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  • How to create a generic C# method that can return either double or decimal?

    - by CrimsonX
    I have a method like this: private static double ComputePercentage(ushort level, ushort capacity) { double percentage; if(capacity == 1) percentage = 1; // do calculations... return percentage; } Is it possible to make it of a generic type like "type T" where it can return either decimal or double, depending on the type of method expected (or the type put into the function?) I tried something like this and I couldn't get it to work, because I cannot assign a number like "1" to a generic type. I also tried using the "where T :" after ushort capacity) but I still couldn't figure it out. private static T ComputePercentage<T>(ushort level, ushort capacity) { T percentage; if(capacity == 1) percentage = 1; // error here // do calculations... return percentage; } Is this even possible? I wasn't sure, but I thought this post might suggest that what I'm trying to do is just plain impossible.

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  • C++ performance when accessing class members

    - by Dr. Acula
    I'm writing something performance-critical and wanted to know if it could make a difference if I use: int test( int a, int b, int c ) { // Do millions of calculations with a, b, c } or class myStorage { public: int a, b, c; }; int test( myStorage values ) { // Do millions of calculations with values.a, values.b, values.c } Does this basically result in similar code? Is there an extra overhead of accessing the class members? I'm sure that this is clear to an expert in C++ so I won't try and write an unrealistic benchmark for it right now

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  • Performance when accessing class members

    - by Dr. Acula
    I'm writing something performance-critical and wanted to know if it could make a difference if I use: int test( int a, int b, int c ) { // Do millions of calculations with a, b, c } or class myStorage { public: int a, b, c; }; int test( myStorage values ) { // Do millions of calculations with values.a, values.b, values.c } Does this basically result in similar code? Is there an extra overhead of accessing the class members? I'm sure that this is clear to an expert in C++ so I won't try and write an unrealistic benchmark for it right now

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  • MATLAB: Designing a "Warm Start"

    - by squall14414
    I'm currently coding a function in MATLAB that has two steps: It processes some data It does some calculations on the processed data I'm using the function to run a series of experiments, where I tweak the way calculations occur in step 2). Seeing how I'm working with a large dataset and the data processing step takes a while each time, however, I'm wondering whether there is anyway to code in a "warm start" in the function. That is to say, is there anyway to save all the progress that I've done after step 1) so that if I run the function a second or third time, it can skip step 1) and go right to step 2)?

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  • Using calculated fields over and over again with a new table

    - by Sin5k4
    I'm fairly new to SQL and i had to do some calculations using a table.Imagine we have a table with fields : ID - Name - Val1 - Val2 ; Lets say i want to add up 2 values and add it to my query result.I can do that easily with a sub query such as: select val1+val2 as valtotal,* from my table. Now if i want to do some more process on valtotal, i use a derived table such as; select valtotal*3 as ValMoreCalculated,* from (select val1+val2 as valtotal,* from my table) AS A A bit more code maybe?? select ValMoreCalculated/valtotal as ValEvenMoreCalc ,* from (select valtotal*3 as ValMoreCalculated,* from (select val1+val2 as valtotal,* from my table) AS A)AS B So if i want to do more calculations with the ValMoreCalculated do i have to go through another derived table? Name it as B for example? Is there an easier way to achieve this in SQL? PS:the title is a bit off i know,but couldn't figure out what to name it :P

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  • Windows Azure Use Case: High-Performance Computing (HPC)

    - by BuckWoody
    This is one in a series of posts on when and where to use a distributed architecture design in your organization's computing needs. You can find the main post here: http://blogs.msdn.com/b/buckwoody/archive/2011/01/18/windows-azure-and-sql-azure-use-cases.aspx  Description: High-Performance Computing (also called Technical Computing) at its most simplistic is a layout of computer workloads where a “head node” accepts work requests, and parses them out to “worker nodes'”. This is useful in cases such as scientific simulations, drug research, MatLab work and where other large compute loads are required. It’s not the immediate-result type computing many are used to; instead, a “job” or group of work requests is sent to a cluster of computers and the worker nodes work on individual parts of the calculations and return the work to the scheduler or head node for the requestor in a batch-request fashion. This is typical to the way that many mainframe computing use-cases work. You can use commodity-based computers to create an HPC Cluster, such as the Linux application called Beowulf, and Microsoft has a server product for HPC using standard computers, called the Windows Compute Cluster that you can read more about here. The issue with HPC (from any vendor) that some organization have is the amount of compute nodes they need. Having too many results in excess infrastructure, including computers, buildings, storage, heat and so on. Having too few means that the work is slower, and takes longer to return a result to the calling application. Unless there is a consistent level of work requested, predicting the number of nodes is problematic. Implementation: Recently, Microsoft announced an internal partnership between the HPC group (Now called the Technical Computing Group) and Windows Azure. You now have two options for implementing an HPC environment using Windows. You can extend the current infrastructure you have for HPC by adding in Compute Nodes in Windows Azure, using a “Broker Node”.  You can then purchase time for adding machines, and then stop paying for them when the work is completed. This is a common pattern in groups that have a constant need for HPC, but need to “burst” that load count under certain conditions. The second option is to install only a Head Node and a Broker Node onsite, and host all Compute Nodes in Windows Azure. This is often the pattern for organizations that need HPC on a scheduled and periodic basis, such as financial analysis or actuarial table calculations. References: Blog entry on Hybrid HPC with Windows Azure: http://blogs.msdn.com/b/ignitionshowcase/archive/2010/12/13/high-performance-computing-on-premise-and-in-the-windows-azure-cloud.aspx  Links for further research on HPC, includes Windows Azure information: http://blogs.msdn.com/b/ncdevguy/archive/2011/02/16/handy-links-for-hpc-and-azure.aspx 

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  • BAM design pointers

    - by Kavitha Srinivasan
    In working recently with a large Oracle customer on SOA and BAM, I discovered that some BAM best practices are not quite well known as I had always assumed ! There is a doc bug out to formally incorporate those learnings but here are a few notes..  EMS-DO parity When using EMS (Enterprise Message Source) as a BAM feed, the best practice is to use one EMS to write to one Data Object. There is a possibility of collisions and duplicates when multiple EMS write to the same row of a DO at the same time. This customer had 17 EMS writing to one DO at the same time. Every sensor in their BPEL process writes to one topic but the Topic was read by 1 EMS corresponding to one sensor. They then used XSL within BAM to transform the payload into the BAM DO format. And hence for a given BPEL instance, 17 sensors fired, populated 1 JMS topic, was consumed by 17 EMS which in turn wrote to 1 DataObject.(You can image what would happen for later versions of the application that needs to send more information to BAM !).  We modified their design to use one Master XSL based on sensorname for all sensors relating to a DO- say Data Object 'Orders' and were able to thus reduce the 17 EMS to 1 with a master XSL. For those of you wondering about how squeaky clean this design is, you are right ! This is indeed not squeaky clean and that brings us to yet another 'inferred' best practice. (I try very hard not to state the obvious in my blogs with the hope that everytime I blog, it is very useful but this one is an exception.) Transformations and Calculations It is optimal to do transformations within an engine like BPEL. Not only does this provide modelling ease with a nice GUI XSL mapper in JDeveloper, the XSL engine in BPEL is quite efficient at runtime as well. And so, doing XSL transformations in BAM is not quite prudent.  The same is true for any non-trivial calculations as well. It is best to do all transformations,calcuations and sanitize the data in a BPEL or like layer and then send this to BAM (via JMS, WS etc.) This then delegates simply the function of report rendering and mechanics of real-time reporting to the Oracle BAM reporting tool which it is most suited to do. All nulls are not created equal Here is yet another possibly known fact but reiterated here. For an EMS with an Upsert operation: a) If Empty tags or tags with no value are sent like <Tag1/> or <Tag1></Tag1>, the DO will be overwritten with --null-- b) If Empty tags are suppressed ie not generated at all, the corresponding DO field will NOT be overwritten. The field will have whatever value existed previously.  For an EMS with an Insert operation, both tags with an empty value and no tags result in –null-- being written to the DO. Hope this helps .. Happy 4th!

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  • How does 2D Game Physics work? [closed]

    - by StefanE
    Possible Duplicate: How do I build a 2D physics engine? If we take the game Angry Birds that had big success lately I were thinking how do they implement the physics in a game like that? Your are shooting of your birds and they hit something that will fall off and in turn creating a chain reaction of things either falling or exploding.. Are all this happening with calculations with rules considering all collisions together with gravity etc.?

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  • Algorithm to find all tiles within a given radius on staggered isometric map

    - by kasztelan
    Given staggered isometric map and a start tile what would be the best way to get all surrounding tiles within given radius(middle to middle)? I can get all neighbours of a given tile and distance between each of them without any problems but I'm not sure what path to take after that. This feature will be used quite often (along with A*) so I'd like to avoid unecessary calculations. If it makes any difference I'm using XNA and each tile is 64x32 pixels.

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  • BizTalk 2009 - Custom Functoid Categories

    - by StuartBrierley
    I recently had cause to code a number of custom functoids to aid with some maps that I was writing. Once these were developed and deployed to C:\Program Files\Microsoft BizTalk Server 2009\Developer Tools\Mapper Extensions a quick refresh allowed them to appear in toolbox.  After dropping these on a map and configuring the appropriate inputs I tested the map to check that they worked as expected.  All but one of the functoids worked as expecetd, but the final functoid appeared not to be firing at all. I had already tested the code used in a simple test harness application, so I was confident in the code used, but I still needed to figure out what the problem might be. Debugging the map helped me on the way; for some reason the functoid in question was not shown correctly - the functoid definition was wrong. After some investigations I found that the functoid type you assign when coding a custom functoid affects more than just the category it appears in; different functoid types have different capabilities, including what they can link too.  For example, a logical functoid can not provide content for an output element, it can only say whether the element exists.  Map this via a Value Mapping functoid and the value of true or false can be seen in the output element. The functoid I was having problems with was one whare I had used the XPath functoid type, this had seemed to be a good fit as I was looking up content in a config file using xpath and I wanted it to appear the advanced area.  From the table below you can see that this functoid type is marked as "Internal Only", preventing it from being used for custom functoids.  Changing my type to String allowed the functoid to function as expected. Category Description Toolbox Group Assert Internal Use Only Advanced Conversion Converts characters to and from numerics and converts numbers from one base to another. Conversion Count Internal Use Only Advanced Cumulative Performs accumulations of the value of a field that occurs multiple times in a source document and outputs a single output. Cumulative DatabaseExtract Internal Use Only Database DatabaseLookup Internal Use Only Database DateTime Adds date, time, date and time, or add days to a specified date, in output data. Date/Time ExistenceLooping Internal Use Only Advanced Index Internal Use Only Advanced Iteration Internal Use Only Advanced Keymatch Internal Use Only Advanced Logical Controls conditional behavior of other functoids to determine whether particular output data is created. Logical Looping Internal Use Only Advanced MassCopy Internal Use Only Advanced Math Performs specific numeric calculations such as addition, multiplication, and division. Mathematical NilValue Internal Use Only Advanced Scientific Performs specific scientific calculations such as logarithmic, exponential, and trigonometric functions. Scientific Scripter Internal Use Only Advanced String Manipulates data strings by using well-known string functions such as concatenation, length, find, and trim. String TableExtractor Internal Use Only Advanced TableLooping Internal Use Only Advanced Unknown Internal Use Only Advanced ValueMapping Internal Use Only Advanced XPath Internal Use Only Advanced Links http://msdn.microsoft.com/en-us/library/microsoft.biztalk.basefunctoids.functoidcategory(BTS.20).aspx http://blog.eliasen.dk/CommentView,guid,d33b686b-b059-4381-a0e7-1c56e808f7f0.aspx

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  • A Real-Time HPC Approach for Optimizing Multicore Architectures

    Complex math is at the heart of many of the biggest technical challenges. With multicore processors, the type of calculations that would have required a supercomputer can now be performed in real-time, embedded environments. High-performance computing - Supercomputer - Real-time computing - Operating system - Companies

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  • Robust line of sight test on the inside of a polygon with tolerance

    - by David Gouveia
    Foreword This is a followup to this question and the main problem I'm trying to solve. My current solution is an hack which involves inflating the polygon, and doing most calculations on the inflated polygon instead. My goal is to remove this step completely, and correctly solve the problem with calculations only. Problem Given a concave polygon and treating all of its edges as if they were walls in a level, determine whether two points A and B are in line of sight of each other, while accounting for some degree of floating point errors. I'm currently basing my solution on a series of line-segment interection tests. In other words: If any of the end points are outside the polygon, they are not in line of sight. If both end points are inside the polygon, and the line segment from A to B crosses any of the edges from the polygon, then they are not in line of sight. If both end points are inside the polygon, and the line segment from A to B does not cross any of the edges from the polygon, then they are in line of sight. But the problem is dealing correctly with all the edge cases. In particular, it must be able to deal with all the situations depicted below, where red lines are examples that should be rejected, and green lines are examples that should be accepted. I probably missed a few other situations, such as when the line segment from A to B is colinear with an edge, but one of the end points is outside the polygon. One point of particular interest is the difference between 1 and 9. In both cases, both end points are vertices of the polygon, and there are no edges being intersected, but 1 should be rejected while 9 should be accepted. How to distinguish these two? I could check some middle point within the segment to see if it falls inside or not, but it's easy to come up with situations in which it would fail. Point 7 was also pretty tricky and I had to to treat it as a special case, which checks if two points are adjacent vertices of the polygon directly. But there are also other chances of line segments being col linear with the edges of the polygon, and I'm still not entirely sure how I should handle those cases. Is there any well known solution to this problem?

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  • Infix vs Prefix Notation - Which do you prefer?

    - by Jetti
    I have been learning Clojure and looking at Scheme and CL which introduced me to the world of prefix notation. At first I didn't like it but it is still starting to grow on me. To be honest though, there are still long calculations that are difficult for me to understand but I think that is an issue of me needing more exposure/practice and I'll get it. But that leads me to the question: Which type of notation do you prefer and why?

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  • ssao implementation

    - by Irbis
    I try to implement a ssao based on this tutorial: link I use a deferred rendering and world coordinates for shading calculations. When saving gbuffer a vertex shader output looks like this: worldPosition = vec3(ModelMatrix * vec4(inPosition, 1.0)); normal = normalize(normalModelMatrix * inNormal); gl_Position = ProjectionMatrix * ViewMatrix * ModelMatrix * vec4(inPosition, 1.0); Next for a ssao calculations I render a scene as a full screen quad and I save an occlusion parameter in a texture. (Vertex positions in the world space: link Normals in the world space: link) SSAO implementation: subroutine (RenderPassType) void ssao() { vec2 texCoord = CalcTexCoord(); vec3 worldPos = texture(texture0, texCoord).xyz; vec3 normal = normalize(texture(texture1, texCoord).xyz); vec2 noiseScale = vec2(screenSize.x / 4, screenSize.y / 4); vec3 rvec = texture(texture2, texCoord * noiseScale).xyz; vec3 tangent = normalize(rvec - normal * dot(rvec, normal)); vec3 bitangent = cross(normal, tangent); mat3 tbn = mat3(tangent, bitangent, normal); float occlusion = 0.0; float radius = 4.0; for (int i = 0; i < kernelSize; ++i) { vec3 pix = tbn * kernel[i]; pix = pix * radius + worldPos; vec4 offset = vec4(pix, 1.0); offset = ProjectionMatrix * ViewMatrix * offset; offset.xy /= offset.w; offset.xy = offset.xy * 0.5 + 0.5; float sample_depth = texture(texture0, offset.xy).z; float range_check = abs(worldPos.z - sample_depth) < radius ? 1.0 : 0.0; occlusion += (sample_depth <= pix.z ? 1.0 : 0.0); } outputColor = vec4(occlusion, occlusion, occlusion, 1); } That code gives following results: camera looking towards -z world space: link camera looking towards +z world space: link I wonder if it is possible to use world coordinates in the above code ? When I move camera I get different results because world space positions don't change. Can I treat worldPos.z as a linear depth ? What should I change to get a correct results ? I except the white areas in place of occlusion, so the ground should has the white areas only near to the object.

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  • Stock Analysis and Moving Average with PowerPivot

    - by Marco Russo (SQLBI)
    One week ago Alberto Ferrari wrote a post about how to do working days calculation in PowerPivot . You might think this is necessary only for accounting department or something like that… but in reality the same techniques are really useful to implement calculations that might be useful when you want to implement some stock analysis using PowerPivot and Excel! As you might know, in PowerPivot it is important having a Dates table containing all the days, without exceptions. But when you manage stock...(read more)

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  • Any command line calculator for Ubuntu?

    - by AgentCool
    I am looking for a Calculator which can do calculations in the terminal itself without any other extra prefixes and suffixes. For example: If I typed something like 10000-9000 in the terminal, the answer should come out as 1000. Once again I am saying, I just need a quick calculator in terminal, without any characters added. I know if I switch to Python, it can do that but I don't want it in such a way.

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  • Help with calculation to steer ship in 3d space

    - by Aaron Anodide
    I'm a beginner using XNA to try and make a 3D Asteroids game. I'm really close to having my space ship drive around as if it had thrusters for pitch and yaw. The problem is I can't quite figure out how to translate the rotations, for instance, when I pitch forward 45 degrees and then start to turn - in this case there should be rotation being applied to all three directions to get the "diagonal yaw" - right? I thought I had it right with the calculations below, but they cause a partly pitched forward ship to wobble instead of turn.... :( Here's current (almost working) calculations for the Rotation acceleration: float accel = .75f; // Thrust +Y / Forward if (currentKeyboardState.IsKeyDown(Keys.I)) { this.ship.AccelerationY += (float)Math.Cos(this.ship.RotationZ) * accel; this.ship.AccelerationX += (float)Math.Sin(this.ship.RotationZ) * -accel; this.ship.AccelerationZ += (float)Math.Sin(this.ship.RotationX) * accel; } // Rotation +Z / Yaw if (currentKeyboardState.IsKeyDown(Keys.J)) { this.ship.RotationAccelerationZ += (float)Math.Cos(this.ship.RotationX) * accel; this.ship.RotationAccelerationY += (float)Math.Sin(this.ship.RotationX) * accel; this.ship.RotationAccelerationX += (float)Math.Sin(this.ship.RotationY) * accel; } // Rotation -Z / Yaw if (currentKeyboardState.IsKeyDown(Keys.K)) { this.ship.RotationAccelerationZ += (float)Math.Cos(this.ship.RotationX) * -accel; this.ship.RotationAccelerationY += (float)Math.Sin(this.ship.RotationX) * -accel; this.ship.RotationAccelerationX += (float)Math.Sin(this.ship.RotationY) * -accel; } // Rotation +X / Pitch if (currentKeyboardState.IsKeyDown(Keys.F)) { this.ship.RotationAccelerationX += accel; } // Rotation -X / Pitch if (currentKeyboardState.IsKeyDown(Keys.D)) { this.ship.RotationAccelerationX -= accel; } I'm combining that with drawing code that does a rotation to the model: public void Draw(Matrix world, Matrix view, Matrix projection, TimeSpan elsapsedTime) { float seconds = (float)elsapsedTime.TotalSeconds; // update velocity based on acceleration this.VelocityX += this.AccelerationX * seconds; this.VelocityY += this.AccelerationY * seconds; this.VelocityZ += this.AccelerationZ * seconds; // update position based on velocity this.PositionX += this.VelocityX * seconds; this.PositionY += this.VelocityY * seconds; this.PositionZ += this.VelocityZ * seconds; // update rotational velocity based on rotational acceleration this.RotationVelocityX += this.RotationAccelerationX * seconds; this.RotationVelocityY += this.RotationAccelerationY * seconds; this.RotationVelocityZ += this.RotationAccelerationZ * seconds; // update rotation based on rotational velocity this.RotationX += this.RotationVelocityX * seconds; this.RotationY += this.RotationVelocityY * seconds; this.RotationZ += this.RotationVelocityZ * seconds; Matrix translation = Matrix.CreateTranslation(PositionX, PositionY, PositionZ); Matrix rotation = Matrix.CreateRotationX(RotationX) * Matrix.CreateRotationY(RotationY) * Matrix.CreateRotationZ(RotationZ); model.Root.Transform = rotation * translation * world; model.CopyAbsoluteBoneTransformsTo(boneTransforms); foreach (ModelMesh mesh in model.Meshes) { foreach (BasicEffect effect in mesh.Effects) { effect.World = boneTransforms[mesh.ParentBone.Index]; effect.View = view; effect.Projection = projection; effect.EnableDefaultLighting(); } mesh.Draw(); } }

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  • Pathfinding in Warcraft 1

    - by Valmond
    Dijkstra and A* are all nice and popular but what kind of algorithm was used in Warcraft 1 for pathfinding? I remember that the enemy could get trapped in bowl-like caverns which means there were (most probably) no full-path calculations from "start to end". If I recall correctly, the algorithm could be something like this: A) Move towards enemy until success or hitting a wall B) If blocked by a wall, follow the wall until you can move towards the enemy without being blocked and then do A) But I'd like to know, if someone knows :-)

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  • How to decompose a rectangular shape in a Voronoi diagram, only generating convex shapes?

    - by DevilWithin
    I think this is a very straighforward question, lets say i have a building in 2D, a rectangle shape. Now i want to decompose that area in a lot of convex shapes, as seen in a voronoi diagram, or closely like it, just so I can add those shapes to the physics engine, and have a realistic destruction. Bonus: Possible suggestions on how to make the effect more dynamic and interesting. Please keep in mind we re talking about realtime calculations..

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  • Why Are We Still Using CPUs Instead of GPUs?

    - by Jason Fitzpatrick
    Increasingly GPUs are being used for non-graphical tasks like risk computations, fluid dynamics calculations, and seismic analysis. What’s to stop us from adopting GPU-driven devices? Today’s Question & Answer session comes to us courtesy of SuperUser—a subdivision of Stack Exchange, a community-drive grouping of Q&A web sites. 6 Ways Windows 8 Is More Secure Than Windows 7 HTG Explains: Why It’s Good That Your Computer’s RAM Is Full 10 Awesome Improvements For Desktop Users in Windows 8

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  • Stairway to MDX - Level 2: The Ordinal Function

    Business Intelligence Architect Bill Pearson introduces the MDX Ordinal Function, as a means for generating lists and for conditionally presenting calculations. He also demonstrates the use of the function in creating datasets to support report parameter picklists. Develop seamlessly between Management Studio and Visual StudioSQL Connect is a Visual Studio add-in that makes it easy to keep your database and Visual Studio project in sync.

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  • Properly Analyze the Value of the Cloud

    Most analyses of the benefits of cloud computing are based on unrealistic total cost of ownership (TCO), return on investment (ROI), and capex/opex calculations. To fully understand the potential benefits of cloud computing, a new metric is required.

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  • Is basing storage requirements based on IOPS sufficient?

    - by Boden
    The current system in question is running SBS 2003, and is going to be migrated on new hardware to SBS 2008. Currently I'm seeing on average 200-300 disk transfers per second total across all the arrays in the system. The array seeing the bulk of activity is a 6 disk 7200RPM RAID 6 and it struggles to keep up during high traffic times (idle time often only 10-20%; response times peaking 20-50+ ms). Based on some rough calculations this makes sense (avg ~245 IOPS on this array at 70/30 read to write ratio). I'm considering using a much simpler disk configuration using a single RAID 10 array of 10K disks. Using the same parameters for my calculations above, I'm getting 583 average random IOPS / sec. Granted SBS 2008 is not the same beast as 2003, but I'd like to make the assumption that it'll be similar in terms of disk performance, if not better (Exchange 2007 is easier on the disk and there's no ISA server). Am I correct in believing that the proposed system will be sufficient in terms of performance, or am I missing something? I've read so much about recommended disk configurations for various products like Exchange, and they often mention things like dedicating spindles to logs, etc. I understand the reasoning behind this, but if I've got more than enough random I/O overhead, does it really matter? I've always at the very least had separate spindles for the OS, but I could really reduce cost and complexity if I just had a single, good performing array. So as not to make you guys do my job for me, the generic version of this question is: if I have a projected IOPS figure for a new system, is it sufficient to use this value alone to spec the storage, ignoring "best practice" configurations? (given similar technology, not going from DAS to SAN or anything)

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  • How do I calculate clock speed in multi-core processors?

    - by NReilingh
    Is it correct to say, for example, that a processor with four cores each running at 3GHz is in fact a processor running at 12GHz? I once got into a "Mac vs. PC" argument (which by the way is NOT the focus of this topic... that was back in middle school) with an acquaintance who insisted that Macs were only being advertised as 1Ghz machines because they were dual-processor G4s each running at 500MHz. At the time I knew this to be hogwash for reasons I think are apparent to most people, but I just saw a comment on this website to the effect of "6 cores x 0.2GHz = 1.2Ghz" and that got me thinking again about whether there's a real answer to this. So, this is a more-or-less philosophical/deep technical question about the semantics of clock speed calculation. I see two possibilities: Each core is in fact doing x calculations per second, thus the total number of calculations is x(cores). Clock speed is rather a count of the number of cycles the processor goes through in the space of a second, so as long as all cores are running at the same speed, the speed of each clock cycle stays the same no matter how many cores exist. In other words, Hz = (core1Hz+core2Hz+...)/cores.

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  • What is the peak theoretical WiFi G user density? [closed]

    - by Bigbio2002
    I've seen a few WiFi capacity planning questions, and this one is related, but hopefully different enough not to be closed. Also, this is related specifically to 802.11g, but a similar question could be made for N. In order to squeeze more WiFi users into a space, the transmit power on the APs need to be reduced and the APs squeezed closer together. My question is, how far can you practically take this before the network becomes unusable? There will come a point where the transmit power is so weak that nobody will actually be able to pick up a connection, or be constantly roaming to/from APs spaced a few feet apart as they walk around. There are also only 3 available channels to use as well, which is a factor to consider. After determining the peak AP density, then multiply by users-per-AP, which should be easier to find out. After factoring all of this in and running some back-of-the-envelope calculations, I'd like to be able to get a figure of "XX users per 10ft^2" or something. This can be considered the physical limit of WiFi, and will keep people from asking about getting 3,000 people in a ballroom conference on WiFi. Can anyone with WiFi experience chime in, or better yet, provide some calculations for a more accurate figure? Assumptions: Let's assume an ideal environment with no reflection (think of a big, square, open room, with the APs spaced out on a plane), APs are placed on the ceiling so humans won't absorb the waves, and the only interference are from the APs themselves and the devices. As for what devices specifically, that's irrelevant for the first point of the question (AP density, so only channel and transmit power should matter). User experience: Wikipedia states that Wireless G has about 22Mbps maximum effective throughput, or about 2.75MB/s. For the purpose of this question, anything below 100KB/s per user can be deemed to be a poor user experience. As for roaming, I'll assume the user is standing in the same place, so hopefully that will be a non-issue.

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