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• ArchBeat Link-o-Rama for 2012-07-11

  - by Bob Rhubart

  Is the future of retail showrooming? | GigaOm "The digital shopper isn’t just digital and she expects to be served seamlessly across all channels, physical and digital," reports GigaOm. Twenty years into the Internet era and the changes just keep coming. Solution architects take note... Agile Bureaucracy: When Practices become Principles | Jim Highsmith.com "Principles and values are a critical part of keeping individuals in organizations aligned and engaged," says Agile guru Jim Highsmith, "but the more pseudo-principles are piled on top of principles, the less and less organizations are able to adapt." Oracle Fusion Applications 11g Basics | Michel Schildmeijer "We are trying to build up a Oracle Fusion Apps environment on a Exalogic system, though still on bare metal, because officially there still is no Oracle VM available yet on Exalogic," says Michel Schildmeijer, an Oracle Fusion Middleware Architect at Qualogy. "It is a bit of a challenge, but getting to know the basics and which components the install, build and configure phase use, might bring you a step further on the way." Process Centric Banking: Loan Origination Solution | Manish Palaparthy This interesting, detailed post by Manish Palaparthy explains the process behind the execution of a proof-of-concept for a Fusion Middleware-based loan-origination solution for a bank. The solution incorporates Oracle BPM Suite, Webcenter, and ADF technolgies in a SOA infrastructure. How eBay and Facebook are Cleaning Up Data Centers | Amy Gallo - HBR The Cloud has needs! As reported by Amy Gallo in an article in the Harvard Business Review, "The electricity demand of data centers and the telecommunications network is rivaling that of most nations. If the cloud were itself a country, it would rank fifth in the world on energy demand behind the U.S., China, Russia, and Japan." Do WebLogic configuration from ANT | Edwin Biemond "With WebLogic WLST you can script the creation of all your Application DataSources or SOA Integration artifacts( like JMS etc)," says Oracle ACE Edwin Biemond. "This is necessary if your domain contains many WebLogic artifacts or you have more then one WebLogic environment. If so, you want to script this so you can configure a new WebLogic domain in minutes and you can repeat this task with always the same result." Oracle Special-Edition E-Book: Cloud Architecture for Dummies Learn how to architect and model your cloud implementation to drive efficiency and leverage economies of scale with Cloud Architecture for Dummies, a free Oracle e-book. (Registration required.) Thought for the Day "One of the best things to come out of the home computer revolution could be the general and widespread understanding of how severely limited logic really is." — Frank Herbert Source: SoftwareQuotes.com

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• GPU hung when switching graphic card

  - by Lie Ryan

  I have a laptop (Dell Inspiron N4110) with a switchable graphic. $ lspci | grep VGA 00:02.0 VGA compatible controller: Intel Corporation 2nd Generation Core Processor Family Integrated Graphics Controller (rev 09) 01:00.0 VGA compatible controller: ATI Technologies Inc NI Whistler [AMD Radeon HD 6600M Series] (rev ff) Normally, my laptop starts with both graphic cards enabled, which caused the laptop to turn very hot and the fan to become very noisy. I have been using a small script to disable the Radeon card. For some time, I'm quite happy with this arrangement. However, I have been having some issues with the Intel card (IGD), the Intel card often randomly hang when running OpenGL apps; and so I want to give the Radeon card (DIS) another chance. I have never been able to switch to the Radeon card, but recently, I found out that if I do a "delayed switching" (DDIS): # echo "DDIS" > /sys/kernel/debug/vgaswitcheroo/switch root@lieryan-dell-ubuntu:/sys/kernel/debug/vgaswitcheroo# cat switch 0:IGD:+:Pwr:0000:00:02.0 1:DIS: :Pwr:0000:01:00.0 then I logoff (i.e. to restart X), the screen switch to pseudo-tty and then it stuck there freezing. At this situation, mouse and keyboard stops working so I can't switch to another ptty. I tried ssh-ing from another computer to salvage logs (dmesg at that point) and whatnot; I found out that when freezing, the active graphic card is the AMD card: -- this is from ssh -- # cat switch 0:IGD: :Off:0000:00:02.0 1:DIS:+:Pwr:0000:01:00.0 but the GPU is apparently hung, looking at dmesg gives: ... [ 1411.649974] vga_switcheroo: client 0 refused switch [ 1411.649985] vga_switcheroo: setting delayed switch to client 1 [ 1423.911759] vga_switcheroo: processing delayed switch to 1 [ 1424.006564] fbcon: Remapping primary device, fb1, to tty 1-63 [ 1424.006799] i915: switched off [ 1424.840351] [drm:drm_mode_getfb] *ERROR* invalid framebuffer id [ 1425.718088] [drm:drm_mode_getfb] *ERROR* invalid framebuffer id [ 1426.622377] [drm:drm_mode_getfb] *ERROR* invalid framebuffer id [ 1427.355683] [drm:drm_mode_getfb] *ERROR* invalid framebuffer id [ 1428.193549] [drm:drm_mode_getfb] *ERROR* invalid framebuffer id ... the invalid framebuffer id error is repeated for many times over ... I were able to successfully recover by switching back to the Intel card and restarting X from ssh; indicating that only the Radeon card has problems switching. System info: $ uname -a Linux lieryan-dell-ubuntu 3.0.0-14-generic #23-Ubuntu SMP Mon Nov 21 20:28:43 UTC 2011 x86_64 x86_64 x86_64 GNU/Linux $ lsb_release -a No LSB modules are available. Distributor ID: Ubuntu Description: Ubuntu 11.10 Release: 11.10 Codename: oneiric The laptop also do not have the option to set graphic card at BIOS and the proprietary driver, fglrx, also have never worked; when I installed it through jockey ("Additional Drivers"), glxinfo showed that it still being rendered by Mesa, the /sys/kernel/debug/vgaswitcheroo directory has gone missing, and the driver crashes with a traceback if I use xorg.conf to tell X to use fglrx. Anyone had any idea if it is possible to use this AMD card either with the radeon or the fglrx driver? logs: dmesg

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• Drawing multiple objects from one Vertex Buffer Object in OpenGL/OpenTK

  - by stoney78us

  I am trying to experimenting drawing method using VBO in OpenGL. Many people normally use 1 vbo to store one object data array. I was trying to do something quite opposite which is storing multiple object data into 1 vbo then drawing it. There is story behind why i want to do this. I want to group many of objects as a single object sometime. However my code doesn't do the justice. Following is my pseudo code: //Data double[] vertices = {line strip 1, line strip 2, line strip 3}; //series of vertices int linestrip1offset = index of the first vertex in line strip 1; int linestrip2offset = index of the first vertex in line strip 2; int linestrip3offset = index of the first vertex in line strip 3; int linestrip1VertexNum = number of vertices in linestrip 1; int linestrip2VertexNum = number of vertices in linestrip 2; int linestrip3VertexNum = number of vertices in linestrip 3; //Setting Up void init() { int[] vBO = new int[1]; GL.GenBuffer(1, vBO); GL.BindBuffer(BufferTarget.ArrayBuffer, vBO[0]); GL.BufferData(BufferTarget.ArrayBuffer, new IntPtr(_vertices.Length * sizeof(double)), _vertices, BufferUsageHint.StaticDraw); GL.EnableClientState(Array.VertexArray); } //Drawing void draw() { GL.BindBuffer(BufferTarget.ArrayBuffer, vBO[0]); GL.EnableClientState(ArrayCap.VertexArray); GL.VertexPointer(3, VertexPointerType.Double, 0, linestrip1offset); //drawing first linestrip GL.DrawArrays(drawMode, linestrip1offset , linestrip1VertexNum ); GL.VertexPointer(3, VertexPointerType.Double, 0, linestrip2offset); //drawing second linestrip GL.DrawArrays(drawMode, linestrip2offset , linestrip2VertexNum ); GL.VertexPointer(3, VertexPointerType.Double, 0, linestrip3offset); //drawing third linestrip GL.DrawArrays(drawMode, linestrip3offset , linestrip3VertexNum ); GL.DisableClientState(ArrayCap.VertexArray); GL.BindBuffer(BufferTarget.ArrayBuffer, 0); } I don't know what i did wrong but i think technically it should work where we can tell OpenGL which part of the data in the vBO to be drawn.

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• Power Distribution amongst connected nodes

  - by Perky

  In my game the map is represented by connected nodes, each node has a number of connected nodes. The nodes represent a system in which players can build structures and move units about. If you're familiar with Sins of a Solar Empire the game map is very similar. I want each node to be able to produce power and share it with all connected nodes. For example if A, B, C & D are all connected and produce 100 power units, then each system should have 400 power units available. If node B builds a structure that consumes 100 power units then A, B, C & D should then have 300 power units available. I've been working on this system all day and haven't been able to get it working quite the way I want. My current implementation is to first recurse through each nodes's connected node adding up the power, I keep a list of closed nodes so it doesn't loop, it's quite similar to A* actually. Pseudo code: All nodes start with the properties node.power = 0 node.basePower = 100 // could be different for each node. node.initialPower = node.basePower - function propagatePower( node, initialPower, closedNodes ) node.power += initialPower add( closedNodes, node ) connectedNodes = connected_nodes_except_from( closedNodes ) foreach node in connectedNodes do propagatePower( node, initialPower, closedNodes ) end end After this I iterate through all power consumers. foreach consumer in consumers do node = consumer.parentNode if node.power >= consumer.powerConsumption then consumer.powerConsumed += consumer.powerConsumption node.producedPower -= consumer.powerConsumption end end Then I adjust the initial power for the next propagation cycle. foreach node in nodes do node.initialPower = node.basePower - node.producedPower node.displayPower = node.power // for rendering the power. node.power = 0 end This seemed to work at first but then I came into a problem. Say two nodes A & B produce 100Pu each, it's shared so both A & B have 200Pu. I then make two structures that consume 80Pu each on A (160Pu). Then the nodes power is adjusted to basePower - producedPower (100-160 = -60). Nodes are propagated, both nodes now have 40Pu (A: -60 + B: 100 = 40). Which is correct because they started with 200Pu - 160Pu = 40Pu. However now node.power >= consumer.powerConsumption is false. Whats worse is it's false for any structure that uses more that 40Pu, so the whole system goes down. I could deduct from consumer.powerConsumption but what do I do if power is reduced elsewhere? I don't have the correct data to perform the necessary checks. It's late so I'm probably not thinking straight but I thought to ask on here to see if anyone has any other implementations, better or worse I'd be interested to know.

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• In a state machine, is it a good idea to separate states and transitions?

  - by codablank1

  I have implemented a small state machine in this way (in pseudo code): class Input {} class KeyInput inherits Input { public : enum { Key_A, Key_B, ..., } } class GUIInput inherits Input { public : enum { Button_A, Button_B, ..., } } enum Event { NewGame, Quit, OpenOptions, OpenMenu } class BaseState { String name; Event get_event (Input input); void handle (Event e); //event handling function } class Menu inherits BaseState{...} class InGame inherits BaseState{...} class Options inherits BaseState{...} class StateMachine { public : BaseState get_current_state () { return current_state; } void add_state (String name, BaseState state) { statesMap.insert(name, state);} //raise an exception if state not found BaseState get_state (String name) { return statesMap.find(name); } //raise an exception if state or next_state not found void add_transition (Event event, String state_name, String next_state_name) { BaseState state = get_state(state_name); BaseState next_state = get_state(next_state_name); transitionsMap.insert(pair<event, state>, next_state); } //raise exception if couple not found BaseState get_next_state(Event event, BaseState state) { return transitionsMap.find(pair<event, state>); } void handle(Input input) { Event event = current_state.get_event(input) current_state.handle(event); current_state = get_next_state(event, current_state); } private : BaseState current_state; map<String, BaseState> statesMap; //map of all states in the machine //for each couple event/state, this map stores the next state map<pair<Event, BaseState>, BaseState> transitionsMap; } So, before getting the transition, I need to convert the key input or GUI input to the proper event, given the current state; thus the same key 'W' can launch a new game in the 'Menu' state or moving forward a character in the 'InGame' state; Then I get the next state from the transitionsMap and I update the current state Does this configuration seem valid to you ? Is it a good idea to separate states and transitions ? And I have some kind of trouble to represent a 'null state' or a 'null event'; What initial value can I give to the current state and which one should be returned by get_state if it fails ?

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• Understanding how OpenGL blending works

  - by yuumei

  I am attempting to understand how OpenGL (ES) blending works. I am finding it difficult to understand the documentation and how the results of glBlendFunc and glBlendEquation effect the final pixel that is written. Do the source and destination out of glBlendFunc get added together with GL_FUNC_ADD by default? This seems wrong because "basic" blending of GL_ONE, GL_ONE would output 2,2,2,2 then (Source giving 1,1,1,1 and dest giving 1,1,1,1). I have written the following pseudo-code, what have I got wrong? struct colour { float r, g, b, a; }; colour blend_factor( GLenum factor, colour source, colour destination, colour blend_colour ) { colour colour_factor; float i = min( source.a, 1 - destination.a ); // From http://www.khronos.org/opengles/sdk/docs/man/xhtml/glBlendFunc.xml switch( factor ) { case GL_ZERO: colour_factor = { 0, 0, 0, 0 }; break; case GL_ONE: colour_factor = { 1, 1, 1, 1 }; break; case GL_SRC_COLOR: colour_factor = source; break; case GL_ONE_MINUS_SRC_COLOR: colour_factor = { 1 - source.r, 1 - source.g, 1 - source.b, 1 - source.a }; break; // ... } return colour_factor; } colour blend( colour & source, colour destination, GLenum source_factor, // from glBlendFunc GLenum destination_factor, // from glBlendFunc colour blend_colour, // from glBlendColor GLenum blend_equation // from glBlendEquation ) { colour source_colour = blend_factor( source_factor, source, destination, blend_colour ); colour destination_colour = blend_factor( destination_factor, source, destination, blend_colour ); colour output; // From http://www.khronos.org/opengles/sdk/docs/man/xhtml/glBlendEquation.xml switch( blend_equation ) { case GL_FUNC_ADD: output = add( source_colour, destination_colour ); case GL_FUNC_SUBTRACT: output = sub( source_colour, destination_colour ); case GL_FUNC_REVERSE_SUBTRACT: output = sub( destination_colour, source_colour ); } return output; } void do_pixel() { colour final_colour; // Blending if( enable_blending ) { final_colour = blend( current_colour_output, framebuffer[ pixel ], ... ); } else { final_colour = current_colour_output; } } Thanks!

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• How do we provide valid time estimates during Sprint Planning without doing "too much" design?

  - by Michael Edenfield

  My team is getting up to speed with Scrum, but most of us are more familiar with non-agile or "pseudo-"agile methodologies. The part that is the biggest hurdle for us is running an efficient Sprint Planning meeting where we break our backlog items into tasks, and estimate hours. (I'm using the terminology from the VS2010 Scrum Template; apologies if I use the wrong word somewhere.) When we try to figure out how long a task is going to take, we often fall into the trap of designing the feature at the code level -- table layout, interfaces, etc -- in order to figure out how long that's going to take. I'm pretty sure this is not the appropriate place to be doing that kind of design. We should be scheduling tasks for these design meetings during the sprint. However, we are having trouble figuring out how else to come up with meaningful estimates for the tasks. Are there any practical habits/techniques/etc. for making a judgement call about how long a feature is going to take, without knowing how you plan to implement it? If our time estimates are going to change significantly once the design has been completed, how can we properly budget our Sprint backlog ahead of time? EDIT: Just to clarify, since some of the comments/answers are very valid but I think addressing the wrong question. We know that what we're doing is not right, and that we should be building time into the sprint for this design. Conceptually all of the developers understand that. We also also bringing in a team member with Scrum experience to keep us on track if we start going off into the weeds. The problem is that, without going through this design process, we are finding it difficult to provide concrete time estimates for anything. We are constantly saying things like "well if we design it this way it might take 8 hours but if we end up having to do this other way instead that will take about 32 but it might not be as bad once we start trying to write it...". I also assume that this process will get better once we have some historical velocity to work from, but many of the technologies and architectural patterns we are using are new to us. But if potentially-wildly-wrong estimates are just a natural part of adapting this process then we will just need to recondition ourselves to accept that :)

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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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• Why do old programming languages continue to be revised?

  - by SunAvatar

  This question is not, "Why do people still use old programming languages?" I understand that quite well. In fact the two programming languages I know best are C and Scheme, both of which date back to the 70s. Recently I was reading about the changes in C99 and C11 versus C89 (which seems to still be the most-used version of C in practice and the version I learned from K&R). Looking around, it seems like every programming language in heavy use gets a new specification at least once per decade or so. Even Fortran is still getting new revisions, despite the fact that most people using it are still using FORTRAN 77. Contrast this with the approach of, say, the typesetting system TeX. In 1989, with the release of TeX 3.0, Donald Knuth declared that TeX was feature-complete and future releases would contain only bug fixes. Even beyond this, he has stated that upon his death, "all remaining bugs will become features" and absolutely no further updates will be made. Others are free to fork TeX and have done so, but the resulting systems are renamed to indicate that they are different from the official TeX. This is not because Knuth thinks TeX is perfect, but because he understands the value of a stable, predictable system that will do the same thing in fifty years that it does now. Why do most programming language designers not follow the same principle? Of course, when a language is relatively new, it makes sense that it will go through a period of rapid change before settling down. And no one can really object to minor changes that don't do much more than codify existing pseudo-standards or correct unintended readings. But when a language still seems to need improvement after ten or twenty years, why not just fork it or start over, rather than try to change what is already in use? If some people really want to do object-oriented programming in Fortran, why not create "Objective Fortran" for that purpose, and leave Fortran itself alone? I suppose one could say that, regardless of future revisions, C89 is already a standard and nothing stops people from continuing to use it. This is sort of true, but connotations do have consequences. GCC will, in pedantic mode, warn about syntax that is either deprecated or has a subtly different meaning in C99, which means C89 programmers can't just totally ignore the new standard. So there must be some benefit in C99 that is sufficient to impose this overhead on everyone who uses the language. This is a real question, not an invitation to argue. Obviously I do have an opinion on this, but at the moment I'm just trying to understand why this isn't just how things are done already. I suppose the question is: What are the (real or perceived) advantages of updating a language standard, as opposed to creating a new language based on the old?

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• Rending 2D Tile World (With Player In The Middle)

  - by Mick

  What I have at the moment is a series of data structures I'm using, and I would like to render the world onto the screen (just the visible parts). I've actually already done this several times (lots of rewrites), but it's a bit buggy (rounding seems to make the screen jump ever so slightly every x tiles the player walks past). Basically I've been confusing myself heavily on what I feel should be a pretty simple problem... so here I am asking for some help! OK! So I have a 50x50 array holding the tiles of the world. I have the player position as 2 floats, x ([0, 49]) and y ([0, 49]) in that array. I have the application size exactly in pixels (x and y). I have an arbitrary TILE_SIZE static int (based on screen pixels). What I think is heavily confusing me is using a 2d orthogonal projection in opengl which maps (0,0) to the top left of the screen and (SCREEN_SIZE_X, SCREEN_SIZE_Y) to the bottom right of the screen. gl.glMatrixMode(GL.GL_PROJECTION); gl.glLoadIdentity(); glu.gluOrtho2D(0, getActualWidth(), getActualHeight(), 0); gl.glMatrixMode(GL.GL_MODELVIEW); gl.glLoadIdentity(); The map tiles are set so that the (0,0) in the array is the bottom left. And the player has to be in the middle on the screen (SCREEN_SIZE_X/2, SCREEN_SIZE_Y/2). What I've been doing so far is trying to render 1-2 tiles more all around what would be displayed on the screen so that I don't have to worry about figuring out rendering half a tile from the top left, depending where the player is. It seems like such an easy problem but after spending about 40+hours on it rewriting it many times I think I'm at a point where I just can't think clearly anymore... Any help would be appreciated. It would be great if someone can provide some very basic pseudo code on keeping the player in the middle when your projection is mapped to screen coordinates and only rendering basically the tiles that you would be any be see. Thanks!

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• Checking timeouts made more readable

  - by Markus

  I have several situations where I need to control timeouts in a technical application. Either in a loop or as a simple check. Of course – handling this is really easy, but none of these is looking cute. To clarify, here is some C# (Pseudo) code: private DateTime girlWentIntoBathroom; girlWentIntoBathroom = DateTime.Now; do { // do something } while (girlWentIntoBathroom.AddSeconds(10) > DateTime.Now); or if (girlWentIntoBathroom.AddSeconds(10) > DateTime.Now) MessageBox.Show("Wait a little longer"); else MessageBox.Show("Knock louder"); Now I was inspired by something a saw in Ruby on StackOverflow: Now I’m wondering if this construct can be made more readable using extension methods. My goal is something that can be read like “If girlWentIntoBathroom is more than 10 seconds ago” 1st attempt if (girlWentIntoBathroom > (10).Seconds().Ago()) MessageBox.Show("Wait a little longer"); else MessageBox.Show("Knock louder"); So I wrote an extension for integer that converts the integer into a TimeSpan public static TimeSpan Seconds(this int amount) { return new TimeSpan(0, 0, amount); } After that, I wrote an extension for TimeSpan like this: public static DateTime Ago(this TimeSpan diff) { return DateTime.Now.Add(-diff); } This works fine so far, but has a great disadvantage. The logic is inverted! Since girlWentIntoBathroom is a timestamp in the past, the right side of the equation needs to count backwards: impossible. Just inverting the equation is no solution, because it will invert the read sentence as well. 2nd attempt So I tried something new: if (girlWentIntoBathroom.IsMoreThan(10).SecondsAgo()) MessageBox.Show("Knock louder"); else MessageBox.Show("Wait a little longer"); IsMoreThan() needs to transport the past timestamp as well as the span for the extension SecondsAgo(). It could be: public static DateWithIntegerSpan IsMoreThan(this DateTime baseTime, int span) { return new DateWithIntegerSpan() { Date = baseTime, Span = span }; } Where DateWithIntegerSpan is simply: public class DateWithIntegerSpan { public DateTime Date {get; set;} public int Span { get; set; } } And SecondsAgo() is public static bool SecondsAgo(this DateWithIntegerSpan dateAndSpan) { return dateAndSpan.Date.Add(new TimeSpan(0, 0, dateAndSpan.Span)) < DateTime.Now; } Using this approach, the English sentence matches the expected behavior. But the disadvantage is, that I need a helping class (DateWithIntegerSpan). Has anyone an idea to make checking timeouts look more cute and closer to a readable sentence? Am I a little too insane thinking about something minor like this?

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• Tiling Problem Solutions for Various Size "Dominoes"

  - by user67081

  I've got an interesting tiling problem, I have a large square image (size 128k so 131072 squares) with dimensons 256x512... I want to fill this image with certain grain types (a 1x1 tile, a 1x2 strip, a 2x1 strip, and 2x2 square) and have no overlap, no holes, and no extension past the image boundary. Given some probability for each of these grain types, a list of the number required to be placed is generated for each. Obviously an iterative/brute force method doesn't work well here if we just randomly place the pieces, instead a certain algorithm is required. 1) all 2x2 square grains are randomly placed until exhaustion. 2) 1x2 and 2x1 grains are randomly placed alternatively until exhaustion 3) the remaining 1x1 tiles are placed to fill in all holes. It turns out this algorithm works pretty well for some cases and has no problem filling the entire image, however as you might guess, increasing the probability (and thus number) of 1x2 and 2x1 grains eventually causes the placement to stall (since there are too many holes created by the strips and not all them can be placed). My approach to this solution has been as follows: 1) Create a mini-image of size 8x8 or 16x16. 2) Fill this image randomly and following the algorithm specified above so that the desired probability of the entire image is realized in the mini-image. 3) Create N of these mini-images and then randomly successively place them in the large image. Unfortunately there are some downfalls to this simplification. 1) given the small size of the mini-images, nailing an exact probability for the entire image is not possible. Example if I want p(2x1)=P(1x2)=0.4, the mini image may only give 0.41 as the closes probability. 2) The mini-images create a pseudo boundary where no overlaps occur which isn't really descriptive of the model this is being used for. 3) There is only a fixed number of mini-images so i'm not sure how random this really is. I'm really just looking to brainstorm about possible solutions to this. My main concern is really to nail down closer probabilities, now one might suggest I just increase the mini-image size. Well I have, and it turns out that in certain cases(p(1x2)=p(2x1)=0.5) the mini-image 16x16 isn't even iteratively solvable.. So it's pretty obvious how difficult it is to randomly solve this for anything greater than 8x8 sizes.. So I'd love to hear some ideas. Thanks

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• Reasons NOT to use JSF [closed]

  - by Vain Fellowman

  I am new to StackExchange, but I figured you would be able to help me. We're crating a new Java Enterprise application, replacing an legacy JSP solution. Due to many many changes, the UI and parts of the business logic will completely be rethought and reimplemented. Our first thought was JSF, as it is the standard in Java EE. At first I had a good impression. But now I am trying to implement a functional prototype, and have some really serious concerns about using it. First of all, it creates the worst, most cluttered invalid pseudo-HTML/CSS/JS mix I've ever seen. It violates every single rule I learned in web-development. Furthermore it throws together, what never should be so tightly coupled: Layout, Design, Logic and Communication with the server. I don't see how I would be able to extend this output comfortably, whether styling with CSS, adding UI candy (like configurable hot-keys, drag-and-drop widgets) or whatever. Secondly, it is way too complicated. Its complexity is outstanding. If you ask me, it's a poor abstraction of basic web technologies, crippled and useless in the end. What benefits do I have? None, if you think about. Hundreds of components? I see ten-thousands of HTML/CSS snippets, ten-thousands of JavaScript snippets and thousands of jQuery plug-ins in addition. It solves really many problems - we wouldn't have if we wouldn't use JSF. Or the front-controller pattern at all. And Lastly, I think we will have to start over in, say 2 years. I don't see how I can implement all of our first GUI mock-up (Besides; we have no JSF Expert in our team). Maybe we could hack it together somehow. And then there will be more. I'm sure we could hack our hack. But at some point, we'll be stuck. Due to everything above the service tier is in control of JSF. And we will have to start over. My suggestion would be to implement a REST api, using JAX-RS. Then create a HTML5/Javascript client with client side MVC. (or some flavor of MVC..) By the way; we will need the REST api anyway, as we are developing a partial Android front-end, too. I doubt, that JSF is the best solution nowadays. As the Internet is evolving, I really don't see why we should use this 'rake'. Now, what are pros/cons? How can I emphasize my point to not use JSF? What are strong points to use JSF over my suggestion?

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• How to remotely open gedit with SFTP URL in Gnome through SSH?

  - by Álvaro Justen

  My setup is weird and I can't change it now. I have two machines: local-machine: it's my desktop running Ubuntu with Gnome remote-machine: it's one virtual machine, also running Ubuntu but without X In both machines I have my private and public SSH keys. I need to run SSH from remote-machine to local-machine and run gedit (in local-machine, under the default $DISPLAY) but openning a file in remote-machine throught SFTP. Something like this: myuser@remote-machine:~$ ssh local-machine "DISPLAY=:0.0 gedit sftp://remote-machine/some/file" The command above doesn't work. gedit shows this message: Could not open the file sftp://remote-machine/some/file. gedit cannot handle sftp: locations. Note that: /some/file exists on remote-machine. I can SSH normally from remote-machine to local-machine using my SSH key without any problems! I can run the command DISPLAY=:0.0 gedit sftp://remote-machine/some/file in a terminal on local-machine and gedit opens the file on remote-machine without any problems - but the terminal in which I executed the command is running in DISPLAY :0 (really, it's gnome-terminal). I also tried -t option of SSH client (to force pseudo-tty allocation) but it didn't work. If I try to run DISPLAY=:0.0 gedit sftp://remote-machine/some/file in local-machine but under a tty (for example in tty1, by pressing <Ctrl>+<Alt>+<F1>) it doesn't not work - I get the same error when running from remote-machine. I found that if I pass the environment variable DBUS_SESSION_BUS_ADDRESS with a correct value, it works! So, if I do something like that: myuser@local-machine:~$ env | grep DBUS_SESSION_BUS_ADDRESS > env.txt myuser@local-machine:~$ scp env.txt remote-machine: and then: myuser@remote-machine:~$ ssh local-machine "DISPLAY=:0.0 $(cat env.txt) gedit sftp://remote-machine/some/file" it works! The problem is that I'm not on local-machine so I can't get the correct value for this env variable. Is there any other way to make this work?

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• When I restart my virtual enviorment it does not re-bind to the IP address

  - by RoboTamer

  The IP does no longer respond to a remote ping With restart I mean: lxc-stop -n vm3 lxc-start -n vm3 -f /etc/lxc/vm3.conf -d -- /etc/network/interfaces auto lo iface lo inet loopback up route add -net 127.0.0.0 netmask 255.0.0.0 dev lo down route add -net 127.0.0.0 netmask 255.0.0.0 dev lo # device: eth0 auto eth0 iface eth0 inet manual auto br0 iface br0 inet static address 192.22.189.58 netmask 255.255.255.248 gateway 192.22.189.57 broadcast 192.22.189.63 bridge_ports eth0 bridge_fd 0 bridge_hello 2 bridge_maxage 12 bridge_stp off post-up ip route add 192.22.189.59 dev br0 post-up ip route add 192.22.189.60 dev br0 post-up ip route add 192.22.189.61 dev br0 post-up ip route add 192.22.189.62 dev br0 -- /etc/lxc/vm3.conf lxc.utsname = vm3 lxc.rootfs = /var/lib/lxc/vm3/rootfs lxc.tty = 4 #lxc.pts = 1024 # pseudo tty instance for strict isolation lxc.network.type = veth lxc.network.flags = up lxc.network.link = br0 lxc.network.name = eth0 lxc.network.mtu = 1500 #lxc.cgroup.cpuset.cpus = 0 # security parameter lxc.cgroup.devices.deny = a # Deny all access to devices lxc.cgroup.devices.allow = c 1:3 rwm # dev/null lxc.cgroup.devices.allow = c 1:5 rwm # dev/zero lxc.cgroup.devices.allow = c 5:1 rwm # dev/console lxc.cgroup.devices.allow = c 5:0 rwm # dev/tty lxc.cgroup.devices.allow = c 4:0 rwm # dev/tty0 lxc.cgroup.devices.allow = c 4:1 rwm # dev/tty1 lxc.cgroup.devices.allow = c 4:2 rwm # dev/tty2 lxc.cgroup.devices.allow = c 1:9 rwm # dev/urandon lxc.cgroup.devices.allow = c 1:8 rwm # dev/random lxc.cgroup.devices.allow = c 136:* rwm # dev/pts/* lxc.cgroup.devices.allow = c 5:2 rwm # dev/pts/ptmx lxc.cgroup.devices.allow = c 254:0 rwm # rtc # mounts point lxc.mount.entry=proc /var/lib/lxc/vm3/rootfs/proc proc nodev,noexec,nosuid 0 0 lxc.mount.entry=devpts /var/lib/lxc/vm3/rootfs/dev/pts devpts defaults 0 0 lxc.mount.entry=sysfs /var/lib/lxc/vm3/rootfs/sys sysfs defaults 0 0

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• Fedora, ssh and sudo

  - by Ricky Robinson

  I have to run a script remotely on several Fedora machines through ssh. Since the script requires root priviliges, I do: $ ssh me@remost_host "sudo touch test_sudo" #just a simple example sudo: no tty present and no askpass program specified The remote machines are configured in such a way that the password for sudo is never asked for. For the above error, the most common fix is to allocate a pseudo-terminal with the -t option in ssh: $ ssh -t me@remost_host "sudo touch test_sudo" sudo: no tty present and no askpass program specified Let's try to force this allocation with -t -t: $ ssh -t -t me@remost_host "sudo touch test_sudo" sudo: no tty present and no askpass program specified Nope, it doesn't work. In /etc/sudoers of course I have this line: #Defaults requiretty ... but I can't manually change it on tens of remote machines. Am I missing something here? Is there an easy fix? EDIT: Here is the sudoers file of a host where ssh me@host "sudo stat ." works. Here is the sudoers file of a host where it doesn't work. EDIT 2: Running tty on a host where it works: $ ssh me@host_ok tty not a tty $ ssh -t me@host_ok tty /dev/pts/12 Connection to host_ok closed. $ ssh -t -t me@host_ok tty /dev/pts/12 Connection to host_ok closed. Now on a host where it doesn't work: $ ssh me@host_ko tty not a tty $ ssh -t me@host_ko tty not a tty Connection to host_ko closed. $ ssh -t -t me@host_ko tty not a tty Connection to host_ko closed.

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• GRE Tunnel over IPsec with Loopback

  - by Alek

  I'm having a really hard time trying to estabilish a VPN connection using a GRE over IPsec tunnel. The problem is that it involves some sort of "loopback" connection which I don't understand -- let alone be able to configure --, and the only help I could find is related to configuring Cisco routers. My network is composed of a router and a single host running Debian Linux. My task is to create a GRE tunnel over an IPsec infrastructure, which is particularly intended to route multicast traffic between my network, which I am allowed to configure, and a remote network, for which I only bear a form containing some setup information (IP addresses and phase information for IPsec). For now it suffices to estabilish a communication between this single host and the remote network, but in the future it will be desirable for the traffic to be routed to other machines on my network. As I said this GRE tunnel involves a "loopback" connection which I have no idea of how to configure. From my previous understanding, a loopback connection is simply a local pseudo-device used mostly for testing purposes, but in this context it might be something more specific that I do not have the knowledge of. I have managed to properly estabilish the IPsec communication using racoon and ipsec-tools, and I believe I'm familiar with the creation of tunnels and addition of addresses to interfaces using ip, so the focus is on the GRE step. The worst part is that the remote peers do not respond to ping requests and the debugging of the general setup is very difficult due to the encrypted nature of the traffic. There are two pairs of IP addresses involved: one pair for the GRE tunnel peer-to-peer connection and one pair for the "loopback" part. There is also an IP range involved, which is supposed to be the final IP addresses for the hosts inside the VPN. My question is: how (or if) can this setup be done? Do I need some special software or another daemon, or does the Linux kernel handle every aspect of the GRE/IPsec tunneling? Please inform me if any extra information could be useful. Any help is greatly appreciated.

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• mod_rewrite "Request exceeded the limit of 10 internal redirects due to probable configuration error."

  - by Shoaibi

  What i want: Force www [works] Restrict access to .inc.php [works] Force redirection of abc.php to /abc/ Removal of extension from url Add a trailing slash if needed old .htaccess : Options +FollowSymLinks <IfModule mod_rewrite.c> RewriteEngine On RewriteBase / ### Force www RewriteCond %{HTTP_HOST} ^example\.net$ RewriteRule ^(.*)$ http://www\.example\.net/$1 [L,R=301] ### Restrict access RewriteCond %{REQUEST_URI} ^/(.*)\.inc\.php$ [NC] RewriteRule .* - [F,L] #### Remove extension: RewriteRule ^(.*)/$ /$1.php [L,R=301] ######### Trailing slash: RewriteCond %{REQUEST_FILENAME} !-f RewriteCond %{REQUEST_URI} !(.*)/$ RewriteRule ^(.*)$ http://www.example.net/$1/ [R=301,L] </IfModule> New .htaccess: Options +FollowSymLinks <IfModule mod_rewrite.c> RewriteEngine On RewriteBase / ### Force www RewriteCond %{HTTP_HOST} ^example\.net$ RewriteRule ^(.*)$ http://www\.example\.net/$1 [L,R=301] ### Restrict access RewriteCond %{REQUEST_URI} ^/(.*)\.inc\.php$ [NC] RewriteRule .* - [F,L] #### Remove extension: RewriteCond %{REQUEST_FILENAME} \.php$ RewriteCond %{REQUEST_FILENAME} -f RewriteRule (.*)\.php$ /$1/ [L,R=301] #### Map pseudo-directory to PHP file RewriteCond %{REQUEST_FILENAME}\.php -f RewriteRule (.*) /$1.php [L] ######### Trailing slash: RewriteCond %{REQUEST_FILENAME} -d RewriteCond %{REQUEST_FILENAME} !/$ RewriteRule (.*) $1/ [L,R=301] </IfModule> errorlog: Request exceeded the limit of 10 internal redirects due to probable configuration error. Use 'LimitInternalRecursion' to increase the limit if necessary. Use 'LogLevel debug' to get a backtrace., referer: http://www.example.net/ Rewrite.log: http://pastebin.com/x5PKeJHB

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• No signal on monitor after plug it to a linux box

  - by yaroot

  I use my old computer as an NAS, so I remove the monitor after I installed linux on it (disconnect vga cable). I use ssh to control the machine and it works fine. Until some day, after kernel/softare upgrade or messing up some configs, I cannot connect to it through ssh, then I have to plug the monitor back, but the monitor says "No input signal". So I have to restart the computer WITH the monitor connected, and the monitor's back! I think the computer/linux kernel doesn't detect the monitor plug-in event. So how can I start my linux box without a monitor, but when it goes wrong I can still plug my monitor (vga) back and use the console. Edit: just one pci-e video card, has dvi, vga, tv/out (s-video) Edit2: Xorg is not running. I just need the console (CTRL+ALT+F1). The problem is, if the machine booted without a monitor connected, it won't give me a pseudo terminal after I attach the vga cable while it's running. Clearly the monitor is not auto detected as usb device. I'm wondering how to let the monitor auto detected.

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• Using AT on Ubuntu to Background Downloads (w/ Queue)

  - by Nicholas Yost

  I am writing a PHP script, but I want to use the AT command in Ubuntu to fetch a remote file via WGET. I'm basically looking to background the process, so PHP can finish fairly quickly. I cannot find any questions on here about how to use both, but I basically want to do the following pseudo-code: <?php exec('at now -q queuename wget http://path.to/remote/file.ext'); ?> Additionally, I'd like to queue this between providers. I'd like to have each path.to have its own queue, so I only download one file from each provider at a time. Meaning: <?php exec('at now -q remote wget http://path.to/remote/file.ext /local/path'); exec('at now -q vendorone wget http://vendor.one/remote/file.ext /local/path'); exec('at now -q vendortwo wget http://vendor.two/remote/file.ext /local/path'); exec('at now -q vendorone wget http://vendor.one/remote/file.ext /local/path'); ?> This should download the files from path.to, vendor.one, vendor.two immediately, and when the first file is finished downloading from vendor.one, it starts the second file. Does that make sense? I can't find anything like this anywhere on the web, much less on SO/SF. If we can use the crontab to run a one-off wget command, thats fine too.

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• How flexible is the 'indirect' function?

  - by Chuck

  My curiosity pushes me to ask this question. If I were to have a series of functions that referenced a different column in a worksheet but all ended on the same row of data is there a way to point the 'row' part of a cell reference to a blank cell and use it has a variable to show the results of the functions up to a desired row simultaneously? Example: =Average('worksheet 1'.$A$1:'worksheet 1'.$A100) =Max('worksheet 1'.$B$1:'worksheet 1'.$B100) =Min('worksheet 1'.$C$1:'worksheet 1'.$C100) =Sum('worksheet 1'.$D$1:'worksheet 1'.$D100) Pseudo formulas... =Average('worksheet 1'.$A$1:'worksheet 1'.$A*('worksheet 2'.$A$1)*) =Max('worksheet 1'.$B$1:'worksheet 1'.$B*('worksheet 2'.$A$1)*) =Min('worksheet 1'.$C$1:'worksheet 1'.$C*('worksheet 2'.$A$1)*) =Sum('worksheet 1'.$D$1:'worksheet 1'.$D*('worksheet 2'.$A$1)*) Where 'worksheet 2'.$A$1 would only contain a number corresponding to a row in 'worksheet 1'. After stumbling upon and playing with the indirect() function I have only been able to replace the entire cell reference (Column and Row) with any success. The formula so far =SUM('worksheet 1'.C3:INDIRECT(A1)) Where A1 is on 'worksheet 2' and contains a full cell reference pointing to 'worksheet 1'. Any pointers?

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• GRE Tunnel over IPsec with Loopback

  - by Alek

  Hello, I'm having a really hard time trying to estabilish a VPN connection using a GRE over IPsec tunnel. The problem is that it involves some sort of "loopback" connection which I don't understand -- let alone be able to configure --, and the only help I could find is related to configuring Cisco routers. My network is composed of a router and a single host running Debian Linux. My task is to create a GRE tunnel over an IPsec infrastructure, which is particularly intended to route multicast traffic between my network, which I am allowed to configure, and a remote network, for which I only bear a form containing some setup information (IP addresses and phase information for IPsec). For now it suffices to estabilish a communication between this single host and the remote network, but in the future it will be desirable for the traffic to be routed to other machines on my network. As I said this GRE tunnel involves a "loopback" connection which I have no idea of how to configure. From my previous understanding, a loopback connection is simply a local pseudo-device used mostly for testing purposes, but in this context it might be something more specific that I do not have the knowledge of. I have managed to properly estabilish the IPsec communication using racoon and ipsec-tools, and I believe I'm familiar with the creation of tunnels and addition of addresses to interfaces using ip, so the focus is on the GRE step. The worst part is that the remote peers do not respond to ping requests and the debugging of the general setup is very difficult due to the encrypted nature of the traffic. There are two pairs of IP addresses involved: one pair for the GRE tunnel peer-to-peer connection and one pair for the "loopback" part. There is also an IP range involved, which is supposed to be the final IP addresses for the hosts inside the VPN. My question is: how (or if) can this setup be done? Do I need some special software or another daemon, or does the Linux kernel handle every aspect of the GRE/IPsec tunneling? Please inform me if any extra information could be useful. Any help is greatly appreciated.

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• What does this mean: "SATP VMW_SATP_LOCAL does not support device configuration"?

  - by Jason Tan

  Can anyone tell me what this means in ESXi 5.1?: SATP VMW_SATP_LOCAL does not support device configuration I've googled it and I get a lot of results, but as yet all the pages that contain the string are discussing other matters. The storage array is a HDS HUS-VM and the hosts are HP b460c G8 blades with flex fabric and flex fabric VCs which I am in the process of commissioning and would like to get it started on the right foot - i.e. error and warning free! naa.600508b1001c56ee3d70da65f071da23 Device Display Name: HP Serial Attached SCSI Disk (naa.600508b1001c56ee3d70da65f071da23) Storage Array Type: VMW_SATP_LOCAL Storage Array Type Device Config: SATP VMW_SATP_LOCAL does not support device configuration. Path Selection Policy: VMW_PSP_FIXED Path Selection Policy Device Config: {preferred=vmhba0:C0:T0:L1;current=vmhba0:C0:T0:L1} Path Selection Policy Device Custom Config: Working Paths: vmhba0:C0:T0:L1 Is Local SAS Device: true Is Boot USB Device: false This is the same LUN: ~ # esxcli storage core device list -d naa.60060e80132757005020275700000016 naa.60060e80132757005020275700000016 Display Name: HITACHI Fibre Channel Disk (naa.60060e80132757005020275700000016) Has Settable Display Name: true Size: 204800 Device Type: Direct-Access Multipath Plugin: NMP Devfs Path: /vmfs/devices/disks/naa.60060e80132757005020275700000016 Vendor: HITACHI Model: OPEN-V Revision: 5001 SCSI Level: 2 Is Pseudo: false Status: degraded Is RDM Capable: true Is Local: false Is Removable: false Is SSD: false Is Offline: false Is Perennially Reserved: false Queue Full Sample Size: 0 Queue Full Threshold: 0 Thin Provisioning Status: unknown Attached Filters: VAAI_FILTER VAAI Status: supported Other UIDs: vml.020001000060060e801327570050202757000000164f50454e2d56 Is Local SAS Device: false Is Boot USB Device: false ~ #

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• When I restart my LXC environment, the container does not re-bind to the IP address

  - by RoboTamer

  The IP does no longer respond to a remote ping With restart I mean: lxc-stop -n vm3 lxc-start -n vm3 -f /etc/lxc/vm3.conf -d -- /etc/network/interfaces auto lo iface lo inet loopback up route add -net 127.0.0.0 netmask 255.0.0.0 dev lo down route add -net 127.0.0.0 netmask 255.0.0.0 dev lo # device: eth0 auto eth0 iface eth0 inet manual auto br0 iface br0 inet static address 192.22.189.58 netmask 255.255.255.248 gateway 192.22.189.57 broadcast 192.22.189.63 bridge_ports eth0 bridge_fd 0 bridge_hello 2 bridge_maxage 12 bridge_stp off post-up ip route add 192.22.189.59 dev br0 post-up ip route add 192.22.189.60 dev br0 post-up ip route add 192.22.189.61 dev br0 post-up ip route add 192.22.189.62 dev br0 -- /etc/lxc/vm3.conf lxc.utsname = vm3 lxc.rootfs = /var/lib/lxc/vm3/rootfs lxc.tty = 4 #lxc.pts = 1024 # pseudo tty instance for strict isolation lxc.network.type = veth lxc.network.flags = up lxc.network.link = br0 lxc.network.name = eth0 lxc.network.mtu = 1500 #lxc.cgroup.cpuset.cpus = 0 # security parameter lxc.cgroup.devices.deny = a # Deny all access to devices lxc.cgroup.devices.allow = c 1:3 rwm # dev/null lxc.cgroup.devices.allow = c 1:5 rwm # dev/zero lxc.cgroup.devices.allow = c 5:1 rwm # dev/console lxc.cgroup.devices.allow = c 5:0 rwm # dev/tty lxc.cgroup.devices.allow = c 4:0 rwm # dev/tty0 lxc.cgroup.devices.allow = c 4:1 rwm # dev/tty1 lxc.cgroup.devices.allow = c 4:2 rwm # dev/tty2 lxc.cgroup.devices.allow = c 1:9 rwm # dev/urandon lxc.cgroup.devices.allow = c 1:8 rwm # dev/random lxc.cgroup.devices.allow = c 136:* rwm # dev/pts/* lxc.cgroup.devices.allow = c 5:2 rwm # dev/pts/ptmx lxc.cgroup.devices.allow = c 254:0 rwm # rtc # mounts point lxc.mount.entry=proc /var/lib/lxc/vm3/rootfs/proc proc nodev,noexec,nosuid 0 0 lxc.mount.entry=devpts /var/lib/lxc/vm3/rootfs/dev/pts devpts defaults 0 0 lxc.mount.entry=sysfs /var/lib/lxc/vm3/rootfs/sys sysfs defaults 0 0

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• Improving TCP performance over a gigabit network lots of connections and high traffic for storage and streaming services

  - by Linux Guy

  I have two servers, Both servers hardware Specification are Processor : Dual Processor RAM : over 128 G.B Hard disk : SSD Hard disk Outging Traffic bandwidth : 3 Gbps network cards speed : 10 Gbps Server A : for Encoding videos Server B : for storage videos andstream videos over web interface like youtube The inbound bandwidth between two servers is 10Gbps , the outbound bandwidth internet bandwidth is 500Mpbs Both servers using public ip addresses in public and private network Both servers transfer and connection on nginx port , and the server B used for streaming media , like youtube stream videos Both servers in same network , when i do ping from Server A to Server B i got high time latency above 1.0ms , the time range time=52.7 ms to time=215.7 ms - This is the output of iftop utility 353Mb 707Mb 1.04Gb 1.38Gb 1.73Gb mqqqqqqqqqqqqqqqqqqqqqqqqqqqvqqqqqqqqqqqqqqqqqqqqqqqqqqqvqqqqqqqqqqqqqqqqqqqqqqqqqqqvqqqqqqqqqqqqqqqqqqqqqqqqqqqvqqqqqqqqqqqqqqqqqqqqqqqqqqq server.example.com => ip.address 6.36Mb 4.31Mb 1.66Mb <= 158Kb 94.8Kb 35.1Kb server.example.com => ip.address 1.23Mb 4.28Mb 1.12Mb <= 17.1Kb 83.5Kb 21.9Kb server.example.com => ip.address 395Kb 3.89Mb 1.07Mb <= 6.09Kb 109Kb 28.6Kb server.example.com => ip.address 4.55Mb 3.83Mb 1.04Mb <= 55.6Kb 45.4Kb 13.0Kb server.example.com => ip.address 649Kb 3.38Mb 1.47Mb <= 9.00Kb 38.7Kb 16.7Kb server.example.com => ip.address 5.00Mb 3.32Mb 1.80Mb <= 65.7Kb 55.1Kb 29.4Kb server.example.com => ip.address 387Kb 3.13Mb 1.06Mb <= 18.4Kb 39.9Kb 15.0Kb server.example.com => ip.address 3.27Mb 3.11Mb 1.01Mb <= 81.2Kb 64.5Kb 20.9Kb server.example.com => ip.address 1.75Mb 3.08Mb 2.72Mb <= 16.6Kb 35.6Kb 32.5Kb server.example.com => ip.address 1.75Mb 2.90Mb 2.79Mb <= 22.4Kb 32.6Kb 35.6Kb server.example.com => ip.address 3.03Mb 2.78Mb 1.82Mb <= 26.6Kb 27.4Kb 20.2Kb server.example.com => ip.address 2.26Mb 2.66Mb 1.36Mb <= 51.7Kb 49.1Kb 24.4Kb server.example.com => ip.address 586Kb 2.50Mb 1.03Mb <= 4.17Kb 26.1Kb 10.7Kb server.example.com => ip.address 2.42Mb 2.49Mb 2.44Mb <= 31.6Kb 29.7Kb 29.9Kb server.example.com => ip.address 2.41Mb 2.46Mb 2.41Mb <= 26.4Kb 24.5Kb 23.8Kb server.example.com => ip.address 2.37Mb 2.39Mb 2.40Mb <= 28.9Kb 27.0Kb 28.5Kb server.example.com => ip.address 525Kb 2.20Mb 1.05Mb <= 7.03Kb 26.0Kb 12.8Kb qqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqq TX: cum: 102GB peak: 1.65Gb rates: 1.46Gb 1.44Gb 1.48Gb RX: 1.31GB 24.3Mb 19.5Mb 18.9Mb 20.0Mb TOTAL: 103GB 1.67Gb 1.48Gb 1.46Gb 1.50Gb I check the transfer speed using iperf utility From Server A to Server B # iperf -c 0.0.0.2 -p 8777 ------------------------------------------------------------ Client connecting to 0.0.0.2, TCP port 8777 TCP window size: 85.3 KByte (default) ------------------------------------------------------------ [ 3] local 0.0.0.1 port 38895 connected with 0.0.0.2 port 8777 [ ID] Interval Transfer Bandwidth [ 3] 0.0-10.8 sec 528 KBytes 399 Kbits/sec My Current Connections in Server B # netstat -an|grep ":8777"|awk '/tcp/ {print $6}'|sort -nr| uniq -c 2072 TIME_WAIT 28 SYN_RECV 1 LISTEN 189 LAST_ACK 139 FIN_WAIT2 373 FIN_WAIT1 3381 ESTABLISHED 34 CLOSING Server A Network Card Information Settings for eth0: Supported ports: [ TP ] Supported link modes: 100baseT/Full 1000baseT/Full 10000baseT/Full Supported pause frame use: No Supports auto-negotiation: Yes Advertised link modes: 10000baseT/Full Advertised pause frame use: No Advertised auto-negotiation: Yes Speed: 10000Mb/s Duplex: Full Port: Twisted Pair PHYAD: 0 Transceiver: external Auto-negotiation: on MDI-X: Unknown Supports Wake-on: d Wake-on: d Current message level: 0x00000007 (7) drv probe link Link detected: yes Server B Network Card Information Settings for eth2: Supported ports: [ FIBRE ] Supported link modes: 10000baseT/Full Supported pause frame use: No Supports auto-negotiation: No Advertised link modes: 10000baseT/Full Advertised pause frame use: No Advertised auto-negotiation: No Speed: 10000Mb/s Duplex: Full Port: Direct Attach Copper PHYAD: 0 Transceiver: external Auto-negotiation: off Supports Wake-on: d Wake-on: d Current message level: 0x00000007 (7) drv probe link Link detected: yes ifconfig server A eth0 Link encap:Ethernet HWaddr 00:25:90:ED:9E:AA inet addr:0.0.0.1 Bcast:0.0.0.255 Mask:255.255.255.0 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:1202795665 errors:0 dropped:64334 overruns:0 frame:0 TX packets:2313161968 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:893413096188 (832.0 GiB) TX bytes:3360949570454 (3.0 TiB) lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:65536 Metric:1 RX packets:2207544 errors:0 dropped:0 overruns:0 frame:0 TX packets:2207544 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:247769175 (236.2 MiB) TX bytes:247769175 (236.2 MiB) ifconfig Server B eth2 Link encap:Ethernet HWaddr 00:25:90:82:C4:FE inet addr:0.0.0.2 Bcast:0.0.0.2 Mask:255.255.255.0 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:39973046980 errors:0 dropped:1828387600 overruns:0 frame:0 TX packets:69618752480 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:3013976063688 (2.7 TiB) TX bytes:102250230803933 (92.9 TiB) lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:65536 Metric:1 RX packets:1049495 errors:0 dropped:0 overruns:0 frame:0 TX packets:1049495 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:129012422 (123.0 MiB) TX bytes:129012422 (123.0 MiB) Netstat -i on Server B # netstat -i Kernel Interface table Iface MTU Met RX-OK RX-ERR RX-DRP RX-OVR TX-OK TX-ERR TX-DRP TX-OVR Flg eth2 9000 0 42098629968 0 2131223717 0 73698797854 0 0 0 BMRU lo 65536 0 1077908 0 0 0 1077908 0 0 0 LRU I Turn up send/receive buffers on the network card to 2048 and problem still persist I increase the MTU for server A and problem still persist and i increase the MTU for server B for better connectivity and transfer speed but it couldn't transfer at all The problem is : as you can see from iperf utility, the transfer speed from server A to server B slow when i restart network service in server B the transfer in server A at full speed, after 2 minutes , it's getting slow How could i troubleshoot slow speed issue and fix it in server B ? Notice : if there any other commands i should execute in servers for more information, so it might help resolve the problem , let me know in comments

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