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  • Windows Virtual Machine not seen by host (Mac OS X) using VMWare Fusion

    - by Malkuth
    Hi, I installed Windows XP with VMware Fusion on my MacBook and while internet works, Windows can ping the Mac, etc. from the Mac or any other machine in the network we can not see the Virtual Machine. In between, I use bridged option and obtain the the VM's IP dynamically; tried also static assignment from the free addresses but the problem persisted. Any ideas what is wrong?

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  • Mass Remove IP Subnet?

    - by Clear.Cache
    How do I mass delete IPs I no longer use on the server (secondary assignment, not prime subnet) For example I have a specific /27 I want to remove in one shot, instead of one IP at a time via whm delete IPs function I'm using Cpanel/WHM with Centos 5x

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  • List DB2 version, OS and hardware on Linux? (aws image)

    - by mestika
    Hello everybody, I'm not that familiar with Linux but I'm currently working on a aws image for an assignment and I need to display the DB2 version, the OS and the hardware. Is there a commando or program of some sort I can use for this purpose? I tried a rpm called "Bonnie" but that only writes the throughput for the system. Thanks Mestika

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  • List DB2 version, OS and hardware on Linux? (aws image)H

    - by mestika
    Hello everybody, I'm not that familiar with Linux but I'm currently working on a aws image for an assignment and I need to display the DB2 version, the OS and the hardware. Is there a commando or program of some sort I can use for this purpose? I tried a rpm called "Bonnie" but that only writes the throughput for the system. Thanks Mestika

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  • AD logon script, how to...

    - by allenskd
    I'm a student, I have this assignment where I need to know how to disable the user from changing the background to a client computer, thing is that I've been looking around to know what language does the logon script use, any site with handy information, tried googling but I really can't find anything useful, don't know if I'm googling the right terms All I've found for now is a lot of tutorials about mapping network drives and so on

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  • Add site to trusted sites through GPO

    - by Matt Bear
    I need to add a site to trusted sites on all computers in my domain. I can do it with the "site to zone assignment list", however when I do, it locks trusted sites on the client computer "this setting is managed by your administrator". What I need is a way to add the site, make it persistant, and not affects the users ability to add trusted sites of thier own. (It's a development enviroment, sites are created and tested regularly, they need that ability.)

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  • cannot paste words with pictures in ms word 2010

    - by user23950
    Is there any option that will correct this? I'm pasting my assignment with some pictures in it in ms word 2010 from a webpage but it doesn't seem to be showing the picture that is copied along with the words. When I try to right click and see the paste options. The only option that I can see is text. Please help.

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  • Limiting database security

    - by Torbal
    A number of texts signify that the most important aspects offered by a DBMS are availability, integrity and secrecy. As part of a homework assignment I have been tasked with mentioning attacks which would affect each aspect. This is what I have come up with - are they any good? Availability - DDOS attack Integrity Secrecy - SQL Injection attack Integrity - Use of trojans to gain access to objects with higher security roles

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  • Number of subnets for specific mask

    - by kutacz
    Question source Problem: Your company has been assigned the following IP address: 192.112.136.0 /27 Your group has been assigned the fourth subnet. Question 5: How many useable subnets are available for assignment? Why the answer is 6? I would shoot it's 8 , because 255/32 = 8. More generally - what is an correct algorithm to compute the number of available subnetworks for the same mask?

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  • SSD installed but system reserved drive is visible, how to fix?

    - by JL
    I've just installed an SSD as primary boot drive. During install, a system reserved partition was allocated (not very big) around 100MB. Problem is the drive is visible in explorer and its assigned to D: Anyone else had this problem, and is there a way to somehow hide that drive from explorer, and also get back the drive letter assignment? Thanks

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  • Blank Mail from PHP application

    - by brettlwilliams
    Problem: Blank email from PHP web application. Confirmed: App works in Linux, has various problems in Windows server environment. Blank emails are the last remaining problem. PHP Version 5.2.6 on the server I'm a librarian implementing a PHP based web application to help students complete their assignments.I have installed this application before on a Linux based free web host and had no problems. Email is controlled by two files, email_functions.php and email.php. While email can be sent, all that is sent is a blank email. My IT department is an ASP only shop, so I can get little to no help there. I also cannot install additional libraries like PHPmail or Swiftmailer. You can see a functional copy at http://rpc.elm4you.org/ You can also download a copy from Sourceforge from the link there. Thanks in advance for any insight into this! email_functions.php <?php /********************************************************** Function: build_multipart_headers Author: Michael Berkowski Last Modified: September 2007 *********************************************************** Purpose: Creates email headers for a message of type multipart/mime This will include a plain text part and HTML. **********************************************************/ function build_multipart_headers($boundary_rand) { global $EMAIL_FROM_DISPLAY_NAME, $EMAIL_FROM_ADDRESS, $CALC_PATH, $CALC_TITLE, $SERVER_NAME; // Using \n instead of \r\n because qmail doubles up the \r and screws everything up! $crlf = "\n"; $message_date = date("r"); // Construct headers for multipart/mixed MIME email. It will have a plain text and HTML part $headers = "X-Calc-Name: $CALC_TITLE" . $crlf; $headers .= "X-Calc-Url: http://{$SERVER_NAME}/{$CALC_PATH}" . $crlf; $headers .= "MIME-Version: 1.0" . $crlf; $headers .= "Content-type: multipart/alternative;" . $crlf; $headers .= " boundary=__$boundary_rand" . $crlf; $headers .= "From: $EMAIL_FROM_DISPLAY_NAME <$EMAIL_FROM_ADDRESS>" . $crlf; $headers .= "Sender: $EMAIL_FROM_DISPLAY_NAME <$EMAIL_FROM_ADDRESS>" . $crlf; $headers .= "Reply-to: $EMAIL_FROM_DISPLAY_NAME <$EMAIL_FROM_ADDRESS>" . $crlf; $headers .= "Return-Path: $EMAIL_FROM_DISPLAY_NAME <$EMAIL_FROM_ADDRESS>" . $crlf; $headers .= "Date: $message_date" . $crlf; $headers .= "Message-Id: $boundary_rand@$SERVER_NAME" . $crlf; return $headers; } /********************************************************** Function: build_multipart_body Author: Michael Berkowski Last Modified: September 2007 *********************************************************** Purpose: Builds the email body content to go with the headers from build_multipart_headers() **********************************************************/ function build_multipart_body($plain_text_message, $html_message, $boundary_rand) { //$crlf = "\r\n"; $crlf = "\n"; $boundary = "__" . $boundary_rand; // Begin constructing the MIME multipart message $multipart_message = "This is a multipart message in MIME format." . $crlf . $crlf; $multipart_message .= "--{$boundary}{$crlf}Content-type: text/plain; charset=\"us-ascii\"{$crlf}Content-Transfer-Encoding: 7bit{$crlf}{$crlf}"; $multipart_message .= $plain_text_message . $crlf . $crlf; $multipart_message .= "--{$boundary}{$crlf}Content-type: text/html; charset=\"iso-8859-1\"{$crlf}Content-Transfer-Encoding: 7bit{$crlf}{$crlf}"; $multipart_message .= $html_message . $crlf . $crlf; $multipart_message .= "--{$boundary}--$crlf$crlf"; return $multipart_message; } /********************************************************** Function: build_step_email_body_text Author: Michael Berkowski Last Modified: September 2007 *********************************************************** Purpose: Returns a plain text version of the email body to be used for individually sent step reminders **********************************************************/ function build_step_email_body_text($stepnum, $arr_instructions, $dates, $query_string, $teacher_info ,$name, $class, $project_id) { global $CALC_PATH, $CALC_TITLE, $SERVER_NAME; $step_email_body =<<<BODY $CALC_TITLE Step $stepnum: {$arr_instructions["step$stepnum"]["title"]} Name: $name Class: $class BODY; $step_email_body .= build_text_single_step($stepnum, $arr_instructions, $dates, $query_string, $teacher_info); $step_email_body .= "\n\n"; $step_email_body .=<<<FOOTER The $CALC_TITLE offers suggestions, but be sure to check with your teacher to find out the best working schedule for your assignment! If you would like to stop receiving further reminders for this project, click the link below: http://$SERVER_NAME/$CALC_PATH/deleteproject.php?proj=$project_id FOOTER; // Wrap text to 78 chars per line // Convert any remaining HTML <br /> to \r\n // Strip out any remaining HTML tags. $step_email_body = strip_tags(linebreaks_html2text(wordwrap($step_email_body, 78, "\n"))); return $step_email_body; } /********************************************************** Function: build_step_email_body_html Author: Michael Berkowski Last Modified: September 2007 *********************************************************** Purpose: Same as above, but with HTML **********************************************************/ function build_step_email_body_html($stepnum, $arr_instructions, $dates, $query_string, $teacher_info, $name, $class, $project_id) { global $CALC_PATH, $CALC_TITLE, $SERVER_NAME; $styles = build_html_styles(); $step_email_body =<<<BODY <html> <head> <title> $CALC_TITLE </title> $styles </head> <body> <h1> $CALC_TITLE Schedule </h1> <strong>Name:</strong> $name <br /> <strong>Class:</strong> $class <br /> BODY; $step_email_body .= build_html_single_step($stepnum, $arr_instructions, $dates, $query_string, $teacher_info); $step_email_body .=<<<FOOTER <p> The $CALC_TITLE offers suggestions, but be sure to check with your teacher to find out the best working schedule for your assignment! </p> <p> If you would like to stop receiving further reminders for this project, <a href="http://{$SERVER_NAME}/$CALC_PATH/deleteproject.php?proj=$project_id">click this link.</a> </p> </body> </html> FOOTER; return $step_email_body; } /********************************************************** Function: build_html_styles Author: Michael Berkowski Last Modified: September 2007 *********************************************************** Purpose: Just returns a string of <style /> for the HTML message body **********************************************************/ function build_html_styles() { $styles =<<<STYLES <style type="text/css"> body { font-family: Arial, sans-serif; font-size: 85%; } h1 { font-size: 120%; } table { border: none; } tr { vertical-align: top; } img { display: none; } hr { border: 0; } </style> STYLES; return $styles; } /********************************************************** Function: linebreaks_html2text Author: Michael Berkowski Last Modified: October 2007 *********************************************************** Purpose: Convert <br /> html tags to \n line breaks **********************************************************/ function linebreaks_html2text($in_string) { $out_string = ""; $arr_br = array("<br>", "<br />", "<br/>"); $out_string = str_replace($arr_br, "\n", $in_string); return $out_string; } ?> email.php <?php require_once("include/config.php"); require_once("include/instructions.php"); require_once("dbase/dbfunctions.php"); require_once("include/email_functions.php"); ini_set("sendmail_from", "[email protected]"); ini_set("SMTP", "mail.qatar.net.qa"); // Verify that the email has not already been sent by checking for a cookie // whose value is generated each time the form is loaded freshly. if (!(isset($_COOKIE['rpc_transid']) && $_COOKIE['rpc_transid'] == $_POST['transid'])) { // Setup some preliminary variables for email. // The scanning of $_POST['email']already took place when this file was included... $to = $_POST['email']; $subject = $EMAIL_SUBJECT; $boundary_rand = md5(rand()); $mail_type = ""; switch ($_POST['reminder-type']) { case "progressive": $arr_dbase_dates = array(); $conn = rpc_connect(); if (!$conn) { $mail_success = FALSE; $mail_status_message = "Could not register address!"; break; } // Sanitize all the data that will be inserted into table... // We need to remove "CONTENT-TYPE:" from name/class to defang them. // Additionall, we can't allow any line-breaks in those fields to avoid // hacks to email headers. $ins_name = mysql_real_escape_string($name); $ins_name = eregi_replace("CONTENT-TYPE", "...Content_Type...", $ins_name); $ins_name = str_replace("\n", "", $ins_name); $ins_class = mysql_real_escape_string($class); $ins_class = eregi_replace("CONTENT-TYPE", "...Content_Type...", $ins_class); $ins_class = str_replace("\n", "", $ins_class); $ins_email = mysql_real_escape_string($email); $ins_teacher_info = $teacher_info ? "YES" : "NO"; switch ($format) { case "Slides": $ins_format = "SLIDES"; break; case "Video": $ins_format = "VIDEO"; break; case "Essay": default: $ins_format = "ESSAY"; break; } // The transid from the previous form will be used as a project identifier // Steps will be grouped by project identifier. $ins_project_id = mysql_real_escape_string($_POST['transid'] . md5(rand())); $arr_dbase_dates = dbase_dates($dates); $arr_past_dates = array(); // Iterate over the dates array and build a SQL statement for each one. $insert_success = TRUE; // $min_reminder_date = date("Ymd", mktime(0,0,0,date("m"),date("d")+$EMAIL_REMINDER_DAYS_AHEAD,date("Y"))); for ($date_index = 0; $date_index < sizeof($arr_dbase_dates); $date_index++) { // Make sure we're using the right keys... $ins_date_index = $date_index + 1; // The insert will only happen if the date of the event is in the future. // For dates today and earlier, no insert. // For dates today or after the reminder deadline, we'll send the email immediately after the inserts. if ($arr_dbase_dates[$date_index] > (int)$min_reminder_date) { $qry =<<<QRY INSERT INTO email_queue ( NOTIFICATION_ID, PROJECT_ID, EMAIL, NAME, CLASS, FORMAT, TEACHER_INFO, STEP, MESSAGE_DATE ) VALUES ( NULL, '$ins_project_id', '$ins_email', '$ins_name', '$ins_class', '$ins_format', '$ins_teacher_info', $ins_date_index, /*step number*/ {$arr_dbase_dates[$date_index]} /* Date in the integer format yyyymmdd */ ) QRY; // Attempt to do the insert... $result = mysql_query($qry); // If even one insert fails, bail out. if (!$result) { $mail_success = FALSE; $mail_status_message = "Could not register address!"; break; } } // For dates today or earlier, store the steps=>dates in an array so the mails can // be sent immediately. else { $arr_past_dates[$ins_date_index] = $arr_dbase_dates[$date_index]; } } // Close the connection resources. mysql_close($conn); // SEND OUT THE EMAILS THAT HAVE TO GO IMMEDIATELY... // This should only be step 1, but who knows... //var_dump($arr_past_dates); for ($stepnum=1; $stepnum<=sizeof($arr_past_dates); $stepnum++) { $email_teacher_info = ($teacher_info && $EMAIL_TEACHER_REMINDERS) ? TRUE : FALSE; $boundary = md5(rand()); $plain_text_body = build_step_email_body_text($stepnum, $arr_instructions, $dates, $query_string, $email_teacher_info ,$name, $class, $ins_project_id); $html_body = build_step_email_body_html($stepnum, $arr_instructions, $dates, $query_string, $email_teacher_info ,$name, $class, $ins_project_id); $multipart_headers = build_multipart_headers($boundary); $multipart_body = build_multipart_body($plain_text_body, $html_body, $boundary); mail($to, $subject . ": Step " . $stepnum, $multipart_body, $multipart_headers, "[email protected]"); } // Set appropriate flags and messages $mail_success = TRUE; $mail_status_message = "Email address registered!"; $mail_type = "progressive"; set_mail_success_cookie(); break; // Default to a single email message. case "single": default: // We don't want to send images in the message, so strip them out of the existing structure. // This big ugly regex strips the whole table cell containing the image out of the table. // Must find a better solution... //$email_table_html = eregi_replace("<td class=\"stepImageContainer\" width=\"161px\">[\s\r\n\t]*<img class=\"stepImage\" src=\"images/[_a-zA-Z0-9]*\.gif\" alt=\"Step [1-9]{1} logo\" />[\s\r\n\t]*</td>", "\n", $table_html); // Show more descriptive text based on the value of $format switch ($format) { case "Video": $format_display = "Video"; break; case "Slides": $format_display = "Presentation with electronic slides"; break; case "Essay": default: $format_display = "Essay"; break; } $days = (int)$days; $html_message = ""; $styles = build_html_styles(); $html_message =<<<HTMLMESSAGE <html> <head> <title> $CALC_TITLE </title> $styles </head> <body> <h1> $CALC_TITLE Schedule </h1> <strong>Name:</strong> $name <br /> <strong>Class:</strong> $class <br /> <strong>Email:</strong> $email <br /> <strong>Assignment type:</strong> $format_display <br /><br /> <strong>Starting on:</strong> $date1 <br /> <strong>Assignment due:</strong> $date2 <br /> <strong>You have $days days to finish.</strong><br /> <hr /> $email_table_html </body> </html> HTMLMESSAGE; // Create the plain text version of the message... $plain_text_message = strip_tags(linebreaks_html2text(build_text_all_steps($arr_instructions, $dates, $query_string, $teacher_info))); // Add the title, since it doesn't get built in by build_text_all_steps... $plain_text_message = $CALC_TITLE . " Schedule\n\n" . $plain_text_message; $plain_text_message = wordwrap($plain_text_message, 78, "\n"); $multipart_headers = build_multipart_headers($boundary_rand); $multipart_message = build_multipart_body($plain_text_message, $html_message, $boundary_rand); $mail_success = FALSE; if (mail($to, $subject, $multipart_message, $multipart_headers, "[email protected]")) { $mail_success = TRUE; $mail_status_message = "Email sent!"; $mail_type = "single"; set_mail_success_cookie(); } else { $mail_success = FALSE; $mail_status_message = "Could not send email!"; } break; } } function set_mail_success_cookie() { // Prevent the mail from being resent on page reload. Set a timestamp cookie. // Expires in 24 hours. setcookie("rpc_transid", $_POST['transid'], time() + 86400); } ?>

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  • UPK Content State

    - by peter.maravelias
    State is an editable property for communicating the status of a document in the UPK library. This is particularly helpful when working with other authors in a development team. Authors can assign a state to any document using the values that are defined in the master list. The default master list of State values includes Not Started, Draft, In Review, and Final (in the language installed on the server). Administrators can customize the list by adding, deleting, or renaming the values as well as sequencing the values as they will appear on the assignment list from the Properties pane. Let us know if or how you are using UPK Content States in your development efforts!

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  • MySQL server with website hosting with managed hosting

    - by BlackSheep
    I work for a small business, and I am the "IT Department". I also happen to be a summer intern, so after I leave the number of IT staff will be 0 for an indefinite period of time. I need a place where I can reliably put up the company's website as well as the mySQL+PHP backend. Good redundancy is a plus, as well as easy administration for my IT-challenged colleagues. Managed hosting would be good, so the PHP versions can update without my company having to hire an admin. EDIT: The company already has a mySQL+PHP server running locally which hosts the existing website. My assignment is to find a remote server where the latest versions of mySQL+PHP will be maintained and where there is a very small chance of unintended downtime. Can you recommend anything?

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  • C# 4.0: Covariance And Contravariance In Generics

    - by Paulo Morgado
    C# 4.0 (and .NET 4.0) introduced covariance and contravariance to generic interfaces and delegates. But what is this variance thing? According to Wikipedia, in multilinear algebra and tensor analysis, covariance and contravariance describe how the quantitative description of certain geometrical or physical entities changes when passing from one coordinate system to another.(*) But what does this have to do with C# or .NET? In type theory, a the type T is greater (>) than type S if S is a subtype (derives from) T, which means that there is a quantitative description for types in a type hierarchy. So, how does covariance and contravariance apply to C# (and .NET) generic types? In C# (and .NET), variance applies to generic type parameters and not to the resulting generic type. A generic type parameter is: covariant if the ordering of the generic types follows the ordering of the generic type parameters: Generic<T> = Generic<S> for T = S. contravariant if the ordering of the generic types is reversed from the ordering of the generic type parameters: Generic<T> = Generic<S> for T = S. invariant if neither of the above apply. If this definition is applied to arrays, we can see that arrays have always been covariant because this is valid code: object[] objectArray = new string[] { "string 1", "string 2" }; objectArray[0] = "string 3"; objectArray[1] = new object(); However, when we try to run this code, the second assignment will throw an ArrayTypeMismatchException. Although the compiler was fooled into thinking this was valid code because an object is being assigned to an element of an array of object, at run time, there is always a type check to guarantee that the runtime type of the definition of the elements of the array is greater or equal to the instance being assigned to the element. In the above example, because the runtime type of the array is array of string, the first assignment of array elements is valid because string = string and the second is invalid because string = object. This leads to the conclusion that, although arrays have always been covariant, they are not safely covariant – code that compiles is not guaranteed to run without errors. In C#, the way to define that a generic type parameter as covariant is using the out generic modifier: public interface IEnumerable<out T> { IEnumerator<T> GetEnumerator(); } public interface IEnumerator<out T> { T Current { get; } bool MoveNext(); } Notice the convenient use the pre-existing out keyword. Besides the benefit of not having to remember a new hypothetic covariant keyword, out is easier to remember because it defines that the generic type parameter can only appear in output positions — read-only properties and method return values. In a similar way, the way to define a type parameter as contravariant is using the in generic modifier: public interface IComparer<in T> { int Compare(T x, T y); } Once again, the use of the pre-existing in keyword makes it easier to remember that the generic type parameter can only be used in input positions — write-only properties and method non ref and non out parameters. Because covariance and contravariance apply only to the generic type parameters, a generic type definition can have both covariant and contravariant generic type parameters in its definition: public delegate TResult Func<in T, out TResult>(T arg); A generic type parameter that is not marked covariant (out) or contravariant (in) is invariant. All the types in the .NET Framework where variance could be applied to its generic type parameters have been modified to take advantage of this new feature. In summary, the rules for variance in C# (and .NET) are: Variance in type parameters are restricted to generic interface and generic delegate types. A generic interface or generic delegate type can have both covariant and contravariant type parameters. Variance applies only to reference types; if you specify a value type for a variant type parameter, that type parameter is invariant for the resulting constructed type. Variance does not apply to delegate combination. That is, given two delegates of types Action<Derived> and Action<Base>, you cannot combine the second delegate with the first although the result would be type safe. Variance allows the second delegate to be assigned to a variable of type Action<Derived>, but delegates can combine only if their types match exactly. If you want to learn more about variance in C# (and .NET), you can always read: Covariance and Contravariance in Generics — MSDN Library Exact rules for variance validity — Eric Lippert Events get a little overhaul in C# 4, Afterward: Effective Events — Chris Burrows Note: Because variance is a feature of .NET 4.0 and not only of C# 4.0, all this also applies to Visual Basic 10.

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  • What are the most important OO skills to show off in the job hunt?

    - by Kat
    I am in the market for new employment, and found a position were they asked me to create a programming sample based off an assignment. I blew the sample trying to get it done quickly one night, and got declined - only to be given a second chance recently. The concern was that I didn't really demonstrate object oriented knowledge. I've rethought my approach but I figure it's worth asking: if you were hiring someone for an OO position, what skills would you most want to see them demonstrate they had a firm grasp on? I want to be sure that I'm missing anything important this time around.

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  • Question about casting a class in Java with generics

    - by Florian F
    In Java 6 Class<? extends ArrayList<?>> a = ArrayList.class; gives and error, but Class<? extends ArrayList<?>> b = (Class<? extends ArrayList<?>>)ArrayList.class; gives a warning. Why is (a) an error? What is it, that Java needs to do in the assignment, if not the cast shown in (b)? And why isn't ArrayList compatible with ArrayList? I know one is "raw" and the other is "generic", but what is it you can do with an ArrayList and not with an ArrayList, or the other way around?

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  • SPRoleAssignment Crazy Caviats

    - by MOSSLover
    I’m not sure if this bug exists on any other environment, but here are a few issues I ran into when trying to use SPRoleAssignment and SPGroup: When trying to use Web.Groups[“GroupName”] it basically told me the group did not exist, so I had to change the code to use Web.SiteGroups[“GroupName”]. I could not add the Role Assignment to the Web and run a Web.Update() without adding an additional Web.AllowUnsafeUpdates= true; , however on my virtual machine I could do a Web.Update() without the extra piece of code.  I kept receiving an error in my browser stating that I should hit the back button and update my permissions. So after fixing those two issues I was able to copy the permissions from a page item into a Site for my migration.  Hopefully, one of you can learn from my error messages if you have any issues in the future. Technorati Tags: SPRoleAssignment,MOSS,SPGroup

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  • PTLQueue : a scalable bounded-capacity MPMC queue

    - by Dave
    Title: Fast concurrent MPMC queue -- I've used the following concurrent queue algorithm enough that it warrants a blog entry. I'll sketch out the design of a fast and scalable multiple-producer multiple-consumer (MPSC) concurrent queue called PTLQueue. The queue has bounded capacity and is implemented via a circular array. Bounded capacity can be a useful property if there's a mismatch between producer rates and consumer rates where an unbounded queue might otherwise result in excessive memory consumption by virtue of the container nodes that -- in some queue implementations -- are used to hold values. A bounded-capacity queue can provide flow control between components. Beware, however, that bounded collections can also result in resource deadlock if abused. The put() and take() operators are partial and wait for the collection to become non-full or non-empty, respectively. Put() and take() do not allocate memory, and are not vulnerable to the ABA pathologies. The PTLQueue algorithm can be implemented equally well in C/C++ and Java. Partial operators are often more convenient than total methods. In many use cases if the preconditions aren't met, there's nothing else useful the thread can do, so it may as well wait via a partial method. An exception is in the case of work-stealing queues where a thief might scan a set of queues from which it could potentially steal. Total methods return ASAP with a success-failure indication. (It's tempting to describe a queue or API as blocking or non-blocking instead of partial or total, but non-blocking is already an overloaded concurrency term. Perhaps waiting/non-waiting or patient/impatient might be better terms). It's also trivial to construct partial operators by busy-waiting via total operators, but such constructs may be less efficient than an operator explicitly and intentionally designed to wait. A PTLQueue instance contains an array of slots, where each slot has volatile Turn and MailBox fields. The array has power-of-two length allowing mod/div operations to be replaced by masking. We assume sensible padding and alignment to reduce the impact of false sharing. (On x86 I recommend 128-byte alignment and padding because of the adjacent-sector prefetch facility). Each queue also has PutCursor and TakeCursor cursor variables, each of which should be sequestered as the sole occupant of a cache line or sector. You can opt to use 64-bit integers if concerned about wrap-around aliasing in the cursor variables. Put(null) is considered illegal, but the caller or implementation can easily check for and convert null to a distinguished non-null proxy value if null happens to be a value you'd like to pass. Take() will accordingly convert the proxy value back to null. An advantage of PTLQueue is that you can use atomic fetch-and-increment for the partial methods. We initialize each slot at index I with (Turn=I, MailBox=null). Both cursors are initially 0. All shared variables are considered "volatile" and atomics such as CAS and AtomicFetchAndIncrement are presumed to have bidirectional fence semantics. Finally T is the templated type. I've sketched out a total tryTake() method below that allows the caller to poll the queue. tryPut() has an analogous construction. Zebra stripping : alternating row colors for nice-looking code listings. See also google code "prettify" : https://code.google.com/p/google-code-prettify/ Prettify is a javascript module that yields the HTML/CSS/JS equivalent of pretty-print. -- pre:nth-child(odd) { background-color:#ff0000; } pre:nth-child(even) { background-color:#0000ff; } border-left: 11px solid #ccc; margin: 1.7em 0 1.7em 0.3em; background-color:#BFB; font-size:12px; line-height:65%; " // PTLQueue : Put(v) : // producer : partial method - waits as necessary assert v != null assert Mask = 1 && (Mask & (Mask+1)) == 0 // Document invariants // doorway step // Obtain a sequence number -- ticket // As a practical concern the ticket value is temporally unique // The ticket also identifies and selects a slot auto tkt = AtomicFetchIncrement (&PutCursor, 1) slot * s = &Slots[tkt & Mask] // waiting phase : // wait for slot's generation to match the tkt value assigned to this put() invocation. // The "generation" is implicitly encoded as the upper bits in the cursor // above those used to specify the index : tkt div (Mask+1) // The generation serves as an epoch number to identify a cohort of threads // accessing disjoint slots while s-Turn != tkt : Pause assert s-MailBox == null s-MailBox = v // deposit and pass message Take() : // consumer : partial method - waits as necessary auto tkt = AtomicFetchIncrement (&TakeCursor,1) slot * s = &Slots[tkt & Mask] // 2-stage waiting : // First wait for turn for our generation // Acquire exclusive "take" access to slot's MailBox field // Then wait for the slot to become occupied while s-Turn != tkt : Pause // Concurrency in this section of code is now reduced to just 1 producer thread // vs 1 consumer thread. // For a given queue and slot, there will be most one Take() operation running // in this section. // Consumer waits for producer to arrive and make slot non-empty // Extract message; clear mailbox; advance Turn indicator // We have an obvious happens-before relation : // Put(m) happens-before corresponding Take() that returns that same "m" for T v = s-MailBox if v != null : s-MailBox = null ST-ST barrier s-Turn = tkt + Mask + 1 // unlock slot to admit next producer and consumer return v Pause tryTake() : // total method - returns ASAP with failure indication for auto tkt = TakeCursor slot * s = &Slots[tkt & Mask] if s-Turn != tkt : return null T v = s-MailBox // presumptive return value if v == null : return null // ratify tkt and v values and commit by advancing cursor if CAS (&TakeCursor, tkt, tkt+1) != tkt : continue s-MailBox = null ST-ST barrier s-Turn = tkt + Mask + 1 return v The basic idea derives from the Partitioned Ticket Lock "PTL" (US20120240126-A1) and the MultiLane Concurrent Bag (US8689237). The latter is essentially a circular ring-buffer where the elements themselves are queues or concurrent collections. You can think of the PTLQueue as a partitioned ticket lock "PTL" augmented to pass values from lock to unlock via the slots. Alternatively, you could conceptualize of PTLQueue as a degenerate MultiLane bag where each slot or "lane" consists of a simple single-word MailBox instead of a general queue. Each lane in PTLQueue also has a private Turn field which acts like the Turn (Grant) variables found in PTL. Turn enforces strict FIFO ordering and restricts concurrency on the slot mailbox field to at most one simultaneous put() and take() operation. PTL uses a single "ticket" variable and per-slot Turn (grant) fields while MultiLane has distinct PutCursor and TakeCursor cursors and abstract per-slot sub-queues. Both PTL and MultiLane advance their cursor and ticket variables with atomic fetch-and-increment. PTLQueue borrows from both PTL and MultiLane and has distinct put and take cursors and per-slot Turn fields. Instead of a per-slot queues, PTLQueue uses a simple single-word MailBox field. PutCursor and TakeCursor act like a pair of ticket locks, conferring "put" and "take" access to a given slot. PutCursor, for instance, assigns an incoming put() request to a slot and serves as a PTL "Ticket" to acquire "put" permission to that slot's MailBox field. To better explain the operation of PTLQueue we deconstruct the operation of put() and take() as follows. Put() first increments PutCursor obtaining a new unique ticket. That ticket value also identifies a slot. Put() next waits for that slot's Turn field to match that ticket value. This is tantamount to using a PTL to acquire "put" permission on the slot's MailBox field. Finally, having obtained exclusive "put" permission on the slot, put() stores the message value into the slot's MailBox. Take() similarly advances TakeCursor, identifying a slot, and then acquires and secures "take" permission on a slot by waiting for Turn. Take() then waits for the slot's MailBox to become non-empty, extracts the message, and clears MailBox. Finally, take() advances the slot's Turn field, which releases both "put" and "take" access to the slot's MailBox. Note the asymmetry : put() acquires "put" access to the slot, but take() releases that lock. At any given time, for a given slot in a PTLQueue, at most one thread has "put" access and at most one thread has "take" access. This restricts concurrency from general MPMC to 1-vs-1. We have 2 ticket locks -- one for put() and one for take() -- each with its own "ticket" variable in the form of the corresponding cursor, but they share a single "Grant" egress variable in the form of the slot's Turn variable. Advancing the PutCursor, for instance, serves two purposes. First, we obtain a unique ticket which identifies a slot. Second, incrementing the cursor is the doorway protocol step to acquire the per-slot mutual exclusion "put" lock. The cursors and operations to increment those cursors serve double-duty : slot-selection and ticket assignment for locking the slot's MailBox field. At any given time a slot MailBox field can be in one of the following states: empty with no pending operations -- neutral state; empty with one or more waiting take() operations pending -- deficit; occupied with no pending operations; occupied with one or more waiting put() operations -- surplus; empty with a pending put() or pending put() and take() operations -- transitional; or occupied with a pending take() or pending put() and take() operations -- transitional. The partial put() and take() operators can be implemented with an atomic fetch-and-increment operation, which may confer a performance advantage over a CAS-based loop. In addition we have independent PutCursor and TakeCursor cursors. Critically, a put() operation modifies PutCursor but does not access the TakeCursor and a take() operation modifies the TakeCursor cursor but does not access the PutCursor. This acts to reduce coherence traffic relative to some other queue designs. It's worth noting that slow threads or obstruction in one slot (or "lane") does not impede or obstruct operations in other slots -- this gives us some degree of obstruction isolation. PTLQueue is not lock-free, however. The implementation above is expressed with polite busy-waiting (Pause) but it's trivial to implement per-slot parking and unparking to deschedule waiting threads. It's also easy to convert the queue to a more general deque by replacing the PutCursor and TakeCursor cursors with Left/Front and Right/Back cursors that can move either direction. Specifically, to push and pop from the "left" side of the deque we would decrement and increment the Left cursor, respectively, and to push and pop from the "right" side of the deque we would increment and decrement the Right cursor, respectively. We used a variation of PTLQueue for message passing in our recent OPODIS 2013 paper. ul { list-style:none; padding-left:0; padding:0; margin:0; margin-left:0; } ul#myTagID { padding: 0px; margin: 0px; list-style:none; margin-left:0;} -- -- There's quite a bit of related literature in this area. I'll call out a few relevant references: Wilson's NYU Courant Institute UltraComputer dissertation from 1988 is classic and the canonical starting point : Operating System Data Structures for Shared-Memory MIMD Machines with Fetch-and-Add. Regarding provenance and priority, I think PTLQueue or queues effectively equivalent to PTLQueue have been independently rediscovered a number of times. See CB-Queue and BNPBV, below, for instance. But Wilson's dissertation anticipates the basic idea and seems to predate all the others. Gottlieb et al : Basic Techniques for the Efficient Coordination of Very Large Numbers of Cooperating Sequential Processors Orozco et al : CB-Queue in Toward high-throughput algorithms on many-core architectures which appeared in TACO 2012. Meneghin et al : BNPVB family in Performance evaluation of inter-thread communication mechanisms on multicore/multithreaded architecture Dmitry Vyukov : bounded MPMC queue (highly recommended) Alex Otenko : US8607249 (highly related). John Mellor-Crummey : Concurrent queues: Practical fetch-and-phi algorithms. Technical Report 229, Department of Computer Science, University of Rochester Thomasson : FIFO Distributed Bakery Algorithm (very similar to PTLQueue). Scott and Scherer : Dual Data Structures I'll propose an optimization left as an exercise for the reader. Say we wanted to reduce memory usage by eliminating inter-slot padding. Such padding is usually "dark" memory and otherwise unused and wasted. But eliminating the padding leaves us at risk of increased false sharing. Furthermore lets say it was usually the case that the PutCursor and TakeCursor were numerically close to each other. (That's true in some use cases). We might still reduce false sharing by incrementing the cursors by some value other than 1 that is not trivially small and is coprime with the number of slots. Alternatively, we might increment the cursor by one and mask as usual, resulting in a logical index. We then use that logical index value to index into a permutation table, yielding an effective index for use in the slot array. The permutation table would be constructed so that nearby logical indices would map to more distant effective indices. (Open question: what should that permutation look like? Possibly some perversion of a Gray code or De Bruijn sequence might be suitable). As an aside, say we need to busy-wait for some condition as follows : "while C == 0 : Pause". Lets say that C is usually non-zero, so we typically don't wait. But when C happens to be 0 we'll have to spin for some period, possibly brief. We can arrange for the code to be more machine-friendly with respect to the branch predictors by transforming the loop into : "if C == 0 : for { Pause; if C != 0 : break; }". Critically, we want to restructure the loop so there's one branch that controls entry and another that controls loop exit. A concern is that your compiler or JIT might be clever enough to transform this back to "while C == 0 : Pause". You can sometimes avoid this by inserting a call to a some type of very cheap "opaque" method that the compiler can't elide or reorder. On Solaris, for instance, you could use :"if C == 0 : { gethrtime(); for { Pause; if C != 0 : break; }}". It's worth noting the obvious duality between locks and queues. If you have strict FIFO lock implementation with local spinning and succession by direct handoff such as MCS or CLH,then you can usually transform that lock into a queue. Hidden commentary and annotations - invisible : * And of course there's a well-known duality between queues and locks, but I'll leave that topic for another blog post. * Compare and contrast : PTLQ vs PTL and MultiLane * Equivalent : Turn; seq; sequence; pos; position; ticket * Put = Lock; Deposit Take = identify and reserve slot; wait; extract & clear; unlock * conceptualize : Distinct PutLock and TakeLock implemented as ticket lock or PTL Distinct arrival cursors but share per-slot "Turn" variable provides exclusive role-based access to slot's mailbox field put() acquires exclusive access to a slot for purposes of "deposit" assigns slot round-robin and then acquires deposit access rights/perms to that slot take() acquires exclusive access to slot for purposes of "withdrawal" assigns slot round-robin and then acquires withdrawal access rights/perms to that slot At any given time, only one thread can have withdrawal access to a slot at any given time, only one thread can have deposit access to a slot Permissible for T1 to have deposit access and T2 to simultaneously have withdrawal access * round-robin for the purposes of; role-based; access mode; access role mailslot; mailbox; allocate/assign/identify slot rights; permission; license; access permission; * PTL/Ticket hybrid Asymmetric usage ; owner oblivious lock-unlock pairing K-exclusion add Grant cursor pass message m from lock to unlock via Slots[] array Cursor performs 2 functions : + PTL ticket + Assigns request to slot in round-robin fashion Deconstruct protocol : explication put() : allocate slot in round-robin fashion acquire PTL for "put" access store message into slot associated with PTL index take() : Acquire PTL for "take" access // doorway step seq = fetchAdd (&Grant, 1) s = &Slots[seq & Mask] // waiting phase while s-Turn != seq : pause Extract : wait for s-mailbox to be full v = s-mailbox s-mailbox = null Release PTL for both "put" and "take" access s-Turn = seq + Mask + 1 * Slot round-robin assignment and lock "doorway" protocol leverage the same cursor and FetchAdd operation on that cursor FetchAdd (&Cursor,1) + round-robin slot assignment and dispersal + PTL/ticket lock "doorway" step waiting phase is via "Turn" field in slot * PTLQueue uses 2 cursors -- put and take. Acquire "put" access to slot via PTL-like lock Acquire "take" access to slot via PTL-like lock 2 locks : put and take -- at most one thread can access slot's mailbox Both locks use same "turn" field Like multilane : 2 cursors : put and take slot is simple 1-capacity mailbox instead of queue Borrow per-slot turn/grant from PTL Provides strict FIFO Lock slot : put-vs-put take-vs-take at most one put accesses slot at any one time at most one put accesses take at any one time reduction to 1-vs-1 instead of N-vs-M concurrency Per slot locks for put/take Release put/take by advancing turn * is instrumental in ... * P-V Semaphore vs lock vs K-exclusion * See also : FastQueues-excerpt.java dice-etc/queue-mpmc-bounded-blocking-circular-xadd/ * PTLQueue is the same as PTLQB - identical * Expedient return; ASAP; prompt; immediately * Lamport's Bakery algorithm : doorway step then waiting phase Threads arriving at doorway obtain a unique ticket number Threads enter in ticket order * In the terminology of Reed and Kanodia a ticket lock corresponds to the busy-wait implementation of a semaphore using an eventcount and a sequencer It can also be thought of as an optimization of Lamport's bakery lock was designed for fault-tolerance rather than performance Instead of spinning on the release counter, processors using a bakery lock repeatedly examine the tickets of their peers --

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  • Is it necessary to create a database with as few tables as possible

    - by Shaheer
    Should we create a database structure with a minimum number of tables? Should it be designed in a way that everything stays in one place or is it okay to have more tables? Will it in anyway affect anything? I am asking this question because a friend of mine modified some database structure in mediaWiki. In the end, instead of 20 tables he was using only 8, and it took him 8 months to do that (it was his college assignment). EDIT I am concluding the answer as: size of the tables does NOT matter, until the case is exceptional; in which case the denormalization may help. Thanks to everyone for the answers.

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  • Coolbits not working

    - by usk
    I want to use coolbits to increase fan speed of my Fermi GPU. 280.13 driver installed. Ubuntu 11.10 I edited /etc/X11/xorg.conf as follows, by pressing Alt+F2 and gksu gedit /etc/X11/xorg.conf I get Section "Device" Identifier "Device0" Driver "nvidia" VendorName "NVIDIA Corporation" BoardName "GeForce GTX 470" Option "NoLogo" "True" Option "Coolbits" "4" EndSection Started getting these messages, Gtk-WARNING **: Unable to locate theme engine in module_path: "pixmap" So I did this, sudo aptitude install gtk2-engines-pixbuf terminal, a@z:~$ nvidia-settings -a [gpu:0]/GPUFanControlState=1 a@z:~$ nvidia-settings -q fans 1 Fan on z:0 [0] z:0[fan:0] (Fan 0) a@z:~$ nvidia-settings -a [fan:0]/GPUCurrentFanSpeed=80 ERROR: Error assigning value 80 to attribute 'GPUCurrentFanSpeed' (z:0[fan:0]) as specified in assignment '[fan:0]/GPUCurrentFanSpeed=80' (Unknown Error). So, it's not working; I can't enter the fan speed percentage. Also from NVidia X Server, there are no fan controls. http://en.gentoo-wiki.com/wiki/Nvidia#Manual_Fan_Control_for_nVIDIA_Settings

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  • Oracle HRMS APIs

    - by PRajkumar
    Oracle HRMS APIs..... Here I will be sharing all the Oracle HRMS APIs related articles. Item Type Author 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Create Employee API Update Employee API Create Employee Contact API Create Employee Address API Update Employee Address API Create Element Entries for Employee API Delete Element Entries for Employee API Rehire Employee API Create Employee Payment Method API Create and Update Employee Phone API Create and Update Employee Salary Proposal API Update Employee Fed Tax Rule API Create Employee State Tax Rule API Update Employee State Tax Rule API Update Employee Assignment API Puneet Rajkumar Puneet Rajkumar Puneet Rajkumar Puneet Rajkumar Puneet Rajkumar Puneet Rajkumar Puneet Rajkumar Puneet Rajkumar Puneet Rajkumar Puneet Rajkumar Puneet Rajkumar Puneet Rajkumar Puneet Rajkumar Puneet Rajkumar Puneet Rajkumar

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  • Need an idea for an iOS project for a trainee to prove his skills

    - by Umair Khan Jadoon
    I am teaching iOS development to a trainee who has recently joined our startup. He already has strong background and experience in .net. At first phase, he will learn the following things: Basics of Objective C. Views and View Controllers(Navigation, Table, Tabs), gester recognizers, table views, segues etc. Protocols, gesters, delegates. Blocks and multithreading. Now, I have to give him some kind of homework assignment or project to get his skills to action and to know what he has learnt. Any ideas?

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  • Is Silverlight only for eye-candy, or does it have a use in business?

    - by Cyberherbalist
    Granted that Silverlight may make eye-popping websites of great beauty, is there any justification for using it to make practical web applications that have serious business purposes? I'd like to use it (to learn it) for a new assignment I have, which is to build a web-based application that keeps track of the data interfaces used in our organization, but I'm not sure how to justify it, even to myself. Any thoughts on this? If I can't justify it then I will have to build the app using the same old tired straight ASP.NET approach I've used (it seems) a hundred times already.

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  • What should be allowed inside getters and setters?

    - by Botond Balázs
    I got into an interesting internet argument about getter and setter methods and encapsulation. Someone said that all they should do is an assignment (setters) or a variable access (getters) to keep them "pure" and ensure encapsulation. Am I right that this would completely defeat the purpose of having getters and setters in the first place and validation and other logic (without strange side-effects of course) should be allowed? When should validation happen? When setting the value, inside the setter (to protect the object from ever entering an invalid state - my opinion) Before setting the value, outside the setter Inside the object, before each time the value is used Is a setter allowed to change the value (maybe convert a valid value to some canonical internal representation)?

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  • Process arbitrarily large lists without explicit recursion or abstract list functions?

    - by Erica Xu
    This is one of the bonus questions in my assignment. The specific questions is to see the input list as a set and output all subsets of it in a list. We can only use cons, first, rest, empty?, empty, lambda, and cond. And we can only define exactly once. But after a night's thinking I don't see it possible to go through the arbitrarily long list without map or foldr. Is there a way to perform recursion or alternative of recursion with only these functions?

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