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  • How to Make Objects Fall Faster in a Physics Simulation

    - by David Dimalanta
    I used the collision physics (i.e. Box2d, Physics Body Editor) and implemented onto the java code. I'm trying to make the fall speed higher according to the examples: It falls slower if light object (i.e. feather). It falls faster depending on the object (i.e. pebble, rock, car). I decided to double its falling speed for more excitement. I tried adding the mass but the speed of falling is constant instead of gaining more speed. check my code that something I put under input processor's touchUp() return method under same roof of the class that implements InputProcessor and Screen: @Override public boolean touchUp(int screenX, int screenY, int pointer, int button) { // TODO Touch Up Event if(is_Next_Fruit_Touched) { BodyEditorLoader Fruit_Loader = new BodyEditorLoader(Gdx.files.internal("Shape_Physics/Fruity Physics.json")); Fruit_BD.type = BodyType.DynamicBody; Fruit_BD.position.set(x, y); FixtureDef Fruit_FD = new FixtureDef(); // --> Allows you to make the object's physics. Fruit_FD.density = 1.0f; Fruit_FD.friction = 0.7f; Fruit_FD.restitution = 0.2f; MassData mass = new MassData(); mass.mass = 5f; Fruit_Body[n] = world.createBody(Fruit_BD); Fruit_Body[n].setActive(true); // --> Let your dragon fall. Fruit_Body[n].setMassData(mass); Fruit_Body[n].setGravityScale(1.0f); System.out.println("Eggs... " + n); Fruit_Loader.attachFixture(Fruit_Body[n], Body, Fruit_FD, Fruit_IMG.getWidth()); Fruit_Origin = Fruit_Loader.getOrigin(Body, Fruit_IMG.getWidth()).cpy(); is_Next_Fruit_Touched = false; up = y; Gdx.app.log("Initial Y-coordinate", "Y at " + up); //Once it's touched, the next fruit will set to drag. if(n < 50) { n++; }else{ System.exit(0); } } return true; } And take note, at show() method , the view size from the camera is at 720x1280: camera_1 = new OrthographicCamera(); camera_1.viewportHeight = 1280; camera_1.viewportWidth = 720; camera_1.position.set(camera_1.viewportWidth * 0.5f, camera_1.viewportHeight * 0.5f, 0f); camera_1.update(); I know it's a good idea to add weight to make the falling object falls faster once I released the finger from the touchUp() after I picked the object from the upper right of the screen but the speed remains either constant or slow. How can I solve this? Can you help?

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  • Multi Pass Blend

    - by Kirk Patrick
    I am seeking the simplest working example of a two pass HLSL pixel shader. It can do anything really, but the main idea is to perform "ping ponging" to take the output of the first pass and then send it for the second pass. In my example I want to draw to the R channel and then draw to the G channel and produce a simple Venn Diagram in the shader, but need to detect overlap. I can currently detect one or the other but not overlap. There are a red and green circle overlapping, and I want to put a dynamic texture map in the overlap region. I can currently put it in either or. Below is how it looks in the shader. -------------------------------- Texture2D shaderTexture; SamplerState SampleType; ////////////// // TYPEDEFS // ////////////// struct PixelInputType { float4 position : SV_POSITION; float2 tex0 : TEXCOORD0; float2 tex1 : TEXCOORD1; float4 color : COLOR; }; //////////////////////////////////////////////////////////////////////////////// // Pixel Shader //////////////////////////////////////////////////////////////////////////////// float4 main(PixelInputType input) : SV_TARGET { float4 textureColor0; float4 textureColor1; // Sample the pixel color from the texture using the sampler at this texture coordinate location. textureColor0 = shaderTexture.Sample(SampleType, input.tex0); textureColor1 = shaderTexture.Sample(SampleType, input.tex1); if (input.color[0]==1.0f && input.color[1]==1.0f) // Requires multi-pass textureColor0 = textureColor1; return textureColor0; } Here is the calling code (that needs to be modified) m_d3dContext->IASetVertexBuffers(0, 2, vbs, strides, offsets); m_d3dContext->IASetIndexBuffer(m_indexBuffer.Get(), DXGI_FORMAT_R32_UINT,0); m_d3dContext->IASetPrimitiveTopology(D3D11_PRIMITIVE_TOPOLOGY_TRIANGLELIST); m_d3dContext->IASetInputLayout(m_inputLayout.Get()); m_d3dContext->VSSetShader(m_vertexShader.Get(), nullptr, 0); m_d3dContext->VSSetConstantBuffers(0, 1, m_constantBuffer.GetAddressOf()); m_d3dContext->PSSetShader(m_pixelShader.Get(), nullptr, 0); m_d3dContext->PSSetShaderResources(0, 1, m_SRV.GetAddressOf()); m_d3dContext->PSSetSamplers(0, 1, m_QuadsTexSamplerState.GetAddressOf());

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  • 12.04 boots fine, with graphical splash screen, but then Monitor "out of range"

    - by Jim Bednar
    I see dozens of posts from people whose monitors are saying "out of range" under Ubuntu; seems like there are some serious problems in Ubuntu with autodetection of monitor capabilities. :-( But none of the many, many suggestions I found have solved my problem, and right now I can't use anything graphical on this machine! History: I installed Ubuntu 12.04 on my HP Proliant Microserver N40L, which worked reasonably at the default resolution across several reboots. At some point I noticed that the proprietary video driver was not in use, and tried to install one to get better window-drawing speeds, but it failed with some sort of error, and I gave up on that. A few weeks later when I next rebooted, it showed the usual BIOS screen and various boot loading screens (including GRUB), and then the usual purple Ubuntu splash screen with the dots showing that things were loading, but when it finished booting the monitor went black and eventually showed "Out of range" (with no other information). Given that there were several weeks between reboots (it's a server, after all), I've no idea if it was some system update, trying to install the proprietary drivers, or something else that caused the problem. Anyway, the system has booted fine, as I can do Ctrl-Alt-F1 to get a text prompt and can log in there. But Ctrl-Alt-F7 goes back to the out of range error. Some posters said to try Ctrl-Alt-- (minus) to cycle through resolutions until one works, but that didn't have any visible effect. Many, many others said it was a grub problem, which seems unlikely given that grub's screen looks fine, but I tried editing /etc/default/grub to set a particular resolution (trying many of them) and running update-grub, with no apparent effect. Rebooting into failsafe mode works the same as regular mode. Replacing xorg.conf with xorg.conf.failsafe works the same too. I'm at my wits' end! Isn't there anything I can do to convince Ubuntu to choose a mode that the monitor supports? E.g. the one that it is using for the splash screen? I don't need great resolution on this machine, just anything that works!!!!! Help!!!!!! Please!!!!

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  • 3D terrain map with Hexagon Grids (XNA)

    - by Rob
    I'm working on a hobby project (I'm a web/backend developer by day) and I want to create a 3D Tile (terrain) engine. I'm using XNA, but I can use MonoGame, OpenGL, or straight DirectX, so the answer does not have to be XNA specific. I'm more looking for some high level advice on how to approach this problem. I know about creating height maps and such, there are thousands of references out there on the net for that, this is a bit more specific. I'm more concerned with is the approach to get a 3D hexagon tile grid out of my terrain (since the terrain, and all 3d objects, are basically triangles). The first approach I thought about is to basically draw the triangles on the screen in the following order (blue numbers) to give me the triangles for terrain (black triangles) and then make hexes out of the triangles (red hex). http://screencast.com/t/ebrH2g5V This approach seems complicated to me since i'm basically having to draw 4 different types of triangles. The next approach I thought of was to use the existing triangles like I did for a square grid and get my hexes from 6 triangles as follows http://screencast.com/t/w9b7qKzVJtb8 This seems like the easier approach to me since there are only 2 types of triangles (i would have to play with the heights and widths to get a "perfect" hexagon, but the idea is the same. So I'm looking for: 1) Any suggestions on which approach I should take, and why. 2) How would I translate mouse position to a hexagon grid position (especially when moving the camera around), for example in the second image if the mouse pointer were the green circle, how would I determine to highlight that hexagon and then translating that into grid coordinates (assuming it is 0,0)? 3) Any references, articles, books, etc - to get me going in the right direction. Note: I've done hex grid's and mouse-grid coordinate conversion before in 2d. looking for some pointers on how to do the same in 3d. The result I would like to achieve is something similar to the following: http :// www. youtube .com / watch?v=Ri92YkyC3fw (sorry about the youtube link, but it will only let me post 2 links in this post... same rep problem i mention below...) Thanks for any help! P.S. Sorry for not posting the images inline, I apparently don't have enough rep on this stack exchange site.

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  • Euler angles to Cartesian Coordinates for use with gluLookAt

    - by notrodash
    I have searched all of the internet but just couldn't find the answer. I am using LibGDX and this is part of my code that loops over and over: public void render() { GL11 gl = Gdx.gl11; float centerX = (float)Math.cos(yaw) * (float)Math.cos(pitch); float centerY = (float)Math.sin(yaw) * (float)Math.cos(pitch); float centerZ = (float)Math.sin(pitch); System.out.println(centerX+" "+centerY+" "+centerZ+" ~ "+GDXRacing.camera.position.x+" "+GDXRacing.camera.position.y+" "+GDXRacing.camera.position.z); Gdx.glu.gluLookAt(gl, GDXRacing.camera.position.x, GDXRacing.camera.position.y, GDXRacing.camera.position.z, centerX, centerY, centerZ, 0, 1, 0); if(Gdx.input.isKeyPressed(Keys.A)) { yaw--; } if(Gdx.input.isKeyPressed(Keys.D)) { yaw++; } } I might just be bad at the math, but I dont get it. Does someone have a good explanation and an idea about how to deal with this? I am trying to make a first person camera. By the way, the camera is translated by +10 on the Z axis. Currently when I run the application, this is what I get: Watch video in browser | Download video (for those who cant download the video, everything shakes in a clockwise/anticlockwise action, depending on if I increase or decrease the Yaw value) -Thank you. [edit] and with this code: public void render() { GL11 gl = Gdx.gl11; float centerX = (float)(MathUtils.cosDeg(yaw)*4); float centerY = 0; float centerZ = (float)(MathUtils.sinDeg(yaw)*4); System.out.println(centerX+" "+centerY+" "+centerZ+" ~ "+GDXRacing.camera.position.x+" "+GDXRacing.camera.position.y+" "+GDXRacing.camera.position.z); Gdx.glu.gluLookAt(gl, GDXRacing.camera.position.x, GDXRacing.camera.position.y, GDXRacing.camera.position.z, centerX, centerY, centerZ, 0, 1, 0); if(Gdx.input.isKeyPressed(Keys.A)) { yaw--; } if(Gdx.input.isKeyPressed(Keys.D)) { yaw++; } } it slowly swings from the left to the right. This approach worked for turning left and right for 2d games though. What am I doing wrong?

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  • Perl syntax error [closed]

    - by Linny
    I am a beginner taking a Perl programming course. We are trying to write a basic program for counting nucleotides in a DNA string. I'm getting syntax errors on the lines that have a single bracket on lines 28 & 70 and don't know why. It also reads that I have compilation errors. I have no idea where to start figuring that out. # The purpose of this program is to count the number of nucleotides in a strand. Each protein is counted separately # print "/n NOTE: Nucleotide counting /n"; # use strict; # enforce variable declarations use warnings; # enable compiler warnings # Display number of A,a,T,t,G,g,C,c, nucleotides in a word or sequence of letters. # my ($base) = ''; # an extracted letter from a string my ($nuceotide_count) = 0 ; # the current position within the word my ($position) = 0 ; # number of vowels in user-supplied word my ($word) = ''; # word to be processed my ($A_count) = 0 ; # of A nucleotides in the user-supplied sequence my ($a_count) = 0 ; # of A nucleotides in the user-supplied sequence my ($C_count) = 0 ; # of C nucleotides in the user-supplied sequence my ($c_count) = 0 ; # of C nucleotides in the user-supplied sequence my ($G_count) = 0 ; # of G nucleotides in the user-supplied sequence my ($g_count) = 0 ; # of G nucleotides in the user-supplied sequence my ($T_count) = 0 ; # of T nucleotides in the user-supplied sequence my ($t_count) = 0 ; # of T nucleotides in the user-supplied sequence word = (STDIN) for ($position = 0);($position if (($base eq 'a') or ($base eq 'A')) { ++$A_count; } # end if ++$position; if (($base eq 'T') or ($base eq 't')) { ++$T_count; } end if ++$position; if (($base eq 'G') or ($base eq 'g')) { ++$G_count; } # end if ++$position; if (($base eq 'C') or ($base eq 'c')) { ++$C_count; } # end if ++$position; } # end for # Display final results. # print " \n The number of A or a neucleotides is: $A_count"; print " \n The number of T or t neucleotides is: $T_count"; print " \n The number of G or g neucleotides is: $G_count"; print " \n The number of C or c neucleotides is: $C_count"; print " \n\n Program completed successfully. \n" ; exit ;

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  • In an Entity-Component-System Engine, How do I deal with groups of dependent entities?

    - by John Daniels
    After going over a few game design patterns, I have settle with Entity-Component-System (ES System) for my game engine. I've reading articles (mainly T=Machine) and review some source code and I think I got enough to get started. There is just one basic idea I am struggling with. How do I deal with groups of entities that are dependent on each other? Let me use an example: Assume I am making a standard overhead shooter (think Jamestown) and I want to construct a "boss entity" with multiple distinct but connected parts. The break down might look like something like this: Ship body: Movement, Rendering Cannon: Position (locked relative to the Ship body), Tracking\Fire at hero, Taking Damage until disabled Core: Position (locked relative to the Ship body), Tracking\Fire at hero, Taking Damage until disabled, Disabling (er...destroying) all other entities in the ship group My goal would be something that would be identified (and manipulated) as a distinct game element without having to rewrite subsystem form the ground up every time I want to build a new aggregate Element. How do I implement this kind of design in ES System? Do I implement some kind of parent-child entity relationship (entities can have children)? This seems to contradict the methodology that Entities are just empty container and makes it feel more OOP. Do I implement them as separate entities, with some kind of connecting Component (BossComponent) and related system (BossSubSystem)? I can't help but think that this will be hard to implement since how components communicate seem to be a big bear trap. Do I implement them as one Entity, with a collection of components (ShipComponent, CannonComponents, CoreComponent)? This one seems to veer way of the ES System intent (components here seem too much like heavy weight entities), but I'm know to this so I figured I would put that out there. Do I implement them as something else I have mentioned? I know that this can be implemented very easily in OOP, but my choosing ES over OOP is one that I will stick with. If I need to break with pure ES theory to implement this design I will (not like I haven't had to compromise pure design before), but I would prefer to do that for performance reason rather than start with bad design. For extra credit, think of the same design but, each of the "boss entities" were actually connected to a larger "BigBoss entity" made of a main body, main core and 3 "Boss Entities". This would let me see a solution for at least 3 dimensions (grandparent-parent-child)...which should be more than enough for me. Links to articles or example code would be appreciated. Thanks for your time.

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  • glGetActiveAttrib on Android NDK

    - by user408952
    In my code-base I need to link the vertex declarations from a mesh to the attributes of a shader. To do this I retrieve all the attribute names after linking the shader. I use the following code (with some added debug info since it's not really working): int shaders[] = { m_ps, m_vs }; if(linkProgram(shaders, 2)) { ASSERT(glIsProgram(m_program) == GL_TRUE, "program is invalid"); int attrCount = 0; GL_CHECKED(glGetProgramiv(m_program, GL_ACTIVE_ATTRIBUTES, &attrCount)); int maxAttrLength = 0; GL_CHECKED(glGetProgramiv(m_program, GL_ACTIVE_ATTRIBUTE_MAX_LENGTH, &maxAttrLength)); LOG_INFO("shader", "got %d attributes for '%s' (%d) (maxlen: %d)", attrCount, name, m_program, maxAttrLength); m_attrs.reserve(attrCount); GLsizei attrLength = -1; GLint attrSize = -1; GLenum attrType = 0; char tmp[256]; for(int i = 0; i < attrCount; i++) { tmp[0] = 0; GL_CHECKED(glGetActiveAttrib(m_program, GLuint(i), sizeof(tmp), &attrLength, &attrSize, &attrType, tmp)); LOG_INFO("shader", "%d: %d %d '%s'", i, attrLength, attrSize, tmp); m_attrs.append(String(tmp, attrLength)); } } GL_CHECKED is a macro that calls the function and calls glGetError() to see if something went wrong. This code works perfectly on Windows 7 using ANGLE and gives this this output: info:shader: got 2 attributes for 'static/simplecolor.glsl' (3) (maxlen: 11) info:shader: 0: 7 1 'a_Color' info:shader: 1: 10 1 'a_Position' But on my Nexus 7 (1st gen) I get the following (the errors are the output from the GL_CHECKED macro): I/testgame:shader(30865): got 2 attributes for 'static/simplecolor.glsl' (3) (maxlen: 11) E/testgame:gl(30865): 'glGetActiveAttrib(m_program, GLuint(i), sizeof(tmp), &attrLength, &attrSize, &attrType, tmp)' failed: INVALID_VALUE [jni/src/../../../../src/Game/Asset/ShaderAsset.cpp:50] I/testgame:shader(30865): 0: -1 -1 '' E/testgame:gl(30865): 'glGetActiveAttrib(m_program, GLuint(i), sizeof(tmp), &attrLength, &attrSize, &attrType, tmp)' failed: INVALID_VALUE [jni/src/../../../../src/Game/Asset/ShaderAsset.cpp:50] I/testgame:shader(30865): 1: -1 -1 '' I.e. the call to glGetActiveAttrib gives me an INVALID_VALUE. The opengl docs says this about the possible errors: GL_INVALID_VALUE is generated if program is not a value generated by OpenGL. This is not the case, I added an ASSERT to make sure glIsProgram(m_program) == GL_TRUE, and it doesn't trigger. GL_INVALID_OPERATION is generated if program is not a program object. Different error. GL_INVALID_VALUE is generated if index is greater than or equal to the number of active attribute variables in program. i is 0 and 1, and the number of active attribute variables are 2, so this isn't the case. GL_INVALID_VALUE is generated if bufSize is less than 0. Well, it's not zero, it's 256. Does anyone have an idea what's causing this? Am I just lucky that it works in ANGLE, or is the nvidia tegra driver wrong?

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  • Ubuntu won't connect to wired network

    - by djeikyb
    I'm running 10.04, upgraded from 9.10, maybe, but probably not upgraded from 9.04. I have two wifi routers. Zeus is connected to the dsl modem. Hermes uses a wds bridge with Zeus to extend the network. My desktop (Daedalus) is ethernetted to Hermes. My laptop (Clyde) is wifi, switching to Hermes or Zeus as needed. Occasionally, as in whenever I transfer a large file from desktop to laptop, the wds bridge will die. Fixing it means restarting both routers, though it seems Hermes should boot first. This is ridiculous, and eventually I'll get around to asking you guys to help me stop it from happening. More importantly is that my desktop requires a reboot to get back on the network. WTF. ifconfig shows my nic has no ip. /etc/init.d/networking restart doesn't do anything, not even give me a lousy ip. dhcpcd eth1 grants me an ip address, but doesn't help with internet access. route -n shows what looks like my normal routing table, but pinging google.com informs me it's an unknown host. jake@daedalus:~$ route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 10.1.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1 169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth1 0.0.0.0 10.1.1.1 0.0.0.0 UG 0 0 0 eth1 It may be worth noting that I can ping both Zeus (10.1.1.1) and Hermes (10.1.1.4) and my laptop (10.1.1.55). Much obliged for any help. Rebooting is, well, trivial in this instance. But it's stupid. I switched to linux because I like the idea that if one part breaks, you fix it instead of reboot reboot reboot. I've left my poor desktop in disarray, confining myself to my little netbook. My desktop is broken, awaiting magical commands from you brilliant folk. (and yes, i know clyde the netbook should be named icarus. it was its original name. ironically the ssd burned out, and i felt it wasn't right when it came to reinstalling)

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  • Oracle GoldenGate: Knowledge Document Series Post #2

    - by Doug Reid
    0 false 18 pt 18 pt 0 0 false false false /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-ascii-font-family:Cambria; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Cambria; mso-hansi-theme-font:minor-latin;} 0 false 18 pt 18 pt 0 0 false false false /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-ascii-font-family:Cambria; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Cambria; mso-hansi-theme-font:minor-latin;} For our second post in this series the team would like to highlight the knowledge document “How-To: Oracle GoldenGate – Heartbeat Process to Monitor Lag and Performance”. This knowledge document outlines a procedure to reliably measure lag between source and target systems through the use of 'heartbeat' tables. The basic idea is to have a table on the source system that gets updated at a predetermined interval. In your capture processes you would capture the update from the heartbeat table. Using tokens you would add some additional information to the heartbeat record to be able to tell which extract process was capturing the update. This additional information would be used downstream to calculate the real lag time between the source and target systems for a given extract and by checking the last update time on the heartbeat at the target you could also determine if data has stopped flowing between the source and target.  Click here to view the document

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  • Have you used the ExecutionValue and ExecValueVariable properties?

    The ExecutionValue execution value property and it’s friend ExecValueVariable are a much undervalued feature of SSIS, and many people I talk to are not even aware of their existence, so I thought I’d try and raise their profile a bit. The ExecutionValue property is defined on the base object Task, so all tasks have it available, but it is up to the task developer to do something useful with it. The basic idea behind it is that it allows the task to return something useful and interesting about what it has performed, in addition to the standard success or failure result. The best example perhaps is the Execute SQL Task which uses the ExecutionValue property to return the number of rows affected by the SQL statement(s). This is a very useful feature, something people often want to capture into a variable, and start using the result set options to do. Unfortunately we cannot read the value of a task property at runtime from within a SSIS package, so the ExecutionValue property on its own is a bit of a let down, but enter the ExecValueVariable and we have the perfect marriage. The ExecValueVariable is another property exposed through the task (TaskHost), which lets us select a SSIS package variable. What happens now is that when the task sets the ExecutionValue, the interesting value is copied into the variable we set on the ExecValueVariable property, and a variable is something we can access and do something with. So put simply if the ExecutionValue property value is of interest, make sure you create yourself a package variable and set the name as the ExecValueVariable. Have  look at the 3 step guide below: 1 Configure your task as normal, for example the Execute SQL Task, which here calls a stored procedure to do some updates. 2 Create variable of a suitable type to match the ExecutionValue, an integer is used to match the result we want to capture, the number of rows. 3 Set the ExecValueVariable for the task, just select the variable we created in step 2. You need to do this in Properties grid for the task (Short-cut key, select the task and press F4) Now when we execute the sample task above, our variable UpdateQueueRowCount will get the number of rows we updated in our Execute SQL Task. I’ve tried to collate a list of tasks that return something useful via the ExecutionValue and ExecValueVariable mechanism, but the documentation isn’t always great. Task ExecutionValue Description Execute SQL Task Returns the number of rows affected by the SQL statement or statements. File System Task Returns the number of successful operations performed by the task. File Watcher Task Returns the full path of the file found Transfer Error Messages Task Returns the number of error messages that have been transferred Transfer Jobs Task Returns the number of jobs that are transferred Transfer Logins Task Returns the number of logins transferred Transfer Master Stored Procedures Task Returns the number of stored procedures transferred Transfer SQL Server Objects Task Returns the number of objects transferred WMI Data Reader Task Returns an object that contains the results of the task. Not exactly clear, but I assume it depends on the WMI query used.

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  • Walmart's Mobile Self-Checkout

    - by David Dorf
    Reuters recently reported that Walmart was testing an iPhone-based self-checkout at a store near its headquarters.  Consumers scan items as they're placed in the physical basket, then the virtual basket is transferred to an existing self-checkout station where payment is tendered.  A very solid solution, but not exactly original. Before we go further, let's look at the possible cost savings for Walmart.  According to the article: Pushing more shoppers to scan their own items and make payments without the help of a cashier could save Wal-Mart millions of dollars, Chief Financial Officer Charles Holley said on March 7. The company spends about $12 million in cashier wages every second at its Walmart U.S. stores. Um, yeah. Using back-of-the-napkin math, I calculated Walmart's cashiers are making $157k per hour.  A more accurate statement would be saving $12M per year for each second saved on the average transaction time.  So if this self-checkout approach saves 2 seconds per transaction on average, Walmart would save $24M per year on labor.  Maybe.  Sometimes that savings will be used to do other tasks in the store, so it may not directly translate to less employees. When I saw this approach demonstrated in Sweden, there were a few differences, which may or may not be in Walmart's plans.  First, the consumers were identified based on their loyalty card.  In order to offset the inevitable shrink, retailers need to save on labor but also increase basket size, typically via in-aisle promotions.  As they scan items, retailers should target promos, and that's easier to do if you know some shopping history.  Last I checked, Walmart had no loyalty program. Second, at the self-checkout station consumers were randomly selected for an audit in which they must re-scan all the items just like you do at a typical self-checkout.  If you were found to be stealing, your ability to use the system can be revoked.  That's a tough one in the US, especially when the system goes wrong, either by mistake or by lying.  At least in my view, the Swedes are bit more trustworthy than the people of Walmart. So while I think the idea of mobile self-checkout has merit, perhaps its not right for Walmart.

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  • Drawing lots of tiles with OpenGL, the modern way

    - by Nic
    I'm working on a small tile/sprite-based PC game with a team of people, and we're running into performance issues. The last time I used OpenGL was around 2004, so I've been teaching myself how to use the core profile, and I'm finding myself a little confused. I need to draw in the neighborhood of 250-750 48x48 tiles to the screen every frame, as well as maybe around 50 sprites. The tiles only change when a new level is loaded, and the sprites are changing all the time. Some of the tiles are made up of four 24x24 pieces, and most (but not all) of the sprites are the same size as the tiles. A lot of the tiles and sprites use alpha blending. Right now I'm doing all of this in immediate mode, which I know is a bad idea. All the same, when one of our team members tries to run it, he gets very bad frame rates (~20-30 fps), and it's much worse when there are more tiles, especially when a lot of those tiles are the kind that are cut into pieces. This all makes me think that the problem is the number of draw calls being made. I've thought of a few possible solutions to this, but I wanted to run them by some people who know what they're talking about so I don't waste my time on something stupid: TILES: When a level is loaded, draw all the tiles once into a frame buffer attached to a big honking texture, and just draw a big rectangle with that texture on it every frame. Put all the tiles into a static vertex buffer when the level is loaded, and draw them that way. I don't know if there's a way to draw objects with different textures with a single call to glDrawElements, or if this is even something I'd want to do. Maybe just put all the tiles into a big giant texture and use funny texture coordinates in the VBO? SPRITES: Draw each sprite with a separate call to glDrawElements. Use a dynamic VBO somehow. Same texture question as number 2 above. Point sprites? This is probably silly. Are any of these ideas sensible? Is there a good implementation somewhere I could look over?

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  • Thoughts on schemas and schema proliferation

    - by jamiet
    In SQL Server 2005 Microsoft introduced user-schema separation and since then I have seen the use of schemas increase; whereas before I would typically see databases where all objects were in the [dbo] schema I now see databases that have multiple schemas, a database I saw recently had 31 (thirty one) of them. I can’t help but wonder whether this is a good thing or not – clearly 31 is an extreme case but I question whether multiple schemas create more problems than they solve? I have been involved in many discussions that go something like this: Developer #1> “I have a new function to add to the database and I’m not sure which schema to put it in” Developer #2> “What does it do?” Developer #1> “It provides data to a report in Reporting Services” Developer #2> “Ok, so put it in the [reports] schema” Developer #1> “Well I could, but the data will only be used by our Financial reporting folks so shouldn’t I put it in the [financial] schema?” Developer #2> “Maybe, yes” Developer #1> “Mind you, the data is supposed to be used for regulatory reporting to the FSA, should I put it in [regulatory]?” Developer #2> “Err….” You get the idea!!! The more schemas that exist in your database then the more chance that their supposed usages will overlap. I’m left wondering whether the use of schemas is actually necessary. I don’t view really see them as an aid to security because I generally believe that principles should be assigned permissions on objects as-needed on a case-by-case basis (and I have a stock SQL query that deciphers them all for me) so why bother using them at all? I can envisage a use where a database is used to house objects pertaining to many different business functions (which, in itself, is an ambiguous term) and in that circumstance perhaps a schema per business function would be appropriate; hence of late I have been loosely following this edict: If some objects in a database could be moved en masse to another database without the need to remove any foreign key constraints then those objects could legitimately exist in a dedicated schema. I am interested to know what other people’s thoughts are on this. If you would like to share then please do so in the comments. @Jamiet

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  • What are some reasonable stylistic limits on type inference?

    - by Jon Purdy
    C++0x adds pretty darn comprehensive type inference support. I'm sorely tempted to use it everywhere possible to avoid undue repetition, but I'm wondering if removing explicit type information all over the place is such a good idea. Consider this rather contrived example: Foo.h: #include <set> class Foo { private: static std::set<Foo*> instances; public: Foo(); ~Foo(); // What does it return? Who cares! Just forward it! static decltype(instances.begin()) begin() { return instances.begin(); } static decltype(instances.end()) end() { return instances.end(); } }; Foo.cpp: #include <Foo.h> #include <Bar.h> // The type need only be specified in one location! // But I do have to open the header to find out what it actually is. decltype(Foo::instances) Foo::instances; Foo() { // What is the type of x? auto x = Bar::get_something(); // What does do_something() return? auto y = x.do_something(*this); // Well, it's convertible to bool somehow... if (!y) throw "a constant, old school"; instances.insert(this); } ~Foo() { instances.erase(this); } Would you say this is reasonable, or is it completely ridiculous? After all, especially if you're used to developing in a dynamic language, you don't really need to care all that much about the types of things, and can trust that the compiler will catch any egregious abuses of the type system. But for those of you that rely on editor support for method signatures, you're out of luck, so using this style in a library interface is probably really bad practice. I find that writing things with all possible types implicit actually makes my code a lot easier for me to follow, because it removes nearly all of the usual clutter of C++. Your mileage may, of course, vary, and that's what I'm interested in hearing about. What are the specific advantages and disadvantages to radical use of type inference?

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  • Is There a Real Advantage to Generic Repository?

    - by Sam
    Was reading through some articles on the advantages of creating Generic Repositories for a new app (example). The idea seems nice because it lets me use the same repository to do several things for several different entity types at once: IRepository repo = new EfRepository(); // Would normally pass through IOC into constructor var c1 = new Country() { Name = "United States", CountryCode = "US" }; var c2 = new Country() { Name = "Canada", CountryCode = "CA" }; var c3 = new Country() { Name = "Mexico", CountryCode = "MX" }; var p1 = new Province() { Country = c1, Name = "Alabama", Abbreviation = "AL" }; var p2 = new Province() { Country = c1, Name = "Alaska", Abbreviation = "AK" }; var p3 = new Province() { Country = c2, Name = "Alberta", Abbreviation = "AB" }; repo.Add<Country>(c1); repo.Add<Country>(c2); repo.Add<Country>(c3); repo.Add<Province>(p1); repo.Add<Province>(p2); repo.Add<Province>(p3); repo.Save(); However, the rest of the implementation of the Repository has a heavy reliance on Linq: IQueryable<T> Query(); IList<T> Find(Expression<Func<T,bool>> predicate); T Get(Expression<Func<T,bool>> predicate); T First(Expression<Func<T,bool>> predicate); //... and so on This repository pattern worked fantastic for Entity Framework, and pretty much offered a 1 to 1 mapping of the methods available on DbContext/DbSet. But given the slow uptake of Linq on other data access technologies outside of Entity Framework, what advantage does this provide over working directly with the DbContext? I attempted to write a PetaPoco version of the Repository, but PetaPoco doesn't support Linq Expressions, which makes creating a generic IRepository interface pretty much useless unless you only use it for the basic GetAll, GetById, Add, Update, Delete, and Save methods and utilize it as a base class. Then you have to create specific repositories with specialized methods to handle all the "where" clauses that I could previously pass in as a predicate. Is the Generic Repository pattern useful for anything outside of Entity Framework? If not, why would someone use it at all instead of working directly with Entity Framework? Edit: Original link doesn't reflect the pattern I was using in my sample code. Here is an (updated link).

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  • Started wrong with a project. Should I start over?

    - by solidsnake
    I'm a beginner web developer (one year of experience). A couple of weeks after graduating, I got offered a job to build a web application for a company whose owner is not much of a tech guy. He recruited me to avoid theft of his idea, the high cost of development charged by a service company, and to have someone young he can trust onboard to maintain the project for the long run (I came to these conclusions by myself long after being hired). Cocky as I was back then, with a diploma in computer science, I accepted the offer thinking I can build anything. I was calling the shots. After some research I settled on PHP, and started with plain PHP, no objects, just ugly procedural code. Two months later, everything was getting messy, and it was hard to make any progress. The web application is huge. So I decided to check out an MVC framework that would make my life easier. That's where I stumbled upon the cool kid in the PHP community: Laravel. I loved it, it was easy to learn, and I started coding right away. My code looked cleaner, more organized. It looked very good. But again the web application was huge. The company was pressuring me to deliver the first version, which they wanted to deploy, obviously, and start seeking customers. Because Laravel was fun to work with, it made me remember why I chose this industry in the first place - something I forgot while stuck in the shitty education system. So I started working on small projects at night, reading about methodologies and best practice. I revisited OOP, moved on to object-oriented design and analysis, and read Uncle Bob's book Clean Code. This helped me realize that I really knew nothing. I did not know how to build software THE RIGHT WAY. But at this point it was too late, and now I'm almost done. My code is not clean at all, just spaghetti code, a real pain to fix a bug, all the logic is in the controllers, and there is little object oriented design. I'm having this persistent thought that I have to rewrite the whole project. However, I can't do it... They keep asking when is it going to be all done. I can not imagine this code deployed on a server. Plus I still know nothing about code efficiency and the web application's performance. On one hand, the company is waiting for the product and can not wait anymore. On the other hand I can't see myself going any further with the actual code. I could finish up, wrap it up and deploy, but god only knows what might happen when people start using it. What do you think I should do?

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  • Unable to boot ubuntu 11.10 from external usb drive

    - by user45006
    I'm new to Ubuntu (and actually all things Linux) as of this morning, so please excuse any stupid mistakes I may be making. I recently bought an external hard drive for my newly built PC (that is running windows 7 if it matters). I would like to install Ubuntu onto the external drive and boot from there. I downloaded Ubuntu 11.10 and made a bootable cd, unplugged my internal HDDs, plugged in the external drive, installed Ubuntu 11.10 on the external drive via the installer, and replugged in my internal HDDs. Then I set my bios boot order to: Boot from USB-HDD - Boot from Hard Disk - Boot from CD/DVD. Now when I restart I get the message "Starting Operating System..." (or something like that, I forget exactly what it says) that lingers on the screen for a moment and then windows starts. Any idea what the problem may be? ~Relevant info~ BIOS version: Award Software International, Inc. F2, 2/22/2011 Ubuntu Version: 11.10 External Hard Drive: Western Digital My Passport Essential 500GB Portable Hard Drive (Black) ~Things I've already tried~ 1) Unplug internal HDDs so that only external drive was plugged in via usb. Same thing happened only obviously my BIOS could not detect any hard drives besides the external one. When booting received error "Could not detect operating system" 2) Formatted external hard drive and re installed. It didn't make a difference, however interestingly when I booted from cd the ubuntu installer said it detected ubuntu 11.10 on the external hard drive. 3) Within BIOS I've messed around with every boot order combo I could think of both in the "Hard Disk boot order" screen and the "Boot order" screen. I'm a little confused of why there are two screens for this. 4) Held F12 during startup which opens (what I think is) the one time boot screen and it gave me the options "Hard Drive", "cd/dvd", "USB-FDD", "USB-cdrom", "USB-HDD", and "USB-something else I can't remember what it was". I tried all of them, but the same thing as before happened each time. ~References~ I noticed several people on askubuntu have tried to do something similar if not the exact same. In fact, I even found a post that pretty much outlines step by step exactly what I did... only their's worked. /jealous. Linky: Install Ubuntu or Kubuntu on a External USB Drive I'm willing to try a different version of ubuntu - it's not like my heart is set on 11.10, but it's a pain to open my case and unplug my internal hard drives so I'd prefer not to do this unless someone is reasonably confident it'll work. Thank you for all of your help in advance! I'm really looking forward to exploring Ubuntu!

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  • Installed LibreOffice 4 with ppa, how do I remove it and go back to LibreOffice 3?

    - by MMA
    EDIT This question is not at all a duplicate of How to downgrade from LibreOffice 4.0 to 3.6? The above mentioned question talks about downgrading from a specific version of LibreOffice, namely from 4.0 to 3.6. The solutions mentioned are not the ones I am looking for. They will work but I wanted a general solution without using PPA or downloading .deb files for from a higher version to a lower version. The above solutions suggest either downloading .deb files for LibreOffice 3.6 or adding repository for it. Furthermore, some of the answers put out-of-proportion~(applicable for the solution, however) stress on use of synaptic, not general command-line-solution. That made me wonder, at this very moment, if I take a fresh computer, and install Ubuntu 12.04, LibreOffice installation will work without a hitch. Then why I can not install LibreOffice in my 12.04 machine today from simple command line? This answer to my question, clarified everything. I need to use ppa-purge so that this resets all packages from a PPA to the standard versions released for my distribution. Basically it is like a way to restore my system back to the way it was before my installed packages from a PPA. This article further elaborates the idea. The above mentioned answer worked perfectly for me. Actually, this was an education for me since it taught me how do downgrade a package that was added via PPA. I had upgraded from LibreOffice 3 to LibreOffice 4 using the PPA. Now since I found that LibreOffice 4 has some issues, including handling my native language, I want to move back to LibreOffice 3. In order to accomplish this, I removed the LibreOffice config directory from my home and then purged LibreOffice from my machine. sudo apt-get purge libreoffice-* Then I removed the relevant PPA's using the sudo apt-add-repository --remove command. And then ran sudo apt-get update. Now, when I try to install LibreOffice using the command sudo apt-get install libreoffice I get an avalanche of output about unmet dependencies, something like, The following packages have unmet dependencies: libreoffice : Depends: libreoffice-core (= 1:3.5.7-0ubuntu4) but it is not going to be installed (snipped) If I dig the issue further, by using the command, sudo apt-get install libreoffice-core I get The following packages have unmet dependencies: libreoffice-core : Depends: libreoffice-common (> 1:3.5.7) but it is not going to be installed Depends: libexttextcat0 (>= 2.2-8) but it is not going to be installed Depends: ure (>= 3.5.7~) but it is not going to be installed E: Unable to correct problems, you have held broken packages. Could you please tell me how do I install LibreOffice 3 in my machine? I am using Ubuntu 12.04 LTS.

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  • Windows8, JavaScript and HTML5 - A good thing?

    - by Albers
    Most of us have seen the Windows 8 news regarding support for native HTML5/JavaScript applications. The press has pushed this as a potential threat to the .NET developer community because JavaScript and HTML5 were called "our new developer platform". The press release refers to "Web-connected and Web-powered apps built using HTML5 and JavaScript that have access to the full power of the PC.".Microsoft has also been hush on details related to these comments. Before we buy the hype and start worrying about a world where we drop our Visual Studio licenses and buy DreamWeaver - let's think about how Windows 8 HTML/JavaScript applications would be implemented. The HTML5 spec offers support for offline applications, but this won't offer the OS-integrated experience the press release refers to. MS has to be planning a way to extend access beyond the traditional JavaScript feature set. Microsoft has a similar option today: HTML Applications or HTAs. They come close to required features, but HTAs need ActiveX or Java integration to provide the promised OS-level access. I'm guessing that Microsoft's future OS strategy isn't built on developers cranking out ActiveX controls or Java applets. So where is Microsoft headed? One possibility is that MS builds a new JavaScript framework from the ground up outside their current APIs. Another idea would be for Microsoft to add support for JavaScript as a first class .NET language using the Dynamic Language Runtime. A solution based on the DLR could be integrated into an HTA-like model to provide the promised access, along with the full range of features in .NET Framework. Security comes included in the Framework. And the work necessary to support this integration would tie in nicely with the effort MS has recently made providing better JavaScript and HTML5 support in Visual Studio 2010. As a bonus, a full-fledged JavaScript DLR implementation would allow single language web solutions across client and server (think node.js) and would appeal to developers who are familiar with JavaScript but have less experience with the Microsoft tech stack. We will all get a better picture after the Build conference in September. But in the mean time we know that Microsoft has a reputation for providing strong developer support. We might want to reserve our harshest judgement and consider that the press release could hint at new opportunities for .NET development.

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  • How to implement an intelligent enemy in a shoot-em-up?

    - by bummzack
    Imagine a very simple shoot-em-up, something we all know: You're the player (green). Your movement is restricted to the X axis. Our enemy (or enemies) is at the top of the screen, his movement is also restricted to the X axis. The player fires bullets (yellow) at the enemy. I'd like to implement an A.I. for the enemy that should be really good at avoiding the players bullets. My first idea was to divide the screen into discrete sections and assign weights to them: There are two weights: The "bullet-weight" (grey) is the danger imposed by a bullet. The closer the bullet is to the enemy, the higher the "bullet-weight" (0..1, where 1 is highest danger). Lanes without a bullet have a weight of 0. The second weight is the "distance-weight" (lime-green). For every lane I add 0.2 movement cost (this value is kinda arbitrary now and could be tweaked). Then I simply add the weights (white) and go to the lane with the lowest weight (red). But this approach has an obvious flaw, because it can easily miss local minima as the optimal place to go would be simply between two incoming bullets (as denoted with the white arrow). So here's what I'm looking for: Should find a way through bullet-storm, even when there's no place that doesn't impose a threat of a bullet. Enemy can reliably dodge bullets by picking an optimal (or almost optimal) solution. Algorithm should be able to factor in bullet movement speed (as they might move with different velocities). Ways to tweak the algorithm so that different levels of difficulty can be applied (dumb to super-intelligent enemies). Algorithm should allow different goals, as the enemy doesn't only want to evade bullets, he should also be able to shoot the player. That means that positions where the enemy can fire at the player should be preferred when dodging bullets. So how would you tackle this? Contrary to other games of this genre, I'd like to have only a few, but very "skilled" enemies instead of masses of dumb enemies.

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  • Thinkpad brightness steps error using FN+Home/End

    - by petermolnar
    I've met the following problem: normally my T400 (Lenovo Thinkpad) has 16 steps of brightness, and Windows utilizes it correctly. After a fresh install & minor tweaks Mint 12 (which is based on 11.10 Ubuntu) I only had 6 steps which was way to few. Listing /sys/class/backlight showed 3 entried. I removed the acpi-tools package, one of the disapperared - and I now have 10 steps! Therefore I think if I can reduce the entries to 1 I'm going to have 16 steps, since the stepping will be 1 instead of 2 (or 3). /sys/class/backlight/ intel_backlight -> ../../devices/pci0000:00/0000:00:02.0/drm/card0/card0-LVDS-1/intel_backlight thinkpad_screen -> ../../devices/virtual/backlight/thinkpad_screen The problem is that I'm unable to trace back what are the configs / daemons / kernel options triggers these two. More strangely, I discovered a strange behaviour. I monitored watch -n1 "cat /sys/class/backlight/thinkpad_screen/actual_brightness" and watch -n1 "cat /sys/class/backlight/intel_backlight/actual_brightness" while changing the brightness with FN+home/end combinations from max to min. The outcome is the following: brighness intel thinkpad --------- ----- -------- MAX 2408475 7 | 1955115 5 | 1435640 3 | 1246740 1 | 1086175 0 | 1010615 6 | 859495 4 | 689485 2 v 481695 0 MIN 217235 0 brighness intel thinkpad --------- ----- -------- MIN 217235 0 | 481695 2 | 689485 4 | 859495 6 | 1010615 7 | 1086175 1 | 1246740 3 | 1435640 5 v 1955115 7 MAX 2408475 0 When stepping from MIN to MAX, there's no difference between the last 2 steps. Also, the OSD icon (Cinnamon desktop, default theme) goes from full to min in 4 steps and from full to min once again in 4 steps. So... it seems that the intel entry is working correctly, showing correct values. The thinkpad entry however twists the things and even showing incorrect values. Does anyone have any idea how to get rid of the thinkpad entry? System data: Linux Mint 12 3.0.0-16 kernel Lenovo ThinkPad T400 Cinnamon 1.4 desktop For any additional info, please tell me what do you need. EDIT I'm sorry, I forgot to mention, I added acpi_backlight=vendor to GRUB cmdline as well, this is the result of the semi-better working than the default.

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  • How exactly is Google Webmaster Tools measuring "Site Performance"?

    - by Rémi
    I've been working for two months now on improving our response time (mainly server side) on a new forum (a brand new product on a technical point of view) we've launched in Germany a few month ago and I'm a lot surprised by the results I get. I monitor our response time using Apache logs and our own implementation of Boomerang beacon. Using my stats, I can see that our new product responds in about 680 ms where our old product was responding in about 1050 ms. On the other side, Google Webmaster Tool tells us that our pages have an average reponse time of about 1500 ms today where it was 700 three months ago with our old product. I've figured that GWT was taking client side metrics into account so I've added some measures on our Boomerang beacon and everything looks just fine. I've also ran some random pages on ySlow and Google's Page Speed and everything looks better than it was before. We event have a 82% on Google's Page Speed tool which is quite cool for a site with some ads in it :) Lately, we have signed a deal with Akamai to use two of their products : CDN for our static files (we were using another CDN before but it wasn't very effective) and RMA to improve Networks routes. We have also introduced a new agressive cache mecanism to ensure that most of the pages served to crawlers are cached by our memcache grid. After checking my metrics, it seems that this changes have improved from 650ms to about 500ms, which is good (still not great but it is definitly an improvement). But webmaster tools continues to report an increasing average response time where we see it decreasing in the same time. Have you ever had the same kind of wierd behavior on your sites while doing performance improvements ? Do you have any idea how to monitor the same thing Google does with Site Performance in Google Webmaster Tools so that we could improve our site and constantly check if it is what Google wants ? Edit 2011/07/26 : Thanks for your answers guys ! Nevertheless, I was not precise enough. The main issue we have is not with the Site Performance page but with the Crawl Stats one for now. We probably found an issue on our side with some very slow pages (around 3000 ms !!) and we are trying to fix them. I'll keep you posted as soon I'll have some infos. Thanks again !

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  • What layer to introduce human readable error messages?

    - by MrLane
    One of the things that I have never been happy with on any project I have worked on over the years and have really not been able to resolve myself is exactly at what tier in an application should human readable error information be retrieved for display to a user. A common approach that has worked well has been to return strongly typed/concrete "result objects" from the methods on the public surface of the business tier/API. A method on the interface may be: public ClearUserAccountsResult ClearUserAccounts(ClearUserAccountsParam param); And the result class implementation: public class ClearUserAccountsResult : IResult { public readonly List<Account> ClearedAccounts{get; set;} public readonly bool Success {get; set;} // Implements IResult public readonly string Message{get; set;} // Implements IResult, human readable // Constructor implemented here to set readonly properties... } This works great when the API needs to be exposed over WCF as the result object can be serialized. Again this is only done on the public surface of the API/business tier. The error message can also be looked up from the database, which means it can be changed and localized. However, it has always been suspect to me, this idea of returning human readable information from the business tier like this, partly because what constitutes the public surface of the API may change over time...and it may be the case that the API will need to be reused by other API components in the future that do not need the human readable string messages (and looking them up from a database would be an expensive waste). I am thinking a better approach is to keep the business objects free from such result objects and keep them simple and then retrieve human readable error strings somewhere closer to the UI layer or only in the UI itself, but I have two problems here: 1) The UI may be a remote client (Winforms/WPF/Silverlight) or an ASP.NET web application hosted on another server. In these cases the UI will have to fetch the error strings from the server. 2) Often there are multiple legitimate modes of failure. If the business tier becomes so vague and generic in the way it returns errors there may not be enough information exposed publicly to tell what the error actually was: i.e: if a method has 3 modes of legitimate failure but returns a boolean to indicate failure, you cannot work out what the appropriate message to display to the user should be. I have thought about using failure enums as a substitute, they can indicate a specific error that can be tested for and coded against. This is sometimes useful within the business tier itself as a way of passing via method returns the specifics of a failure rather than just a boolean, but it is not so good for serialization scenarios. Is there a well worn pattern for this? What do people think? Thanks.

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  • What does the Spring framework do? Should I use it? Why or why not?

    - by sangfroid
    So, I'm starting a brand-new project in Java, and am considering using Spring. Why am I considering Spring? Because lots of people tell me I should use Spring! Seriously, any time I've tried to get people to explain what exactly Spring is or what it does, they can never give me a straight answer. I've checked the intros on the SpringSource site, and they're either really complicated or really tutorial-focused, and none of them give me a good idea of why I should be using it, or how it will make my life easier. Sometimes people throw around the term "dependency injection", which just confuses me even more, because I think I have a different understanding of what that term means. Anyway, here's a little about my background and my app : Been developing in Java for a while, doing back-end web development. Yes, I do a ton of unit testing. To facilitate this, I typically make (at least) two versions of a method : one that uses instance variables, and one that only uses variables that are passed in to the method. The one that uses instance variables calls the other one, supplying the instance variables. When it comes time to unit test, I use Mockito to mock up the objects and then make calls to the method that doesn't use instance variables. This is what I've always understood "dependency injection" to be. My app is pretty simple, from a CS perspective. Small project, 1-2 developers to start with. Mostly CRUD-type operations with a a bunch of search thrown in. Basically a bunch of RESTful web services, plus a web front-end and then eventually some mobile clients. I'm thinking of doing the front-end in straight HTML/CSS/JS/JQuery, so no real plans to use JSP. Using Hibernate as an ORM, and Jersey to implement the webservices. I've already started coding, and am really eager to get a demo out there that I can shop around and see if anyone wants to invest. So obviously time is of the essence. I understand Spring has quite the learning curve, plus it looks like it necessitates a whole bunch of XML configuration, which I typically try to avoid like the plague. But if it can make my life easier and (especially) if make it can make development and testing faster, I'm willing to bite the bullet and learn Spring. So please. Educate me. Should I use Spring? Why or why not?

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