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• Classical task-scheduling assignment

  - by Bruno

  I am working on a flight scheduling app (disclaimer: it's for a college project, so no code answers, please). Please read this question w/ a quantum of attention before answering as it has a lot of peculiarities :( First, some terminology issues: You have planes and flights, and you have to pair them up. For simplicity's sake, we'll assume that a plane is free as soon as the flight using it prior lands. Flights are seen as tasks: They have a duration They have dependencies They have an expected date/time for beginning Planes can be seen as resources to be used by tasks (or flights, in our terminology). Flights have a specific type of plane needed. e.g. flight 200 needs a plane of type B. Planes obviously are of one and only one specific type, e.g., Plane Airforce One is of type C. A "project" is the set of all the flights by an airline in a given time period. The functionality required is: Finding the shortest possible duration for a said project The earliest and latest possible start for a task (flight) The critical tasks, with basis on provided data, complete with identifiers of preceding tasks. Automatically pair up flights and planes, so as to get all flights paired up with a plane. (Note: the duration of flights is fixed) Get a Gantt diagram with the projects scheduling, in which all flights begin as early as possible, showing all previously referred data graphically (dependencies, time info, etc.) So the questions is: How in the world do I achieve this? Particularly: We are required to use a graph. What do the graph's edges and nodes respectively symbolise? Are we required to discard tasks to achieve the critical tasks set? If you could also recommend some algorithms for us to look up, that'd be great.

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• Import CSV to class structure as the user defines

  - by Assimilater

  I have a contact manager program and I would like to offer the feature to import csv files. The problem is that different data sources order the fields in different ways. I thought of programming an interface for the user to tell it the field order and how to handle exceptions. Here is an example line in one of many possible field orders: "ID#","Name","Rank","Address1","Address2","City","State","Country","Zip","Phone#","Email","Join Date","Sponsor ID","Sponsor Name" "Z1234","Call, Anson","STU","1234 E. 6578 S.","","Somecity","TX","United States","012345","000-000-0000","[email protected]","5/24/2010","z12343","Quantum Independence" Notice that in one data field "Name" there is a comma to separate last name and first name and in another there is not. My plan is to have a line for each field (ie ID, Name, City etc.) and a statement "import to" and list box with options like: Don't Import, BusinessJoin Date, First Name, Zip and the program recognizes those as properties of an object... I'd also like the user to be able to record preset field orders so they can re-use them for csv files from the same download source. Then I also need it to check if a record all ready exists (is there a record for Anson Call all ready?) and allow the user to tell it what to do if there is a record (ie mailing address may have changes, so if that field is filled overwrite it, or this mailing address is invalid, leave the current data untouched for this person, overwrite the rest). While I'm capable of coding this...i'm not very excited about it and I'm wondering if there's a tool or set of tools out there to all ready perform most of this functionality... I hope this makes sense...

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• Do you ever make a code change and just test rather than trying to fully understand the change you'v

  - by Clay Nichols

  I'm working in a 12 year old code base which I have been the only developer on. There are times that I'll make a a very small change based on an intuition (or quantum leap in logic ;-). Usually I try to deconstruct that change and make sure I read thoroughly the code. However sometimes, (more and more these days) I just test and make sure it had the effect I wanted. (I'm a pretty thorough tester and would test even if I read the code). This works for me and we have surprisingly (compared to most software I see) few bugs escape into the wild. But what I'm wondering is whether this is just the "art" side of coding. Yes, in an ideal world you would exhaustively read every bit of code that your change modified, but I in practice, if you're confident that it only affects a small section of code, is this a common practice? I can obviously see where this would be a disastrous approach in the hands of a poor programmer. But then, I've seen programmers who ostensibly are reading the code and break stuff left and right (in their own code based which only they have been working on).

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• Parallel programming, are we not learning from history again?

  - by mezmo

  I started programming because I was a hardware guy that got bored, I thought the problems being solved in the software side of things were much more interesting than those in hardware. At that time, most of the electrical buses I dealt with were serial, some moving data as fast as 1.5 megabit!! ;) Over the years these evolved into parallel buses in order to speed communication up, after all, transferring 8/16/32/64, whatever bits at a time incredibly speeds up the transfer. Well, our ability to create and detect state changes got faster and faster, to the point where we could push data so fast that interference between parallel traces or cable wires made cleaning the signal too expensive to continue, and we still got reasonable performance from serial interfaces, heck some graphics interfaces are even happening over USB for a while now. I think I'm seeing a like trend in software now, our processors were getting faster and faster, so we got good at building "serial" software. Now we've hit a speed bump in raw processor speed, so we're adding cores, or "traces" to the mix, and spending a lot of time and effort on learning how to properly use those. But I'm also seeing what I feel are advances in things like optical switching and even quantum computing that could take us far more quickly that I was expecting back to the point where "serial programming" again makes the most sense. What are your thoughts?

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• What is in your Mathematica tool bag?

  - by Timo

  We all know that Mathematica is great, but it also often lacks critical functionality. What kind of external packages / tools / resources do you use with Mathematica? I'll edit (and invite anyone else to do so too) this main post to include resources which are focused on general applicability in scientific research and which as many people as possible will find useful. Feel free to contribute anything, even small code snippets (as I did below for a timing routine). Also, undocumented and useful features in Mathematica 7 and beyond you found yourself, or dug up from some paper/site are most welcome. Please include a short description or comment on why something is great or what utility it provides. If you link to books on Amazon with affiliate links please mention it, e.g., by putting your name after the link. Packages: LevelScheme is a package that greatly expands Mathematica's capability to produce good looking plots. I use it if not for anything else then for the much, much improved control over frame/axes ticks. David Park's Presentation Package ($50 - no charge for updates) Tools: MASH is Daniel Reeves's excellent perl script essentially providing scripting support for Mathematica 7. (This is finally built in as of Mathematica 8 with the -script option.) Resources: Wolfram's own repository MathSource has a lot of useful if narrow notebooks for various applications. Also check out the other sections such as Current Documentation, Courseware for lectures, and Demos for, well, demos. Books: Mathematica programming: an advanced introduction by Leonid Shifrin (web, pdf) is a must read if you want to do anything more than For loops in Mathematica. Quantum Methods with Mathematica by James F. Feagin (amazon) The Mathematica Book by Stephen Wolfram (amazon) (web) Schaum's Outline (amazon) Mathematica in Action by Stan Wagon (amazon) - 600 pages of neat examples and goes up to Mathematica version 7. Visualization techniques are especially good, you can see some of them on the author's Demonstrations Page. Mathematica Programming Fundamentals by Richard Gaylord (pdf) - A good concise introduction to most of what you need to know about Mathematica programming. Undocumented (or scarcely documented) Features: How to customize Mathematica keyboard shortcuts. See this question. How to inspect patterns and functions used by Mathematica's own functions. See this answer How to achieve Consistent size for GraphPlots in Mathematica? See this question.

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• How do we, as a community, help encourage programming in public schools? (Or state Schools for the U

  - by NoMoreZealots

  PRIMARY MOTIVATION My office gets involved with the "First Robotics" competitions and one thing that lingers year to year is the students typically have no preparation for doing even simple programming as part of the public schools system. While the science classes provide some basic grasp of mechanical and electrical concepts, by in large computer programming gets no coverage from the curriculum. (This my be different in other areas of the country/world.) What makes it worse is there is only a short period of time you have to prepare the student's and help them design the robot. Talking to some professors from local colleges, it's a problem because you can't assume even the most basic understanding for freshman CS majors. Languages like Python, Lua and BASIC are simple enough for at least high school level students, if not younger. SCOPE So how do you get public schools to support a programming, at least to the level of "Try it in BASIC" examples that used to be at the end of a chapter in my Algebra book? At least enough to prepare them for event's such as the FIRST Robotic competitions. Which the primary objectives are to teach problem solving and team work, and to possible foster an interest in Math, Science and Engineering in general. (Not force feed to them, as some people her seem to be implying.) Edit: Why teach kids: (Since 2000 CS enrollment in US colleges has decreased by 70% while college enrollment has increased, this is a PROBLEM.) Saying there is no value in teaching someone programming in Jr./High school because they might think "they know programming." Is like saying there's no value in teaching High school science and physics, because they might decide they "know physics." Leading to abuse like: "I passed a high school physics class, I'm going to develop a Unified Quantum Gravitational Theory." Better Prepared students are better students. Instead it would allows college programs to raise the bar on the entry level courses, allowing students to be weeded out based on their understanding of more advanced material. Plus people who did poorly in that in topic in High school aren't as likely to say "I think there's money in computer's so I'll computer science." Plus if people take it in high school and decide THEN that it's not for them, it's better than them wasting their money to PAY a college to figure that out. The result is that people who take the degree are more likely to succeed and be there for the RIGHT reasons. (i.e. It's what they REALLY want to do. And that's REALLY the key to being good at anything.) Programming is like anything else, the more practice and genuine interest you have the better you get. If you start them later, they get less practice. The earlier give them the opportunity to start, the more practice they will get. All other things equal, the more practice the better the programmer.

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• Algorithm for finding symmetries of a tree

  - by Paxinum

  I have n sectors, enumerated 0 to n-1 counterclockwise. The boundaries between these sectors are infinite branches (n of them). The sectors live in the complex plane, and for n even, sector 0 and n/2 are bisected by the real axis, and the sectors are evenly spaced. These branches meet at certain points, called junctions. Each junction is adjacent to a subset of the sectors (at least 3 of them). Specifying the junctions, (in pre-fix order, lets say, starting from junction adjacent to sector 0 and 1), and the distance between the junctions, uniquely describes the tree. Now, given such a representation, how can I see if it is symmetric wrt the real axis? For example, n=6, the tree (0,1,5)(1,2,4,5)(2,3,4) have three junctions on the real line, so it is symmetric wrt the real axis. If the distances between (015) and (1245) is equal to distance from (1245) to (234), this is also symmetric wrt the imaginary axis. The tree (0,1,5)(1,2,5)(2,4,5)(2,3,4) have 4 junctions, and this is never symmetric wrt either imaginary or real axis, but it has 180 degrees rotation symmetry if the distance between the first two and the last two junctions in the representation are equal. Edit: This is actually for my research. I have posted the question at mathoverflow as well, but my days in competition programming tells me that this is more like an IOI task. Code in mathematica would be excellent, but java, python, or any other language readable by a human suffices. Here are some examples (pretend the double edges are single and we have a tree) http://www2.math.su.se/~per/files.php?file=contr_ex_1.pdf http://www2.math.su.se/~per/files.php?file=contr_ex_2.pdf http://www2.math.su.se/~per/files.php?file=contr_ex_5.pdf Example 1 is described as (0,1,4)(1,2,4)(2,3,4)(0,4,5) with distances (2,1,3). Example 2 is described as (0,1,4)(1,2,4)(2,3,4)(0,4,5) with distances (2,1,1). Example 5 is described as (0,1,4,5)(1,2,3,4) with distances (2). So, given the description/representation, I want to find some algorithm to decide if it is symmetric wrt real, imaginary, and rotation 180 degrees. The last example have 180 degree symmetry. (These symmetries corresponds to special kinds of potential in the Schroedinger equation, which has nice properties in quantum mechanics.)

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• Powershell $LastExitCode=0 but $?=False . Redirecting stderr to stdout gives NativeCommandError

  - by Colonel Panic

  Can anyone explain Powershell's surprising behaviour in the second example below? First, a example of sane behaviour: PS C:\> & cmd /c "echo Hello from standard error 1>&2"; echo "`$LastExitCode=$LastExitCode and `$?=$?" Hello from standard error $LastExitCode=0 and $?=True No surprises. I print a message to standard error (using cmd's echo). I inspect the variables $? and $LastExitCode. They equal to True and 0 respectively, as expected. However, if I ask Powershell to redirect standard error to standard output over the first command, I get a NativeCommandError: PS C:\> & cmd /c "echo Hello from standard error 1>&2" 2>&1; echo "`$LastExitCode=$LastExitCode and `$?=$?" cmd.exe : Hello from standard error At line:1 char:4 + cmd <<<< /c "echo Hello from standard error 1>&2" 2>&1; echo "`$LastExitCode=$LastExitCode and `$?=$?" + CategoryInfo : NotSpecified: (Hello from standard error :String) [], RemoteException + FullyQualifiedErrorId : NativeCommandError $LastExitCode=0 and $?=False My first question, why the NativeCommandError ? Secondly, why is $? False when cmd ran successfully and $LastExitCode is 0? Powershell's docs about_Automatic_Variables don't explicitly define $?. I always supposed it is True if and only if $LastExitCode is 0 but my example contradicts that. Here's how I came across this behaviour in the real-world (simplified). It really is FUBAR. I was calling one Powershell script from another. The inner script: cmd /c "echo Hello from standard error 1>&2" if (! $?) { echo "Job failed. Sending email.." exit 1 } # do something else Running this simply .\job.ps1, it works fine, no email is sent. However, I was calling it from another Powershell script, logging to a file .\job.ps1 2>&1 > log.txt. In this case, an email is sent! Here, the act of observing a phenomenon changes its outcome. This feels like quantum physics rather than scripting! [Interestingly: .\job.ps1 2>&1 may or not blow up depending on where you run it]

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• Fun with Aggregates

  - by Paul White

  There are interesting things to be learned from even the simplest queries.  For example, imagine you are given the task of writing a query to list AdventureWorks product names where the product has at least one entry in the transaction history table, but fewer than ten. One possible query to meet that specification is: SELECT p.Name FROM Production.Product AS p JOIN Production.TransactionHistory AS th ON p.ProductID = th.ProductID GROUP BY p.ProductID, p.Name HAVING COUNT_BIG(*) < 10; That query correctly returns 23 rows (execution plan and data sample shown below): The execution plan looks a bit different from the written form of the query: the base tables are accessed in reverse order, and the aggregation is performed before the join.  The general idea is to read all rows from the history table, compute the count of rows grouped by ProductID, merge join the results to the Product table on ProductID, and finally filter to only return rows where the count is less than ten. This ‘fully-optimized’ plan has an estimated cost of around 0.33 units.  The reason for the quote marks there is that this plan is not quite as optimal as it could be – surely it would make sense to push the Filter down past the join too?  To answer that, let’s look at some other ways to formulate this query.  This being SQL, there are any number of ways to write logically-equivalent query specifications, so we’ll just look at a couple of interesting ones.  The first query is an attempt to reverse-engineer T-SQL from the optimized query plan shown above.  It joins the result of pre-aggregating the history table to the Product table before filtering: SELECT p.Name FROM ( SELECT th.ProductID, cnt = COUNT_BIG(*) FROM Production.TransactionHistory AS th GROUP BY th.ProductID ) AS q1 JOIN Production.Product AS p ON p.ProductID = q1.ProductID WHERE q1.cnt < 10; Perhaps a little surprisingly, we get a slightly different execution plan: The results are the same (23 rows) but this time the Filter is pushed below the join!  The optimizer chooses nested loops for the join, because the cardinality estimate for rows passing the Filter is a bit low (estimate 1 versus 23 actual), though you can force a merge join with a hint and the Filter still appears below the join.  In yet another variation, the < 10 predicate can be ‘manually pushed’ by specifying it in a HAVING clause in the “q1” sub-query instead of in the WHERE clause as written above. The reason this predicate can be pushed past the join in this query form, but not in the original formulation is simply an optimizer limitation – it does make efforts (primarily during the simplification phase) to encourage logically-equivalent query specifications to produce the same execution plan, but the implementation is not completely comprehensive. Moving on to a second example, the following query specification results from phrasing the requirement as “list the products where there exists fewer than ten correlated rows in the history table”: SELECT p.Name FROM Production.Product AS p WHERE EXISTS ( SELECT * FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID HAVING COUNT_BIG(*) < 10 ); Unfortunately, this query produces an incorrect result (86 rows): The problem is that it lists products with no history rows, though the reasons are interesting.  The COUNT_BIG(*) in the EXISTS clause is a scalar aggregate (meaning there is no GROUP BY clause) and scalar aggregates always produce a value, even when the input is an empty set.  In the case of the COUNT aggregate, the result of aggregating the empty set is zero (the other standard aggregates produce a NULL).  To make the point really clear, let’s look at product 709, which happens to be one for which no history rows exist: -- Scalar aggregate SELECT COUNT_BIG(*) FROM Production.TransactionHistory AS th WHERE th.ProductID = 709;   -- Vector aggregate SELECT COUNT_BIG(*) FROM Production.TransactionHistory AS th WHERE th.ProductID = 709 GROUP BY th.ProductID; The estimated execution plans for these two statements are almost identical: You might expect the Stream Aggregate to have a Group By for the second statement, but this is not the case.  The query includes an equality comparison to a constant value (709), so all qualified rows are guaranteed to have the same value for ProductID and the Group By is optimized away. In fact there are some minor differences between the two plans (the first is auto-parameterized and qualifies for trivial plan, whereas the second is not auto-parameterized and requires cost-based optimization), but there is nothing to indicate that one is a scalar aggregate and the other is a vector aggregate.  This is something I would like to see exposed in show plan so I suggested it on Connect.  Anyway, the results of running the two queries show the difference at runtime: The scalar aggregate (no GROUP BY) returns a result of zero, whereas the vector aggregate (with a GROUP BY clause) returns nothing at all.  Returning to our EXISTS query, we could ‘fix’ it by changing the HAVING clause to reject rows where the scalar aggregate returns zero: SELECT p.Name FROM Production.Product AS p WHERE EXISTS ( SELECT * FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID HAVING COUNT_BIG(*) BETWEEN 1 AND 9 ); The query now returns the correct 23 rows: Unfortunately, the execution plan is less efficient now – it has an estimated cost of 0.78 compared to 0.33 for the earlier plans.  Let’s try adding a redundant GROUP BY instead of changing the HAVING clause: SELECT p.Name FROM Production.Product AS p WHERE EXISTS ( SELECT * FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID GROUP BY th.ProductID HAVING COUNT_BIG(*) < 10 ); Not only do we now get correct results (23 rows), this is the execution plan: I like to compare that plan to quantum physics: if you don’t find it shocking, you haven’t understood it properly :)  The simple addition of a redundant GROUP BY has resulted in the EXISTS form of the query being transformed into exactly the same optimal plan we found earlier.  What’s more, in SQL Server 2008 and later, we can replace the odd-looking GROUP BY with an explicit GROUP BY on the empty set: SELECT p.Name FROM Production.Product AS p WHERE EXISTS ( SELECT * FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID GROUP BY () HAVING COUNT_BIG(*) < 10 ); I offer that as an alternative because some people find it more intuitive (and it perhaps has more geek value too).  Whichever way you prefer, it’s rather satisfying to note that the result of the sub-query does not exist for a particular correlated value where a vector aggregate is used (the scalar COUNT aggregate always returns a value, even if zero, so it always ‘EXISTS’ regardless which ProductID is logically being evaluated). The following query forms also produce the optimal plan and correct results, so long as a vector aggregate is used (you can probably find more equivalent query forms): WHERE Clause SELECT p.Name FROM Production.Product AS p WHERE ( SELECT COUNT_BIG(*) FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID GROUP BY () ) < 10; APPLY SELECT p.Name FROM Production.Product AS p CROSS APPLY ( SELECT NULL FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID GROUP BY () HAVING COUNT_BIG(*) < 10 ) AS ca (dummy); FROM Clause SELECT q1.Name FROM ( SELECT p.Name, cnt = ( SELECT COUNT_BIG(*) FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID GROUP BY () ) FROM Production.Product AS p ) AS q1 WHERE q1.cnt < 10; This last example uses SUM(1) instead of COUNT and does not require a vector aggregate…you should be able to work out why :) SELECT q.Name FROM ( SELECT p.Name, cnt = ( SELECT SUM(1) FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID ) FROM Production.Product AS p ) AS q WHERE q.cnt < 10; The semantics of SQL aggregates are rather odd in places.  It definitely pays to get to know the rules, and to be careful to check whether your queries are using scalar or vector aggregates.  As we have seen, query plans do not show in which ‘mode’ an aggregate is running and getting it wrong can cause poor performance, wrong results, or both. © 2012 Paul White Twitter: @SQL_Kiwi email: [email protected]

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• Fun with Aggregates

  - by Paul White

  There are interesting things to be learned from even the simplest queries.  For example, imagine you are given the task of writing a query to list AdventureWorks product names where the product has at least one entry in the transaction history table, but fewer than ten. One possible query to meet that specification is: SELECT p.Name FROM Production.Product AS p JOIN Production.TransactionHistory AS th ON p.ProductID = th.ProductID GROUP BY p.ProductID, p.Name HAVING COUNT_BIG(*) < 10; That query correctly returns 23 rows (execution plan and data sample shown below): The execution plan looks a bit different from the written form of the query: the base tables are accessed in reverse order, and the aggregation is performed before the join.  The general idea is to read all rows from the history table, compute the count of rows grouped by ProductID, merge join the results to the Product table on ProductID, and finally filter to only return rows where the count is less than ten. This ‘fully-optimized’ plan has an estimated cost of around 0.33 units.  The reason for the quote marks there is that this plan is not quite as optimal as it could be – surely it would make sense to push the Filter down past the join too?  To answer that, let’s look at some other ways to formulate this query.  This being SQL, there are any number of ways to write logically-equivalent query specifications, so we’ll just look at a couple of interesting ones.  The first query is an attempt to reverse-engineer T-SQL from the optimized query plan shown above.  It joins the result of pre-aggregating the history table to the Product table before filtering: SELECT p.Name FROM ( SELECT th.ProductID, cnt = COUNT_BIG(*) FROM Production.TransactionHistory AS th GROUP BY th.ProductID ) AS q1 JOIN Production.Product AS p ON p.ProductID = q1.ProductID WHERE q1.cnt < 10; Perhaps a little surprisingly, we get a slightly different execution plan: The results are the same (23 rows) but this time the Filter is pushed below the join!  The optimizer chooses nested loops for the join, because the cardinality estimate for rows passing the Filter is a bit low (estimate 1 versus 23 actual), though you can force a merge join with a hint and the Filter still appears below the join.  In yet another variation, the < 10 predicate can be ‘manually pushed’ by specifying it in a HAVING clause in the “q1” sub-query instead of in the WHERE clause as written above. The reason this predicate can be pushed past the join in this query form, but not in the original formulation is simply an optimizer limitation – it does make efforts (primarily during the simplification phase) to encourage logically-equivalent query specifications to produce the same execution plan, but the implementation is not completely comprehensive. Moving on to a second example, the following query specification results from phrasing the requirement as “list the products where there exists fewer than ten correlated rows in the history table”: SELECT p.Name FROM Production.Product AS p WHERE EXISTS ( SELECT * FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID HAVING COUNT_BIG(*) < 10 ); Unfortunately, this query produces an incorrect result (86 rows): The problem is that it lists products with no history rows, though the reasons are interesting.  The COUNT_BIG(*) in the EXISTS clause is a scalar aggregate (meaning there is no GROUP BY clause) and scalar aggregates always produce a value, even when the input is an empty set.  In the case of the COUNT aggregate, the result of aggregating the empty set is zero (the other standard aggregates produce a NULL).  To make the point really clear, let’s look at product 709, which happens to be one for which no history rows exist: -- Scalar aggregate SELECT COUNT_BIG(*) FROM Production.TransactionHistory AS th WHERE th.ProductID = 709;   -- Vector aggregate SELECT COUNT_BIG(*) FROM Production.TransactionHistory AS th WHERE th.ProductID = 709 GROUP BY th.ProductID; The estimated execution plans for these two statements are almost identical: You might expect the Stream Aggregate to have a Group By for the second statement, but this is not the case.  The query includes an equality comparison to a constant value (709), so all qualified rows are guaranteed to have the same value for ProductID and the Group By is optimized away. In fact there are some minor differences between the two plans (the first is auto-parameterized and qualifies for trivial plan, whereas the second is not auto-parameterized and requires cost-based optimization), but there is nothing to indicate that one is a scalar aggregate and the other is a vector aggregate.  This is something I would like to see exposed in show plan so I suggested it on Connect.  Anyway, the results of running the two queries show the difference at runtime: The scalar aggregate (no GROUP BY) returns a result of zero, whereas the vector aggregate (with a GROUP BY clause) returns nothing at all.  Returning to our EXISTS query, we could ‘fix’ it by changing the HAVING clause to reject rows where the scalar aggregate returns zero: SELECT p.Name FROM Production.Product AS p WHERE EXISTS ( SELECT * FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID HAVING COUNT_BIG(*) BETWEEN 1 AND 9 ); The query now returns the correct 23 rows: Unfortunately, the execution plan is less efficient now – it has an estimated cost of 0.78 compared to 0.33 for the earlier plans.  Let’s try adding a redundant GROUP BY instead of changing the HAVING clause: SELECT p.Name FROM Production.Product AS p WHERE EXISTS ( SELECT * FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID GROUP BY th.ProductID HAVING COUNT_BIG(*) < 10 ); Not only do we now get correct results (23 rows), this is the execution plan: I like to compare that plan to quantum physics: if you don’t find it shocking, you haven’t understood it properly :)  The simple addition of a redundant GROUP BY has resulted in the EXISTS form of the query being transformed into exactly the same optimal plan we found earlier.  What’s more, in SQL Server 2008 and later, we can replace the odd-looking GROUP BY with an explicit GROUP BY on the empty set: SELECT p.Name FROM Production.Product AS p WHERE EXISTS ( SELECT * FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID GROUP BY () HAVING COUNT_BIG(*) < 10 ); I offer that as an alternative because some people find it more intuitive (and it perhaps has more geek value too).  Whichever way you prefer, it’s rather satisfying to note that the result of the sub-query does not exist for a particular correlated value where a vector aggregate is used (the scalar COUNT aggregate always returns a value, even if zero, so it always ‘EXISTS’ regardless which ProductID is logically being evaluated). The following query forms also produce the optimal plan and correct results, so long as a vector aggregate is used (you can probably find more equivalent query forms): WHERE Clause SELECT p.Name FROM Production.Product AS p WHERE ( SELECT COUNT_BIG(*) FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID GROUP BY () ) < 10; APPLY SELECT p.Name FROM Production.Product AS p CROSS APPLY ( SELECT NULL FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID GROUP BY () HAVING COUNT_BIG(*) < 10 ) AS ca (dummy); FROM Clause SELECT q1.Name FROM ( SELECT p.Name, cnt = ( SELECT COUNT_BIG(*) FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID GROUP BY () ) FROM Production.Product AS p ) AS q1 WHERE q1.cnt < 10; This last example uses SUM(1) instead of COUNT and does not require a vector aggregate…you should be able to work out why :) SELECT q.Name FROM ( SELECT p.Name, cnt = ( SELECT SUM(1) FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID ) FROM Production.Product AS p ) AS q WHERE q.cnt < 10; The semantics of SQL aggregates are rather odd in places.  It definitely pays to get to know the rules, and to be careful to check whether your queries are using scalar or vector aggregates.  As we have seen, query plans do not show in which ‘mode’ an aggregate is running and getting it wrong can cause poor performance, wrong results, or both. © 2012 Paul White Twitter: @SQL_Kiwi email: [email protected]

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• Thread scheduling Round Robin / scheduling dispatch

  - by MRP

  #include <pthread.h> #include <stdio.h> #include <stdlib.h> #include <semaphore.h> #define NUM_THREADS 4 #define COUNT_LIMIT 13 int done = 0; int count = 0; int quantum = 2; int thread_ids[4] = {0,1,2,3}; int thread_runtime[4] = {0,5,4,7}; pthread_mutex_t count_mutex; pthread_cond_t count_threshold_cv; void * inc_count(void * arg); static sem_t count_sem; int quit = 0; ///////// Inc_Count//////////////// void *inc_count(void *t) { long my_id = (long)t; int i; sem_wait(&count_sem); /////////////CRIT SECTION////////////////////////////////// printf("run_thread = %d\n",my_id); printf("%d \n",thread_runtime[my_id]); for( i=0; i < thread_runtime[my_id];i++) { printf("runtime= %d\n",thread_runtime[my_id]); pthread_mutex_lock(&count_mutex); count++; if (count == COUNT_LIMIT) { pthread_cond_signal(&count_threshold_cv); printf("inc_count(): thread %ld, count = %d Threshold reached.\n", my_id, count); } printf("inc_count(): thread %ld, count = %d, unlocking mutex\n",my_id, count); pthread_mutex_unlock(&count_mutex); sleep(1) ; }//End For sem_post(&count_sem); // Next Thread Enters Crit Section pthread_exit(NULL); } /////////// Count_Watch //////////////// void *watch_count(void *t) { long my_id = (long)t; printf("Starting watch_count(): thread %ld\n", my_id); pthread_mutex_lock(&count_mutex); if (count<COUNT_LIMIT) { pthread_cond_wait(&count_threshold_cv, &count_mutex); printf("watch_count(): thread %ld Condition signal received.\n", my_id); printf("watch_count(): thread %ld count now = %d.\n", my_id, count); } pthread_mutex_unlock(&count_mutex); pthread_exit(NULL); } ////////////////// Main //////////////// int main (int argc, char *argv[]) { int i; long t1=0, t2=1, t3=2, t4=3; pthread_t threads[4]; pthread_attr_t attr; sem_init(&count_sem, 0, 1); /* Initialize mutex and condition variable objects */ pthread_mutex_init(&count_mutex, NULL); pthread_cond_init (&count_threshold_cv, NULL); /* For portability, explicitly create threads in a joinable state */ pthread_attr_init(&attr); pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE); pthread_create(&threads[0], &attr, watch_count, (void *)t1); pthread_create(&threads[1], &attr, inc_count, (void *)t2); pthread_create(&threads[2], &attr, inc_count, (void *)t3); pthread_create(&threads[3], &attr, inc_count, (void *)t4); /* Wait for all threads to complete */ for (i=0; i<NUM_THREADS; i++) { pthread_join(threads[i], NULL); } printf ("Main(): Waited on %d threads. Done.\n", NUM_THREADS); /* Clean up and exit */ pthread_attr_destroy(&attr); pthread_mutex_destroy(&count_mutex); pthread_cond_destroy(&count_threshold_cv); pthread_exit(NULL); } I am trying to learn thread scheduling, there is a lot of technical coding that I don't know. I do know in theory how it should work, but having trouble getting started in code... I know, at least I think, this program is not real time and its not meant to be. Some how I need to create a scheduler dispatch to control the threads in the order they should run... RR FCFS SJF ect. Right now I don't have a dispatcher. What I do have is semaphores/ mutex to control the threads. This code does run FCFS... and I have been trying to use semaphores to create a RR.. but having a lot of trouble. I believe it would be easier to create a dispatcher but I dont know how. I need help, I am not looking for answers just direction.. some sample code will help to understand a bit more. Thank you.

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• move element li into ul with jquery

  - by ron

  Hi everybody i'm looking for a solution to move an element that i need to move into a .... im using jquery and i leave here the code i tried with different things but wasn't working it. this is the big menu <ul class="sf-menu"> <li><a href="">Student Centre</a> <ul> <li><a href="9">STUDENT CENTRAL WEBSITE</a></li> <li><a href="10">STUDENT CENTRAL EMAIL</a></li> <li><a href="11">CCM STUDENT SURVIAL TIPS</a></li> <li><a href="12">VET TUTTTION ASSURANSE</a></li> <li><a href="13">WHAT GOING ON AT CCM</a></li> <li><a href="14">IMPORTANT STUDENTS NOTICE</a></li> </ul> </li> <li><a href="">Research</a> <ul> <li><a href="_16">WHAT IS HOLISTIC KINESIOLOGY ?</a></li> <li><a href="_17">TRANF. CHILDREN W/ LEARNING DIFFICULTIES</a></li> <li><a href="_18">HEALING WITH HOLISTIC KINESIOLOGY</a></li> <li><a href="_19">UNDERSTANDING ASPERGER'S SYNDROME</a></li> <li><a href="_20">DAVID CORBY THE DIRECTOR OF CCM</a></li> <li><a href="_21">HELPING PEOPLE CREATE THEIR OWN MIRACLES</a></li> <li><a href="_22">MAGNESIUM AND COLLOIDAL MINERALS</a></li> <li><a href="_23">BRAIN ENERGETICS CHAKRAS AND NADIS</a></li> <li><a href="_24">KINESIOLOGY FAQ'S</a></li>' </ul> </li> <li><a href="25">Contact Us</a></li> <li><a href="26">A - Z</a></li> </ul> and i need to add this li to ul but i need to put in the second place after the first not nested <li id="faculty"> <a href="#">Faculty Courses </a> <ul> <li><a href="">INTENSE SHORT COURSES</a><ul> <li><a href="_59">CRYSTAL KINESIOLOGY ONE</a></li> <li><a href="_60">APPLIED PHYSIOLOGY</a></li> <li><a href="_61">VIBRATIONAL HEALING SYSTEMS 1</a></li> <li><a href="_62">VIBRATIONAL HEALING SYSTEMS 2</a></li> <li><a href="_63">VIBRATIONAL HEALING SYSTEMS 3</a></li> <li><a href="_64">VIBRATIONAL HEALING SYSTEMS 6</a></li> <li><a href="_65">NUTRITIONAL KINESIOLOGY</a></li> <li><a href="_66">QUANTUM HARMONICS</a></li><li><a href="_67">CHAKRA HOLOGRAM</a></li> <li><a href="_68">CLINICAL APPLICATIONS OF KINESIOLOGY</a></li> <li><a href="_69">COUNSELLING KINESIOLOGY</a></li> <li><a href="_70">HARMONISING CHI FLOW</a></li> </ul> </li> <li><a href="=53">FREE INTRUCTION COURSE DAYS</a> <ul> <li><a href="=53_56">HOLISTIC KINESIOLOGY</a></li> <li><a href="=53_57">TRANSPERSONAL COUNSELLING</a></li> <li><a href="=53_58">SHAMMANISM &amp; TRANSFORMATIONAL MASK</a></li> </ul> </li> <li><a href="=50">DIPLOMA MASK AND TRADITIONAL HEALING</a></li> <li><a href="=43">DIPLOMA TRANSPERSONAL ART THERAPY</a></li> <li><a href="=42">DIPLOMA HOLISTIC KINESIOLOGY</a></li> <li><a href="=47">ADVANCE DIPLOMA HOLISTIC KINESIOLOGY</a></li> <li><a href="=48">DIPLOMA DINAMIC AND FUNCTIONAL</a></li> <li><a href="=49">CERTIFICATE MASK AND TRADITIONAL HEALING</a></li> <li><a href="=51">DIPLOMA TRANSPERSONAL COUNSELLING</a></li> <li><a href="=52">STUDENT CLINICS</a></li> </ul> </li> please i need you help Thanks in advance

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• JavaFX FXML communication between Application and Controller classes

  - by likethesky

  I am trying to get and destroy an external process I've created via ProcessBuilder in my FXML application close, but it's not working. This is based on the helpful advice Sergey Grinev gave me here. I have tried running with/without the "// myController.setApp(this);" and with "// super.stop();" at top of subclass and at bottom (see commented out/in for that line in MyApp), but no combination works. This probably isn't related to FXML or JavaFX, though I imagine this is a common pattern for developing apps on JavaFX. I suppose I'm asking for a Java best practice for closing dependent processes in a UI-based app like this one (in this case: FXML / JavaFX based), where there is a controller class and an application class. Can you explain what I'm doing wrong? Or better: advise what I should be doing instead? Thanks. In my Application I do this: public class MyApp extends Application { @Override public void start(Stage primaryStage) throws Exception { FXMLLoader fxmlLoader = new FXMLLoader(); Scene scene = (Scene)FXMLLoader.load(getClass().getResource("MyApp.fxml")); MyAppController myController = (MyAppController)fxmlLoader.getController(); primaryStage.setScene(scene); primaryStage.show(); // myController.setApp(this); } @Override public void stop() throws Exception { // super.stop(); // this is called on fx app close, you may call it in an action handler too if (MyAppController.getScriptProcess() != null) { MyAppController.getScriptProcess().destroy(); } super.stop(); } public static void main(String[] args) { launch(args); } } In my Controller I do this: public class MyAppController implements Initializable { private Application app; private static Process scriptProcess; public void setApp(Application a) { app = a; } public static Process getScriptProcess() { return scriptProcess; } } The result when I run with the "commented-out setApp()" not commented out (that is, left in the start method), is the following, immediately upon launch (the main Scene flashes, then disappears, then this dialog appears: "JavaFX Launcher Error: Exception while running Application" And it gives an, "Exception in Application start method" in the console as well. The result when I leave out the "commented-out code" in my MyApp above (that is, remove the "setApp()" from the start method), is that my app does indeed close, but gives this error when it closes: Exception in thread "JavaFX Application Thread" java.lang.RuntimeException: java.lang.reflect.InvocationTargetException at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1440) at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:69) at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:217) at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:170) at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:38) at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:37) at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92) at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:35) at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92) at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:35) at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92) at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:53) at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:28) at javafx.event.Event.fireEvent(Event.java:171) at javafx.scene.Node.fireEvent(Node.java:6863) at javafx.scene.control.Button.fire(Button.java:179) at com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(ButtonBehavior.java:193) at com.sun.javafx.scene.control.skin.SkinBase$4.handle(SkinBase.java:336) at com.sun.javafx.scene.control.skin.SkinBase$4.handle(SkinBase.java:329) at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:64) at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:217) at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:170) at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:38) at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:37) at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92) at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:35) at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92) at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:35) at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92) at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:35) at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92) at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:53) at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:33) at javafx.event.Event.fireEvent(Event.java:171) at javafx.scene.Scene$MouseHandler.process(Scene.java:3324) at javafx.scene.Scene$MouseHandler.process(Scene.java:3164) at javafx.scene.Scene$MouseHandler.access$1900(Scene.java:3119) at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1559) at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2261) at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:228) at com.sun.glass.ui.View.handleMouseEvent(View.java:528) at com.sun.glass.ui.View.notifyMouse(View.java:922) at com.sun.glass.ui.gtk.GtkApplication._runLoop(Native Method) at com.sun.glass.ui.gtk.GtkApplication$3$1.run(GtkApplication.java:82) at java.lang.Thread.run(Thread.java:722) Caused by: java.lang.reflect.InvocationTargetException at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:601) at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1435) ... 44 more Caused by: java.lang.NullPointerException at mypackage.MyController.handleCancel(MyController.java:300) ... 49 more Clean up...

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• CodePlex Daily Summary for Tuesday, June 28, 2011

  CodePlex Daily Summary for Tuesday, June 28, 2011Popular ReleasesCoding4Fun Tools: Coding4Fun.Phone.Toolkit v1.4.3: Fix for prompts not returning the appbarMosaic Project: Mosaic Alpha build 261: - Fixed crash when pinning applications in x64 OS - Added Hub to video widget. It shows videos from Video library (only .wmv and .avi). Can work slow if there are too much files. - Fixed some issues with scrolling - Fixed bug with html widgets - Fixed bug in Gmail widget - Added html today widget missed in previous release - Now Mosaic saves running widgets if you restarting from optionsEnhSim: EnhSim 2.4.9 BETA: 2.4.9 BETAThis release supports WoW patch 4.2 at level 85 To use this release, you must have the Microsoft Visual C++ 2010 Redistributable Package installed. This can be downloaded from http://www.microsoft.com/downloads/en/details.aspx?FamilyID=A7B7A05E-6DE6-4D3A-A423-37BF0912DB84 To use the GUI you must have the .NET 4.0 Framework installed. This can be downloaded from http://www.microsoft.com/downloads/en/details.aspx?FamilyID=9cfb2d51-5ff4-4491-b0e5-b386f32c0992 - Added in some of th....NET Reflector Add-Ins: Reflector V7 Add-Ins: All the add-ins compiled for Reflector V7TerrariViewer: TerrariViewer v4.1 [4.0 Bug Fixes]: Version 4.1 ChangelogChanged how users will Open Player files (This change makes it much easier) This allowed me to remove the "Current player file" labels that were present Changed file control icons Added submit bug button Various Bug Fixes Fixed crashes related to clicking on buffs before a character is loaded Fixed crashes related to selecting "No Buff" when choosing a new buff Fixed crashes related to clicking on a "Max" button on the buff tab before a character is loaded Cor...AcDown????? - Anime&Comic Downloader: AcDown????? v3.0 Beta8: ??AcDown???????????????，?????????????????????。????????????????????，??Acfun、Bilibili、???、???、?????，???????????、???????。 AcDown???????????????????????????，???，???????????????????。 AcDown???????C#??，?????"Acfun?????"。 ????32??64? Windows XP/Vista/7 ????????????? ??：????????Windows XP???,?????????.NET Framework 2.0???(x86)?.NET Framework 2.0???(x64)，?????"?????????"??? ??????????????，??????????： ??"AcDown?????"????????? ??v3.0 Beta8 ?? ??????????????? ???????????????(??????????) ???????...BlogEngine.NET: BlogEngine.NET 2.5: Get DotNetBlogEngine for 3 Months Free! Click Here for More Info 3 Months FREE – BlogEngine.NET Hosting – Click Here! If you want to set up and start using BlogEngine.NET right away, you should download the Web project. If you want to extend or modify BlogEngine.NET, you should download the source code. If you are upgrading from a previous version of BlogEngine.NET, please take a look at the Upgrading to BlogEngine.NET 2.5 instructions. To get started, be sure to check out our installatio...PHP Manager for IIS: PHP Manager 1.2 for IIS 7: This release contains all the functionality available in 62183 plus the following additions: Command Line Support via PowerShell - now it is possible to manage and script PHP installations on IIS by using Windows PowerShell. More information is available at Managing PHP installations with PHP Manager command line. Detection and alert when using local PHP handler - if a web site or a directory has a local copy of PHP handler mapping then the configuration changes made on upper configuration ...MiniTwitter: 1.71: MiniTwitter 1.71 ???? ?? OAuth ???????????? ????????、??????????????????? ???????????????????????SizeOnDisk: 1.0.10.0: Fix: issue 327: size format error when save settings Fix: some UI bindings trouble (sorting, refresh) Fix: user settings file deletion when corrupted Feature: TreeView virtualization (better speed with many folders) Feature: New file type DataGrid column Feature: In KByte view, show size of file < 1024B and > 0 with 3 decimal Feature: New language: Italian Task: Cleanup for speedRawr: Rawr 4.2.0: This is the Downloadable WPF version of Rawr!For web-based version see http://elitistjerks.com/rawr.php You can find the version notes at: http://rawr.codeplex.com/wikipage?title=VersionNotes Rawr AddonWe now have a Rawr Official Addon for in-game exporting and importing of character data hosted on Curse. The Addon does not perform calculations like Rawr, it simply shows your exported Rawr data in wow tooltips and lets you export your character to Rawr (including bag and bank items) like Char...HD-Trailers.NET Downloader: HD-Trailer.net Downloader 1.86: This version implements a new config flag "ConsiderTheatricalandNumberedTrailersasIdentical" that for the purposes of Exclusions only Teaser Trailer and one Trailer (named Trailer, Theatrical Traler Trailer No. 1, Trailer 1, Trailer No. 2, etc) will be downloaded. This also includes a bug fix where the .nfo file did not include the -trailer if configured for XBMC.N2 CMS: 2.2: * Web platform installer support available ** Nuget support available What's newDinamico Templates (beta) - an MVC3 & Razor based template pack using the template-first! development paradigm Boilerplate CSS & HTML5 Advanced theming with css comipilation (concrete, dark, roadwork, terracotta) Template-first! development style Content, news, listing, slider, image sizes, search, sitemap, globalization, youtube, google map Display Tokens - replaces text tokens with rendered content (usag...Circuit Diagram: Circuit Diagram v0.5 Beta: New in this release: New components: Ammeter (meter) Voltmeter (meter) Undo/redo functionality for placing/moving components Choose resolution when exporting PNG image New logoMicrosoft Ajax Minifier: Microsoft Ajax Minifier 4.23: XML input file can now specify both JS and CSS output files in the same XML file. Don't output octal escsape sequences in string literals for strict-mode scripts. Expand expression optimizations to handle more instances of logical-not being smaller. Properly handle comments that look like conditional comments but aren't because no @cc_on statement has been encountered. CSS Important comments should start on a new line, and CSS hacks should not have the ! in them. Various other smaller updates.KinectNUI: Jun 25 Alpha Release: Initial public version. No installer needed, just run the EXE.Terraria World Viewer: Version 1.5: Update June 24th Made compatible with the new tiles found in Terraria 1.0.5Kinect Earth Move: KinectEarthMove sample code: Sample code releasedThis is a sample code for Kinect for Windows SDK beta, which was demonstrated on Channel 9 Kinect for Windows SKD beta launch event on June 17 2011. Using color image and skeleton data from Kinect and user in front of Kinect can manipulate the earth between his/her hands.patterns & practices: Project Silk: Project Silk Community Drop 12 - June 22, 2011: Changes from previous drop: Minor code changes. New "Introduction" chapter. New "Modularity" chapter. Updated "Architecture" chapter. Updated "Server-Side Implementation" chapter. Updated "Client Data Management and Caching" chapter. Guidance Chapters Ready for Review The Word documents for the chapters are included with the source code in addition to the CHM to help you provide feedback. The PDF is provided as a separate download for your convenience. Installation Overview To ins...DotNetNuke® Community Edition: 06.00.00 Beta: Beta 1 (Build 2300) includes many important enhancements to the user experience. The control panel has been updated for easier access to the most important features and additional forms have been adapted to the new pattern. This release also includes many bug fixes that make it more stable than previous CTP releases. Beta ForumsNew ProjectsAI4CAD-3D: AI4CAD-3D bir 3 boyutlu tasarim ve ince ve kaba insaat metraj programidir.Beginner 2D game Dev -MokoNa: learning to make 2D games from ground up cae2rampage: A top down XNA-based multipalyer game.CamelWiki: Simple wiki software written in Perl using POD as markup language. CamelWiki can use MySQL, PostgreSQL or SQLite as database backend. DmPoster: An assistant to help us to post danmaku to bilibili.tv website. ????? bilibili.tv ?????????。 It's developed in C#. ????? C#。EasyDP: EasyDP is an open source Silverlight application to upload and manage one's display pictures in a website. It can be integrated to websites not limited to ASP.NET. It posts images up with generic HTTP form data thus it can communicate with HTTP handler written in any server-side programming language.E-Commerce TCP: Projeto E-Commerce para a cadeira de TCP da UFRGS. Semestre 01/2011.Encounter: a host-guest interaction energy calculator: Encounter is a simple program for calculating the interaction energy between two molecules using the output from a GAUSSIAN two-component counterpoise correction calculation. The Counterpoise Correction arises due to the Basis Set Superposition Error in quantum modeling.Excel add-in for regular expressions: Match, replace, and search character strings in Excel using the C++0x <regex> library.FlvBugger: ?Flv????????，???????????????????，????????。Frontdesk: Frontdesk is a form creator and autoresponder program designed in Microsoft ASP.NET MVC 2. It contains a custom member/security implementation, admin area, and lots of flexibility in form & autoresponder creation. It uses an integrated WYSIWYG editor & form field drag-and-drop.His2012: his2012ixbShop: ???????? Open-source e-commerce platformJBot: PL: Program sieciowy JBot jest chatterbotem. EN: Network program JBot is chatterbot.JungleSoft_Lux: luxKillstone PaRSS: Killstone PaRSS is a jQuery Plugin that parses an RSS feed and appends the items from the feed to a UL or OL on your webpage.Killstone PHP Framework: A simple PHP framework that helps organize your PHP application in a Model / View / Controller pattern.Orchard-PhotoTag-FamilyTree: This is an Orchard Module that allows you to tag a photo. It comes with a widget and a Page type. In addition to tagging photo's you can create a family tree/org chart to drill down into. (I originally built this for a family reunion).ResX DSL: ResX DSL is a Domain Specific Language created with Visual Studio DSL Tools. It helps to define a ResX DSL-Model with multi-language and multi-typed Ressources and generates with T4-Templates an ordinary Resx-File as well as a Proxy-Class with a given Ressources-Set.Self-Tracking Entity Generator for WPF and Silverlight: An Entity Framework project item to generate self-tracking entity classes for WPF and Silverlight applications.SharePoint 2010 Print List Ribbon Button: SharePoint 2010 Print List button on Top Ribbon for Calendar listStocks Application: This is technical demo to apply F-Sharp (F#) language in real world application. This application is close to real world enterprise application (with very optimal solutions, at least in 2011). The function of this application is to get Stock Quote Data and Historical Stock Prices from Yahoo Finance The Smart Shopping List: The Smart Shopping List makes it easier to keep track of your purchasesUmbraco Flickr API Search - XSLT Extension: An Umbraco XSLT Extension Package that enables calling the Flickr API to retrieve photos from a tag(s), user, group, and text search. The underlying engine is built off of the FlickrNET library (http://www.codeplex.com/FlickrNet).WASTLib: WASTLib is the acronim of Web Application Security Testing Library. Its main purpose is to easly create security tests for your web application. WinPanel: WinPanel ist ein nachgemachtes GNOME-Panel, dass auf Windows läuft. Es wird in Visual Basic 2010 Express programmiert.

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• CodePlex Daily Summary for Tuesday, November 20, 2012

  CodePlex Daily Summary for Tuesday, November 20, 2012Popular ReleasesTwitter Bootstrap for SharePoint: Twitter Bootstrap Master Page for SharePoint 2010: Twitter Bootstrap Master Page for SharePoint 2010 Version 1.0 Beta by Liam Powell @LiamPowell87 for more information visit my blog http://www.LiamPowell.com .WSP file can be deployed to SharePoint using powershell .Rar file contains sourceJson.NET: Json.NET 4.5 Release 11: New feature - Added ITraceWriter, MemoryTraceWriter, DiagnosticsTraceWriter New feature - Added StringEscapeHandling with options to escape HTML and non-ASCII characters New feature - Added non-generic JToken.ToObject methods New feature - Deserialize ISet<T> properties as HashSet<T> New feature - Added implicit conversions for Uri, TimeSpan, Guid New feature - Missing byte, char, Guid, TimeSpan and Uri explicit conversion operators added to JToken New feature - Special case...HigLabo: HigLabo_20121119: HigLabo_2012111 --HigLabo.Mail-- Modify bug fix of ExecuteAppend method. Add ExecuteXList method to ImapClient class. --HigLabo.Net.WindowsLive-- Add AsyncCall to WindowsLiveClient class.mojoPortal: 2.3.9.4: see release notes on mojoportal.com http://www.mojoportal.com/mojoportal-2394-released Note that we have separate deployment packages for .NET 3.5 and .NET 4.0, but we recommend you to use .NET 4, we will probably drop support for .NET 3.5 once .NET 4.5 is available The deployment package downloads on this page are pre-compiled and ready for production deployment, they contain no C# source code and are not intended for use in Visual Studio. To download the source code see getting the lates...VidCoder: 1.4.6 Beta: Brought back the x264 advanced options panel due to popular demand. Thank you for all the feedback. x264 Preset/Profile/Tune/Level has been moved back to the Video tab, along with a copy of the "extra options" string. Added Fast Decode and Zero Latency checkboxes to support multiple Tunes. Added cropping option "None". Audio bitrates that are incompatible with the encoder (such as MP3 > 320 kbps) are no longer preset on the list. Fixed crash on opening VidCoder after de-selecting "re...DotNetNuke® Store: 03.01.07: What's New in this release? IMPORTANT: this version requires DotNetNuke 04.06.02 or higher! DO NOT REPORT BUGS HERE IN THE ISSUE TRACKER, INSTEAD USE THE DotNetNuke Store Forum! Bugs corrected: - Replaced some hard coded references to the default address provider classes by the corresponding interfaces to allow the creation of another address provider with a different name. New Features: - Added the 'pickup' delivery option at checkout. - Added the 'no delivery' option in the Store Admin ...Bundle Transformer - a modular extension for ASP.NET Web Optimization Framework: Bundle Transformer 1.6.10: Version: 1.6.10 Published: 11/18/2012 Now almost all of the Bundle Transformer's assemblies is signed (except BundleTransformer.Yui.dll); In BundleTransformer.SassAndScss the SassAndCoffee.Ruby library was replaced by my own implementation of the Sass- and SCSS-compiler (based on code of the SassAndCoffee.Ruby library version 2.0.2.0); In BundleTransformer.CoffeeScript added support of CoffeeScript version 1.4.0-3; In BundleTransformer.TypeScript added support of TypeScript version 0....ExtJS based ASP.NET 2.0 Controls: FineUI v3.2.0: +2012-11-18 v3.2.0 -?????????????????SelectedValueArray????????（◇?◆:）。 -???????????????????RecoverPropertiesFromJObject????（〓?〓、????、??、Vian_Pan）。 -????????????，?????????????，???SelectedValueArray???????（sam.chang）。 -??Alert.Show???????????（swtseaman）。 -???????????????，??Icon??IconUrl????（swtseaman）。 -?????????TimePicker（??）。 -?????????，??/res.axd?css=blue.css&v=1。 -????????，?????????????，???????。 -????MenuCheckBox（???????）。 -?RadioButton??AutoPostBack??。 -???????FCKEditor?????????...BugNET Issue Tracker: BugNET 1.2: Please read our release notes for BugNET 1.2: http://blog.bugnetproject.com/bugnet-1-2-has-been-released Please do not post questions as reviews. Questions should be posted in the Discussions tab, where they will usually get promptly responded to. If you post a question as a review, you will pollute the rating, and you won't get an answer.Paint.NET PSD Plugin: 2.2.0: Changes: Layer group visibility is now applied to all layers within the group. This greatly improves the visual fidelity of complex PSD files that have hidden layer groups. Layer group names are prefixed so that users can get an indication of the layer group hierarchy. (Paint.NET has a flat list of layers, so the hierarchy is flattened out on load.) The progress bar now reports status when saving PSD files, instead of showing an indeterminate rolling bar. Performance improvement of 1...CRM 2011 Visual Ribbon Editor: Visual Ribbon Editor (1.3.1116.7): [IMPROVED] Detailed error message descriptions for FaultException [FIX] Fixed bug in rule CrmOfflineAccessStateRule which had incorrect State attribute name [FIX] Fixed bug in rule EntityPropertyRule which was missing PropertyValue attribute [FIX] Current connection information was not displayed in status bar while refreshing list of entitiesSuper Metroid Randomizer: Super Metroid Randomizer v5: v5 -Added command line functionality for automation purposes. -Implented Krankdud's change to randomize the Etecoon's item. NOTE: this version will not accept seeds from a previous version. The seed format has changed by necessity. v4 -Started putting version numbers at the top of the form. -Added a warning when suitless Maridia is required in a parsed seed. v3 -Changed seed to only generate filename-legal characters. Using old seeds will still work exactly the same. -Files can now be saved...Caliburn Micro: WPF, Silverlight, WP7 and WinRT/Metro made easy.: Caliburn.Micro v1.4: Changes This version includes many bug fixes across all platforms, improvements to nuget support and...the biggest news of all...full support for both WinRT and WP8. Download Contents Debug and Release Assemblies Samples Readme.txt License.txt Packages Available on Nuget Caliburn.Micro – The full framework compiled into an assembly. Caliburn.Micro.Start - Includes Caliburn.Micro plus a starting bootstrapper, view model and view. Caliburn.Micro.Container – The Caliburn.Micro invers...DirectX Tool Kit: November 15, 2012: November 15, 2012 Added support for WIC2 when available on Windows 8 and Windows 7 with KB 2670838 Cleaned up warning level 4 warningsDotNetNuke® Community Edition CMS: 06.02.05: Major Highlights Updated the system so that it supports nested folders in the App_Code folder Updated the Global Error Handling so that when errors within the global.asax handler happen, they are caught and shown in a page displaying the original HTTP error code Fixed issue that stopped users from specifying Link URLs that open on a new window Security FixesFixed issue in the Member Directory module that could show members to non authenticated users Fixed issue in the Lists modul...fastJSON: v2.0.10: - added MonoDroid projectxUnit.net Contrib: xunitcontrib-resharper 0.7 (RS 7.1, 6.1.1): xunitcontrib release 0.6.1 (ReSharper runner) This release provides a test runner plugin for Resharper 7.1 RTM and 6.1.1, targetting all versions of xUnit.net. (See the xUnit.net project to download xUnit.net itself.) This release drops 7.0 support and targets the latest revisions of the last two major versions of ReSharper (namely 7.0 and 6.1.1). Copies of the plugin that support previous verions of ReSharper can be downloaded from this release. Also note that all builds work against ALL ...OnTopReplica: Release 3.4: Update to the 3 version with major fixes and improvements. Compatible with Windows 8. Now runs (and requires) .NET Framework v.4.0. Added relative mode for region selection (allows the user to select regions as margins from the borders of the thumbnail, useful for windows which have a variable size but fixed size controls, like video players). Improved window seeking when restoring cloned thumbnail or cloning a window by title or by class. Improved settings persistence. Improved co...DotSpatial: DotSpatial 1.4: This is a Minor Release. See the changes in the issue tracker. Minimal -- includes DotSpatial core and essential extensions Extended -- includes debugging symbols and additional extensions Tutorials are available. Just want to run the software? End user (non-programmer) version available branded as MapWindow Want to add your own feature? Develop a plugin, using the template and contribute to the extension feed (you can also write extensions that you distribute in other ways). Components ...WinRT XAML Toolkit: WinRT XAML Toolkit - 1.3.5: WinRT XAML Toolkit based on the Windows 8 RTM SDK. Download the latest source from the SOURCE CODE page. For compiled version use NuGet. You can add it to your project in Visual Studio by going to View/Other Windows/Package Manager Console and entering: PM> Install-Package winrtxamltoolkit Features Attachable Behaviors AwaitableUI extensions Controls Converters Debugging helpers Extension methods Imaging helpers IO helpers VisualTree helpers Samples Recent changes Docum...New ProjectsAzzeton: azzetonBadminton: Source codeBitFox Expression Evaluator: Integrate evaluation of expressions wrote in fox language into your app. Part of BITFOX, a project to help in migration of Visual Foxpro apps to .NET world.Brunch: Brunch is a Visual Studio 2008 add-in that shows the name of a code branch in a toolbar that you can place wherever you want. You'll no longer have to inspect the path of a file in your project to find out which branch you are working in.CapturePoint365 - an Office 365 extension to Cropper: CapturePoint365 - an Office 365 extension to Cropper utility. CLR Profiler: Provides downloads for those who want to use a profiler of managed code, and those who want to write a profiler of managed code.CMS KickStart: Working on building a Content Management System.cricketcodeplex: uploading projectDanish Language Pack for Community Server: Danish Language Packs for Community Server 2.1 and 2007. At its inception, this project contains quite incomplete translations to Danish. This project provides a common resource where all interested parties can gradually improve on this language pack. Please join to improve the contents. The source code tree contains two major folders: One for Community Server 2.1 and one for Community Server 2007.Data Workflow Activities: OData and SQL Server Workflow Activities and DesignersDelegateMock: DelegateMock is C# library for mocking and stubbing delegates.DevMango: MongoDB ToolEasyIADP Application Component: EasyIADP application component is built for application which want to integrate to Intel AppUp Center. Enterprise Library Logging Dynamics Crm 2011 Trace Listener: Enterprise Library Trace Listener that writes to Microsoft Dynamics CRM 2011, formatting the output with an ILogFormatterEPiServer Customizable Page Reference Properties: Customizable PageReference and LinkCollection properties for EPiServer. Allows to easily setup root page and available types for selecting. This project uses cool <a href="http://episerverfpr.codeplex.com">Filtered Page Reference</a> library written by <a href="http://world.episerver.com/Blogs/Lee-Crowe">Lee Crowe</a>. For more information look at this blog post: <a href="http://dotnetcake.blogspot.com/2011/08/episerver-filtered-page-reference-easy.html">EPiServer Filtered Page Referen...exSnake: exSnake is a C# version of the classic game Snake.Friday Shopping: Windows Mobile applicationHIC Projects Home: HIC's central public location for source control, file collaboration and project management.Infinite DoWork: Example of an infinite loop.Kinect n Touch to WWT: Using Kinect and Touch devices with WWT - worldwide telescopeKoka: Koka is a function-oriented strongly typed language that separates pure values from side-effecting computations. Laboratório de Engenharia de Software - Projeto: Criado para estudar e aplicar novas tecnologias web.M26WC - Mono 2.6 Wizard Control: Wizard which runs under Mono2.6 A fork of: http://aerowizard.codeplex.com/Mercado seguridad: Este es mi summaryMVC 4 Web d?t tour du l?ch: Web d?t tour du l?ch mvc 4ObjectMerger: ObjectMerger is a class library with extension methods for merging two different objects of the same (generic) type. It's developed in C#. omr.selector.js: Easy dom selectorORM-Micro: ORM-Micro Easiest and fastest Micro ORM, you've got the queries, you've got the objects, take the best of two worlds !Primary5choo1: ????????DEMOProject1327: wdPubSync: Visual Studio's publishing solutions are slow and somewhat unreliable. PubSync is my solution to these issues. Rhythm Comet: Jogo em C# utilizando o framework XNARuntime Hello Worlds: Runtime Hello Worlds is a very simple project demonstrating a number of ways of implementing "Hello, World" in C#/.NET 4.0 in runtime generated and/or bound code.SeguridadDeSistemas: sumarySercury: ????????，????WCF??????????????。Setup Project Tuner: A VisualStudio addin that gives you some additional views on your setup project (.vdproj) filesSimple Sales Tracking CRM API Wrapper: The Simple Sales Tracking API Wrapper, enables easy extention development and integration with the hosted service at http://www.simplesalestracking.comSkincaretips: Skincare tips coding shownSQScriptRunner: Simple Quick Script Runner allows an administrator to run T-SQL Scripts against one or more servers with common characteristics. For example, an maintenance script might be targeted at a list of mirrored servers, or a list of computers running SQL Express.SystemHelperLibrary: Some helper classesTask Manager Nuke: How to write a dotnetnuke moduleThe TVDB API: Library to utilise The TVDB API.Thermo: This is the software developed for my PhD. It's about computing thermal properties of materials using first principles quantum mechanics.tool projects: Tool Projectstourism: updateVirtualPoSH Script Repository: This is the VirtualPoSH Script Repository!Wheel of Jeopardy: This is the repository for Wheel of Jeopardy project for Software Engineering 605.401.82 SU10 class.

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• .NET Code Evolution

  - by Alois Kraus

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

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