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  • In which object should I implement wait()/notify()?

    - by Christopher Francisco
    I'm working in an Android project with multithreading. Basically I have to wait to the server to respond before sending more data. The data sending task is delimited by the flag boolean hasServerResponded so the Thread will loop infinitely without doing anything until the flag becomes true. Since this boolean isn't declared as volatile (yet), and also looping without doing anything wastes resources, I thought maybe I should use AtomicBoolean and also implement wait() / notify() mechanism. Should I use the AtomicBoolean object notify() and wait() methods or should I create a lock Object?

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  • Unresponsive Script window pops up all the time now. Why and what to do?

    - by Christopher Jewell
    I don't know that it's for the exact same script each time, it may be. A script on this page may be busy, or it may have stopped responding. You can stop the script now, or you can continue to see if the script will complete. Script: chrome://messenger/content/folderPane.js:721 This is in association with Thunderbird I think. This doesn't just happen after I've stepped away for a long time. It happens every time I click on anything. Things keep running that I'm clicking on. Just before this started as a constant problem, I was looking at addons etc, and something in Thunderbird deactivated an old or expired JavaScript. I clicked on the update for that and after a while I found the best choice on the list and clicked download. I don't know that anything happened with that and I moved away from addons etc area. The unresponsive script window started coming back all the time. Every time I clicked on something in Thunderbird and sometimes with Firefox. I turned off Firefox and restarted, but it didn't change. Shut down Firefox and computer restarted didn't change. The unresponsive script window is persistent now.

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  • Use two networks at the same time?

    - by Christopher
    I want to use Ubuntu 10.10 Server in a classroom, a computer lab whose bandwidth is provided by a local cable ISP. That's no problem, though the school network has an IP printer that I want to use. I cannot reach the printer through the cable Internet. But, I have two network cards. How is it possible to use both networks at once? eth0 (static 192.168.1.254) is plugged into a four-port router, 192.168.1.1. On the public side of the four-port router is Internet provided by the cable company. I also have the classroom workstations plugged into a switch. The switch is plugged into the four-port router. The whole classroom is wired into the cable Internet. The other NIC, eth1, could it be plugged into an Ethernet jack in the wall? It uses the school network, and I might receive by DHCP an IP address like 10.140.10.100, with the printer on maybe 10.120.50.10. I was thinking about installing the printer on the server so that it could be shared with the workstations. But how does this work? Can I just plug eth1 into the school network and access both LANs? Thanks for any insight

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  • How are components properly instantiated and used in XNA 4.0?

    - by Christopher Horenstein
    I am creating a simple input component to hold on to actions and key states, and a short history of the last ten or so states. The idea is that everything that is interested in input will ask this component for the latest input, and I am wondering where I should create it. I am also wondering how I should create components that are specific to my game objects - I envision them as variables, but then how do their Update/Draw methods get called? What I'm trying to ask is, what are the best practices for adding components to the proper collections? Right now I've added my input component in the main Game class that XNA creates when everything is first initialized, saying something along the lines of this.Components.Add(new InputComponent(this)), which looks a little odd to me, and I'd still want to hang onto that reference so I can ask it things. An answer to my input component's dilemma is great, but also I'm guessing there is a right way to do this in general in XNA.

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  • How can I write byte[] to socket outputstream and specify the end of file?

    - by Christopher Francisco
    I've googled 2 days straight and I can't find how to do this. I have an open stream between client and server, and client will send a JSON string (encrypted to bytes) to the server each 3 to 5 seconds. How can I write to the Socket OutputStream so that I can read each JSON string in the server. I'm guessing I need to specify some kind of end of file or something, but can't find any info on how to achieve this.

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  • Profiling NetBeans 7.0 Beta 2 and Reporting Problems

    - by christopher.jones
    With NetBeans 7.0 recently going into Beta 2 phase, now is the time to test it out properly and report issues. The development team has been squashing bugs, including memory issues with the PHP bundle.There are some great new PHP related features in NetBeans 7.0, so you know you want to try it out.If you identify something wrong with NetBeans, please report it following the guidelines http://wiki.netbeans.org/IssueReportingGuidelinesDepending on the issues, data to attach to the report is mentioned on: http://wiki.netbeans.org/FaqLogMessagesFile and http://wiki.netbeans.org/FaqProfileMeNowIf you have a memory issue then a memory dump would also be useful. Run the jmap tool for this. There is some background information on http://wiki.netbeans.org/FaqMemoryDump. Here's how I used it.First I set my environment to match the JDK used by NetBeans. In my case I am using a nightly build so the JDK is in the configuration file under $HOME/netbeans-dev-201102210501:$ egrep netbeans_jdkhome $HOME/netbeans-dev-201102210501/etc/netbeans.conf netbeans_jdkhome="/home/cjones/src/jdk1.6.0_24" $ export JAVA_HOME=/home/cjones/src/jdk1.6.0_24 $ export PATH=$JAVA_HOME/bin:$PATH Next, I found the correct process number to examine:$ ps -ef | egrep 'netbeans|jdk'cjones   23230     1  0 16:07 ?        00:00:00 /bin/bash /home/cjones/netbeans-cjones   23438 23230  2 16:07 ?        00:00:09 /home/cjones/src/jdk1.6.0_24/binFinally I used the parent JDK process as the jmap argument:$ jmap -histo:live 23438 num     #instances         #bytes  class name----------------------------------------------   1:         12075        9028656  [I   2:         49535        6581920  <constMethodKlass>   3:         49535        3964128  <methodKlass>   4:         80256        3840776  <symbolKlass>   5:         36093        3635336  [C   6:          5095        3341312  <constantPoolKlass>   7:          5095        2486016  <instanceKlassKlass>   8:          4325        1961432  <constantPoolCacheKlass>   9:         18729        1763976  [B  10:         59952        1438848  java.util.HashMap$Entry  . . .This histogram memory report will help identify the kind of memory issues you are seeing. It may not be as complete as an often tens of megabyte jmap -dump:live,file=/tmp/nbheap.log 23438 heap dump, but is much more easily attached to a bug report.If you want to keep up to date with NetBeans, nightly builds are at: http://bits.netbeans.org/download/trunk/nightly/latest/zip/

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  • Painfully Slow iPhone Backup?

    - by Christopher House
    And now for something completely different... For the past couple of weeks, I've not been able to sync my iPhone.  What happens is that I plug it in to my computer, start the sync and two hours later, iTunes shows it's about 75% complete.  After some googling, I tried a few things like deleting old backups, changing some settings, etc, but nothing seemed to help.  Tonight I decided I'd try deleting all the photos and videos on my phone.  Sure enough, that did the trick.  I'm now able to successfully sync in a reasonable amount of time.

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  • How to fix Xubuntu LightDM Theme after installing unity.

    - by Christopher
    After successfully installing Xubuntu 12.04.1 on my laptop, I decided to install Unity. That went OK but then I realized there was no themes. So then I installed the themes and artwork, and got a really bad surprise. My lightDM greeter was still Xubuntu like I wanted but the buttons where you choose the user are really tall and I have a purple computer as the icon above my computer name. How do I get back to the original Xubuntu configuration or edit the CSS while keeping Unity? I know where all of the files are but don't know which file to edit or which CSS property to modify. Packages Installed: unity unity-services unity-mail Then I Installed: ubuntu-artwork light-themes ubuntu-wallpapers-oneric ubuntu-wallpapers-precise

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  • GeoTrust SSL brand name used by re-sellers

    - by Christopher
    I feel like a I got the bait-and-switch from my web host provider since they advertise "GeoTrust SSL" for $99. I purchased it, thinking the certificate is issued from geotrust.com, but then I get an email from Comodo saying they are providing it. My host provider says they get a discount by using Comodo. I purchased the certificate with the understanding it would be issued by GeoTrust. I called the host provider and they said they usually expect it from GeoTrust, but someone from email support responded saying the product name is "GeoTrust SSL" but they use Comodo to get a discount. I think this is bogus and unfair trade practice. However, searching for "GeoTrust" on google brings up a ton of websites selling "GeoTrust" certificates. How can companies get away with this? Since the host provider is part of BBB I plan to inform my host to update the purchase page on their website to state clearly that... "This certicate is provided at a discount and may be issued by a provider other than GeoTrust.com, such as Comodo.com" Any feedback on this is appreciated.

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  • How do I get my folders back on my desktop?

    - by Christopher Allen
    Using the 12.04 version. This morning the Update Manager popped up, I clicked it and it said some items will be un-installed and some will be upgraded and new ones will be installed. I did it and restarted. On restart, I entered my password about 5 times and it said it was incorrect. I changed the shell from Gnome to Ubuntu and logged on then changed it back to Gnome and I was able to log on. However, all my folders on the screen are gone but they appear under Desktop in the Home folder. How do I get then back on the screen?

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  • Enforcing Constraints Upon Data Documents of Various Formats

    - by Christopher Berman
    This seems like the sort of problem that must have been solved elegantly long ago, but I haven't the foggiest how to google it and find it. Suppose you're maintaining a large legacy system, which has a large collection of data (tens of GB) of various formats, including XML and two different internal configuration formats. Suppose further that there are abstract rules governing the values these files may or may not contain. EXAMPLE: File A defines the raw, mathematical data pertaining to the aerodynamics of a car for consumption of the physics component of the system. File B contains certain values from File A in an easily accessible, XML hierarchy for consumption of a different component of the system. There exists, therefore, an abstract rule (or constraint) such that the values from File B must match the values from File A. This is probably the simplest constraint that can be specified, but in practice, the constraints between files can become very complicated indeed. What is the best method for managing these constraints between files of arbitrary formats, short of migrating it over to an RDBMS (which simply isn't feasible for the foreseeable future)? Has this problem been solved already? To be more specific, I would expect the solution to at least produce notifications of violated constraints; the solution need not resolve the constraints. ============================== Sample file structures File A (JeepWrangler2011.emv): MODEL JeepWrangler2011 { EsotericMathValueX 11.1 EsotericMathValueY 22.2 EsotericMathValueZ 33.3 } File B (JeepWrangler2011.xml): <model name="JeepWrangler2011"> <!--These values must correspond File A's EsotericMathValues--> <modelExtent x="11.1" y="22.2" z="33.3"/> [...] </model>

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  • Moving Day

    - by Christopher House
    I've decided that it's time for me to move on from Geeks with Blogs.  It's been a great platform but unforuntately I've not used it nearly as much as I should.  It's been over a year and a half since my last post.  It's not that I haven't had worthwhile stuff to post, it's more due to a lack of motivation.  Knowing how I work, I think part of the problem with me using GWB is that it's free.  If I don't use it, I don't feel like I'm wasting anything.  With that in mind, I've decided to move to a paid host in hopes that drives me to post more frequently.  My new blog is located at the following address:http://thirteendaysaweek.comIn the coming days and weeks I'll be working on moving my content to the new site and will leave posts here that redirect to the new site.

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  • Is it OK to write a programming language in Jython? [closed]

    - by Christopher
    I've been looking at the tools for writing a programming language and I had a bizarre idea. What If I wrote a full blown programming language in Jython? Is that a practical solution? Will distribution and bundling be a problem? Can that make or break the language's success? In other words, I'm asking if writing a programing language written in Jython is a practical solution for production enviroments?

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  • Exalogic 2.0.1 Tea Break Snippets - Scripting Asset Creation

    - by The Old Toxophilist
    So far in this series we have looked at creating asset within the EMOC BUI but the Exalogic 2.0.1 installation also provide the Iaas cli as an alternative to most of the common functionality available within EMOC. The IaaS cli interface provides access to the functions that are available to a user logged into the BUI with the CloudUser Role. As such not all functionality is available from the command line interface however having said that the IaaS cli provides all the functionality required to create the Assets within a specific Account (Tenure). Because these action are common and repeatable I decided to wrap the functionality within a simple script that takes a simple input file and creates the Asset. Following the Script through will show us the required steps needed to create the various Assets within an Account and hence I will work through the various functions within the script below describing the steps. You will note from the various steps within the script that it is designed to pause between actions allowing the proceeding action to complete. The reason for this is because we could swamp EMOC with a series of actions and may end up with a situation where we are trying to action a Volume attached before the creation of the vServer and Volume have completed. processAssets() This function simply reads through the passed input file identifying what assets need to be created. An example of the input file can be found below. It can be seen that the input file can be used to create Assets in multiple Accounts during a single run. The order of the entries define the functions that need to be actioned as follows: Input Command Iaas Actions Parameters Production:Connect akm-describe-accounts akm-create-access-key iaas-create-key-pair iaas-describe-vnets iaas-describe-vserver-types iaas-describe-server-templates Username Password Production:Create|vServer iaas-run-vserver vServer Name vServer Type Name Template Name Comma separated list of network names which the vServer will connect to. Comma separated list of IPs for the specified networks. Production:Create|Volume iaas-create-volume Volume Name Volume Size Production:Attach|Volume iaas-attach-volumes-to-vserver vServer Name Comma separated list of volume names Production:Disconnect iaas-delete-key-pair akm-delete-access-key None connectToAccount() It can be seen from the connectToAccount function that before we can execute any Asset creation we must first connect to the appropriate account. To do this we will need the ID associated with the Account. This can be found by executing the akm-describe-accounts cli command which will return a list of all Accounts and there IDs. Once we have the Account ID we generate and Access key using the akm-create-access-key command and then a keypair with the iaas-create-key-pair command. At this point we now have all the information we need to access the specific named account. createVServer() This function simply retrieved the information from the input line and then will create the vServer using the iaas-run-vserver cli command. Reading the function you will notice that it takes the various input names for vServer Type, Template and Networks and converts them into the appropriate IDs. The IaaS cli will not work directly with component names and hence all IDs need to be found. createVolume() Function that simply takes the Volume name and Size then executes the iaas-create-volume command to create the volume. attachVolume() Takes the name of the Volume, which we may have just created, and a Volume then identifies the appropriate IDs before assigning the Volume to the vServer with the iaas-attach-volumes-to-vserver. disconnectFromAccount() Once we have finished connecting to the Account we simply remove the key pair with iaas-delete-key-pair and the access key with akm-delete-access-key although it may be useful to keep this if ssh is required and you do not subsequently modify the sshd information to allow unsecured access. By default the key is required for ssh access when a vServer is created from the command-line. CreateAssets.sh 1 export OCCLI=/opt/sun/occli/bin 2 export IAAS_HOME=/opt/oracle/iaas/cli 3 export JAVA_HOME=/usr/java/latest 4 export IAAS_BASE_URL=https://127.0.0.1 5 export IAAS_ACCESS_KEY_FILE=iaas_access.key 6 export KEY_FILE=iaas_access.pub 7 #CloudUser used to create vServers & Volumes 8 export IAAS_USER=exaprod 9 export IAAS_PASSWORD_FILE=root.pwd 10 export KEY_NAME=cli.recreate 11 export INPUT_FILE=CreateAssets.in 12 13 export ACCOUNTS_FILE=accounts.out 14 export VOLUMES_FILE=volumes.out 15 export DISTGRPS_FILE=distgrp.out 16 export VNETS_FILE=vnets.out 17 export VSERVER_TYPES_FILE=vstype.out 18 export VSERVER_FILE=vserver.out 19 export VSERVER_TEMPLATES=template.out 20 export KEY_PAIRS=keypairs.out 21 22 PROCESSING_ACCOUNT="" 23 24 function cleanTempFiles() { 25 rm -f $ACCOUNTS_FILE $VOLUMES_FILE $DISTGRPS_FILE $VNETS_FILE $VSERVER_TYPES_FILE $VSERVER_FILE $VSERVER_TEMPLATES $KEY_PAIRS $IAAS_PASSWORD_FILE $KEY_FILE $IAAS_ACCESS_KEY_FILE 26 } 27 28 function connectToAccount() { 29 if [[ "$ACCOUNT" != "$PROCESSING_ACCOUNT" ]] 30 then 31 if [[ "" != "$PROCESSING_ACCOUNT" ]] 32 then 33 $IAAS_HOME/bin/iaas-delete-key-pair --key-name $KEY_NAME --access-key-file $IAAS_ACCESS_KEY_FILE 34 $IAAS_HOME/bin/akm-delete-access-key $AK 35 fi 36 PROCESSING_ACCOUNT=$ACCOUNT 37 IAAS_USER=$ACCOUNT_USER 38 echo "$ACCOUNT_PASSWORD" > $IAAS_PASSWORD_FILE 39 $IAAS_HOME/bin/akm-describe-accounts --sep "|" > $ACCOUNTS_FILE 40 while read line 41 do 42 ACCOUNT_ID=${line%%|*} 43 line=${line#*|} 44 ACCOUNT_NAME=${line%%|*} 45 # echo "Id = $ACCOUNT_ID" 46 # echo "Name = $ACCOUNT_NAME" 47 if [[ "$ACCOUNT_NAME" == "$ACCOUNT" ]] 48 then 49 echo "Found Production Account $line" 50 AK=`$IAAS_HOME/bin/akm-create-access-key --account $ACCOUNT_ID --access-key-file $IAAS_ACCESS_KEY_FILE` 51 KEYPAIR=`$IAAS_HOME/bin/iaas-create-key-pair --key-name $KEY_NAME --key-file $KEY_FILE` 52 echo "Connected to $ACCOUNT_NAME" 53 break 54 fi 55 done < $ACCOUNTS_FILE 56 fi 57 } 58 59 function disconnectFromAccount() { 60 $IAAS_HOME/bin/iaas-delete-key-pair --key-name $KEY_NAME --access-key-file $IAAS_ACCESS_KEY_FILE 61 $IAAS_HOME/bin/akm-delete-access-key $AK 62 PROCESSING_ACCOUNT="" 63 } 64 65 function getNetworks() { 66 $IAAS_HOME/bin/iaas-describe-vnets --sep "|" > $VNETS_FILE 67 } 68 69 function getVSTypes() { 70 $IAAS_HOME/bin/iaas-describe-vserver-types --sep "|" > $VSERVER_TYPES_FILE 71 } 72 73 function getTemplates() { 74 $IAAS_HOME/bin/iaas-describe-server-templates --sep "|" > $VSERVER_TEMPLATES 75 } 76 77 function getVolumes() { 78 $IAAS_HOME/bin/iaas-describe-volumes --sep "|" > $VOLUMES_FILE 79 } 80 81 function getVServers() { 82 $IAAS_HOME/bin/iaas-describe-vservers --sep "|" > $VSERVER_FILE 83 } 84 85 function getNetworkId() { 86 while read line 87 do 88 NETWORK_ID=${line%%|*} 89 line=${line#*|} 90 NAME=${line%%|*} 91 if [[ "$NAME" == "$NETWORK_NAME" ]] 92 then 93 break 94 fi 95 done < $VNETS_FILE 96 } 97 98 function getVSTypeId() { 99 while read line 100 do 101 VSTYPE_ID=${line%%|*} 102 line=${line#*|} 103 NAME=${line%%|*} 104 if [[ "$VSTYPE_NAME" == "$NAME" ]] 105 then 106 break 107 fi 108 done < $VSERVER_TYPES_FILE 109 } 110 111 function getTemplateId() { 112 while read line 113 do 114 TEMPLATE_ID=${line%%|*} 115 line=${line#*|} 116 NAME=${line%%|*} 117 if [[ "$TEMPLATE_NAME" == "$NAME" ]] 118 then 119 break 120 fi 121 done < $VSERVER_TEMPLATES 122 } 123 124 function getVolumeId() { 125 while read line 126 do 127 export VOLUME_ID=${line%%|*} 128 line=${line#*|} 129 NAME=${line%%|*} 130 if [[ "$NAME" == "$VOLUME_NAME" ]] 131 then 132 break; 133 fi 134 done < $VOLUMES_FILE 135 } 136 137 function getVServerId() { 138 while read line 139 do 140 VSERVER_ID=${line%%|*} 141 line=${line#*|} 142 NAME=${line%%|*} 143 if [[ "$VSERVER_NAME" == "$NAME" ]] 144 then 145 break; 146 fi 147 done < $VSERVER_FILE 148 } 149 150 function getVServerState() { 151 getVServers 152 while read line 153 do 154 VSERVER_ID=${line%%|*} 155 line=${line#*|} 156 NAME=${line%%|*} 157 line=${line#*|} 158 line=${line#*|} 159 VSERVER_STATE=${line%%|*} 160 if [[ "$VSERVER_NAME" == "$NAME" ]] 161 then 162 break; 163 fi 164 done < $VSERVER_FILE 165 } 166 167 function pauseUntilVServerRunning() { 168 # Wait until the Server is running before creating the next 169 getVServerState 170 while [[ "$VSERVER_STATE" != "RUNNING" ]] 171 do 172 getVServerState 173 echo "$NAME $VSERVER_STATE" 174 if [[ "$VSERVER_STATE" != "RUNNING" ]] 175 then 176 echo "Sleeping......." 177 sleep 60 178 fi 179 if [[ "$VSERVER_STATE" == "FAILED" ]] 180 then 181 echo "Will Delete $NAME in 5 Minutes....." 182 sleep 300 183 deleteVServer 184 echo "Deleted $NAME waiting 5 Minutes....." 185 sleep 300 186 break 187 fi 188 done 189 # Lets pause for a minute or two 190 echo "Just Chilling......" 191 sleep 60 192 echo "Ahhhhh we're getting there......." 193 sleep 60 194 echo "I'm almost at one with the universe......." 195 sleep 60 196 echo "Bong Reality Check !" 197 } 198 199 function deleteVServer() { 200 $IAAS_HOME/bin/iaas-terminate-vservers --force --vserver-ids $VSERVER_ID 201 } 202 203 function createVServer() { 204 VSERVER_NAME=${ASSET_DETAILS%%|*} 205 ASSET_DETAILS=${ASSET_DETAILS#*|} 206 VSTYPE_NAME=${ASSET_DETAILS%%|*} 207 ASSET_DETAILS=${ASSET_DETAILS#*|} 208 TEMPLATE_NAME=${ASSET_DETAILS%%|*} 209 ASSET_DETAILS=${ASSET_DETAILS#*|} 210 NETWORK_NAMES=${ASSET_DETAILS%%|*} 211 ASSET_DETAILS=${ASSET_DETAILS#*|} 212 IP_ADDRESSES=${ASSET_DETAILS%%|*} 213 # Get Ids associated with names 214 getVSTypeId 215 getTemplateId 216 # Convert Network Names to Ids 217 NETWORK_IDS="" 218 while true 219 do 220 NETWORK_NAME=${NETWORK_NAMES%%,*} 221 NETWORK_NAMES=${NETWORK_NAMES#*,} 222 getNetworkId 223 if [[ "$NETWORK_IDS" != "" ]] 224 then 225 NETWORK_IDS="$NETWORK_IDS,$NETWORK_ID" 226 else 227 NETWORK_IDS=$NETWORK_ID 228 fi 229 if [[ "$NETWORK_NAME" == "$NETWORK_NAMES" ]] 230 then 231 break 232 fi 233 done 234 # Create vServer 235 echo "About to execute : $IAAS_HOME/bin/iaas-run-vserver --name $VSERVER_NAME --key-name $KEY_NAME --vserver-type $VSTYPE_ID --server-template-id $TEMPLATE_ID --vnets $NETWORK_IDS --ip-addresses $IP_ADDRESSES" 236 $IAAS_HOME/bin/iaas-run-vserver --name $VSERVER_NAME --key-name $KEY_NAME --vserver-type $VSTYPE_ID --server-template-id $TEMPLATE_ID --vnets $NETWORK_IDS --ip-addresses $IP_ADDRESSES 237 pauseUntilVServerRunning 238 } 239 240 function createVolume() { 241 VOLUME_NAME=${ASSET_DETAILS%%|*} 242 ASSET_DETAILS=${ASSET_DETAILS#*|} 243 VOLUME_SIZE=${ASSET_DETAILS%%|*} 244 # Create Volume 245 echo "About to execute : $IAAS_HOME/bin/iaas-create-volume --name $VOLUME_NAME --size $VOLUME_SIZE" 246 $IAAS_HOME/bin/iaas-create-volume --name $VOLUME_NAME --size $VOLUME_SIZE 247 # Lets pause 248 echo "Just Waiting 30 Seconds......" 249 sleep 30 250 } 251 252 function attachVolume() { 253 VSERVER_NAME=${ASSET_DETAILS%%|*} 254 ASSET_DETAILS=${ASSET_DETAILS#*|} 255 VOLUME_NAMES=${ASSET_DETAILS%%|*} 256 # Get vServer Id 257 getVServerId 258 # Convert Volume Names to Ids 259 VOLUME_IDS="" 260 while true 261 do 262 VOLUME_NAME=${VOLUME_NAMES%%,*} 263 VOLUME_NAMES=${VOLUME_NAMES#*,} 264 getVolumeId 265 if [[ "$VOLUME_IDS" != "" ]] 266 then 267 VOLUME_IDS="$VOLUME_IDS,$VOLUME_ID" 268 else 269 VOLUME_IDS=$VOLUME_ID 270 fi 271 if [[ "$VOLUME_NAME" == "$VOLUME_NAMES" ]] 272 then 273 break 274 fi 275 done 276 # Attach Volumes 277 echo "About to execute : $IAAS_HOME/bin/iaas-attach-volumes-to-vserver --vserver-id $VSERVER_ID --volume-ids $VOLUME_IDS" 278 $IAAS_HOME/bin/iaas-attach-volumes-to-vserver --vserver-id $VSERVER_ID --volume-ids $VOLUME_IDS 279 # Lets pause 280 echo "Just Waiting 30 Seconds......" 281 sleep 30 282 } 283 284 function processAssets() { 285 while read line 286 do 287 ACCOUNT=${line%%:*} 288 line=${line#*:} 289 ACTION=${line%%|*} 290 line=${line#*|} 291 if [[ "$ACTION" == "Connect" ]] 292 then 293 ACCOUNT_USER=${line%%|*} 294 line=${line#*|} 295 ACCOUNT_PASSWORD=${line%%|*} 296 connectToAccount 297 298 ## Account Info 299 getNetworks 300 getVSTypes 301 getTemplates 302 303 continue 304 fi 305 if [[ "$ACTION" == "Create" ]] 306 then 307 ASSET=${line%%|*} 308 line=${line#*|} 309 ASSET_DETAILS=$line 310 if [[ "$ASSET" == "vServer" ]] 311 then 312 createVServer 313 314 continue 315 fi 316 if [[ "$ASSET" == "Volume" ]] 317 then 318 createVolume 319 320 continue 321 fi 322 fi 323 if [[ "$ACTION" == "Attach" ]] 324 then 325 ASSET=${line%%|*} 326 line=${line#*|} 327 ASSET_DETAILS=$line 328 if [[ "$ASSET" == "Volume" ]] 329 then 330 getVolumes 331 getVServers 332 attachVolume 333 334 continue 335 fi 336 fi 337 if [[ "$ACTION" == "Connect" ]] 338 then 339 disconnectFromAccount 340 341 continue 342 fi 343 done < $INPUT_FILE 344 } 345 346 # Should Parameterise this 347 348 while [ $# -gt 0 ] 349 do 350 case "$1" in 351 -a) INPUT_FILE="$2"; shift;; 352 *) echo ""; echo >&2 \ 353 "usage: $0 [-a <Asset Definition File>] (Default is CreateAssets.in)" 354 echo""; exit 1;; 355 *) break;; 356 esac 357 shift 358 done 359 360 361 362 363 processAssets 364 365 echo "**************************************" 366 echo "***** Finished Creating Assets *****" 367 echo "**************************************" 368 CreateAssetsProd.in Production:Connect|exaprod|welcome1 Production:Create|vServer|VS006|VSTProduction|BaseOEL56ServerTemplate|EoIB-otd-prod,vn-prod-web,IPoIB-default,IPoIB-vserver-shared-storage|10.51.223.13,192.168.0.13,10.117.81.67,172.17.0.14 Production:Create|vServer|VS007|VSTProduction|BaseOEL56ServerTemplate|EoIB-otd-prod,vn-prod-web,IPoIB-default,IPoIB-vserver-shared-storage|10.51.223.14,192.168.0.14,10.117.81.68,172.17.0.15 Production:Create|vServer|VS008|VSTProduction|BaseOEL56ServerTemplate|EoIB-wls-prod,vn-prod-web,IPoIB-default,IPoIB-vserver-shared-storage|10.51.225.61,192.168.0.61,10.117.81.61,172.17.0.16 Production:Create|vServer|VS009|VSTProduction|BaseOEL56ServerTemplate|EoIB-wls-prod,vn-prod-web,IPoIB-default,IPoIB-vserver-shared-storage|10.51.225.62,192.168.0.62,10.117.81.62,172.17.0.17 Production:Create|vServer|VS000|VSTProduction|BaseOEL56ServerTemplate|EoIB-wls-prod,vn-prod-web,IPoIB-default,IPoIB-vserver-shared-storage|10.51.225.63,192.168.0.63,10.117.81.63,172.17.0.18 Production:Create|vServer|VS001|VSTProduction|BaseOEL56ServerTemplate|EoIB-wls-prod,vn-prod-web,IPoIB-default,IPoIB-vserver-shared-storage|10.51.225.64,192.168.0.64,10.117.81.64,172.17.0.19 Production:Create|vServer|VS002|VSTProduction|BaseOEL56ServerTemplate|EoIB-wls-prod,vn-prod-web,IPoIB-default,IPoIB-vserver-shared-storage|10.51.225.65,192.168.0.65,10.117.81.65,172.17.0.20 Production:Create|vServer|VS003|VSTProduction|BaseOEL56ServerTemplate|EoIB-wls-prod,vn-prod-web,IPoIB-default,IPoIB-vserver-shared-storage|10.51.225.66,192.168.0.66,10.117.81.66,172.17.0.21 Production:Create|Volume|VS006|50 Production:Create|Volume|VS007|50 Production:Create|Volume|VS008|50 Production:Create|Volume|VS009|50 Production:Create|Volume|VS000|50 Production:Create|Volume|VS001|50 Production:Create|Volume|VS002|50 Production:Create|Volume|VS003|50 Production:Attach|Volume|VS006|VS006 Production:Attach|Volume|VS007|VS007 Production:Attach|Volume|VS008|VS008 Production:Attach|Volume|VS009|VS009 Production:Attach|Volume|VS000|VS000 Production:Attach|Volume|VS001|VS001 Production:Attach|Volume|VS002|VS002 Production:Attach|Volume|VS003|VS003 Production:Disconnect Development:Connect|exadev|welcome1 Development:Create|vServer|VS014|VSTDevelopment|BaseOEL56ServerTemplate|EoIB-development,IPoIB-default,IPoIB-vserver-shared-storage|10.51.224.24,10.117.81.71,172.17.0.24 Development:Create|vServer|VS015|VSTDevelopment|BaseOEL56ServerTemplate|EoIB-development,IPoIB-default,IPoIB-vserver-shared-storage|10.51.224.25,10.117.81.72,172.17.0.25 Development:Create|vServer|VS016|VSTDevelopment|BaseOEL56ServerTemplate|EoIB-development,IPoIB-default,IPoIB-vserver-shared-storage|10.51.224.26,10.117.81.73,172.17.0.26 Development:Create|vServer|VS017|VSTDevelopment|BaseOEL56ServerTemplate|EoIB-development,IPoIB-default,IPoIB-vserver-shared-storage|10.51.224.27,10.117.81.74,172.17.0.27 Development:Create|vServer|VS018|VSTDevelopment|BaseOEL56ServerTemplate|EoIB-development,IPoIB-default,IPoIB-vserver-shared-storage|10.51.224.28,10.117.81.75,172.17.0.28 Development:Create|vServer|VS019|VSTDevelopment|BaseOEL56ServerTemplate|EoIB-development,IPoIB-default,IPoIB-vserver-shared-storage|10.51.224.29,10.117.81.76,172.17.0.29 Development:Create|vServer|VS020|VSTDevelopment|BaseOEL56ServerTemplate|EoIB-development,IPoIB-default,IPoIB-vserver-shared-storage|10.51.224.30,10.117.81.77,172.17.0.30 Development:Create|vServer|VS021|VSTDevelopment|BaseOEL56ServerTemplate|EoIB-development,IPoIB-default,IPoIB-vserver-shared-storage|10.51.224.31,10.117.81.78,172.17.0.31 Development:Create|vServer|VS022|VSTDevelopment|BaseOEL56ServerTemplate|EoIB-development,IPoIB-default,IPoIB-vserver-shared-storage|10.51.224.32,10.117.81.79,172.17.0.32 Development:Create|vServer|VS023|VSTDevelopment|BaseOEL56ServerTemplate|EoIB-development,IPoIB-default,IPoIB-vserver-shared-storage|10.51.224.33,10.117.81.80,172.17.0.33 Development:Create|vServer|VS024|VSTDevelopment|BaseOEL56ServerTemplate|EoIB-development,IPoIB-default,IPoIB-vserver-shared-storage|10.51.224.34,10.117.81.81,172.17.0.34 Development:Create|vServer|VS025|VSTDevelopment|BaseOEL56ServerTemplate|EoIB-development,IPoIB-default,IPoIB-vserver-shared-storage|10.51.224.35,10.117.81.82,172.17.0.35 Development:Create|vServer|VS026|VSTDevelopment|BaseOEL56ServerTemplate|EoIB-development,IPoIB-default,IPoIB-vserver-shared-storage|10.51.224.36,10.117.81.83,172.17.0.36 Development:Create|vServer|VS027|VSTDevelopment|BaseOEL56ServerTemplate|EoIB-development,IPoIB-default,IPoIB-vserver-shared-storage|10.51.224.37,10.117.81.84,172.17.0.37 Development:Create|Volume|VS014|50 Development:Create|Volume|VS015|50 Development:Create|Volume|VS016|50 Development:Create|Volume|VS017|50 Development:Create|Volume|VS018|50 Development:Create|Volume|VS019|50 Development:Create|Volume|VS020|50 Development:Create|Volume|VS021|50 Development:Create|Volume|VS022|50 Development:Create|Volume|VS023|50 Development:Create|Volume|VS024|50 Development:Create|Volume|VS025|50 Development:Create|Volume|VS026|50 Development:Create|Volume|VS027|50 Development:Attach|Volume|VS014|VS014 Development:Attach|Volume|VS015|VS015 Development:Attach|Volume|VS016|VS016 Development:Attach|Volume|VS017|VS017 Development:Attach|Volume|VS018|VS018 Development:Attach|Volume|VS019|VS019 Development:Attach|Volume|VS020|VS020 Development:Attach|Volume|VS021|VS021 Development:Attach|Volume|VS022|VS022 Development:Attach|Volume|VS023|VS023 Development:Attach|Volume|VS024|VS024 Development:Attach|Volume|VS025|VS025 Development:Attach|Volume|VS026|VS026 Development:Attach|Volume|VS027|VS027 Development:Disconnect This entry was originally posted on the The Old Toxophilist Site.

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  • Understanding C# async / await (1) Compilation

    - by Dixin
    Now the async / await keywords are in C#. Just like the async and ! in F#, this new C# feature provides great convenience. There are many nice documents talking about how to use async / await in specific scenarios, like using async methods in ASP.NET 4.5 and in ASP.NET MVC 4, etc. In this article we will look at the real code working behind the syntax sugar. According to MSDN: The async modifier indicates that the method, lambda expression, or anonymous method that it modifies is asynchronous. Since lambda expression / anonymous method will be compiled to normal method, we will focus on normal async method. Preparation First of all, Some helper methods need to make up. internal class HelperMethods { internal static int Method(int arg0, int arg1) { // Do some IO. WebClient client = new WebClient(); Enumerable.Repeat("http://weblogs.asp.net/dixin", 10) .Select(client.DownloadString).ToArray(); int result = arg0 + arg1; return result; } internal static Task<int> MethodTask(int arg0, int arg1) { Task<int> task = new Task<int>(() => Method(arg0, arg1)); task.Start(); // Hot task (started task) should always be returned. return task; } internal static void Before() { } internal static void Continuation1(int arg) { } internal static void Continuation2(int arg) { } } Here Method() is a long running method doing some IO. Then MethodTask() wraps it into a Task and return that Task. Nothing special here. Await something in async method Since MethodTask() returns Task, let’s try to await it: internal class AsyncMethods { internal static async Task<int> MethodAsync(int arg0, int arg1) { int result = await HelperMethods.MethodTask(arg0, arg1); return result; } } Because we used await in the method, async must be put on the method. Now we get the first async method. According to the naming convenience, it is called MethodAsync. Of course a async method can be awaited. So we have a CallMethodAsync() to call MethodAsync(): internal class AsyncMethods { internal static async Task<int> CallMethodAsync(int arg0, int arg1) { int result = await MethodAsync(arg0, arg1); return result; } } After compilation, MethodAsync() and CallMethodAsync() becomes the same logic. This is the code of MethodAsyc(): internal class CompiledAsyncMethods { [DebuggerStepThrough] [AsyncStateMachine(typeof(MethodAsyncStateMachine))] // async internal static /*async*/ Task<int> MethodAsync(int arg0, int arg1) { MethodAsyncStateMachine methodAsyncStateMachine = new MethodAsyncStateMachine() { Arg0 = arg0, Arg1 = arg1, Builder = AsyncTaskMethodBuilder<int>.Create(), State = -1 }; methodAsyncStateMachine.Builder.Start(ref methodAsyncStateMachine); return methodAsyncStateMachine.Builder.Task; } } It just creates and starts a state machine MethodAsyncStateMachine: [CompilerGenerated] [StructLayout(LayoutKind.Auto)] internal struct MethodAsyncStateMachine : IAsyncStateMachine { public int State; public AsyncTaskMethodBuilder<int> Builder; public int Arg0; public int Arg1; public int Result; private TaskAwaiter<int> awaitor; void IAsyncStateMachine.MoveNext() { try { if (this.State != 0) { this.awaitor = HelperMethods.MethodTask(this.Arg0, this.Arg1).GetAwaiter(); if (!this.awaitor.IsCompleted) { this.State = 0; this.Builder.AwaitUnsafeOnCompleted(ref this.awaitor, ref this); return; } } else { this.State = -1; } this.Result = this.awaitor.GetResult(); } catch (Exception exception) { this.State = -2; this.Builder.SetException(exception); return; } this.State = -2; this.Builder.SetResult(this.Result); } [DebuggerHidden] void IAsyncStateMachine.SetStateMachine(IAsyncStateMachine param0) { this.Builder.SetStateMachine(param0); } } The generated code has been cleaned up so it is readable and can be compiled. Several things can be observed here: The async modifier is gone, which shows, unlike other modifiers (e.g. static), there is no such IL/CLR level “async” stuff. It becomes a AsyncStateMachineAttribute. This is similar to the compilation of extension method. The generated state machine is very similar to the state machine of C# yield syntax sugar. The local variables (arg0, arg1, result) are compiled to fields of the state machine. The real code (await HelperMethods.MethodTask(arg0, arg1)) is compiled into MoveNext(): HelperMethods.MethodTask(this.Arg0, this.Arg1).GetAwaiter(). CallMethodAsync() will create and start its own state machine CallMethodAsyncStateMachine: internal class CompiledAsyncMethods { [DebuggerStepThrough] [AsyncStateMachine(typeof(CallMethodAsyncStateMachine))] // async internal static /*async*/ Task<int> CallMethodAsync(int arg0, int arg1) { CallMethodAsyncStateMachine callMethodAsyncStateMachine = new CallMethodAsyncStateMachine() { Arg0 = arg0, Arg1 = arg1, Builder = AsyncTaskMethodBuilder<int>.Create(), State = -1 }; callMethodAsyncStateMachine.Builder.Start(ref callMethodAsyncStateMachine); return callMethodAsyncStateMachine.Builder.Task; } } CallMethodAsyncStateMachine has the same logic as MethodAsyncStateMachine above. The detail of the state machine will be discussed soon. Now it is clear that: async /await is a C# level syntax sugar. There is no difference to await a async method or a normal method. A method returning Task will be awaitable. State machine and continuation To demonstrate more details in the state machine, a more complex method is created: internal class AsyncMethods { internal static async Task<int> MultiCallMethodAsync(int arg0, int arg1, int arg2, int arg3) { HelperMethods.Before(); int resultOfAwait1 = await MethodAsync(arg0, arg1); HelperMethods.Continuation1(resultOfAwait1); int resultOfAwait2 = await MethodAsync(arg2, arg3); HelperMethods.Continuation2(resultOfAwait2); int resultToReturn = resultOfAwait1 + resultOfAwait2; return resultToReturn; } } In this method: There are multiple awaits. There are code before the awaits, and continuation code after each await After compilation, this multi-await method becomes the same as above single-await methods: internal class CompiledAsyncMethods { [DebuggerStepThrough] [AsyncStateMachine(typeof(MultiCallMethodAsyncStateMachine))] // async internal static /*async*/ Task<int> MultiCallMethodAsync(int arg0, int arg1, int arg2, int arg3) { MultiCallMethodAsyncStateMachine multiCallMethodAsyncStateMachine = new MultiCallMethodAsyncStateMachine() { Arg0 = arg0, Arg1 = arg1, Arg2 = arg2, Arg3 = arg3, Builder = AsyncTaskMethodBuilder<int>.Create(), State = -1 }; multiCallMethodAsyncStateMachine.Builder.Start(ref multiCallMethodAsyncStateMachine); return multiCallMethodAsyncStateMachine.Builder.Task; } } It creates and starts one single state machine, MultiCallMethodAsyncStateMachine: [CompilerGenerated] [StructLayout(LayoutKind.Auto)] internal struct MultiCallMethodAsyncStateMachine : IAsyncStateMachine { public int State; public AsyncTaskMethodBuilder<int> Builder; public int Arg0; public int Arg1; public int Arg2; public int Arg3; public int ResultOfAwait1; public int ResultOfAwait2; public int ResultToReturn; private TaskAwaiter<int> awaiter; void IAsyncStateMachine.MoveNext() { try { switch (this.State) { case -1: HelperMethods.Before(); this.awaiter = AsyncMethods.MethodAsync(this.Arg0, this.Arg1).GetAwaiter(); if (!this.awaiter.IsCompleted) { this.State = 0; this.Builder.AwaitUnsafeOnCompleted(ref this.awaiter, ref this); } break; case 0: this.ResultOfAwait1 = this.awaiter.GetResult(); HelperMethods.Continuation1(this.ResultOfAwait1); this.awaiter = AsyncMethods.MethodAsync(this.Arg2, this.Arg3).GetAwaiter(); if (!this.awaiter.IsCompleted) { this.State = 1; this.Builder.AwaitUnsafeOnCompleted(ref this.awaiter, ref this); } break; case 1: this.ResultOfAwait2 = this.awaiter.GetResult(); HelperMethods.Continuation2(this.ResultOfAwait2); this.ResultToReturn = this.ResultOfAwait1 + this.ResultOfAwait2; this.State = -2; this.Builder.SetResult(this.ResultToReturn); break; } } catch (Exception exception) { this.State = -2; this.Builder.SetException(exception); } } [DebuggerHidden] void IAsyncStateMachine.SetStateMachine(IAsyncStateMachine stateMachine) { this.Builder.SetStateMachine(stateMachine); } } The above code is already cleaned up, but there are still a lot of things. More clean up can be done, and the state machine can be very simple: [CompilerGenerated] [StructLayout(LayoutKind.Auto)] internal struct MultiCallMethodAsyncStateMachine : IAsyncStateMachine { // State: // -1: Begin // 0: 1st await is done // 1: 2nd await is done // ... // -2: End public int State; public TaskCompletionSource<int> ResultToReturn; // int resultToReturn ... public int Arg0; // int Arg0 public int Arg1; // int arg1 public int Arg2; // int arg2 public int Arg3; // int arg3 public int ResultOfAwait1; // int resultOfAwait1 ... public int ResultOfAwait2; // int resultOfAwait2 ... private Task<int> currentTaskToAwait; /// <summary> /// Moves the state machine to its next state. /// </summary> void IAsyncStateMachine.MoveNext() { try { switch (this.State) { // Orginal code is splitted by "case"s: // case -1: // HelperMethods.Before(); // MethodAsync(Arg0, arg1); // case 0: // int resultOfAwait1 = await ... // HelperMethods.Continuation1(resultOfAwait1); // MethodAsync(arg2, arg3); // case 1: // int resultOfAwait2 = await ... // HelperMethods.Continuation2(resultOfAwait2); // int resultToReturn = resultOfAwait1 + resultOfAwait2; // return resultToReturn; case -1: // -1 is begin. HelperMethods.Before(); // Code before 1st await. this.currentTaskToAwait = AsyncMethods.MethodAsync(this.Arg0, this.Arg1); // 1st task to await // When this.currentTaskToAwait is done, run this.MoveNext() and go to case 0. this.State = 0; IAsyncStateMachine this1 = this; // Cannot use "this" in lambda so create a local variable. this.currentTaskToAwait.ContinueWith(_ => this1.MoveNext()); // Callback break; case 0: // Now 1st await is done. this.ResultOfAwait1 = this.currentTaskToAwait.Result; // Get 1st await's result. HelperMethods.Continuation1(this.ResultOfAwait1); // Code after 1st await and before 2nd await. this.currentTaskToAwait = AsyncMethods.MethodAsync(this.Arg2, this.Arg3); // 2nd task to await // When this.currentTaskToAwait is done, run this.MoveNext() and go to case 1. this.State = 1; IAsyncStateMachine this2 = this; // Cannot use "this" in lambda so create a local variable. this.currentTaskToAwait.ContinueWith(_ => this2.MoveNext()); // Callback break; case 1: // Now 2nd await is done. this.ResultOfAwait2 = this.currentTaskToAwait.Result; // Get 2nd await's result. HelperMethods.Continuation2(this.ResultOfAwait2); // Code after 2nd await. int resultToReturn = this.ResultOfAwait1 + this.ResultOfAwait2; // Code after 2nd await. // End with resultToReturn. this.State = -2; // -2 is end. this.ResultToReturn.SetResult(resultToReturn); break; } } catch (Exception exception) { // End with exception. this.State = -2; // -2 is end. this.ResultToReturn.SetException(exception); } } /// <summary> /// Configures the state machine with a heap-allocated replica. /// </summary> /// <param name="stateMachine">The heap-allocated replica.</param> [DebuggerHidden] void IAsyncStateMachine.SetStateMachine(IAsyncStateMachine stateMachine) { // No core logic. } } Only Task and TaskCompletionSource are involved in this version. And MultiCallMethodAsync() can be simplified to: [DebuggerStepThrough] [AsyncStateMachine(typeof(MultiCallMethodAsyncStateMachine))] // async internal static /*async*/ Task<int> MultiCallMethodAsync_(int arg0, int arg1, int arg2, int arg3) { MultiCallMethodAsyncStateMachine multiCallMethodAsyncStateMachine = new MultiCallMethodAsyncStateMachine() { Arg0 = arg0, Arg1 = arg1, Arg2 = arg2, Arg3 = arg3, ResultToReturn = new TaskCompletionSource<int>(), // -1: Begin // 0: 1st await is done // 1: 2nd await is done // ... // -2: End State = -1 }; (multiCallMethodAsyncStateMachine as IAsyncStateMachine).MoveNext(); // Original code are in this method. return multiCallMethodAsyncStateMachine.ResultToReturn.Task; } Now the whole state machine becomes very clear - it is about callback: Original code are split into pieces by “await”s, and each piece is put into each “case” in the state machine. Here the 2 awaits split the code into 3 pieces, so there are 3 “case”s. The “piece”s are chained by callback, that is done by Builder.AwaitUnsafeOnCompleted(callback), or currentTaskToAwait.ContinueWith(callback) in the simplified code. A previous “piece” will end with a Task (which is to be awaited), when the task is done, it will callback the next “piece”. The state machine’s state works with the “case”s to ensure the code “piece”s executes one after another. Callback Since it is about callback, the simplification  can go even further – the entire state machine can be completely purged. Now MultiCallMethodAsync() becomes: internal static Task<int> MultiCallMethodAsync(int arg0, int arg1, int arg2, int arg3) { TaskCompletionSource<int> taskCompletionSource = new TaskCompletionSource<int>(); try { // Oringinal code begins. HelperMethods.Before(); MethodAsync(arg0, arg1).ContinueWith(await1 => { int resultOfAwait1 = await1.Result; HelperMethods.Continuation1(resultOfAwait1); MethodAsync(arg2, arg3).ContinueWith(await2 => { int resultOfAwait2 = await2.Result; HelperMethods.Continuation2(resultOfAwait2); int resultToReturn = resultOfAwait1 + resultOfAwait2; // Oringinal code ends. taskCompletionSource.SetResult(resultToReturn); }); }); } catch (Exception exception) { taskCompletionSource.SetException(exception); } return taskCompletionSource.Task; } Please compare with the original async / await code: HelperMethods.Before(); int resultOfAwait1 = await MethodAsync(arg0, arg1); HelperMethods.Continuation1(resultOfAwait1); int resultOfAwait2 = await MethodAsync(arg2, arg3); HelperMethods.Continuation2(resultOfAwait2); int resultToReturn = resultOfAwait1 + resultOfAwait2; return resultToReturn; Yeah that is the magic of C# async / await: Await is literally pretending to wait. In a await expression, a Task object will be return immediately so that caller is not blocked. The continuation code is compiled as that Task’s callback code. When that task is done, continuation code will execute. Please notice that many details inside the state machine are omitted for simplicity, like context caring, etc. If you want to have a detailed picture, please do check out the source code of AsyncTaskMethodBuilder and TaskAwaiter.

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  • Understanding C# async / await (1) Compilation

    - by Dixin
    Now the async / await keywords are in C#. Just like the async and ! in F#, this new C# feature provides great convenience. There are many nice documents talking about how to use async / await in specific scenarios, like using async methods in ASP.NET 4.5 and in ASP.NET MVC 4, etc. In this article we will look at the real code working behind the syntax sugar. According to MSDN: The async modifier indicates that the method, lambda expression, or anonymous method that it modifies is asynchronous. Since lambda expression / anonymous method will be compiled to normal method, we will focus on normal async method. Preparation First of all, Some helper methods need to make up. internal class HelperMethods { internal static int Method(int arg0, int arg1) { // Do some IO. WebClient client = new WebClient(); Enumerable.Repeat("http://weblogs.asp.net/dixin", 10) .Select(client.DownloadString).ToArray(); int result = arg0 + arg1; return result; } internal static Task<int> MethodTask(int arg0, int arg1) { Task<int> task = new Task<int>(() => Method(arg0, arg1)); task.Start(); // Hot task (started task) should always be returned. return task; } internal static void Before() { } internal static void Continuation1(int arg) { } internal static void Continuation2(int arg) { } } Here Method() is a long running method doing some IO. Then MethodTask() wraps it into a Task and return that Task. Nothing special here. Await something in async method Since MethodTask() returns Task, let’s try to await it: internal class AsyncMethods { internal static async Task<int> MethodAsync(int arg0, int arg1) { int result = await HelperMethods.MethodTask(arg0, arg1); return result; } } Because we used await in the method, async must be put on the method. Now we get the first async method. According to the naming convenience, it is named MethodAsync. Of course a async method can be awaited. So we have a CallMethodAsync() to call MethodAsync(): internal class AsyncMethods { internal static async Task<int> CallMethodAsync(int arg0, int arg1) { int result = await MethodAsync(arg0, arg1); return result; } } After compilation, MethodAsync() and CallMethodAsync() becomes the same logic. This is the code of MethodAsyc(): internal class CompiledAsyncMethods { [DebuggerStepThrough] [AsyncStateMachine(typeof(MethodAsyncStateMachine))] // async internal static /*async*/ Task<int> MethodAsync(int arg0, int arg1) { MethodAsyncStateMachine methodAsyncStateMachine = new MethodAsyncStateMachine() { Arg0 = arg0, Arg1 = arg1, Builder = AsyncTaskMethodBuilder<int>.Create(), State = -1 }; methodAsyncStateMachine.Builder.Start(ref methodAsyncStateMachine); return methodAsyncStateMachine.Builder.Task; } } It just creates and starts a state machine, MethodAsyncStateMachine: [CompilerGenerated] [StructLayout(LayoutKind.Auto)] internal struct MethodAsyncStateMachine : IAsyncStateMachine { public int State; public AsyncTaskMethodBuilder<int> Builder; public int Arg0; public int Arg1; public int Result; private TaskAwaiter<int> awaitor; void IAsyncStateMachine.MoveNext() { try { if (this.State != 0) { this.awaitor = HelperMethods.MethodTask(this.Arg0, this.Arg1).GetAwaiter(); if (!this.awaitor.IsCompleted) { this.State = 0; this.Builder.AwaitUnsafeOnCompleted(ref this.awaitor, ref this); return; } } else { this.State = -1; } this.Result = this.awaitor.GetResult(); } catch (Exception exception) { this.State = -2; this.Builder.SetException(exception); return; } this.State = -2; this.Builder.SetResult(this.Result); } [DebuggerHidden] void IAsyncStateMachine.SetStateMachine(IAsyncStateMachine param0) { this.Builder.SetStateMachine(param0); } } The generated code has been refactored, so it is readable and can be compiled. Several things can be observed here: The async modifier is gone, which shows, unlike other modifiers (e.g. static), there is no such IL/CLR level “async” stuff. It becomes a AsyncStateMachineAttribute. This is similar to the compilation of extension method. The generated state machine is very similar to the state machine of C# yield syntax sugar. The local variables (arg0, arg1, result) are compiled to fields of the state machine. The real code (await HelperMethods.MethodTask(arg0, arg1)) is compiled into MoveNext(): HelperMethods.MethodTask(this.Arg0, this.Arg1).GetAwaiter(). CallMethodAsync() will create and start its own state machine CallMethodAsyncStateMachine: internal class CompiledAsyncMethods { [DebuggerStepThrough] [AsyncStateMachine(typeof(CallMethodAsyncStateMachine))] // async internal static /*async*/ Task<int> CallMethodAsync(int arg0, int arg1) { CallMethodAsyncStateMachine callMethodAsyncStateMachine = new CallMethodAsyncStateMachine() { Arg0 = arg0, Arg1 = arg1, Builder = AsyncTaskMethodBuilder<int>.Create(), State = -1 }; callMethodAsyncStateMachine.Builder.Start(ref callMethodAsyncStateMachine); return callMethodAsyncStateMachine.Builder.Task; } } CallMethodAsyncStateMachine has the same logic as MethodAsyncStateMachine above. The detail of the state machine will be discussed soon. Now it is clear that: async /await is a C# language level syntax sugar. There is no difference to await a async method or a normal method. As long as a method returns Task, it is awaitable. State machine and continuation To demonstrate more details in the state machine, a more complex method is created: internal class AsyncMethods { internal static async Task<int> MultiCallMethodAsync(int arg0, int arg1, int arg2, int arg3) { HelperMethods.Before(); int resultOfAwait1 = await MethodAsync(arg0, arg1); HelperMethods.Continuation1(resultOfAwait1); int resultOfAwait2 = await MethodAsync(arg2, arg3); HelperMethods.Continuation2(resultOfAwait2); int resultToReturn = resultOfAwait1 + resultOfAwait2; return resultToReturn; } } In this method: There are multiple awaits. There are code before the awaits, and continuation code after each await After compilation, this multi-await method becomes the same as above single-await methods: internal class CompiledAsyncMethods { [DebuggerStepThrough] [AsyncStateMachine(typeof(MultiCallMethodAsyncStateMachine))] // async internal static /*async*/ Task<int> MultiCallMethodAsync(int arg0, int arg1, int arg2, int arg3) { MultiCallMethodAsyncStateMachine multiCallMethodAsyncStateMachine = new MultiCallMethodAsyncStateMachine() { Arg0 = arg0, Arg1 = arg1, Arg2 = arg2, Arg3 = arg3, Builder = AsyncTaskMethodBuilder<int>.Create(), State = -1 }; multiCallMethodAsyncStateMachine.Builder.Start(ref multiCallMethodAsyncStateMachine); return multiCallMethodAsyncStateMachine.Builder.Task; } } It creates and starts one single state machine, MultiCallMethodAsyncStateMachine: [CompilerGenerated] [StructLayout(LayoutKind.Auto)] internal struct MultiCallMethodAsyncStateMachine : IAsyncStateMachine { public int State; public AsyncTaskMethodBuilder<int> Builder; public int Arg0; public int Arg1; public int Arg2; public int Arg3; public int ResultOfAwait1; public int ResultOfAwait2; public int ResultToReturn; private TaskAwaiter<int> awaiter; void IAsyncStateMachine.MoveNext() { try { switch (this.State) { case -1: HelperMethods.Before(); this.awaiter = AsyncMethods.MethodAsync(this.Arg0, this.Arg1).GetAwaiter(); if (!this.awaiter.IsCompleted) { this.State = 0; this.Builder.AwaitUnsafeOnCompleted(ref this.awaiter, ref this); } break; case 0: this.ResultOfAwait1 = this.awaiter.GetResult(); HelperMethods.Continuation1(this.ResultOfAwait1); this.awaiter = AsyncMethods.MethodAsync(this.Arg2, this.Arg3).GetAwaiter(); if (!this.awaiter.IsCompleted) { this.State = 1; this.Builder.AwaitUnsafeOnCompleted(ref this.awaiter, ref this); } break; case 1: this.ResultOfAwait2 = this.awaiter.GetResult(); HelperMethods.Continuation2(this.ResultOfAwait2); this.ResultToReturn = this.ResultOfAwait1 + this.ResultOfAwait2; this.State = -2; this.Builder.SetResult(this.ResultToReturn); break; } } catch (Exception exception) { this.State = -2; this.Builder.SetException(exception); } } [DebuggerHidden] void IAsyncStateMachine.SetStateMachine(IAsyncStateMachine stateMachine) { this.Builder.SetStateMachine(stateMachine); } } Once again, the above state machine code is already refactored, but it still has a lot of things. More clean up can be done if we only keep the core logic, and the state machine can become very simple: [CompilerGenerated] [StructLayout(LayoutKind.Auto)] internal struct MultiCallMethodAsyncStateMachine : IAsyncStateMachine { // State: // -1: Begin // 0: 1st await is done // 1: 2nd await is done // ... // -2: End public int State; public TaskCompletionSource<int> ResultToReturn; // int resultToReturn ... public int Arg0; // int Arg0 public int Arg1; // int arg1 public int Arg2; // int arg2 public int Arg3; // int arg3 public int ResultOfAwait1; // int resultOfAwait1 ... public int ResultOfAwait2; // int resultOfAwait2 ... private Task<int> currentTaskToAwait; /// <summary> /// Moves the state machine to its next state. /// </summary> public void MoveNext() // IAsyncStateMachine member. { try { switch (this.State) { // Original code is split by "await"s into "case"s: // case -1: // HelperMethods.Before(); // MethodAsync(Arg0, arg1); // case 0: // int resultOfAwait1 = await ... // HelperMethods.Continuation1(resultOfAwait1); // MethodAsync(arg2, arg3); // case 1: // int resultOfAwait2 = await ... // HelperMethods.Continuation2(resultOfAwait2); // int resultToReturn = resultOfAwait1 + resultOfAwait2; // return resultToReturn; case -1: // -1 is begin. HelperMethods.Before(); // Code before 1st await. this.currentTaskToAwait = AsyncMethods.MethodAsync(this.Arg0, this.Arg1); // 1st task to await // When this.currentTaskToAwait is done, run this.MoveNext() and go to case 0. this.State = 0; MultiCallMethodAsyncStateMachine that1 = this; // Cannot use "this" in lambda so create a local variable. this.currentTaskToAwait.ContinueWith(_ => that1.MoveNext()); break; case 0: // Now 1st await is done. this.ResultOfAwait1 = this.currentTaskToAwait.Result; // Get 1st await's result. HelperMethods.Continuation1(this.ResultOfAwait1); // Code after 1st await and before 2nd await. this.currentTaskToAwait = AsyncMethods.MethodAsync(this.Arg2, this.Arg3); // 2nd task to await // When this.currentTaskToAwait is done, run this.MoveNext() and go to case 1. this.State = 1; MultiCallMethodAsyncStateMachine that2 = this; this.currentTaskToAwait.ContinueWith(_ => that2.MoveNext()); break; case 1: // Now 2nd await is done. this.ResultOfAwait2 = this.currentTaskToAwait.Result; // Get 2nd await's result. HelperMethods.Continuation2(this.ResultOfAwait2); // Code after 2nd await. int resultToReturn = this.ResultOfAwait1 + this.ResultOfAwait2; // Code after 2nd await. // End with resultToReturn. this.State = -2; // -2 is end. this.ResultToReturn.SetResult(resultToReturn); break; } } catch (Exception exception) { // End with exception. this.State = -2; // -2 is end. this.ResultToReturn.SetException(exception); } } /// <summary> /// Configures the state machine with a heap-allocated replica. /// </summary> /// <param name="stateMachine">The heap-allocated replica.</param> [DebuggerHidden] public void SetStateMachine(IAsyncStateMachine stateMachine) // IAsyncStateMachine member. { // No core logic. } } Only Task and TaskCompletionSource are involved in this version. And MultiCallMethodAsync() can be simplified to: [DebuggerStepThrough] [AsyncStateMachine(typeof(MultiCallMethodAsyncStateMachine))] // async internal static /*async*/ Task<int> MultiCallMethodAsync(int arg0, int arg1, int arg2, int arg3) { MultiCallMethodAsyncStateMachine multiCallMethodAsyncStateMachine = new MultiCallMethodAsyncStateMachine() { Arg0 = arg0, Arg1 = arg1, Arg2 = arg2, Arg3 = arg3, ResultToReturn = new TaskCompletionSource<int>(), // -1: Begin // 0: 1st await is done // 1: 2nd await is done // ... // -2: End State = -1 }; multiCallMethodAsyncStateMachine.MoveNext(); // Original code are moved into this method. return multiCallMethodAsyncStateMachine.ResultToReturn.Task; } Now the whole state machine becomes very clean - it is about callback: Original code are split into pieces by “await”s, and each piece is put into each “case” in the state machine. Here the 2 awaits split the code into 3 pieces, so there are 3 “case”s. The “piece”s are chained by callback, that is done by Builder.AwaitUnsafeOnCompleted(callback), or currentTaskToAwait.ContinueWith(callback) in the simplified code. A previous “piece” will end with a Task (which is to be awaited), when the task is done, it will callback the next “piece”. The state machine’s state works with the “case”s to ensure the code “piece”s executes one after another. Callback If we focus on the point of callback, the simplification  can go even further – the entire state machine can be completely purged, and we can just keep the code inside MoveNext(). Now MultiCallMethodAsync() becomes: internal static Task<int> MultiCallMethodAsync(int arg0, int arg1, int arg2, int arg3) { TaskCompletionSource<int> taskCompletionSource = new TaskCompletionSource<int>(); try { // Oringinal code begins. HelperMethods.Before(); MethodAsync(arg0, arg1).ContinueWith(await1 => { int resultOfAwait1 = await1.Result; HelperMethods.Continuation1(resultOfAwait1); MethodAsync(arg2, arg3).ContinueWith(await2 => { int resultOfAwait2 = await2.Result; HelperMethods.Continuation2(resultOfAwait2); int resultToReturn = resultOfAwait1 + resultOfAwait2; // Oringinal code ends. taskCompletionSource.SetResult(resultToReturn); }); }); } catch (Exception exception) { taskCompletionSource.SetException(exception); } return taskCompletionSource.Task; } Please compare with the original async / await code: HelperMethods.Before(); int resultOfAwait1 = await MethodAsync(arg0, arg1); HelperMethods.Continuation1(resultOfAwait1); int resultOfAwait2 = await MethodAsync(arg2, arg3); HelperMethods.Continuation2(resultOfAwait2); int resultToReturn = resultOfAwait1 + resultOfAwait2; return resultToReturn; Yeah that is the magic of C# async / await: Await is not to wait. In a await expression, a Task object will be return immediately so that execution is not blocked. The continuation code is compiled as that Task’s callback code. When that task is done, continuation code will execute. Please notice that many details inside the state machine are omitted for simplicity, like context caring, etc. If you want to have a detailed picture, please do check out the source code of AsyncTaskMethodBuilder and TaskAwaiter.

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  • EventDispatcher between an as and an fla?

    - by Christopher Richa
    Hi everyone. I am making a fighting game in Flash and while I have everything running, I am missing something: a victory/loss screen. Logically, I know how to do it: if character.hp < 0 { character.dead = true; dispatchevent("death", event) } My problem is that I have no idea as to how to code it. I know I will use two classes and my two .fla files (unless I am wrong). I have two .fla files that are in play here: the Menu.fla file and the Arena.fla file. Menu.fla contains the entire navigation of the game, options, character selection screens, etc. and when it is time for the player to engage in battle, it loads the Arena.fla file, which contains only the backgrounds (depending on the selected stage) and for now is set to a length of one frame only. For Arena.fla, the real action happens in my classes, but logically, I would only need HP.as and Character.as. In Character.as, I have declared the following variable: var isDead:Boolean = false; //is character dead? In HP.as, believe I should have the following: if(currentHp<0) { currentHp = 0; character.isDead = true; //declared as var `character:Object;` EventDispatcher.dispatchEventListener("playerDead", playerDead); } And finally, in Arena.fla, I want to be able to detect the above-mentioned eventlistener and simply move on to a second frame which will display a message in the style of "PLAYER ONE HAS WON" or "PLAYER ONE HAS LOST" with a button that will allow me to go back to the character selection screen. This is the first part in which I am stuck: how do I detect the dispatched event listener in my main .fla file? Secondly, if the player clicks on the "CONTINUE" button, which displays regardless if the player has won or lost, how can my Menu.fla (which loads the Arena.swf) detect this click event, unload the game, and go back to the character selection screen? Thank you in advance for helping me out. I realize this is a lot of text but it's the most descriptive I can be. If you have any questions or need any clarification concerning my question, feel free to speak up. -Christopher

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  • In org-mode, is there a way to show the number of undone todo items in a subtree when collapsed?

    - by Gerry Lufwansa
    For example, suppose I have this document: * category 1 ** TODO item 1.1 ** not a todo item ** DONE a done todo item ** TODO item 1.4 * category 2 ** not a todo item ** not a todo item * category 3 ** DONE done item * category 4 ** TODO item 4.1 *** TODO subitem 4.1.1 *** TODO subitem 4.1.2 When collapsed, I'd like to see something like: * category 1 (2)... * category 2 (0)... * category 3 (2)... * category 4 (3)...

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  • How can I resolve gstreamer dependencies in Ubuntu

    - by michael
    Hi, Can you please tell me how can I resolve these dependencies on ubuntu: checking for GSTREAMER... configure: error: Package requirements (gstreamer-0.10 >= 0.10 gstreamer-app-0.10 gstreamer-base-0.10 gstreamer-pbutils-0.10 gstreamer-plugins-base-0.10 >= 0.10.25 gstreamer-video-0.10) were not met: No package 'gstreamer-app-0.10' found No package 'gstreamer-pbutils-0.10' found No package 'gstreamer-plugins-base-0.10' found No package 'gstreamer-video-0.10' found I have tried: $ sudo apt-get install *gstreamer-video* Reading package lists... Done Building dependency tree Reading state information... Done E: Regex compilation error - Invalid preceding regular expression $ sudo apt-get install *gstreamer-app* Reading package lists... Done Building dependency tree Reading state information... Done E: Regex compilation error - Invalid preceding regular expression $ sudo apt-get install *gstreamer-base* Reading package lists... Done Building dependency tree Reading state information... Done E: Regex compilation error - Invalid preceding regular expression

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  • Can this way of storing typed objects be improved?

    - by Pindatjuh
    This is an "can it be improved"-question. Topic: Storing typed objects in memory. Background information: I'm building a compiler for the x86-32 Windows platform for my language. My goal includes typed objects. Idea: Every primitive is a semi-class (it can be used as if it was a normal class, but it's stored more compact). Every class is represented by primitives and some meta-data (containing class-properties, inheritance stuff, etc.). The meta-data is complex: it doesn't use fields but instead context-switches. For primitives, the meta-data is very small, compared to a "real" class, which is alot bigger. This enables another idea that "primitives are objects", in my language, which I found nessecairy. Example: If I have an array of 32 booleans, then the pure content of this array is exactly 4 byte (32 bits of booleans). The meta-data will contain flags that the type is an array of booleans, which contains 32 entries. The meta-data is very compacted, on bit-level: using a sort of "packing" mechanism, which is read by a FSM at runtime, when doing inspection of the type (like when passing the object to methods for checking, etc.) For instance (read from left to right, top to bottom, remember vertical position when going to the right, and check nearest column header for meaning of switch): Primitive? Array? Type-Meta 1 Byte? || Size (1 byte) 1 1 [...] 1 [...] done 0 2 Bytes? || Size (2 bytes) 1 [...] done || Size (4 bytes) 0 [...] done Integer? 1 Byte? 2 Bytes? 0 1 0 1 done 1 done 0 done Boolean? Byte? 0 1 0 done 1 done More-Primitives 0 .... Class-Stuff (Huge) 0 ... (After reaching done the data is inserted. || = byte alignment. [...] is variable sized. ... is not described here, for simplicity. And let's call them cost-based-data-structures.) For an array of 32 booleans containing all true values, the memory for this type would be (read top-down): 1 Primitive 1 Array 1 ArrayType: Primitive 0 Not-Array 0 Not-Integer 1 Boolean 0 Not-Byte (thus bit) 1 Integer Size: 1 Byte 00100000 Array size 01010101 01010101 01010101 01010101 Data (user defined) Thus, 8 bytes represent 32 booleans in an array: 11100101 00100000 01010101 01010101 01010101 01010101 How can I improve this? (Both performance- and memory-consumption wise)

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  • Forcing Flex to update the screen?

    - by ABBarton
    This may be a bit of a beginners question, but I can't for the life of me figure it out. I'm using flex to develop a GUI for a large project, specifically a status bar along the bottom. Within my StatusBar class is a ProgressBar, which other classes doing work can tell to update(change bar completion and label) as they progress. The problem I'm encountering is that flex won't update whats shown on the screen until it's too late, for example ProgressBar initialized, 0% done some class sets the ProgressBar to be 12% done some class does some work some class sets the ProgressBar to be 56% done Whats happening is the 12% done is never displaying, it just hangs at 0% during the work, then skips right to 56% done. I've tried to understand the lifecycle of a flex component (invalidation and validation), and I think I understand it and am applying it correctly, but it's not working at all. I need to tell flex to redraw my StatusBar (or at least the ProgressBar within) after some class sets it to be 12% done, but before some class starts doing its work. How do I do this?

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  • Silverlight Cream for March 13, 2010 -- #813

    - by Dave Campbell
    In this Issue: András Velvárt, Bobby Diaz, John Papa/Laurent Bugnion, Jesse Liberty, Christopher Bennage, Tim Greenfield, and Cameron Albert. Shoutouts: Svetla Stoycheva of SilverlightShow has an Interview with SilverlightShow Eco Contest Grand Prize Winner Daniel James Svetla Stoycheva of SilverlightShow also has an Interview with SilverlightShow Eco Contest Community Vote Winner Cigdem Patlak File this under #DoesHeEverSleep, Nokola has an EasyPainter Source Pack 1 Refresh And another filing in the same category by Nokola: EasyPainter Source Pack 2: Flickr, ComboCheckBox and more! In my last pre-#MIX10 'Cream post: From SilverlightCream.com: A Designer-friendly Approach to MVVM András Velvárt has an MVVM tutorial up on SilverlightShow from the Designer perspective of wiring up the View and ViewModel... good stuff my friend! Generate Strongly Typed Observable Events for the Reactive Extensions for .NET (Rx) In an effort to get more familiar with Rx, Bobby Diaz built a WhiteBoard app... there's a demo page plus the source... thanks Bobby! Silverlight TV 13: MVVM Light Toolkit My friend Laurent Bugnion is probably in the air flying to MIX10 right now, but at the MVP Summit last month, he recorded with John Papa and they produced an episode of Silverlight TV for Laurent's MVVM Light ... good stuff guys... see you tomorrow :) WCF Ria Services For Real Jesse Liberty has a great tutorial up on what it takes to get real data into your app ... you know... the stuff you have to get after reading a blog post that uses local stuff :) 1 Simple Step for Commanding in Silverlight Christopher Bennage is discussing Commanding and of course is using Caliburn for the example :) Use Silverlight Reactive Extensions (Rx) to build responsive UIs Tim Greenfield is beginning a two-parter on using Rx. In this first he has a comparison of with and without Rx... cool idea. General Purpose Sprite Class On the heels of Bill Reiss' Sprite posts, Cameron Albert has a General Purpose Sprite class post up using Bill's SilverSprite. Stay in the 'Light! Twitter SilverlightNews | Twitter WynApse | WynApse.com | Tagged Posts | SilverlightCream Join me @ SilverlightCream | Phoenix Silverlight User Group Technorati Tags: Silverlight    Silverlight 3    Silverlight 4    MIX10

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  • I can't upgrade 13.10 because of broken pipe

    - by user212179
    I try upgrading and this is what I get: christopher@chris-computer:~$ sudo apt-get upgrade [sudo] password for christopher: Reading package lists... Done Building dependency tree Reading state information... Done The following packages will be upgraded: librhythmbox-core7 1 upgraded, 0 newly installed, 0 to remove and 0 not upgraded. Need to get 0 B/809 kB of archives. After this operation, 39.9 kB of additional disk space will be used. Do you want to continue [Y/n]? y (Reading database ... 170617 files and directories currently installed.) Preparing to replace librhythmbox-core7 2.99.1-0ubuntu1 (using .../librhythmbox-core7_3.0.1-0~13.10~ppa1_i386.deb) ... Unpacking replacement librhythmbox-core7 ... dpkg: error processing /var/cache/apt/archives/librhythmbox-core7_3.0.1-0~13.10~ppa1_i386.deb (--unpack): trying to overwrite '/usr/lib/librhythmbox-core.so.8.0.0', which is also in package librhythmbox-core8 3.0.1-1ubuntu2~ppa0 No apport report written because MaxReports is reached already dpkg-deb: error: subprocess paste was killed by signal (Broken pipe) Errors were encountered while processing: /var/cache/apt/archives/librhythmbox-core7_3.0.1-0~13.10~ppa1_i386.deb E: Sub-process /usr/bin/dpkg returned an error code (1)

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  • Parallel processing slower than sequential?

    - by zebediah49
    EDIT: For anyone who stumbles upon this in the future: Imagemagick uses a MP library. It's faster to use available cores if they're around, but if you have parallel jobs, it's unhelpful. Do one of the following: do your jobs serially (with Imagemagick in parallel mode) set MAGICK_THREAD_LIMIT=1 for your invocation of the imagemagick binary in question. By making Imagemagick use only one thread, it slows down by 20-30% in my test cases, but meant I could run one job per core without issues, for a significant net increase in performance. Original question: While converting some images using ImageMagick, I noticed a somewhat strange effect. Using xargs was significantly slower than a standard for loop. Since xargs limited to a single process should act like a for loop, I tested that, and found it to be about the same. Thus, we have this demonstration. Quad core (AMD Athalon X4, 2.6GHz) Working entirely on a tempfs (16g ram total; no swap) No other major loads Results: /media/ramdisk/img$ time for f in *.bmp; do echo $f ${f%bmp}png; done | xargs -n 2 -P 1 convert -auto-level real 0m3.784s user 0m2.240s sys 0m0.230s /media/ramdisk/img$ time for f in *.bmp; do echo $f ${f%bmp}png; done | xargs -n 2 -P 2 convert -auto-level real 0m9.097s user 0m28.020s sys 0m0.910s /media/ramdisk/img$ time for f in *.bmp; do echo $f ${f%bmp}png; done | xargs -n 2 -P 10 convert -auto-level real 0m9.844s user 0m33.200s sys 0m1.270s Can anyone think of a reason why running two instances of this program takes more than twice as long in real time, and more than ten times as long in processor time to complete the same task? After that initial hit, more processes do not seem to have as significant of an effect. I thought it might have to do with disk seeking, so I did that test entirely in ram. Could it have something to do with how Convert works, and having more than one copy at once means it cannot use processor cache as efficiently or something? EDIT: When done with 1000x 769KB files, performance is as expected. Interesting. /media/ramdisk/img$ time for f in *.bmp; do echo $f ${f%bmp}png; done | xargs -n 2 -P 1 convert -auto-level real 3m37.679s user 5m6.980s sys 0m6.340s /media/ramdisk/img$ time for f in *.bmp; do echo $f ${f%bmp}png; done | xargs -n 2 -P 1 convert -auto-level real 3m37.152s user 5m6.140s sys 0m6.530s /media/ramdisk/img$ time for f in *.bmp; do echo $f ${f%bmp}png; done | xargs -n 2 -P 2 convert -auto-level real 2m7.578s user 5m35.410s sys 0m6.050s /media/ramdisk/img$ time for f in *.bmp; do echo $f ${f%bmp}png; done | xargs -n 2 -P 4 convert -auto-level real 1m36.959s user 5m48.900s sys 0m6.350s /media/ramdisk/img$ time for f in *.bmp; do echo $f ${f%bmp}png; done | xargs -n 2 -P 10 convert -auto-level real 1m36.392s user 5m54.840s sys 0m5.650s

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