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  • Organization &amp; Architecture UNISA Studies &ndash; Chap 4

    - by MarkPearl
    Learning Outcomes Explain the characteristics of memory systems Describe the memory hierarchy Discuss cache memory principles Discuss issues relevant to cache design Describe the cache organization of the Pentium Computer Memory Systems There are key characteristics of memory… Location – internal or external Capacity – expressed in terms of bytes Unit of Transfer – the number of bits read out of or written into memory at a time Access Method – sequential, direct, random or associative From a users perspective the two most important characteristics of memory are… Capacity Performance – access time, memory cycle time, transfer rate The trade off for memory happens along three axis… Faster access time, greater cost per bit Greater capacity, smaller cost per bit Greater capacity, slower access time This leads to people using a tiered approach in their use of memory   As one goes down the hierarchy, the following occurs… Decreasing cost per bit Increasing capacity Increasing access time Decreasing frequency of access of the memory by the processor The use of two levels of memory to reduce average access time works in principle, but only if conditions 1 to 4 apply. A variety of technologies exist that allow us to accomplish this. Thus it is possible to organize data across the hierarchy such that the percentage of accesses to each successively lower level is substantially less than that of the level above. A portion of main memory can be used as a buffer to hold data temporarily that is to be read out to disk. This is sometimes referred to as a disk cache and improves performance in two ways… Disk writes are clustered. Instead of many small transfers of data, we have a few large transfers of data. This improves disk performance and minimizes processor involvement. Some data designed for write-out may be referenced by a program before the next dump to disk. In that case the data is retrieved rapidly from the software cache rather than slowly from disk. Cache Memory Principles Cache memory is substantially faster than main memory. A caching system works as follows.. When a processor attempts to read a word of memory, a check is made to see if this in in cache memory… If it is, the data is supplied, If it is not in the cache, a block of main memory, consisting of a fixed number of words is loaded to the cache. Because of the phenomenon of locality of references, when a block of data is fetched into the cache, it is likely that there will be future references to that same memory location or to other words in the block. Elements of Cache Design While there are a large number of cache implementations, there are a few basic design elements that serve to classify and differentiate cache architectures… Cache Addresses Cache Size Mapping Function Replacement Algorithm Write Policy Line Size Number of Caches Cache Addresses Almost all non-embedded processors support virtual memory. Virtual memory in essence allows a program to address memory from a logical point of view without needing to worry about the amount of physical memory available. When virtual addresses are used the designer may choose to place the cache between the MMU (memory management unit) and the processor or between the MMU and main memory. The disadvantage of virtual memory is that most virtual memory systems supply each application with the same virtual memory address space (each application sees virtual memory starting at memory address 0), which means the cache memory must be completely flushed with each application context switch or extra bits must be added to each line of the cache to identify which virtual address space the address refers to. Cache Size We would like the size of the cache to be small enough so that the overall average cost per bit is close to that of main memory alone and large enough so that the overall average access time is close to that of the cache alone. Also, larger caches are slightly slower than smaller ones. Mapping Function Because there are fewer cache lines than main memory blocks, an algorithm is needed for mapping main memory blocks into cache lines. The choice of mapping function dictates how the cache is organized. Three techniques can be used… Direct – simplest technique, maps each block of main memory into only one possible cache line Associative – Each main memory block to be loaded into any line of the cache Set Associative – exhibits the strengths of both the direct and associative approaches while reducing their disadvantages For detailed explanations of each approach – read the text book (page 148 – 154) Replacement Algorithm For associative and set associating mapping a replacement algorithm is needed to determine which of the existing blocks in the cache must be replaced by a new block. There are four common approaches… LRU (Least recently used) FIFO (First in first out) LFU (Least frequently used) Random selection Write Policy When a block resident in the cache is to be replaced, there are two cases to consider If no writes to that block have happened in the cache – discard it If a write has occurred, a process needs to be initiated where the changes in the cache are propagated back to the main memory. There are several approaches to achieve this including… Write Through – all writes to the cache are done to the main memory as well at the point of the change Write Back – when a block is replaced, all dirty bits are written back to main memory The problem is complicated when we have multiple caches, there are techniques to accommodate for this but I have not summarized them. Line Size When a block of data is retrieved and placed in the cache, not only the desired word but also some number of adjacent words are retrieved. As the block size increases from very small to larger sizes, the hit ratio will at first increase because of the principle of locality, which states that the data in the vicinity of a referenced word are likely to be referenced in the near future. As the block size increases, more useful data are brought into cache. The hit ratio will begin to decrease as the block becomes even bigger and the probability of using the newly fetched information becomes less than the probability of using the newly fetched information that has to be replaced. Two specific effects come into play… Larger blocks reduce the number of blocks that fit into a cache. Because each block fetch overwrites older cache contents, a small number of blocks results in data being overwritten shortly after they are fetched. As a block becomes larger, each additional word is farther from the requested word and therefore less likely to be needed in the near future. The relationship between block size and hit ratio is complex, and no set approach is judged to be the best in all circumstances.   Pentium 4 and ARM cache organizations The processor core consists of four major components: Fetch/decode unit – fetches program instruction in order from the L2 cache, decodes these into a series of micro-operations, and stores the results in the L2 instruction cache Out-of-order execution logic – Schedules execution of the micro-operations subject to data dependencies and resource availability – thus micro-operations may be scheduled for execution in a different order than they were fetched from the instruction stream. As time permits, this unit schedules speculative execution of micro-operations that may be required in the future Execution units – These units execute micro-operations, fetching the required data from the L1 data cache and temporarily storing results in registers Memory subsystem – This unit includes the L2 and L3 caches and the system bus, which is used to access main memory when the L1 and L2 caches have a cache miss and to access the system I/O resources

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  • JavaScript 3D space ship rotation

    - by user36202
    I am working with a fairly low-level JavaScript 3D API (not Three.js) which uses euler angles for rotation. In most cases, euler angles work quite well for doing things like aligning buildings, operating a hovercraft, or looking around in the first-person. However, in space there is no up or down. I want to control the ship's roll, pitch, and yaw. To do that, some people would use a local coordinate system or a permenant matrix or quaternion or whatever to represent the ship's angle. However, since I am not most people and am using a library that deals exclusively in euler angles, I will be using relative angles to represent how to rotate the ship in space and getting the resulting non-relative euler angles. For you math nerds, that means I need to convert 3 euler angles (with Y being the vertical axis, X representing the pitch, and Z representing a roll which is unaffected by the other angles, left-handed system) into a 3x3 orientation matrix, do something fancy with the matrix, and convert it back into the 3 euler angles. Euler to matrix to euler. Somebody has posted something similar to this on SO (http://stackoverflow.com/questions/1217775/rotating-a-spaceship-model-for-a-space-simulator-game) but he ended up just working with a matrix. This will not do for me. Also, I am using JavaScript, not C++. What I want essentially are the functions do_roll, do_pitch, and do_yaw which only take in and put out euler angles. Many thanks.

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  • SEO For Ecommerce Sites

    Ecommerce is a fancy name for just about any business that can be conducted via the internet or other computer systems. The global internet explosion has changed the face of the ecommerce industry for good, increasing both potential profits and the ferocity of competition across virtually every consumer market.

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  • Fast determination of whether objects are onscreen in 2D

    - by Ben Ezard
    So currently, I have this in each object's renderer's update method: float a = transform.position.x * Main.scale; float b = transform.position.y * Main.scale; float c = Camera.main.transform.position.x * Main.scale; float d = Camera.main.transform.position.y * Main.scale; onscreen = a + width - c > 0 && a - c < GameView.width && b + height - d > 0 && b - d < GameView.height; transform.position is a 2D vector containing the game engine's definition of where the object is - this is then multiplied by Main.scale to translate that coordinate into actual screen space Similarly, Camera.main.transform.position is the in-engine representation of where the main camera is, and this is also multiplied by Main.scale The problem is, as my game is tile-based, thousands of these updates get called every frame, just to determine whether or not each object should be drawn - how can I improve this please?

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  • " this kernel required an X86-64 CPU, but only detected a i686 CPU"

    - by jy19
    I recently decided to use Virtualbox to run Ubuntu, but I get the message this kernel required an X86-64 CPU, but only detected a i686 CPU I've already enabled virtualization in BIOS, but that doesn't seem to work. Many other solutions suggest that I should download the 32-bit version, and not the 64-bit. I'm not sure about that though, since my computer clearly says "64-bit operating system" under systems. But I might just be mistaken.

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  • Extracting Frustum Planes (Hartmann & Gribbs method)

    - by DAVco
    I have been grappling with the Hartmann/Gribbs method of extracting the Frustum planes for some time now, with little success. There doesn't appear to be a "definitive" topic or tutorial which combines all the necessary information, so perhaps this can be it First of all, I am attempting to do this in C# (For Playstation Mobile), using OpenGL style Column-Major matrices in a Right-Handed coordinate system but obviously the math will work in any language. My projection matrix has a Near plane at 1.0, Far plane at 1000, FOV of 45.0 and Aspect of 1.7647. I want to get my planes in World-Space, so I build my frustum from the View-Projection Matrix (that's projectionMatrix * viewMatrix). The view Matrix is the inverse of the camera's World-Transform. The problem is; regardless of what I tweak, I can't seem to get a correct frustum. I think that I may be missing something obvious. Focusing on the Near and Far planes for the moment (since they have the most obvious normals when correct), when my camera is positioned looking down the negative z-axis, I get two planes facing in the same direction, rather than opposite directions. If i strafe my camera left and right (while still looking along the z axis) the x value of the normal vector changes. Obviously, something is fundamentally wrong here; I just can't figure out what - maybe someone here can?

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  • Collision checking problem on a Tiled map

    - by nosferat
    I'm working on a pacman styled dungeon crawler, using the free oryx sprites. I've created the map using Tiled, separating the floor, walls and treasure in three different layers. After importing the map in libGDX, it renders fine. I also added the player character, for now it just moves into one direction, the player cannot control it yet. I wanted to add collision and I was planning to do this by checking if the player's new position is on a wall tile. Therefore as you can see in the following code snippet, I get the tile type of the appropriate tile and if it is not zero (since on that layer there is nothing except the wall tile) it is a collision and the player cannot move further: final Vector2 newPos = charController.move(warrior.getX(), warrior.getY()); if(!collided(newPos)) { warrior.setPosition(newPos.x, newPos.y); warrior.flip(charController.flipX(), charController.flipY()); } [..] private boolean collided(Vector2 newPos) { int row = (int) Math.floor((newPos.x / 32)); int col = (int) Math.floor((newPos.y / 32)); int tileType = tiledMap.layers.get(1).tiles[row][col]; if (tileType == 0) { return false; } return true; } The character only moves one tile with this code: If I reduce the col value by two it two more tiles. I think the problem will be around indexing, but I'm totally confused because the zero in the coordinate system of libGDX is in the bottom left corner of the screen, and I don't know the tiles array's indexing is similair or not. The size of the map is 19x21 tiles and looks like the following (the starting position of the player is marked with blue:

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  • Maximizing the Value of Software

    - by David Dorf
    A few years ago we decided to increase our investments in documenting retail processes and architectures.  There were several goals but the main two were to help retailers maximize the value they derive from our software and help system integrators implement our software faster.  The sale is only part of our success metric -- its actually more important that the customer realize the benefits of the software.  That's when we actually celebrate. This week many of our customers are gathered in Chicago to discuss their successes during our annual Crosstalk conference.  That provides the perfect forum to announce the release of the Oracle Retail Reference Library.  The RRL is available for free to Oracle Retail customers and partners.  It contains 1000s of hours of work and represents years of experience in the retail industry.  The Retail Reference Library is composed of three offerings: Retail Reference Model We've been sharing the RRM for several years now, with lots of accolades.  The RRM is a set of business process diagrams at varying levels of granularity. This release marks the debut of Visio documents, which should make it easier for retailers to adopt and edit the diagrams.  The processes represent an approximation of the Oracle Retail software, but at higher levels they are pretty generic and therefore usable with other software as well.  Using these processes, the business and IT are better able to communicate the expectations of the software.  They can be used to guide customization when necessary, and help identify areas for optimization in the organization. Retail Reference Architecture When embarking on a software implementation project, it can be daunting to start from a blank sheet of paper.  So we offer the RRA, a comprehensive set of documents that describe the retail enterprise in terms of logical architecture, physical deployments, and systems integration.  These documents and diagrams describe how all the systems typically found in a retailer enterprise work together.  They serve as a way to jump-start implementations using best practices we've captured over the years. Retail Semantic Glossary Have you ever seen two people argue over something because they're using misaligned terminology?  Its a huge waste and happens all the time.  The Retail Semantic Glossary is a simple application that allows retailers to define terms and metrics in a centralized database.  This initial version comes with limited content with the goal of adding more over subsequent releases.  This is the single source for defining key performance indicators, metrics, algorithms, and terms so that the retail organization speaks in a consistent language. These three offerings are downloaded from MyOracleSupport separately and linked together using the start page above.  Everything is navigated using a Web browser.  See the Oracle Retail Documentation blog for more details.

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  • Enable Seamless Transformation and Effective Adoption of Change with Oracle User Productivity Kit

    Organizations go through continuous transformation and change - whether it is through mergers and acquisitions, standardizations of systems, a rollout of a new application or business process improvements. With Oracle User Productivity Kit, project teams can capture and deploy best practices to streamline efficiency, reduce cost, and ensure successful change adoption. Discover how organizations can leverage the multiple outputs of Oracle UPK for all phases of the project from blueprinting/design/configuration to testing/training/go-live as well as maintenance and support.

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  • This Week on the Green Data Center Management Front

    Among the big news this week for those looking to make their data center more environmentally friendly: Two IBM POWER7-based servers become the first four-processor systems in the industry to qualify for Energy Star status; NetApp announces plans to have execs, and other on hand to discuss green computing at SNW Spring 2010; and the feds are examining how cloud will save money and energy.

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  • Les risques du Cloud sont plus importants que ses avantages, pour les responsables IT interrogés par

    Mise à jour du 08/04/10 [Les commentaires sur cette mise à jour commencent ici] Les risques du Cloud Computing sont plus grands que ses avantages Pour les responsables IT interrogés par l'ISACA Près de la moitié (45%) des responsables IT interrogés dans une étude de l'ISACA (la Information Systems Audit and Control Association) considèrent que les risques liés au Cloud Computing sont plus importants que ses avantages, 38% pensent que risques et bénéfices s'équilibrent, et seulement 12% pensent que...

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  • XSIGO Product Training Now Available

    - by Cinzia Mascanzoni
    Xsigo Sales and Pre-Sales training is available via iLearning for partners registered in OPN Server and Storage Systems Knowledge Zones. The recommended online training sessions provide sales training solutions that equip partners with the product knowledge, market knowledge and selling strategies to help achieve their revenue targets. Partners are invited to learn more here: Sales Training: Product Essentials For Sales - Oracle Virtual Networking Pre-Sales Training and Product Essentials For Sales Consultants - Oracle Virtual Networking.

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  • Well-tested libraries for player ratings?

    - by Lucky
    It's common in games to implement some sort of numerical ranking system -- the ELO system is usually used in chess. I could implement this system naively using Wikipedia's descriptions, but I suspect that this would open up a whole box of problems that have already been solved: rating inflation, etc -- for instance, the ELO system has a K constant that's 'fudged' according to rating, duration, pairings, statistics, ... What are some libraries (I'm looking at Python, but anything is okay) that implements rating systems? It also doesn't have to be ELO.

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  • Change Management and Source Control

    So, given the many good reasons for using Version Control systems for managing the changes in database applications, how does one go about the rather different routines of team development, such as testing, continuous integration, and managing data? What are the issues that you're likely to face? The Future of SQL Server Monitoring "Being web-based, SQL Monitor 2.0 enables you to check on your servers from almost any location" Jonathan Allen.Try SQL Monitor now.

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  • How do I compile & install the newest version of Transmission?

    - by Codemonkey
    I'm trying to install Transmission 2.51 on Ubuntu 10.04. Compiling the source goes fine, but I can't seem to get it to compile the GUI as well. This is the configure output: Configuration: Source code location: . Compiler: g++ Build libtransmission: yes * optimized for low-resource systems: no * µTP enabled: yes Build Command-Line client: yes Build GTK+ client: no (GTK+ none) * libappindicator for an Ubuntu-style tray: no Build Daemon: yes Build Mac client: no How do I get it to build the GTK+ client?

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  • SQL Server Database Settings

    - by rbishop
    For those using Data Relationship Management on Oracle DB this does not apply, but for those using Microsoft SQL Server it is highly recommended that you run with Snapshot Isolation Mode. The Data Governance module will not function correctly without this mode enabled. All new Data Relationship Management repositories are created with this mode enabled by default. This mode makes SQL Server (2005+) behave more like Oracle DB where readers simply see older versions of rows while a write is in progress, instead of readers being blocked by locks while a write takes place. Many common sources of deadlocks are eliminated. For example, if one user starts a 5 minute transaction updating half the rows in a table, without snapshot isolation everyone else reading the table will be blocked waiting. With snapshot isolation, they will see the rows as they were before the write transaction started. Conversely, if the readers had started first, the writer won't be stuck waiting for them to finish reading... the writes can begin immediately without affecting the current transactions. To make this change, make sure no one is using the target database (eg: put it into single-user mode), then run these commands: ALTER DATABASE [DB] SET ALLOW_SNAPSHOT_ISOLATION ONALTER DATABASE [DB] SET READ_COMMITTED_SNAPSHOT ON Please make sure you coordinate with your DBA team to ensure tempdb is appropriately setup to support snapshot isolation mode, as the extra row versions are stored in tempdb until the transactions are committed. Let me take this opportunity to extremely strongly highly recommend that you use solid state storage for your databases with appropriate iSCSI, FiberChannel, or SAN bandwidth. The performance gains are significant and there is no excuse for not using 100% solid state storage in 2013. Actually unless you need to store petabytes of archival data, there is no excuse for using hard drives in any systems, whether laptops, desktops, application servers, or database servers. The productivity benefits alone are tremendous, not to mention power consumption, heat, etc.

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  • OpenGL + Allegro. Moving from software drawing X Y to openGL is confusing

    - by Aaron
    Having a fair bit of trouble. I'm used to Allegro and drawing sprites on a bitmap buffer at X Y coords. Now I've started a test project with OpenGL and its weird. Basically, as far as I know, theirs many ways to draw stuff in OpenGL. At the moment, I think I'm creating a Quad? Whatever that is, and I think Ive given it a texture of a bitmap and them im drawing that: GLuint gl_image; bitmap = load_bitmap("cat.bmp", NULL); gl_image = allegro_gl_make_texture_ex(AGL_TEXTURE_MASKED, bitmap, GL_RGBA); glBindTexture(GL_TEXTURE_2D, gl_image); glBegin(GL_QUADS); glColor4ub(255, 255, 255, 255); glTexCoord2f(0, 0); glVertex3f(-0.5, 0.5, 0); glTexCoord2f(1, 0); glVertex3f(0.5, 0.5, 0); glTexCoord2f(1, 1); glVertex3f(0.5, -0.5, 0); glTexCoord2f(0, 1); glVertex3f(-0.5, -0.5, 0); glEnd(); So yeah. So I got a few questions: Is this the best way of drawing a sprite? Is it suitable? The big question: Can anyone help / Does anyone know any tutorials on this weird coordinate thing? If it even is that. It's vastly different from XY, but I want to learn it. I was thinking maybe I could learn how this weird positioning stuff works, and then write a function to try and translate it to X and Y coords. Thats about it. I'm still trying to figure it all out on my own but any contributions you guys can make would be greatly appreciated =D Thanks!

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  • Algorithm to shoot at a target in a 3d game

    - by Sebastian Bugiu
    For those of you remembering Descent Freespace it had a nice feature to help you aim at the enemy when shooting non-homing missiles or lasers: it showed a crosshair in front of the ship you chased telling you where to shoot in order to hit the moving target. I tried using the answer from http://stackoverflow.com/questions/4107403/ai-algorithm-to-shoot-at-a-target-in-a-2d-game?lq=1 but it's for 2D so I tried adapting it. I first decomposed the calculation to solve the intersection point for XoZ plane and saved the x and z coordinates and then solving the intersection point for XoY plane and adding the y coordinate to a final xyz that I then transformed to clipspace and put a texture at those coordinates. But of course it doesn't work as it should or else I wouldn't have posted the question. From what I notice the after finding x in XoZ plane and the in XoY the x is not the same so something must be wrong. float a = ENG_Math.sqr(targetVelocity.x) + ENG_Math.sqr(targetVelocity.y) - ENG_Math.sqr(projectileSpeed); float b = 2.0f * (targetVelocity.x * targetPos.x + targetVelocity.y * targetPos.y); float c = ENG_Math.sqr(targetPos.x) + ENG_Math.sqr(targetPos.y); ENG_Math.solveQuadraticEquation(a, b, c, collisionTime); First time targetVelocity.y is actually targetVelocity.z (the same for targetPos) and the second time it's actually targetVelocity.y. The final position after XoZ is crossPosition.set(minTime * finalEntityVelocity.x + finalTargetPos4D.x, 0.0f, minTime * finalEntityVelocity.z + finalTargetPos4D.z); and after XoY crossPosition.y = minTime * finalEntityVelocity.y + finalTargetPos4D.y; Is my approach of separating into 2 planes and calculating any good? Or for 3D there is a whole different approach? sqr() is square not sqrt - avoiding a confusion.

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  • What is the value of an Enterprise Resource Planning (ERP) System?

    According to PWC.com ERP systems can add tremendous value to a company’s core business functionality.  Below PWC.com summarizes the primary value that an ERP can add to a company. ERPs are a collection business application that coordinates the resources, information, and activities required for core business processes. ERPs are strategic tools used to reduce costs, improve business processes, and healthier risk management.

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  • Cover Feature: "United Development"

    Developers need solutions, and there's no shortage of language and technology choices. Whether you're making development choices for applications that connect with legacy mainframe systems or new Web 2.0-enabled applications, standards and integration are key. Read about the standards-based tools and development solutions from Oracle that integrate your business processes.

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  • help configuring my samba file server

    - by user281745
    Hello everyone I have installed all the files I needed for my samba file server. I have also installed the gadmin-samba 0.3.2. I am trying to set a user-name and password also I would like to know how to ad my laptops I own to the machines allowed to connect to it. it can be in terminal but preferably in gadmin-samba which is like a GUI. please be very descriptive my systems is Ubuntu 14.04 and Gadmin-Samba 0.3.2

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