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• How to find optimal path visit every node with parallel workers complicated by dynamic edge costs?

  - by Aaron Anodide

  Say you have an acyclic directed graph with weighted edges and create N workers. My goal is to calculate the optimal way those workers can traverse the entire graph in parralel. However, edge costs may change along the way. Example: A -1-> B A -2-> C B -3-> C (if A has already been visited) B -5-> C (if A has not already been visited) Does what I describe lend itself to a standard algorithmic approach, or alternately can someone suggest if I'm looking at this in an inherently flawed way (i have an intuition I might be)?

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• How to display consistent background image

  - by Tofu_Craving_Redish_BlueDragon

  Drawing a large background is relatively slow in PyGame. In order to avoid drawing BG every frame, you could draw it once, then do nothing. However, if something is overdrawn onto the surface and keeps moving, you will need to redraw the background in order to "erase" the color pixels left by moving object; otherwise, you will have "traces" of the moving object. I have a moving object in my PyGame. However, I do not want to "clear the color buffer" by redrawing the background image. Redrawing the background image every frame is slow. My solution : I will "clear" only required portions (where the "traces" of moving object are left) of the "buffer" by redrawing portions of background. Is there any other better way to have a consistent background?

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• What techniques can I use to render very large numbers of objects more efficiently in OpenGL?

  - by Luke

  You can think of my application as drawing a very large ball-and-stick diagram (or graph). At times, this graph can get very large, where the number of elements even outnumbers the pixels on the screen. Currently I am simply passing all of my textures (as GL_POINTS) and lines to the graphics card using VBO's. When the number of elements outnumbers the number of pixels, is this the most efficient way to do this? Or should I do some calculations on the CPU side before handing everything over to the GPU? If it matters, I do use GL_DEPTH_TEST and GL_ALPHA_TEST. I do some alpha blending, but probably not enough to make a huge performance difference. My scene can be static at times, but the user has control over a typical arc-ball camera and can pan, rotate, or zoom. It is during these operations that performance degradation is noticeable.

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• Which app can I use for easily annotating pictures/screenshots?

  - by koushik

  Often I need to annotate (draw some arrows, lines, basic shapes like squares, ellipses etc and enter some text) on top of pictures (JPG, PNG images) and screenshots (again png images). I would also need to be able to crop, resize etc. I tried the Gimp but I could only enter text and perform all image transformations but couldn't find a way to draw boxes etc. I finally settled to Openoffice.org draw, but I know that isn't what I want, because in oodraw I need to insert my pic into a drawing and resize it (or the drawing) to fit and then go about making changes and finally export to png... Is there any image editor that allows adding shapes and text to jpg & png files and save the modified file in its place? If the tool can also have template collections (like dia does) for shapes that is an added bonus.

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• Letting the user draw a Polygon Body and Image

  - by Siddharth

  In my game, I want to provide the user with a drawing feature. By free hand drawing, the user creates a polygon shape. Then, in my game implementation, I have to create a body for the found vertices and generate an image based on that polygon shape. My problem is how to create an image that matches the user-provided vertices. I've heard that cocos2d has something called Image Masking. I don't understand how I could implement it in AndEngine. Could someone help?

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• Statistics for facebook like button

  - by bessarabov

  I have a small site with facebook like button. I want to find out the information about what pages are liked. I've found url http://graph.facebook.com/?id=http://imdb.com but it shows only overal count for the site. I think that I can ask http://graph.facebook.com/?ids=url1,url2 with all my pages as the parameters to get detailed information, but this seems to be an ugly solution. A have lots of pages, so I have to ask facebook many times. Maybe there is some simple way of finding the information I need?

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• Edit and render RichText

  - by OregonGhost

  We have an application (a custom network management tool for building automation) that supports printing labels that you can cut out and insert into the devices' front displays. In earlier versions of the tool (not developed in my company), the application just pushed the strings into an Excel file that the field technician could then manipulate (like formatting text). We didn't do this in the new version because it was hard (impossible) to keep the Excel file in sync, and to avoid a binding to an external application (let alone different versions of Excel). We're using PDFSharp for rendering the labels. It has a System.Drawing-like interface, but can output to a System.Drawing.Graphics (screen / printer) as well as to a PDF file, which is a requirement. Later, basic formatting was introduced like Font Family, Style, Size, Color which would apply to one label (i.e. to exactly one string). Now the customer wants to be able to apply these formats to single characters in a string. I think the easiest way would be to support a subset of RichText. It's not as easy as I thought though. Currently the editor just displays a TextBox for the label you want to edit, with the font set to the label's font. I thought I'd just replace it with RichTextBox, and update the formatting buttons to use the RichTextBox formatting properties. Fairly easy. However, I need to draw the text. I know you can get the RichTextBox to draw to a HDC or System.Drawing.Graphics - but as already said, I need it to use PDFSharp. Rendering to bitmaps is not an option, since the PDF must not be huge, and it's a lot of labels. Unfortunately I couldn't get the RichTextBox to tell me the layout of the text - I'm fine with doing the actual rendering by hand, as long as I know where to draw what. This is the first question: How can I get the properly layouted metrics of the rich text out of a RichTextBox? Or is there any way to convert the rich text to a vector graphics format that can be easily drawn manually? I know about NRTFTree which can be used to parse and manipulate RichText. The documentation is bad (actually I don't know, it's Spanish), but I think I can get it to work. As far as I understood, it won't provide layouting as well. Because of this, I think I'll have to write a custom edit control (remember, it's basically just one or two line labels with basic RTF formatting, not a full-fledged edit control - more like editing a textbox in PowerPoint) and write custom text layout logic that used PDFSharp rather than System.Drawing for drawing. Is there any existing, even if partial, solution available, either for the editing or for doing the layout manually (or both)? Or is there an entirely different approach I'm just not seeing? Bonus points if exporting the label texts as RTF into a CSV file, and then importing in Excel retains the formatting. For the editing part, I need it to work in Windows Forms. Other than that it's not Windows-Forms-related, I think.

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• c# opennetCF background worker - e.result gives a ObjectDisposedException

  - by ikky

  Hi! I'm new working with background worker in C#. Here is a class, and under it, you will find the instansiation of it, and under there i will define my problem for you: I have the class Drawing: class Drawing { BackgroundWorker bgWorker; ProgressBar progressBar; Panel panelHolder; public Drawing(ref ProgressBar pgbar, ref Panel panelBig) // Progressbar and panelBig as reference { this.panelHolder = panelBig; this.progressBar = pgbar; bgWorker = new BackgroundWorker(); bgWorker.WorkerReportsProgress = true; bgWorker.WorkerSupportsCancellation = true; bgWorker.DoWork += new OpenNETCF.ComponentModel.DoWorkEventHandler(this.bgWorker_DoWork); bgWorker.RunWorkerCompleted += new OpenNETCF.ComponentModel.RunWorkerCompletedEventHandler(this.bgWorker_RunWorkerCompleted); bgWorker.ProgressChanged += new OpenNETCF.ComponentModel.ProgressChangedEventHandler(this.bgWorker_ProgressChanged); } public void createDrawing() { bgWorker.RunWorkerAsync(); } private void bgWorker_DoWork(object sender, DoWorkEventArgs e) { Panel panelContainer = new Panel(); // Adding panels to the panelContainer for(i=0; i<100; i++) { Panel panelSubpanel = new Panel(); // Setting size, color, name etc.... panelContainer.Controls.Add(panelSubpanel); // Adding the subpanel to the panelContainer //Report the progress bgWorker.ReportProgress(0, i); // Reporting number of panels loaded } e.Result = imagePanel; // Send the result(a panel with lots of subpanels) as an argument } private void bgWorker_ProgressChanged(object sender, ProgressChangedEventArgs e) { this.progressBar.Value = (int)e.UserState; this.progressBar.Update(); } private void bgWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e) { if (e.Error == null) { this.panelHolder = (Panel)e.Result; } else { MessageBox.Show("An error occured, please try again"); } } } Instansiating an object of this class: public partial class Draw: Form { public Draw() { ProgressBar progressBarLoading = new ProgressBar(); // Set lots of properties on progressBarLoading Panel panelBigPanelContainer = new Panel(); Drawing drawer = new Drawing(ref progressBarLoading, ref panelBigPanelContainer); drawer.createDrawing(); // this makes the object start a new thread, loading all the panels into a panel container, while also sending the progress to this progressbar. } } Here is my problem: In the private void bgWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e) i don't get the e.Result as it should be. When i debug and look at the e.Result, the panel's properties have this exception message: '((System.Windows.Forms.Control)(e.Result)).ClientSize' threw an exception of type 'System.ObjectDisposedException' So the object gets disposed, but "why" is my question, and how can i fix this? I hope someone will answer me, this is making me crazy. Another question i have: Is it allowed to use "ref" with arguments? is it bad programming? Thanks in advance. I have also written how i understand the Background worker below here: This is what i think is the "rules" for background workers: bgWorker.RunWorkerAsync(); => starts a new thread. bgWorker_DoWork cannot reach the main thread without delegates - private void bgWorker_DoWork(object sender, DoWorkEventArgs e) { // The work happens here, this is a thread that is not reachable by the main thread e.Result => This is an argument which can be reached by bgWorker_RunWorkerCompleted() bgWorker.ReportProgress(progressVar); => Reports the progress to the bgWorker_ProgressChanged() } - private void bgWorker_ProgressChanged(object sender, ProgressChangedEventArgs e) { // I get the progress here, and can do stuff to the main thread from here (e.g update a control) this.ProgressBar.Value = e.ProgressPercentage; } - private void bgWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e) { // This is where the thread is completed. // Here i can get e.Result from the bgWorker thread // From here i can reach controls in my main thread, and use e.Result in my main thread if (e.Error == null) { this.panelTileHolder = (Panel)e.Result; } else { MessageBox.Show("There was an error"); } }

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• asp.net image aspect ratio help

  - by StealthRT

  Hey all, i am in need of some help with keeping an image aspect ratio in check. This is the aspx code that i have to resize and upload an image the user selects. <%@ Page Trace="False" Language="vb" aspcompat="false" debug="true" validateRequest="false"%> <%@ Import Namespace=System.Drawing %> <%@ Import Namespace=System.Drawing.Imaging %> <%@ Import Namespace=System %> <%@ Import Namespace=System.Web %> <SCRIPT LANGUAGE="VBScript" runat="server"> const Lx = 500 ' max width for thumbnails const Ly = 60 ' max height for thumbnails const upload_dir = "/uptest/" ' directory to upload file const upload_original = "sample" ' filename to save original as (suffix added by script) const upload_thumb = "thumb" ' filename to save thumbnail as (suffix added by script) const upload_max_size = 512 ' max size of the upload (KB) note: this doesn't override any server upload limits dim fileExt ' used to store the file extension (saves finding it mulitple times) dim newWidth, newHeight as integer ' new width/height for the thumbnail dim l2 ' temp variable used when calculating new size dim fileFld as HTTPPostedFile ' used to grab the file upload from the form Dim originalimg As System.Drawing.Image ' used to hold the original image dim msg ' display results dim upload_ok as boolean ' did the upload work ? </script> <% randomize() ' used to help the cache-busting on the preview images upload_ok = false if lcase(Request.ServerVariables("REQUEST_METHOD"))="post" then fileFld = request.files(0) ' get the first file uploaded from the form (note:- you can use this to itterate through more than one image) if fileFld.ContentLength > upload_max_size * 1024 then msg = "Sorry, the image must be less than " & upload_max_size & "Kb" else try originalImg = System.Drawing.Image.FromStream(fileFld.InputStream) ' work out the width/height for the thumbnail. Preserve aspect ratio and honour max width/height ' Note: if the original is smaller than the thumbnail size it will be scaled up If (originalImg.Width/Lx) > (originalImg.Width/Ly) Then L2 = originalImg.Width newWidth = Lx newHeight = originalImg.Height * (Lx / L2) if newHeight > Ly then newWidth = newWidth * (Ly / newHeight) newHeight = Ly end if Else L2 = originalImg.Height newHeight = Ly newWidth = originalImg.Width * (Ly / L2) if newWidth > Lx then newHeight = newHeight * (Lx / newWidth) newWidth = Lx end if End If Dim thumb As New Bitmap(newWidth, newHeight) 'Create a graphics object Dim gr_dest As Graphics = Graphics.FromImage(thumb) ' just in case it's a transparent GIF force the bg to white dim sb = new SolidBrush(System.Drawing.Color.White) gr_dest.FillRectangle(sb, 0, 0, thumb.Width, thumb.Height) 'Re-draw the image to the specified height and width gr_dest.DrawImage(originalImg, 0, 0, thumb.Width, thumb.Height) try fileExt = System.IO.Path.GetExtension(fileFld.FileName).ToLower() originalImg.save(Server.MapPath(upload_dir & upload_original & fileExt), originalImg.rawformat) thumb.save(Server.MapPath(upload_dir & upload_thumb & fileExt), originalImg.rawformat) msg = "Uploaded " & fileFld.FileName & " to " & Server.MapPath(upload_dir & upload_original & fileExt) upload_ok = true catch msg = "Sorry, there was a problem saving the image." end try ' Housekeeping for the generated thumbnail if not thumb is nothing then thumb.Dispose() thumb = nothing end if catch msg = "Sorry, that was not an image we could process." end try end if ' House Keeping ! if not originalImg is nothing then originalImg.Dispose() originalImg = nothing end if end if %> What i am looking for is a way to just have it go by the height of what i set it: const Ly = 60 ' max height for thumbnails And have the code for the width just be whatever. So if i had an image... say 600 x 120 (w h) and i used photoshop to change just the height, it would keep it in ratio and have it 300 x 60 (w x h). Thats what i am looking to do with this code here. However, i can not think of a way to do this (or to just leave a wildcard for the width setting. Any help would be great :o) David

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• Emulating old-school sprite flickering (theory and concept)

  - by Jeffrey Kern

  I'm trying to develop an oldschool NES-style video game, with sprite flickering and graphical slowdown. I've been thinking of what type of logic I should use to enable such effects. I have to consider the following restrictions if I want to go old-school NES style: No more than 64 sprites on the screen at a time No more than 8 sprites per scanline, or for each line on the Y axis If there is too much action going on the screen, the system freezes the image for a frame to let the processor catch up with the action From what I've read up, if there were more than 64 sprites on the screen, the developer would only draw high-priority sprites while ignoring low-priority ones. They could also alternate, drawing each even numbered sprite on opposite frames from odd numbered ones. The scanline issue is interesting. From my testing, it is impossible to get good speed on the XBOX 360 XNA framework by drawing sprites pixel-by-pixel, like the NES did. This is why in old-school games, if there were too many sprites on a single line, some would appear if they were cut in half. For all purposes for this project, I'm making scanlines be 8 pixels tall, and grouping the sprites together per scanline by their Y positioning. So, dumbed down I need to come up with a solution that.... 64 sprites on screen at once 8 sprites per 'scanline' Can draw sprites based on priority Can alternate between sprites per frame Emulate slowdown Here is my current theory First and foremost, a fundamental idea I came up with is addressing sprite priority. Assuming values between 0-255 (0 being low), I can assign sprites priority levels, for instance: 0 to 63 being low 63 to 127 being medium 128 to 191 being high 192 to 255 being maximum Within my data files, I can assign each sprite to be a certain priority. When the parent object is created, the sprite would randomly get assigned a number between its designated range. I would then draw sprites in order from high to low, with the end goal of drawing every sprite. Now, when a sprite gets drawn in a frame, I would then randomly generate it a new priority value within its initial priority level. However, if a sprite doesn't get drawn in a frame, I could add 32 to its current priority. For example, if the system can only draw sprites down to a priority level of 135, a sprite with an initial priority of 45 could then be drawn after 3 frames of not being drawn (45+32+32+32=141) This would, in theory, allow sprites to alternate frames, allow priority levels, and limit sprites to 64 per screen. Now, the interesting question is how do I limit sprites to only 8 per scanline? I'm thinking that if I'm sorting the sprites high-priority to low-priority, iterate through the loop until I've hit 64 sprites drawn. However, I shouldn't just take the first 64 sprites in the list. Before drawing each sprite, I could check to see how many sprites were drawn in it's respective scanline via counter variables . For example: Y-values between 0 to 7 belong to Scanline 0, scanlineCount[0] = 0 Y-values between 8 to 15 belong to Scanline 1, scanlineCount[1] = 0 etc. I could reset the values per scanline for every frame drawn. While going down the sprite list, add 1 to the scanline's respective counter if a sprite gets drawn in that scanline. If it equals 8, don't draw that sprite and go to the sprite with the next lowest priority. SLOWDOWN The last thing I need to do is emulate slowdown. My initial idea was that if I'm drawing 64 sprites per frame and there's still more sprites that need to be drawn, I could pause the rendering by 16ms or so. However, in the NES games I've played, sometimes there's slowdown if there's not any sprite flickering going on whereas the game moves beautifully even if there is some sprite flickering. Perhaps give a value to each object that uses sprites on the screen (like the priority values above), and if the combined values of all objects w/ sprites surpass a threshold, introduce the sprite flickering? IN CONCLUSION... Does everything I wrote actually sound legitimate and could work, or is it a pipe dream? What improvements can you all possibly think with this game programming theory of mine?

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• How to remove a model object from an EMF model and its GEF Editor via Adapter

  - by s.d

  This question is principally a follow-up to my question about EMF listening mechanisms. So, I have a third-party EMF model (uneditable) which is based on a generic graph model. The structure is as follows: Project | ItemGraph | Item | Document | DocumentGraph / | \ Tokens Nodes Relations(Edges) I have a GEF editor which works on the DocumentGraph (i.e., not the root object, perhaps this is a problem?): getGraphicalViewer().setContents(documentGraph). THe editor has the following edit part structure: DocumentGraphEP / \ Primary Connection LayerEP LayerEP / \ | TokenEP NodeEP RelationEP PrimaryLayerEP and ConnectionLayerEP both have simple Strings as model, which are not represented in the EMF (domain) model. They are simply used to add a primary (i.e., node) layer, and a connection layer (with ShortestPathConnectionRouter) to the editor. Problem: I am trying to get myself into the workings of EMF adapters, and have tried to make use of the available tutorials, mainly the EMF-GEF Eclipse tutorial, vainolo's blog, and vogella's tutorial. I thought I'd start with an easy thing, so tried to remove a node from the graph and see if I get it to work. Which I didn't, and I don't see where the problem is. I can select a node, and have the generic delete Action in my toolbar, but when I click it, nothing happens. Here is the respective source code for the different responsible parts. Please be so kind to point me to any errors (of thinking, coding errors, whathaveyou) you can find. NodeEditPart public class NodeEditPart extends AbstractGraphicalEditPart implements Adapter { protected IFigure createFigure() { return new NodeFigure(); } protected void createEditPolicies() { .... installEditPolicy(EditPolicy.COMPONENT_ROLE, new NodeComponentEditPolicy()); } protected void refreshVisuals() { NodeFigure figure = (NodeFigure) getFigure(); SNode model = (SNode) getModel(); PrimaryLayerEditPart parent = (PrimaryLayerEditPart) getParent(); // Set text figure.getLabel().setText(model.getSName()); .... } public void activate() { if (isActive()) return; // start listening for changes in the model ((Notifier)getModel()).eAdapters().add(this); super.activate(); } public void deactivate() { if (!isActive()) return; // stop listening for changes in the model ((Notifier)getModel()).eAdapters().remove(this); super.deactivate(); } private Notifier getSDocumentGraph() { return ((SNode)getModel()).getSDocumentGraph(); } @Override public void notifyChanged(Notification notification) { int type = notification.getEventType(); switch( type ) { case Notification.ADD: case Notification.ADD_MANY: case Notification.REMOVE: case Notification.REMOVE_MANY: refreshChildren(); break; case Notification.SET: refreshVisuals(); break; } } @Override public Notifier getTarget() { return target; } @Override public void setTarget(Notifier newTarget) { this.target = newTarget; } @Override public boolean isAdapterForType(Object type) { return type.equals(getModel().getClass()); } } NodeComponentEditPolicy public class NodeComponentEditPolicy extends ComponentEditPolicy { public NodeComponentEditPolicy() { super(); } protected Command createDeleteCommand(GroupRequest deleteRequest) { DeleteNodeCommand cmd = new DeleteNodeCommand(); cmd.setSNode((SNode) getHost().getModel()); return cmd; } } DeleteNodeCommand public class DeleteNodeCommand extends Command { private SNode node; private SDocumentGraph graph; @Override public void execute() { node.setSDocumentGraph(null); } @Override public void undo() { node.setSDocumentGraph(graph); } public void setSNode(SNode node) { this.node = node; this.graph = node.getSDocumentGraph(); } } All seems to work fine: When a node is selected in the editor, the delete symbol is activated in the toolbar, but when it is clicked, nothing happens in the editor. I'd be very thankful for any pointers :).

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• Cacti not working for SNMP data sources

  - by lorenzo-s

  I installed packages cacti and snmpd on a Debian server. I'm able to display common graphs in Cacti (such as memory usage, load average, logged in users, etc) using the data templates listed as Unix. Now I want to replace these graphs with new ones using SNMP data sources, because I see there is also CPU usage and because it's not excluded I have to manage multiple hosts in the future. So, I installed snmpd on the machine and left the snmpd.conf as it is. In Cacti, I created three new data sources from SNMP templates for 127.0.0.1 host: ucd/net - CPU Usage - Nice ucd/net - CPU Usage - System ucd/net - CPU Usage - User Then I created a new graph from template ucd/net - CPU Usage, and select the three data sources in the Graph Item Fields section. Graph is now enabled and running, but empty. No data have been collected. Under Console - Devices my SNMP host is listed as up and running: System:Linux ip-xx-xx-xxx-xxx 3.2.0-23-virtual #36-Ubuntu SMP Tue Apr 10 22:29:03 UTC 2012 x86_64 Uptime: 929267 (0 days, 2 hours, 34 minutes) Hostname: ip-xx-xx-xxx-xxx Location: Sitting on the Dock of the Bay Contact: Me [email protected] In SNMP Options I left all as it is: SNMP Version: Version 1 SNMP Community: public SNMP Timeout: 500 ms Maximum OID's Per Get Request: 10 In Console - Utilities - Cacti Log I have multiple warning (two for each data source) every 5 minutes: 10/29/2012 01:45:01 PM - CMDPHP: Poller[0] Host[2] DS[18] WARNING: Result from SNMP not valid. Partial Result: U 10/29/2012 01:45:01 PM - CMDPHP: Poller[0] WARNING: SNMP Get Timeout for Host:'127.0.0.1', and OID:'.1.3.6.1.4.1.2021.4.15.0' 10/29/2012 01:45:01 PM - CMDPHP: Poller[0] Host[1] DS[9] WARNING: Result from SNMP not valid. Partial Result: U 10/29/2012 01:45:01 PM - CMDPHP: Poller[0] WARNING: SNMP Get Timeout for Host:'127.0.0.1', and OID:'.1.3.6.1.4.1.2021.11.52.0' 10/29/2012 01:40:01 PM - CMDPHP: Poller[0] Host[2] DS[19] WARNING: Result from SNMP not valid. Partial Result: U 10/29/2012 01:40:01 PM - CMDPHP: Poller[0] WARNING: SNMP Get Timeout for Host:'127.0.0.1', and OID:'.1.3.6.1.4.1.2021.4.6.0' [...] I have the feeling I'm missing something, but I cannot get it...

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• Cacti is ignoring hash marks in interface aliases

  - by Matt Simmons

  I'm attempting to set up Cacti to monitor a router's interfaces, and I'm having trouble getting the graph templates to show the information that I'd like. Our interface configuration looks like this: interface GigabitEthernet3/6 description WalljackNumber # Server info no ip address no shutdown switchport switchport access vlan 116 switchport mode access ip dhcp snooping trust spanning-tree portfast The "Server Info" string is really just the machine name, and a short relevant description, such as "PolarSprings vmnic2". The important part appears to be that it follows the hashmark. When I run snmpwalk, I get the proper output: IF-MIB::ifAlias.230 = STRING: WalljackNumber # Server info But in Cacti, when I go into the graph templates and set the title to this: |host_description| - Traffic - |query_ifName| (|query_ifAlias|) All that shows up in the graph is: switchname - Traffic - Gi3/6 (WalljackNumber #) Which strikes me as a little weird. What I suppose MAY be happening is that somewhere in the cacti stream, it's interpreting # as being a comment and stripping everything after, but I'm not sure. I was hoping someone could tell me that this was a known documented behavior, or that I could change it in a setting that I wasn't aware of. The alternative answer is to change the delimiter from # to something else, but I've got over a thousand lit switchports on an old college infrastructure, and I'm not sure what else might be relying on them.

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• Preventing DDOS/SYN attacks (as far as possible)

  - by Godius

  Recently my CENTOS machine has been under many attacks. I run MRTG and the TCP connections graph shoots up like crazy when an attack is going on. It results in the machine becoming inaccessible. My MRTG graph: mrtg graph This is my current /etc/sysctl.conf config # Kernel sysctl configuration file for Red Hat Linux # # For binary values, 0 is disabled, 1 is enabled. See sysctl(8) and # sysctl.conf(5) for more details. # Controls IP packet forwarding net.ipv4.ip_forward = 0 # Controls source route verification net.ipv4.conf.default.rp_filter = 1 # Do not accept source routing net.ipv4.conf.default.accept_source_route = 0 # Controls the System Request debugging functionality of the kernel kernel.sysrq = 1 # Controls whether core dumps will append the PID to the core filename # Useful for debugging multi-threaded applications kernel.core_uses_pid = 1 # Controls the use of TCP syncookies net.ipv4.tcp_syncookies = 1 # Controls the maximum size of a message, in bytes kernel.msgmnb = 65536 # Controls the default maxmimum size of a mesage queue kernel.msgmax = 65536 # Controls the maximum shared segment size, in bytes kernel.shmmax = 68719476736 # Controls the maximum number of shared memory segments, in pages kernel.shmall = 4294967296 net.ipv4.conf.all.rp_filter = 1 net.ipv4.tcp_syncookies = 1 net.ipv4.icmp_echo_ignore_broadcasts = 1 net.ipv4.conf.all.accept_redirects = 0 net.ipv6.conf.all.accept_redirects = 0 net.ipv4.conf.all.send_redirects = 0 net.ipv4.conf.all.accept_source_route = 0 net.ipv4.conf.all.rp_filter = 1 net.ipv4.tcp_max_syn_backlog = 1280 Futher more in my Iptables file (/etc/sysconfig/iptables ) I only have this setup # Generated by iptables-save v1.3.5 on Mon Feb 14 07:07:31 2011 *filter :INPUT ACCEPT [1139630:287215872] :FORWARD ACCEPT [0:0] :OUTPUT ACCEPT [1222418:555508541] Together with the settings above, there are about 800 IP's blocked via the iptables file by lines like: -A INPUT -s 82.77.119.47 -j DROP These have all been added by my hoster, when Ive emailed them in the past about attacks. Im no expert, but im not sure if this is ideal. My question is, what are some good things to add to the iptables file and possibly other files which would make it harder for the attackers to attack my machine without closing out any non-attacking users. Thanks in advance!

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• What can cause kernel out_of_memory error?

  - by nbolton

  I'm running Debian GNU/Linux 5.0 and I'm experiencing intermittent out_of_memory errors coming from the kernel. The server stops responding to all but pings, and I have to reboot the server. # uname -a Linux xxx 2.6.18-164.9.1.el5xen #1 SMP Tue Dec 15 21:31:37 EST 2009 x86_64 GNU/Linux This seems to be the important bit from /var/log/messages Dec 28 20:16:25 slarti kernel: Call Trace: Dec 28 20:16:25 slarti kernel: [<ffffffff802bedff>] out_of_memory+0x8b/0x203 Dec 28 20:16:25 slarti kernel: [<ffffffff8020f825>] __alloc_pages+0x245/0x2ce Dec 28 20:16:25 slarti kernel: [<ffffffff8021377f>] __do_page_cache_readahead+0xc6/0x1ab Dec 28 20:16:25 slarti kernel: [<ffffffff80214015>] filemap_nopage+0x14c/0x360 Dec 28 20:16:25 slarti kernel: [<ffffffff80208ebc>] __handle_mm_fault+0x443/0x1337 Dec 28 20:16:25 slarti kernel: [<ffffffff8026766a>] do_page_fault+0xf7b/0x12e0 Dec 28 20:16:25 slarti kernel: [<ffffffff8026ef17>] monotonic_clock+0x35/0x7b Dec 28 20:16:25 slarti kernel: [<ffffffff80262da3>] thread_return+0x6c/0x113 Dec 28 20:16:25 slarti kernel: [<ffffffff8021afef>] remove_vma+0x4c/0x53 Dec 28 20:16:25 slarti kernel: [<ffffffff80264901>] _spin_lock_irqsave+0x9/0x14 Dec 28 20:16:25 slarti kernel: [<ffffffff8026082b>] error_exit+0x0/0x6e Full snippet here: http://pastebin.com/a7eWf7VZ I thought that perhaps the server was actually running out of memory (it has 1GB physical memory), but my Cacti memory graph looks OK to me... But strangely the load graph goes through the roof shortly before the kernel crashes: What logs can I look at for more info? Update: Maybe noteworthy - the CPU percentage and network traffic graphs were both normal at the time of the crash. The only abnormality was the average load graph.

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• SSL connection hangs as client hello (curl, openssl client, apt-get, wget, everything)

  - by Niklas B

  Hi, I've run into a problem on my Debian VPS (a xen domU) regarding SSL. Namely almost all SSL connections hangs at client hello. For example: # curl -vI https://graph.facebook.com About to connect() to graph.facebook.com port 443 (#0) Trying 66.220.146.48... connected Connected to graph.facebook.com (66.220.146.48) port 443 (#0) successfully set certificate verify locations: CAfile: none CApath: /etc/ssl/certs SSLv3, TLS handshake, Client hello (1): It's the same when using the openssl client. However, some of the SSL traffic works (for example https://www.nordea.se). Server #uname -a Linux server.com 2.6.26-1-xen-amd64 #1 SMP Fri Mar 13 21:39:38 UTC 2009 x86_64 GNU/Linux It does however work on my Dom 0 (the main xen host). Apt-get I can't even run apt-get update with the debian security sources (hangs on reading headers) Open SSL At the begining I thought I had an old openssl client (0.9.8o-4) since I appeared to have a newer on the Dom 0 (0.9.8g-15+lenny8) but doing a manuanl update on the openssl deb didn't help. Open SSL Client This is the full output of when the openssl client hangs: http://pastebin.com/PAjwMap9 Closing thoughts I've Googled the crap out of this, and I'm not getting any further. I've seen problems with curl, apt-get etc. but they are all specific relating to the very application - not general for the system. Any thoughts?

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• How to display escaped characters in tmux status bar

  - by walrus

  i am running tmux from a tty on an embedded linux device. (NOT a terminal emulator) because the screen is rather small, i want to add some "icons" to the tmux status bar. to achieve this, i have simply created a font with the appropriate glyphs for things like battery, or wifi. i can load the font, and display the characters with calls that use an escape to the line drawing characters like so: echo -e "\xe\234\xf" \xe escapes me into line drawing character mode, \234 is my created character, and \xf returns me to normal character mode so my terminal doesnt start getting goofy. this works perfectly if i enter the command at the terminal whether tmux is started or not. the issue arises if i then try to use it in my ~/.tmux.conf file for the status bar. i currently have a line like this: set -g status-right "#(echo -e "\xe\234\xf") #(/script/to/output/powerlevel) this simply outputs \xe\234\xf powerlevel this goes the same if i try printf over echo. this is the output i would expect to get on the terminal if i made the call without passing -e to echo, or without enclosing the statement with quotes. i then decided to wrap the calls to the echo or printf in a shell script. again, the script works when called from the terminal, but not in tmux's status bar. now i get the unprintable character "?" instead of my icon, like this: ? powerlevel this is what i would expect if i did not use the line drawing escapes previously mentioned above, or if i tried to copy and paste the character as text using tmux. in addition, the calling of these character scripts screws up the rest of my status-right, as the clock has about 6 digits for minutes when it is called (though it correctly only updates two of them). how can i make tmux respect the escape characters? any help or insight is greatly appreciated.

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• The plugin of munin is always timed out

  - by haoX

  I want to use munin to make a graph of ttyACM0 in Linux, but munin can not create the graph. I found some information in "munin-node.log". it shows that "Service 'temperature' timed out". So I changed timeout to 60 or 120 in /munin/plugin-conf.d/munin-node, but it does not work. It's also timed out. Here is part of my code: if [ "$1" = "config" ]; then echo 'graph_title Temperature of board' echo 'graph_args --base 1000 -l 0' echo 'graph_vlabel temperature(°C)' echo 'graph_category temperature' echo 'graph_scale no' echo 'graph_info This graph shows the temperature of board' for i in 1 2 3 4 5; do case $i in 1) TYPE="Under PCB" ;; 2) TYPE="HDD" ;; 3) TYPE="PHY" ;; 4) TYPE="CPU" ;; 5) TYPE="Ambience" ;; esac name=$(clean_name $TYPE) if [ "$TYPE" != "NA" ]; then echo "temp_$name.label $TYPE"; fi done exit 0 fi for i in 1 2 3 4 5; do case $i in 1) TYPE="Under PCB" VALUE=$(head -1 /dev/ttyACM0 | awk '{print $1}') ;; 2) TYPE="HDD" VALUE=$(head -1 /dev/ttyACM0 | awk '{print $2}') ;; 3) TYPE="PHY" VALUE=$(head -1 /dev/ttyACM0 | awk '{print $3}') ;; 4) TYPE="CPU" VALUE=$(head -1 /dev/ttyACM0 | awk '{print $4}') ;; 5) TYPE="Ambience" VALUE=$(head -1 /dev/ttyACM0 | awk '{print $5}') ;; esac name=$(clean_name $TYPE) if [ "$TYPE" != "NA" ]; then echo "temp_$name.value $VALUE" fi

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• Easily Plotting Multiple Data Series in Excel

  - by John

  I really need help figuring out how to speed up graphing multiple series on a graph. I have seperate devices that give monthly readings for several variables like pressure, temperature, and salinity. Each of these variables is going to be its own graph with devices being the series. My x-axis is going to be the dates that these values were taken. The problem is that it takes ages to do this for each spreadsheet since I have monthly dates from 1950 up to the present and I have about 50 devices in each spreadsheet. I also have graphs for calculated values that are in columns next to them. Each of these devices is going to become a data series in the graph. E.g. In one of my graphs I have all the pressures from the devices and each of the data series' names is the name of the device. I want a fast way to do this. Doing this manually is taking a very long time. Please help! Is there any easier way to do this? It is consistent and the dates all line up. I am just repeating the same clicks over and over again Thank you!

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• Facebook Oauth Logout

  - by Derek Troy-West

  I have an application that integrates with Facebook using Oauth 2. I can authorize with FB and query their REST and Graph APIs perfectly well, but when I authorize an active browser session is created with FB. I can then log-out of my application just fine, but the session with FB persists, so if anyone else uses the browser they will see the previous users FB account (unless the previous user manually logs out of FB also). The steps I take to authorize are: Call [LINK: graph.facebook.com/oauth/authorize?client_id...] This step opens a Facebook login/connect window if the user's browser doesn't already have an active FB session. Once they log-in to facebook they redirect to my site with a code I can exchange for an oauth token. Call [LINK: graph.facebook.com/oauth/access_token?client_id..] with the code from (1) Now I have an Oauth Token, and the user's browser is logged into my site, and into FB. I call a bunch of APIs to do stuff: i.e. [LINK: graph.facebook.com/me?access_token=..] Lets say my user wants to log out of my site. The FB terms and conditions demand that I perform Single Sign Off, so when the user logs out of my site, they also are logged out of Facebook. There are arguments that this is a bit daft, but I'm happy to comply if there is any way of actually achieving that. I have seen suggestions that: A. I use the Javascript API to logout: FB.Connect.logout(). Well I tried using that, but it didn't work, and I'm not sure exactly how it could, as I don't use the Javascript API in any way on my site. The session isn't maintained or created by the Javascript API so I'm not sure how it's supposed to expire it either. B. Use [LINK: facebook.com/logout.php]. This was suggested by an admin in the Facebook forums some time ago. The example given related to the old way of getting FB sessions (non-oauth) so I don't think I can apply it in my case. C. Use the old REST api expireSession or revokeAuthorization. I tried both of these and while they do expire the Oauth token they don't invalidate the session that the browser is currently using so it has no effect, the user is not logged out of Facebook. I'm really at a bit of a loose end, the Facebook documentation is patchy, ambiguous and pretty poor. The support on the forums is non-existant, at the moment I can't even log in to the facebook forum, and aside from that, their own FB Connect integration doesn't even work on the forum itself. Doesn't inspire much confidence. Ta for any help you can offer. Derek ps. Had to change HTTPS to LINK, not enough karma to post links which is probably fair enough.

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• real time plotting on iPhone using core plot?

  - by ram007

  I want to use core-plot for drawing line graph dynamically. data won't come at a time, we will be receiving point by point dynamically. Is it possible to draw the chart dynamically using core-plot i.e drawing point by point as on when we receive the (x,y) point? Please help me, Thanks.

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• ext-js chart, multiple series on same chart

  - by user121196

  Ext-js Chart, I have a line graph, and I wish to add a single line(eg. average line) to the graph. The only way I can think of to emulate this line is to do the following: add an extra field with identical value to all my data points if, but this seems to be a waste and plus I don't want to show the dots that comes with the line. is there anyway to add an average line to my existing chart?

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• Clever ways of implementing different data structures in C & data structures that should be used mor

  - by Yktula

  What are some clever (not ordinary) ways of implementing data structures in C, and what are some data structures that should be used more often? For example, what is the most effective way (generating minimal overhead) to implement a directed and cyclic graph with weighted edges in C? I know that we can store the distances in an array as is done here, but what other ways are there to implement this kind of a graph?

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• Show frequencies along with barplot in ggplot2

  - by aL3xa

  I'm trying to display frequencies within barplot ... well, I want them somewhere in the graph: under the bars, within bars, above bars or in the legend area. And I recall (I may be wrong) that it can be done in ggplot2. This is probably an easy one... at least it seems easy. Here's the code: p <- ggplot(mtcars) p + aes(factor(cyl)) + geom_bar() Is there any chance that I can get frequencies embedded in the graph?

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• "Beveled" Shapes in Quartz 2D

  - by Shaggy Frog

  I'm familiar with some of the basics of Quartz 2D drawing, like drawing basic shapes and gradients and so on, but I'm not sure how to draw a shape with a "beveled" look, like this: Essentially we've got a shine on one corner, and maybe some shading in the opposite corner. I think -- I didn't make this image, although I'd like to be able to approximate it. Any ideas? This is on the iPhone, and I'd like to use built-in frameworks and avoid any external libraries if at all possible.

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