must be one of the collection of sales reps who represents the customer. In the database already each customer is represented by a sales rep. Which yields a one to one relationship. I need to enable a customer to have several sales reps, and make it so that only those sales rep will be eligible for commission upon each order.

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• Why is a FLAC encoded from a decoded MP3 bigger than the MP3?

  - by Ryan Thompson

  To be more precise than in the title, suppose I have a MP3 file that is 320 kbps. If I decompress it, then logically, all the data except for roughly 320 kilobits out of each second of audio should be redundant data, able to be compressed away. So, when I encode the decompressed file to FLAC, or any other lossless codec, why is it so much larger? On a related note, is it theoretically possible to losslessly recover the source mp3 audio from a decompressed wav? (I know the mp3 itself is lossy. I'm asking if it's possible to re-encode without any further loss.) EDIT: Let me clarify the related question, and the rationale behind it. Suppose I have a wav that was decompressed from an MP3 file (and assume I don't have the mp3 itself for some reason). If I don't want to lose any more quality, I can re-encode it with FLAC or any other lossless encoder and get a larger file just to maintain the same quality. Or, I can re-encode it to mp3 again and get the same size as the original but lose more data. Obviously, neither of these cases is ideal. I can either have the original size or the original quality, but not both (I mean the quality of the original mp3, not the original lossless source). My question is: Can we get both? Is it theoretically possible to recover the lossy compressed data from the lossy decompressed data, without losing even more? If it is possible, I could imagine a lossless compression algorithm that compresses the audio with FLAC. Then it also scans the audio for any signs of previous lossy compression, and if detected, recompresses it losslessly to the original lossy file. Then it keeps whichever file is smaller.

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• dhcpd pool exhaustion - What's the result?

  - by jarmund

  I have a DHCP server that serves leases to several houndred, maybe up to a thousand, different clients on an average day. The pool consists of 242 IPs, and due to the highly dynamic nature of the network, it's enough 99% of the time (most devices are gone from the network in a few minutes), despite having a lease time of 3600. Now, imagine if more clients than that connect to the network during an hour. The sollution is obvious: Decrease lease time, or increase the DHCP pool, however, what i would like to know: What happens when dhcpd has exhausted the pool? Are new DHCP requests simply ignored?

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• What if a computer with Ethernet

  - by George Nixon

  I'm just revising for an exam on Networks and Data Communications, and there's one thing I don't get about CSMA/CD and Ethernet. It's supposed to be fairly stable, for instance if a computer drops out of the network, it's not a problem like it might be in a token ring network (I think). But Ethernet works by all the other computers waiting for the currently transmitting computer to finish what it's doing, and then the others use CMSA/CD to determine who goes next. What if one computer malfunctioned and kept sending a continuous stream of data in an infinite loop? In fact, is there a standard time for pcs to transmit before they yield to others?

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• Limiting database security

  - by Torbal

  A number of texts signify that the most important aspects offered by a DBMS are availability, integrity and secrecy. As part of a homework assignment I have been tasked with mentioning attacks which would affect each aspect. This is what I have come up with - are they any good? Availability - DDOS attack Integrity Secrecy - SQL Injection attack Integrity - Use of trojans to gain access to objects with higher security roles

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• In the days of modern computing, in 'typical business apps' - why does performance matter?

  - by Prog

  This may seem like an odd question to some of you. I'm a hobbyist Java programmer. I have developed several games, an AI program that creates music, another program for painting, and similar stuff. This is to tell you that I have an experience in programming, but not in professional development of business applications. I see a lot of talk on this site about performance. People often debate what would be the most efficient algorithm in C# to perform a task, or why Python is slow and Java is faster, etc. What I'm trying to understand is: why does this matter? There are specific areas of computing where I see why performance matters: games, where tens of thousands of computations are happening every second in a constant-update loop, or low level systems which other programs rely on, such as OSs and VMs, etc. But for the normal, typical high-level business app, why does performance matter? I can understand why it used to matter, decades ago. Computers were much slower and had much less memory, so you had to think carefully about these things. But today, we have so much memory to spare and computers are so fast: does it actually matter if a particular Java algorithm is O(n^2)? Will it actually make a difference for the end users of this typical business app? When you press a GUI button in a typical business app, and behind the scenes it invokes an O(n^2) algorithm, in these days of modern computing - do you actually feel the inefficiency? My question is split in two: In practice, today does performance matter in a typical normal business program? If it does, please give me real-world examples of places in such an application, where performance and optimizations are important.

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• Why is Python used for high-performance/scientific computing (but Ruby isn't)?

  - by Cyclops

  There's a quote from a PyCon 2011 talk that goes: At least in our shop (Argonne National Laboratory) we have three accepted languages for scientific computing. In this order they are C/C++, Fortran in all its dialects, and Python. You’ll notice the absolute and total lack of Ruby, Perl, Java. It was in the more general context of high-performance computing. Granted the quote is only from one shop, but another question about languages for HPC, also lists Python as one to learn (and not Ruby). Now, I can understand C/C++ and Fortran being used in that problem-space (and Perl/Java not being used). But I'm surprised that there would be a major difference in Python and Ruby use for HPC, given that they are fairly similar. (Note - I'm a fan of Python, but have nothing against Ruby). Is there some specific reason why the one language took off? Is it about the libraries available? Some specific language features? The community? Or maybe just historical contigency, and it could have gone the other way?

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• Basics of automated tests?

  - by Muhammad Yasir

  Hi, Till now I've been testing my web (usually written in PHP) as well as desktop applications (normally Java or C#) manually. Now I read somewhere on the net about automated tests. I tried searching to know about it in details but almost all searches end up at things like PHPUnit. Could someone please put some light on the theory behind automated tests? How a software can be tested automatically? Any limitations etc? Or may be you can tell me a place where I can read about this. Regards

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• An approximate algorithm for finding Steiner Forest.

  - by Tadeusz A. Kadlubowski

  Hello. Consider a weighted graph G=(V,E,w). We are given a family of subsets of vertices V_i. Those sets of vertices are not necessarily disjoint. A Steiner Forest is a forest that for each subset of vertices V_i connects all of the vertices in this subset with a tree. Example: only one subset V_1 = V. In this case a Steiner forest is a spanning tree of the whole graph. Enough theory. Finding such a forest with minimal weight is difficult (NP-complete). Do you know any quicker approximate algorithm to find such a forest with non-optimal weight?

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• Why is this an invalid Turing machine?

  - by Danny King

  Whilst doing exam revision I am having trouble answering the following question from the book, "An Introduction to the Theory of Computation" by Sipser. Unfortunately there's no solution to this question in the book. Explain why the following is not a legitimate Turing machine. M = { The input is a polynomial p over variables x1, ..., xn Try all possible settings of x1, ..., xn to integer values Evaluate p on all of these settings If any of these settings evaluates to 0, accept; otherwise reject. } This is driving me crazy! I suspect it is because the set of integers is infinite? Does this somehow exceed the alphabet's allowable size? Thanks!

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• Solving the water jug problem

  - by Amit

  While reading through some lecture notes on preliminary number theory, I came across the solution to water jug problem (with two jugs) which is summed as thus: Using the property of the G.C.D of two numbers that GCD(a,b) is the smallest possible linear combination of a and b, and hence a certain quantity Q is only measurable by the 2 jugs, iff Q is a n*GCD(a,b), since Q=sA + tB, where: n = a positive integer A = capacity of jug A B= capacity of jug B And, then the method to the solution is discussed Another model of the solution is to model the various states as a state-space search problem as often resorted to in Artificial Intelligence. My question is: What other known methods exist which models the solution, and how? Google didn't throw up much.

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• Is it a solvable problem to generate a regular expression that matches some input set?

  - by Roman

  I provide some input set which contains known separated number of text blocks. I want to make a program that automatically generate 1 or more regular expressions each of which matches every text block in the input set. I see some relatively easy ways to implement a brute-force search. But I'm not an expert in compilers theory. That's why I'm curious: 1) is this problem solvable? or there are some principle impossibility to make such algorithm? 2) is it possible to achieve polynomial complexity for this algorithm and avoid brute forcing?

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