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  • Running a simple integration scenario using the Oracle Big Data Connectors on Hadoop/HDFS cluster

    - by hamsun
    Between the elephant ( the tradional image of the Hadoop framework) and the Oracle Iron Man (Big Data..) an english setter could be seen as the link to the right data Data, Data, Data, we are living in a world where data technology based on popular applications , search engines, Webservers, rich sms messages, email clients, weather forecasts and so on, have a predominant role in our life. More and more technologies are used to analyze/track our behavior, try to detect patterns, to propose us "the best/right user experience" from the Google Ad services, to Telco companies or large consumer sites (like Amazon:) ). The more we use all these technologies, the more we generate data, and thus there is a need of huge data marts and specific hardware/software servers (as the Exadata servers) in order to treat/analyze/understand the trends and offer new services to the users. Some of these "data feeds" are raw, unstructured data, and cannot be processed effectively by normal SQL queries. Large scale distributed processing was an emerging infrastructure need and the solution seemed to be the "collocation of compute nodes with the data", which in turn leaded to MapReduce parallel patterns and the development of the Hadoop framework, which is based on MapReduce and a distributed file system (HDFS) that runs on larger clusters of rather inexpensive servers. Several Oracle products are using the distributed / aggregation pattern for data calculation ( Coherence, NoSql, times ten ) so once that you are familiar with one of these technologies, lets says with coherence aggregators, you will find the whole Hadoop, MapReduce concept very similar. Oracle Big Data Appliance is based on the Cloudera Distribution (CDH), and the Oracle Big Data Connectors can be plugged on a Hadoop cluster running the CDH distribution or equivalent Hadoop clusters. In this paper, a "lab like" implementation of this concept is done on a single Linux X64 server, running an Oracle Database 11g Enterprise Edition Release 11.2.0.4.0, and a single node Apache hadoop-1.2.1 HDFS cluster, using the SQL connector for HDFS. The whole setup is fairly simple: Install on a Linux x64 server ( or virtual box appliance) an Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 server Get the Apache Hadoop distribution from: http://mir2.ovh.net/ftp.apache.org/dist/hadoop/common/hadoop-1.2.1. Get the Oracle Big Data Connectors from: http://www.oracle.com/technetwork/bdc/big-data-connectors/downloads/index.html?ssSourceSiteId=ocomen. Check the java version of your Linux server with the command: java -version java version "1.7.0_40" Java(TM) SE Runtime Environment (build 1.7.0_40-b43) Java HotSpot(TM) 64-Bit Server VM (build 24.0-b56, mixed mode) Decompress the hadoop hadoop-1.2.1.tar.gz file to /u01/hadoop-1.2.1 Modify your .bash_profile export HADOOP_HOME=/u01/hadoop-1.2.1 export PATH=$PATH:$HADOOP_HOME/bin export HIVE_HOME=/u01/hive-0.11.0 export PATH=$PATH:$HADOOP_HOME/bin:$HIVE_HOME/bin (also see my sample .bash_profile) Set up ssh trust for Hadoop process, this is a mandatory step, in our case we have to establish a "local trust" as will are using a single node configuration copy the new public keys to the list of authorized keys connect and test the ssh setup to your localhost: We will run a "pseudo-Hadoop cluster", in what is called "local standalone mode", all the Hadoop java components are running in one Java process, this is enough for our demo purposes. We need to "fine tune" some Hadoop configuration files, we have to go at our $HADOOP_HOME/conf, and modify the files: core-site.xml hdfs-site.xml mapred-site.xml check that the hadoop binaries are referenced correctly from the command line by executing: hadoop -version As Hadoop is managing our "clustered HDFS" file system we have to create "the mount point" and format it , the mount point will be declared to core-site.xml as: The layout under the /u01/hadoop-1.2.1/data will be created and used by other hadoop components (MapReduce = /mapred/...) HDFS is using the /dfs/... layout structure format the HDFS hadoop file system: Start the java components for the HDFS system As an additional check, you can use the GUI Hadoop browsers to check the content of your HDFS configurations: Once our HDFS Hadoop setup is done you can use the HDFS file system to store data ( big data : )), and plug them back and forth to Oracle Databases by the means of the Big Data Connectors ( which is the next configuration step). You can create / use a Hive db, but in our case we will make a simple integration of "raw data" , through the creation of an External Table to a local Oracle instance ( on the same Linux box, we run the Hadoop HDFS one node cluster and one Oracle DB). Download some public "big data", I use the site: http://france.meteofrance.com/france/observations, from where I can get *.csv files for my big data simulations :). Here is the data layout of my example file: Download the Big Data Connector from the OTN (oraosch-2.2.0.zip), unzip it to your local file system (see picture below) Modify your environment in order to access the connector libraries , and make the following test: [oracle@dg1 bin]$./hdfs_stream Usage: hdfs_stream locationFile [oracle@dg1 bin]$ Load the data to the Hadoop hdfs file system: hadoop fs -mkdir bgtest_data hadoop fs -put obsFrance.txt bgtest_data/obsFrance.txt hadoop fs -ls /user/oracle/bgtest_data/obsFrance.txt [oracle@dg1 bg-data-raw]$ hadoop fs -ls /user/oracle/bgtest_data/obsFrance.txt Found 1 items -rw-r--r-- 1 oracle supergroup 54103 2013-10-22 06:10 /user/oracle/bgtest_data/obsFrance.txt [oracle@dg1 bg-data-raw]$hadoop fs -ls hdfs:///user/oracle/bgtest_data/obsFrance.txt Found 1 items -rw-r--r-- 1 oracle supergroup 54103 2013-10-22 06:10 /user/oracle/bgtest_data/obsFrance.txt Check the content of the HDFS with the browser UI: Start the Oracle database, and run the following script in order to create the Oracle database user, the Oracle directories for the Oracle Big Data Connector (dg1 it’s my own db id replace accordingly yours): #!/bin/bash export ORAENV_ASK=NO export ORACLE_SID=dg1 . oraenv sqlplus /nolog <<EOF CONNECT / AS sysdba; CREATE OR REPLACE DIRECTORY osch_bin_path AS '/u01/orahdfs-2.2.0/bin'; CREATE USER BGUSER IDENTIFIED BY oracle; GRANT CREATE SESSION, CREATE TABLE TO BGUSER; GRANT EXECUTE ON sys.utl_file TO BGUSER; GRANT READ, EXECUTE ON DIRECTORY osch_bin_path TO BGUSER; CREATE OR REPLACE DIRECTORY BGT_LOG_DIR as '/u01/BG_TEST/logs'; GRANT READ, WRITE ON DIRECTORY BGT_LOG_DIR to BGUSER; CREATE OR REPLACE DIRECTORY BGT_DATA_DIR as '/u01/BG_TEST/data'; GRANT READ, WRITE ON DIRECTORY BGT_DATA_DIR to BGUSER; EOF Put the following in a file named t3.sh and make it executable, hadoop jar $OSCH_HOME/jlib/orahdfs.jar \ oracle.hadoop.exttab.ExternalTable \ -D oracle.hadoop.exttab.tableName=BGTEST_DP_XTAB \ -D oracle.hadoop.exttab.defaultDirectory=BGT_DATA_DIR \ -D oracle.hadoop.exttab.dataPaths="hdfs:///user/oracle/bgtest_data/obsFrance.txt" \ -D oracle.hadoop.exttab.columnCount=7 \ -D oracle.hadoop.connection.url=jdbc:oracle:thin:@//localhost:1521/dg1 \ -D oracle.hadoop.connection.user=BGUSER \ -D oracle.hadoop.exttab.printStackTrace=true \ -createTable --noexecute then test the creation fo the external table with it: [oracle@dg1 samples]$ ./t3.sh ./t3.sh: line 2: /u01/orahdfs-2.2.0: Is a directory Oracle SQL Connector for HDFS Release 2.2.0 - Production Copyright (c) 2011, 2013, Oracle and/or its affiliates. All rights reserved. Enter Database Password:] The create table command was not executed. The following table would be created. CREATE TABLE "BGUSER"."BGTEST_DP_XTAB" ( "C1" VARCHAR2(4000), "C2" VARCHAR2(4000), "C3" VARCHAR2(4000), "C4" VARCHAR2(4000), "C5" VARCHAR2(4000), "C6" VARCHAR2(4000), "C7" VARCHAR2(4000) ) ORGANIZATION EXTERNAL ( TYPE ORACLE_LOADER DEFAULT DIRECTORY "BGT_DATA_DIR" ACCESS PARAMETERS ( RECORDS DELIMITED BY 0X'0A' CHARACTERSET AL32UTF8 STRING SIZES ARE IN CHARACTERS PREPROCESSOR "OSCH_BIN_PATH":'hdfs_stream' FIELDS TERMINATED BY 0X'2C' MISSING FIELD VALUES ARE NULL ( "C1" CHAR(4000), "C2" CHAR(4000), "C3" CHAR(4000), "C4" CHAR(4000), "C5" CHAR(4000), "C6" CHAR(4000), "C7" CHAR(4000) ) ) LOCATION ( 'osch-20131022081035-74-1' ) ) PARALLEL REJECT LIMIT UNLIMITED; The following location files would be created. osch-20131022081035-74-1 contains 1 URI, 54103 bytes 54103 hdfs://localhost:19000/user/oracle/bgtest_data/obsFrance.txt Then remove the --noexecute flag and create the external Oracle table for the Hadoop data. Check the results: The create table command succeeded. CREATE TABLE "BGUSER"."BGTEST_DP_XTAB" ( "C1" VARCHAR2(4000), "C2" VARCHAR2(4000), "C3" VARCHAR2(4000), "C4" VARCHAR2(4000), "C5" VARCHAR2(4000), "C6" VARCHAR2(4000), "C7" VARCHAR2(4000) ) ORGANIZATION EXTERNAL ( TYPE ORACLE_LOADER DEFAULT DIRECTORY "BGT_DATA_DIR" ACCESS PARAMETERS ( RECORDS DELIMITED BY 0X'0A' CHARACTERSET AL32UTF8 STRING SIZES ARE IN CHARACTERS PREPROCESSOR "OSCH_BIN_PATH":'hdfs_stream' FIELDS TERMINATED BY 0X'2C' MISSING FIELD VALUES ARE NULL ( "C1" CHAR(4000), "C2" CHAR(4000), "C3" CHAR(4000), "C4" CHAR(4000), "C5" CHAR(4000), "C6" CHAR(4000), "C7" CHAR(4000) ) ) LOCATION ( 'osch-20131022081719-3239-1' ) ) PARALLEL REJECT LIMIT UNLIMITED; The following location files were created. osch-20131022081719-3239-1 contains 1 URI, 54103 bytes 54103 hdfs://localhost:19000/user/oracle/bgtest_data/obsFrance.txt This is the view from the SQL Developer: and finally the number of lines in the oracle table, imported from our Hadoop HDFS cluster SQL select count(*) from "BGUSER"."BGTEST_DP_XTAB"; COUNT(*) ---------- 1151 In a next post we will integrate data from a Hive database, and try some ODI integrations with the ODI Big Data connector. Our simplistic approach is just a step to show you how these unstructured data world can be integrated to Oracle infrastructure. Hadoop, BigData, NoSql are great technologies, they are widely used and Oracle is offering a large integration infrastructure based on these services. Oracle University presents a complete curriculum on all the Oracle related technologies: NoSQL: Introduction to Oracle NoSQL Database Using Oracle NoSQL Database Big Data: Introduction to Big Data Oracle Big Data Essentials Oracle Big Data Overview Oracle Data Integrator: Oracle Data Integrator 12c: New Features Oracle Data Integrator 11g: Integration and Administration Oracle Data Integrator: Administration and Development Oracle Data Integrator 11g: Advanced Integration and Development Oracle Coherence 12c: Oracle Coherence 12c: New Features Oracle Coherence 12c: Share and Manage Data in Clusters Oracle Coherence 12c: Oracle GoldenGate 11g: Fundamentals for Oracle Oracle GoldenGate 11g: Fundamentals for SQL Server Oracle GoldenGate 11g Fundamentals for Oracle Oracle GoldenGate 11g Fundamentals for DB2 Oracle GoldenGate 11g Fundamentals for Teradata Oracle GoldenGate 11g Fundamentals for HP NonStop Oracle GoldenGate 11g Management Pack: Overview Oracle GoldenGate 11g Troubleshooting and Tuning Oracle GoldenGate 11g: Advanced Configuration for Oracle Other Resources: Apache Hadoop : http://hadoop.apache.org/ is the homepage for these technologies. "Hadoop Definitive Guide 3rdEdition" by Tom White is a classical lecture for people who want to know more about Hadoop , and some active "googling " will also give you some more references. About the author: Eugene Simos is based in France and joined Oracle through the BEA-Weblogic Acquisition, where he worked for the Professional Service, Support, end Education for major accounts across the EMEA Region. He worked in the banking sector, ATT, Telco companies giving him extensive experience on production environments. Eugen currently specializes in Oracle Fusion Middleware teaching an array of courses on Weblogic/Webcenter, Content,BPM /SOA/Identity-Security/GoldenGate/Virtualisation/Unified Comm Suite) throughout the EMEA region.

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  • Got an idea for an application, but part of it is patented, any suggestions?

    - by tekiegreg
    Hi there, so I've been working on developing an idea for an application that I think has the potential to be successful, however after some initial research I've discovered that at least part of my ideas are covered by a patent out there, the patent in particular is held by a really large company (I don't want to give away specifics for fear I'd draw their attention for sure). I'm debating a few options: 1) Develop patents around my ideas that don't conflict and maybe approach the company in question for a license exchange 2) Just approach them for a license outright 3) Just develop around it anyways and hope for the best :-p What have other people done in these situations? Are companies generally willing to grant patent licenses? Are they willing to grant them at reasonable prices? Thoughts?

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  • Do NOT remove the reference to System.Core from your VS2010 Project

    - by Lee Brandt
    One of the things I routinely do when adding a new class library project, is remove all references and just add them back in as I need them. That is NOT a good idea for Visual Studio 2010. When I DID need System.Core, and went to add it back, this is what I got: "A reference to 'System.Core' could not be added. This component is automatically referenced..." After some Googling I found this article: http://connect.microsoft.com/VisualStudio/feedback/details/525663/cannot-remove-system-core-dll-reference-from-a-vs2010-project It tells you to add it back manually. Here is the part that needs back in the project file. After the last PropertyGroup node, add this node:   <ItemGroup>     <Reference Include="System.Core" />   </ItemGroup> You should be good to go again. Hope this helps.

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  • arp problems with transparent bridge on linux

    - by Mink
    I've been trying to secure my virtual machines on my esx server by putting them behind a transparent bridge with 2 interfaces, one in front, one at the back. My intention is to put all the firewall rules in one place (instead of on each virtual server). I've been using as bridge a blank new virtual machine based on arch linux (but I suspect it doesn't matter which brand of linux it is). What I have is 2 virtual switchs (thus two Virtual Network, VN_front and VN_back), each with 2 types of ports (switched/separated or promiscious/where the machine can see all packets). On my bridge machine, I've set up 2 virtual NIC, one on VN_front, one on VN_back, both in promisc mode. I've created a bridge br0 with both NIC in it: brctl addbr br0 brctl stp br0 off brctl addif br0 front_if brctl addif br0 back_if Then brought them up: ifconfig front_if 0.0.0.0 promisc ifconfig back_if 0.0.0.0 promisc ifconfig br0 0.0.0.0 (I use promisc mode, because I'm not sure I can do without, thinking that maybe the packets don't reach the NICs) Then I took one of my virtual server sitting on VN_front, and plugged it to VN_back instead (that's the nifty use case I'm thinking about, being able to move my servers around just by changing the VN they are plugged into, without changing anything in the configuration). Then I looked into the macs "seen" by my addressless bridge using brctl showmacs br0 and it did show my server from both sides: I get something that looks like this : port no mac addr is local? ageing timer 2 00:0c:29:e1:54:75 no 9.27 1 00:0c:29:fd:86:0c no 9.27 2 00:50:56:90:05:86 no 73.38 1 00:50:56:90:05:88 no 0.10 2 00:50:56:90:05:8b yes 0.00 << FRONT VN 1 00:50:56:90:05:8c yes 0.00 << BACK VN 2 00:50:56:90:19:18 no 13.55 2 00:50:56:90:3c:cf no 13.57 the thing is that the server that are plugged in front/back are not shown on the correct port. I suspect some horrible thing happening in the ARP-world... :-/ If I ping from a front virtual server to a back virtual server, I can only see the back machine if that back machine pings something in the front. As soon as I stop the ping from the back machine, the ping from the front machine stops getting through... I've noticed that if the back machine pings, then its port on the bridge is the correct one... I've tried to play with the arp_ switch of /proc/sys, but with no clear effect on the end result... /proc/sys/net/ipv4/ip_forward doesn't seem to be of any use when using a bridge (seems it's all taken care of by brctl) /proc/sys/net/ipv4/conf//arp_ don't seem to change much either... (tried arp_announce to 2 or 8 - like suggested elsewhere - and arp_ignore to 0 or 1 ) All the examples I've seen have a different subnet on either side like 10.0.1.0/24 and 10.0.2.0/24... In my case I want 10.0.1.0/24 on both side (just like a transparent switch - except it's a hidden fw ). Turning stp on/off doesn't seem to have any impact on my issue. It's as if the arp packets where getting through the bridge, corrupting the other side with false data... I've tried to use the -arp on each interface, br0, front, back... it breaks the thing altogether... I suspect it has something to do with both side being on the same subnet... I've thought about putting all my machine behind the fw, so as to have all the same subnet at the back... but I'm stuck with my provider's gateway standing at the front with part of my subnet (in fact 3 appliance to route the whole subnet), so I'll always have ips from the same subnet on both side, whatever I do... (I'm using fixed front IPs on my delegated subnet). I'm at a loss... -_-'' Thx for your help. (As anyone tried something like this? from within ESXi?) (It's not just a stunt, the idea is to have something like fail2ban running on some servers, sending their banned IP to the bridge/fw so that it too could ban them - saving all the other servers from that same attacker in one go, allowing for some honeypot that would trigger the fw from any kind of suitable response, and stuffs of the sort... I am aware I could use something like snort, but it addresses some completely different kind of problems, in a completely different way... )

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  • Advice Needed: Developers blocked by waiting on code to merge from another branch using GitFlow

    - by fogwolf
    Our team just made the switch from FogBugz & Kiln/Mercurial to Jira & Stash/Git. We are using the Git Flow model for branching, adding subtask branches off of feature branches (relating to Jira subtasks of Jira features). We are using Stash to assign a reviewer when we create a pull request to merge back into the parent branch (usually develop but for subtasks back into the feature branch). The problem we're finding is that even with the best planning and breakdown of feature cases, when multiple developers are working together on the same feature, say on the front-end and back-end, if they are working on interdependent code that is in separate branches one developer ends up blocking the other. We've tried pulling between each others' branches as we develop. We've also tried creating local integration branches each developer can pull from multiple branches to test the integration as they develop. Finally, and this seems to work possibly the best for us so far, though with a bit more overhead, we have tried creating an integration branch off of the feature branch right off the bat. When a subtask branch (off of the feature branch) is ready for a pull request and code review, we also manually merge those change sets into this feature integration branch. Then all interested developers are able to pull from that integration branch into other dependent subtask branches. This prevents anyone from waiting for any branch they are dependent upon to pass code review. I know this isn't necessarily a Git issue - it has to do with working on interdependent code in multiple branches, mixed with our own work process and culture. If we didn't have the strict code-review policy for develop (true integration branch) then developer 1 could merge to develop for developer 2 to pull from. Another complication is that we are also required to do some preliminary testing as part of the code review process before handing the feature off to QA.This means that even if front-end developer 1 is pulling directly from back-end developer 2's branch as they go, if back-end developer 2 finishes and his/her pull request is sitting in code review for a week, then front-end developer 2 technically can't create his pull request/code review because his/her code reviewer can't test because back-end developer 2's code hasn't been merged into develop yet. Bottom line is we're finding ourselves in a much more serial rather than parallel approach in these instance, depending on which route we go, and would like to find a process to use to avoid this. Last thing I'll mention is we realize by sharing code across branches that haven't been code reviewed and finalized yet we are in essence using the beta code of others. To a certain extent I don't think we can avoid that and are willing to accept that to a degree. Anyway, any ideas, input, etc... greatly appreciated. Thanks!

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  • PTLQueue : a scalable bounded-capacity MPMC queue

    - by Dave
    Title: Fast concurrent MPMC queue -- I've used the following concurrent queue algorithm enough that it warrants a blog entry. I'll sketch out the design of a fast and scalable multiple-producer multiple-consumer (MPSC) concurrent queue called PTLQueue. The queue has bounded capacity and is implemented via a circular array. Bounded capacity can be a useful property if there's a mismatch between producer rates and consumer rates where an unbounded queue might otherwise result in excessive memory consumption by virtue of the container nodes that -- in some queue implementations -- are used to hold values. A bounded-capacity queue can provide flow control between components. Beware, however, that bounded collections can also result in resource deadlock if abused. The put() and take() operators are partial and wait for the collection to become non-full or non-empty, respectively. Put() and take() do not allocate memory, and are not vulnerable to the ABA pathologies. The PTLQueue algorithm can be implemented equally well in C/C++ and Java. Partial operators are often more convenient than total methods. In many use cases if the preconditions aren't met, there's nothing else useful the thread can do, so it may as well wait via a partial method. An exception is in the case of work-stealing queues where a thief might scan a set of queues from which it could potentially steal. Total methods return ASAP with a success-failure indication. (It's tempting to describe a queue or API as blocking or non-blocking instead of partial or total, but non-blocking is already an overloaded concurrency term. Perhaps waiting/non-waiting or patient/impatient might be better terms). It's also trivial to construct partial operators by busy-waiting via total operators, but such constructs may be less efficient than an operator explicitly and intentionally designed to wait. A PTLQueue instance contains an array of slots, where each slot has volatile Turn and MailBox fields. The array has power-of-two length allowing mod/div operations to be replaced by masking. We assume sensible padding and alignment to reduce the impact of false sharing. (On x86 I recommend 128-byte alignment and padding because of the adjacent-sector prefetch facility). Each queue also has PutCursor and TakeCursor cursor variables, each of which should be sequestered as the sole occupant of a cache line or sector. You can opt to use 64-bit integers if concerned about wrap-around aliasing in the cursor variables. Put(null) is considered illegal, but the caller or implementation can easily check for and convert null to a distinguished non-null proxy value if null happens to be a value you'd like to pass. Take() will accordingly convert the proxy value back to null. An advantage of PTLQueue is that you can use atomic fetch-and-increment for the partial methods. We initialize each slot at index I with (Turn=I, MailBox=null). Both cursors are initially 0. All shared variables are considered "volatile" and atomics such as CAS and AtomicFetchAndIncrement are presumed to have bidirectional fence semantics. Finally T is the templated type. I've sketched out a total tryTake() method below that allows the caller to poll the queue. tryPut() has an analogous construction. Zebra stripping : alternating row colors for nice-looking code listings. See also google code "prettify" : https://code.google.com/p/google-code-prettify/ Prettify is a javascript module that yields the HTML/CSS/JS equivalent of pretty-print. -- pre:nth-child(odd) { background-color:#ff0000; } pre:nth-child(even) { background-color:#0000ff; } border-left: 11px solid #ccc; margin: 1.7em 0 1.7em 0.3em; background-color:#BFB; font-size:12px; line-height:65%; " // PTLQueue : Put(v) : // producer : partial method - waits as necessary assert v != null assert Mask = 1 && (Mask & (Mask+1)) == 0 // Document invariants // doorway step // Obtain a sequence number -- ticket // As a practical concern the ticket value is temporally unique // The ticket also identifies and selects a slot auto tkt = AtomicFetchIncrement (&PutCursor, 1) slot * s = &Slots[tkt & Mask] // waiting phase : // wait for slot's generation to match the tkt value assigned to this put() invocation. // The "generation" is implicitly encoded as the upper bits in the cursor // above those used to specify the index : tkt div (Mask+1) // The generation serves as an epoch number to identify a cohort of threads // accessing disjoint slots while s-Turn != tkt : Pause assert s-MailBox == null s-MailBox = v // deposit and pass message Take() : // consumer : partial method - waits as necessary auto tkt = AtomicFetchIncrement (&TakeCursor,1) slot * s = &Slots[tkt & Mask] // 2-stage waiting : // First wait for turn for our generation // Acquire exclusive "take" access to slot's MailBox field // Then wait for the slot to become occupied while s-Turn != tkt : Pause // Concurrency in this section of code is now reduced to just 1 producer thread // vs 1 consumer thread. // For a given queue and slot, there will be most one Take() operation running // in this section. // Consumer waits for producer to arrive and make slot non-empty // Extract message; clear mailbox; advance Turn indicator // We have an obvious happens-before relation : // Put(m) happens-before corresponding Take() that returns that same "m" for T v = s-MailBox if v != null : s-MailBox = null ST-ST barrier s-Turn = tkt + Mask + 1 // unlock slot to admit next producer and consumer return v Pause tryTake() : // total method - returns ASAP with failure indication for auto tkt = TakeCursor slot * s = &Slots[tkt & Mask] if s-Turn != tkt : return null T v = s-MailBox // presumptive return value if v == null : return null // ratify tkt and v values and commit by advancing cursor if CAS (&TakeCursor, tkt, tkt+1) != tkt : continue s-MailBox = null ST-ST barrier s-Turn = tkt + Mask + 1 return v The basic idea derives from the Partitioned Ticket Lock "PTL" (US20120240126-A1) and the MultiLane Concurrent Bag (US8689237). The latter is essentially a circular ring-buffer where the elements themselves are queues or concurrent collections. You can think of the PTLQueue as a partitioned ticket lock "PTL" augmented to pass values from lock to unlock via the slots. Alternatively, you could conceptualize of PTLQueue as a degenerate MultiLane bag where each slot or "lane" consists of a simple single-word MailBox instead of a general queue. Each lane in PTLQueue also has a private Turn field which acts like the Turn (Grant) variables found in PTL. Turn enforces strict FIFO ordering and restricts concurrency on the slot mailbox field to at most one simultaneous put() and take() operation. PTL uses a single "ticket" variable and per-slot Turn (grant) fields while MultiLane has distinct PutCursor and TakeCursor cursors and abstract per-slot sub-queues. Both PTL and MultiLane advance their cursor and ticket variables with atomic fetch-and-increment. PTLQueue borrows from both PTL and MultiLane and has distinct put and take cursors and per-slot Turn fields. Instead of a per-slot queues, PTLQueue uses a simple single-word MailBox field. PutCursor and TakeCursor act like a pair of ticket locks, conferring "put" and "take" access to a given slot. PutCursor, for instance, assigns an incoming put() request to a slot and serves as a PTL "Ticket" to acquire "put" permission to that slot's MailBox field. To better explain the operation of PTLQueue we deconstruct the operation of put() and take() as follows. Put() first increments PutCursor obtaining a new unique ticket. That ticket value also identifies a slot. Put() next waits for that slot's Turn field to match that ticket value. This is tantamount to using a PTL to acquire "put" permission on the slot's MailBox field. Finally, having obtained exclusive "put" permission on the slot, put() stores the message value into the slot's MailBox. Take() similarly advances TakeCursor, identifying a slot, and then acquires and secures "take" permission on a slot by waiting for Turn. Take() then waits for the slot's MailBox to become non-empty, extracts the message, and clears MailBox. Finally, take() advances the slot's Turn field, which releases both "put" and "take" access to the slot's MailBox. Note the asymmetry : put() acquires "put" access to the slot, but take() releases that lock. At any given time, for a given slot in a PTLQueue, at most one thread has "put" access and at most one thread has "take" access. This restricts concurrency from general MPMC to 1-vs-1. We have 2 ticket locks -- one for put() and one for take() -- each with its own "ticket" variable in the form of the corresponding cursor, but they share a single "Grant" egress variable in the form of the slot's Turn variable. Advancing the PutCursor, for instance, serves two purposes. First, we obtain a unique ticket which identifies a slot. Second, incrementing the cursor is the doorway protocol step to acquire the per-slot mutual exclusion "put" lock. The cursors and operations to increment those cursors serve double-duty : slot-selection and ticket assignment for locking the slot's MailBox field. At any given time a slot MailBox field can be in one of the following states: empty with no pending operations -- neutral state; empty with one or more waiting take() operations pending -- deficit; occupied with no pending operations; occupied with one or more waiting put() operations -- surplus; empty with a pending put() or pending put() and take() operations -- transitional; or occupied with a pending take() or pending put() and take() operations -- transitional. The partial put() and take() operators can be implemented with an atomic fetch-and-increment operation, which may confer a performance advantage over a CAS-based loop. In addition we have independent PutCursor and TakeCursor cursors. Critically, a put() operation modifies PutCursor but does not access the TakeCursor and a take() operation modifies the TakeCursor cursor but does not access the PutCursor. This acts to reduce coherence traffic relative to some other queue designs. It's worth noting that slow threads or obstruction in one slot (or "lane") does not impede or obstruct operations in other slots -- this gives us some degree of obstruction isolation. PTLQueue is not lock-free, however. The implementation above is expressed with polite busy-waiting (Pause) but it's trivial to implement per-slot parking and unparking to deschedule waiting threads. It's also easy to convert the queue to a more general deque by replacing the PutCursor and TakeCursor cursors with Left/Front and Right/Back cursors that can move either direction. Specifically, to push and pop from the "left" side of the deque we would decrement and increment the Left cursor, respectively, and to push and pop from the "right" side of the deque we would increment and decrement the Right cursor, respectively. We used a variation of PTLQueue for message passing in our recent OPODIS 2013 paper. ul { list-style:none; padding-left:0; padding:0; margin:0; margin-left:0; } ul#myTagID { padding: 0px; margin: 0px; list-style:none; margin-left:0;} -- -- There's quite a bit of related literature in this area. I'll call out a few relevant references: Wilson's NYU Courant Institute UltraComputer dissertation from 1988 is classic and the canonical starting point : Operating System Data Structures for Shared-Memory MIMD Machines with Fetch-and-Add. Regarding provenance and priority, I think PTLQueue or queues effectively equivalent to PTLQueue have been independently rediscovered a number of times. See CB-Queue and BNPBV, below, for instance. But Wilson's dissertation anticipates the basic idea and seems to predate all the others. Gottlieb et al : Basic Techniques for the Efficient Coordination of Very Large Numbers of Cooperating Sequential Processors Orozco et al : CB-Queue in Toward high-throughput algorithms on many-core architectures which appeared in TACO 2012. Meneghin et al : BNPVB family in Performance evaluation of inter-thread communication mechanisms on multicore/multithreaded architecture Dmitry Vyukov : bounded MPMC queue (highly recommended) Alex Otenko : US8607249 (highly related). John Mellor-Crummey : Concurrent queues: Practical fetch-and-phi algorithms. Technical Report 229, Department of Computer Science, University of Rochester Thomasson : FIFO Distributed Bakery Algorithm (very similar to PTLQueue). Scott and Scherer : Dual Data Structures I'll propose an optimization left as an exercise for the reader. Say we wanted to reduce memory usage by eliminating inter-slot padding. Such padding is usually "dark" memory and otherwise unused and wasted. But eliminating the padding leaves us at risk of increased false sharing. Furthermore lets say it was usually the case that the PutCursor and TakeCursor were numerically close to each other. (That's true in some use cases). We might still reduce false sharing by incrementing the cursors by some value other than 1 that is not trivially small and is coprime with the number of slots. Alternatively, we might increment the cursor by one and mask as usual, resulting in a logical index. We then use that logical index value to index into a permutation table, yielding an effective index for use in the slot array. The permutation table would be constructed so that nearby logical indices would map to more distant effective indices. (Open question: what should that permutation look like? Possibly some perversion of a Gray code or De Bruijn sequence might be suitable). As an aside, say we need to busy-wait for some condition as follows : "while C == 0 : Pause". Lets say that C is usually non-zero, so we typically don't wait. But when C happens to be 0 we'll have to spin for some period, possibly brief. We can arrange for the code to be more machine-friendly with respect to the branch predictors by transforming the loop into : "if C == 0 : for { Pause; if C != 0 : break; }". Critically, we want to restructure the loop so there's one branch that controls entry and another that controls loop exit. A concern is that your compiler or JIT might be clever enough to transform this back to "while C == 0 : Pause". You can sometimes avoid this by inserting a call to a some type of very cheap "opaque" method that the compiler can't elide or reorder. On Solaris, for instance, you could use :"if C == 0 : { gethrtime(); for { Pause; if C != 0 : break; }}". It's worth noting the obvious duality between locks and queues. If you have strict FIFO lock implementation with local spinning and succession by direct handoff such as MCS or CLH,then you can usually transform that lock into a queue. Hidden commentary and annotations - invisible : * And of course there's a well-known duality between queues and locks, but I'll leave that topic for another blog post. * Compare and contrast : PTLQ vs PTL and MultiLane * Equivalent : Turn; seq; sequence; pos; position; ticket * Put = Lock; Deposit Take = identify and reserve slot; wait; extract & clear; unlock * conceptualize : Distinct PutLock and TakeLock implemented as ticket lock or PTL Distinct arrival cursors but share per-slot "Turn" variable provides exclusive role-based access to slot's mailbox field put() acquires exclusive access to a slot for purposes of "deposit" assigns slot round-robin and then acquires deposit access rights/perms to that slot take() acquires exclusive access to slot for purposes of "withdrawal" assigns slot round-robin and then acquires withdrawal access rights/perms to that slot At any given time, only one thread can have withdrawal access to a slot at any given time, only one thread can have deposit access to a slot Permissible for T1 to have deposit access and T2 to simultaneously have withdrawal access * round-robin for the purposes of; role-based; access mode; access role mailslot; mailbox; allocate/assign/identify slot rights; permission; license; access permission; * PTL/Ticket hybrid Asymmetric usage ; owner oblivious lock-unlock pairing K-exclusion add Grant cursor pass message m from lock to unlock via Slots[] array Cursor performs 2 functions : + PTL ticket + Assigns request to slot in round-robin fashion Deconstruct protocol : explication put() : allocate slot in round-robin fashion acquire PTL for "put" access store message into slot associated with PTL index take() : Acquire PTL for "take" access // doorway step seq = fetchAdd (&Grant, 1) s = &Slots[seq & Mask] // waiting phase while s-Turn != seq : pause Extract : wait for s-mailbox to be full v = s-mailbox s-mailbox = null Release PTL for both "put" and "take" access s-Turn = seq + Mask + 1 * Slot round-robin assignment and lock "doorway" protocol leverage the same cursor and FetchAdd operation on that cursor FetchAdd (&Cursor,1) + round-robin slot assignment and dispersal + PTL/ticket lock "doorway" step waiting phase is via "Turn" field in slot * PTLQueue uses 2 cursors -- put and take. Acquire "put" access to slot via PTL-like lock Acquire "take" access to slot via PTL-like lock 2 locks : put and take -- at most one thread can access slot's mailbox Both locks use same "turn" field Like multilane : 2 cursors : put and take slot is simple 1-capacity mailbox instead of queue Borrow per-slot turn/grant from PTL Provides strict FIFO Lock slot : put-vs-put take-vs-take at most one put accesses slot at any one time at most one put accesses take at any one time reduction to 1-vs-1 instead of N-vs-M concurrency Per slot locks for put/take Release put/take by advancing turn * is instrumental in ... * P-V Semaphore vs lock vs K-exclusion * See also : FastQueues-excerpt.java dice-etc/queue-mpmc-bounded-blocking-circular-xadd/ * PTLQueue is the same as PTLQB - identical * Expedient return; ASAP; prompt; immediately * Lamport's Bakery algorithm : doorway step then waiting phase Threads arriving at doorway obtain a unique ticket number Threads enter in ticket order * In the terminology of Reed and Kanodia a ticket lock corresponds to the busy-wait implementation of a semaphore using an eventcount and a sequencer It can also be thought of as an optimization of Lamport's bakery lock was designed for fault-tolerance rather than performance Instead of spinning on the release counter, processors using a bakery lock repeatedly examine the tickets of their peers --

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  • SQL SERVER – Rollback TRUNCATE Command in Transaction

    - by pinaldave
    This is very common concept that truncate can not be rolled back. I always hear conversation between developer if truncate can be rolled back or not. If you use TRANSACTIONS in your code, TRUNCATE can be rolled back. If there is no transaction is used and TRUNCATE operation is committed, it can not be retrieved from [...]

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  • How to switch to user perspective in Blender

    - by Cyanophage
    I've just started using Blender (v2.63) for the first time. I have used a lot of 3d modelling programs in the past but Blender's controls seem to be set up differently and it's taking a while to get used to it. The thing that is really bugging me at the moment is switching from user perspective to front/side/top views. I have my view in perspective mode and I want to switch to front view in orthographic mode and then switch back to the view I had before. It seems that the only way is to press numpad-0 to go to camera view, rotate the screen a bit to get rid of the annoying black outline and then switch it back to perspective mode. Then sometimes when I go back to front view it's in perspective mode which is annoying as you never want front view in perspective, only orthographic mode. My question: Is there a way I can be in my user view in perspective mode, switch to front/side/top views in orthographic mode and then switch back to where I was before in my user mode and be back in perspective mode?

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  • Welcome to Jackstown

    - by fatherjack
    I live in a small town, the population count isn't that great but let me introduce you to some of the population. We'll start with Martin the Doc, he fixes up anything that gets poorly, so much so that he could be classed as the doctor, the vet and even the garage mechanic. He's got a reputation that he can fix anything and that hasn't been proved wrong yet. He's great friends with Brian (who gets called "Brains") the teacher who seems to have a sound understanding of any topic you care to pass his way. If he isn't sure he tells you and then goes to find out and comes back with a full answer real quick. Its good to have that sort of research capability close at hand. Brains is also great at encouraging anyone who needs a bit of support to get them up to speed and working on their jobs. Steve sees Brains regularly, that's because he is the librarian, he keeps all sorts of reading material and nowadays there's even video to watch about any topic you like. Steve keeps scouring all sorts of places to get the content that's needed and he keeps it in good order so that what ever is needed can be found quickly. He also has to make sure that old stuff gets marked as probably out of date so that anyone reading it wont get mislead. Over the road from him is Greg, he's the town crier. We don't have a newspaper here so Greg keeps us all informed of what's going on "out of town" - what new stuff we might make use of and what wont work in a small place like this. If we are interested he goes ahead and gets people in to demonstrate their products  and tell us about the details. Greg is pretty good at getting us discounts too. Now Greg's brother Ian works for the mayors office in the "waste management department" nowadays its all about the recycling but he still has to make sure that the stuff that cant be used any more gets disposed of properly. It depends on the type of waste he's dealing with that decides how it need to be treated and he has to know a lot about the different methods and when to use which ones. There are two people that keep the peace in town, Brent is the detective, investigating wrong doings and applying justice where necessary and Bart is the diplomat who smooths things over when any people have a dispute or disagreement. Brent is meticulous in his investigations and fair in the way he handles any situation he finds. Discretion is his byword. There's a rumour that Bart used to work for the United Nations but what ever his history there is no denying his ability to get apparently irreconcilable parties working together to their combined benefit. Someone who works closely with Bart is Brad, he is the translator in town. He has several languages that he can converse in but he can also explain things from someone's point of view or  and make it understandable to someone else. To keep things on the straight and narrow from a legal perspective is Ben the solicitor, making sure we all abide by the rules.Two people who make for an interesting evening's conversation if you get them together are Aaron and Grant, Aaron is the local planning inspector and Grant is an inventor of some reputation. Anything being constructed around here needs Aarons agreement. He's quite flexible in his rules though; if you can justify what you want to do with solid logic but he wont stand for any development going on without his inclusion. That gets a demolition notice and there's no argument. Grant as I mentioned is the inventor in town, if something can be improved or created then Grant is your man. He mainly works on his own but isnt averse to getting specific advice and assistance from specialist from out of town if they can help him finish his creations.There aren't too many people left for you to meet in the town, there's Rob, he's an ex professional sportsman. He played Hockey, Football, Cricket, you name it. He was in his element as goal keeper / wicket keeper and that shows in his personal life. He just goes about his business and people often don't even know that he's helped them. Really low profile, doesn't get any glory but saves people from lots of problems, even disasters on occasion. There goes Neil, he's a bit of an odd person, some people say he's gifted with special clairvoyant powers, personally I think he's got his ear to the ground and knows where to find out the important news as soon as its made public. Anyone getting a visit from Neil is best off to follow his advice though, he's usually spot on and you wont be caught by surprise if you follow his recommendations – wherever it comes from.Poor old Andrew is the last person to introduce you to. Andrew doesn't show himself too often but when he does it seems that people find a reason to blame him for their problems, whether he had anything to do with their predicament or not. In all honesty, without fail, and to his great credit, he takes it in good grace and never retaliates or gets annoyed when he's out and about.  It pays off too as its very often the case that those who were blaming him recently suddenly find they need his help and they readily forget the issues pretty rapidly.And then there's me, what do I do in town? Well, I'm just a DBA with a lot of hats. (Jackstown Pop. 1)

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  • How to set x509 Certificate private key access rights for AppPoolIdentity

    - by ChrisD
    If your website uses the AppPoolIdentity and requires access to the private key of an x509Certficate, you’ll need to grant the read permissions to the iis application pool.   To grant permissions to the AppPoolIdentity: Run Certificates.MMC (or Start->run->mmc.exe, Add Certificate Snap-In for LocalMachine) Select the certificate (Personal node on the certificate tree) , right click and Manage Permissions. Add a new user to the permissions list. Enter "IIS AppPool\AppPoolName" on the local machine". Replace "AppPoolName" with the name of your application pool.

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  • What constitutes a "substantial, good-faith effort to remove the links"

    - by Luke McCallum
    We engaged the services of a 3rd party SEO consultant to assist us in managing our Meta data and to write regular blogs on our site http://cyberdesignworks.com.au Without our authorisation, the SEO also ran a link building campaign which has seen us Penguin slapped and we no longer appear in Google for a number of our core keywords. Since notification by Google that we have "unnatural links" back in March we have undertaken a significant campaign to rid ourselves of these dodgy backlinks by a number of methods. I have just received feedback on my 4th or 5th resubmission which is still advising that we need to make a "substantial, good-faith effort to remove the links" before Google will reconsider us for inclusion. After the effort that I have gone through to get links removed, I am now at a loss as to what else I can do to demonstrate "substantial, good-faith effort to remove the links". Below is a summary of the actions that we have taken to date. According to http://removem.com we had about 5584 back-linking domains. Of those we have successfully contacted and had removed links from 344 domains We ignored links from 625 domains as they were either legitimate press releases, natural backlinks or client websites containing an attribution link in the footer that points back to us. Due to our efforts, or the sites simply becoming defunct, removem.com reports that links from 3262 domains have been removed. We have contacted but are yet to receive feedback from 1666 domains so we can assume that the backlinks remain. We have configured an automatic 301 redirect for each of the links from these 1666 domains to point to http://redirects.sanscode.com/ which we are calling our Bad Link Catcher (a stroke of genius I thought). i.e http://www.mysimplewebdesign.com/create-a-perfect-webpage-with-four-important-tips-from-sydney-web-development-service-companies.php As we are a web design agency, we have a large number of client websites which contain an attribution link in their footer which points back to us. We have gone through the vast majority of these and updated these links to replace anchor text with an image and rel="nofollow" link. i.e <a rel="nofollow" target="_blank" href="http://www.cyberdesignworks.com.au/"><img src="https://sessions.sanscode.com/site/assets/media/badges/Badge_CDW_SANSCODE.png"></a> See http://www.milkatwork.com.au/ An export from http://removem.com detailing the number of times we have contacted each link and whether it is still found or not was also supplied with each resubmission. The total back links reported in Google Web Master Tools has dropped from over 100K to 87K and I expect it to drop significantly lower once Google re-crawls each back-linking page. Based on all of the above, I am not sure what else I can do to to demonstrate a "substantial, good-faith effort to remove the links". I would sincerely appreciate any feedback or suggestions that you may have as I am out of ideas.

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  • Running Multiple Queries in Oracle SQL Developer

    - by thatjeffsmith
    There are two methods for running queries in SQL Developer: Run Statement Run Statement, Shift+Enter, F9, or this button Run Script No grids, just script (SQL*Plus like) ouput is fine, thank you very much! What’s the Difference? There are some obvious differences between the two features, the most obvious being the format of the output delivered. But there are some other, more subtle differences here, primarily around fetching. What is Fetch? After you run send your query to Oracle, it has to do 3 things: Parse Execute Fetch Technically it has to do at least 2 things, and sometimes only 1. But, to get the data back to the user, the fetch must occur. If you have a 10 row query or a 1,000,000 row query, this can mean 1 or many fetches in groups of records. Ok, before I went on the Fetch tangent, I said there were two ways to run statements in SQL Developer: Run Statement Run statement brings your query results to a grid with a single fetch. The user sees 50, 100, 500, etc rows come back, but SQL Developer and the database know that there are more rows waiting to be retrieved. The process on the server that was used to execute the query is still hanging around too. To alleviate this, increase your fetch size to 500. Every query ran will come back with the first 500 rows, and rows will be continued to be fetched in 500 row increments. You’ll then see most of your ad hoc queries complete with a single fetch. Scroll down, or hit Ctrl+End to force a full fetch and get all your rows back. Run Script Run Script runs the contents of the worksheet (or what’s highlighted) as a ‘script.’ What does that mean exactly? Think of this as being equivalent to running this in SQL*Plus: @my_script.sql; Each statement is executed. Also, ALL rows are fetched. So once it’s finished executing, there are no open cursors left around. The more obvious difference here is that the output comes back formatted as plain old text. Run one or more commands plus SQL*Plus commands like SET and SPOOL The Trick: Run Statement Works With Multiple Statements! It says ‘run statement,’ but if you select more than one with your mouse and hit the button – it will run each and throw the results to 1 grid for each statement. If you mouse hover over the Query Result panel tab, SQL Developer will tell you the query used to populate that grid. This will work regardless of what you have this preference set to: DATABASE – WORKSHEET – SHOW QUERY RESULTS IN NEW TABS Mind the fetch though! Close those cursors by bring back all the records or closing the grids when you’re done with them.

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  • Ubuntu server Mysql remote access from MySQL Workbench

    - by goodseller
    I have a newly install ubuntu installed the mysql server. After the basic config, I changed the my.cnf file and commented the bind_address I can start the server and added iptable for 3306. I also add the privileges to mysql server as follow: GRANT ALL PRIVILEGES ON . TO 'root'@'%' IDENTIFIED BY 'P@ssw0rd' WITH GRANT OPTION; FLUSH PRIVILEGES; exit However after connected from the mysql workbench, it shows no database. But it seems that have login. Anyone have faced that or can help me? Thx!

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  • HLSL - Creating Shadows in 2D

    - by richard
    The way that I create shadows is by the following technique: http://www.catalinzima.com/2010/07/my-technique-for-the-shader-based-dynamic-2d-shadows/ But I have questions to HLSL. The way that I currently do it is, I have a black and white image, where Black means 'object', and white means 'nothing'. I then distort the image like in the tutorial. I do this with a pixel shader, but instead of rendering to the screen, I render to a texture, back to my application. I then take this, and create the shadows, and then send it back to the graphics card to undo the distortion, after the shadow has been added - this comes back and I have a stencil of shadow. I can put this ontop of the original image and send them back to the graphics card, which then puts them on the screen. To me this is alot of back and forth. Is there a way i can avoid this? The problem that I am having is that I need to basically go through all positions in the texture 3 times, and use the new new texture every time instead of the orginal one. I tried to read up on Passes, but i don't think that i am heading in the right direction there. Help?

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  • java.net outage

    - by alexismp
    The GlassFish website has been down for a number of hours (together with a number of other projects) as a result of a general outage in the java.net datacenter. The team is working hard on getting everything back to normal. You can track progress by following @ProjectKenai. Update: services should now all be back to normal. If you face java.net issues in the future, consider reporting them here. And now, back to work!

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  • Cannot boot computer, help please :(

    - by Austin
    Ok so here is more descriptions, I REALLY NEED HELP! I installed Ubuntu on a disk (unsure of v. I can't check.. Computer is broke :/ ) I then burned the disk I restarted computer pressed f12 blah blah it came up, I pressed enter for English, I plugged an Ethernet card in for better connection, and then started the installation.... I did the basics, and I entered a host name, and a user name and pass all that, when it came to partition page, I presse enter for no and then it went back to the installation page, I pressed install again, and it brought me back, so I selected yes , it loaded an it asked what software to instal I selected sh ( it was first option and I didn't know which to do ) so after everything finished loading, my disk was ejected the process finish, I run my computer and it opens up in log in page on cmd script I didn't know it, so I ran disk again makin a user and pass to remember.... Going back to login thing I logged in, and all it did was say my username... I didn't know what to do from there, I looked online found nothing but grub stuff, so I went to "Advanced Ubuntu options" and then "(Recovery Mode) and went to update grub... In middle o loading it asked to continue (Y/n) I typed Y and it finished, it went back to the options located in (Recovery Mode) and I closed it, and it loaded... And then showed up in another script screen, saying a paragraph on top, and on left side ( where login: would be located etc. ) it says "Grub" and I don't know what to type, if I turn off computer and turn back on it just goes straight to that again... PLEASE HELP:(

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  • What is Linkvana?

    Linkvana is a wonderful search engine optimization service that makes it possible to have as many back links as you want. You can have these back links to multiple third party websites. You are completely free to choose your own anchor text for these back links. There is a network of articles and another one that comprises of blogs. You can create a custom anchor text in a very short time. Usually the process takes less than the time taken to write a hundred words long post on your blog or website. It is very easy and intuitive to create number of back links to several pages deep in your site navigation with the help of Linkvana.

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  • Is Java easy decompilation a factor worth considering

    - by Sandra G
    We are considering the programming language for a desktop application with extended GUI use (tables, windows) and heavy database use. We considered Java for use however the fact that it can be decompiled back very easily into source code is holding us back. There are of course many obfuscators available however they are just that: obfuscators. The only obfuscation worth doing we got was stripping function and variables names into meaningless letters and numbers so that at least stealing code and renaming it back into something meaningful is too much work and we are 100% sure it is not reversible back in any automated way. However as it concerns to protecting internals (like password hashes or sensible variables content) we found obfuscators really lacking. Is there any way to make Java applications as hard to decode as .exe counterparts? And is it a factor to consider when deciding whether to develop in Java a desktop application?

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  • At the Java DEMOgrounds - Oracle Java ME Embedded Enables the “Internet of Things”

    - by Janice J. Heiss
    I caught up with Oracle’s Robert Barnes, Senior Director, Java Product Management, who was demonstrating a new product from Oracle’s Java Platform, Micro Edition (Java ME) product portfolio, Oracle Java ME Embedded 3.2, a complete client Java runtime optimized for microcontrollers and other resource-constrained devices. Oracle’s Java ME Embedded 3.2 is a Java ME runtime based on CLDC 1.1 (JSR-139) and IMP-NG (JSR-228).“What we are showing here is the Java ME Embedded 3.2 that we announced last week,” explained Barnes. “It’s the start of the 'Internet of Things,’ in which you have very very small devices that are on the edge of the network where the sensors sit. You often have a middle area called a gateway or a concentrator which is fairly middle to higher performance. On the back end you have a very high performance server. What this is showing is Java spanning all the way from the server side right down towards the type of chip that you will get at the sensor side as the network.” Barnes explained that he had two different demos running.The first, called the Solar Panel System Demo, measures the brightness of the light.  “This,” said Barnes, “is a light source demo with a Cortex M3 controlling the motor, on the end of which is a sensor which is measuring the brightness of the lamp. This is recording the data of the brightness of the lamp and as we move the lamp out of the way, we should be able using the server to turn the sensor towards the lamp so the brightness reading will go higher. This sends the message back to the server and we can look at the web server sitting on the PC underneath the desk. We can actually see the data being passed back effectively through a back office type of function within a utility environment.” The second demo, the Smart Grid Response Demo, Barnes explained, “has the same board and processor and is still using Java ME embedded with a different app on top. This is a demand response demo. What we are seeing within the managing environment is that people want to track the pricing signals of the electricity. If it’s particularly expensive at any point in time, they may turn something off. This demo sets the price of the electricity as though this is coming from the back of the server sending pricing signals to my home.” The demo had a lamp and a fan and it was tracking the price of electricity. “If I set the price of the electricity to go over 5 cents, then the device will turn off,” explained Barnes. “I can go into my settings and, in this case, change the price to 50 cents and we can wait a minus and the lamp will go off. When I change the pricing signal so that it is lower, the lamp will come back on. The key point is that the Java software we have running is the same across all the different devices; it’s a way to build applications across multiple devices using the same software. This is important because it fixes peak loading on the network and can stops blackouts.” This demo brought me back to a prior decade when Sun Microsystems first promoted  Jini technology, a version of Java that would put everything on the network and give us the smart home. Your home would be automated to tell you when you were out of milk, when to change your light bulbs, etc. You would have access to the web and the network throughout your home.It’s interesting to see how technology moves over time – from the smart home to the Internet of Things.

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  • Xubuntu 14.04 black screen after monitor off/on

    - by Sampo Smolander
    I have a HP desktop machine with Ubuntu 14.04, with also Xubuntu and Gnome desktops installed. I mostly use the Xubuntu session. When using the Xubuntu session, when I power off my monitor, and power it back on, the screen stays black and I cannot do any work. With ctrl-alt-f6 I can open another virtual terminal, and then the screen works again, but if I to go back to the desktop session with ctrl-alt-f7, all I have is a black screen. But, if I login to Unity (the Ubuntu default session), or to Gnome, and turn the monitor off and back on, everything works ok. Also, if I log out, and while in the lightdm greeter, turn the monitor off and back on, everything works ok. What could be the cause for this, and how to fix this?

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  • Got an idea for an application, but part of it is patented, any suggestions?

    - by tekiegreg
    so I've been working on developing an idea for an application that I think has the potential to be successful, however after some initial research I've discovered that at least part of my ideas are covered by a patent out there, the patent in particular is held by a really large company (I don't want to give away specifics for fear I'd draw their attention for sure). I'm debating a few options: 1) Develop patents around my ideas that don't conflict and maybe approach the company in question for a license exchange 2) Just approach them for a license outright 3) Just develop around it anyways and hope for the best :-p What have other people done in these situations? Are companies generally willing to grant patent licenses? Are they willing to grant them at reasonable prices? Thoughts?

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  • Tips for XNA WP7 Developers

    - by Michael B. McLaughlin
    There are several things any XNA developer should know/consider when coming to the Windows Phone 7 platform. This post assumes you are familiar with the XNA Framework and with the changes between XNA 3.1 and XNA 4.0. It’s not exhaustive; it’s simply a list of things I’ve gathered over time. I may come back and add to it over time, and I’m happy to add anything anyone else has experienced or learned as well. Display · The screen is either 800x480 or 480x800. · But you aren’t required to use only those resolutions. · The hardware scaler on the phone will scale up from 240x240. · One dimension will be capped at 800 and the other at 480; which depends on your code, but you cannot have, e.g., an 800x600 back buffer – that will be created as 800x480. · The hardware scaler will not normally change aspect ratio, though, so no unintended stretching. · Any dimension (width, height, or both) below 240 will be adjusted to 240 (without any aspect ratio adjustment such that, e.g. 200x240 will be treated as 240x240). · Dimensions below 240 will be honored in terms of calculating whether to use portrait or landscape. · If dimensions are exactly equal or if height is greater than width then game will be in portrait. · If width is greater than height, the game will be in landscape. · Landscape games will automatically flip if the user turns the phone 180°; no code required. · Default landscape is top = left. In other words a user holding a phone who starts a landscape game will see the first image presented so that the “top” of the screen is along the right edge of his/her phone, such that the natural behavior would be to turn the phone 90° so that the top of the phone will be held in the user’s left hand and the bottom would be held in the user’s right hand. · The status bar (where the clock, battery power, etc., are found) is hidden when the Game-derived class sets GraphicsDeviceManager.IsFullScreen = true. It is shown when IsFullScreen = false. The default value is false (i.e. the status bar is shown). · You should have a good reason for hiding the status bar. Users find it helpful to know what time it is, how much charge their battery has left, and whether or not their phone is in service range. This is especially true for casual games that you expect someone to play for a few minutes at a time, e.g. while waiting for some event to start, for a phone call to come in, or for a train, bus, or subway to arrive. · In portrait mode, the status bar occupies 32 pixels of space. This means that a game with a back buffer of 480x800 will be scaled down to occupy approximately 461x768 screen pixels. Setting the back buffer to 480x768 (or some resolution with the same 0.625 aspect ratio) will avoid this scaling. · In landscape mode, the status bar occupies 72 pixels of space. This means that a game with a back buffer of 800x480 will be scaled down to occupy approximately 728x437 screen pixels. Setting the back buffer to 728x480 (or some resolution with the same 1.51666667 aspect ratio) will avoid this scaling. Input · Touch input is scaled with screen size. · So if your back buffer is 600x360, a tap in the bottom right corner will come in as (599,359). You don’t need to do anything special to get this automatic scaling of touch behavior. · If you do not use full area of the screen, any touch input outside the area you use will still register as a touch input. For example, if you set a portrait resolution of 240x240, it would be scaled up to occupy a 480x480 area, centered in the screen. If you touch anywhere above this area, you will get a touch input of (X,0) where X is a number from 0 to 239 (in accordance with your 240 pixel wide back buffer). Any touch below this area will give a touch input of (X,239). · If you keep the status bar visible, touches within its area will not be passed to your game. · In general, a screen measurement is the diagonal. So a 3.5” screen is 3.5” long from the bottom right corner to the top left corner. With an aspect ratio of 0.6 (480/800 = 0.6), this means that a phone with a 3.5” screen is only approximately 1.8” wide by 3” tall. So there are approximately 267 pixels in an inch on a 3.5” screen. · Again, this time in metric! 3.5 inches is approximately 8.89 cm. So an 8.89 cm screen is 8.89 cm long from the bottom right corner to the top left corner. With an aspect ratio of 0.6, this means that a phone with an 8.89 cm screen is only approximately 4.57 cm wide by 7.62 cm tall. So there are approximately 105 pixels in a centimeter on an 8.89 cm screen. · Think about the size of your finger tip. If you do not have large hands, think about the size of the fingertip of someone with large hands. Consider that when you are sizing your touch input. Especially consider that when you are spacing two touch targets near one another. You need to judge it for yourself, but items that are next to each other and are each 100x100 should be fine when it comes to selecting items individually. Smaller targets than that are ok provided that you leave space between them. · You want your users to have a pleasant experience. Making touch controls too small or too close to one another will make them nervous about whether they will touch the right target. Take this into account when you plan out your game initially. If possible, do some quick size mockups on an actual phone using colored rectangles that you position and size where you plan to have your game controls. Adjust as necessary. · People do not have transparent hands! Nor are their hands the size of a mouse pointer icon. Consider leaving a dedicated space for input rather than forcing the user to cover up to one-third of the screen with a finger just to play the game. · Another benefit of designing your controls to use a dedicated area is that you’re less likely to have players moving their finger(s) so frantically that they accidentally hit the back button, start button, or search button (many phones have one or more of these on the screen itself – it’s easy to hit one by accident and really annoying if you hit, e.g., the search button and then quickly tap back only to find out that the game didn’t save your progress such that you just wasted all the time you spent playing). · People do not like doing somersaults in order to move something forward with accelerometer-based controls. Test your accelerometer-based controls extensively and get a lot of feedback. Very well-known games from noted publishers have created really bad accelerometer controls and been virtually unplayable as a result. Also be wary of exceptions and other possible failures that the documentation warns about. · When done properly, the accelerometer can add a nice touch to your game (see, e.g. ilomilo where the accelerometer was used to move the background; it added a nice touch without frustrating the user; I also think CarniVale does direct accelerometer controls very well). However, if done poorly, it will make your game an abomination unto the Marketplace. Days, weeks, perhaps even months of development time that you will never get back. I won’t name names; you can search the marketplace for games with terrible reviews and you’ll find them. Graphics · The maximum frame rate is 30 frames per second. This was set as a compromise between battery life and quality. · At least one model of phone is known to have a screen refresh rate that is between 59 and 60 hertz. Because of this, using a fixed time step with a target frame rate of 30 will cause a slight internal delay to build up as the framework is forced to wait slightly for the next refresh. Eventually the delay will get to the point where a draw is skipped in order to recover from the delay. (See Nick's comment below for clarification.) · To deal with that delay, you can either stay with a fixed time step and set the frame rate slightly lower or else you can go to a variable time step and make sure to adjust all of your update data (e.g. player movement distance) to take into account the elapsed time from the last update. A variable time step makes your update logic slightly more complicated but will avoid frame skips entirely. · Currently there are no custom shaders. This might change in the future (there is no hardware limitation preventing it; it simply wasn’t a feature that could be implemented in the time available before launch). · There are five built-in shaders. You can create a lot of nice effects with the built-in shaders. · There is more power on the CPU than there is on the GPU so things you might typically off-load to the GPU will instead make sense to do on the CPU side. · This is a phone. It is not a PC. It is not an Xbox 360. The emulator runs on a PC and uses the full power of your PC. It is very good for testing your code for bugs and doing early prototyping and layout. You should not use it to measure performance. Use actual phone hardware instead. · There are many phone models, each of which has slightly different performance levels for I/O, screen blitting, CPU performance, etc. Do not take your game right to the performance limit on your phone since for some other phones you might be crossing their limits and leaving players with a bad experience. Leave a cushion to account for hardware differences. · Smaller screened phones will have slightly more dots per inch (dpi). Larger screened phones will have slightly less. Either way, the dpi will be much higher than the typical 96 found on most computer screens. Make sure that whoever is doing art for your game takes this into account. · Screens are only required to have 16 bit color (65,536 colors). This is common among smart phones. Using gradients on a 16 bit display can produce an ugly artifact known as banding. Banding is when, rather than a smooth transition from one color to another, you instead see distinct lines. Be careful to avoid this when possible. Banding can be avoided through careful art creation. Its effects can be minimized and even unnoticeable when the texture in question is always moving. You should be careful not to rely on “looks good on my phone” since some phones do have 32-bit displays and thus you’ll find yourself wondering why you’re getting bad reviews that complain about the graphics. Avoid gradients; if you can’t, make sure they are 16-bit safe. Audio · Never rely on sounds as your sole signal to the player that something is happening in the game. They might have the sound off. They might be playing somewhere loud. Etc. · You have to provide controls to disable sound & music. These should be separate. · On at least one model of phone, the volume control API currently has no effect. Players can adjust sound with their hardware volume buttons, but in game selectors simply won’t work. As such, it may not be worth the effort of providing anything beyond on/off switches for sound and music. · MediaPlayer.GameHasControl will return true when a game is hooked up to a PC running Zune. When Zune is running, any attempts to do anything (beyond check GameHasControl) with MediaPlayer will cause an exception to be thrown. If this exception is thrown, catch it and disable music. Exceptions take time to propagate; you don’t want one popping up in every single run of your game’s Update method. · Remember that players can already be listening to music or using the FM radio. In this case GameHasControl will be false and you should handle this appropriately. You can, alternately, ask the player for permission to stop their current music and play your music instead, but the (current) requirement that you restore their music when done is very hard (if not impossible) to deal with. · You can still play sound effects even when the game doesn’t have control of the music, but don’t think this is a backdoor to playing music. Your game will fail certification if your “sound effect” seems to be more like music in scope and length.

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  • How to make xlock use the first key I hit as a part of my password

    - by alesplin
    I just switched from Arch Linux to Ubuntu 10.10. I'm running the Fluxbox window manager, and I use xlockmore to lock my screen with the following key shortcut: 192 :Exec xlock-mode marquee +usefirst -icongeometry 240x240 -message "back in a minute..." The problem I'm having is that xlock is definitely not using my first key as part of my password. Instead, it uses some randomized fade pattern to fade to the password screen. I find this highly annoying, as when I get back to my desk and start entering my password it doesn't register password characters until the fade pattern is complete. I've also tried the following modifications with no difference: 192 :Exec xlock -mode marquee -usefirst -icongeometry 240x240 -message "back in a minute..." 192 :Exec xlock -mode marquee -icongeometry 240x240 -message "back in a minute..." The first example worked flawlessly on Arch. Does Ubuntu have some sort of system default that you can't override on the command-line?

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