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  • Limitations of the SharePoint join using CAML

    - by ybbest
    Limitation One In SharePoint 2010, you can join the primary list to a foreign list and include more than one field from the foreign list. However, the limitation is that the included fields from foreign list have to be the following type: Calculated (treated as plain text) ContentTypeId Counter Currency DateTime Guid Integer Note (one-line only) Number Text The above limitation also explains why you cannot include some types of the fields from the remote list when creating a lookup. Limitation Two When using CAML query to join SharePoint lists, there can be joins to multiple lists, multiple joins to the same list, and chains of joins. However, the limitations are only inner and left outer joins are permitted and the field in the primary list must be a Lookup type field that looks up to the field in the foreign list. Limitation Three The support for writing the JOIN query in CAML is very limited.I have to hand-code the CAML query to join the lists,not fun at all.Although some blogs post mentioned about using LINQ to SharePoint and get the CAML code from there , but I never get it to work.You can check this blog post  for this.Let me know if it works for you. References: http://msdn.microsoft.com/en-us/library/ee535502.aspx http://msdn.microsoft.com/en-us/library/microsoft.sharepoint.spquery.joins.aspx

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  • How to set up an inter-OS partition?

    - by Confuzzled Persun
    I need a working partition configuration for use and accessibility on both Ubuntu and Windows. I have an 8GB USB flash drive onto which I am installing Ubuntu 11.10 so that I can have a personal bootable OS wherever I go. I've installed Ubuntu several times, but I just can't seem to get this one partition right. This is my own configuration: Partition 1: Primary - 200MB - Beginning - Ext4 - /boot Partition 2: Primary - 1300MB - End - swap area Partition 3: Logical - 5200MB - Beginning - Ext4 - / Partition 4: Logical - 1258MB - Beginning - Ext4 - /home Partition 5: Logical - 42MB - End - FAT32? - /windows? What I want to do is to get partition 5 configured so I can access it on both the installed Ubuntu system and a Windows system (when the USB drive is connected while Windows is booted). Basically, what I want is Ubuntu installed on the USB drive along with a partition that I can access with other operating systems. I'm thinking I just need the technical configuration of "Use as:" and "Mount point:" for my final partition. But I don't know. Any help with this is appreciated. And any other tips are appreciated as well.

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  • Philosophy behind the memento pattern

    - by TheSilverBullet
    I have been reading up on memento pattern from various sources of the internet. Differing information from different sources has left me in confusion regarding why this pattern is actually needed. The dofactory implementation says that the primary intention of this pattern is to restore the state of the system. Wiki says that the primary intention is to be able to restore the changes on the system. This gives a different impact - saying that it is possible for a system to have memento implementation with no need to restore. And that ability of restore is a feature of this. OODesign says that It is sometimes necessary to capture the internal state of an object at some point and have the ability to restore the object to that state later in time. Such a case is useful in case of error or failure. So, my question is why exactly do we use this one? Is it to save previous states - or to promote encapsulation between the Caretaker and the Memento? Why is this type of encapsulation so important? Edit: For those visiting, check out this Implementation!

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  • alt+tab moves windows between workspaces and crashes unity

    - by Ruslanchik
    I have recently been using multiple workspaces in unity but have run into a bug that is making it very difficult to do this effectively. The problem is with alt+tab. When I am focused on a window that is not in the primary (top-left) workspace one of two things happens: Unity restarts (the launcher and menu bar disappear and screen flashes blank before everything reappears) and all of my windows are moved to different workspaces. The focused window is always moved to the primary workspace and other windows are typically moved one workspace to the left. alt+tab will usually function normally after this. Unity completely crashes. The windows in the current workspace are still there, but the launcher and menu bar are gone, I cannot switch between workspaces, and none of the hotkeys work. The same issues occur when using alt+` as well. I have installed ccsm, but have made only minor adjustments with it. I am still using the Unity switcher. I actually uninstalled ccsm hoping that would resolve the issue, but the issue persists. Is there some resolution to this issue? I like Unity and want to keep using it, but having to use the mouse to switch between programs is irritating and enough reason to switch to Gnome.

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  • Installing Ubuntu along with windows 7 on shrunk partition

    - by Thabo
    I am new to Ubuntu OS and ask Ubuntu community. First this is not a duplicate question. Actually this a question which is a summery of all solutions and questions were posted in this community, related to Install Ubuntu along with Windows 7. I have bought a new Hp laptop with its original windows 7.I want to install Ubuntu along with windows 7 64 bit. I ran the Ubuntu 12.4 Desktop installation CD. But Ubuntu installer doesn't show the "along with windows 7 option"only it is showing two options. I read some questions and answers posted on this community. Specially following link Ubuntu 12.04 does not see windows already install on my computer (dual installation) I tried following thinks, I ran the terminal in live CD and tried sudo dmraid -rE command and dmraid remove command .But terminals says there is no dmraid partitions. So I tried another scenario checked my partitions with g parted.There are some partitions labeled C,HP tools,Recovery and System. C is containing windows 7 Files. So I shrank the volume of C Drive. Now I have 50000Mb of unallocated disk. I tried with Gparted to create a partition on that allocated space.It says some thing that you can't create more than four primary partition.Of course all other four partitions were created on widows are actually type of primary partition. So I went back to Windows 7 and tried to create a new volume on unallocated space.But unfortunately it says,If i create a new volume it will be the type of Dynamic partition.It says we cant boot another OS from that partition. So i cancelled that step. Now i have 50000Mb unallocated space but how can i install Ubuntu on that partition without harming the existing Windows 7? Because still I have only two options: Erase and install Ubuntu. Try something else. (I can see my unallocated space by going to "something else" option.)

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  • Standard Network Tiers in a Distributed N-Tier System

    Distributed N-Tier client/server architecture allows for segments of an application to be broken up and distributed across multiple locations on a network.  Listed below are standard tiers in a Distributed N-Tier System. End-User Client Tier The End-User Client is responsible for sending and receiving requests from web servers and other applications servers and translating the responses so that the End-User can interpret the data effectively. The primary roles for this tier are to communicate with servers and translate server responses back to the end-user to interpret. Business-Specific Functions Validate Data Display Data Send Data to Webserver Web Server Tier The Web server tier processes new requests for information coming in from the HTTP and HTTPS ports. This primarily handles the generation of user interfaces and calls the application server when needed to access Data and business logic when needed. Business-specific functions Send Data to application server Format Data for Display Validate Data Application Server Tier The application server stores and executes predefined business logic that is applied to various pieces of data as the business determines. The processed data is then returned back to the Webserver. Additionally, this server directly calls the database to obtain and store any data used by the system Business-Specific Functions Validate Data Process Data Send Data to Database Server Database Server Tier The Database Server is responsible for storing and returning all data need by the calling applications. The primary role for this this server is storage. Data is stored as needed and can be recalled at any point later in time. Business-Specific Functions Insert Data Delete Data Return Data to Application Server

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  • Creating floppy drive special devices under Quantal

    - by JCCyC
    First, I'd like for the various special devices for different floppy capacities (like /dev/fd0u720 etc.) to be available. I tried to adapt some udev rules I found online. I tried this, which I saved as /etc/udev/rules.d/70-persistent-floppy.rules: # change floppy device ownership and permissions # default permissions are 640, which prevents group users from having write access # first fix primary devices (/dev/fd0, /dev/fd1, etc.) # also change group ownership from disk to floppy SUBSYSTEM=="block", KERNEL=="fd[0-9]*", GROUP="floppy", MODE="0660" # next recreate secondary devices (/dev/fd0u720, /dev/fd0u1440, etc.) SUBSYSTEM=="block", KERNEL=="fd[0-9]*", ACTION=="add", RUN+="create_floppy_devices -c -t $attr{cmos} -m %M -M 0660 -G floppy $root/%k" But to no avail. It seems the create_floppy_devices script isn't provided with 12.10. How do I obtain it? Second: I'm using MATE, and whenever I log in I get a message box saying it tried to mount the drive but failed. How do I disable this? Third (which is probably related to the second): Whenever there's a disk in the drive, the motor won't stop spinning. If I do a mdir of it, after it returns, the motor stops, and then starts again. I suspect there's some process in MATE doing this. UPDATE: For CentOS 6 (who does have a create_floppy_devices program) the following rules file worked. Saved as /etc/udev/rules.d/98-floppy.rules: # change floppy device ownership and permissions # default permissions are 640, which prevents group users from having write access # first fix primary devices (/dev/fd0, /dev/fd1, etc.) # also change group ownership from disk to floppy KERNEL=="fd[0-9]*", GROUP="floppy", MODE="0660" # next recreate secondary devices (/dev/fd0u720, /dev/fd0u1440, etc.) # drive A: is type 4 (1.44MB) - add other lines for other drives KERNEL=="fd0*", ACTION=="add", RUN+="/lib/udev/create_floppy_devices -c -t 4 -m %M -M 0660 -G floppy $root/%k"

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  • Ubuntu 11.10 not starting in Graphical mode?

    - by iammilind
    I am in deep trouble. I am using Ubuntu 11.10 in dual boot mode with XP. Originally my touch pad was not working, (sometimes). To fix that, I installed something. After reboot my Ubuntu is not booting up!! I have several software pkgs already installed in past several weeks so reinstall of OS is my last resort. Can someone help me to get it rebooted in graphical mode? I had followed the procedure mentioned in this thread as well. With that link, somehow I am able to restart in text mode. But no luck after that. I am not being able to go back on graphical mode. The important outputs of lspci are following: 00.00.0 Host bridge: Intel Corporation Mobile PM965/GM965/GL960 Memory Controller Hub (rev 0c) 00:02.0 VGA compatible controller: Intel Corporation Mobile GM965/GL960 Integrated Graphics Controller (primary) (rev 0c) 00:02.0 Display controller: Intel Corporation Mobile GM965/GL960 Integrated Graphics Controller (primary) (rev 0c) I am attaching few snapshots, for more details on hardware.

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  • How to force Multiple Monitors correct resolutions for LightDM?

    - by Hanynowsky
    I am affected by the BUG: https://bugs.launchpad.net/ubuntu/+source/unity-greeter/+bug/874241 Otherwise, if like me you have a laptop connected to a second monitor of higher resolution, LIGHTDM at the login stage, mirrors the displays in both screens and assign to them a common resolution (1024X768) in my case, instead of extending the desktop (Primary screen with the greeter and secondary with just a logo as mentioned in the Multiple Monitors UX specifications book for 12.04). Here is my xrandr -q @L502X:~$ xrandr -q Screen 0: minimum 320 x 200, current 1920 x 1848, maximum 8192 x 8192 LVDS1 connected 1366x768+309+1080 (normal left inverted right x axis y axis) 344mm x 193mm 1366x768 60.0*+ 1360x768 59.8 60.0 1024x768 60.0 800x600 60.3 56.2 640x480 59.9 VGA1 disconnected (normal left inverted right x axis y axis) HDMI1 connected 1920x1080+0+0 (normal left inverted right x axis y axis) 510mm x 287mm 1920x1080 60.0*+ 1600x1200 60.0 1680x1050 60.0 1280x1024 60.0 1440x900 59.9 1280x960 60.0 1280x800 59.8 1024x768 60.0 800x600 60.3 56.2 640x480 60.0 DP1 disconnected (normal left inverted right x axis y axis) I tried to force lightdm to execute some xrandr commands in order to set the right resolution for each monitor and extend the desktop, but I get a LOW GRAPHICS MODE ERROR (You're running in low graphics mode, your screen, input devices...did not get detected..) I created a simple script named lightdmxrand.sh: #!/bin/sh xrandr --output HDMI1 --primary --mode 1920x1080 --output LVDS1 --mode 1366x768 --below HDMI1 And told lightdm to run it : /etc/lightdm/lightdm.conf [SeatDefaults] greeter-session=unity-greeter user-session=ubuntu greeter-setup-script=/usr/bin/numlockx on display-setup-script=/home/hanynowsky/lightdmxrandr.sh Someone knows what is wrong!? Thanks in advance.

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  • preseeded installation keeps asking for confirmation while creating RAID-Partitions on certain hardware-platform

    - by Marc Shennon
    I am aware of the partman-md/confirm_nooverwrite thing, that was the solution to most of this problems in the past. The thing is, that the preseed-file works for almost all hardware-platforms I tested, but only for one (Primergy MX130) it keeps asking for confirmation, before writing the partition-layout to the disks. All machines I tested are running with two SATA Disks, nothing special. I'm not really sure, what information could be needed in order to investigate the cause of this behaviour, but I would of course be willing to provide more information, if someone has an idea. Relevant part of the preseed file is the following: d-i partman-auto/disk string /dev/sda /dev/sdb d-i partman-auto/method string raid d-i partman-md/confirm boolean true d-i partman-partitioning/confirm_write_new_label boolean true d-i partman-md/device_remove_md boolean true d-i partman/choose_partition select finish d-i partman-md/confirm_nooverwrite boolean true # Write the changes to disks? d-i partman/confirm boolean true d-i mdadm/boot_degraded boolean true # RECIPE # Next you need to specify the physical partitions that will be used. d-i partman-auto/expert_recipe string \ multiraid :: \ 500 10000 1000000000 raid $lvmignore{ }\ $primary{ } \ method{ raid } \ . \ 512 1000 786 raid $lvmignore{ }\ $primary{ } \ method{ raid } \ . \ 8192 10240 10240 raid $lvmignore{ }\ method{ raid } \ . # Parameters are: # <raidtype> <devcount> <sparecount> <fstype> <mountpoint> <devices> <sparedevices> d-i partman-auto-raid/recipe string \ 1 2 0 ext4 / /dev/sda1#/dev/sdb1 . \ 1 2 0 ext2 /boot /dev/sda2#/dev/sdb2 . \ 1 2 0 swap - /dev/sda5#/dev/sdb5 .

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  • Partition does not start on physical sector boundary?

    - by jasmines
    I've one HD on my laptop, with two partitions (one ext3 with Ubuntu 12.04 installed and one swap). fdisk is giving me a Partition 1 does not start on physical sector boundary warning. What is the cause and do I need to fix it? If so, how? This is sudo fdisk -l: Disk /dev/sda: 750.2 GB, 750156374016 bytes 255 testine, 63 settori/tracce, 91201 cilindri, totale 1465149168 settori Unità = settori di 1 * 512 = 512 byte Sector size (logical/physical): 512 bytes / 4096 bytes I/O size (minimum/optimal): 4096 bytes / 4096 bytes Identificativo disco: 0x5a25087f Dispositivo Boot Start End Blocks Id System /dev/sda1 * 63 1448577023 724288480+ 83 Linux Partition 1 does not start on physical sector boundary. /dev/sda2 1448577024 1465147391 8285184 82 Linux swap / Solaris This is sudo lshw related result: *-disk description: ATA Disk product: WDC WD7500BPKT-0 vendor: Western Digital physical id: 0 bus info: scsi@0:0.0.0 logical name: /dev/sda version: 01.0 serial: WD-WX21CC1T0847 size: 698GiB (750GB) capabilities: partitioned partitioned:dos configuration: ansiversion=5 signature=5a25087f *-volume:0 description: EXT3 volume vendor: Linux physical id: 1 bus info: scsi@0:0.0.0,1 logical name: /dev/sda1 logical name: / version: 1.0 serial: cc5c562a-bc59-4a37-b589-805b27b2cbd7 size: 690GiB capacity: 690GiB capabilities: primary bootable journaled extended_attributes large_files recover ext3 ext2 initialized configuration: created=2010-02-27 09:18:28 filesystem=ext3 modified=2012-06-23 18:33:59 mount.fstype=ext3 mount.options=rw,relatime,errors=remount-ro,user_xattr,barrier=1,data=ordered mounted=2012-06-28 00:20:47 state=mounted *-volume:1 description: Linux swap volume physical id: 2 bus info: scsi@0:0.0.0,2 logical name: /dev/sda2 version: 1 serial: 16a7fee0-be9e-4e34-9dc3-28f4eeb61bf6 size: 8091MiB capacity: 8091MiB capabilities: primary nofs swap initialized configuration: filesystem=swap pagesize=4096 These are related /etc/fstab lines: UUID=cc5c562a-bc59-4a37-b589-805b27b2cbd7 / ext3 errors=remount-ro,user_xattr 0 1 UUID=16a7fee0-be9e-4e34-9dc3-28f4eeb61bf6 none swap sw 0 0

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  • Ubuntu 12.04 still slow at mounting internal filesystem

    - by Matthew Goson
    I'm using Toshiba laptop with this configuration: - CPU: Core i5, 2.4GHz - RAM: 4GB - Graphics card: Intel - Hard disk: 500GB SATA I installed Ubuntu 12.04 64bit and got the same issue with this guy Very slow boot due to mounting filesytem, I tried all suggestions there but the slow boot issue still here. Here's a part of my dmesg: [ 2.041015] usbhid: USB HID core driver [ 2.101378] usb 1-1.6: new full-speed USB device number 5 using ehci_hcd [ 2.137980] atl1c 0000:04:00.0: version 1.0.1.0-NAPI [ 2.779080] EXT4-fs (sda2): mounted filesystem with ordered data mode. Opts: (null) [ 22.822597] udevd[381]: starting version 175 [ 22.837954] ADDRCONF(NETDEV_UP): eth0: link is not ready [ 22.850837] lp: driver loaded but no devices found [ 23.003822] Adding 7079096k swap on /dev/sda7. Priority:-1 extents:1 across:7079096k [ 23.407915] mei: module is from the staging directory, the quality is unknown, you have been warned. [ 23.408153] mei 0000:00:16.0: PCI->APIC IRQ transform: INT A -> IRQ 16 [ 23.408160] mei 0000:00:16.0: setting latency timer to 64 [ 23.408211] mei 0000:00:16.0: irq 44 for MSI/MSI-X [ 23.433196] [drm] Initialized drm 1.1.0 20060810 Additional information: my sda1 is a primary NTFS partition, sda2 is a primary ext4 partition which I installed Ubuntu onto. Other partitions are inside an extended partition.

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  • Deal Registration Moves to Oracle Partner Store (OPS)- The Four Action Items for Partners

    - by Richard Lefebvre
    In November 2012, Oracle’s partner deal registration process will move to the Oracle Partner Store (OPS). During this time, OPS will become the single source for partners to register deals, obtain deal status, and place orders. What will partners need to do? 1. Request an OPS Account – If your company is new to OPS the first thing you need to do is request an account (if your company already has an OPS account, go to step 2). It’s important to have the person who will be managing your OPS account make this request as soon as possible. They will be set up as your company’s primary administrator. 2. Set-Up Users in OPS – Setup of users can start immediately, and will be handled by the primary OPS administrator at your company. The process is simple, but all existing users of Global PRM (Partner Relationship Management) deal registration will need to be set up in OPS before November 14, 2012.  3. Review/Action Any Registrations Pending Submission in PRM – Prior to November 14, 2012, all pending registrations should be submitted in the existing PRM system. It is important that this step is complete so registrations will not need to be re-entered when the system is moved to OPS on November 17, 2012. Registrations pending submission are easily identified on the registration listing screen with either “Incomplete” or “Returned to Partner” in the status column.  4. Attend Training – Oracle will offer multiple VAD and VAR training sessions beginning October 29, 2012. It is recommended that all users attend one of these important sessions.  Detailed instructions on each of these tasks can be found on the OPS Information Page. OPS will offer several enhancements to the deal registration process, including: Simplified Registration Form Easier Product Selection Expanded Browser Support Shared Registration Visibility Between VAD and VAR Pre-set Customer Selection From Partner Ordering Base Best Regards, Titina Ott Vice President, Worldwide A&C Systems And Business Processes 

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  • Impact of Server Failure on Coherence Request Processing

    - by jpurdy
    Requests against a given cache server may be temporarily blocked for several seconds following the failure of other cluster members. This may cause issues for applications that can not tolerate multi-second response times even during failover processing (ignoring for the moment that in practice there are a variety of issues that make such absolute guarantees challenging even when there are no server failures). In general, Coherence is designed around the principle that failures in one member should not affect the rest of the cluster if at all possible. However, it's obvious that if that failed member was managing a piece of state that another member depends on, the second member will need to wait until a new member assumes responsibility for managing that state. This transfer of responsibility is (as of Coherence 3.7) performed by the primary service thread for each cache service. The finest possible granularity for transferring responsibility is a single partition. So the question becomes how to minimize the time spent processing each partition. Here are some optimizations that may reduce this period: Reduce the size of each partition (by increasing the partition count) Increase the number of JVMs across the cluster (increasing the total number of primary service threads) Increase the number of CPUs across the cluster (making sure that each JVM has a CPU core when needed) Re-evaluate the set of configured indexes (as these will need to be rebuilt when a partition moves) Make sure that the backing map is as fast as possible (in most cases this means running on-heap) Make sure that the cluster is running on hardware with fast CPU cores (since the partition processing is single-threaded) As always, proper testing is required to make sure that configuration changes have the desired effect (and also to quantify that effect).

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  • Installation on SSD with Windows preinstalled

    - by ebbot
    I bought a laptop with this fancy SSD drive, fancy new UEFI aso. I figured at first Windows out Ubuntu in but after doing 3 DoA on 3 laptops in one day I realized that maybe keeping Windows could come in handy. So dual boot it is. And this is what I've got: Disk 1 - 500 Gb HD 300 Mb Windoze only says "Healthy" don't know what it's for. 600 Mb "Healthy (EFI partition)" 186.30 Gb NTFS "OS (C:)" "Healthy (Boot, Page File, Crash Dump, Primary Partition)" 258.45 Gb NTFS "Data (D:)" "Healthy" 20.00 Gb "Healthy (Recovery Partition)" Disk 2 - 24 Gb SSD 4.00 Gb "Healthy (OEM Partition)" 18.36 Gb "Healthy (Primary Partition)" So I'm not sure what the first partition on each drive does (the 300 Gb on the HD and the OEM Partition on the SSD. Nor do I know what Data (D:). I think the 2nd partition on the SSD is for some speedup of Windoze. I'm debating if I should shrink the OS (C:) drive to around 120 GB or so. Clear the Data (D:) and also use the whole SSD for Ubuntu. That would leave me 24 Gb for e.g. / on the SSD and some 320 Gb on the HD for /home and swap. Is this a reasonable setup? Do I need to configure fstab for the SSD differently to a HD?

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  • Step by Step: Remove/Sideline Preinstalled Windows 8, Install Ubuntu

    - by user207562
    I want Ubuntu as my primary/only operating system. Computer came with presumptive Pre-Installed Windows 8.(touch screen) Help. New Dell Inspiron 15r. Cannot install Ubuntu 12.04-03 or LTS. I need/request step by step instructions to remove Windows 8 or sideline Windows 8. (ie) BIOS settings I need to know: What to have; What settings; When to apply; Boot manager settings. UEFI. Etc. This should be easy, but I am mired in the Herpes that is Microsoft. I end up having a presumed dual boot that will not access Ubuntu. (ie) Step 1: Turn on computer. Step 2: F# to change ... to ... at Dell prompt... I want to use Ubuntu as my primary operating system or my only operating system.

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  • Quit job for another but current employer doesn't want to lose me. Would it be a bad idea to stay?

    - by Confused
    So I've handed in my notice at my current job as I've been offered a job at another company. However, my current employer doesn't want to lose me and they want to know what I want to stay. I mostly enjoy working there so I'd be open to negiotiation. The new job was an unexpected opportunity that presented itself. Such things I'd be looking for are: Better computers for developers Opportunity to work from home occasionally Improved internet access (e.g. able to download software, no keyword blocking) Chance to work on other technologies than my primary (we do have projects on other technologies) Pay increase (though this isn't my primary motivation) I found out that some of these were already in progress when I handed in my notice :( Is it ever a good idea to remain at a company after you've resigned? What if they meet all my conditions and alter my contract accordingly? Will I burn my bridges at the new company (I've already told them I'd accept their offer)? Update: Thanks for the answers. Quite a mixed bag which was interesting. Anyway, just so you know, I've chosen to stay at my current company. So far, it definately feels like the right decision. Guess I won't know for a few months whether is was though.

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  • Poor performance after reinstalling to a USB drive

    - by anonymous
    I am currently running Ubuntu 11.10 off of a SanDisk 16GB USB. I installed it using a Live USB with the following partition configuration: 6GB Primary /dos FAT32 5GB Logical / ext4 5GB Logical /home ext4 I don't have a hard disk, and don't see myself getting one anytime soon. I rely solely on this 16GB, and two other 4GB USBs, one of which I used as the LiveUSB. I bring the USBs around, and even use the install at work. I previously used an install that used a swap file. It functioned fine for the most part, save for a few slow moments, but I came across this post, and it got me thinking about my USB's life, so I reinstalled with the current config. My problem now is that it is slower. Applications like Firefox would hang more often. In my previous setup (the automatically partitioned setup), Firefox would start hanging if I was running an unzip or install task on the same partition as /. Now however, it would hang if I had another window open i.e. the system settings window. My guess is that it may have something to do with the swap file or the install being on a Logical partition rather than a Primary partition, but I don't know. Any insight as to why it has slowed down?

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  • Video quality too bad while playing (any) videos in Intel GM965/GL960 Integrated Graphics Controller Ubuntu 12.04

    - by Sukhdev
    I have searched blogs and forums, installed several drivers, but can't find a solution that can provide equivalent video quality as that of Windows 7. Kindly help. Video quality specially color is too bad while playing with any media player. Configuration details are: Ubuntu - 12.04 Intel Corporation Mobile GM965/GL960 Integrated The results of the following commands are a) sudo lspci | grep VGA 00:02.0 VGA compatible controller: Intel Corporation Mobile GM965/GL960 Integrated Graphics Controller (primary) (rev 0c) b) find /dev -group video /dev/fb0 /dev/dri/card0 /dev/dri/controlD64 /dev/agpgart c) glxinfo | grep -i vendor server glx vendor string: SGI client glx vendor string: ATI OpenGL vendor string: Tungsten Graphics, Inc d) sudo lshw -C video *-display:0 description: VGA compatible controller product: Mobile GM965/GL960 Integrated Graphics Controller (primary) vendor: Intel Corporation physical id: 2 bus info: pci@0000:00:02.0 version: 0c width: 64 bits clock: 33MHz capabilities: msi pm vga_controller bus_master cap_list rom configuration: driver=i915 latency=0 resources: irq:44 memory:fea00000-feafffff memory:e0000000-efffffff ioport:efe8(size=8) *-display:1 UNCLAIMED description: Display controller product: Mobile GM965/GL960 Integrated Graphics Controller (secondary) vendor: Intel Corporation physical id: 2.1 bus info: pci@0000:00:02.1 version: 0c width: 64 bits clock: 33MHz capabilities: pm bus_master cap_list configuration: latency=0 resources: memory:feb00000-febfffff I have spent days installing various drivers, and then un-installing but can't come up with a solution. Please help.

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  • ??GoldenGate Replicat?HANDLECOLLISIONS??

    - by Liu Maclean(???)
    HANDLECOLLISIONS?????goldengate????????REPLICAT??,???????????????????,???????????????????????????,??????????????????????????reperror????????discard??,????????????????,??????(????error mapping????,???????discard??),??????????????;?????????????????,????????? ??HANDLECOLLISIONS?????: target??delete??(missing delete),??????????discardfile target??update??(missing update) ????????=» update???INSERT ,???????????? ?????????=» ??????????discardfile ????????????target??,???replicat???UPDATE?????????????? ??1 target??delete??(missing delete) : C:\Users\ML>sqlplus / as sysdba SQL*Plus: Release 11.2.0.3.0 Production on Tue Sep 18 13:38:03 2012 Copyright (c) 1982, 2011, Oracle. All rights reserved. Connected to: Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production With the Partitioning, OLAP, Data Mining and Real Application Testing options SQL> conn sender/oracle Connected. SQL> create table handlec(t1 int primary key,t2 int); Table created. SQL> insert into handlec values(1,2); 1 row created. SQL> insert into handlec values(3,2); 1 row created. SQL> insert into handlec values(4,2); 1 row created. SQL> commit; Commit complete. SQL> select * from handlec; T1 T2 ---------- ---------- 1 2 3 2 4 2 target : SQL> conn receiver/oracle Connected. SQL> create table handlec(t1 int primary key,t2 int); Table created. SQL> insert into handlec values(1,2); 1 row created. SQL> commit; SQL> select * from handlec; T1 T2 ---------- ---------- 1 2 SQL> GGSCI (XIANGBLI-CN) 1> alter extract load2 , begin now EXTRACT altered. GGSCI (XIANGBLI-CN) 4> alter replicat rep2, begin now REPLICAT altered. GGSCI (XIANGBLI-CN) 13> add trandata sender.* Logging of supplemental redo data enabled for table SENDER.HANDLEC. Logging of supplemental redo log data is already enabled for table SENDER.TV. GGSCI (XIANGBLI-CN) 14> start mgr MGR is already running. GGSCI (XIANGBLI-CN) 15> start er * Sending START request to MANAGER ... EXTRACT LOAD2 starting Sending START request to MANAGER ... REPLICAT REP2 starting GGSCI (XIANGBLI-CN) 16> info all Program Status Group Lag at Chkpt Time Since Chkpt MANAGER RUNNING EXTRACT RUNNING LOAD2 00:00:00 00:00:01 REPLICAT RUNNING REP2 00:00:00 00:00:08 ***SOURCE?????TARGET????? SQL> delete handlec where t1=3; 1 row deleted. SQL> commit; Commit complete. ??SQL error 1403??,REPLICAT ABORT 2012-09-18 13:45:48 WARNING OGG-01004 Aborted grouped transaction on 'RECEIVER.HANDLEC', Database error 1403 (OCI Error ORA-01403: no data found, SQL ). 2012-09-18 13:45:48 WARNING OGG-01003 Repositioning to rba 1091 in seqno 3. 2012-09-18 13:45:48 WARNING OGG-01154 SQL error 1403 mapping SENDER.HANDLEC to RECEIVER.HANDLEC OCI Error ORA-01403: no data found, SQL . 2012-09-18 13:45:48 WARNING OGG-01003 Repositioning to rba 1091 in seqno 3. Source Context : SourceModule : [er.errors] SourceID : [er/errors.cpp] SourceFunction : [take_rep_err_action] SourceLine : [623] ThreadBacktrace : [8] elements : [D:\ogg\V34342-01\gglog.dll(??1CContextItem@@UEAA@XZ+0x3272) [0x000000018010BDD2]] : [D:\ogg\V34342-01\gglog.dll(?_MSG_ERR_MAP_TO_TANDEM_FAILED@@YAPEAVCMessage@@PEAVCSourceContext@@AEBV?$CQualDBObjName@$00@ggapp@gglib@ggs@@1W4MessageDisposition@CMessageFactory@@@Z+0x138) [0x00000001800AD508]] : [D:\ogg\V34342-01\replicat.exe(ERCALLBACK+0x6e1e) [0x0000000140099D5E]] : [D:\ogg\V34342-01\replicat.exe(shutdownMonitoring+0x4411) [0x00000001400C9BE1]] : [D:\ogg\V34342-01\replicat.exe(shutdownMonitoring+0x289cd) [0x00000001400EE19D]] : [D:\ogg\V34342-01\replicat.exe(CommonLexerNewSSD+0x9440) [0x00000001402AE980]] : [C:\windows\system32\kernel32.dll(BaseThreadInitThunk+0xd) [0x000000007733652D]] : [C:\windows\SYSTEM32\ntdll.dll(RtlUserThreadStart+0x21) [0x000000007746C521]] 2012-09-18 13:45:48 ERROR OGG-01296 Error mapping from SENDER.HANDLEC to RECEIVER.HANDLEC. *********************************************************************** * ** Run Time Statistics ** * *********************************************************************** Last record for the last committed transaction is the following: ___________________________________________________________________ Trail name : D:\ogg\V34342-01\ex\ze000003 Hdr-Ind : E (x45) Partition : . (x04) UndoFlag : . (x00) BeforeAfter: B (x42) RecLength : 9 (x0009) IO Time : 2012-09-18 13:45:38.000000 IOType : 3 (x03) OrigNode : 255 (xff) TransInd : . (x03) FormatType : R (x52) SyskeyLen : 0 (x00) Incomplete : . (x00) AuditRBA : 44 AuditPos : 3337232 Continued : N (x00) RecCount : 1 (x01) 2012-09-18 13:45:38.000000 Delete Len 9 RBA 1091 Name: SENDER.HANDLEC ___________________________________________________________________ Reading D:\ogg\V34342-01\ex\ze000003, current RBA 1091, 0 records Report at 2012-09-18 13:45:48 (activity since 2012-09-18 13:45:48) From Table SENDER.HANDLEC to RECEIVER.HANDLEC: # inserts: 0 # updates: 0 # deletes: 0 # discards: 1 Last log location read: FILE: D:\ogg\V34342-01\ex\ze000003 SEQNO: 3 RBA: 1091 TIMESTAMP: 2012-09-18 13:45:38.000000 EOF: NO READERR: 0 2012-09-18 13:45:48 ERROR OGG-01668 PROCESS ABENDING. 2012-09-18 13:45:48 INFO OGG-01237 Trace file D:\ogg\V34342-01\REP_TRACE1.TRC closed. 2012-09-18 13:45:48 INFO OGG-01237 Trace file D:\ogg\V34342-01\REP_TRACE2.TRC closed. CACHE OBJECT MANAGER statistics CACHE MANAGER VM USAGE vm current = 0 vm anon queues = 0 vm anon in use = 0 vm file = 0 vm used max = 0 ==> CACHE BALANCED CACHE CONFIGURATION cache size = 2G cache force paging = 3.41G buffer min = 64K buffer highwater = 8M pageout eligible size = 8M ================================================================================ ??skiptransaction???????? GGSCI (XIANGBLI-CN) 18> start rep2 skiptransaction Sending START request to MANAGER ... REPLICAT REP2 starting ??2 target??update??(missing update),???????? : ???????, ??source????????? SQL> update handlec set t1=5 where t1=4; 1 row updated. SQL> commit; Commit complete. ???target ????(miss update)??????? Database error 1403+OGG-01296 2012-09-18 13:49:30 WARNING OGG-01004 Aborted grouped transaction on 'RECEIVER.HANDLEC', Database error 1403 (OCI Error ORA-01403: no data found, SQL <UPDATE "RECEIVER"."HANDLEC" SET "T1" = :a1 WHERE "T1" = :b0>). 2012-09-18 13:49:30 WARNING OGG-01003 Repositioning to rba 1218 in seqno 3. 2012-09-18 13:49:30 WARNING OGG-01003 Repositioning to rba 1218 in seqno 3. Source Context : SourceModule : [er.errors] SourceID : [er/errors.cpp] SourceFunction : [take_rep_err_action] SourceLine : [623] ThreadBacktrace : [8] elements : [D:\ogg\V34342-01\gglog.dll(??1CContextItem@@UEAA@XZ+0x3272) [0x000000018010BDD2]] : [D:\ogg\V34342-01\gglog.dll(?_MSG_ERR_MAP_TO_TANDEM_FAILED@@YAPEAVCMessage@@PEAVCSourceContext@@AEBV?$CQualDBObjName@$00@ggapp@gglib@ggs@@1W4MessageDisposition@CMessageFactory@@@Z+0x138) [0x00000001800AD508]] : [D:\ogg\V34342-01\replicat.exe(ERCALLBACK+0x6e1e) [0x0000000140099D5E]] : [D:\ogg\V34342-01\replicat.exe(shutdownMonitoring+0x4411) [0x00000001400C9BE1]] : [D:\ogg\V34342-01\replicat.exe(shutdownMonitoring+0x289cd) [0x00000001400EE19D]] : [D:\ogg\V34342-01\replicat.exe(CommonLexerNewSSD+0x9440) [0x00000001402AE980]] : [C:\windows\system32\kernel32.dll(BaseThreadInitThunk+0xd) [0x000000007733652D]] : [C:\windows\SYSTEM32\ntdll.dll(RtlUserThreadStart+0x21) [0x000000007746C521]] 2012-09-18 13:49:30 ERROR OGG-01296 Error mapping from SENDER.HANDLEC to RECEIVER.HANDLEC. ??HANDLECOLLISIONS?,rep??????????discard?? GGSCI (XIANGBLI-CN) 23> view params rep2 replicat rep2 userid receiver , password oracle trace ./rep_trace1.trc trace2 ./rep_trace2.trc ASSUMETARGETDEFS HANDLECOLLISIONS map sender.*, target receiver.*; GGSCI (XIANGBLI-CN) 18> start rep2 SQL> select * from handlec; T1 T2 ---------- ---------- 1 2 5 ????T1=5 T2 NULL?????? ,??update?????????????,??replicat??????????????update????????????????,?????T2 ?NULL ,????????????EXTRACT??PKUPDATE??? ????????FETCHOPTIONS FETCHPKUPDATECOLS ????????EXTRACT?????,???EXTRACT? ????extract???????????? ??????: SQL> conn receiver/oracle Connected. SQL> select * from handlec; T1 T2 ---------- ---------- 1 2 10 100 5 20 200 SQL> delete handlec where t1=5; 1 row deleted. SQL> commit; Commit complete. SQL> select * from handlec; T1 T2 ---------- ---------- 1 2 10 100 20 200 SQL> conn sender/oracle Connected. SQL> update handlec set t1=t1+1000 where t1=5; 1 row updated. SQL> commit; Commit complete. SQL> conn receiver/oracle Connected. SQL> SQL> SQL> select * from handlec; T1 T2 ---------- ---------- 1 2 10 100 20 200 1005 2 ???????FETCHOPTIONS FETCHPKUPDATECOLS??????redo image???trail?,????primary key?????HANDLECOLLISIONS????target??????????? ??3 ????????????target??,???replicat???UPDATE??????????????: *** TARGET SQL> conn receiver/oracle Connected. SQL> select * from handlec; T1 T2 ---------- ---------- 1 2 10 9 5 target????? t1=10 t2=9??? ,????source???(10,100)??? >>SOURCE SQL> insert into handlec values(10,100); 1 row created. SQL> commit; >>TARGET SQL> select * from handlec; T1 T2 ---------- ---------- 1 2 10 100 5 ???????source?insert??,???target???????????????HANDLECOLLISIONS?REPLICAT???UPDATE??????COLUMNS ?? HANDLECOLLISIONS?????goldengate????????REPLICAT??,???????????????????,???????????????????????????,??????????????????????????reperror????????discard??,????????????????,??????,??????????????;?????????????????,????????? ??HANDLECOLLISIONS?????: target??delete??(missing delete),??????????discardfile target??update??(missing update) ????????=» update???INSERT ,???????????? ?????????=» ??????????discardfile ????????????target??,???replicat???UPDATE?????????????? ?:???????????Insert/Delete??,????????????????Replicat?????abend,????? ???????????,??target??HANDLECOLLISIONS??update??,?????INSERT??????,???????????????,FETCHOPTIONS FETCHPKUPDATECOLS??????redo image???trail?,????primary key?????HANDLECOLLISIONS????target??????????? ??????send ??????HANDLECOLLISIONS GGSCI (XIANGBLI-CN) 29> send rep2, NOHANDLECOLLISIONS Sending NOHANDLECOLLISIONS request to REPLICAT REP2 ... REP2 NOHANDLECOLLISIONS set for 1 tables and 0 wildcard entries

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  • Linq-to-XML query to select specific sub-element based on additional criteria

    - by BrianLy
    My current LINQ query and example XML are below. What I'd like to do is select the primary email address from the email-addresses element into the User.Email property. The type element under the email-address element is set to primary when this is true. There may be more than one element under the email-addresses but only one will be marked primary. What is the simplest approach to take here? Current Linq Query (User.Email is currently empty): var users = from response in xdoc.Descendants("response") where response.Element("id") != null select new User { Id = (string)response.Element("id"), Name = (string)response.Element("full-name"), Email = (string)response.Element("email-addresses"), JobTitle = (string)response.Element("job-title"), NetworkId = (string)response.Element("network-id"), Type = (string)response.Element("type") }; Example XML: <?xml version="1.0" encoding="UTF-8"?> <response> <response> <contact> <phone-numbers/> <im> <provider></provider> <username></username> </im> <email-addresses> <email-address> <type>primary</type> <address>[email protected]</address> </email-address> </email-addresses> </contact> <job-title>Account Manager</job-title> <type>user</type> <expertise nil="true"></expertise> <summary nil="true"></summary> <kids-names nil="true"></kids-names> <location nil="true"></location> <guid nil="true"></guid> <timezone>Eastern Time (US &amp; Canada)</timezone> <network-name>Domain</network-name> <full-name>Alice</full-name> <network-id>79629</network-id> <stats> <followers>2</followers> <updates>4</updates> <following>3</following> </stats> <mugshot-url> https://assets3.yammer.com/images/no_photo_small.gif</mugshot-url> <previous-companies/> <birth-date></birth-date> <name>alice</name> <web-url>https://www.yammer.com/domain.com/users/alice</web-url> <interests nil="true"></interests> <state>active</state> <external-urls/> <url>https://www.yammer.com/api/v1/users/1089943</url> <network-domains> <network-domain>domain.com</network-domain> </network-domains> <id>1089943</id> <schools/> <hire-date nil="true"></hire-date> <significant-other nil="true"></significant-other> </response> <response> <contact> <phone-numbers/> <im> <provider></provider> <username></username> </im> <email-addresses> <email-address> <type>primary</type> <address>[email protected]</address> </email-address> </email-addresses> </contact> <job-title>Office Manager</job-title> <type>user</type> <expertise nil="true"></expertise> <summary nil="true"></summary> <kids-names nil="true"></kids-names> <location nil="true"></location> <guid nil="true"></guid> <timezone>Eastern Time (US &amp; Canada)</timezone> <network-name>Domain</network-name> <full-name>Bill</full-name> <network-id>79629</network-id> <stats> <followers>3</followers> <updates>1</updates> <following>1</following> </stats> <mugshot-url> https://assets3.yammer.com/images/no_photo_small.gif</mugshot-url> <previous-companies/> <birth-date></birth-date> <name>bill</name> <web-url>https://www.yammer.com/domain.com/users/bill</web-url> <interests nil="true"></interests> <state>active</state> <external-urls/> <url>https://www.yammer.com/api/v1/users/1089920</url> <network-domains> <network-domain>domain.com</network-domain> </network-domains> <id>1089920</id> <schools/> <hire-date nil="true"></hire-date> <significant-other nil="true"></significant-other> </response> </response>

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  • Using HTML 5 SessionState to save rendered Page Content

    - by Rick Strahl
    HTML 5 SessionState and LocalStorage are very useful and super easy to use to manage client side state. For building rich client side or SPA style applications it's a vital feature to be able to cache user data as well as HTML content in order to swap pages in and out of the browser's DOM. What might not be so obvious is that you can also use the sessionState and localStorage objects even in classic server rendered HTML applications to provide caching features between pages. These APIs have been around for a long time and are supported by most relatively modern browsers and even all the way back to IE8, so you can use them safely in your Web applications. SessionState and LocalStorage are easy The APIs that make up sessionState and localStorage are very simple. Both object feature the same API interface which  is a simple, string based key value store that has getItem, setItem, removeitem, clear and  key methods. The objects are also pseudo array objects and so can be iterated like an array with  a length property and you have array indexers to set and get values with. Basic usage  for storing and retrieval looks like this (using sessionStorage, but the syntax is the same for localStorage - just switch the objects):// set var lastAccess = new Date().getTime(); if (sessionStorage) sessionStorage.setItem("myapp_time", lastAccess.toString()); // retrieve in another page or on a refresh var time = null; if (sessionStorage) time = sessionStorage.getItem("myapp_time"); if (time) time = new Date(time * 1); else time = new Date(); sessionState stores data that is browser session specific and that has a liftetime of the active browser session or window. Shut down the browser or tab and the storage goes away. localStorage uses the same API interface, but the lifetime of the data is permanently stored in the browsers storage area until deleted via code or by clearing out browser cookies (not the cache). Both sessionStorage and localStorage space is limited. The spec is ambiguous about this - supposedly sessionStorage should allow for unlimited size, but it appears that most WebKit browsers support only 2.5mb for either object. This means you have to be careful what you store especially since other applications might be running on the same domain and also use the storage mechanisms. That said 2.5mb worth of character data is quite a bit and would go a long way. The easiest way to get a feel for how sessionState and localStorage work is to look at a simple example. You can go check out the following example online in Plunker: http://plnkr.co/edit/0ICotzkoPjHaWa70GlRZ?p=preview which looks like this: Plunker is an online HTML/JavaScript editor that lets you write and run Javascript code and similar to JsFiddle, but a bit cleaner to work in IMHO (thanks to John Papa for turning me on to it). The sample has two text boxes with counts that update session/local storage every time you click the related button. The counts are 'cached' in Session and Local storage. The point of these examples is that both counters survive full page reloads, and the LocalStorage counter survives a complete browser shutdown and restart. Go ahead and try it out by clicking the Reload button after updating both counters and then shutting down the browser completely and going back to the same URL (with the same browser). What you should see is that reloads leave both counters intact at the counted values, while a browser restart will leave only the local storage counter intact. The code to deal with the SessionStorage (and LocalStorage not shown here) in the example is isolated into a couple of wrapper methods to simplify the code: function getSessionCount() { var count = 0; if (sessionStorage) { var count = sessionStorage.getItem("ss_count"); count = !count ? 0 : count * 1; } $("#txtSession").val(count); return count; } function setSessionCount(count) { if (sessionStorage) sessionStorage.setItem("ss_count", count.toString()); } These two functions essentially load and store a session counter value. The two key methods used here are: sessionStorage.getItem(key); sessionStorage.setItem(key,stringVal); Note that the value given to setItem and return by getItem has to be a string. If you pass another type you get an error. Don't let that limit you though - you can easily enough store JSON data in a variable so it's quite possible to pass complex objects and store them into a single sessionStorage value:var user = { name: "Rick", id="ricks", level=8 } sessionStorage.setItem("app_user",JSON.stringify(user)); to retrieve it:var user = sessionStorage.getItem("app_user"); if (user) user = JSON.parse(user); Simple! If you're using the Chrome Developer Tools (F12) you can also check out the session and local storage state on the Resource tab:   You can also use this tool to refresh or remove entries from storage. What we just looked at is a purely client side implementation where a couple of counters are stored. For rich client centric AJAX applications sessionStorage and localStorage provide a very nice and simple API to store application state while the application is running. But you can also use these storage mechanisms to manage server centric HTML applications when you combine server rendering with some JavaScript to perform client side data caching. You can both store some state information and data on the client (ie. store a JSON object and carry it forth between server rendered HTML requests) or you can use it for good old HTTP based caching where some rendered HTML is saved and then restored later. Let's look at the latter with a real life example. Why do I need Client-side Page Caching for Server Rendered HTML? I don't know about you, but in a lot of my existing server driven applications I have lists that display a fair amount of data. Typically these lists contain links to then drill down into more specific data either for viewing or editing. You can then click on a link and go off to a detail page that provides more concise content. So far so good. But now you're done with the detail page and need to get back to the list, so you click on a 'bread crumbs trail' or an application level 'back to list' button and… …you end up back at the top of the list - the scroll position, the current selection in some cases even filters conditions - all gone with the wind. You've left behind the state of the list and are starting from scratch in your browsing of the list from the top. Not cool! Sound familiar? This a pretty common scenario with server rendered HTML content where it's so common to display lists to drill into, only to lose state in the process of returning back to the original list. Look at just about any traditional forums application, or even StackOverFlow to see what I mean here. Scroll down a bit to look at a post or entry, drill in then use the bread crumbs or tab to go back… In some cases returning to the top of a list is not a big deal. On StackOverFlow that sort of works because content is turning around so quickly you probably want to actually look at the top posts. Not always though - if you're browsing through a list of search topics you're interested in and drill in there's no way back to that position. Essentially anytime you're actively browsing the items in the list, that's when state becomes important and if it's not handled the user experience can be really disrupting. Content Caching If you're building client centric SPA style applications this is a fairly easy to solve problem - you tend to render the list once and then update the page content to overlay the detail content, only hiding the list temporarily until it's used again later. It's relatively easy to accomplish this simply by hiding content on the page and later making it visible again. But if you use server rendered content, hanging on to all the detail like filters, selections and scroll position is not quite as easy. Or is it??? This is where sessionStorage comes in handy. What if we just save the rendered content of a previous page, and then restore it when we return to this page based on a special flag that tells us to use the cached version? Let's see how we can do this. A real World Use Case Recently my local ISP asked me to help out with updating an ancient classifieds application. They had a very busy, local classifieds app that was originally an ASP classic application. The old app was - wait for it: frames based - and even though I lobbied against it, the decision was made to keep the frames based layout to allow rapid browsing of the hundreds of posts that are made on a daily basis. The primary reason they wanted this was precisely for the ability to quickly browse content item by item. While I personally hate working with Frames, I have to admit that the UI actually works well with the frames layout as long as you're running on a large desktop screen. You can check out the frames based desktop site here: http://classifieds.gorge.net/ However when I rebuilt the app I also added a secondary view that doesn't use frames. The main reason for this of course was for mobile displays which work horribly with frames. So there's a somewhat mobile friendly interface to the interface, which ditches the frames and uses some responsive design tweaking for mobile capable operation: http://classifeds.gorge.net/mobile  (or browse the base url with your browser width under 800px)   Here's what the mobile, non-frames view looks like:   As you can see this means that the list of classifieds posts now is a list and there's a separate page for drilling down into the item. And of course… originally we ran into that usability issue I mentioned earlier where the browse, view detail, go back to the list cycle resulted in lost list state. Originally in mobile mode you scrolled through the list, found an item to look at and drilled in to display the item detail. Then you clicked back to the list and BAM - you've lost your place. Because there are so many items added on a daily basis the full list is never fully loaded, but rather there's a "Load Additional Listings"  entry at the button. Not only did we originally lose our place when coming back to the list, but any 'additionally loaded' items are no longer there because the list was now rendering  as if it was the first page hit. The additional listings, and any filters, the selection of an item all were lost. Major Suckage! Using Client SessionStorage to cache Server Rendered Content To work around this problem I decided to cache the rendered page content from the list in SessionStorage. Anytime the list renders or is updated with Load Additional Listings, the page HTML is cached and stored in Session Storage. Any back links from the detail page or the login or write entry forms then point back to the list page with a back=true query string parameter. If the server side sees this parameter it doesn't render the part of the page that is cached. Instead the client side code retrieves the data from the sessionState cache and simply inserts it into the page. It sounds pretty simple, and the overall the process is really easy, but there are a few gotchas that I'll discuss in a minute. But first let's look at the implementation. Let's start with the server side here because that'll give a quick idea of the doc structure. As I mentioned the server renders data from an ASP.NET MVC view. On the list page when returning to the list page from the display page (or a host of other pages) looks like this: https://classifieds.gorge.net/list?back=True The query string value is a flag, that indicates whether the server should render the HTML. Here's what the top level MVC Razor view for the list page looks like:@model MessageListViewModel @{ ViewBag.Title = "Classified Listing"; bool isBack = !string.IsNullOrEmpty(Request.QueryString["back"]); } <form method="post" action="@Url.Action("list")"> <div id="SizingContainer"> @if (!isBack) { @Html.Partial("List_CommandBar_Partial", Model) <div id="PostItemContainer" class="scrollbox" xstyle="-webkit-overflow-scrolling: touch;"> @Html.Partial("List_Items_Partial", Model) @if (Model.RequireLoadEntry) { <div class="postitem loadpostitems" style="padding: 15px;"> <div id="LoadProgress" class="smallprogressright"></div> <div class="control-progress"> Load additional listings... </div> </div> } </div> } </div> </form> As you can see the query string triggers a conditional block that if set is simply not rendered. The content inside of #SizingContainer basically holds  the entire page's HTML sans the headers and scripts, but including the filter options and menu at the top. In this case this makes good sense - in other situations the fact that the menu or filter options might be dynamically updated might make you only cache the list rather than essentially the entire page. In this particular instance all of the content works and produces the proper result as both the list along with any filter conditions in the form inputs are restored. Ok, let's move on to the client. On the client there are two page level functions that deal with saving and restoring state. Like the counter example I showed earlier, I like to wrap the logic to save and restore values from sessionState into a separate function because they are almost always used in several places.page.saveData = function(id) { if (!sessionStorage) return; var data = { id: id, scroll: $("#PostItemContainer").scrollTop(), html: $("#SizingContainer").html() }; sessionStorage.setItem("list_html",JSON.stringify(data)); }; page.restoreData = function() { if (!sessionStorage) return; var data = sessionStorage.getItem("list_html"); if (!data) return null; return JSON.parse(data); }; The data that is saved is an object which contains an ID which is the selected element when the user clicks and a scroll position. These two values are used to reset the scroll position when the data is used from the cache. Finally the html from the #SizingContainer element is stored, which makes for the bulk of the document's HTML. In this application the HTML captured could be a substantial bit of data. If you recall, I mentioned that the server side code renders a small chunk of data initially and then gets more data if the user reads through the first 50 or so items. The rest of the items retrieved can be rather sizable. Other than the JSON deserialization that's Ok. Since I'm using SessionStorage the storage space has no immediate limits. Next is the core logic to handle saving and restoring the page state. At first though this would seem pretty simple, and in some cases it might be, but as the following code demonstrates there are a few gotchas to watch out for. Here's the relevant code I use to save and restore:$( function() { … var isBack = getUrlEncodedKey("back", location.href); if (isBack) { // remove the back key from URL setUrlEncodedKey("back", "", location.href); var data = page.restoreData(); // restore from sessionState if (!data) { // no data - force redisplay of the server side default list window.location = "list"; return; } $("#SizingContainer").html(data.html); var el = $(".postitem[data-id=" + data.id + "]"); $(".postitem").removeClass("highlight"); el.addClass("highlight"); $("#PostItemContainer").scrollTop(data.scroll); setTimeout(function() { el.removeClass("highlight"); }, 2500); } else if (window.noFrames) page.saveData(null); // save when page loads $("#SizingContainer").on("click", ".postitem", function() { var id = $(this).attr("data-id"); if (!id) return true; if (window.noFrames) page.saveData(id); var contentFrame = window.parent.frames["Content"]; if (contentFrame) contentFrame.location.href = "show/" + id; else window.location.href = "show/" + id; return false; }); … The code starts out by checking for the back query string flag which triggers restoring from the client cache. If cached the cached data structure is read from sessionStorage. It's important here to check if data was returned. If the user had back=true on the querystring but there is no cached data, he likely bookmarked this page or otherwise shut down the browser and came back to this URL. In that case the server didn't render any detail and we have no cached data, so all we can do is redirect to the original default list view using window.location. If we continued the page would render no data - so make sure to always check the cache retrieval result. Always! If there is data the it's loaded and the data.html data is restored back into the document by simply injecting the HTML back into the document's #SizingContainer element:$("#SizingContainer").html(data.html); It's that simple and it's quite quick even with a fully loaded list of additional items and on a phone. The actual HTML data is stored to the cache on every page load initially and then again when the user clicks on an element to navigate to a particular listing. The former ensures that the client cache always has something in it, and the latter updates with additional information for the selected element. For the click handling I use a data-id attribute on the list item (.postitem) in the list and retrieve the id from that. That id is then used to navigate to the actual entry as well as storing that Id value in the saved cached data. The id is used to reset the selection by searching for the data-id value in the restored elements. The overall process of this save/restore process is pretty straight forward and it doesn't require a bunch of code, yet it yields a huge improvement in the usability of the site on mobile devices (or anybody who uses the non-frames view). Some things to watch out for As easy as it conceptually seems to simply store and retrieve cached content, you have to be quite aware what type of content you are caching. The code above is all that's specific to cache/restore cycle and it works, but it took a few tweaks to the rest of the script code and server code to make it all work. There were a few gotchas that weren't immediately obvious. Here are a few things to pay attention to: Event Handling Logic Timing of manipulating DOM events Inline Script Code Bookmarking to the Cache Url when no cache exists Do you have inline script code in your HTML? That script code isn't going to run if you restore from cache and simply assign or it may not run at the time you think it would normally in the DOM rendering cycle. JavaScript Event Hookups The biggest issue I ran into with this approach almost immediately is that originally I had various static event handlers hooked up to various UI elements that are now cached. If you have an event handler like:$("#btnSearch").click( function() {…}); that works fine when the page loads with server rendered HTML, but that code breaks when you now load the HTML from cache. Why? Because the elements you're trying to hook those events to may not actually be there - yet. Luckily there's an easy workaround for this by using deferred events. With jQuery you can use the .on() event handler instead:$("#SelectionContainer").on("click","#btnSearch", function() {…}); which monitors a parent element for the events and checks for the inner selector elements to handle events on. This effectively defers to runtime event binding, so as more items are added to the document bindings still work. For any cached content use deferred events. Timing of manipulating DOM Elements Along the same lines make sure that your DOM manipulation code follows the code that loads the cached content into the page so that you don't manipulate DOM elements that don't exist just yet. Ideally you'll want to check for the condition to restore cached content towards the top of your script code, but that can be tricky if you have components or other logic that might not all run in a straight line. Inline Script Code Here's another small problem I ran into: I use a DateTime Picker widget I built a while back that relies on the jQuery date time picker. I also created a helper function that allows keyboard date navigation into it that uses JavaScript logic. Because MVC's limited 'object model' the only way to embed widget content into the page is through inline script. This code broken when I inserted the cached HTML into the page because the script code was not available when the component actually got injected into the page. As the last bullet - it's a matter of timing. There's no good work around for this - in my case I pulled out the jQuery date picker and relied on native <input type="date" /> logic instead - a better choice these days anyway, especially since this view is meant to be primarily to serve mobile devices which actually support date input through the browser (unlike desktop browsers of which only WebKit seems to support it). Bookmarking Cached Urls When you cache HTML content you have to make a decision whether you cache on the client and also not render that same content on the server. In the Classifieds app I didn't render server side content so if the user comes to the page with back=True and there is no cached content I have to a have a Plan B. Typically this happens when somebody ends up bookmarking the back URL. The easiest and safest solution for this scenario is to ALWAYS check the cache result to make sure it exists and if not have a safe URL to go back to - in this case to the plain uncached list URL which amounts to effectively redirecting. This seems really obvious in hindsight, but it's easy to overlook and not see a problem until much later, when it's not obvious at all why the page is not rendering anything. Don't use <body> to replace Content Since we're practically replacing all the HTML in the page it may seem tempting to simply replace the HTML content of the <body> tag. Don't. The body tag usually contains key things that should stay in the page and be there when it loads. Specifically script tags and elements and possibly other embedded content. It's best to create a top level DOM element specifically as a placeholder container for your cached content and wrap just around the actual content you want to replace. In the app above the #SizingContainer is that container. Other Approaches The approach I've used for this application is kind of specific to the existing server rendered application we're running and so it's just one approach you can take with caching. However for server rendered content caching this is a pattern I've used in a few apps to retrofit some client caching into list displays. In this application I took the path of least resistance to the existing server rendering logic. Here are a few other ways that come to mind: Using Partial HTML Rendering via AJAXInstead of rendering the page initially on the server, the page would load empty and the client would render the UI by retrieving the respective HTML and embedding it into the page from a Partial View. This effectively makes the initial rendering and the cached rendering logic identical and removes the server having to decide whether this request needs to be rendered or not (ie. not checking for a back=true switch). All the logic related to caching is made on the client in this case. Using JSON Data and Client RenderingThe hardcore client option is to do the whole UI SPA style and pull data from the server and then use client rendering or databinding to pull the data down and render using templates or client side databinding with knockout/angular et al. As with the Partial Rendering approach the advantage is that there's no difference in the logic between pulling the data from cache or rendering from scratch other than the initial check for the cache request. Of course if the app is a  full on SPA app, then caching may not be required even - the list could just stay in memory and be hidden and reactivated. I'm sure there are a number of other ways this can be handled as well especially using  AJAX. AJAX rendering might simplify the logic, but it also complicates search engine optimization since there's no content loaded initially. So there are always tradeoffs and it's important to look at all angles before deciding on any sort of caching solution in general. State of the Session SessionState and LocalStorage are easy to use in client code and can be integrated even with server centric applications to provide nice caching features of content and data. In this post I've shown a very specific scenario of storing HTML content for the purpose of remembering list view data and state and making the browsing experience for lists a bit more friendly, especially if there's dynamically loaded content involved. If you haven't played with sessionStorage or localStorage I encourage you to give it a try. There's a lot of cool stuff that you can do with this beyond the specific scenario I've covered here… Resources Overview of localStorage (also applies to sessionStorage) Web Storage Compatibility Modernizr Test Suite© Rick Strahl, West Wind Technologies, 2005-2013Posted in JavaScript  HTML5  ASP.NET  MVC   Tweet !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs"); (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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  • Minecraft Style Chunk building problem

    - by David Torrey
    I'm having some problems with speed in my chunk engine. I timed it out, and in its current state it takes a total ~5 seconds per chunk to fill each face's list. I have a check to see if each face of a block is visible and if it is not visible, it skips it and moves on. I'm using a dictionary (unordered map) because it makes sense memorywise to just not have an entry if there is no block. I've tracked my problem down to testing if there is an entry, and accessing an entry if it does exist. If I remove the tests to see if there is an entry in the dictionary for an adjacent block, or if the block type itself is seethrough, it runs within about 2-4 milliseconds. so here's my question: Is there a faster way to check for an entry in a dictionary than .ContainsKey()? As an aside, I tried TryGetValue() and it doesn't really help with the speed that much. If I remove the ContainsKey() and keep the test where it does the IsSeeThrough for each block, it halves the time, but it's still about 2-3 seconds. It only drops to 2-4ms if I remove BOTH checks. Here is my code: using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; using System.Runtime.InteropServices; using OpenTK; using OpenTK.Graphics.OpenGL; using System.Drawing; namespace Anabelle_Lee { public enum BlockEnum { air = 0, dirt = 1, } [StructLayout(LayoutKind.Sequential,Pack=1)] public struct Coordinates<T1> { public T1 x; public T1 y; public T1 z; public override string ToString() { return "(" + x + "," + y + "," + z + ") : " + typeof(T1); } } public struct Sides<T1> { public T1 left; public T1 right; public T1 top; public T1 bottom; public T1 front; public T1 back; } public class Block { public int blockType; public bool SeeThrough() { switch (blockType) { case 0: return true; } return false ; } public override string ToString() { return ((BlockEnum)(blockType)).ToString(); } } class Chunk { private Dictionary<Coordinates<byte>, Block> mChunkData; //stores the block data private Sides<List<Coordinates<byte>>> mVBOVertexBuffer; private Sides<int> mVBOHandle; //private bool mIsChanged; private const byte mCHUNKSIZE = 16; public Chunk() { } public void InitializeChunk() { //create VBO references #if DEBUG Console.WriteLine ("Initializing Chunk"); #endif mChunkData = new Dictionary<Coordinates<byte> , Block>(); //mIsChanged = true; GL.GenBuffers(1, out mVBOHandle.left); GL.GenBuffers(1, out mVBOHandle.right); GL.GenBuffers(1, out mVBOHandle.top); GL.GenBuffers(1, out mVBOHandle.bottom); GL.GenBuffers(1, out mVBOHandle.front); GL.GenBuffers(1, out mVBOHandle.back); //make new list of vertexes for each face mVBOVertexBuffer.top = new List<Coordinates<byte>>(); mVBOVertexBuffer.bottom = new List<Coordinates<byte>>(); mVBOVertexBuffer.left = new List<Coordinates<byte>>(); mVBOVertexBuffer.right = new List<Coordinates<byte>>(); mVBOVertexBuffer.front = new List<Coordinates<byte>>(); mVBOVertexBuffer.back = new List<Coordinates<byte>>(); #if DEBUG Console.WriteLine("Chunk Initialized"); #endif } public void GenerateChunk() { #if DEBUG Console.WriteLine("Generating Chunk"); #endif for (byte i = 0; i < mCHUNKSIZE; i++) { for (byte j = 0; j < mCHUNKSIZE; j++) { for (byte k = 0; k < mCHUNKSIZE; k++) { Random blockLoc = new Random(); Coordinates<byte> randChunk = new Coordinates<byte> { x = i, y = j, z = k }; mChunkData.Add(randChunk, new Block()); mChunkData[randChunk].blockType = blockLoc.Next(0, 1); } } } #if DEBUG Console.WriteLine("Chunk Generated"); #endif } public void DeleteChunk() { //delete VBO references #if DEBUG Console.WriteLine("Deleting Chunk"); #endif GL.DeleteBuffers(1, ref mVBOHandle.left); GL.DeleteBuffers(1, ref mVBOHandle.right); GL.DeleteBuffers(1, ref mVBOHandle.top); GL.DeleteBuffers(1, ref mVBOHandle.bottom); GL.DeleteBuffers(1, ref mVBOHandle.front); GL.DeleteBuffers(1, ref mVBOHandle.back); //clear all vertex buffers ClearPolyLists(); #if DEBUG Console.WriteLine("Chunk Deleted"); #endif } public void UpdateChunk() { #if DEBUG Console.WriteLine("Updating Chunk"); #endif ClearPolyLists(); //prepare buffers //for every entry in mChunkData map foreach(KeyValuePair<Coordinates<byte>,Block> feBlockData in mChunkData) { Coordinates<byte> checkBlock = new Coordinates<byte> { x = feBlockData.Key.x, y = feBlockData.Key.y, z = feBlockData.Key.z }; //check for polygonson the left side of the cube if (checkBlock.x > 0) { //check to see if there is a key for current x - 1. if not, add the vector if (!IsVisible(checkBlock.x - 1, checkBlock.y, checkBlock.z)) { //add polygon AddPoly(checkBlock.x, checkBlock.y, checkBlock.z, mVBOHandle.left); } } else { //polygon is far left and should be added AddPoly(checkBlock.x, checkBlock.y, checkBlock.z, mVBOHandle.left); } //check for polygons on the right side of the cube if (checkBlock.x < mCHUNKSIZE - 1) { if (!IsVisible(checkBlock.x + 1, checkBlock.y, checkBlock.z)) { //add poly AddPoly(checkBlock.x, checkBlock.y, checkBlock.z, mVBOHandle.right); } } else { //poly for right add AddPoly(checkBlock.x, checkBlock.y, checkBlock.z, mVBOHandle.right); } if (checkBlock.y > 0) { //check to see if there is a key for current x - 1. if not, add the vector if (!IsVisible(checkBlock.x, checkBlock.y - 1, checkBlock.z)) { //add polygon AddPoly(checkBlock.x, checkBlock.y, checkBlock.z, mVBOHandle.bottom); } } else { //polygon is far left and should be added AddPoly(checkBlock.x, checkBlock.y, checkBlock.z, mVBOHandle.bottom); } //check for polygons on the right side of the cube if (checkBlock.y < mCHUNKSIZE - 1) { if (!IsVisible(checkBlock.x, checkBlock.y + 1, checkBlock.z)) { //add poly AddPoly(checkBlock.x, checkBlock.y, checkBlock.z, mVBOHandle.top); } } else { //poly for right add AddPoly(checkBlock.x, checkBlock.y, checkBlock.z, mVBOHandle.top); } if (checkBlock.z > 0) { //check to see if there is a key for current x - 1. if not, add the vector if (!IsVisible(checkBlock.x, checkBlock.y, checkBlock.z - 1)) { //add polygon AddPoly(checkBlock.x, checkBlock.y, checkBlock.z, mVBOHandle.back); } } else { //polygon is far left and should be added AddPoly(checkBlock.x, checkBlock.y, checkBlock.z, mVBOHandle.back); } //check for polygons on the right side of the cube if (checkBlock.z < mCHUNKSIZE - 1) { if (!IsVisible(checkBlock.x, checkBlock.y, checkBlock.z + 1)) { //add poly AddPoly(checkBlock.x, checkBlock.y, checkBlock.z, mVBOHandle.front); } } else { //poly for right add AddPoly(checkBlock.x, checkBlock.y, checkBlock.z, mVBOHandle.front); } } BuildBuffers(); #if DEBUG Console.WriteLine("Chunk Updated"); #endif } public void RenderChunk() { } public void LoadChunk() { #if DEBUG Console.WriteLine("Loading Chunk"); #endif #if DEBUG Console.WriteLine("Chunk Deleted"); #endif } public void SaveChunk() { #if DEBUG Console.WriteLine("Saving Chunk"); #endif #if DEBUG Console.WriteLine("Chunk Saved"); #endif } private bool IsVisible(int pX,int pY,int pZ) { Block testBlock; Coordinates<byte> checkBlock = new Coordinates<byte> { x = Convert.ToByte(pX), y = Convert.ToByte(pY), z = Convert.ToByte(pZ) }; if (mChunkData.TryGetValue(checkBlock,out testBlock )) //if data exists { if (testBlock.SeeThrough() == true) //if existing data is not seethrough { return true; } } return true; } private void AddPoly(byte pX, byte pY, byte pZ, int BufferSide) { //create temp array GL.BindBuffer(BufferTarget.ArrayBuffer, BufferSide); if (BufferSide == mVBOHandle.front) { //front face mVBOVertexBuffer.front.Add(new Coordinates<byte> { x = (byte)(pX) , y = (byte)(pY + 1), z = (byte)(pZ + 1) }); mVBOVertexBuffer.front.Add(new Coordinates<byte> { x = (byte)(pX) , y = (byte)(pY) , z = (byte)(pZ + 1) }); mVBOVertexBuffer.front.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY) , z = (byte)(pZ + 1) }); mVBOVertexBuffer.front.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY) , z = (byte)(pZ + 1) }); mVBOVertexBuffer.front.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY + 1), z = (byte)(pZ + 1) }); mVBOVertexBuffer.front.Add(new Coordinates<byte> { x = (byte)(pX) , y = (byte)(pY + 1), z = (byte)(pZ + 1) }); } else if (BufferSide == mVBOHandle.right) { //back face mVBOVertexBuffer.back.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY + 1), z = (byte)(pZ) }); mVBOVertexBuffer.back.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY) , z = (byte)(pZ) }); mVBOVertexBuffer.back.Add(new Coordinates<byte> { x = (byte)(pX) , y = (byte)(pY) , z = (byte)(pZ) }); mVBOVertexBuffer.back.Add(new Coordinates<byte> { x = (byte)(pX) , y = (byte)(pY) , z = (byte)(pZ) }); mVBOVertexBuffer.back.Add(new Coordinates<byte> { x = (byte)(pX) , y = (byte)(pY + 1), z = (byte)(pZ) }); mVBOVertexBuffer.back.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY + 1), z = (byte)(pZ) }); } else if (BufferSide == mVBOHandle.top) { //left face mVBOVertexBuffer.left.Add(new Coordinates<byte> { x = (byte)(pX), y = (byte)(pY + 1), z = (byte)(pZ) }); mVBOVertexBuffer.left.Add(new Coordinates<byte> { x = (byte)(pX), y = (byte)(pY) , z = (byte)(pZ) }); mVBOVertexBuffer.left.Add(new Coordinates<byte> { x = (byte)(pX), y = (byte)(pY) , z = (byte)(pZ + 1) }); mVBOVertexBuffer.left.Add(new Coordinates<byte> { x = (byte)(pX), y = (byte)(pY) , z = (byte)(pZ + 1) }); mVBOVertexBuffer.left.Add(new Coordinates<byte> { x = (byte)(pX), y = (byte)(pY + 1), z = (byte)(pZ + 1) }); mVBOVertexBuffer.left.Add(new Coordinates<byte> { x = (byte)(pX), y = (byte)(pY + 1), z = (byte)(pZ) }); } else if (BufferSide == mVBOHandle.bottom) { //right face mVBOVertexBuffer.right.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY + 1), z = (byte)(pZ + 1) }); mVBOVertexBuffer.right.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY) , z = (byte)(pZ + 1) }); mVBOVertexBuffer.right.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY) , z = (byte)(pZ) }); mVBOVertexBuffer.right.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY) , z = (byte)(pZ) }); mVBOVertexBuffer.right.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY + 1), z = (byte)(pZ) }); mVBOVertexBuffer.right.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY + 1), z = (byte)(pZ + 1) }); } else if (BufferSide == mVBOHandle.front) { //top face mVBOVertexBuffer.top.Add(new Coordinates<byte> { x = (byte)(pX) , y = (byte)(pY + 1), z = (byte)(pZ) }); mVBOVertexBuffer.top.Add(new Coordinates<byte> { x = (byte)(pX) , y = (byte)(pY + 1), z = (byte)(pZ + 1) }); mVBOVertexBuffer.top.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY + 1), z = (byte)(pZ + 1) }); mVBOVertexBuffer.top.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY + 1), z = (byte)(pZ + 1) }); mVBOVertexBuffer.top.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY + 1), z = (byte)(pZ) }); mVBOVertexBuffer.top.Add(new Coordinates<byte> { x = (byte)(pX) , y = (byte)(pY + 1), z = (byte)(pZ) }); } else if (BufferSide == mVBOHandle.back) { //bottom face mVBOVertexBuffer.bottom.Add(new Coordinates<byte> { x = (byte)(pX) , y = (byte)(pY), z = (byte)(pZ + 1) }); mVBOVertexBuffer.bottom.Add(new Coordinates<byte> { x = (byte)(pX) , y = (byte)(pY), z = (byte)(pZ) }); mVBOVertexBuffer.bottom.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY), z = (byte)(pZ) }); mVBOVertexBuffer.bottom.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY), z = (byte)(pZ) }); mVBOVertexBuffer.bottom.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY), z = (byte)(pZ + 1) }); mVBOVertexBuffer.bottom.Add(new Coordinates<byte> { x = (byte)(pX) , y = (byte)(pY), z = (byte)(pZ + 1) }); } } private void BuildBuffers() { #if DEBUG Console.WriteLine("Building Chunk Buffers"); #endif GL.BindBuffer(BufferTarget.ArrayBuffer, mVBOHandle.front); GL.BufferData(BufferTarget.ArrayBuffer, (IntPtr)(Marshal.SizeOf(new Coordinates<byte>()) * mVBOVertexBuffer.front.Count), mVBOVertexBuffer.front.ToArray(), BufferUsageHint.StaticDraw); GL.BindBuffer(BufferTarget.ArrayBuffer, mVBOHandle.back); GL.BufferData(BufferTarget.ArrayBuffer, (IntPtr)(Marshal.SizeOf(new Coordinates<byte>()) * mVBOVertexBuffer.back.Count), mVBOVertexBuffer.back.ToArray(), BufferUsageHint.StaticDraw); GL.BindBuffer(BufferTarget.ArrayBuffer, mVBOHandle.left); GL.BufferData(BufferTarget.ArrayBuffer, (IntPtr)(Marshal.SizeOf(new Coordinates<byte>()) * mVBOVertexBuffer.left.Count), mVBOVertexBuffer.left.ToArray(), BufferUsageHint.StaticDraw); GL.BindBuffer(BufferTarget.ArrayBuffer, mVBOHandle.right); GL.BufferData(BufferTarget.ArrayBuffer, (IntPtr)(Marshal.SizeOf(new Coordinates<byte>()) * mVBOVertexBuffer.right.Count), mVBOVertexBuffer.right.ToArray(), BufferUsageHint.StaticDraw); GL.BindBuffer(BufferTarget.ArrayBuffer, mVBOHandle.top); GL.BufferData(BufferTarget.ArrayBuffer, (IntPtr)(Marshal.SizeOf(new Coordinates<byte>()) * mVBOVertexBuffer.top.Count), mVBOVertexBuffer.top.ToArray(), BufferUsageHint.StaticDraw); GL.BindBuffer(BufferTarget.ArrayBuffer, mVBOHandle.bottom); GL.BufferData(BufferTarget.ArrayBuffer, (IntPtr)(Marshal.SizeOf(new Coordinates<byte>()) * mVBOVertexBuffer.bottom.Count), mVBOVertexBuffer.bottom.ToArray(), BufferUsageHint.StaticDraw); GL.BindBuffer(BufferTarget.ArrayBuffer,0); #if DEBUG Console.WriteLine("Chunk Buffers Built"); #endif } private void ClearPolyLists() { #if DEBUG Console.WriteLine("Clearing Polygon Lists"); #endif mVBOVertexBuffer.top.Clear(); mVBOVertexBuffer.bottom.Clear(); mVBOVertexBuffer.left.Clear(); mVBOVertexBuffer.right.Clear(); mVBOVertexBuffer.front.Clear(); mVBOVertexBuffer.back.Clear(); #if DEBUG Console.WriteLine("Polygon Lists Cleared"); #endif } }//END CLASS }//END NAMESPACE

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  • Inside the Concurrent Collections: ConcurrentDictionary

    - by Simon Cooper
    Using locks to implement a thread-safe collection is rather like using a sledgehammer - unsubtle, easy to understand, and tends to make any other tool redundant. Unlike the previous two collections I looked at, ConcurrentStack and ConcurrentQueue, ConcurrentDictionary uses locks quite heavily. However, it is careful to wield locks only where necessary to ensure that concurrency is maximised. This will, by necessity, be a higher-level look than my other posts in this series, as there is quite a lot of code and logic in ConcurrentDictionary. Therefore, I do recommend that you have ConcurrentDictionary open in a decompiler to have a look at all the details that I skip over. The problem with locks There's several things to bear in mind when using locks, as encapsulated by the lock keyword in C# and the System.Threading.Monitor class in .NET (if you're unsure as to what lock does in C#, I briefly covered it in my first post in the series): Locks block threads The most obvious problem is that threads waiting on a lock can't do any work at all. No preparatory work, no 'optimistic' work like in ConcurrentQueue and ConcurrentStack, nothing. It sits there, waiting to be unblocked. This is bad if you're trying to maximise concurrency. Locks are slow Whereas most of the methods on the Interlocked class can be compiled down to a single CPU instruction, ensuring atomicity at the hardware level, taking out a lock requires some heavy lifting by the CLR and the operating system. There's quite a bit of work required to take out a lock, block other threads, and wake them up again. If locks are used heavily, this impacts performance. Deadlocks When using locks there's always the possibility of a deadlock - two threads, each holding a lock, each trying to aquire the other's lock. Fortunately, this can be avoided with careful programming and structured lock-taking, as we'll see. So, it's important to minimise where locks are used to maximise the concurrency and performance of the collection. Implementation As you might expect, ConcurrentDictionary is similar in basic implementation to the non-concurrent Dictionary, which I studied in a previous post. I'll be using some concepts introduced there, so I recommend you have a quick read of it. So, if you were implementing a thread-safe dictionary, what would you do? The naive implementation is to simply have a single lock around all methods accessing the dictionary. This would work, but doesn't allow much concurrency. Fortunately, the bucketing used by Dictionary allows a simple but effective improvement to this - one lock per bucket. This allows different threads modifying different buckets to do so in parallel. Any thread making changes to the contents of a bucket takes the lock for that bucket, ensuring those changes are thread-safe. The method that maps each bucket to a lock is the GetBucketAndLockNo method: private void GetBucketAndLockNo( int hashcode, out int bucketNo, out int lockNo, int bucketCount) { // the bucket number is the hashcode (without the initial sign bit) // modulo the number of buckets bucketNo = (hashcode & 0x7fffffff) % bucketCount; // and the lock number is the bucket number modulo the number of locks lockNo = bucketNo % m_locks.Length; } However, this does require some changes to how the buckets are implemented. The 'implicit' linked list within a single backing array used by the non-concurrent Dictionary adds a dependency between separate buckets, as every bucket uses the same backing array. Instead, ConcurrentDictionary uses a strict linked list on each bucket: This ensures that each bucket is entirely separate from all other buckets; adding or removing an item from a bucket is independent to any changes to other buckets. Modifying the dictionary All the operations on the dictionary follow the same basic pattern: void AlterBucket(TKey key, ...) { int bucketNo, lockNo; 1: GetBucketAndLockNo( key.GetHashCode(), out bucketNo, out lockNo, m_buckets.Length); 2: lock (m_locks[lockNo]) { 3: Node headNode = m_buckets[bucketNo]; 4: Mutate the node linked list as appropriate } } For example, when adding another entry to the dictionary, you would iterate through the linked list to check whether the key exists already, and add the new entry as the head node. When removing items, you would find the entry to remove (if it exists), and remove the node from the linked list. Adding, updating, and removing items all follow this pattern. Performance issues There is a problem we have to address at this point. If the number of buckets in the dictionary is fixed in the constructor, then the performance will degrade from O(1) to O(n) when a large number of items are added to the dictionary. As more and more items get added to the linked lists in each bucket, the lookup operations will spend most of their time traversing a linear linked list. To fix this, the buckets array has to be resized once the number of items in each bucket has gone over a certain limit. (In ConcurrentDictionary this limit is when the size of the largest bucket is greater than the number of buckets for each lock. This check is done at the end of the TryAddInternal method.) Resizing the bucket array and re-hashing everything affects every bucket in the collection. Therefore, this operation needs to take out every lock in the collection. Taking out mutiple locks at once inevitably summons the spectre of the deadlock; two threads each hold a lock, and each trying to acquire the other lock. How can we eliminate this? Simple - ensure that threads never try to 'swap' locks in this fashion. When taking out multiple locks, always take them out in the same order, and always take out all the locks you need before starting to release them. In ConcurrentDictionary, this is controlled by the AcquireLocks, AcquireAllLocks and ReleaseLocks methods. Locks are always taken out and released in the order they are in the m_locks array, and locks are all released right at the end of the method in a finally block. At this point, it's worth pointing out that the locks array is never re-assigned, even when the buckets array is increased in size. The number of locks is fixed in the constructor by the concurrencyLevel parameter. This simplifies programming the locks; you don't have to check if the locks array has changed or been re-assigned before taking out a lock object. And you can be sure that when a thread takes out a lock, another thread isn't going to re-assign the lock array. This would create a new series of lock objects, thus allowing another thread to ignore the existing locks (and any threads controlling them), breaking thread-safety. Consequences of growing the array Just because we're using locks doesn't mean that race conditions aren't a problem. We can see this by looking at the GrowTable method. The operation of this method can be boiled down to: private void GrowTable(Node[] buckets) { try { 1: Acquire first lock in the locks array // this causes any other thread trying to take out // all the locks to block because the first lock in the array // is always the one taken out first // check if another thread has already resized the buckets array // while we were waiting to acquire the first lock 2: if (buckets != m_buckets) return; 3: Calculate the new size of the backing array 4: Node[] array = new array[size]; 5: Acquire all the remaining locks 6: Re-hash the contents of the existing buckets into array 7: m_buckets = array; } finally { 8: Release all locks } } As you can see, there's already a check for a race condition at step 2, for the case when the GrowTable method is called twice in quick succession on two separate threads. One will successfully resize the buckets array (blocking the second in the meantime), when the second thread is unblocked it'll see that the array has already been resized & exit without doing anything. There is another case we need to consider; looking back at the AlterBucket method above, consider the following situation: Thread 1 calls AlterBucket; step 1 is executed to get the bucket and lock numbers. Thread 2 calls GrowTable and executes steps 1-5; thread 1 is blocked when it tries to take out the lock in step 2. Thread 2 re-hashes everything, re-assigns the buckets array, and releases all the locks (steps 6-8). Thread 1 is unblocked and continues executing, but the calculated bucket and lock numbers are no longer valid. Between calculating the correct bucket and lock number and taking out the lock, another thread has changed where everything is. Not exactly thread-safe. Well, a similar problem was solved in ConcurrentStack and ConcurrentQueue by storing a local copy of the state, doing the necessary calculations, then checking if that state is still valid. We can use a similar idea here: void AlterBucket(TKey key, ...) { while (true) { Node[] buckets = m_buckets; int bucketNo, lockNo; GetBucketAndLockNo( key.GetHashCode(), out bucketNo, out lockNo, buckets.Length); lock (m_locks[lockNo]) { // if the state has changed, go back to the start if (buckets != m_buckets) continue; Node headNode = m_buckets[bucketNo]; Mutate the node linked list as appropriate } break; } } TryGetValue and GetEnumerator And so, finally, we get onto TryGetValue and GetEnumerator. I've left these to the end because, well, they don't actually use any locks. How can this be? Whenever you change a bucket, you need to take out the corresponding lock, yes? Indeed you do. However, it is important to note that TryGetValue and GetEnumerator don't actually change anything. Just as immutable objects are, by definition, thread-safe, read-only operations don't need to take out a lock because they don't change anything. All lockless methods can happily iterate through the buckets and linked lists without worrying about locking anything. However, this does put restrictions on how the other methods operate. Because there could be another thread in the middle of reading the dictionary at any time (even if a lock is taken out), the dictionary has to be in a valid state at all times. Every change to state has to be made visible to other threads in a single atomic operation (all relevant variables are marked volatile to help with this). This restriction ensures that whatever the reading threads are doing, they never read the dictionary in an invalid state (eg items that should be in the collection temporarily removed from the linked list, or reading a node that has had it's key & value removed before the node itself has been removed from the linked list). Fortunately, all the operations needed to change the dictionary can be done in that way. Bucket resizes are made visible when the new array is assigned back to the m_buckets variable. Any additions or modifications to a node are done by creating a new node, then splicing it into the existing list using a single variable assignment. Node removals are simply done by re-assigning the node's m_next pointer. Because the dictionary can be changed by another thread during execution of the lockless methods, the GetEnumerator method is liable to return dirty reads - changes made to the dictionary after GetEnumerator was called, but before the enumeration got to that point in the dictionary. It's worth listing at this point which methods are lockless, and which take out all the locks in the dictionary to ensure they get a consistent view of the dictionary: Lockless: TryGetValue GetEnumerator The indexer getter ContainsKey Takes out every lock (lockfull?): Count IsEmpty Keys Values CopyTo ToArray Concurrent principles That covers the overall implementation of ConcurrentDictionary. I haven't even begun to scratch the surface of this sophisticated collection. That I leave to you. However, we've looked at enough to be able to extract some useful principles for concurrent programming: Partitioning When using locks, the work is partitioned into independant chunks, each with its own lock. Each partition can then be modified concurrently to other partitions. Ordered lock-taking When a method does need to control the entire collection, locks are taken and released in a fixed order to prevent deadlocks. Lockless reads Read operations that don't care about dirty reads don't take out any lock; the rest of the collection is implemented so that any reading thread always has a consistent view of the collection. That leads us to the final collection in this little series - ConcurrentBag. Lacking a non-concurrent analogy, it is quite different to any other collection in the class libraries. Prepare your thinking hats!

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  • .NET Code Evolution

    - by Alois Kraus
    Originally posted on: http://geekswithblogs.net/akraus1/archive/2013/07/24/153504.aspxAt my day job I do look at a lot of code written by other people. Most of the code is quite good and some is even a masterpiece. And there is also code which makes you think WTF… oh it was written by me. Hm not so bad after all. There are many excuses reasons for bad code. Most often it is time pressure followed by not enough ambition (who cares) or insufficient training. Normally I do care about code quality quite a lot which makes me a (perceived) slow worker who does write many tests and refines the code quite a lot because of the design deficiencies. Most of the deficiencies I do find by putting my design under stress while checking for invariants. It does also help a lot to step into the code with a debugger (sometimes also Windbg). I do this much more often when my tests are red. That way I do get a much better understanding what my code really does and not what I think it should be doing. This time I do want to show you how code can evolve over the years with different .NET Framework versions. Once there was  time where .NET 1.1 was new and many C++ programmers did switch over to get rid of not initialized pointers and memory leaks. There were also nice new data structures available such as the Hashtable which is fast lookup table with O(1) time complexity. All was good and much code was written since then. At 2005 a new version of the .NET Framework did arrive which did bring many new things like generics and new data structures. The “old” fashioned way of Hashtable were coming to an end and everyone used the new Dictionary<xx,xx> type instead which was type safe and faster because the object to type conversion (aka boxing) was no longer necessary. I think 95% of all Hashtables and dictionaries use string as key. Often it is convenient to ignore casing to make it easy to look up values which the user did enter. An often followed route is to convert the string to upper case before putting it into the Hashtable. Hashtable Table = new Hashtable(); void Add(string key, string value) { Table.Add(key.ToUpper(), value); } This is valid and working code but it has problems. First we can pass to the Hashtable a custom IEqualityComparer to do the string matching case insensitive. Second we can switch over to the now also old Dictionary type to become a little faster and we can keep the the original keys (not upper cased) in the dictionary. Dictionary<string, string> DictTable = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase); void AddDict(string key, string value) { DictTable.Add(key, value); } Many people do not user the other ctors of Dictionary because they do shy away from the overhead of writing their own comparer. They do not know that .NET has for strings already predefined comparers at hand which you can directly use. Today in the many core area we do use threads all over the place. Sometimes things break in subtle ways but most of the time it is sufficient to place a lock around the offender. Threading has become so mainstream that it may sound weird that in the year 2000 some guy got a huge incentive for the idea to reduce the time to process calibration data from 12 hours to 6 hours by using two threads on a dual core machine. Threading does make it easy to become faster at the expense of correctness. Correct and scalable multithreading can be arbitrarily hard to achieve depending on the problem you are trying to solve. Lets suppose we want to process millions of items with two threads and count the processed items processed by all threads. A typical beginners code might look like this: int Counter; void IJustLearnedToUseThreads() { var t1 = new Thread(ThreadWorkMethod); t1.Start(); var t2 = new Thread(ThreadWorkMethod); t2.Start(); t1.Join(); t2.Join(); if (Counter != 2 * Increments) throw new Exception("Hmm " + Counter + " != " + 2 * Increments); } const int Increments = 10 * 1000 * 1000; void ThreadWorkMethod() { for (int i = 0; i < Increments; i++) { Counter++; } } It does throw an exception with the message e.g. “Hmm 10.222.287 != 20.000.000” and does never finish. The code does fail because the assumption that Counter++ is an atomic operation is wrong. The ++ operator is just a shortcut for Counter = Counter + 1 This does involve reading the counter from a memory location into the CPU, incrementing value on the CPU and writing the new value back to the memory location. When we do look at the generated assembly code we will see only inc dword ptr [ecx+10h] which is only one instruction. Yes it is one instruction but it is not atomic. All modern CPUs have several layers of caches (L1,L2,L3) which try to hide the fact how slow actual main memory accesses are. Since cache is just another word for redundant copy it can happen that one CPU does read a value from main memory into the cache, modifies it and write it back to the main memory. The problem is that at least the L1 cache is not shared between CPUs so it can happen that one CPU does make changes to values which did change in meantime in the main memory. From the exception you can see we did increment the value 20 million times but half of the changes were lost because we did overwrite the already changed value from the other thread. This is a very common case and people do learn to protect their  data with proper locking.   void Intermediate() { var time = Stopwatch.StartNew(); Action acc = ThreadWorkMethod_Intermediate; var ar1 = acc.BeginInvoke(null, null); var ar2 = acc.BeginInvoke(null, null); ar1.AsyncWaitHandle.WaitOne(); ar2.AsyncWaitHandle.WaitOne(); if (Counter != 2 * Increments) throw new Exception(String.Format("Hmm {0:N0} != {1:N0}", Counter, 2 * Increments)); Console.WriteLine("Intermediate did take: {0:F1}s", time.Elapsed.TotalSeconds); } void ThreadWorkMethod_Intermediate() { for (int i = 0; i < Increments; i++) { lock (this) { Counter++; } } } This is better and does use the .NET Threadpool to get rid of manual thread management. It does give the expected result but it can result in deadlocks because you do lock on this. This is in general a bad idea since it can lead to deadlocks when other threads use your class instance as lock object. It is therefore recommended to create a private object as lock object to ensure that nobody else can lock your lock object. When you read more about threading you will read about lock free algorithms. They are nice and can improve performance quite a lot but you need to pay close attention to the CLR memory model. It does make quite weak guarantees in general but it can still work because your CPU architecture does give you more invariants than the CLR memory model. For a simple counter there is an easy lock free alternative present with the Interlocked class in .NET. As a general rule you should not try to write lock free algos since most likely you will fail to get it right on all CPU architectures. void Experienced() { var time = Stopwatch.StartNew(); Task t1 = Task.Factory.StartNew(ThreadWorkMethod_Experienced); Task t2 = Task.Factory.StartNew(ThreadWorkMethod_Experienced); t1.Wait(); t2.Wait(); if (Counter != 2 * Increments) throw new Exception(String.Format("Hmm {0:N0} != {1:N0}", Counter, 2 * Increments)); Console.WriteLine("Experienced did take: {0:F1}s", time.Elapsed.TotalSeconds); } void ThreadWorkMethod_Experienced() { for (int i = 0; i < Increments; i++) { Interlocked.Increment(ref Counter); } } Since time does move forward we do not use threads explicitly anymore but the much nicer Task abstraction which was introduced with .NET 4 at 2010. It is educational to look at the generated assembly code. The Interlocked.Increment method must be called which does wondrous things right? Lets see: lock inc dword ptr [eax] The first thing to note that there is no method call at all. Why? Because the JIT compiler does know very well about CPU intrinsic functions. Atomic operations which do lock the memory bus to prevent other processors to read stale values are such things. Second: This is the same increment call prefixed with a lock instruction. The only reason for the existence of the Interlocked class is that the JIT compiler can compile it to the matching CPU intrinsic functions which can not only increment by one but can also do an add, exchange and a combined compare and exchange operation. But be warned that the correct usage of its methods can be tricky. If you try to be clever and look a the generated IL code and try to reason about its efficiency you will fail. Only the generated machine code counts. Is this the best code we can write? Perhaps. It is nice and clean. But can we make it any faster? Lets see how good we are doing currently. Level Time in s IJustLearnedToUseThreads Flawed Code Intermediate 1,5 (lock) Experienced 0,3 (Interlocked.Increment) Master 0,1 (1,0 for int[2]) That lock free thing is really a nice thing. But if you read more about CPU cache, cache coherency, false sharing you can do even better. int[] Counters = new int[12]; // Cache line size is 64 bytes on my machine with an 8 way associative cache try for yourself e.g. 64 on more modern CPUs void Master() { var time = Stopwatch.StartNew(); Task t1 = Task.Factory.StartNew(ThreadWorkMethod_Master, 0); Task t2 = Task.Factory.StartNew(ThreadWorkMethod_Master, Counters.Length - 1); t1.Wait(); t2.Wait(); Counter = Counters[0] + Counters[Counters.Length - 1]; if (Counter != 2 * Increments) throw new Exception(String.Format("Hmm {0:N0} != {1:N0}", Counter, 2 * Increments)); Console.WriteLine("Master did take: {0:F1}s", time.Elapsed.TotalSeconds); } void ThreadWorkMethod_Master(object number) { int index = (int) number; for (int i = 0; i < Increments; i++) { Counters[index]++; } } The key insight here is to use for each core its own value. But if you simply use simply an integer array of two items, one for each core and add the items at the end you will be much slower than the lock free version (factor 3). Each CPU core has its own cache line size which is something in the range of 16-256 bytes. When you do access a value from one location the CPU does not only fetch one value from main memory but a complete cache line (e.g. 16 bytes). This means that you do not pay for the next 15 bytes when you access them. This can lead to dramatic performance improvements and non obvious code which is faster although it does have many more memory reads than another algorithm. So what have we done here? We have started with correct code but it was lacking knowledge how to use the .NET Base Class Libraries optimally. Then we did try to get fancy and used threads for the first time and failed. Our next try was better but it still had non obvious issues (lock object exposed to the outside). Knowledge has increased further and we have found a lock free version of our counter which is a nice and clean way which is a perfectly valid solution. The last example is only here to show you how you can get most out of threading by paying close attention to your used data structures and CPU cache coherency. Although we are working in a virtual execution environment in a high level language with automatic memory management it does pay off to know the details down to the assembly level. Only if you continue to learn and to dig deeper you can come up with solutions no one else was even considering. I have studied particle physics which does help at the digging deeper part. Have you ever tried to solve Quantum Chromodynamics equations? Compared to that the rest must be easy ;-). Although I am no longer working in the Science field I take pride in discovering non obvious things. This can be a very hard to find bug or a new way to restructure data to make something 10 times faster. Now I need to get some sleep ….

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