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  • Problem with my unicorn

    - by Johnny W
    I'd love to get some help with my unicorn, the damned thing just won't respond to my commands. It's a standard white unicorn with with a white mane. I've tried giving it hay, carrots and sugar cubes, but it's still refusing to do what I ask. I've read on other sites that I may need to reshoe her, but I'd rather not if I don't have to. Thanks for any help.

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  • OpenGL basics: calling glDrawElements once per object

    - by Bethor
    Hi all, continuing on from my explorations of the basics of OpenGL (see this question), I'm trying to figure out the basic principles of drawing a scene with OpenGL. I am trying to render a simple cube repeated n times in every direction. My method appears to yield terrible performance : 1000 cubes brings performance below 50fps (on a QuadroFX 1800, roughly a GeForce 9600GT). My method for drawing these cubes is as follows: done once: set up a vertex buffer and array buffer containing my cube vertices in model space set up an array buffer indexing the cube for drawing as 12 triangles done for each frame: update uniform values used by the vertex shader to move all cubes at once done for each cube, for each frame: update uniform values used by the vertex shader to move each cube to its position call glDrawElements to draw the positioned cube Is this a sane method ? If not, how does one go about something like this ? I'm guessing I need to minimize calls to glUniform, glDrawElements, or both, but I'm not sure how to do that. Full code for my little test : (depends on gletools and pyglet) I'm aware that my init code (at least) is really ugly; I'm concerned with the rendering code for each frame right now, I'll move to something a little less insane for the creation of the vertex buffers and such later on. import pyglet from pyglet.gl import * from pyglet.window import key from numpy import deg2rad, tan from gletools import ShaderProgram, FragmentShader, VertexShader, GeometryShader vertexData = [-0.5, -0.5, -0.5, 1.0, -0.5, 0.5, -0.5, 1.0, 0.5, -0.5, -0.5, 1.0, 0.5, 0.5, -0.5, 1.0, -0.5, -0.5, 0.5, 1.0, -0.5, 0.5, 0.5, 1.0, 0.5, -0.5, 0.5, 1.0, 0.5, 0.5, 0.5, 1.0] elementArray = [2, 1, 0, 1, 2, 3,## back face 4, 7, 6, 4, 5, 7,## front face 1, 3, 5, 3, 7, 5,## top face 2, 0, 4, 2, 4, 6,## bottom face 1, 5, 4, 0, 1, 4,## left face 6, 7, 3, 6, 3, 2]## right face def toGLArray(input): return (GLfloat*len(input))(*input) def toGLushortArray(input): return (GLushort*len(input))(*input) def initPerspectiveMatrix(aspectRatio = 1.0, fov = 45): frustumScale = 1.0 / tan(deg2rad(fov) / 2.0) fzNear = 0.5 fzFar = 300.0 perspectiveMatrix = [frustumScale*aspectRatio, 0.0 , 0.0 , 0.0 , 0.0 , frustumScale, 0.0 , 0.0 , 0.0 , 0.0 , (fzFar+fzNear)/(fzNear-fzFar) , -1.0, 0.0 , 0.0 , (2*fzFar*fzNear)/(fzNear-fzFar), 0.0 ] return perspectiveMatrix class ModelObject(object): vbo = GLuint() vao = GLuint() eao = GLuint() initDone = False verticesPool = [] indexPool = [] def __init__(self, vertices, indexing): super(ModelObject, self).__init__() if not ModelObject.initDone: glGenVertexArrays(1, ModelObject.vao) glGenBuffers(1, ModelObject.vbo) glGenBuffers(1, ModelObject.eao) glBindVertexArray(ModelObject.vao) initDone = True self.numIndices = len(indexing) self.offsetIntoVerticesPool = len(ModelObject.verticesPool) ModelObject.verticesPool.extend(vertices) self.offsetIntoElementArray = len(ModelObject.indexPool) ModelObject.indexPool.extend(indexing) glBindBuffer(GL_ARRAY_BUFFER, ModelObject.vbo) glEnableVertexAttribArray(0) #position glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 0, 0) glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ModelObject.eao) glBufferData(GL_ARRAY_BUFFER, len(ModelObject.verticesPool)*4, toGLArray(ModelObject.verticesPool), GL_STREAM_DRAW) glBufferData(GL_ELEMENT_ARRAY_BUFFER, len(ModelObject.indexPool)*2, toGLushortArray(ModelObject.indexPool), GL_STREAM_DRAW) def draw(self): glDrawElements(GL_TRIANGLES, self.numIndices, GL_UNSIGNED_SHORT, self.offsetIntoElementArray) class PositionedObject(object): def __init__(self, mesh, pos, objOffsetUf): super(PositionedObject, self).__init__() self.mesh = mesh self.pos = pos self.objOffsetUf = objOffsetUf def draw(self): glUniform3f(self.objOffsetUf, self.pos[0], self.pos[1], self.pos[2]) self.mesh.draw() w = 800 h = 600 AR = float(h)/float(w) window = pyglet.window.Window(width=w, height=h, vsync=False) window.set_exclusive_mouse(True) pyglet.clock.set_fps_limit(None) ## input forward = [False] left = [False] back = [False] right = [False] up = [False] down = [False] inputs = {key.Z: forward, key.Q: left, key.S: back, key.D: right, key.UP: forward, key.LEFT: left, key.DOWN: back, key.RIGHT: right, key.PAGEUP: up, key.PAGEDOWN: down} ## camera camX = 0.0 camY = 0.0 camZ = -1.0 def simulate(delta): global camZ, camX, camY scale = 10.0 move = scale*delta if forward[0]: camZ += move if back[0]: camZ += -move if left[0]: camX += move if right[0]: camX += -move if up[0]: camY += move if down[0]: camY += -move pyglet.clock.schedule(simulate) @window.event def on_key_press(symbol, modifiers): global forward, back, left, right, up, down if symbol in inputs.keys(): inputs[symbol][0] = True @window.event def on_key_release(symbol, modifiers): global forward, back, left, right, up, down if symbol in inputs.keys(): inputs[symbol][0] = False ## uniforms for shaders camOffsetUf = GLuint() objOffsetUf = GLuint() perspectiveMatrixUf = GLuint() camRotationUf = GLuint() program = ShaderProgram( VertexShader(''' #version 330 layout(location = 0) in vec4 objCoord; uniform vec3 objOffset; uniform vec3 cameraOffset; uniform mat4 perspMx; void main() { mat4 translateCamera = mat4(1.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f, 0.0f, cameraOffset.x, cameraOffset.y, cameraOffset.z, 1.0f); mat4 translateObject = mat4(1.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f, 0.0f, objOffset.x, objOffset.y, objOffset.z, 1.0f); vec4 modelCoord = objCoord; vec4 positionedModel = translateObject*modelCoord; vec4 cameraPos = translateCamera*positionedModel; gl_Position = perspMx * cameraPos; }'''), FragmentShader(''' #version 330 out vec4 outputColor; const vec4 fillColor = vec4(1.0f, 1.0f, 1.0f, 1.0f); void main() { outputColor = fillColor; }''') ) shapes = [] def init(): global camOffsetUf, objOffsetUf with program: camOffsetUf = glGetUniformLocation(program.id, "cameraOffset") objOffsetUf = glGetUniformLocation(program.id, "objOffset") perspectiveMatrixUf = glGetUniformLocation(program.id, "perspMx") glUniformMatrix4fv(perspectiveMatrixUf, 1, GL_FALSE, toGLArray(initPerspectiveMatrix(AR))) obj = ModelObject(vertexData, elementArray) nb = 20 for i in range(nb): for j in range(nb): for k in range(nb): shapes.append(PositionedObject(obj, (float(i*2), float(j*2), float(k*2)), objOffsetUf)) glEnable(GL_CULL_FACE) glCullFace(GL_BACK) glFrontFace(GL_CW) glEnable(GL_DEPTH_TEST) glDepthMask(GL_TRUE) glDepthFunc(GL_LEQUAL) glDepthRange(0.0, 1.0) glClearDepth(1.0) def update(dt): print pyglet.clock.get_fps() pyglet.clock.schedule_interval(update, 1.0) @window.event def on_draw(): with program: pyglet.clock.tick() glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT) glUniform3f(camOffsetUf, camX, camY, camZ) for shape in shapes: shape.draw() init() pyglet.app.run()

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  • How to pre-load all deployed assemblies for an AppDomain

    - by Andras Zoltan
    Given an App Domain, there are many different locations that Fusion (the .Net assembly loader) will probe for a given assembly. Obviously, we take this functionality for granted and, since the probing appears to be embedded within the .Net runtime (Assembly._nLoad internal method seems to be the entry-point when Reflect-Loading - and I assume that implicit loading is probably covered by the same underlying algorithm), as developers we don't seem to be able to gain access to those search paths. My problem is that I have a component that does a lot of dynamic type resolution, and which needs to be able to ensure that all user-deployed assemblies for a given AppDomain are pre-loaded before it starts its work. Yes, it slows down startup - but the benefits we get from this component totally outweight this. The basic loading algorithm I've already written is as follows. It deep-scans a set of folders for any .dll (.exes are being excluded at the moment), and uses Assembly.LoadFrom to load the dll if it's AssemblyName cannot be found in the set of assemblies already loaded into the AppDomain (this is implemented inefficiently, but it can be optimized later): void PreLoad(IEnumerable<string> paths) { foreach(path p in paths) { PreLoad(p); } } void PreLoad(string p) { //all try/catch blocks are elided for brevity string[] files = null; files = Directory.GetFiles(p, "*.dll", SearchOption.AllDirectories); AssemblyName a = null; foreach (var s in files) { a = AssemblyName.GetAssemblyName(s); if (!AppDomain.CurrentDomain.GetAssemblies().Any( assembly => AssemblyName.ReferenceMatchesDefinition( assembly.GetName(), a))) Assembly.LoadFrom(s); } } LoadFrom is used because I've found that using Load() can lead to duplicate assemblies being loaded by Fusion if, when it probes for it, it doesn't find one loaded from where it expects to find it. So, with this in place, all I now have to do is to get a list in precedence order (highest to lowest) of the search paths that Fusion is going to be using when it searches for an assembly. Then I can simply iterate through them. The GAC is irrelevant for this, and I'm not interested in any environment-driven fixed paths that Fusion might use - only those paths that can be gleaned from the AppDomain which contain assemblies expressly deployed for the app. My first iteration of this simply used AppDomain.BaseDirectory. This works for services, form apps and console apps. It doesn't work for an Asp.Net website, however, since there are at least two main locations - the AppDomain.DynamicDirectory (where Asp.Net places it's dynamically generated page classes and any assemblies that the Aspx page code references), and then the site's Bin folder - which can be discovered from the AppDomain.SetupInformation.PrivateBinPath property. So I now have working code for the most basic types of apps now (Sql Server-hosted AppDomains are another story since the filesystem is virtualised) - but I came across an interesting issue a couple of days ago where this code simply doesn't work: the nUnit test runner. This uses both Shadow Copying (so my algorithm would need to be discovering and loading them from the shadow-copy drop folder, not from the bin folder) and it sets up the PrivateBinPath as being relative to the base directory. And of course there are loads of other hosting scenarios that I probably haven't considered; but which must be valid because otherwise Fusion would choke on loading the assemblies. I want to stop feeling around and introducing hack upon hack to accommodate these new scenarios as they crop up - what I want is, given an AppDomain and its setup information, the ability to produce this list of Folders that I should scan in order to pick up all the DLLs that are going to be loaded; regardless of how the AppDomain is setup. If Fusion can see them as all the same, then so should my code. Of course, I might have to alter the algorithm if .Net changes its internals - that's just a cross I'll have to bear. Equally, I'm happy to consider SQL Server and any other similar environments as edge-cases that remain unsupported for now. Any ideas!?

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  • Clickonce downloading the deploy files via HTTP and not HTTPS

    - by Scott Manning
    I am working on a project to deploy a project via clickonce. The website where these files are housed will only accept HTTPS traffic and if you attempt to connect via HTTP, our siteminder agent will redirect you to a HTTPS login form. We cannot disable the siteminder agent or enable HTTP for security reasons. In the application file, I have a codebase that references an absolute path to the manifest and it is via HTTPS <dependency> <dependentAssembly dependencyType="install" codebase="https://psaportal.ilab.test.com/testprinting/Application_Files/testprint_1_0_0_1/testprint.exe.manifest" size="10147"> <assemblyIdentity name="testprint.exe" version="1.0.0.1" publicKeyToken="9a078649ee05e0e7" language="neutral" processorArchitecture="msil" type="win32" /> <hash> <dsig:Transforms> <dsig:Transform Algorithm="urn:schemas-microsoft-com:HashTransforms.Identity" /> </dsig:Transforms> <dsig:DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1" /> <dsig:DigestValue>2nch1T0SmlAycmePobtg9F1qF7c=</dsig:DigestValue> </hash> </dependentAssembly> </dependency> In running wireshark and decoding the SSL traffic (I am using the server’s private key in wireshark to decrypt the SSL traffic). I see the request to the application’s manifest file is via HTTPS (This is a good thing). But when the clickonce tries to download the testprint.exe.deploy and the other respective files, it is always via HTTP and the siteminder jumps in and redirects the requests which kills the clickonce install with errors. I have tried to specific an absolute codebase reference in the manifest file, but then I start getting entrypoint errors when the manifest is downloaded by the Clickonce installer. The current dependency section from the manifest file looks like the following: <dependency> <dependentAssembly dependencyType="install" allowDelayedBinding="true" codebase="testprint.exe" size="107008"> <assemblyIdentity name="testprint" version="1.0.0.1" language="neutral" processorArchitecture="msil" /> <hash> <dsig:Transforms> <dsig:Transform Algorithm="urn:schemas-microsoft-com:HashTransforms.Identity" /> </dsig:Transforms> <dsig:DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1" /> <dsig:DigestValue>dm2nJsu/5UyaEXSDmnISwfnE9MM=</dsig:DigestValue> </hash> </dependentAssembly> </dependency> I have verified that the website where the application, manifest and deploy files are all under the same URL and the SSL certificate is a valid certificate. We have tried about every combination of generating application and manifest files as we a dream up and are looking for other solutions. The application is using .NET 3.5 and we have tried building the application and manifest files via VS2008, VS2010 and mage with no success. Does anyone know how to get all of the deploy files to always download via HTTPS?

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  • use of tcp_delack_min on redhat linux (kernel 2.6.18)

    - by user41466
    Hello, we're moving from Solaris to Redhat Linux, and trying to duplicate our low-latency setup, that, on solaris, includes the ndd settings related to TCP NO DELAY, and NAGLE ALGORITHM. I got the impression that those parameters are not all configurable system-wide, but still found some info. we have configured our applications to run with no nagle algorithm, but that is not sufficient. we have found an interesting RH article talking presenting the tcp_delack_min parameter, however, when browsing /proc/sys/net/ipv4/ , I can't find it there. would it be safe to assume that simply "adding" the parameter as it's said on the doc would be enough, or rather that the option is not supported by this version (would be strange, as RH specify that it "can be performed on a standard Red Hat Enterprise Linux installation") ? any other idea / recommendation to improve latency further ? thanks

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  • Unable to find valid certification path to requested target while CAS authentication

    - by Dmitriy Sukharev
    I'm trying to configure CAS authentication. It requires both CAS and client application to use HTTPS protocol. Unfortunately we should use self-signed certificate (with CN that doesn't have anything in common with our server). Also the server is behind firewall and we have only two ports (ssh and https) visible. As far as there're several application that should be visible externally, we use Apache for ajp reverse proxying requests to these applications. Secure connections are managed by Apache, and all Tomcat are not configured to work with SSL. But I obtained exception while authentication, therefore desided to set keystore in CATALINA_OPTS: export CATALINA_OPTS="-Djavax.net.ssl.keyStore=/path/to/tomcat/ssl/cert.pfx -Djavax.net.ssl.keyStoreType=PKCS12 -Djavax.net.ssl.keyStorePassword=password -Djavax.net.ssl.keyAlias=alias -Djavax.net.debug=ssl" cert.pfx was obtained from certificate and key that are used by Apache HTTP Server: $ openssl pkcs12 -export -out /path/to/tomcat/ssl/cert.pfx -inkey /path/to/apache2/ssl/server-key.pem -in /path/to/apache2/ssl/server-cert.pem When I try to authenticate a user I obtain the following exception: Caused by: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target at sun.security.provider.certpath.SunCertPathBuilder.engineBuild(SunCertPathBuilder.java:174) ~[na:1.6.0_32] at java.security.cert.CertPathBuilder.build(CertPathBuilder.java:238) ~[na:1.6.0_32] at sun.security.validator.PKIXValidator.doBuild(PKIXValidator.java:318) ~[na:1.6.0_32] Meanwhile I can see in catalina.out that Tomcat see certificate in cert.pfx and it's the same as the one that is used while authentication: 09:11:38.886 [http-bio-8080-exec-2] DEBUG o.j.c.c.v.Cas20ProxyTicketValidator - Constructing validation url: https://external-ip/cas/proxyValidate?pgtUrl=https%3A%2F%2Fexternal-ip%2Fclient%2Fj_spring_cas_security_proxyreceptor&ticket=ST-17-PN26WtdsZqNmpUBS59RC-cas&service=https%3A%2F%2Fexternal-ip%2Fclient%2Fj_spring_cas_security_check 09:11:38.886 [http-bio-8080-exec-2] DEBUG o.j.c.c.v.Cas20ProxyTicketValidator - Retrieving response from server. keyStore is : /path/to/tomcat/ssl/cert.pfx keyStore type is : PKCS12 keyStore provider is : init keystore init keymanager of type SunX509 *** found key for : 1 chain [0] = [ [ Version: V1 Subject: CN=wrong.domain.name, O=Our organization, L=Location, ST=State, C=Country Signature Algorithm: SHA1withRSA, OID = 1.2.840.113549.1.1.5 Key: Sun RSA public key, 1024 bits modulus: 13??a lot of digits here??19 public exponent: ????7 Validity: [From: Tue Apr 24 16:32:18 CEST 2012, To: Wed Apr 24 16:32:18 CEST 2013] Issuer: CN=wrong.domain.name, O=Our organization, L=Location, ST=State, C=Country SerialNumber: [ d??????? ????????] ] Algorithm: [SHA1withRSA] Signature: 0000: 65 Signature is here 0070: 96 . ] *** trustStore is: /jdk-home-folder/jre/lib/security/cacerts Here is a lot of trusted CAs. Here is nothing related to our certicate or our (not trusted) CA. ... 09:11:39.731 [http-bio-8080-exec-4] DEBUG o.j.c.c.v.Cas20ProxyTicketValidator - Retrieving response from server. Allow unsafe renegotiation: false Allow legacy hello messages: true Is initial handshake: true Is secure renegotiation: false %% No cached client session *** ClientHello, TLSv1 RandomCookie: GMT: 1347433643 bytes = { 63, 239, 180, 32, 103, 140, 83, 7, 109, 149, 177, 80, 223, 79, 243, 244, 60, 191, 124, 139, 108, 5, 122, 238, 146, 1, 54, 218 } Session ID: {} Cipher Suites: [SSL_RSA_WITH_RC4_128_MD5, SSL_RSA_WITH_RC4_128_SHA, TLS_RSA_WITH_AES_128_CBC_SHA, TLS_DHE_RSA_WITH_AES_128_CBC_SHA, TLS_DHE_DSS_WITH_AES_128_CBC_SHA, SSL_RSA_WITH_3DES_EDE_CBC_SHA, SSL_DHE_RSA_WITH_3DES_EDE_CBC_SHA, SSL_DHE_DSS_WITH_3DES_EDE_CBC_SHA, SSL_RSA_WITH_DES_CBC_SHA, SSL_DHE_RSA_WITH_DES_CBC_SHA, SSL_DHE_DSS_WITH_DES_CBC_SHA, SSL_RSA_EXPORT_WITH_RC4_40_MD5, SSL_RSA_EXPORT_WITH_DES40_CBC_SHA, SSL_DHE_RSA_EXPORT_WITH_DES40_CBC_SHA, SSL_DHE_DSS_EXPORT_WITH_DES40_CBC_SHA, TLS_EMPTY_RENEGOTIATION_INFO_SCSV] Compression Methods: { 0 } *** http-bio-8080-exec-4, WRITE: TLSv1 Handshake, length = 75 http-bio-8080-exec-4, WRITE: SSLv2 client hello message, length = 101 http-bio-8080-exec-4, READ: TLSv1 Handshake, length = 81 *** ServerHello, TLSv1 RandomCookie: GMT: 1347433643 bytes = { 145, 237, 232, 63, 240, 104, 234, 201, 148, 235, 12, 222, 60, 75, 174, 0, 103, 38, 196, 181, 27, 226, 243, 61, 34, 7, 107, 72 } Session ID: {79, 202, 117, 79, 130, 216, 168, 38, 68, 29, 182, 82, 16, 25, 251, 66, 93, 108, 49, 133, 92, 108, 198, 23, 120, 120, 135, 151, 15, 13, 199, 87} Cipher Suite: SSL_RSA_WITH_RC4_128_SHA Compression Method: 0 Extension renegotiation_info, renegotiated_connection: <empty> *** %% Created: [Session-2, SSL_RSA_WITH_RC4_128_SHA] ** SSL_RSA_WITH_RC4_128_SHA http-bio-8080-exec-4, READ: TLSv1 Handshake, length = 609 *** Certificate chain chain [0] = [ [ Version: V1 Subject: CN=wrong.domain.name, O=Our organization, L=Location, ST=State, C=Country Signature Algorithm: SHA1withRSA, OID = 1.2.840.113549.1.1.5 Key: Sun RSA public key, 1024 bits modulus: 13??a lot of digits here??19 public exponent: ????7 Validity: [From: Tue Apr 24 16:32:18 CEST 2012, To: Wed Apr 24 16:32:18 CEST 2013] Issuer: CN=wrong.domain.name, O=Our organization, L=Location, ST=State, C=Country SerialNumber: [ d??????? ????????] ] Algorithm: [SHA1withRSA] Signature: 0000: 65 Signature is here 0070: 96 . ] *** http-bio-8080-exec-4, SEND TLSv1 ALERT: fatal, description = certificate_unknown http-bio-8080-exec-4, WRITE: TLSv1 Alert, length = 2 http-bio-8080-exec-4, called closeSocket() http-bio-8080-exec-4, handling exception: javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target I tried to convert our pem certificate to der format and imported it to trustedKeyStore (cacerts) (without private key), but it didn't change anything. But I'm not confident that I did it rigth. Also I must inform you that I don't know passphrase for our servier-key.pem file, and probably it differs from password for keystore created by me. OS: CentOS 6.2 Architecture: x64 Tomcat version: 7 Apache HTTP Server version: 2.4 Is there any way to make Tomcat accepts our certificate?

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  • How do I tell mdadm to start using a missing disk in my RAID5 array again?

    - by Jon Cage
    I have a 3-disk RAID array running in my Ubuntu server. This has been running flawlessly for over a year but I was recently forced to strip, move and rebuild the machine. When I had it all back together and ran up Ubuntu, I had some problems with disks not being detected. A couple of reboots later and I'd solved that issue. The problem now is that the 3-disk array is showing up as degraded every time I boot up. For some reason it seems that Ubuntu has made a new array and added the missing disk to it. I've tried stopping the new 1-disk array and adding the missing disk, but I'm struggling. On startup I get this: root@uberserver:~# cat /proc/mdstat Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] md_d1 : inactive sdf1[2](S) 1953511936 blocks md0 : active raid5 sdg1[2] sdc1[3] sdb1[1] sdh1[0] 2930279808 blocks level 5, 64k chunk, algorithm 2 [4/4] [UUUU] I have two RAID arrays and the one that normally pops up as md1 isn't appearing. I read somewhere that calling mdadm --assemble --scan would re-assemble the missing array so I've tried first stopping the existing array that ubuntu started: root@uberserver:~# mdadm --stop /dev/md_d1 mdadm: stopped /dev/md_d1 ...and then tried to tell ubuntu to pick the disks up again: root@uberserver:~# mdadm --assemble --scan mdadm: /dev/md/1 has been started with 2 drives (out of 3). So that's started md1 again but it's not picking up the disk from md_d1: root@uberserver:~# cat /proc/mdstat Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] md1 : active raid5 sde1[1] sdf1[2] 3907023872 blocks level 5, 64k chunk, algorithm 2 [3/2] [_UU] md_d1 : inactive sdd1[0](S) 1953511936 blocks md0 : active raid5 sdg1[2] sdc1[3] sdb1[1] sdh1[0] 2930279808 blocks level 5, 64k chunk, algorithm 2 [4/4] [UUUU] What's going wrong here? Why is Ubuntu trying to pick up sdd into a different array? How do I get that missing disk back home again? [Edit] - After adding the md1 to mdadm.conf it now tries to mount the array on startup but it's still missing the disk. If I tell it to try and assemble automatically I get the impression it know it needs sdd but can't use it: root@uberserver:~# mdadm --assemble --scan /dev/md1: File exists mdadm: /dev/md/1 already active, cannot restart it! mdadm: /dev/md/1 needed for /dev/sdd1... What am I missing?

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  • Help with refactoring PHP code

    - by Richard Knop
    I had some troubles implementing Lawler's algorithm but thanks to SO and a bounty of 200 reputation I finally managed to write a working implementation: http://stackoverflow.com/questions/2466928/lawlers-algorithm-implementation-assistance I feel like I'm using too many variables and loops there though so I am trying to refactor the code. It should be simpler and shorter yet remain readable. Does it make sense to make a class for this? Any advice or even help with refactoring this piece of code is welcomed: <?php /* * @name Lawler's algorithm PHP implementation * @desc This algorithm calculates an optimal schedule of jobs to be * processed on a single machine (in reversed order) while taking * into consideration any precedence constraints. * @author Richard Knop * */ $jobs = array(1 => array('processingTime' => 2, 'dueDate' => 3), 2 => array('processingTime' => 3, 'dueDate' => 15), 3 => array('processingTime' => 4, 'dueDate' => 9), 4 => array('processingTime' => 3, 'dueDate' => 16), 5 => array('processingTime' => 5, 'dueDate' => 12), 6 => array('processingTime' => 7, 'dueDate' => 20), 7 => array('processingTime' => 5, 'dueDate' => 27), 8 => array('processingTime' => 6, 'dueDate' => 40), 9 => array('processingTime' => 3, 'dueDate' => 10)); // precedence constrainst, i.e job 2 must be completed before job 5 etc $successors = array(2=>5, 7=>9); $n = count($jobs); $optimalSchedule = array(); for ($i = $n; $i >= 1; $i--) { // jobs not required to precede any other job $arr = array(); foreach ($jobs as $k => $v) { if (false === array_key_exists($k, $successors)) { $arr[] = $k; } } // calculate total processing time $totalProcessingTime = 0; foreach ($jobs as $k => $v) { if (true === array_key_exists($k, $arr)) { $totalProcessingTime += $v['processingTime']; } } // find the job that will go to the end of the optimal schedule array $min = null; $x = 0; $lastKey = null; foreach($arr as $k) { $x = $totalProcessingTime - $jobs[$k]['dueDate']; if (null === $min || $x < $min) { $min = $x; $lastKey = $k; } } // add the job to the optimal schedule array $optimalSchedule[$lastKey] = $jobs[$lastKey]; // remove job from the jobs array unset($jobs[$lastKey]); // remove precedence constraint from the successors array if needed if (true === in_array($lastKey, $successors)) { foreach ($successors as $k => $v) { if ($lastKey === $v) { unset($successors[$k]); } } } } // reverse the optimal schedule array and preserve keys $optimalSchedule = array_reverse($optimalSchedule, true); // add tardiness to the array $i = 0; foreach ($optimalSchedule as $k => $v) { $optimalSchedule[$k]['tardiness'] = 0; $j = 0; foreach ($optimalSchedule as $k2 => $v2) { if ($j <= $i) { $optimalSchedule[$k]['tardiness'] += $v2['processingTime']; } $j++; } $i++; } echo '<pre>'; print_r($optimalSchedule); echo '</pre>';

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  • Justification of Amazon EC2 Performance

    - by Adroidist
    I have a .jar file that represents a server which receives over TCP an image in bytes (of size at most 500 kb) and writes it file. It then sobels this image and sends it over TCP socket to the client side. I ran it on my laptop and it was very fast. But when I put it on Amazon EC2 server m1.large instance, i found out it is very slow - around 10 times slower. It might be the inefficiency in the code algorithm but in fact my code is nothing but receive image (like any byte file) run the sobel algorithm and send. I have the following questions: 1- Is it normal performance of Amazon EC2 server- I have read the following links link1 and link2 2- Even if the code is not that efficient, the server is finally handling a very low load (just one client), does the "inefficient" code justify such performance? 3- My laptop is dual core only...Why would the amazon ec2 server have worse performance that my laptop? How is this explained? Excuse me for my ignorance.

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  • Can I execute a "variable statements" within a function and without defines.

    - by René Nyffenegger
    I am facing a problem that I cannot see how it is solvable without #defines or incuring a performance impact although I am sure that someone can point me to a solution. I have an algorithm that sort of produces a (large) series of values. For simplicity's sake, in the following I pretend it's a for loop in a for loop, although in my code it's more complex than that. In the core of the loop I need to do calculations with the values being produced. Although the algorithm for the values stays the same, the calculations vary. So basically, what I have is: void normal() { // "Algorithm" producing numbers (x and y): for (int x=0 ; x<1000 ; x++) { for (int y=0 ; y<1000 ; y++) { // Calculation with numbers being produced: if ( x+y == 800 && y > 790) { std::cout << x << ", " << y << std::endl; } // end of calculation }} } So, the only part I need to change is if ( x+y == 800 && y > 790) { std::cout << x << ", " << y << std::endl; } So, in order to solve that, I could construct an abstract base class: class inner_0 { public: virtual void call(int x, int y) = 0; }; and derive a "callable" class from it: class inner : public inner_0 { public: virtual void call(int x, int y) { if ( x+y == 800 && y > 790) { std::cout << x << ", " << y << std::endl; } } }; I can then pass an instance of the class to the "algorithm" like so: void O(inner i) { for (int x=0 ; x<1000 ; x++) { for (int y=0 ; y<1000 ; y++) { i.call(x,y); }} } // somewhere else.... inner I; O(I); In my case, I incur a performance hit because there is an indirect call via virtual function table. So I was thinking about a way around it. It's possible with two #defines: #define OUTER \ for (int x=0 ; x<1000 ; x++) { \ for (int y=0 ; y<1000 ; y++) { \ INNER \ }} // later... #define INNER \ if (x + y == 800 && y > 790) \ std::cout << x << ", " << y << std::endl; OUTER While this certainly works, I am not 100% happy with it because I don't necessarly like #defines. So, my question: is there a better way for what I want to achieve?

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  • displaying python's autodoc to the user (python 3.3)

    - by Plotinus
    I'm writing a simple command line math game, and I'm using python's autodoc for my math algorithms to help me remember, for example, what a proth number is while i'm writing the algorithm, but later on I'll want to tell that information to the user as well, so they'll know what the answer was. So, for example I have: def is_proth(): """Proth numbers and numbers that fit the formula k×2^n + 1, where k are odd positive integers, and 2^n > k.""" [snip] return proths and then I tried to make a dictionary, like so: definitions = {"proths" : help(is_proth)} But it doesn't work. It prints this when I start the program, one for each item in the dictionary, and then it errors out on one of them that returns a set. And anyway, I don't want it displayed to the user until after they've played the game. Help on function is_proth in module __main__: is_proth() Proth numbers and numbers that fit the formula k×2^n + 1, where k are odd positive integers, and 2^n > k. (END) I understand the purpose of autodoc is more for helping programmers who are calling a function than for generating userdoc, but it seems inefficient to have to type out the definition of what a proth number is twice, once in a comment to help me remember what an algorithm does and then once to tell the user the answer to the game they were playing after they've won or lost.

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  • Parallelism in .NET – Part 4, Imperative Data Parallelism: Aggregation

    - by Reed
    In the article on simple data parallelism, I described how to perform an operation on an entire collection of elements in parallel.  Often, this is not adequate, as the parallel operation is going to be performing some form of aggregation. Simple examples of this might include taking the sum of the results of processing a function on each element in the collection, or finding the minimum of the collection given some criteria.  This can be done using the techniques described in simple data parallelism, however, special care needs to be taken into account to synchronize the shared data appropriately.  The Task Parallel Library has tools to assist in this synchronization. The main issue with aggregation when parallelizing a routine is that you need to handle synchronization of data.  Since multiple threads will need to write to a shared portion of data.  Suppose, for example, that we wanted to parallelize a simple loop that looked for the minimum value within a dataset: double min = double.MaxValue; foreach(var item in collection) { double value = item.PerformComputation(); min = System.Math.Min(min, value); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } This seems like a good candidate for parallelization, but there is a problem here.  If we just wrap this into a call to Parallel.ForEach, we’ll introduce a critical race condition, and get the wrong answer.  Let’s look at what happens here: // Buggy code! Do not use! double min = double.MaxValue; Parallel.ForEach(collection, item => { double value = item.PerformComputation(); min = System.Math.Min(min, value); }); This code has a fatal flaw: min will be checked, then set, by multiple threads simultaneously.  Two threads may perform the check at the same time, and set the wrong value for min.  Say we get a value of 1 in thread 1, and a value of 2 in thread 2, and these two elements are the first two to run.  If both hit the min check line at the same time, both will determine that min should change, to 1 and 2 respectively.  If element 1 happens to set the variable first, then element 2 sets the min variable, we’ll detect a min value of 2 instead of 1.  This can lead to wrong answers. Unfortunately, fixing this, with the Parallel.ForEach call we’re using, would require adding locking.  We would need to rewrite this like: // Safe, but slow double min = double.MaxValue; // Make a "lock" object object syncObject = new object(); Parallel.ForEach(collection, item => { double value = item.PerformComputation(); lock(syncObject) min = System.Math.Min(min, value); }); This will potentially add a huge amount of overhead to our calculation.  Since we can potentially block while waiting on the lock for every single iteration, we will most likely slow this down to where it is actually quite a bit slower than our serial implementation.  The problem is the lock statement – any time you use lock(object), you’re almost assuring reduced performance in a parallel situation.  This leads to two observations I’ll make: When parallelizing a routine, try to avoid locks. That being said: Always add any and all required synchronization to avoid race conditions. These two observations tend to be opposing forces – we often need to synchronize our algorithms, but we also want to avoid the synchronization when possible.  Looking at our routine, there is no way to directly avoid this lock, since each element is potentially being run on a separate thread, and this lock is necessary in order for our routine to function correctly every time. However, this isn’t the only way to design this routine to implement this algorithm.  Realize that, although our collection may have thousands or even millions of elements, we have a limited number of Processing Elements (PE).  Processing Element is the standard term for a hardware element which can process and execute instructions.  This typically is a core in your processor, but many modern systems have multiple hardware execution threads per core.  The Task Parallel Library will not execute the work for each item in the collection as a separate work item. Instead, when Parallel.ForEach executes, it will partition the collection into larger “chunks” which get processed on different threads via the ThreadPool.  This helps reduce the threading overhead, and help the overall speed.  In general, the Parallel class will only use one thread per PE in the system. Given the fact that there are typically fewer threads than work items, we can rethink our algorithm design.  We can parallelize our algorithm more effectively by approaching it differently.  Because the basic aggregation we are doing here (Min) is communitive, we do not need to perform this in a given order.  We knew this to be true already – otherwise, we wouldn’t have been able to parallelize this routine in the first place.  With this in mind, we can treat each thread’s work independently, allowing each thread to serially process many elements with no locking, then, after all the threads are complete, “merge” together the results. This can be accomplished via a different set of overloads in the Parallel class: Parallel.ForEach<TSource,TLocal>.  The idea behind these overloads is to allow each thread to begin by initializing some local state (TLocal).  The thread will then process an entire set of items in the source collection, providing that state to the delegate which processes an individual item.  Finally, at the end, a separate delegate is run which allows you to handle merging that local state into your final results. To rewriting our routine using Parallel.ForEach<TSource,TLocal>, we need to provide three delegates instead of one.  The most basic version of this function is declared as: public static ParallelLoopResult ForEach<TSource, TLocal>( IEnumerable<TSource> source, Func<TLocal> localInit, Func<TSource, ParallelLoopState, TLocal, TLocal> body, Action<TLocal> localFinally ) The first delegate (the localInit argument) is defined as Func<TLocal>.  This delegate initializes our local state.  It should return some object we can use to track the results of a single thread’s operations. The second delegate (the body argument) is where our main processing occurs, although now, instead of being an Action<T>, we actually provide a Func<TSource, ParallelLoopState, TLocal, TLocal> delegate.  This delegate will receive three arguments: our original element from the collection (TSource), a ParallelLoopState which we can use for early termination, and the instance of our local state we created (TLocal).  It should do whatever processing you wish to occur per element, then return the value of the local state after processing is completed. The third delegate (the localFinally argument) is defined as Action<TLocal>.  This delegate is passed our local state after it’s been processed by all of the elements this thread will handle.  This is where you can merge your final results together.  This may require synchronization, but now, instead of synchronizing once per element (potentially millions of times), you’ll only have to synchronize once per thread, which is an ideal situation. Now that I’ve explained how this works, lets look at the code: // Safe, and fast! double min = double.MaxValue; // Make a "lock" object object syncObject = new object(); Parallel.ForEach( collection, // First, we provide a local state initialization delegate. () => double.MaxValue, // Next, we supply the body, which takes the original item, loop state, // and local state, and returns a new local state (item, loopState, localState) => { double value = item.PerformComputation(); return System.Math.Min(localState, value); }, // Finally, we provide an Action<TLocal>, to "merge" results together localState => { // This requires locking, but it's only once per used thread lock(syncObj) min = System.Math.Min(min, localState); } ); Although this is a bit more complicated than the previous version, it is now both thread-safe, and has minimal locking.  This same approach can be used by Parallel.For, although now, it’s Parallel.For<TLocal>.  When working with Parallel.For<TLocal>, you use the same triplet of delegates, with the same purpose and results. Also, many times, you can completely avoid locking by using a method of the Interlocked class to perform the final aggregation in an atomic operation.  The MSDN example demonstrating this same technique using Parallel.For uses the Interlocked class instead of a lock, since they are doing a sum operation on a long variable, which is possible via Interlocked.Add. By taking advantage of local state, we can use the Parallel class methods to parallelize algorithms such as aggregation, which, at first, may seem like poor candidates for parallelization.  Doing so requires careful consideration, and often requires a slight redesign of the algorithm, but the performance gains can be significant if handled in a way to avoid excessive synchronization.

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  • A Nondeterministic Engine written in VB.NET 2010

    - by neil chen
    When I'm reading SICP (Structure and Interpretation of Computer Programs) recently, I'm very interested in the concept of an "Nondeterministic Algorithm". According to wikipedia:  In computer science, a nondeterministic algorithm is an algorithm with one or more choice points where multiple different continuations are possible, without any specification of which one will be taken. For example, here is an puzzle came from the SICP: Baker, Cooper, Fletcher, Miller, and Smith live on different floors of an apartment housethat contains only five floors. Baker does not live on the top floor. Cooper does not live onthe bottom floor. Fletcher does not live on either the top or the bottom floor. Miller lives ona higher floor than does Cooper. Smith does not live on a floor adjacent to Fletcher's.Fletcher does not live on a floor adjacent to Cooper's. Where does everyone live? After reading this I decided to build a simple nondeterministic calculation engine with .NET. The rough idea is that we can use an iterator to track each set of possible values of the parameters, and then we implement some logic inside the engine to automate the statemachine, so that we can try one combination of the values, then test it, and then move to the next. We also used a backtracking algorithm to go back when we are running out of choices at some point. Following is the core code of the engine itself: Code highlighting produced by Actipro CodeHighlighter (freeware)http://www.CodeHighlighter.com/--Public Class NonDeterministicEngine Private _paramDict As New List(Of Tuple(Of String, IEnumerator)) 'Private _predicateDict As New List(Of Tuple(Of Func(Of Object, Boolean), IEnumerable(Of String))) Private _predicateDict As New List(Of Tuple(Of Object, IList(Of String))) Public Sub AddParam(ByVal name As String, ByVal values As IEnumerable) _paramDict.Add(New Tuple(Of String, IEnumerator)(name, values.GetEnumerator())) End Sub Public Sub AddRequire(ByVal predicate As Func(Of Object, Boolean), ByVal paramNames As IList(Of String)) CheckParamCount(1, paramNames) _predicateDict.Add(New Tuple(Of Object, IList(Of String))(predicate, paramNames)) End Sub Public Sub AddRequire(ByVal predicate As Func(Of Object, Object, Boolean), ByVal paramNames As IList(Of String)) CheckParamCount(2, paramNames) _predicateDict.Add(New Tuple(Of Object, IList(Of String))(predicate, paramNames)) End Sub Public Sub AddRequire(ByVal predicate As Func(Of Object, Object, Object, Boolean), ByVal paramNames As IList(Of String)) CheckParamCount(3, paramNames) _predicateDict.Add(New Tuple(Of Object, IList(Of String))(predicate, paramNames)) End Sub Public Sub AddRequire(ByVal predicate As Func(Of Object, Object, Object, Object, Boolean), ByVal paramNames As IList(Of String)) CheckParamCount(4, paramNames) _predicateDict.Add(New Tuple(Of Object, IList(Of String))(predicate, paramNames)) End Sub Public Sub AddRequire(ByVal predicate As Func(Of Object, Object, Object, Object, Object, Boolean), ByVal paramNames As IList(Of String)) CheckParamCount(5, paramNames) _predicateDict.Add(New Tuple(Of Object, IList(Of String))(predicate, paramNames)) End Sub Public Sub AddRequire(ByVal predicate As Func(Of Object, Object, Object, Object, Object, Object, Boolean), ByVal paramNames As IList(Of String)) CheckParamCount(6, paramNames) _predicateDict.Add(New Tuple(Of Object, IList(Of String))(predicate, paramNames)) End Sub Public Sub AddRequire(ByVal predicate As Func(Of Object, Object, Object, Object, Object, Object, Object, Boolean), ByVal paramNames As IList(Of String)) CheckParamCount(7, paramNames) _predicateDict.Add(New Tuple(Of Object, IList(Of String))(predicate, paramNames)) End Sub Public Sub AddRequire(ByVal predicate As Func(Of Object, Object, Object, Object, Object, Object, Object, Object, Boolean), ByVal paramNames As IList(Of String)) CheckParamCount(8, paramNames) _predicateDict.Add(New Tuple(Of Object, IList(Of String))(predicate, paramNames)) End Sub Sub CheckParamCount(ByVal count As Integer, ByVal paramNames As IList(Of String)) If paramNames.Count <> count Then Throw New Exception("Parameter count does not match.") End If End Sub Public Property IterationOver As Boolean Private _firstTime As Boolean = True Public ReadOnly Property Current As Dictionary(Of String, Object) Get If IterationOver Then Return Nothing Else Dim _nextResult = New Dictionary(Of String, Object) For Each item In _paramDict Dim iter = item.Item2 _nextResult.Add(item.Item1, iter.Current) Next Return _nextResult End If End Get End Property Function MoveNext() As Boolean If IterationOver Then Return False End If If _firstTime Then For Each item In _paramDict Dim iter = item.Item2 iter.MoveNext() Next _firstTime = False Return True Else Dim canMoveNext = False Dim iterIndex = _paramDict.Count - 1 canMoveNext = _paramDict(iterIndex).Item2.MoveNext If canMoveNext Then Return True End If Do While Not canMoveNext iterIndex = iterIndex - 1 If iterIndex = -1 Then Return False IterationOver = True End If canMoveNext = _paramDict(iterIndex).Item2.MoveNext If canMoveNext Then For i = iterIndex + 1 To _paramDict.Count - 1 Dim iter = _paramDict(i).Item2 iter.Reset() iter.MoveNext() Next Return True End If Loop End If End Function Function GetNextResult() As Dictionary(Of String, Object) While MoveNext() Dim result = Current If Satisfy(result) Then Return result End If End While Return Nothing End Function Function Satisfy(ByVal result As Dictionary(Of String, Object)) As Boolean For Each item In _predicateDict Dim pred = item.Item1 Select Case item.Item2.Count Case 1 Dim p1 = DirectCast(pred, Func(Of Object, Boolean)) Dim v1 = result(item.Item2(0)) If Not p1(v1) Then Return False End If Case 2 Dim p2 = DirectCast(pred, Func(Of Object, Object, Boolean)) Dim v1 = result(item.Item2(0)) Dim v2 = result(item.Item2(1)) If Not p2(v1, v2) Then Return False End If Case 3 Dim p3 = DirectCast(pred, Func(Of Object, Object, Object, Boolean)) Dim v1 = result(item.Item2(0)) Dim v2 = result(item.Item2(1)) Dim v3 = result(item.Item2(2)) If Not p3(v1, v2, v3) Then Return False End If Case 4 Dim p4 = DirectCast(pred, Func(Of Object, Object, Object, Object, Boolean)) Dim v1 = result(item.Item2(0)) Dim v2 = result(item.Item2(1)) Dim v3 = result(item.Item2(2)) Dim v4 = result(item.Item2(3)) If Not p4(v1, v2, v3, v4) Then Return False End If Case 5 Dim p5 = DirectCast(pred, Func(Of Object, Object, Object, Object, Object, Boolean)) Dim v1 = result(item.Item2(0)) Dim v2 = result(item.Item2(1)) Dim v3 = result(item.Item2(2)) Dim v4 = result(item.Item2(3)) Dim v5 = result(item.Item2(4)) If Not p5(v1, v2, v3, v4, v5) Then Return False End If Case 6 Dim p6 = DirectCast(pred, Func(Of Object, Object, Object, Object, Object, Object, Boolean)) Dim v1 = result(item.Item2(0)) Dim v2 = result(item.Item2(1)) Dim v3 = result(item.Item2(2)) Dim v4 = result(item.Item2(3)) Dim v5 = result(item.Item2(4)) Dim v6 = result(item.Item2(5)) If Not p6(v1, v2, v3, v4, v5, v6) Then Return False End If Case 7 Dim p7 = DirectCast(pred, Func(Of Object, Object, Object, Object, Object, Object, Object, Boolean)) Dim v1 = result(item.Item2(0)) Dim v2 = result(item.Item2(1)) Dim v3 = result(item.Item2(2)) Dim v4 = result(item.Item2(3)) Dim v5 = result(item.Item2(4)) Dim v6 = result(item.Item2(5)) Dim v7 = result(item.Item2(6)) If Not p7(v1, v2, v3, v4, v5, v6, v7) Then Return False End If Case 8 Dim p8 = DirectCast(pred, Func(Of Object, Object, Object, Object, Object, Object, Object, Object, Boolean)) Dim v1 = result(item.Item2(0)) Dim v2 = result(item.Item2(1)) Dim v3 = result(item.Item2(2)) Dim v4 = result(item.Item2(3)) Dim v5 = result(item.Item2(4)) Dim v6 = result(item.Item2(5)) Dim v7 = result(item.Item2(6)) Dim v8 = result(item.Item2(7)) If Not p8(v1, v2, v3, v4, v5, v6, v7, v8) Then Return False End If Case Else Throw New NotSupportedException End Select Next Return True End FunctionEnd Class    And now we can use the engine to solve the problem we mentioned above:   Code highlighting produced by Actipro CodeHighlighter (freeware)http://www.CodeHighlighter.com/--Sub Test2() Dim engine = New NonDeterministicEngine() engine.AddParam("baker", {1, 2, 3, 4, 5}) engine.AddParam("cooper", {1, 2, 3, 4, 5}) engine.AddParam("fletcher", {1, 2, 3, 4, 5}) engine.AddParam("miller", {1, 2, 3, 4, 5}) engine.AddParam("smith", {1, 2, 3, 4, 5}) engine.AddRequire(Function(baker) As Boolean Return baker <> 5 End Function, {"baker"}) engine.AddRequire(Function(cooper) As Boolean Return cooper <> 1 End Function, {"cooper"}) engine.AddRequire(Function(fletcher) As Boolean Return fletcher <> 1 And fletcher <> 5 End Function, {"fletcher"}) engine.AddRequire(Function(miller, cooper) As Boolean 'Return miller = cooper + 1 Return miller > cooper End Function, {"miller", "cooper"}) engine.AddRequire(Function(smith, fletcher) As Boolean Return smith <> fletcher + 1 And smith <> fletcher - 1 End Function, {"smith", "fletcher"}) engine.AddRequire(Function(fletcher, cooper) As Boolean Return fletcher <> cooper + 1 And fletcher <> cooper - 1 End Function, {"fletcher", "cooper"}) engine.AddRequire(Function(a, b, c, d, e) As Boolean Return a <> b And a <> c And a <> d And a <> e And b <> c And b <> d And b <> e And c <> d And c <> e And d <> e End Function, {"baker", "cooper", "fletcher", "miller", "smith"}) Dim result = engine.GetNextResult() While Not result Is Nothing Console.WriteLine(String.Format("baker: {0}, cooper: {1}, fletcher: {2}, miller: {3}, smith: {4}", result("baker"), result("cooper"), result("fletcher"), result("miller"), result("smith"))) result = engine.GetNextResult() End While Console.WriteLine("Calculation ended.")End Sub   Also, this engine can solve the classic 8 queens puzzle and find out all 92 results for me.   Code highlighting produced by Actipro CodeHighlighter (freeware)http://www.CodeHighlighter.com/--Sub Test3() ' The 8-Queens problem. Dim engine = New NonDeterministicEngine() ' Let's assume that a - h represents the queens in row 1 to 8, then we just need to find out the column number for each of them. engine.AddParam("a", {1, 2, 3, 4, 5, 6, 7, 8}) engine.AddParam("b", {1, 2, 3, 4, 5, 6, 7, 8}) engine.AddParam("c", {1, 2, 3, 4, 5, 6, 7, 8}) engine.AddParam("d", {1, 2, 3, 4, 5, 6, 7, 8}) engine.AddParam("e", {1, 2, 3, 4, 5, 6, 7, 8}) engine.AddParam("f", {1, 2, 3, 4, 5, 6, 7, 8}) engine.AddParam("g", {1, 2, 3, 4, 5, 6, 7, 8}) engine.AddParam("h", {1, 2, 3, 4, 5, 6, 7, 8}) Dim NotInTheSameDiagonalLine = Function(cols As IList) As Boolean For i = 0 To cols.Count - 2 For j = i + 1 To cols.Count - 1 If j - i = Math.Abs(cols(j) - cols(i)) Then Return False End If Next Next Return True End Function engine.AddRequire(Function(a, b, c, d, e, f, g, h) As Boolean Return a <> b AndAlso a <> c AndAlso a <> d AndAlso a <> e AndAlso a <> f AndAlso a <> g AndAlso a <> h AndAlso b <> c AndAlso b <> d AndAlso b <> e AndAlso b <> f AndAlso b <> g AndAlso b <> h AndAlso c <> d AndAlso c <> e AndAlso c <> f AndAlso c <> g AndAlso c <> h AndAlso d <> e AndAlso d <> f AndAlso d <> g AndAlso d <> h AndAlso e <> f AndAlso e <> g AndAlso e <> h AndAlso f <> g AndAlso f <> h AndAlso g <> h AndAlso NotInTheSameDiagonalLine({a, b, c, d, e, f, g, h}) End Function, {"a", "b", "c", "d", "e", "f", "g", "h"}) Dim result = engine.GetNextResult() While Not result Is Nothing Console.WriteLine("(1,{0}), (2,{1}), (3,{2}), (4,{3}), (5,{4}), (6,{5}), (7,{6}), (8,{7})", result("a"), result("b"), result("c"), result("d"), result("e"), result("f"), result("g"), result("h")) result = engine.GetNextResult() End While Console.WriteLine("Calculation ended.")End Sub (Chinese version of the post: http://www.cnblogs.com/RChen/archive/2010/05/17/1737587.html) Cheers,  

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  • Manually writing a dx11 tessellation shader

    - by Tudor
    I am looking for resources on what are the steps of manually implementing tessellation (I'm using Unity cg). Today it seems that it is all the rage to hide most of the gpu code far away and use rather rigid simplifications such as unity's SURFace shaders. And it seems useless unless you're doing supeficial stuff. A little background: I have procedurally generated meshes (using marching cubes) which have quality normals but no UVs and no Tangents. I have successfully written a custom vertex and fragment shader to do triplanar texture and bumpmap projection as well as some custom stuff (custom lighting, procedurally warping the texture for variation etc). I am using the GPU Gems book as reference. Now I need to implement tessellation, but It seems I must calculate the tangents at runtime by swizzling normals (ctrl+f this in gems: <normal.z, normal.y, -normal.x>) before the tessellator gets them. And I also need to keep my custom vert+frag setup (with my custom parameters/textures being passed between them) - so apparently I cannot use surface shaders. Can anyone provide some guidence?

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  • Does a site's bounce rate influence Google rankings?

    - by Joel Spolsky
    Does Google consider bounce rate or something similar in ranking sites? Background: here at Stack Exchange we noticed that the latest Google algorithm changes resulted in about a 20% dip in traffic to Server Fault (and a much smaller dip in traffic to Super User). Stack Overflow traffic was not affected. There was an article on WebProNews which hypothesized that bounce rate might be a ranking signal in Google's latest Panda update. According to Google Analytics, these are our bounce rates over the last month: Site Bounce Rate Avg Time on Site ------------- ----------- ---------------- SuperUser 84.67% 01:16 ServerFault 83.76% 00:53 Stack Overflow 63.63% 04:12 Now, technically, Google has no way to know the bounce rate. If you go to Google, search for something, and click on the first result, Google can't tell the difference between: a user who turns off their computer a user who goes to a completely different web site a user who spends hours clicking around on the website they landed on What Google does know is how long it takes the user to come back to Google and do another search. According to the book In The Plex (page 47), Google distinguishes between what they call "short clicks" and "long clicks": A short click is a search where the user quickly comes back to Google and does another search. Google interprets this as a signal that the first search results were unsatisfactory. A long click is a search where the user doesn't search again for a long time. The book says that Google uses this information internally, to judge the quality of their own algorithms. It also said that short click data in which someone retypes a slight variation of the search is used to fuel the "Did you mean...?" spell checking algorithm. So, my hypothesis is that Google has recently decided to use long click rates as a signal of a high quality site. Does anyone have any evidence of this? Have you seen any high-bounce-rate sites which lost traffic (or vice-versa)?

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  • Need some advice regarding collision detection with the sprite changing its width and height

    - by Frank Scott
    So I'm messing around with collision detection in my tile-based game and everything works fine and dandy using this method. However, now I am trying to implement sprite sheets so my character can have a walking and jumping animation. For one, I'd like to to be able to have each frame of variable size, I think. I want collision detection to be accurate and during a jumping animation the sprite's height will be shorter (because of the calves meeting the hamstrings). Again, this also works fine at the moment. I can get the character to animate properly each frame and cycle through animations. The problems arise when the width and height of the character change. Often times its position will be corrected by the collision detection system and the character will be rubber-banded to random parts of the map or even go outside the map bounds. For some reason with the linked collision detection algorithm, when the width or height of the sprite is changed on the fly, the entire algorithm breaks down. The solution I found so far is to have a single width and height of the sprite that remains constant, and only adjust the source rectangle for drawing. However, I'm not sure exactly what to set as the sprite's constant bounding box because it varies so much with the different animations. So now I'm not sure what to do. I'm toying with the idea of pixel-perfect collision detection but I'm not sure if it would really be worth it. Does anyone know how Braid does their collision detection? My game is also a 2D sidescroller and I was quite impressed with how it was handled in that game. Thanks for reading.

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  • Textures on top of other textures when using VBOs

    - by GameDev-er
    I'm currently making a cube style game. With chunks being drawn with VBOs. I'd like to know if there is a way to create an overlay texture on top of the existing texture without the need to rebuild the VBO. This is required to show activity in a cube (think of Minecraft when destroying a block and the little cracks start spreading). I believe these are called "decals" but I've not found how to use them with VBOs. So how do I draw decals on OpenGL VBO drawn cubes?

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  • Optimizing Solaris 11 SHA-1 on Intel Processors

    - by danx
    SHA-1 is a "hash" or "digest" operation that produces a 160 bit (20 byte) checksum value on arbitrary data, such as a file. It is intended to uniquely identify text and to verify it hasn't been modified. Max Locktyukhin and others at Intel have improved the performance of the SHA-1 digest algorithm using multiple techniques. This code has been incorporated into Solaris 11 and is available in the Solaris Crypto Framework via the libmd(3LIB), the industry-standard libpkcs11(3LIB) library, and Solaris kernel module sha1. The optimized code is used automatically on systems with a x86 CPU supporting SSSE3 (Intel Supplemental SSSE3). Intel microprocessor architectures that support SSSE3 include Nehalem, Westmere, Sandy Bridge microprocessor families. Further optimizations are available for microprocessors that support AVX (such as Sandy Bridge). Although SHA-1 is considered obsolete because of weaknesses found in the SHA-1 algorithm—NIST recommends using at least SHA-256, SHA-1 is still widely used and will be with us for awhile more. Collisions (the same SHA-1 result for two different inputs) can be found with moderate effort. SHA-1 is used heavily though in SSL/TLS, for example. And SHA-1 is stronger than the older MD5 digest algorithm, another digest option defined in SSL/TLS. Optimizations Review SHA-1 operates by reading an arbitrary amount of data. The data is read in 512 bit (64 byte) blocks (the last block is padded in a specific way to ensure it's a full 64 bytes). Each 64 byte block has 80 "rounds" of calculations (consisting of a mixture of "ROTATE-LEFT", "AND", and "XOR") applied to the block. Each round produces a 32-bit intermediate result, called W[i]. Here's what each round operates: The first 16 rounds, rounds 0 to 15, read the 512 bit block 32 bits at-a-time. These 32 bits is used as input to the round. The remaining rounds, rounds 16 to 79, use the results from the previous rounds as input. Specifically for round i it XORs the results of rounds i-3, i-8, i-14, and i-16 and rotates the result left 1 bit. The remaining calculations for the round is a series of AND, XOR, and ROTATE-LEFT operators on the 32-bit input and some constants. The 32-bit result is saved as W[i] for round i. The 32-bit result of the final round, W[79], is the SHA-1 checksum. Optimization: Vectorization The first 16 rounds can be vectorized (computed in parallel) because they don't depend on the output of a previous round. As for the remaining rounds, because of step 2 above, computing round i depends on the results of round i-3, W[i-3], one can vectorize 3 rounds at-a-time. Max Locktyukhin found through simple factoring, explained in detail in his article referenced below, that the dependencies of round i on the results of rounds i-3, i-8, i-14, and i-16 can be replaced instead with dependencies on the results of rounds i-6, i-16, i-28, and i-32. That is, instead of initializing intermediate result W[i] with: W[i] = (W[i-3] XOR W[i-8] XOR W[i-14] XOR W[i-16]) ROTATE-LEFT 1 Initialize W[i] as follows: W[i] = (W[i-6] XOR W[i-16] XOR W[i-28] XOR W[i-32]) ROTATE-LEFT 2 That means that 6 rounds could be vectorized at once, with no additional calculations, instead of just 3! This optimization is independent of Intel or any other microprocessor architecture, although the microprocessor has to support vectorization to use it, and exploits one of the weaknesses of SHA-1. Optimization: SSSE3 Intel SSSE3 makes use of 16 %xmm registers, each 128 bits wide. The 4 32-bit inputs to a round, W[i-6], W[i-16], W[i-28], W[i-32], all fit in one %xmm register. The following code snippet, from Max Locktyukhin's article, converted to ATT assembly syntax, computes 4 rounds in parallel with just a dozen or so SSSE3 instructions: movdqa W_minus_04, W_TMP pxor W_minus_28, W // W equals W[i-32:i-29] before XOR // W = W[i-32:i-29] ^ W[i-28:i-25] palignr $8, W_minus_08, W_TMP // W_TMP = W[i-6:i-3], combined from // W[i-4:i-1] and W[i-8:i-5] vectors pxor W_minus_16, W // W = (W[i-32:i-29] ^ W[i-28:i-25]) ^ W[i-16:i-13] pxor W_TMP, W // W = (W[i-32:i-29] ^ W[i-28:i-25] ^ W[i-16:i-13]) ^ W[i-6:i-3]) movdqa W, W_TMP // 4 dwords in W are rotated left by 2 psrld $30, W // rotate left by 2 W = (W >> 30) | (W << 2) pslld $2, W_TMP por W, W_TMP movdqa W_TMP, W // four new W values W[i:i+3] are now calculated paddd (K_XMM), W_TMP // adding 4 current round's values of K movdqa W_TMP, (WK(i)) // storing for downstream GPR instructions to read A window of the 32 previous results, W[i-1] to W[i-32] is saved in memory on the stack. This is best illustrated with a chart. Without vectorization, computing the rounds is like this (each "R" represents 1 round of SHA-1 computation): RRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRR With vectorization, 4 rounds can be computed in parallel: RRRRRRRRRRRRRRRRRRRR RRRRRRRRRRRRRRRRRRRR RRRRRRRRRRRRRRRRRRRR RRRRRRRRRRRRRRRRRRRR Optimization: AVX The new "Sandy Bridge" microprocessor architecture, which supports AVX, allows another interesting optimization. SSSE3 instructions have two operands, a input and an output. AVX allows three operands, two inputs and an output. In many cases two SSSE3 instructions can be combined into one AVX instruction. The difference is best illustrated with an example. Consider these two instructions from the snippet above: pxor W_minus_16, W // W = (W[i-32:i-29] ^ W[i-28:i-25]) ^ W[i-16:i-13] pxor W_TMP, W // W = (W[i-32:i-29] ^ W[i-28:i-25] ^ W[i-16:i-13]) ^ W[i-6:i-3]) With AVX they can be combined in one instruction: vpxor W_minus_16, W, W_TMP // W = (W[i-32:i-29] ^ W[i-28:i-25] ^ W[i-16:i-13]) ^ W[i-6:i-3]) This optimization is also in Solaris, although Sandy Bridge-based systems aren't widely available yet. As an exercise for the reader, AVX also has 256-bit media registers, %ymm0 - %ymm15 (a superset of 128-bit %xmm0 - %xmm15). Can %ymm registers be used to parallelize the code even more? Optimization: Solaris-specific In addition to using the Intel code described above, I performed other minor optimizations to the Solaris SHA-1 code: Increased the digest(1) and mac(1) command's buffer size from 4K to 64K, as previously done for decrypt(1) and encrypt(1). This size is well suited for ZFS file systems, but helps for other file systems as well. Optimized encode functions, which byte swap the input and output data, to copy/byte-swap 4 or 8 bytes at-a-time instead of 1 byte-at-a-time. Enhanced the Solaris mdb(1) and kmdb(1) debuggers to display all 16 %xmm and %ymm registers (mdb "$x" command). Previously they only displayed the first 8 that are available in 32-bit mode. Can't optimize if you can't debug :-). Changed the SHA-1 code to allow processing in "chunks" greater than 2 Gigabytes (64-bits) Performance I measured performance on a Sun Ultra 27 (which has a Nehalem-class Xeon 5500 Intel W3570 microprocessor @3.2GHz). Turbo mode is disabled for consistent performance measurement. Graphs are better than words and numbers, so here they are: The first graph shows the Solaris digest(1) command before and after the optimizations discussed here, contained in libmd(3LIB). I ran the digest command on a half GByte file in swapfs (/tmp) and execution time decreased from 1.35 seconds to 0.98 seconds. The second graph shows the the results of an internal microbenchmark that uses the Solaris libpkcs11(3LIB) library. The operations are on a 128 byte buffer with 10,000 iterations. The results show operations increased from 320,000 to 416,000 operations per second. Finally the third graph shows the results of an internal kernel microbenchmark that uses the Solaris /kernel/crypto/amd64/sha1 module. The operations are on a 64Kbyte buffer with 100 iterations. third graph shows the results of an internal kernel microbenchmark that uses the Solaris /kernel/crypto/amd64/sha1 module. The operations are on a 64Kbyte buffer with 100 iterations. The results show for 1 kernel thread, operations increased from 410 to 600 MBytes/second. For 8 kernel threads, operations increase from 1540 to 1940 MBytes/second. Availability This code is in Solaris 11 FCS. It is available in the 64-bit libmd(3LIB) library for 64-bit programs and is in the Solaris kernel. You must be running hardware that supports Intel's SSSE3 instructions (for example, Intel Nehalem, Westmere, or Sandy Bridge microprocessor architectures). The easiest way to determine if SSSE3 is available is with the isainfo(1) command. For example, nehalem $ isainfo -v $ isainfo -v 64-bit amd64 applications sse4.2 sse4.1 ssse3 popcnt tscp ahf cx16 sse3 sse2 sse fxsr mmx cmov amd_sysc cx8 tsc fpu 32-bit i386 applications sse4.2 sse4.1 ssse3 popcnt tscp ahf cx16 sse3 sse2 sse fxsr mmx cmov sep cx8 tsc fpu If the output also shows "avx", the Solaris executes the even-more optimized 3-operand AVX instructions for SHA-1 mentioned above: sandybridge $ isainfo -v 64-bit amd64 applications avx xsave pclmulqdq aes sse4.2 sse4.1 ssse3 popcnt tscp ahf cx16 sse3 sse2 sse fxsr mmx cmov amd_sysc cx8 tsc fpu 32-bit i386 applications avx xsave pclmulqdq aes sse4.2 sse4.1 ssse3 popcnt tscp ahf cx16 sse3 sse2 sse fxsr mmx cmov sep cx8 tsc fpu No special configuration or setup is needed to take advantage of this code. Solaris libraries and kernel automatically determine if it's running on SSSE3 or AVX-capable machines and execute the correctly-tuned code for that microprocessor. Summary The Solaris 11 Crypto Framework, via the sha1 kernel module and libmd(3LIB) and libpkcs11(3LIB) libraries, incorporated a useful SHA-1 optimization from Intel for SSSE3-capable microprocessors. As with other Solaris optimizations, they come automatically "under the hood" with the current Solaris release. References "Improving the Performance of the Secure Hash Algorithm (SHA-1)" by Max Locktyukhin (Intel, March 2010). The source for these SHA-1 optimizations used in Solaris "SHA-1", Wikipedia Good overview of SHA-1 FIPS 180-1 SHA-1 standard (FIPS, 1995) NIST Comments on Cryptanalytic Attacks on SHA-1 (2005, revised 2006)

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  • What are the pros and cons of Coffeescript?

    - by Philip
    Of course one big pro is the amount of syntactic sugar leading to shorter code in a lot of cases. On http://jashkenas.github.com/coffee-script/ there are impressive examples. On the other hand I have doubts that these examples represent code of complex real world applications. In my code for instance I never add functions to bare objects but rather to their prototypes. Moreover the prototype feature is hidden from the user, suggesting classical OOP rather than idiomatic Javascript. The array comprehension example would look in my code probably like this: cubes = $.map(list, math.cube); // which is 8 characters less using jQuery...

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  • SQL SERVER – BI Quiz – Troubleshooting Cube Performance

    - by pinaldave
    My friend Jacob Sebastian runs SQL BI Quiz competition. Where there are 30 different questions on each day of the month. Winners get opportunity to participate in this Quiz, learn something new and win great awards. Working with huge data is very common when it is about Data Warehousing. It is necessary to create Cubes on the data to make it meaningful and consumable. There are cases when retrieving the data from cube takes lots of the time. Let us assume that your cube is returning you data very quickly. Suddenly on one day it is returning the data very slowly. What are the three things will you in order to diagnose this. After diagnose what you will do to resolve performance issue. Participate in my question over here Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Business Intelligence, Pinal Dave, PostADay, Readers Question, SQL, SQL Authority, SQL Performance, SQL Puzzle, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • IBM DB2 and the “'DbProviderFactories' section can only appear once per config” error

    - by Davide Mauri
    IBM doesn’t like MS. That’s a fact. And that’s why you can get your machine.config file (!!!) corrupted if you try to install IBM DB2 data providers on your server machine. If at some point, after having installed IBM DB2 data providers your SSIS packages or SSAS cubes or SSRS Reports starts to complain that 'DbProviderFactories' section can only appear once per config you may want to check into you machine.config, located in the %runtime install path%\Config http://msdn.microsoft.com/en-us/library/ms229697%28v=vs.71%29.aspx Almost surely you’ll find a IBM DB2 Provider into an additional DbProviderFactories section all alone. Poor guy. Remove the double DBProviderFactories entry, and merge everything inside only one section DBProviderFactories and after that everything will start to work again.

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  • Use depth bias for shadows in deferred shading

    - by cubrman
    We are building a deferred shading engine and we have a problem with shadows. To add shadows we use two maps: the first one stores the depth of the scene captured by the player's camera and the second one stores the depth of the scene captured by the light's camera. We then ran a shader that analyzes the two maps and outputs the third one with the ready shadow areas for the current frame. The problem we face is a classic one: Self-Shadowing: A standard way to solve this is to use the slope-scale depth bias and depth offsets, however as we are doing things in a deferred way we cannot employ this algorithm. Any attempts to set depth bias when capturing light's view depth produced no or unsatisfying results. So here is my question: MSDN article has a convoluted explanation of the slope-scale: bias = (m × SlopeScaleDepthBias) + DepthBias Where m is the maximum depth slope of the triangle being rendered, defined as: m = max( abs(delta z / delta x), abs(delta z / delta y) ) Could you explain how I can implement this algorithm manually in a shader? Maybe there are better ways to fix this problem for deferred shadows?

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  • Isometric drawing "Not Tile Stuff" on isometric map?

    - by Icebone1000
    So I got my isometric renderer working, it can draw diamond or jagged maps...Then I want to move on...How do I draw characters/objects on it in a optimal way? What Im doing now, as one can imagine, is traversing my grid(map) and drawing the tiles in a order so alpha blending works correctly. So, anything I draw in this map must be drawed at the same time the map is being drawn, with sucks a lot, screws your very modular map drawer, because now everything on the game (but the HUD) must be included on the drawer.. I was thinking whats the best approach to do this, comparing the position of all objects(not tile stuff) on the grid against the current tile being draw seems stupid, would it be better to add an id ON the grid(map)? this also seems terrible, because objects can move freely, not per tile steps (it can occupies 2 tiles if its between them, etc.) Dont know if matters, but my grid is 3D, so its not a plane with objects poping out, its a bunch of pilled cubes.

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  • I need help with 3d shading/lighting.

    - by Xavier
    How do you guys handle shading in a 3d game? I have a directional light source that shades one side of a tree made of cubes. The remaining 3 sides all get ambient shading only. So the 3d effect is lost when looking at two ambient shaded sides. Am I missing something? Should I be shading the side furthest from the light source even darker? I tried looking at Fallout 3 and it kinda looks like this is what they do however Minecraft appears to shade a grass mound with two opposite sides light and the remaining two opposite sides dark kinda giving the effect that there are two directional lights for the two light shaded sides and ambient light for the dark shaded sides.

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