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  • Triangulation A* (TA*) pathfinding algorithm

    - by hyn
    I need help understanding the Triangle A* (TA*) algorithm that is described by Demyen in his paper Efficient Triangulation-Based Pathfinding, on pages 76-81. He describes how to adapt the regular A* algorithm for triangulation, to search for other possibly more optimal paths, even after the final node is reached/expanded. Regular A* stops when the final node is expanded, but this is not always the best path when used in a triangulated graph. This is exactly the problem I'm having. The problem is illustrated on page 78, Figure 5.4: I understand how to calculate the g and h values presented in the paper (page 80). And I think the search stop condition is: if (currentNode.fCost > shortestDistanceFound) { // stop break; } where currentNode is the search node popped from the open list (priority queue), which has the lowest f-score. shortestDistanceFound is the actual distance of the shortest path found so far. But how do I exclude the previously found paths from future searches? Because if I do the search again, it will obviously find the same path. Do I reset the closed list? I need to modify something, but I don't know what it is I need to change. The paper lacks pseudocode, so that would be helpful.

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  • Alternative, more efficient scraping method for a noncoder, than Google doc's importxml and xpath?

    - by binarybunny
    I've searched throughout the net for a simple solution, but it seems everyone has their own unique method (coding language) of achieving this. I'm only just beginning to learn Linux, and my coding skills are thoroughly lacking (non-existent). I love the simplicity of using importxml and xpath, but copying and pasting values after reaching the spreadsheet limit of 50 is getting old. Now that I've seen the light, I would really just like to know of a simple, yet scalable solution to get more data into more spreadsheets/databases. Before I really start getting my hands dirty, I would love to know some of the ways you guys go about accomplishing this?

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  • Are Get-Set methods a violation of Encapsulation?

    - by Dipan Mehta
    In an Object oriented framework, one believes there must be strict encapsulation. Hence, internal variables are not to be exposed to outside applications. But in many codebases, we see tons of get/set methods which essentially open a formal window to modify internal variables that were originally intended to be strictly prohibited. Isn't it a clear violation of encapsulation? How broadly such a practice is seen and what to do about it? EDIT: I have seen some discussions where there are two opinions in extreme: on one hand people believe that because get/set interface is used to modify any parameter, it does qualifies not be violating encapsulation. On the other hand, there are people who believe it is does violate. Here is my point. Take a case of UDP server, with methods - get_URL(), set_URL(). The URL (to listen to) property is quite a parameter that application needs to be supplied and modified. However, in the same case, if the property like get_byte_buffer_length() and set_byte_buffer_length(), clearly points to values which are quite internal. Won't it imply that it does violate the encapsulation? In fact, even get_byte_buffer_length() which otherwise doesn't modify the object, still misses the point of encapsulation, because, certainly there is an App which knows i have an internal buffer! Tomorrow, if the internal buffer is replaced by something like a *packet_list* the method goes dysfunctional. Is there a universal yes/no towards get set method? Is there any strong guideline that tell programmers (specially the junior ones) as to when does it violate encapsulation and when does it not?

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  • NHibernate Pitfalls: Loading Foreign Key Properties

    - by Ricardo Peres
    This is part of a series of posts about NHibernate Pitfalls. See the entire collection here. When saving a new entity that has references to other entities (one to one, many to one), one has two options for setting their values: Load each of these references by calling ISession.Get and passing the foreign key; Load a proxy instead, by calling ISession.Load with the foreign key. So, what is the difference? Well, ISession.Get goes to the database and tries to retrieve the record with the given key, returning null if no record is found. ISession.Load, on the other hand, just returns a proxy to that record, without going to the database. This turns out to be a better option, because we really don’t need to retrieve the record – and all of its non-lazy properties and collections -, we just need its key. An example: 1: //going to the database 2: OrderDetail od = new OrderDetail(); 3: od.Product = session.Get<Product>(1); //a product is retrieved from the database 4: od.Order = session.Get<Order>(2); //an order is retrieved from the database 5:  6: session.Save(od); 7:  8: //creating in-memory proxies 9: OrderDetail od = new OrderDetail(); 10: od.Product = session.Load<Product>(1); //a proxy to a product is created 11: od.Order = session.Load<Order>(2); //a proxy to an order is created 12:  13: session.Save(od); So, if you just need to set a foreign key, use ISession.Load instead of ISession.Get.

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  • Why is TDD not working here?

    - by TobiMcNamobi
    I want to write a class A that has a method calculate(<params>). That method should calculate a value using database data. So I wrote a class Test_A for unit testing (TDD). The database access is done using another class which I have mocked with a class, let's call it Accessor_Mockup. Now, the TDD cycle requires me to add a test that fails and make the simplest changes to A so that the test passes. So I add data to Accessor_Mockup and call A.calculate with appropriate parameters. But why should A use the accessor class at all? It would be simpler (!) if the class just "knows" the values it could retrieve from the database. For every test I write I could introduce such a new value (or an if-branch or whatever). But wait ... TDD is more. There is the refactoring part. But that sounds to me like "OK, I can do this all with a big if-elseif construct. I could refactor it using a new class ... but instead I make use of the DB accessor and do this in a totally different way. The code will not necessarily look better afterwards but I know I WANT to use the database".

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  • Find The Bug

    - by Alois Kraus
    What does this code print and why?             HashSet<int> set = new HashSet<int>();             int[] data = new int[] { 1, 2, 1, 2 };             var unique = from i in data                          where set.Add(i)                          select i;   // Compiles to: var unique = Enumerable.Where(data, (i) => set.Add(i));             foreach (var i in unique)             {                 Console.WriteLine("First: {0}", i);             }               foreach (var i in unique)             {                 Console.WriteLine("Second: {0}", i);             }   The output is: First: 1 First: 2 Why is there no output of the second loop? The reason is that LINQ does not cache the results of the collection but it does recalculate the contents for every new enumeration again. Since I have used state (the Hashset does decide which entries are part of the output) I do arrive with an empty sequence since Add of the Hashset will return false for all values I have already passed in leaving nothing to return a second time. The solution is quite simple: Use the Distinct extension method or cache the results by calling .ToList() or ToArray() for the result of the LINQ query. Lession Learned: Do never forget to think about state in Where clauses!

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  • Two-state script monitor not auto-resolving in SCOM

    - by DeliriumTremens
    This script runs, and if it returns 'erro' an alert is generated in SCOM. The alert is set to resolve when the monitor returns to healthy state. I have tested the script with cscript and it returns the correct values in each state. I'm baffled as to why it generates an alert on 'erro' but will not auto-resolve on 'ok': Option Explicit On Error Resume Next Dim objFSO Dim TargetFile Dim objFile Dim oAPI, oBag Dim StateDataType Dim FileSize Set oAPI = CreateObject("MOM.ScriptAPI") Set oBag = oAPI.CreatePropertyBag() TargetFile = "\\server\share\file.zip" Set objFSO = CreateObject("scripting.filesystemobject") Set objFile = objFSO.GetFile(TargetFile) FileSize = objFile.Size / 1024 If FileSize < 140000 Then Call oBag.AddValue("State", "erro") Else Call oBag.AddValue("State", "ok") End If Call oAPI.AddItem(oBag) Call oAPI.Return(oBag) Unhealthy expression: Property[@Name='State'] Equals erro Health expression: Property[@Name='State'] Equals ok If anyone can shed some light onto what I might be missing, that would be great!

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  • SQL SERVER – DMV sys.dm_exec_describe_first_result_set_for_object – Describes the First Result Metadata for the Module

    - by pinaldave
    Here is another interesting follow up blog post of SQL SERVER – sp_describe_first_result_set New System Stored Procedure in SQL Server 2012. While I was writing earlier blog post I had come across DMV sys.dm_exec_describe_first_result_set_for_object as well. I found that SQL Server 2012 is providing all this quick and new features which quite often we miss  to learn it and when in future someone demonstrates the same to us, we express our surprise on the subject. DMV sys.dm_exec_describe_first_result_set_for_object returns result set which describes the columns used in the stored procedure. Here is the quick example. Let us first create stored procedure. USE [AdventureWorks] GO ALTER PROCEDURE [dbo].[CompSP] AS SELECT [DepartmentID] id ,[Name] n ,[GroupName] gn FROM [HumanResources].[Department] GO Now let us run following two DMV which gives us meta data description of the stored procedure passed as a parameter. Option1: Pass second parameter @include_browse_information as a 0. SELECT * FROM sys.dm_exec_describe_first_result_set_for_object ( OBJECT_ID('[dbo].[CompSP]'),0) AS Table1 GO Option2: Pass second parameter @include_browse_information as a 1. SELECT * FROM sys.dm_exec_describe_first_result_set_for_object ( OBJECT_ID('[dbo].[CompSP]'),1) AS Table1 GO Here is the result of Option1 and Option2. If you see the result, there is absolutely no difference between the results. Both of the resultset are returning column names which are aliased in the stored procedure. Let us scroll on the right side and you will notice that there is clear difference in some columns. You will see in second resultset source_database, Source_schema as well few other columns are reporting original table instead of NULL values. When @include_browse_information result is set to 1 it will provide the columns details of the underlying table. I have just discovered this DMV, I have yet to use it in production code and find out where exactly I will use this DMV. Do you have any idea? Does any thing comes up to your mind where this DMV can be helpful. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL DMV, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • Latency in Sending and Receiving Files From Amazon EC2 - Justification

    - by Adroidist
    I am facing a huge delay while uploading and downloading files from my Windows Amazon EC2 server to my android device. It takes around 50 seconds to upload then download 500 Kbytes image. My location is in asia and the server is is US-East. I pinged the server from my android and obtained values around 500 ms for RTT. Is this normal? How is this explained? I tried this website: http://cloudharmony.com/speedtest/run and obtained that downloading 270 Kbytes file takes around 20 seconds. How is this delay justified?

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  • Easiest way to open CSV with commas in Excel

    - by Borek
    CSV files are automatically associated with Excel but when I open them, all the rows are basically in the first column, like this: It's probably because when Excel thinks "comma-separated values", it actually searches for some other delimiter (I think it's semicolon but it's not important). Now when I have already opened this file in Excel, is there a button or something to tell it "reopen this file and use comma as a delimiter"? I know I can import the data into a new worksheet etc. but I'm asking specifically for a help with situation where I already have a CSV file with commas in it and I want to open it in Excel without creating new workbook or transforming the original file.

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  • Inside the Concurrent Collections: ConcurrentDictionary

    - by Simon Cooper
    Using locks to implement a thread-safe collection is rather like using a sledgehammer - unsubtle, easy to understand, and tends to make any other tool redundant. Unlike the previous two collections I looked at, ConcurrentStack and ConcurrentQueue, ConcurrentDictionary uses locks quite heavily. However, it is careful to wield locks only where necessary to ensure that concurrency is maximised. This will, by necessity, be a higher-level look than my other posts in this series, as there is quite a lot of code and logic in ConcurrentDictionary. Therefore, I do recommend that you have ConcurrentDictionary open in a decompiler to have a look at all the details that I skip over. The problem with locks There's several things to bear in mind when using locks, as encapsulated by the lock keyword in C# and the System.Threading.Monitor class in .NET (if you're unsure as to what lock does in C#, I briefly covered it in my first post in the series): Locks block threads The most obvious problem is that threads waiting on a lock can't do any work at all. No preparatory work, no 'optimistic' work like in ConcurrentQueue and ConcurrentStack, nothing. It sits there, waiting to be unblocked. This is bad if you're trying to maximise concurrency. Locks are slow Whereas most of the methods on the Interlocked class can be compiled down to a single CPU instruction, ensuring atomicity at the hardware level, taking out a lock requires some heavy lifting by the CLR and the operating system. There's quite a bit of work required to take out a lock, block other threads, and wake them up again. If locks are used heavily, this impacts performance. Deadlocks When using locks there's always the possibility of a deadlock - two threads, each holding a lock, each trying to aquire the other's lock. Fortunately, this can be avoided with careful programming and structured lock-taking, as we'll see. So, it's important to minimise where locks are used to maximise the concurrency and performance of the collection. Implementation As you might expect, ConcurrentDictionary is similar in basic implementation to the non-concurrent Dictionary, which I studied in a previous post. I'll be using some concepts introduced there, so I recommend you have a quick read of it. So, if you were implementing a thread-safe dictionary, what would you do? The naive implementation is to simply have a single lock around all methods accessing the dictionary. This would work, but doesn't allow much concurrency. Fortunately, the bucketing used by Dictionary allows a simple but effective improvement to this - one lock per bucket. This allows different threads modifying different buckets to do so in parallel. Any thread making changes to the contents of a bucket takes the lock for that bucket, ensuring those changes are thread-safe. The method that maps each bucket to a lock is the GetBucketAndLockNo method: private void GetBucketAndLockNo( int hashcode, out int bucketNo, out int lockNo, int bucketCount) { // the bucket number is the hashcode (without the initial sign bit) // modulo the number of buckets bucketNo = (hashcode & 0x7fffffff) % bucketCount; // and the lock number is the bucket number modulo the number of locks lockNo = bucketNo % m_locks.Length; } However, this does require some changes to how the buckets are implemented. The 'implicit' linked list within a single backing array used by the non-concurrent Dictionary adds a dependency between separate buckets, as every bucket uses the same backing array. Instead, ConcurrentDictionary uses a strict linked list on each bucket: This ensures that each bucket is entirely separate from all other buckets; adding or removing an item from a bucket is independent to any changes to other buckets. Modifying the dictionary All the operations on the dictionary follow the same basic pattern: void AlterBucket(TKey key, ...) { int bucketNo, lockNo; 1: GetBucketAndLockNo( key.GetHashCode(), out bucketNo, out lockNo, m_buckets.Length); 2: lock (m_locks[lockNo]) { 3: Node headNode = m_buckets[bucketNo]; 4: Mutate the node linked list as appropriate } } For example, when adding another entry to the dictionary, you would iterate through the linked list to check whether the key exists already, and add the new entry as the head node. When removing items, you would find the entry to remove (if it exists), and remove the node from the linked list. Adding, updating, and removing items all follow this pattern. Performance issues There is a problem we have to address at this point. If the number of buckets in the dictionary is fixed in the constructor, then the performance will degrade from O(1) to O(n) when a large number of items are added to the dictionary. As more and more items get added to the linked lists in each bucket, the lookup operations will spend most of their time traversing a linear linked list. To fix this, the buckets array has to be resized once the number of items in each bucket has gone over a certain limit. (In ConcurrentDictionary this limit is when the size of the largest bucket is greater than the number of buckets for each lock. This check is done at the end of the TryAddInternal method.) Resizing the bucket array and re-hashing everything affects every bucket in the collection. Therefore, this operation needs to take out every lock in the collection. Taking out mutiple locks at once inevitably summons the spectre of the deadlock; two threads each hold a lock, and each trying to acquire the other lock. How can we eliminate this? Simple - ensure that threads never try to 'swap' locks in this fashion. When taking out multiple locks, always take them out in the same order, and always take out all the locks you need before starting to release them. In ConcurrentDictionary, this is controlled by the AcquireLocks, AcquireAllLocks and ReleaseLocks methods. Locks are always taken out and released in the order they are in the m_locks array, and locks are all released right at the end of the method in a finally block. At this point, it's worth pointing out that the locks array is never re-assigned, even when the buckets array is increased in size. The number of locks is fixed in the constructor by the concurrencyLevel parameter. This simplifies programming the locks; you don't have to check if the locks array has changed or been re-assigned before taking out a lock object. And you can be sure that when a thread takes out a lock, another thread isn't going to re-assign the lock array. This would create a new series of lock objects, thus allowing another thread to ignore the existing locks (and any threads controlling them), breaking thread-safety. Consequences of growing the array Just because we're using locks doesn't mean that race conditions aren't a problem. We can see this by looking at the GrowTable method. The operation of this method can be boiled down to: private void GrowTable(Node[] buckets) { try { 1: Acquire first lock in the locks array // this causes any other thread trying to take out // all the locks to block because the first lock in the array // is always the one taken out first // check if another thread has already resized the buckets array // while we were waiting to acquire the first lock 2: if (buckets != m_buckets) return; 3: Calculate the new size of the backing array 4: Node[] array = new array[size]; 5: Acquire all the remaining locks 6: Re-hash the contents of the existing buckets into array 7: m_buckets = array; } finally { 8: Release all locks } } As you can see, there's already a check for a race condition at step 2, for the case when the GrowTable method is called twice in quick succession on two separate threads. One will successfully resize the buckets array (blocking the second in the meantime), when the second thread is unblocked it'll see that the array has already been resized & exit without doing anything. There is another case we need to consider; looking back at the AlterBucket method above, consider the following situation: Thread 1 calls AlterBucket; step 1 is executed to get the bucket and lock numbers. Thread 2 calls GrowTable and executes steps 1-5; thread 1 is blocked when it tries to take out the lock in step 2. Thread 2 re-hashes everything, re-assigns the buckets array, and releases all the locks (steps 6-8). Thread 1 is unblocked and continues executing, but the calculated bucket and lock numbers are no longer valid. Between calculating the correct bucket and lock number and taking out the lock, another thread has changed where everything is. Not exactly thread-safe. Well, a similar problem was solved in ConcurrentStack and ConcurrentQueue by storing a local copy of the state, doing the necessary calculations, then checking if that state is still valid. We can use a similar idea here: void AlterBucket(TKey key, ...) { while (true) { Node[] buckets = m_buckets; int bucketNo, lockNo; GetBucketAndLockNo( key.GetHashCode(), out bucketNo, out lockNo, buckets.Length); lock (m_locks[lockNo]) { // if the state has changed, go back to the start if (buckets != m_buckets) continue; Node headNode = m_buckets[bucketNo]; Mutate the node linked list as appropriate } break; } } TryGetValue and GetEnumerator And so, finally, we get onto TryGetValue and GetEnumerator. I've left these to the end because, well, they don't actually use any locks. How can this be? Whenever you change a bucket, you need to take out the corresponding lock, yes? Indeed you do. However, it is important to note that TryGetValue and GetEnumerator don't actually change anything. Just as immutable objects are, by definition, thread-safe, read-only operations don't need to take out a lock because they don't change anything. All lockless methods can happily iterate through the buckets and linked lists without worrying about locking anything. However, this does put restrictions on how the other methods operate. Because there could be another thread in the middle of reading the dictionary at any time (even if a lock is taken out), the dictionary has to be in a valid state at all times. Every change to state has to be made visible to other threads in a single atomic operation (all relevant variables are marked volatile to help with this). This restriction ensures that whatever the reading threads are doing, they never read the dictionary in an invalid state (eg items that should be in the collection temporarily removed from the linked list, or reading a node that has had it's key & value removed before the node itself has been removed from the linked list). Fortunately, all the operations needed to change the dictionary can be done in that way. Bucket resizes are made visible when the new array is assigned back to the m_buckets variable. Any additions or modifications to a node are done by creating a new node, then splicing it into the existing list using a single variable assignment. Node removals are simply done by re-assigning the node's m_next pointer. Because the dictionary can be changed by another thread during execution of the lockless methods, the GetEnumerator method is liable to return dirty reads - changes made to the dictionary after GetEnumerator was called, but before the enumeration got to that point in the dictionary. It's worth listing at this point which methods are lockless, and which take out all the locks in the dictionary to ensure they get a consistent view of the dictionary: Lockless: TryGetValue GetEnumerator The indexer getter ContainsKey Takes out every lock (lockfull?): Count IsEmpty Keys Values CopyTo ToArray Concurrent principles That covers the overall implementation of ConcurrentDictionary. I haven't even begun to scratch the surface of this sophisticated collection. That I leave to you. However, we've looked at enough to be able to extract some useful principles for concurrent programming: Partitioning When using locks, the work is partitioned into independant chunks, each with its own lock. Each partition can then be modified concurrently to other partitions. Ordered lock-taking When a method does need to control the entire collection, locks are taken and released in a fixed order to prevent deadlocks. Lockless reads Read operations that don't care about dirty reads don't take out any lock; the rest of the collection is implemented so that any reading thread always has a consistent view of the collection. That leads us to the final collection in this little series - ConcurrentBag. Lacking a non-concurrent analogy, it is quite different to any other collection in the class libraries. Prepare your thinking hats!

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  • SQL SERVER – Difference between DATABASEPROPERTY and DATABASEPROPERTYEX

    - by pinaldave
    Earlier I asked a simple question on Facebook regarding difference between DATABASEPROPERTY and DATABASEPROPERTYEX in SQL Server. You can view the original conversation there over here. The conversion immediately became very interesting and lots of healthy discussion happened on facebook page. The best part of having conversation on facebook page is the comfort it provides and leaner commenting interface. Question Question from SQLAuthority.com: What is the difference between DATABASEPROPERTY and DATABASEPROPERTYEX in SQL Server? Answer Answer from Rakesh Kumar: DATABASEPROPERTY is supported for backward compatibility but does not provide information about the properties added in this release. Also, many properties supported by DATABASEPROPERTY have been replaced by new properties in DATABASEPROPERTYEX.- source (MSDN). Answer from Alphonso Jones: The only real difference I can see is one, the number of properties contained and the other is that EX returns a sql_variant while DATABASEPROPERTY returns only int. Answer from Ambati Venkatasiva: Both are system meta data functions. DATABASEPROPERTYEX Returns the current setting of the specified database option. DATABASEPROPERTYEX returns the sq-varient value and DATABASEPROPERTY returns integer value. Answer from Rama Sankar Molleti:  Here is the best example about databasepropertyex SELECT DATABASEPROPERTYEX('dbname', 'Collation') Result SQL_1xCompat_CP850_CI_AS Whereas with databaseproperty it retuns nothing as the return type for this is integer. Sql_variant datatype stores values of various sql server supported datatypes except text, ntext, image and timestamp. Answer from Alok Seth:  SELECT DATABASEPROPERTYEX('AdventureWorks', 'Status') DatabaseStatus_DATABASEPROPERTYEX GO --Result - ONLINE SELECT DATABASEPROPERTY('AdventureWorks', 'Status') DatabaseStatus_DATABASEPROPERTY GO --Result - NULL Summary Use DATABASEPROPERTYEX as it is the only function supported in future version as well it returns status of various database properties which does not exists with DATABASEPROPERTY. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • Changing an MSSQL clustered index field from containing "random" GUIDs to sequential GUIDs - how wil

    - by Eyvind
    We have an MSSQL database in which all the primary keys are GUIDs (uniqueidentifiers). The GUIDs are produced on the client (in C#), and we are considering changing the client to generate sequential (comb) GUIDs instead of just using Guid.NewGuid(), to improve db performance. If we do this, how will this affect installations that already have data with "random" GUIDs as clustered PKs? Can anything be done (short of changing all the PK values) to rebuild the indexes to avoid further fragmentation and bad insert performance? Please give explicit and detailed answers if you can; I am a C# developer at heart and not all too familiar with all the intricacies of SQL Server. Thanks!

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  • Help, broken Gsettings

    - by Rene
    I was trying to disable the global menu as per http://ubuntuhandbook.org/index.php/2013/07/disable-global-menu-on-ubuntu-13-10-saucy/#comment-8612, but while it didn't change anything, after running the autoremove command unity-tweak-tool broke. Obviously my first reaction was to re-install the removed package but it remains broken. TBH I don't know if it is even related or just a coincidence. When I start it from the launcher it just blinks and disappear. When I start it from terminal I get this error: $ gnome-tweak-tool WARNING : Shell not installed or running WARNING : Error detecting shell Traceback (most recent call last): File "/usr/lib/python2.7/dist-packages/gtweak/tweaks/tweak_shell_extensions.py", line 199, in __init__ raise Exception("Shell not running or DBus service not available") Exception: Shell not running or DBus service not available INFO : GSettings missing key org.gnome.nautilus.desktop (key computer-icon-visible) WARNING : Shell not running None INFO : GSettings missing key org.gnome.mutter (key workspaces-only-on-primary) Segmentation fault (core dumped) I had a look with dconf-editor if I could just add the missing key, but apparently keys aren't meant to be added "by hand". So how can I fix this? I'd rather prefer not having to reinstall everything. Which package is broken, can I just reinstall that? EDIT: I found by being root gnome-tweak-tool no longer crashed so possibly a permission issue somewhere. I don't know that I changed any permissions. Another related problem, actually the reason I noticed the problem at all, is that unity-tweak-tool seem no longer to want to save the values edited. I normally just have the Unity launcher on the primary display but wanted to check what it was like having it on both. I didn't like it so I went into unity-tweak-tool to set it back - but regardless how many time I tick "only primary display" it never changes anything. What does the Unity-tweak-tool actually change and can I do this directly somehow?

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  • javascript fixed timestep gameloop with requestanimation frame

    - by coffeecup
    hello i just started to read through several articles, including http://gafferongames.com/game-physics/fix-your-timestep/ ...://gamedev.stackexchange.com/questions/1589/fixed-time-step-vs-variable-time-step/ ...//dewitters.koonsolo.com/gameloop.html ...://nokarma.org/2011/02/02/javascript-game-development-the-game-loop/index.html my understanding of this is that i need the currentTime and the timeStep size and integrate all states to the next state the time which is left is then passed into the render function to do interpolation i tried to implement glenn fiedlers "the final touch", whats troubling me is that each FrameTime is about 15 (ms) and the update loop runs at about 1500 fps which seems a little bit off? heres my code this.t = 0 this.dt = 0.01 this.currTime = new Date().getTime() this.accumulator = 0.0 this.animate() animate: function(){ var newTime = new Date().getTime() , frameTime = newTime - this.currTime , alpha if ( frameTime > 0.25 ) frameTime = 0.25 this.currTime = newTime this.accumulator += frameTime while (this.accumulator >= this.dt ) { this.prev_state = this.curr_state this.update(this.t,this.dt) this.t += this.dt this.accumulator -= this.dt } alpha = this.accumulator / this.dt this.render( this.t, this.dt, alpha) requestAnimationFrame( this.animate ) } also i would like to know, are there differences between glenn fiedlers implementation and the last solution presented here ? gameloop1 gameloop2 [ sorry couldnt post more than 2 links.. ] edit : i looked into it again and adjusted the values this.currTime = new Date().getTime() this.accumulator = 0 this.p_t = 0 this.p_step = 1000/100 this.animate() animate: function(){ var newTime = new Date().getTime() , frameTime = newTime - this.currTime , alpha if(frameTime > 25) frameTime = 25 this.currTime = newTime this.accumulator += frameTime while(this.accumulator >= this.p_step){ // prevstate = currState this.update() this.p_t+=this.p_step this.accumulator -= this.p_step } alpha = this.accumulator / this.p_step this.render(alpha) requestAnimationFrame( this.animate ) now i can set the physics update rate, render runs at 60 fps and physics update at 100 fps, maybe someone could confirm this because its the first time i'm playing around with game development :-)

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  • apply seach criteria to whole cells

    - by Tom
    I am trying to use MATCH() and/or LOOKUP() in LibreOffice Calc. I have the "Search criteria = and < must apply to whole cells" and the "Enable regular expressions in formulas" options selected. The item I am looking for is a multi word string. How do I provide a search criteria as a cell reference (E3) in to LOOKUP(E3, B1:B20, C1:C20) and have it match the value in B1:B20 EXACTLY? Right now it is matching partial strings rather than matching the cell values exactly.

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  • Smart defaults [SSDT]

    - by jamiet
    I’ve just discovered a new, somewhat hidden, feature in SSDT that I didn’t know about and figured it would be worth highlighting here because I’ll bet not many others know it either; the feature is called Smart Defaults. It gets around the problem of adding a NOT NULLable column to an existing table that has got data in it – previous to SSDT you would need to define a DEFAULT constraint however it does feel rather cumbersome to create an object purely for the purpose of pushing through a deployment – that’s the situation that Smart Defaults is meant to alleviate. The Smart Defaults option exists in the advanced section of a Publish Profile file: The description of the setting is “Automatically provides a default value when updating a table that contains data with a column that does not allow null values”, in other words checking that option will cause SSDT to insert an arbitrary default value into your newly created NON NULLable column. In case you’re wondering how it does it, here’s how: SSDT creates a DEFAULT CONSTRAINT at the same time as the column is created and then immediately removes that constraint: ALTER TABLE [dbo].[T1]    ADD [C1] INT NOT NULL,         CONSTRAINT [SD_T1_1df7a5f76cf44bb593506d05ff9a1e2b] DEFAULT 0 FOR [C1];ALTER TABLE [dbo].[T1] DROP CONSTRAINT [SD_T1_1df7a5f76cf44bb593506d05ff9a1e2b]; You can then update the value as appropriate in a Post-Deployment script. Pretty cool! On the downside, you can only specify this option for the whole project, not for an individual table or even an individual column – I’m not sure that I’d want to turn this on for an entire project as it could hide problems that a failed deployment would highlight, in other words smart defaults could be seen to be “papering over the cracks”. If you think that should be improved go and vote (and leave a comment) at [SSDT] Allow us to specify Smart defaults per table or even per column. @Jamiet

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  • Could not establish a secure connection to server with safari

    - by pharno
    Safari tells me that it couldnt open the page, because it couldnt establish a secure connection to the server. However, other browsers (opera, firefox) can open the page. Also, theres nothing in the apache error log. The certificate is selfsigned, and uses standart values. (seen here: http://www.knaupes.net/tutorial-ssl-zertifikat-selbst-erstellen-und-signieren/ ) ssl config: SSLEngine on #SSLInsecureRenegotiation on SSLCertificateFile /home/gemeinde/certs/selfsigned/gemeinde.crt SSLCertificateKeyFile /home/gemeinde/certs/selfsigned/gemeinde.key #SSLCACertificateFile /home/gemeinde/certs/Platinum_G2.pem #SSLOptions +StdEnvVars <Location "/"> SSLOptions +StdEnvVars +OptRenegotiate SSLVerifyClient optional SSLVerifyDepth 10 </Location>

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  • SQL SERVER – Difference between COUNT(DISTINCT) vs COUNT(ALL)

    - by pinaldave
    This blog post is written in response to the T-SQL Tuesday hosted by Jes Schultz Borland. Earlier today, I was presenting a 45-minute session at the Community College about “The Beginning SQL Server Database”. One of the students asked me the following question. What is the difference between COUNT(DISTINCT) vs COUNT(ALL)? I found this question from the student very interesting. He seems to have read the documentation (Book Online) and was then asking me this question. I always carry laptop which has SQL Server installed. I quickly opened it and ran the following script. After looking at the result, I think it was clear to everybody. Here is the script: SELECT COUNT([Title]) Value FROM [AdventureWorks].[Person].[Contact] GO SELECT COUNT(ALL [Title]) ALLValue FROM [AdventureWorks].[Person].[Contact] GO SELECT COUNT(DISTINCT [Title]) DistinctValue FROM [AdventureWorks].[Person].[Contact] GO The above script will give me the following results. You can clearly notice from the result set that COUNT (ALL ColumnName) is the same as COUNT(ColumnName). The reality is that the “ALL” is actually  the default option and it needs not to be specified. The ALL keyword includes all the non-NULL values. I know this is very simple and may be it does not change how we work; however looking at the whole angle, I really enjoyed the question. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, SQLAuthority News, T SQL, Technology

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  • Where to set permissions to all server for logon trigger on sql server 2005

    - by Jay
    I need to keep track of the last login time for each user in our SQL Server 2005 database. I created a trigger like this: CREATE TRIGGER LogonTimeStamp ON ALL SERVER FOR LOGON AS BEGIN IF EXISTS (SELECT * FROM miscdb..user_last_login WHERE user_id = SYSTEM_USER) UPDATE miscdb..user_last_login SET last_login = GETDATE() WHERE user_id = SYSTEM_USER ELSE INSERT INTO miscdb..user_last_login (user_id,last_login) VALUES (SYSTEM_USER,GETDATE()) END; go This trigger works for servers that are system admins but it won't allow regular users to login. I have granted public select,insert and update to the table but that doesn't seem to be the issue. Is there a way to set permissions on the trigger? Is there something else I am missing? Thanks

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  • Retrieving a specific value from “df -h” using shell

    - by diegodias
    When I use df -h, I get the following output: Filesystem Size Used Avail Use% Mounted on /dev/mapper/VolGroup00-LogVol00 59G 2.2G 54G 4% / /dev/sda1 122M 38M 78M 33% /boot tmpfs 1.1G 0 1.1G 0% /dev/shm 10.10.0.105:/somepath 11T 8.4T 2.1T 81% /storage4 10.11.0.101:/somepath 15T 8.9T 5.9T 61% /storage1 /dev/mapper/patha 5.0T 255G 4.8T 5% /storage5_vol0 /dev/mapper/pathb 5.0T 195G 4.9T 4% /storage5_vol1 /dev/mapper/pathc 5.0T 608G 4.5T 12% /storage5_vol2 I want to write a script that gets the value of Avail column on a specific storage. I used to use df -k /storage_name | tail -1 | awk '{print $3}' But the FileSystem column can have a value or not .. which would change the variable of my script from $3 to $4. How can I get the Avail on a single command line even if there are no values on the previous columns?

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  • Excel 2007 Conditional Formatting is not properly using custom formula provided

    - by Charles
    In Excel 2007, I want to conditionally color a row if it is odd numbered and then vary the coloring depending on if a specific cell (in column E) in that row contains a number (green) or empty(red). E.g. if E15 has a value of 2 and E13 has no entry, I would expect row 15 to be green and row 13 to be red. My two formulas are: To color red: =IF((MOD(ROW(),2) = 1),NOT(ISNUMBER(INDIRECT("$E$"&ROW()))), FALSE) To color green: =IF((MOD(ROW(),2) = 1),ISNUMBER(INDIRECT("E"&ROW())), FALSE) If I paste these formulas into cells on the worksheet I get the expected values. For row 15 the "red" equation is false and the "green" equation is true. For Row 13 the "red" equation is true and the "green equation is false. However if I use these formulas in the conditional formating use formula feature, all of my rows are red, any thoughts?

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  • Syntax error in apc.ini: unexpected '='

    - by Ashley
    I installed APC on Ubuntu 10.04 and it seems to be working fine but I'm seeing this error in my Apache error.log: PHP: syntax error, unexpected '=' in /etc/php5/apache2/conf.d/apc.ini on line 2 The contents of the file are: cat /etc/php5/apache2/conf.d/apc.ini extension=apc.so apc.enabled="1" apc.shm_segments="1" apc.shm_size="192" apc.num_files_hint="1024" And I have also tried it without the quotes (") around the values and get the same error. I've looked at loads of the tutorials on installing APC that mention apc.ini and they all seem to use one of the two syntax formats I have tried. I'd appreciate any ideas. Update: This still causes it: cat /etc/php5/apache2/conf.d/apc.ini extension='apc.so' apc.enabled='1' apc.shm_segments='1' apc.shm_size='192' apc.num_files_hint='1024' I changed to: cat /etc/php5/apache2/conf.d/apc.ini extension=apc.so and it still happens (there's no line 2 in the file now!) I'm assuming a /etc/init.d/apache2 reload will be sufficient to read the new config, is that my mistake?

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  • Bash script not adding variables to session

    - by travega
    I have a bash script that I have added as a startup application. It does a bunch of exports and alias assignment. #! /bin/bash alias devhm='cd ${DEV_HOME}; ll'; alias wlhm='cd ${WL_HOME}; ll'; alias dirch='watch --interval=1 "ls -la"'; alias vols='watch --interval=1 "df -h"'; alias svn-update='svn update --depth infinity ./*'; alias mci="~/mci.sh"; alias vncserver="vncserver -geometry 1680x1050"; alias ..="cd .."; alias hist="history | grep "; export PROXY_HOST=proxy.my.setup; export PROXY_PORT=3128; export LD_LIBRARY_PATH=$LD_LIBRARY_PATH/usr/lib/oracle/12.1/client64/lib; export ORACLE_HOME=/usr/lib/oracle/12.1/client64; export TNS_ADMIN=${ORACLE_HOME}/network/admin; echo "DONE!"; But none of these values are available in my terminal sessions anymore. Even when I run the script straight into the terminal like so: ./setup.sh I see the "DONE!" prompt printed but no aliases or env variables are set. If I copy and paste the contents of the file into the terminal the aliases and env variables are set. I have tried adding a line to execute the script from .bashrc also but still no aliases or env variables set. Any ideas what might be going on here? Also could anyone suggest a better way to have these env variables/aliases added to every terminal session?

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  • Formalizing a requirements spec written in narrative English

    - by ProfK
    I have a fairly technical functionality requirements spec, expressed in English prose, produced by my project manager. It is structured as a collection of UI tabs, where the requirements for each tab are expressed as a lit of UI fields and a list of business rules for the tab. Most business rules are for UI fields on a tab, e.g: a) Must be alphanumeric, max length 20. b) Must be a dropdown, with values from table x. c) Is mandatory. d) Is mandatory under certain conditions, e.g. another field is just populated, or has a specific value. Then other business rules get a little more complex. The spec is for a job application, so the central business object (table) is the Applicant, and we have several other tables with one-to-many relationships with applicant, such as Degree, HighSchool, PreviousEmployer, Diploma, etc. e) One such complex rule says a status field can only be assigned a certain value if a many-side record exists in at least one of the many-side tables. E.g. the Applicant has at least one HighSchool or at least one Diploma record. I am looking for advice on how to codify these requirements into a more structured specification defined in terms of tables, fields, and relationships, especially for the conditional rules for fields and for the presence of related records. Any suggestions and advice will be most welcome, but I would be overjoyed if i could find an already defined system or structure for expressing things like this.

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