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  • Lock-Free, Wait-Free and Wait-freedom algorithms for non-blocking multi-thread synchronization.

    - by GJ
    In multi thread programming we can find different terms for data transfer synchronization between two or more threads/tasks. When exactly we can say that some algorithem is: 1)Lock-Free 2)Wait-Free 3)Wait-Freedom I understand what means Lock-free but when we can say that some synchronization algorithm is Wait-Free or Wait-Freedom? I have made some code (ring buffer) for multi-thread synchronization and it use Lock-Free methods but: 1) Algorithm predicts maximum execution time of this routine. 2) Therad which call this routine at beginning set unique reference, what mean that is inside of this routine. 3) Other threads which are calling the same routine check this reference and if is set than count the CPU tick count (measure time) of first involved thread. If that time is to long interrupt the current work of involved thread and overrides him job. 4) Thread which not finished job because was interrupted from task scheduler (is reposed) at the end check the reference if not belongs to him repeat the job again. So this algorithm is not really Lock-free but there is no memory lock in use, and other involved threads can wait (or not) certain time before overide the job of reposed thread. Added RingBuffer.InsertLeft function: function TgjRingBuffer.InsertLeft(const link: pointer): integer; var AtStartReference: cardinal; CPUTimeStamp : int64; CurrentLeft : pointer; CurrentReference: cardinal; NewLeft : PReferencedPtr; Reference : cardinal; label TryAgain; begin Reference := GetThreadId + 1; //Reference.bit0 := 1 with rbRingBuffer^ do begin TryAgain: //Set Left.Reference with respect to all other cores :) CPUTimeStamp := GetCPUTimeStamp + LoopTicks; AtStartReference := Left.Reference OR 1; //Reference.bit0 := 1 repeat CurrentReference := Left.Reference; until (CurrentReference AND 1 = 0)or (GetCPUTimeStamp - CPUTimeStamp > 0); //No threads present in ring buffer or current thread timeout if ((CurrentReference AND 1 <> 0) and (AtStartReference <> CurrentReference)) or not CAS32(CurrentReference, Reference, Left.Reference) then goto TryAgain; //Calculate RingBuffer NewLeft address CurrentLeft := Left.Link; NewLeft := pointer(cardinal(CurrentLeft) - SizeOf(TReferencedPtr)); if cardinal(NewLeft) < cardinal(@Buffer) then NewLeft := EndBuffer; //Calcolate distance result := integer(Right.Link) - Integer(NewLeft); //Check buffer full if result = 0 then //Clear Reference if task still own reference if CAS32(Reference, 0, Left.Reference) then Exit else goto TryAgain; //Set NewLeft.Reference NewLeft^.Reference := Reference; SFence; //Try to set link and try to exchange NewLeft and clear Reference if task own reference if (Reference <> Left.Reference) or not CAS64(NewLeft^.Link, Reference, link, Reference, NewLeft^) or not CAS64(CurrentLeft, Reference, NewLeft, 0, Left) then goto TryAgain; //Calcolate result if result < 0 then result := Length - integer(cardinal(not Result) div SizeOf(TReferencedPtr)) else result := cardinal(result) div SizeOf(TReferencedPtr); end; //with end; { TgjRingBuffer.InsertLeft } RingBuffer unit you can find here: RingBuffer, CAS functions: FockFreePrimitives, and test program: RingBufferFlowTest Thanks in advance, GJ

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  • How to get a non-XML output using JDOM XSLTransformer?

    - by Neil McF
    Hello, I have an XML file which I'd like to parse into a non-XML (text) file based on a XLST file. The code in both seem correct, and it works when testing manually, but I'm having a problem doing this programatically. I'm using JDOM's XSLTransformer class to apply the XSLT to the XML and it returns it in the format of a JDOM Document. The problem here is that I can't seem to access anything in the Document as it is not a proper XML file and I get a "java.lang.IllegalStateException: Root element not set" error. Is there a better way within Java to obtain a non-XML file as a result of XSLT?

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  • Advantage of using a static member function instead of an equivalent non-static member function?

    - by jonathanasdf
    I was wondering whether there's any advantages to using a static member function when there is a non-static equivalent. Will it result in faster execution (because of not having to care about all of the member variables), or maybe less use of memory (because of not being included in all instances)? Basically, the function I'm looking at is an utility function to rotate an integer array representing pixel colours an arbitrary number of degrees around an arbitrary centre point. It is placed in my abstract Bullet base class, since only the bullets will be using it and I didn't want the overhead of calling it in some utility class. It's a bit too long and used in every single derived bullet class, making it probably not a good idea to inline. How would you suggest I define this function? As a static member function of Bullet, of a non-static member function of Bullet, or maybe not as a member of Bullet but defined outside of the class in Bullet.h? What are the advantages and disadvantages of each?

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  • How to make Spring accept fluent (non-void) setters?

    - by Chris
    Hi, I have an API which I am turning into an internal DSL. As such, most methods in my PoJos return a reference to this so that I can chain methods together declaratively as such (syntactic sugar). myComponent .setID("MyId") .setProperty("One") .setProperty2("Two") .setAssociation(anotherComponent) .execute(); My API does not depend on Spring but I wish to make it 'Spring-Friendly' by being PoJo friendly with zero argument constructors, getters and setters. The problem is that Spring seems to not detect my setter methods when I have a non-void return type. The return type of this is very convenient when chaining together my commands so I don't want to destroy my programmatic API just be to compatible with Spring injection. Is there a setting in Spring to allow me to use non-void setters? Chris

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  • Allowing threads from python after calling a blocking i/o code in a python extension generated using

    - by SS
    I have written a python extension wrapping an existing C++ library live555 (wrapping RTSP client interface to be specific) in SWIG. The extension works when it is operated in a single thread, but as soon as I call the event loop function of the library, python interpreter never gets the control back. So if I create a scheduled task using threading.Timer right before calling the event loop, that task never gets executed once event loop starts. To fix this issue, I added Py_BEGIN_ALLOW_THREADS and Py_END_ALLOW_THREADS macros manually in the SWIG auto generated wrapper cxx file around every doEventLoop() function call. But now, I want to do the same (i.e. allow threads) when SWIG generates the code itself and not to change any code manually. Has anyone done something similar in SWIG? P.S. - I would also consider switching to any other framework (like SIP) to get this working. I selected SWIG over any other technology is because writing SWIG interface was really very easy and I just had to include the existing header files.

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  • Writing Device Drivers for Microcontrollers, where to define IO Port pins?

    - by volting
    I always seem to encounter this dilemma when writing low level code for MCU's. I never know where to declare pin definitions so as to make the code as reusable as possible. In this case Im writing a driver to interface an 8051 to a MCP4922 12bit serial DAC. Im unsure how/where I should declare the pin definitions for The CS(chip select) and LDAC(data latch) for the DAC. At the moment there declared in the header file for the driver. Iv done a lot of research trying to figure out the best approach but havent really found anything. Im basically want to know what the best practices... if there are some books worth reading or online information, examples etc, any recommendations would be welcome. Just a snippet of the driver so you get the idea /** @brief This function is used to write a 16bit data word to DAC B -12 data bit plus 4 configuration bits @param dac_data A 12bit word @param ip_buf_unbuf_select Input Buffered/unbuffered select bit. Buffered = 1; Unbuffered = 0 @param gain_select Output Gain Selection bit. 1 = 1x (VOUT = VREF * D/4096). 0 =2x (VOUT = 2 * VREF * D/4096) */ void MCP4922_DAC_B_TX_word(unsigned short int dac_data, bit ip_buf_unbuf_select, bit gain_select) { unsigned char low_byte=0, high_byte=0; CS = 0; /**Select the chip*/ high_byte |= ((0x01 << 7) | (0x01 << 4)); /**Set bit to select DAC A and Set SHDN bit high for DAC A active operation*/ if(ip_buf_unbuf_select) high_byte |= (0x01 << 6); if(gain_select) high_byte |= (0x01 << 5); high_byte |= ((dac_data >> 8) & 0x0F); low_byte |= dac_data; SPI_master_byte(high_byte); SPI_master_byte(low_byte); CS = 1; LDAC = 0; /**Latch the Data*/ LDAC = 1; }

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  • how to handle it if the management just keep on giving me spec after spec non-stop?

    - by Jian Lin
    As a programmer, I feel burnt out if the management give me spec after spec, day after day. I think I can code 6 hours a day very focused, but non-stop coding does burn me out a little, especially it is 1 year or 18 months non-stop. A mere 1 week or 2 week vacation per year isn't going to help much. Sometimes I want to take some time to learn new things, or just to take a break for a month so as to re-charge, like back in college when we have holidays for 1 month during winter or 2.5 months during summer. What do you think?

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  • How to implement blocking request-reply using Java concurrency primitives?

    - by Uri
    My system consists of a "proxy" class that receives "request" packets, marshals them and sends them over the network to a server, which unmarshals them, processes, and returns some "response packet". My "submit" method on the proxy side should block until a reply is received to the request (packets have ids for identification and referencing purposes) or until a timeout is reached. If I was building this in early versions of Java, I would likely implement in my proxy a collection of "pending messages ids", where I would submit a message, and wait() on the corresponding id (with a timeout). When a reply was received, the handling thread would notify() on the corresponding id. Is there a better way to achieve this using an existing library class, perhaps in java.util.concurrency? If I went with the solution described above, what is the correct way to deal with the potential race condition where a reply arrives before wait() is invoked?

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  • Java MapReduce read data

    - by Tatiana
    Hi I am having following map-reduce code by which I am trying to read records from my database. There's code: import java.io.*; import java.util.ArrayList; import java.util.List; import org.apache.hadoop.fs.*; import org.apache.hadoop.io.*; import org.apache.hadoop.mapred.*; import org.apache.hadoop.mapred.lib.db.DBConfiguration; import org.apache.hadoop.mapred.lib.db.DBInputFormat; import org.apache.hadoop.mapred.lib.db.DBWritable; import org.apache.hadoop.util.*; import org.apache.hadoop.conf.*; public class Connection extends Configured implements Tool { public int run(String[] args) throws IOException { JobConf conf = new JobConf(getConf(), Connection.class); conf.setInputFormat(DBInputFormat.class); DBConfiguration.configureDB(conf, "com.sun.java.util.jar.pack.Driver", "jdbc:postgresql://localhost:5432/polyclinic", "postgres", "12345"); String[] fields = { "name" }; DBInputFormat.setInput(conf, MyRecord.class, "doctors", null, null, fields); conf.setMapOutputKeyClass(LongWritable.class); conf.setMapOutputValueClass(MyRecord.class); conf.setOutputKeyClass(LongWritable.class); conf.setOutputValueClass(TextOutputFormat.class); TextOutputFormat.setOutputPath(conf, new Path(args[0])); JobClient.runJob(conf); return 0; } public static void main(String[] args) throws Exception { int exitCode = ToolRunner.run(new Connection(), args); System.exit(exitCode); } } Class Mapper: import java.io.IOException; import org.apache.hadoop.io.IntWritable; import org.apache.hadoop.io.LongWritable; import org.apache.hadoop.io.Text; import org.apache.hadoop.mapred.MapReduceBase; import org.apache.hadoop.mapred.Mapper; import org.apache.hadoop.mapred.OutputCollector; import org.apache.hadoop.mapred.Reporter; public class MyMapper extends MapReduceBase implements Mapper<LongWritable, MyRecord, Text, IntWritable> { public void map(LongWritable key, MyRecord val, OutputCollector<Text, IntWritable> output, Reporter reporter) throws IOException { output.collect(new Text(val.name), new IntWritable(1)); } } Class Record: import java.io.DataInput; import java.io.DataOutput; import java.io.IOException; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import org.apache.hadoop.io.Text; import org.apache.hadoop.io.Writable; import org.apache.hadoop.mapred.lib.db.DBWritable; class MyRecord implements Writable, DBWritable { String name; public void readFields(DataInput in) throws IOException { this.name = Text.readString(in); } public void readFields(ResultSet resultSet) throws SQLException { this.name = resultSet.getString(1); } public void write(DataOutput out) throws IOException { } public void write(PreparedStatement stmt) throws SQLException { } } After this I got error: WARN mapred.JobClient: No job jar file set. User classes may not be found. See JobConf(Class) or JobConf#setJar(String). Can you give me any suggestion how to solve this problem?

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  • SCJP Book, IO section: Is this a typo or is there a reason it would look like this?

    - by iamchuckb
    My question is about line 4, where the new PrintWriter is created with the constructor taking the FileWriter fw as a parameter. I don't understand the use of chaining the BufferedWriter bw to FileWriter if it isn't used later on in the actual writing. Can Java apply chaining in a way that bw still somehow affects the rest of the program? 16. try { 17. FileWriter fw = new FileWriter(test); 18. BufferedWriter bw = new BufferedWriter(fw, 1024); 19. PrintWriter out = new PrintWriter(fw); 20. out.println("<html><body><h1>"); 21. out.println(args[0]); 22. out.println("</h1></body></html>"); 23. out.close(); 24. bw.close(); 25. fw.close(); 26. }catch(IOException e) { 27. e.printStackTrace(); 28. } I think it is probably a typo and they meant to use bw as the parameter for PrintWriter out but like the title says, I'm new to this. Thanks to all in advance.

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  • How to get SimpleRpcClient.Call() to be a blocking call to achieve synchronous communication with RabbitMQ?

    - by Nick Josevski
    In the .NET version (2.4.1) of RabbitMQ the RabbitMQ.Client.MessagePatterns.SimpleRpcClient has a Call() method with these signatures: public virtual object[] Call(params object[] args); public virtual byte[] Call(byte[] body); public virtual byte[] Call(IBasicProperties requestProperties, byte[] body, out IBasicProperties replyProperties); The problem: With various attempts, the method still continues to not block where I expect it to, so it's unable ever handle the response. The Question: Am I missing something obvious in the setup of the SimpleRpcClient, or earlier with the IModel, IConnection, or even PublicationAddress? More Info: I've also tried various paramater configurations of the QueueDeclare() method too with no luck. string QueueDeclare(string queue, bool durable, bool exclusive, bool autoDelete, IDictionary arguments); Some more reference code of my setup of these: IConnection conn = new ConnectionFactory{Address = "127.0.0.1"}.CreateConnection()); using (IModel ch = conn.CreateModel()) { var client = new SimpleRpcClient(ch, queueName); var queueName = ch.QueueDeclare("t.qid", true, true, true, null); ch.QueueBind(queueName, "exch", "", null); //HERE: does not block? var replyMessageBytes = client.Call(prop, msgToSend, out replyProp); } Looking elsewhere: Or is it likely there's an issue in my "server side" code? With and without the use of BasicAck() it appears the client has already continued execution.

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  • Java/Groovy File IO Replacing an Image File with it's own Contents - Why Does This Work?

    - by jboyd
    I have some JPG files that need to be replaced at runtime with a JFIF standardized version of themselves (we are using a vendor that gives us JPG that do not have proper headers so they don't work in certain applications)... I am able to create a new file from the existing image, then get a buffered image from that file and write the contents right back into the file without having to delete it and it works... imageSrcFolder.eachFileMatch ( ~/.*\.jpg/, { BufferedImage bi = ImageIO.read( it ) ImageIO.write( bi, "jpg", it ) }); The question I have is why? Why doesn't the file end up doubled in size? Why don't I have to delete it first? Why am I able to take a file object to an existing file and then treat it as if it were a brand new one? It seems that what I consider to be a "file" is not what the File object in java actually is, or else this wouldn't work at all. My code does exactly what I want it to do, but I'm not convinced it always will... it just seems way too easy

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  • Call non-static method in server side(aspx.cs) from client side use javascript (aspx).....

    - by Pramulia
    how Call non-static method in server side(aspx.cs) from client side using javascript (aspx)....? As far as I know I can call static method in server side from client side... server side : [System.Web.Services.WebMethod] public static void method1() { } client side : <script language="JavaScript"> function keyUP() { PageMethods.method1(); } </script> <asp:ScriptManager ID="ScriptManager1" runat="server" EnablePageMethods="true"> </asp:ScriptManager> It works. Now how do I call non-static method from client side...?

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  • How can two threads access a common array of buffers with minimal blocking ? (c#)

    - by Jelly Amma
    Hello, I'm working on an image processing application where I have two threads on top of my main thread: 1 - CameraThread that captures images from the webcam and writes them into a buffer 2 - ImageProcessingThread that takes the latest image from that buffer for filtering. The reason why this is multithreaded is because speed is critical and I need to have CameraThread to keep grabbing pictures and making the latest capture ready to pick up by ImageProcessingThread while it's still processing the previous image. My problem is about finding a fast and thread-safe way to access that common buffer and I've figured that, ideally, it should be a triple buffer (image[3]) so that if ImageProcessingThread is slow, then CameraThread can keep on writing on the two other images and vice versa. What sort of locking mechanism would be the most appropriate for this to be thread-safe ? I looked at the lock statement but it seems like it would make a thread block-waiting for another one to be finished and that would be against the point of triple buffering. Thanks in advance for any idea or advice. J.

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  • C++ to python communication. Multiple io streams?

    - by Dennis Kempin
    A python program opens a new process of the C++ program and is reading the processes stdout. No problem so far. But is it possible to have multiple streams like this for communication? I can get two if I misuse stderr too, but not more. Easy way to hack this would be using temporary files. Is there something more elegant that does not need a detour to the filesystem? PS: *nix specific solutions are welcome too

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  • How could I catch an "Unicode non-character"-warning?

    - by sid_com
    How could I catch the "Unicode non-character 0xffff is illegal for interchange"-warning? #!/usr/bin/env perl use warnings; use 5.012; use Try::Tiny; use warnings FATAL => qw(all); my $character; try { $character = "\x{ffff}"; } catch { die "---------- caught error ----------\n"; }; say "something"; Output: # Unicode non-character 0xffff is illegal for interchange at ./perl1.pl line 11.

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  • How do I change the curosr during a jQuery synchronous browser blocking POST?

    - by Tommy
    $.ajax({ url: "/cgi-bin/stats.exe", method: "post", async: false, data: { refresh: "a41" } }); Using ajax post synchronously - "async: false". While it blocks the browser during the active request, what is the most efficient way to change the cursor to the hourglass or display a wait .gif? Perhaps set the cursor as it enters this function then change it back in the success or complete function? Any advice is appreciated. Thank You.

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  • Io exception: There is no process to read data written to a pipe.

    - by Srikanth
    I'm using Hibernate3.2+Websphere6.0+struts1.3.. After deploying ,application works fine. After some idle time ,i will get this type of error repeatedly,am not able to login at all. Im not using any connection pooling. i feel after idle time its not able to connect to the database again..if i restart the server everything works fine for some time...after that same story.. please help me out

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  • Capturing stdout from an imported module in wxpython and sending it to a textctrl, without blocking the GUI

    - by splafe
    There are alot of very similar questions to this but I can't find one that applies specifically to what I'm trying to do. I have a simulation (written in SimPy) that I'm writing a GUI for, the main output of the simulation is text - to the console from 'print' statements. Now, I thought the simplest way would be to create a seperate module GUI.py, and import my simulation program into it: import osi_model I want all the print statements to be captured by the GUI and appear inside a Textctrl, which there's countless examples of on here, along these lines: class MyFrame(wx.Frame): def __init__(self, *args, **kwds): <general frame initialisation stuff..> redir=RedirectText(self.txtCtrl_1) sys.stdout=redir class RedirectText: def __init__(self,aWxTextCtrl): self.out=aWxTextCtrl def write(self,string): self.out.WriteText(string) I am also starting my simulation from a 'Go' button: def go_btn_click(self, event): print 'GO' self.RT = threading.Thread(target=osi_model.RunThis()) self.RT.start() This all works fine, and the output from the simulation module is captured by the TextCtrl, except the GUI locks up and becomes unresponsive - I still need it to be accessible (at the very minimum to have a 'Stop' button). I'm not sure if this is a botched attempt at creating a new thread that I've done here, but I assume a new thread will be needed at some stage in this process. People suggest using wx.CallAfter, but I'm not sure how to go about this considering the imported module doesn't know about wx, and also I can't realistically go through the entire simulation architecture and change all the print statements to wx.CallAfter, and any attempt to capture the shell from inside the imported simulation program leads to the program crashing. Does anybody have any ideas about how I can best achieve this? So all I really need is for all console text to be captured by a TextCtrl while the GUI remains responsive, and all text is solely coming from an imported module. (Also, secondary question regarding a Stop button - is it bad form to just kill the simulation thread?). Thanks, Duncan

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  • Is it possible to get Logged in user Non Restricted token from a service on Vista?

    - by coolcake
    Hello All, I need to create a process with integrity level high, so that it can do all the administrative tasks. But the created process should run in the current logged in desktop i.e. it should not run in session 0. By default only administrators will log on to the console. The service should launch the process, as service is running in session 0 and system account. Can it any how get the non restricted token and use it in CreateProcessAsUser, so that the process created does have integrity level of high or system. Is it possible? One more thing is i should get the non restricted token with out prompting for user name or password of the logged in user. Thanks

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  • Trying to packetize TCP with non-blocking IO is hard! Am I doing something wrong?

    - by Ricket
    Oh how I wish TCP was packet-based like UDP is! But alas, that's not the case, so I'm trying to implement my own packet layer. Here's the chain of events so far (ignoring writing packets) Oh, and my Packets are very simply structured: two unsigned bytes for length, and then byte[length] data. (I can't imagine if they were any more complex, I'd be up to my ears in if statements!) Server is in an infinite loop, accepting connections and adding them to a list of Connections. PacketGatherer (another thread) uses a Selector to figure out which Connection.SocketChannels are ready for reading. It loops over the results and tells each Connection to read(). Each Connection has a partial IncomingPacket and a list of Packets which have been fully read and are waiting to be processed. On read(): Tell the partial IncomingPacket to read more data. (IncomingPacket.readData below) If it's done reading (IncomingPacket.complete()), make a Packet from it and stick the Packet into the list waiting to be processed and then replace it with a new IncomingPacket. There are a couple problems with this. First, only one packet is being read at a time. If the IncomingPacket needs only one more byte, then only one byte is read this pass. This can of course be fixed with a loop but it starts to get sorta complicated and I wonder if there is a better overall way. Second, the logic in IncomingPacket is a little bit crazy, to be able to read the two bytes for the length and then read the actual data. Here is the code, boiled down for quick & easy reading: int readBytes; // number of total bytes read so far byte length1, length2; // each byte in an unsigned short int (see getLength()) public int getLength() { // will be inaccurate if readBytes < 2 return (int)(length1 << 8 | length2); } public void readData(SocketChannel c) { if (readBytes < 2) { // we don't yet know the length of the actual data ByteBuffer lengthBuffer = ByteBuffer.allocate(2 - readBytes); numBytesRead = c.read(lengthBuffer); if(readBytes == 0) { if(numBytesRead >= 1) length1 = lengthBuffer.get(); if(numBytesRead == 2) length2 = lengthBuffer.get(); } else if(readBytes == 1) { if(numBytesRead == 1) length2 = lengthBuffer.get(); } readBytes += numBytesRead; } if(readBytes >= 2) { // then we know we have the entire length variable // lazily-instantiate data buffers based on getLength() // read into data buffers, increment readBytes // (does not read more than the amount of this packet, so it does not // need to handle overflow into the next packet's data) } } public boolean complete() { return (readBytes > 2 && readBytes == getLength()+2); } Basically I need feedback on my code. Please suggest any improvements. Even overhauling my entire system would be okay, if you have suggestions for how better to implement the whole thing. Book recommendations are welcome too; I love books. I just get the feeling that something isn't quite right.

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  • How to modify TaskDialog's Show() call to be blocking and return a value when closed?

    - by JustABill
    I'm using the WindowsAPICodePack's TaskDialog implementation, but it bugs me that I have to listen to click handlers on its buttons for even the more basic implementations. I'd like to convert/wrap it so that like the old MessageBox it blocks until closed and then returns a value based on what was done. Is there anything I can read for the basics on how to do this? I just have no idea where to even start, as I am admittedly not that familiar with the Win32 underpinnings.

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