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  • iPad Simulator Multitouch Cursors Don't Show Up When Window is Scaled 100%

    - by Joel
    I have the iPhone SDK 3.2 installed and been working on an iPad application. However, the iPad simulator doesn't show the two gray multitouch "cursors" when I hold down the ALT/OPTION button and move the mouse around. This only happens when the simulator scale size is set to 100%. If I have it set to 50% they show up. When I have it set to be an iPhone, they show up. It's only iPad 100% size. The multitouch still works fine, I just can't see where I'm "touching". I've trying closing the simulator completely, changing from the iPhone and back again. Resizing. All sorts of stuff. Has anyone else seen this problem? Anyone have any suggestions for fixing this? I've googled and searched SOF for anyone else having this problem, but I kinda wonder if it's just me. If it makes a difference I have a Mac Mini 1.83 GHz Intel Core 2 Duo with Snow Leopard 10.6.3 installed. Thanks.

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  • How to use Win32 SetCursor() with WPF resource and HwndHost

    - by Hank
    We have an HwndHost UIElement in our WPF application which is used to display Direct3d graphics, and the only way I have found to set a cursor for the HwndHost UIElment is to call the Win32 API SetCursor(). All of our cursors are resources in managed assemblies, and I would prefer to not change that, but I have not been able to find a way to load one of these cursors via any Win32 APIs like LoadImage(). Does anybody know how to get a handle(hCursor) to a cursor which is a resource in a managed assembly? Or, is there another way to set a cursor on an HwndHost displaying Direct3D graphics?

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  • Lua SQL: peeking at cursors

    - by NP
    I am using LuaSQL, and query for a result set using con:execute(sql_stmt), which returns a cursor. How do I see if there is at least one row in that resultset, without doing a cursor:fetch to pop that first row?

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  • AppEngine: how do cursors work?

    - by victor a.k.a. python for ever
    hello, i have the following code def get(self): date = datetime.date.today() loc_query = Location.all() last_cursor = memcache.get('location_cursor') if last_cursor: loc_query.with_cursor(last_cursor) loc_result = loc_query.fetch(1) for loc in loc_result: self.record(loc, date) taskqueue.add( url='/task/query/simplegeo', params={'date':date, 'locid':loc.key().id()} ) if len(loc_result): memcache.add('location_cursor', loc_query.cursor()) taskqueue.add(url='/task/count/', method='GET') else: memcache.add('location_cursor', None) i don't know what i'm doing wrong, but i am getting the same cursor which is not the effect i wanted. why isn't the cursor moving?

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  • Best way to use PL/SQL Pacakge Cursors from Pro*C

    - by Greg Reynolds
    I have a cursor defined in PL/SQL, and I am wondering what the best way to use it from Pro*C is. Normally for a cursor defined in Pro*C you would do: EXEC SQL DECLARE curs CURSOR FOR SELECT 1 FROM DUAL; EXEC SQL OPEN curs; EXEC SQL FETCH curs INTO :foo; EXEC SQL CLOSE cusr; I was hoping that the same (or similar) syntax would work for a packaged cursor. For example, I have a package MyPack, with a declaration type MyType is record (X integer); cursor MyCurs(x in integer) return MyType; Now I have in my Pro*C code a rather unsatisfying piece of embedded PL/SQL that opens the cursor, does the fetching etc., as I couldn't get the first style of syntax to work. Using the example EXEC SQL EXECUTE DECLARE XTable is table of MyPack.MyType; BEGIN OPEN MyPack.MyCurs(:param); FETCH MyPack.MyCurs INTO XTable; CLOSE MyPack.MyCurs; END; END-EXEC; Does anyone know if there is a more "Pure" Pro*C approach?

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  • Sending one record from cursor to another function Postgres

    - by PylonsN00b
    FYI: I am completely new to using cursors... So I have one function that is a cursor: CREATE FUNCTION get_all_product_promos(refcursor, cursor_object_id integer) RETURNS refcursor AS ' BEGIN OPEN $1 FOR SELECT * FROM promos prom1 JOIN promo_objects ON (prom1.promo_id = promo_objects.promotion_id) WHERE prom1.active = true AND now() BETWEEN prom1.start_date AND prom1.end_date AND promo_objects.object_id = cursor_object_id UNION SELECT prom2.promo_id FROM promos prom2 JOIN promo_buy_objects ON (prom2.promo_id = promo_buy_objects.promo_id) LEFT JOIN promo_get_objects ON prom2.promo_id = promo_get_objects.promo_id WHERE (prom2.buy_quantity IS NOT NULL OR prom2.buy_quantity > 0) AND prom2.active = true AND now() BETWEEN prom2.start_date AND prom2.end_date AND promo_buy_objects.object_id = cursor_object_id; RETURN $1; END; ' LANGUAGE plpgsql; SO then in another function I call it and need to process it: ... --Get the promotions from the cursor SELECT get_all_product_promos('promo_cursor', this_object_id) updated := FALSE; IF FOUND THEN --Then loop through your results LOOP FETCH promo_cursor into this_promotion --Preform comparison logic -this is necessary as this logic is used in other contexts from other functions SELECT * INTO best_promo_results FROM get_best_product_promos(this_promotion, this_object_id, get_free_promotion, get_free_promotion_value, current_promotion_value, current_promotion); ... SO the idea here is to select from the cursor, loop using fetch (next is assumed correct?) and put the record fetched into this_promotion. Then send the record in this_promotion to another function. I can't figure out what to declare the type of this_promotion in get_best_product_promos. Here is what I have: CREATE OR REPLACE FUNCTION get_best_product_promos(this_promotion record, this_object_id integer, get_free_promotion integer, get_free_promotion_value numeric(10,2), current_promotion_value numeric(10,2), current_promotion integer) RETURNS... It tells me: ERROR: plpgsql functions cannot take type record OK first I tried: CREATE OR REPLACE FUNCTION get_best_product_promos(this_promotion get_all_product_promos, this_object_id integer, get_free_promotion integer, get_free_promotion_value numeric(10,2), current_promotion_value numeric(10,2), current_promotion integer) RETURNS... Because I saw some syntax in the Postgres docs showed a function being created w/ a input parameter that had a type 'tablename' this works, but it has to be a tablename not a function :( I know I am so close, I was told to use cursors to pass records around. So I studied up. Please help.

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  • MySQL Cursor Issue

    - by James Inman
    I've got the following code - this is the first time I've really attempted using cursors. DELIMITER $$ DROP PROCEDURE IF EXISTS demo$$ DROP TABLE IF EXISTS temp$$ CREATE TEMPORARY TABLE temp( id INTEGER NOT NULL AUTO_INCREMENT, start DATETIME NOT NULL, end DATETIME NOT NULL, PRIMARY KEY(id) ) $$ CREATE PROCEDURE demo() BEGIN DECLARE done INT DEFAULT 0; DECLARE a, b DATETIME; DECLARE cur1 CURSOR FOR SELECT MAX(end) AS end FROM ( SELECT id, start, end, @r := @r + (start > @edate) AS num, @edate := GREATEST(@edate, end) FROM ( SELECT @r := 0, @edate := '0001-01-01' ) vars, student_lectures WHERE ( student_id = 1 AND start >= '2010-04-26 00:00:00' AND end <= '2010-04-30 23:59:59' ) ORDER BY start ) q GROUP BY num; DECLARE cur2 CURSOR FOR SELECT MIN(start) AS start FROM ( SELECT id, start, end, @r := @r + (start > @edate) AS num, @edate := GREATEST(@edate, end) FROM ( SELECT @r := 0, @edate := '0001-01-01' ) vars, student_lectures WHERE ( student_id = 1 AND start >= '2010-04-26 00:00:00' AND end <= '2010-04-30 23:59:59' ) ORDER BY start ) q GROUP BY num LIMIT 1, 18446744073709551615; DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1; OPEN cur1; OPEN cur2; REPEAT FETCH cur1 INTO a; FETCH cur2 INTO b; IF NOT done THEN INSERT INTO temp(start, end) VALUES(a,b); END IF; UNTIL done END REPEAT; CLOSE cur1; CLOSE cur2; END $$ SELECT * FROM temp; I'm not getting anything outputted into the temp table. Running the following query gives me output, so I know there's rows it should be matching - but I imagine I've made some obvious mistake. SELECT MAX(end) AS end FROM ( SELECT id, start, end, @r := @r + (start > @edate) AS num, @edate := GREATEST(@edate, end) FROM ( SELECT @r := 0, @edate := '0001-01-01' ) vars, student_lectures WHERE ( student_id = 1 AND start >= '2010-04-26 00:00:00' AND end <= '2010-04-30 23:59:59' ) ORDER BY start ) q GROUP BY num; The output this query returns: +---------------------+ | end | +---------------------+ | 2010-04-26 13:00:00 | | 2010-04-26 18:15:00 | | 2010-04-27 11:00:00 | | 2010-04-27 13:00:00 | | 2010-04-27 18:15:00 | | 2010-04-28 13:00:00 | | 2010-04-29 13:00:00 | | 2010-04-29 18:15:00 | | 2010-04-30 13:00:00 | | 2010-04-30 15:15:00 | | 2010-04-30 17:15:00 | +---------------------+ 11 rows in set (0.02 sec)

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  • mysql dynamic cursor

    - by machaa
    Here is the procedure I wrote- Cursors c1 & c2. c2 is inside c1, I tried declaring c2 below c1 (outside the c1 cursor) but then I is NOT taking the updated value :( Any suggestions to make it working would be helpful, Thanks create table t1(i int); create table t2(i int, j int); insert into t1(i) values(1), (2), (3), (4), (5); insert into t2(i, j) values(1, 6), (2, 7), (3, 8), (4, 9), (5, 10); delimiter $ CREATE PROCEDURE p1() BEGIN DECLARE I INT; DECLARE J INT; DECLARE done INT DEFAULT 0; DECLARE c1 CURSOR FOR SELECT i FROM t1; DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1; OPEN c1; REPEAT FETCH c1 INTO I; IF NOT done THEN select I; DECLARE c2 CURSOR FOR SELECT j FROM t2 WHERE i = I; OPEN c2; REPEAT FETCH c2 into J; IF NOT done THEN SELECT J; END IF; UNTIL done END REPEAT; CLOSE c2; set done = 0; END IF; UNTIL done END REPEAT; CLOSE c1; END$ delimiter ;

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  • Help replace this SQL cursor with better code

    - by user318573
    Can anyone give me a hand improving the performance of this cursor logic from SQL 2000. It runs great in SQl2005 and SQL2008, but takes at least 20 minutes to run in SQL 2000. BTW, I would never choose to use a cursor, and I didn't write this code, just trying to get it to run faster. Upgrading this client to 2005/2008 is not an option in the immediate future. ------------------------------------------------------------------------------- ------- Rollup totals in the chart of accounts hierarchy ------------------------------------------------------------------------------- DECLARE @B_SubTotalAccountID int, @B_Debits money, @B_Credits money, @B_YTDDebits money, @B_YTDCredits money DECLARE Bal CURSOR FAST_FORWARD FOR SELECT SubTotalAccountID, Debits, Credits, YTDDebits, YTDCredits FROM xxx WHERE AccountType = 0 AND SubTotalAccountID Is Not Null and (abs(credits)+abs(debits)+abs(ytdcredits)+abs(ytddebits)<>0) OPEN Bal FETCH NEXT FROM Bal INTO @B_SubTotalAccountID, @B_Debits, @B_Credits, @B_YTDDebits, @B_YTDCredits --For Each Active Account WHILE @@FETCH_STATUS = 0 BEGIN --Loop Until end of subtotal chain is reached WHILE @B_SubTotalAccountID Is Not Null BEGIN UPDATE xxx2 SET Debits = Debits + @B_Debits, Credits = Credits + @B_Credits, YTDDebits = YTDDebits + @B_YTDDebits, YTDCredits = YTDCredits + @B_YTDCredits WHERE GLAccountID = @B_SubTotalAccountID SET @B_SubTotalAccountID = (SELECT SubTotalAccountID FROM xxx2 WHERE GLAccountID = @B_SubTotalAccountID) END FETCH NEXT FROM Bal INTO @B_SubTotalAccountID, @B_Debits, @B_Credits, @B_YTDDebits, @B_YTDCredits END CLOSE Bal DEALLOCATE Bal

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  • SQL question - Cursor or not?

    - by grady
    Hi, I have a query which returns 2+ rows. In those results is a column which we can call columnX for now. Lets look at those example results: columnX 100 86 85 70 null null I get 6 rows for example, some of them are null, some of them are not null. Now I want to go through those results and stop as soon as I find a row which is < null. How can I do that? Thanks in advance :-)

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  • Silverlight: Is it possible to use custom mouse cursors/pointers?

    - by Mark Redman
    I have just found this page indicating the support for Silverlight mouse cursors: http://msdn.microsoft.com/en-us/library/system.windows.input.cursor(VS.95).aspx Is that it!!! :-| what are they thinking, at least there is stylish looking Eraser! Is there aany other way to use custom cursors? How efficient/usable would it be to hide the cursor and show a png instead?

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  • In Sublime Text 2, how can I indent out to a straight column with multiple cursors on a ragged edge?

    - by mtoast
    Suppose I've got multiple cursors along several lines, like this: foo| barr| foobar| baz| How can I automatically push the whitespace at the end of each line out to a flat edge, like this?: foo | barr | foobar | baz | (In these examples, | is supposed to be my cursor.) EDIT #1 When you just Tab or Space from the initial arrangement, you get this: # Useful, but not what I'm looking for foo | barr | foobar | baz | That's useful, but not what I'm looking for. I'm looking for some kind of keyboard shortcut that will let me indent from a ragged multi-cursor insert out to a straight column.

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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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  • Bandwidth Problem in Terminal?

    - by Rob Barker
    I'm trying to install the Mac cursors to Ubuntu 12.04 but i get this error when using the wget command in Terminal. ubuntu@ubuntu:~$ wget -O mac-cursors.zip http://dl.dropbox.com/u/53319850/NoobsLab.com/mac-cursors.zip --2012-12-09 16:31:17-- http://dl.dropbox.com/u/53319850/NoobsLab.com/mac-cursors.zip Resolving dl.dropbox.com (dl.dropbox.com)... 23.21.195.136, 23.23.139.153, 107.20.134.231, ... Connecting to dl.dropbox.com (dl.dropbox.com)|23.21.195.136|:80... connected. HTTP request sent, awaiting response... 509 Bandwidth Error 2012-12-09 16:31:18 ERROR 509: Bandwidth Error. Can someone tell me what this means please, and a possible workaround? Thanks very much.

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  • Mouse pointer size inconsistent

    - by charon00
    Since installing Ubuntu 12.04, I've been having a problem with the mouse pointer size. On the desktop, it is quite a bit larger than it should be (24), though the different cursors (editing text, hyperlink hand, etc) are correct. The size changes to the correct size when the pointer is over some application windows (GVim, Netbeans, Firefox), but then changes back once it is moved out of the window. There was a similar question here, but the Xdefaults solution did not work for me, and I didn't want to try the one requiring editing the icon image. In addition, I've tried changing the cursor theme using sudo update-alternatives --config x-cursor-theme as well as using the dconf-editor, but though I can change the theme, the size issue remains. In case it's relevant, I'm running on a dual-screen setup with monitor sizes of 2560x1600 and 1920x1080, using the NVidia video driver. Is there another way to control pointer size, or a setting that might be messing it up? EDIT: These are the values/options I have for update-alternatives and in dconf-editor. I'm now wondering if Netbeans and Firefox are making the mouse pointer smaller than it should be, but I'm not sure how big 24 should be... update-alternatives: Selection Path Priority Status ------------------------------------------------------------ 0 /usr/share/icons/DMZ-White/cursor.theme 90 auto mode 1 /etc/X11/cursors/core.theme 30 manual mode 2 /etc/X11/cursors/handhelds.theme 20 manual mode 3 /etc/X11/cursors/redglass.theme 20 manual mode 4 /etc/X11/cursors/whiteglass.theme 20 manual mode * 5 /usr/share/icons/DMZ-Black/cursor.theme 30 manual mode 6 /usr/share/icons/DMZ-White/cursor.theme 90 manual mode dconf-editor: I can't post the image since I'm a new user but the cursor-size is set to 24 and the cursor-theme is DMZ-Black.

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  • Android: Sorting a merged cursor

    - by tonyc
    Hi, I'm wondering if there's any way to merge two cursors together and then resort them. I can easily merge two cursors together by using a MergedCursor, but that doesn't sort them. I have two sets of contacts in two separate cursors (with totally different schemas) and I want to merge them and sort them by name (the name column is different in the two cursors). Is this possible? Thanks, Tony

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  • Connection Pooling is Busted

    - by MightyZot
    A few weeks ago we started getting complaints about performance in an application that has performed very well for many years.  The application is a n-tier application that uses ADODB with the SQLOLEDB provider to talk to a SQL Server database.  Our object model is written in such a way that each public method validates security before performing requested actions, so there is a significant number of queries executed to get information about file cabinets, retrieve images, create workflows, etc.  (PaperWise is a document management and workflow system.)  A common factor for these customers is that they have remote offices connected via MPLS networks. Naturally, the first thing we looked at was the query performance in SQL Profiler.  All of the queries were executing within expected timeframes, most of them were so fast that the duration in SQL Profiler was zero.  After getting nowhere with SQL Profiler, the situation was escalated to me.  I decided to take a peek with Process Monitor.  Procmon revealed some “gaps” in the TCP/IP traffic.  There were notable delays between send and receive pairs.  The send and receive pairs themselves were quite snappy, but quite often there was a notable delay between a receive and the next send.  You might expect some delay because, presumably, the application is doing some thinking in-between the pairs.  But, comparing the procmon data at the remote locations with the procmon data for workstations on the local network showed that the remote workstations were significantly delayed.  Procmon also showed a high number of disconnects. Wireshark traces showed that connections to the database were taking between 75ms and 150ms.  Not only that, but connections to a file share containing images were taking 2 seconds!  So, I asked about a trust.  Sure enough there was a trust between two domains and the file share was on the second domain.  Joining a remote workstation to the domain hosting the share containing images alleviated the time delay in accessing the file share.  Removing the trust had no affect on the connections to the database. Microsoft Network Monitor includes filters that parse TDS packets.  TDS is the protocol that SQL Server uses to communicate.  There is a certificate exchange and some SSL that occurs during authentication.  All of this was evident in the network traffic.  After staring at the network traffic for a while, and examining packets, I decided to call it a night.  On the way home that night, something about the traffic kept nagging at me.  Then it dawned on me…at the beginning of the dance of packets between the client and the server all was well.  Connection pooling was working and I could see multiple queries getting executed on the same connection and ethereal port.  After a particular query, connecting to two different servers, I noticed that ADODB and SQLOLEDB started making repeated connections to the database on different ethereal ports.  SQL Server would execute a single query and respond on a port, then open a new port and execute the next query.  Connection pooling appeared to be broken. The next morning I wrote a test to confirm my hypothesis.  Turns out that the sequence causing the connection nastiness goes something like this: Make a connection to the database. Open a result set that returns enough records to require multiple roundtrips to the server. For each result, query for some other data in the database (this will open a new implicit connection.) Close the inner result set and repeat for every item in the original result set. Close the original connection. Provided that the first result set returns enough data to require multiple roundtrips to the server, ADODB and SQLOLEDB will start making new connections to the database for each query executed in the loop.  Originally, I thought this might be due to Microsoft’s denial of service (ddos) attack protection.  After turning those features off to no avail, I eventually thought to switch my queries to client-side cursors instead of server-side cursors.  Server-side cursors are the default, by the way.  Voila!  After switching to client-side cursors, the disconnects were gone and the above sequence yielded two connections as expected. While the real problem is the amount of time it takes to make connections over these MPLS networks (100ms on average), switching to client-side cursors made the problem go away.  Believe it or not, this is actually documented by Microsoft, and rather difficult to find.  (At least it was while we were trying to troubleshoot the problem!)  So, if you’re noticing performance issues on slower networks, or networks with slower switching, take a look at the traffic in a tool like Microsoft Network Monitor.  If you notice a high number of disconnects, and you’re using fire-hose or server-side cursors, then try switching to client-side cursors and you may see the problem go away. Most likely, Microsoft believes this to be appropriate behavior, because ADODB can’t guarantee that all of the data has been retrieved when you execute the inner queries.  I’m not convinced, though, because the problem remains even after replacing all of the implicit connections with explicit connections and closing those connections in-between each of the inner queries.  In that case, there doesn’t seem to be a reason why ADODB can’t use a single connection from the connection pool to make the additional queries, bringing the total number of connections to two.  Instead ADO appears to make an assumption about the state of the connection. I’ve reported the behavior to Microsoft and am awaiting to hear from the appropriate team, so that I can demonstrate the problem.  Maybe they can explain to us why this is appropriate behavior.  :)

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  • PostgreSQL pgdb driver raises "can't rollback" exception

    - by David Parunakian
    Hello, for some reason I'm experiencing the Operational Error with "can't rollback" message when I attempt to roll back my transaction in the following context: try: cursors[instance].execute("lock revision, app, timeout IN SHARE MODE") cursors[instance].execute("insert into app (type, active, active_revision, contents, z) values ('session', true, %s, %s, 0) returning id", (cRevision, sessionId)) sAppId = cursors[instance].fetchone()[0] cursors[instance].execute("insert into revision (app_id, type) values (%s, 'active')", (sAppId,)) cursors[instance].execute("insert into timeout (app_id, last_seen) values (%s, now())", (sAppId,)) connections[instance].commit() except pgdb.DatabaseError, e: connections[instance].rollback() return "{status: 'error', errno:4, errmsg: \"%s\"}"%(str(e).replace('\"', '\\"').replace('\n', '\\n').replace('\r', '\\r')) The driver in use is PGDB. What is fundamentally wrong here?

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  • values not equal in sqlite and json array in android

    - by Venkat
    I am trying to compare the value in sqlite table and id of the webservice what i have done so far is if(data_exist!=bookProduct.length()){ Log.i("in update","m here"); Cursor cursors = getRawEvents("select id from bcuk_book"); try{ for (int i = 0; i < bookProduct.length(); i++) { JSONObject c = bookProduct.getJSONObject(i); String Bid = c.getString(TAG_ID); ArrayList<String> mapId = new ArrayList<String>(); while(cursors.moveToNext()) { Log.e("cursors",cursors.getString(0)); Log.i(Bid,Bid); if(cursors.getString(0)!=c.getString(TAG_ID)){ Log.e("fas",Bid); } } mapId.add(TAG_ID); Log.e(Bid,Bid); } } My issue is i am getting same values in logs.. if(cursors.getString(0)!=c.getString(TAG_ID)){ this condition says if they are not equal then print the log..But the issue is i am entering into that block even i am getting same values from sqlite and TAG_ID i.e from json webservice..How to solve this.Where i done wrong?

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  • How do I change the cursor and its size?

    - by Thomas Le Feuvre
    I have recently created an Ubuntu 12.04 partition on my Windows 7 laptop. When installing it, I switched to "high contrast" mode, which has rather large cursors (by large I mean about twice as large and thick as they should normally are). Now I have successfully installed the partition, the large cursors have stuck around even after exiting this high contrast mode, but only when I am hovering over stuff e.g. hovering over text inputs, links, and when resizing windows. All of these cursors are too large. They cursor is only normally sized when the computer should be displaying the normal mouse pointer. Does anyone know how I might go about fixing this?

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  • Lost connection to MySQL server during query

    - by Otavio
    I have a huge table and I need to process all rows in it. I'm always getting this Lost connection message and I'm not able to reconnect and restore the cursor to the last position it was. This is basically the code I have here: # import MySQLdb class DB: conn = None def connect(self): self.conn = MySQLdb.connect('hostname', 'user', '*****', 'some_table', cursorclass=MySQLdb.cursors.SSCursor) def query(self, sql): try: cursor = self.conn.cursor() cursor.execute(sql) except (AttributeError, MySQLdb.OperationalError): self.connect() cursor = self.conn.cursor() cursor.execute(sql) return cursor # # db = DB() sql = "SELECT bla FROM foo" data = db.query(sql) for row in data: do_something(row) # But I'm always getting this: # Traceback (most recent call last): File "teste.py", line 124, in <module> run() File "teste.py", line 109, in run for row in data: File "/usr/lib64/python2.5/site-packages/MySQLdb/cursors.py", line 417, in next row = self.fetchone() File "/usr/lib64/python2.5/site-packages/MySQLdb/cursors.py", line 388, in fetchone r = self._fetch_row(1) File "/usr/lib64/python2.5/site-packages/MySQLdb/cursors.py", line 285, in _fetch_row return self._result.fetch_row(size, self._fetch_type) _mysql_exceptions.OperationalError: (2013, 'Lost connection to MySQL server during query') Exception _mysql_exceptions.OperationalError: (2013, 'Lost connection to MySQL server during query') in <bound method SSCursor.__del__ of <MySQLdb.cursors.SSCursor object at 0x7f7e3c8da410>> ignored # Do you have any idea?

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  • WPF Show wait cursor before application fully loads

    - by e28Makaveli
    I want to show the wait cursor before my WPF application, composed using CAL, fully loads. In the constructor of the main window, I have the following code: public MainWindow([Dependency] IUnityContainer container) { InitializeComponent(); Cursor = System.Windows.Input.Cursors.Wait; Mouse.OverrideCursor = System.Windows.Input.Cursors.Wait; ForceCursor = true; //this.Cursor = System.Windows.Input.Cursors.AppStarting; // event subscriptions PresenterBase.EventAggregate.GetEvent<ModulesLoadedEvent>().Subscribe(OnModulesLoaded); } After all modules have been loaded, the following handler is invoked: private void OnModulesLoaded(EventArgs e) { allModulesLoaded = true; Mouse.OverrideCursor = null; Cursor = System.Windows.Input.Cursors.Arrow; } Problem is, I do not see this wait cursor. What I am missing here? FWIW, I got a hint from this post http://stackoverflow.com/questions/2078766/showing-the-wait-cursor TIA.

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