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• SOA Community Newsletter May 2014

  - by JuergenKress

  Registration for the Fusion Middleware Summer Camps 2014 is open – Register asap for one of our bootcamps August 4th – 8th 2014 in Lisbon. Please read details and pre-requisitions careful before you register. We expect that like in the past, the conference will be booked out soon! If you can’t make it to Lisbon attend our SOA Suite 11c free on-demand Bootcamp or  Managing the Complexity of IoT online trainings. With more than 5000 customers, SOA Suite Achieves Significant Customer Adoption and Industry Recognition.Thanks to all our SOA Specialized partners for making our joins SOA customers successful! As a summary of the Industrial SOA series we published the Podcast Show Notes: SOA and Cloud - Where's This Relationship Going? Make sure you use the Oracle Demo Systems for your customer presentations. The demo systems are hosted by Oracle and include complete scenarios based on the latest Middleware version like the new B2B SOA Suite Demo System! For local presentations without fast internet use the SOA/BPM 11.1.1.7.1 Virtual Machine and Case Management Sample. At our SOA Community Workspace (SOA Community membership required) you can get new IoT presentations for Location Based Offers for Banking & Whitepaper and online Webcast & Utility presentation. In this newsletter you will find many articles about OSB: OSB 11g – A Hands-on Tutorial & Using Split-Joins in OSB Services for parallel processing of messages & OSB, Service Callouts and OQL & Working with Oracle Security Token Service. Thanks for sharing all the additional SOA articles within the community: How to configure Oracle SOA/BPM task auto release & Controlling BPEL process flow at runtime & Upgrading to Oracle SOA Suite 11g PS6 (11.1.1.7)? Do this. & BPEL and BPM's performance monitoring using DMS & SOA 11g - Create RESTful Service In Oracle SOA & Wrong timezone causes TopLink warning in SOA suite. Highlight of the BPM and ACM section is the IDC BPM vendor report. The new bundle Patch including the ACM UI is now available. If you want to learn more about ACM, get the ACM training material at our SOA Community Workspace (SOA Community membership required). A great demo for your next BPM presentation is the BPM iPad app. It’s simpleMobile BPM is Not An Option. It’s a Necessity. Thanks for sharing all the additional BPM articles within the community: BPM update adds Case Management Web Interface and REST APIs & Implementing deadline functionality with Oracle Adaptive Case Management & BPM 11g Timeout Heuristics & Humantask Assignment: Names and Expressions Assignment via Rules. In our last section Architecture, it is all about design. Usability is a key factor for customer satisfaction, worth to spend some time and read the Simplified User Experience Design Patterns eBook. Great blueprint for your project! See you in Lisbon! To read the newsletter please visit www.tinyurl.com/soaNewsMay2014 (OPN Account required) To become a member of the SOA Partner Community please register at http://www.oracle.com/goto/emea/soa (OPN account required) If you need support with your account please contact the Oracle Partner Business Center. Blog Twitter LinkedIn Facebook Wiki Mix Forum Technorati Tags: newsletter,SOA Community newsletter,SOA Community,Oracle,OPN,Jürgen Kress

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• HPCM 11.1.2.2.x - HPCM Standard Costing Generating >99 Calc Scipts

  - by Jane Story

  HPCM Standard Profitability calculation scripts are named based on a documented naming convention. From 11.1.2.2.x, the script name = a script suffix (1 letter) + POV identifier (3 digits) + Stage Order Number (1 digit) + “_” + index (2 digits) (please see documentation for more information (http://docs.oracle.com/cd/E17236_01/epm.1112/hpm_admin/apes01.html). This naming convention results in the name being 8 characters in length i.e. the maximum number of characters permitted calculation script names in non-unicode Essbase BSO databases. The index in the name will indicate the number of scripts per stage. In the vast majority of cases, the number of scripts generated per stage will be significantly less than 100 and therefore, there will be no issue. However, in some cases, the number of scripts generated can exceed 99. It is unusual for an application to generate more than 99 calculation scripts for one stage. This may indicate that explicit assignments are being extensively used. An assessment should be made of the design to see if assignment rules can be used instead. Assignment rules will reduce the need for so many calculation script lines which will reduce the requirement for such a large number of calculation scripts. In cases where the scripts generates exceeds 100, the length of the name of the 100th calculation script is different from the 99th as the calculation script name changes from being 8 characters long and becomes 9 characters long (e.g. A6811_100 rather than A6811_99). A name of 9 characters is not permitted in non Unicode applications. It is “too long”. When this occurs, an error will show in the hpcm.log as “Error processing calculation scripts” and “Unexpected error in business logic “. Further down the log, it is possible to see that this is “Caused by: Error copying object “ and “Caused by: com.essbase.api.base.EssException: Cannot put olap file object ... object name_[<calc script name> e.g. A6811_100] too long for non-unicode mode application”. The error file will give the name of the calculation script which is causing the issue. In my example, this is A6811_100 and you can see this is 9 characters in length. It is not possible to increase the number of characters allowed in a calculation script name. However, it is possible to increase the size of each calculation script. The default for an HPCM application, set in the preferences, is set to 4mb. If the size of each calculation script is larger, the number of scripts generated will reduce and, therefore, less than 100 scripts will be generated which means that the name of the calculation script will remain 8 characters long. To increase the size of the generated calculation scripts for an application, in the HPM_APPLICATION_PREFERENCE table for the application, find the row where HPM_PREFERENCE_NAME_ID=20. The default value in this row is 4194304. This can be increased e.g. 7340032 will increase this to 7mb. Please restart the profitability service after making the change.

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• ArchBeat Link-o-Rama for October 14-20, 2012

  - by Bob Rhubart

  The Top 10 items shared on the OTN ArchBeat Facebook page for the week of October 14-21, 2012. Panel: On the Impact of Software | InfoQ Les Hatton (Oakwood Computing Associates), Clive King (Oracle), Paul Good (Shell), Mike Andrews (Microsoft) and Michiel van Genuchten (moderator) discuss the impact of software engineering on our lives in this panel discussion recorded at the Computer Society Software Experts Summit 2012. ResCare Solves Content Lifecycle Challenges with Oracle WebCenter Learn how ResCare solves content lifecycle challenges with Oracle WebCenter. Speakers: Joe Lichtefeld, VP of Application Services & PMO, ResCare Wayne Boerger, Product Manager, TEAM Informatics Doug Thompson, EVP Global Development, TEAM Informatics Date: Tuesday, October 30, 2012 Time: 10:00 a.m. PT / 1:00 p.m. ET WebLogic Server 11gR1 Interactive Quick Reference "The WebLogic Server 11gR1 Administration interactive quick reference," explains Juergen Kress, "is a multimedia tool for various terms and concepts used in WebLogic Server architecture. This tool is available for administrators for online or offline use. This is built as a multimedia web page which provides descriptions of WebLogic Server Architectural components, and references to relevant documentation. This tool offers valuable reference information for any complex concept or product in an intuitive and useful manner." Oracle ACE Directors Nordic Tour 2012 : Venues and BI Presentations | Mark Rittman Oracle ACE Director Mark Rittman shares information on the Oracle ACE Director Tour, as the community leaders make their way through the land of the midnight sun, with events in Copenhagen, Stockholm, Oslo and Helsinki. Mobile Apps for EBS | Capgemini Oracle Blog Capgemini solution architect Satish Iyer breifly describes how Oracle ADF and Oracle SOA Suite can be used to fill the gap in mobile applications for Oracle EBS. Introducing the New Face of Fusion Applications | Misha Vaughan Oracle ACE Directors Debra Lilly and Floyd Teter have already blogged about the the new face of Oracle Fusion Applications. Now Applications User Experience Architect Misha Vaughan shares a brief overview of how the Oracle Applications User Experience (UX) team developed the new look. BPM 11g - Dynamic Task Assignment with Multi-level Organization Units | Mark Foster "I've seen several requirements to have a more granular level of task assignment in BPM 11g based on some value in the data passed to the process," says Fusion Middleware A-Team architect Mark Foster. "Parametric Roles is normally the first port of call to try to satisfy this requirement, but in this blog we will show how a lot of use-cases can be satisfied by the easier to implement and flexible Organization Unit." OTN Architect Day Los Angeles - Oct 25 Oracle Technology Network Architect Day in Los Angeles happens in one week. Register now to make sure you don't miss out on a rich schedule of expert technical sessions and peer interaction covering the use of Oracle technologies in cloud computing, SOA, and more. Even better: it's all free. When: October 25, 2012, 8:30am - 5:00pm. Where: Sofitel Los Angeles, 8555 Beverly Boulevard, Los Angeles, CA 90048. Oracle VM VirtualBox 4.2.2 released | Oracle's Virtualization Blog The Fat Bloke weighs in with a short post with information on where you can find information and the download for the latest VirtualBox release. Advanced Oracle SOA Suite #OOW 2012 SOA Presentations The Oracle SOA Product Management team has compiled a complete list of all twelve of their Oracle SOA Suite presentations from Oracle OpenWorld 2012, with links to the slide decks. Thought for the Day "Software: do you write it like a book, grow it like a plant, accrete it like a pearl, or construct it like a building?" — Jeff Atwood Source: softwarequotes.com

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• Types of semantic bugs, logic errors [closed]

  - by C-Otto

  I am a PhD student and currently focus on automatically finding instances of new types of bugs in (Java) programs that cannot be found by existing tools like FindBugs. The existing tool currently is used to prove/disprove termination of (Java) programs. I have some ideas (see below), but I could need more input from you (experienced programmers, potential users of my tool). What kind of bugs do you wish to find? What types of bugs exist and might be suitable for my analysis? One strength of the approach I use is detailled information about the heap. So in contrast to FindBugs, I can work with knowledge of the form "variable x and variable y are disjoint on the heap" or "variable z is not cyclic". It is also possible to see if a method might have side effects (and if so, which variables may/may not be affected by it). Example 1: Vacuous call: Graph graphOne = createGraph(); Graph graphTwo = createGraph(); Node source = graphTwo.getRootNode(); for (Node n : graphOne.getNodes()) { if (areConnected(source, n)) { graphTwo.addNode(n); } } Imagine createGraph() creates a fresh graph, so that graphOne and graphTwo are disjoint on the heap. Then, because source is taken from graphTwo instead of graphOne, the call to areConnected always returns false. In this situation I could find out that the call areConnected is useless (because it does not have any side effect and the return value always is false) which helps finding the real bug (taking source from the wrong graph). For this the information that x and y are disjoint (because graphOne and graphTwo are disjoint) is crucial. This bug is related to calling x.equals(y) where x and y are objects of different classes. In this scenario, most implementations of equals() always return false, which most likely is not the intended result. FindBugs already finds this bug (hardcoded to equals(), semantics of implementation is not checked). Example 2: Useless code: someCode(); while (something()) { yetMoreSomething(); } moreCode(); In the case that the loop (so the code in something() and yetMoreSomething()) does not modify anything visible outside the loop, it does not make sense to run this code - the program has the same behaviour as someCode(); moreCode() (i.e., without the loop). To find this out, one needs detailled information about the side effects of the (possibly useless) code. If I can prove that the code does not have any side effect that can be observed afterwards (in the example: in moreCode() or later), then the code indeed is useless. Of course, here Input/Output of any form must be seen as a side effect, so that a System.out.println(...) is not considered useless. Example 3: Ignored return value: Instead of x = foo(); and making use of x, the method is called without storing the result: foo();. If the method does not have any side effect, its invocation is useless and can be dropped. Most likely, the bug here is that the returned value should have been used. Here, too, detailled information about side effects are needed. Can you think of similar types of bugs that might be detected (only) with detailled information about the heap, side effects, semantics of called methods, ...? Did you encounter bugs related to the ones shown below in "real life"? By the way, the tool is AProVE and Java related publications can be found on my homepage. Thanks a lot, Carsten

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• Friday Tips #3

  - by Chris Kawalek

  Even though yesterday was Thanksgiving here in the US, we still have a Friday tip for those of you around your computers today. In fact, we have two! The first one came in last week via our #AskOracleVirtualization Twitter hashtag. The tweet has disappeared into the ether now, but we remember the gist, so here it is: Question: Will there be an Oracle Virtual Desktop Client for Android? Answer by our desktop virtualization product development team: We are looking at Android as a supported platform for future releases. Question: How can I make a Sun Ray Client automatically connect to a virtual machine? Answer by Rick Butland, Principal Sales Consultant, Oracle Desktop Virtualization: Someone recently asked how they can assign VM’s to specific Sun Ray Desktop Units (“DTU’s”) without any user interfaction being required, without the “Desktop Selector” being displayed, or any User Directory.  That is, they wanted each Sun Ray to power on and immediately connect to a pre-assigned Solaris VM.   This can be achieved by using “tokens” for user assignment – that is, the tokens found on Smart Cards, DTU’s, or OVDC clients can be used in place of user credentials.  Note, however, that mixing “token-only” assignments and “User Directories” in the same VDI Center won’t work.   Much of this procedure is covered in the documentation, particularly here. But it can useful to have everything in one place, “cookbook-style”:  1. Create the “token-only” directory type: From the VDI administration interface, select:  “Settings”, “Company”, “New”, select the “None” radio button, and click “Next.” Enter a name for the new “Company”, and click “Next”, then “Finish.” 2. Create Desktop Providers, Pools, and VM’s as appropriate. 3. Access the Sun Ray administration interface at http://servername:1660 and login using “root” credentials, and access the token-id’s you wish to use for assignment.  If you’re using DTU tokens rather than Smart Card tokens, these can be found under the “Tokens” tab, and “Search-ing” using the “Currently Used Tokens” tab.  DTU’s can be identified by the prefix “psuedo.”   For example: 4. Copy/paste this token into the VDI administrative interface, by selecting “Users”, “New”, and pasting in the token ID, and click “OK” - for example: 5. Assign the token (DTU) to a desktop, that is, in the VDI Admin Gui, select “Pool”, “Desktop”, select the VM, and click "Assign" and select the token you want, for example: In addition to assigning tokens to desktops, you'll need to bypass the login screen.  To do this, you need to do two things:  1.  Disable VDI client authentication with:  /opt/SUNWvda/sbin/vda settings-setprops -p clientauthentication=Disabled 2. Disable the VDI login screen – to do this,  add a kiosk argument of "-n" to the Sun Ray kiosk arguments screen.   You set this on the Sun Ray administration page - "Advanced", "Kiosk Mode", "Edit", and add the “-n” option to the arguments screen, for example: 3.  Restart both the Sun Ray and VDI services: # /opt/SUNWut/sbin/utstart –c # /opt/SUNWvda/sbin/vda-service restart Remember, if you have a question for us, please post on Twitter with our hashtag (again, it's #AskOracleVirtualization), and we'll try to answer it if we can. See you next time!

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• Multidimensional multiple-choice knapsack problem: find a feasible solution

  - by Onheiron

  My assignment is to use local search heuristics to solve the Multidimensional multiple-choice knapsack problem, but to do so I first need to find a feasible solution to start with. Here is an example problem with what I tried so far. Problem R1 R2 R3 RESOUCES : 8 8 8 GROUPS: G1: 11.0 3 2 2 12.0 1 1 3 G2: 20.0 1 1 3 5.0 2 3 2 G3: 10.0 2 2 3 30.0 1 1 3 Sorting strategies To find a starting feasible solution for my local search I decided to ignore maximization of gains and just try to fit the resources requirements. I decided to sort the choices (strategies) in each group by comparing their "distance" from the multidimensional space origin, thus calculating SQRT(R1^2 + R2^2 + ... + RN^2). I felt like this was a keen solution as it somehow privileged those choices with resouce usages closer to each other (e.g. R1:2 R2:2 R3:2 < R1:1 R2:2 R3:3) even if the total sum is the same. Doing so and selecting the best choice from each group proved sufficent to find a feasible solution for many[30] different benchmark problems, but of course I knew it was just luck. So I came up with the problem presented above which sorts like this: R1 R2 R3 RESOUCES : 8 8 8 GROUPS: G1: 12.0 1 1 3 < select this 11.0 3 2 2 G2: 20.0 1 1 3 < select this 5.0 2 3 2 G3: 30.0 1 1 3 < select this 10.0 2 2 3 And it is not feasible because the resources consmption is R1:3, R2:3, R3:9. The easy solution is to pick one of the second best choices in group 1 or 2, so I'll need some kind of iteration (local search[?]) to find the starting feasible solution for my local search solution. Here are the options I came up with Option 1: iterate choices I tried to find a way to iterate all the choices with a specific order, something like G1 G2 G3 1 1 1 2 1 1 1 2 1 1 1 2 2 2 1 ... believeng that feasible solutions won't be that far away from the unfeasible one I start with and thus the number of iterations will keep quite low. Does this make any sense? If yes, how can I iterate the choices (grouped combinations) of each group keeping "as near as possibile" to the previous iteration? Option 2: Change the comparation term I tried to think how to find a better variable to sort the choices on. I thought at a measure of how "precious" a resource is based on supply and demand, so that an higer demand of a more precious resource will push you down the list, but this didn't help at all. Also I thought there probably isn't gonna be such a comparsion variable which assures me a feasible solution at first strike. I there such a variable? If not, is there a better sorting criteria anyways? Option 3: implement any known sub-optimal fast solving algorithm Unfortunately I could not find any of such algorithms online. Any suggestion?

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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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• Manual (Dynamic) LINQ subquery using IN clause

  - by immortalali-msn-com

  Hi Everyone, I want to query the DB through LINQ writing manual SQL, my linq method is: var q = db.TableView.Where(sqlAfterWhere); returnValue = q.Count(); this method queries well if the value passed to variable "sqlAfterWhere" is: (this variable is String type) it.Name = 'xyz' but what if i want to use IN clause, using a sub query. (i need to use 'it' before every column name in the above query to work), i cant use 'it' before the sub query columns as its a separate query, so what should i do, if i dont use any thing, and use column names directly it gives error saying " could not be resolved" where is my column names with out 'it' at the begining. So the query not working is: (this is a string passed to the variable above): it.Name IN (SELECT Name FROM TableName WHERE Address LIKE '%SomeAddress%') the errors come out as: Name could not be resolved Address could not be resolved The exact error is: "'Name' could not be resolved in the current scope or context. Make sure that all referenced variables are in scope, that required schemas are loaded, and that namespaces are referenced correctly., near simple identifier, line 6, column 25." Same error for "Address as well if i use 'it.' before these columns it gives error as: "The element type 'Edm.Int32' and the CollectionType 'Transient.collection[Transient.rowtype(GroupID,Edm.Int32(Nullable=True,DefaultValue=))]' are not compatible. The IN expression only supports entity, primitive, and reference types. , near WHERE predicate, line 6, column 14." Thanks for the help

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• Getting fields_for and accepts_nested_attributes_for to work with a belongs_to relationship

  - by Billy Gray

  I cannot seem to get a nested form to generate in a rails view for a belongs_to relationship using the new accepts_nested_attributes_for facility of Rails 2.3. I did check out many of the resources available and it looks like my code should be working, but fields_for explodes on me, and I suspect that it has something to do with how I have the nested models configured. The error I hit is a common one that can have many causes: '@account[owner]' is not allowed as an instance variable name Here are the two models involved: class Account < ActiveRecord::Base # Relationships belongs_to :owner, :class_name => 'User', :foreign_key => 'owner_id' accepts_nested_attributes_for :owner has_many :users end class User < ActiveRecord::Base belongs_to :account end Perhaps this is where I am doing it 'rong', as an Account can have an 'owner', and may 'users', but a user only has one 'account', based on the user model account_id key. This is the view code in new.html.haml that blows up on me: - form_for :account, :url => account_path do |account| = account.text_field :name - account.fields_for :owner do |owner| = owner.text_field :name And this is the controller code for the new action: class AccountsController < ApplicationController # GET /account/new def new @account = Account.new end end When I try to load /account/new I get the following exception: NameError in Accounts#new Showing app/views/accounts/new.html.haml where line #63 raised: @account[owner] is not allowed as an instance variable name If I try to use the mysterious 'build' method, it just bombs out in the controller, perhaps because build is just for multi-record relationships: class AccountsController < ApplicationController # GET /account/new def new @account = Account.new @account.owner.build end end You have a nil object when you didn't expect it! The error occurred while evaluating nil.build If I try to set this up using @account.owner_attributes = {} in the controller, or @account.owner = User.new, I'm back to the original error, "@account[owner] is not allowed as an instance variable name". Does anybody else have the new accepts_nested_attributes_for method working with a belongs_to relationship? Is there something special or different you have to do? All the official examples and sample code (like the great stuff over at Ryans Scraps) is concerned with multi-record associations.

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• ANTLR AST rules fail with RewriteEmptyStreamException

  - by Barry Brown

  I have a simple grammar: grammar sample; options { output = AST; } assignment : IDENT ':=' expr ';' ; expr : factor ('*' factor)* ; factor : primary ('+' primary)* ; primary : NUM | '(' expr ')' ; IDENT : ('a'..'z')+ ; NUM : ('0'..'9')+ ; WS : (' '|'\n'|'\t'|'\r')+ {$channel=HIDDEN;} ; Now I want to add some rewrite rules to generate an AST. From what I've read online and in the Language Patterns book, I should be able to modify the grammar like this: assignment : IDENT ':=' expr ';' -> ^(':=' IDENT expr) ; expr : factor ('*' factor)* -> ^('*' factor+) ; factor : primary ('+' primary)* -> ^('+' primary+) ; primary : NUM | '(' expr ')' -> ^(expr) ; But it does not work. Although it compiles fine, when I run the parser I get a RewriteEmptyStreamException error. Here's where things get weird. If I define the pseudo tokens ADD and MULT and use them instead of the tree node literals, it works without error. tokens { ADD; MULT; } expr : factor ('*' factor)* -> ^(MULT factor+) ; factor : primary ('+' primary)* -> ^(ADD primary+) ; Alternatively, if I use the node suffix notation, it also appears to work fine: expr : factor ('*'^ factor)* ; factor : primary ('+'^ primary)* ; Is this discrepancy in behavior a bug?

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• Design approach, string table data, variables, stl memory usage

  - by howieh

  I have an old structure class like this: typedef vector<vector<string>> VARTYPE_T; which works as a single variable. This variable can hold from one value over a list to data like a table. Most values are long,double, string or double [3] for coordinates (x,y,z). I just convert them as needed. The variables are managed in a map like this : map<string,VARTYPE_T *> where the string holds the variable name. Sure, they are wrapped in classes. Also i have a tree of nodes, where each node can hold one of these variablemaps. Using VS 2008 SP1 for this, i detect a lot of memory fragmentation. Checking against the stlport, stlport seemed to be faster (20% ) and uses lesser memory (30%, for my test cases). So the question is: What is the best implementation to solve this requirement with fast an properly used memory ? Should i write an own allocator like a pool allocator. How would you do this ? Thanks in advance, Howie

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• Traversing/Manipulating new window from parent window with jquery

  - by Anthony

  I found a question already with a possible solution, but I had already tried the method suggested before reading it, and it even says it's inconsistent. So I guess I'm wondering why this doesn't work: $("img").click(function() { var imgwindow = window.open('imgwin.html','','width=460,height=345'); alert(imgwindow.find("img").attr("src")); }); The goal is to set the new window's img to the same src as the image that the user clicked to open the new window. But in the above scenario, I'm just trying to tap into the new window to get what it's already-set src. I have imgwin.html already written with a default src for the image, so it should alert that url. Instead I just get undefined. I also tried the following (which should be identical on the back end), but with the same results: $("img").click(function() { var imgwindow = window.open('imgwin.html','','width=460,height=345'); alert($("img",imgwindow).attr("src")); }); I even tried variations of wrapping the imgwindow variable in $() in case somehow jquery wasn't picking up on the variable as a DOM element. The only thing I can guess is that since window.open() is a method, jquery doesn't treat it like a DOM element, even though all documentation from basic javascript tutorials treat the variable as both a method to open the window and the pointer to the window's inner DOM.

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• onPause/onResume activity issues

  - by Josh

  I have a small test application I am working on which has a timer that updates a textview to countdown from 100 to 0. That works fine, but now I am trying to pause the application if the user presses the back button on the phone and then restart the timer from where they left off when they reopen the app. Here is the code I am using: @Override public void onPause() { if(this._timer_time_remaining > 0) { this.timer.cancel(); } super.onPause(); Log.v("Pausing", String.format("Pausing with %d", this._timer_time_remaining)); } @Override public void onResume() { super.onResume(); Log.v("Resuming", String.format("Resuming with %d", this._timer_time_remaining)); if(this._timer_time_remaining > 0) { setContentView(R.layout.in_game); start_timer(this._timer_time_remaining); } } The start_timer() method creates a CountDownTimer which updates the textview in the onTick method and updates the this._timer_time_remaining int variable. CountDownTimer and _timer_time_remaining are both declared at the class level like this: private CountDownTimer timer; private int _timer_time_remaining; From the Log.v() prints I see that the _timer_time_remaining variable has the correct number of seconds stored when onPause is called, but it is set back to 0 when onResume starts. Why does the variable get reset? I thought that the application would continue to run in the background with the same values. Am I missing something? This is all declared in a class that extends Activity. Thanks in advance!

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• vbCrLf in Multiline TextBox shows up only when .Trim() is called

  - by Brandon Montgomery

  I have an ASP TextBox with TextMode set to MultiLine. I'm having problems with preserving the vbCrLf characters when a user tries to put line breaks into the text. When a button on the page is pressed, I'm taking the text from the control, trimming it using String.Trim, and assigning that value to a String property on an object (which, in turn assigns it to a private internal String variable on the object). The object then takes the value from the private internal variable and throws it into the database using a stored procedure call (the SP parameter it is put into is an nvarchar(4000)). ASPX Page: <asp:UpdatePanel ID="UpdatePanel2" runat="server" RenderMode="Inline" UpdateMode="Conditional" ChildrenAsTriggers="true"> <ContentTemplate> <!-- some other controls and things --> <asp:TextBox TextMode="MultiLine" runat="server" ID="txtComments" Width="100%" Height="60px" CssClass="TDTextArea" Style="border: 0px;" MaxLength="2000" /> <!-- some other controls and things --> </ContentTemplate> </asp:UpdatePanel> code behind: ProjectRequest.StatusComments = txtComments.Text.Trim object property: Protected mStatusComments As String = String.Empty Property StatusComments() As String Get Return mStatusComments.Trim End Get Set(ByVal Value As String) mStatusComments = Value End Set End Property stored proc call: Common.RunSP(mDBConnStr, "ProjectStatusUpdate", _ Common.MP("@UID", SqlDbType.NVarChar, 40, mUID), _ Common.MP("@ProjID", SqlDbType.VarChar, 40, mID), _ Common.MP("@StatusID", SqlDbType.Int, 8, mStatusID), _ Common.MP("@Comments", SqlDbType.NVarChar, 4000, mStatusComments), _ Common.MP("@PCTComp", SqlDbType.Int, 4, 0), _ Common.MP("@Type", Common.TDSqlDbType.TinyInt, 1, EntryType)) Here's the strangest part. When I debug the code, if I type "test test" (without the quotes) into the comments text box, then click the save button and use the immediate window to view the variable values as I step through, here is what I get: ?txtComments.Text "test test" ?txtComments.Text.Trim "test test" ?txtComments.Text(4) " "c ?txtComments.Text.Trim()(4) " "c Anyone have a clue as to what's going on here?

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• Advice moving from Eclipse to xCode

  - by Gloin the Dark

  To xCode xPerts: I have been doing Java in Eclipse for about 9 years now and I have really gotten used to the power of the refactoring tools. There are a few operations I do all the time. I am looking for equivalents in xCode since it has better support for objective-c than eclipse. (I'm not at my Mac as I write this. So some of this is from memory. I am still very new to xCode.) 1 "rename". It seems that the xCode equivalent for variables is "edit all in scope". Does this work for files/classes/methods too? 2 "extract local variable" select an expression it creates a local var initialized to that expression. It even creates a usable name for the variable. 3 "extract method" select some code and it will create a method with that code and appropriate parameters/return value. 4 "inline" (variable or method) opposite of extract, inlines all or just the selected occurrence of the selected var or method. 5 "find next" occurrence of selected text. In eclipse I can select some text and hit ctrl-k to go to the next occurrence of that in the file. likewise shift-ctrl-k finds backwards. IIRC the xCode "find next" ignores the selection and only uses what is in the find box. 6 "change method signature" This would be very useful with ocjective-c's named parameter messaging syntax. This is great for adding parameters to a method. 7 "pull-up/push-down" for moving methods up or down the class hierarchy. 8 "move" for moving elements around to other classes etc. Those are the ones that I use all of the time. I have estimated that these tools cut my coding time in half. Are any of these supported in xCode? Thanks in advance for any advice.

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• jQuery autocomplete: taking JSON input and setting multiple fields from single field

  - by Sly

  I am trying to get the jQuery autocomplete plugin to take a local JSON variable as input. Once the user has selected one option from the autocomplete list, I want the adjacent address fields to be autopopulated. Here's the JSON variable that declared as a global variable in the of the HTML file: var JSON_address={"1":{"origin":{"nametag":"Home","street":"Easy St","city":"Emerald City","state":"CA","zip":"9xxxx"},"destination":{"nametag":"Work","street":"Factory St","city":"San Francisco","state":"CA","zip":"94104"}},"2":{"origin":{"nametag":"Work","street":"Umpa Loompa St","city":"San Francisco","state":"CA","zip":"94104"},"destination":{"nametag":"Home","street":"Easy St","city":"Emerald City ","state":"CA","zip":"9xxxx"}}}</script> I want the first field to display a list of "origin" nametags: "Home", "Work". Then when "Home" is selected, adjacent fields are automatically populated with Street: Easy St, City: Emerald City, etc. Here's the code I have for the autocomplete: $(document).ready(function(){ $("#origin_nametag_id").autocomplete(JSON_address, { autoFill:true, minChars:0, dataType: 'json', parse: function(data) { var rows = new Array(); for (var i=0; i<=data.length; i++) { rows[rows.length] = { data:data[i], value:data[i].origin.nametag, result:data[i].origin.nametag }; } return rows; } }).change(function(){ $("#street_address_id").autocomplete({ dataType: 'json', parse: function(data) { var rows = new Array(); for (var i=0; i<=data.length; i++) { rows[rows.length] = { data:data[i], value:data[i].origin.street, result:data[i].origin.street }; } return rows; } }); }); }); So this question really has two subparts: 1) How do you get autocomplete to process the multi-dimensional JSON object? (When the field is clicked and text entered, nothing happens - no list) 2) How do you get the other fields (street, city, etc) to populate based upon the origin nametag sub-array? Thanks in advance!

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• emacs: Can I set compilation-error-regexp-alist in a mode hook fn?

  - by Cheeso

  I am trying to set the compilation-error-regexp-alist in a function that I add as a mode hook. (defun cheeso-javascript-mode-fn () (turn-on-font-lock) ...bunch of other stuff ;; for JSLINT (make-local-variable 'compilation-error-regexp-alist) (setq compilation-error-regexp-alist '( ("^[ \t]*\\([A-Za-z.0-9_: \\-]+\\)(\\([0-9]+\\)[,]\\( *[0-9]+\\))\\( Microsoft JScript runtime error\\| JSLINT\\): \\(.+\\)$" 1 2 3) )) ;;(make-local-variable 'compile-command) (setq compile-command (let ((file (file-name-nondirectory buffer-file-name))) (concat "%windir%\\system32\\cscript.exe \\cheeso\\bin\\jslint.js " file))) ) (add-hook 'javascript-mode-hook 'cheeso-javascript-mode-fn) The mode hook runs. The various things I Set in the mode hook work. The compile-command gets set. But for some reason, the compilation-error-regexp-alist value doesn't take effect. If I later do a M-x describe-variable on compilation-error-regexp-alist, it shows me the value I think it should have. But .. the errors in the compilation buffer don't get highlighted, and M-x next-error does not work. If I add the error regexp value to the compilation-error-regexp-alist via setq-default, like this: (setq-default compilation-error-regexp-alist '( ... jslint regexp here ... ... many other regexp's here... )) ...then it works. The errors in the compilation buffer get properly highlighted and M-x next-error functions as expected.

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• Altering URLs and mapping - path_prefix? - Ruby on Rails...

  - by bgadoci

  Ok, so I am working on a blog application of sorts. Thus far, it allows for a user to sign up for their own account, create posts, tags, comments, etc. I have just implemented the ability to use www.myapp.com/brandon to set @user to find by username and therefore correctly display the users information at each url. So when you go to www.myapp.com/brandon you see all Brandon's posts, tags, and comments associated with those posts, etc. Works great. I implementing this URL mapping through the routes.rb file by adding the following: map.username_link '/:username', :controller => 'posts', :action => 'index' And then just setting the @user variable in the PostController and corresponding views to find_by_username. Now the issue is this. Once at www.myapp.com/brandon when you click on a post title, it sends to myapp.com/posts/id without the username in the URL which blows up my view because nothing is being set for the @user variable. How do I tell Rails to create the link reading www.myapp.com/brandon/posts/id vs www.myapp.com/posts/id and then map that action? I am assuming this will involve some code in the view, and then adding another line in the routes.rb file, map.subdomain_link '/:username/posts/:id', :controller => 'posts', :action => 'show' and adding the @user variable to the PostController#show action, but not totally sure if this is even the right approach. UPDATE: I have been reading about :path_prefix and seems like it might be what I am looking for. I have tried to implement simply by adding map.resources :posts, :path_prefix => '/:user_username/:post_id' to the routes.rb file but not working (even after server restart). I am sure this is not correct but wanted to let you know what I have tried.

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• What's with the love of dynamic Languages

  - by Kibbee

  It seems that everybody is jumping on the dynamic, non-compiled bandwagon lately. I've mostly only worked in compiled, static typed languages (C, Java, .Net). The experience I have with dynamic languages is stuff like ASP (Vb Script), JavaScript, and PHP. Using these technologies has left a bad taste in my mouth when thinking about dynamic languages. Things that usually would have been caught by the compiler such as misspelled variable names and assigning an value of the wrong type to a variable don't occur until runtime. And even then, you may not notice an error, as it just creates a new variable, and assigns some default value. I've also never seen intellisense work well in a dynamic language, since, well, variables don't have any explicit type. What I want to know is, what people find so appealing about dynamic languages? What are the main advantages in terms of things that dynamic languages allow you to do that can't be done, or are difficult to do in compiled languages. It seems to me that we decided a long time ago, that things like uncompiled asp pages throwing runtime exceptions was a bad idea. Why is there is a resurgence of this type of code? And why does it seem to me at least, that Ruby on Rails doesn't really look like anything you couldn't have done with ASP 10 years ago?

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• function's return address is different from its supposed value, buffer overflow,

  - by ultrajohn

  Good day everyone! I’m trying to understand how buffer overflow works. I’m doing this for my project in a computer security course I’m taking. Right now, I’m in the process of determining the address of the function’s return address which I’m supposed to change to perform a buffer overflow attack. I’ve written a simple program based from an example I’ve read in the internet. What this program does is it creates an integer pointer that will be made to point to the address of the function return address in the stack. To do this, (granted I understand how a function/program variables get organized in the stack), I add 8 to the buffer variable’ address and set it as the value of ret. I’m not doing anything here that would change the address contained in the location of func’s return address. here's the program: Output of the program when gets excecuted: As you can see, I’m printing the address of the variables buffer and ret. I’ve added an additional statement printing the value of the ret variable (supposed location of func return address, so this should print the address of the next instruction which will get executed after func returns from execution). Here is the dump which shows the supposed address of the instruction to be executed after func returns. (Underlined in green) As you can see, that value is way different from the value printed contained in the variable ret. My question is, why are they different? (of course in the assumption that what I’ve done are all right). Else, what have I done wrong? Is my understanding of the program’s runtime stack wrong? Please, help me understand this. My project is due nextweek and I’ve barely touched it yet. I’m sorry if I’m being demanding, I badly need your help.

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• Django model operating on a queryset

  - by jmoz

  I'm new to Django and somewhat to Python as well. I'm trying to find the idiomatic way to loop over a queryset and set a variable on each model. Basically my model depends on a value from an api, and a model method must multiply one of it's attribs by this api value to get an up-to-date correct value. At the moment I am doing it in the view and it works, but I'm not sure it's the correct way to achieve what I want. I have to replicate this looping elsewhere. Is there a way I can encapsulate the looping logic into a queryset method so it can be used in multiple places? I have this atm (I am using django-rest-framework): class FooViewSet(viewsets.ModelViewSet): model = Foo serializer_class = FooSerializer bar = # some call to an api def get_queryset(self): # Dynamically set the bar variable on each instance! foos = Foo.objects.filter(baz__pk=1).order_by('date') for item in foos: item.needs_bar = self.bar return items I would think something like so would be better: def get_queryset(self): bar = # some call to an api # Dynamically set the bar variable on each instance! return Foo.objects.filter(baz__pk=1).order_by('date').set_bar(bar) I'm thinking the api hit should be in the controller and then injected to instances of the model, but I'm not sure how you do this. I've been looking around querysets and managers but still can't figure it out nor decided if it's the best method to achieve what I want. Can anyone suggest the correct way to model this with django? Thanks.

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• Flash (AS3) can't read response ...

  - by Quandary

  Question: I call an asp.net handler (ashx) like this from Flash, and onLoadSuccessful, I get the ashx response back. The problem now is whatever I do in onLoadSuccessful to get the responseStatus variable never gets me the variable (just an error message: property responseStatus for string not found), but the output of: trace("Response: " + evt.target.data); is Response: &responseStatus=ASP.NET+Fehler%3a+Die+Datei+%22C%3a%5cinetpub%5cwwwroot%5cRaumplaner_New%5cRaumplaner_New%5cabcdef.xml%22+konnte+nicht+gefunden+werden.& It used to work in ActionScript2... Any hints as to what I do wrong ? I mean the request gets sent, and the reponse received, but no matter how I try to do it, I can't access the responseStatus variable... var scriptRequest:URLRequest = new URLRequest(strURL); var scriptLoader:URLLoader = new URLLoader(); var scriptVars:URLVariables = new URLVariables(); scriptLoader.addEventListener(Event.COMPLETE, onLoadSuccessful); scriptLoader.addEventListener(IOErrorEvent.IO_ERROR, onLoadError); scriptLoader.addEventListener(SecurityErrorEvent.SECURITY_ERROR, onSecurityError); scriptVars.ScaleString = nScale; scriptVars.ModifyFile = "abcdef.xml"; scriptRequest.method = URLRequestMethod.POST; scriptRequest.data = scriptVars; scriptLoader.load(scriptRequest); function onLoadSuccessful(evt:Event):void { trace("Success."); //ExternalInterface.call("alert", "Die neue Skalierung wurde erfolgreich gespeichert."); //getURL("javascript:alert(\""+"Die neue Skalierung wurde erfolgreich gespeichert.\\nALLE Instanzen des Browsers schliessen und neu starten, damit die Änderung in Kraft tritt."+"\");"); trace("Response: " + evt.target.data); trace("ResponseStatus: " + evt.target.data.responseStatus); var loader:URLLoader = URLLoader(evt.target); trace("responseStatus: " + loader.data.responseStatus); }

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• perl issuing os command with defined variables

  - by Vinnie Biros

  I am adding functionality into my scripts so that they can use kerberos authentication to run automatically and use secure protocols when executing. I have my functionality working for shell scripts that do exactly what i want, however i am having issues porting it to perl to work within my perl scripts as i am new to perl. Here is my working shell code and trying to get the same functionality in perl: #!/bin/sh ticketFileName=`basename $0-$$` #set filename variable to name of script plus the PID krb5CacheLocation=/tmp/$ticketFileName #set ticket cache location to /tmp + script name /usr/share/centrifydc/kerberos/bin/kinit -c $krb5CacheLocation -kt /root/.ssh/someaccount.keytab someaccount #get TGT and specifiy ticket cache location on kinit export KRB5CCNAME=$krb5CacheLocation #set the KRB5CCNAME variable to tell ssh where to look What i have attempted in perl: #!/usr/bin/perl my $ticketFileName = `basename $0-$$`; my $krb5CacheLocation = '/tmp/'.$ticketFileName; `export KRB5CCNAME=$krb5CacheLocation`; `/usr/share/centrifydc/kerberos/bin/kinit -c $krb5CacheLocation -kt /root/.ssh/unixmap0000.keytab unixmap0000`; Seems it is not liking the passed variable that i am referencing in the OS command. Anyone have any ideas or suggestions?

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• Write a compiler for a language that looks ahead and multiple files?

  - by acidzombie24

  In my language I can use a class variable in my method when the definition appears below the method. It can also call methods below my method and etc. There are no 'headers'. Take this C# example. class A { public void callMethods() { print(); B b; b.notYetSeen(); public void print() { Console.Write("v = {0}", v); } int v=9; } class B { public void notYetSeen() { Console.Write("notYetSeen()\n"); } } How should I compile that? what i was thinking is: pass1: convert everything to an AST pass2: go through all classes and build a list of define classes/variable/etc pass3: go through code and check if there's any errors such as undefined variable, wrong use etc and create my output But it seems like for this to work I have to do pass 1 and 2 for ALL files before doing pass3. Also it feels like a lot of work to do until I find a syntax error (other than the obvious that can be done at parse time such as forgetting to close a brace or writing 0xLETTERS instead of a hex value). My gut says there is some other way. Note: I am using bison/flex to generate my compiler.

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• How you would you describe the Observer pattern in beginner language?

  - by Sheldon

  Currently, my level of understanding is below all the coding examples on the web about the Observer Pattern. I understand it simply as being almost a subscription that updates all other events when a change is made that the delegate registers. However, I'm very unstable in my true comprehension of the benefits and uses. I've done some googling, but most are above my level of understanding. I'm trying to implement this pattern with my current homework assignment, and to truly make sense on my project need a better understanding of the pattern itself and perhaps an example to see what its use. I don't want to force this pattern into something just to submit, I need to understand the purpose and develop my methods accordingly so that it actually serves a good purpose. My text doesn't really go into it, just mentions it in one sentence. MSDN was hard for me to understand, as I'm a beginner on this, and it seems more of an advanced topic. How would you describe this Observer pattern and its uses in C# to a beginner? For an example, please keep code very simple so I can understand the purpose more than complex code snippets. I'm trying to use it effectively with some simple textbox string manipulations and using delegates for my assignment, so a pointer would help!

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