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• Windows periodically disconnects, reconnects to the network

  - by einpoklum

  My setup: I have a PC with a Gigabyte GA-MA78S2H motherboard (Realtek Gigabit wired Ethernet on-board). I have the latest drivers (at least the latest driver for the NIC. I'm connecting via an Edimax BR-6216Mg (again, wired connection). For some reason I experience short periodic disconnects and reconnects. Specifically, Skype disconnects, tries to connect, succeeds after a short while; incoming SFTP sessions get dropped; using a browser, I sometime get stuck in the DNS lookup or connection to the website and a page won't load. A couple of seconds later, a reload works. All this happens with Windows XP SP3. With Windows 7, it also happens. (When I initially wrote this question I didn't notice it.) ipconfig for my adapter: Ethernet adapter Local Area Connection: Connection-specific DNS Suffix . : Description . . . . . . . . . . . : Realtek PCIe GBE Family Controller Physical Address. . . . . . . . . : 00-1D-7D-E9-72-9E Dhcp Enabled. . . . . . . . . . . : Yes Autoconfiguration Enabled . . . . : Yes IP Address. . . . . . . . . . . . : 192.168.0.2 Subnet Mask . . . . . . . . . . . : 255.255.255.0 Default Gateway . . . . . . . . . : 192.168.0.254 DHCP Server . . . . . . . . . . . : 192.168.0.254 DNS Servers . . . . . . . . . . . : 192.117.235.235 62.219.186.7 Lease Obtained. . . . . . . . . . : Saturday, March 10, 2012 8:28:20 AM Lease Expires . . . . . . . . . . : Friday, January 26, 1906 2:00:04 AM A result of some tests a couple of the disconnects: C:\Documents and Settings\eyalroz.BAKNUNIN>nslookup google.com DNS request timed out. timeout was 2 seconds. *** Can't find server name for address 192.117.235.235: Timed out DNS request timed out. timeout was 2 seconds. *** Can't find server name for address 62.219.186.7: Timed out *** Default servers are not available Server: UnKnown Address: 192.117.235.235 DNS request timed out. timeout was 2 seconds. DNS request timed out. timeout was 2 seconds. *** Request to UnKnown timed-out C:\Documents and Settings\eyalroz.BAKNUNIN>ping 194.90.1.5 Pinging 194.90.1.5 with 32 bytes of data: Control-C ^C C:\Documents and Settings\eyalroz.BAKNUNIN>tracert -d 194.90.1.5 Tracing route to 194.90.1.5 over a maximum of 30 hops 1 <1 ms <1 ms <1 ms 192.168.0.254 2 * * 11 ms 10.168.128.1 3 14 ms 13 ms 14 ms 212.179.160.142 4 * * * Request timed out. 5 * * * Request timed out. 6 * * 47 ms 62.219.189.169 7 31 ms 27 ms 32 ms 62.219.189.150 8 15 ms 14 ms 16 ms 192.114.65.202 9 15 ms 15 ms 11 ms 212.143.10.66 10 13 ms 29 ms 31 ms 212.143.12.234 11 35 ms 15 ms 18 ms 212.143.8.72 12 22 ms 22 ms 16 ms 194.90.1.5 I usually ping 194.90.1.5 (which is not at my ISP) with 15ms response time and no losses. Things I've done/tried: [2012-03-26] I replaced the cable; I thought that made a difference, but the disconnects were back a while later, so that wasn't it. Updated the NIC driver. Tried reducing the MTU (used a utility called Dr. TCP); there was no effect. I updated my board BIOS revision (which caused all the HW to be "reinstalled" or re-identified - successfully). I installed another NIC, and tried switching to it - same effect with the on-board NIC. A while back I tried another router (although it was an Edimax model) - same problem. Connected the computer directly, with no router. Same problem. ping -t to the router (192.168.0.254) gives pongs, nothing is lost, and time is < 1 ms almost always (sometimes it says 1 or 2 ms). This is the case also during the disconnects.

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• I don't understand how work call_once

  - by SABROG

  Please help me understand how work call_once Here is thread-safe code. I don't understand why this need Thread Local Storage and global_epoch variables. Variable _fast_pthread_once_per_thread_epoch can be changed to constant/enum like {FAST_PTHREAD_ONCE_INIT, BEING_INITIALIZED, FINISH_INITIALIZED}. Why needed count calls in global_epoch? I think this code can be rewriting with logc: if flag FINISH_INITIALIZED do nothing, else go to block with mutexes and this all. #ifndef FAST_PTHREAD_ONCE_H #define FAST_PTHREAD_ONCE_H #include #include typedef sig_atomic_t fast_pthread_once_t; #define FAST_PTHREAD_ONCE_INIT SIG_ATOMIC_MAX extern __thread fast_pthread_once_t _fast_pthread_once_per_thread_epoch; #ifdef __cplusplus extern "C" { #endif extern void fast_pthread_once( pthread_once_t *once, void (*func)(void) ); inline static void fast_pthread_once_inline( fast_pthread_once_t *once, void (*func)(void) ) { fast_pthread_once_t x = *once; /* unprotected access */ if ( x _fast_pthread_once_per_thread_epoch ) { fast_pthread_once( once, func ); } } #ifdef __cplusplus } #endif #endif FAST_PTHREAD_ONCE_H Source fast_pthread_once.c The source is written in C. The lines of the primary function are numbered for reference in the subsequent correctness argument. #include "fast_pthread_once.h" #include static pthread_mutex_t mu = PTHREAD_MUTEX_INITIALIZER; /* protects global_epoch and all fast_pthread_once_t writes */ static pthread_cond_t cv = PTHREAD_COND_INITIALIZER; /* signalled whenever a fast_pthread_once_t is finalized */ #define BEING_INITIALIZED (FAST_PTHREAD_ONCE_INIT - 1) static fast_pthread_once_t global_epoch = 0; /* under mu */ __thread fast_pthread_once_t _fast_pthread_once_per_thread_epoch; static void check( int x ) { if ( x == 0 ) abort(); } void fast_pthread_once( fast_pthread_once_t *once, void (*func)(void) ) { /*01*/ fast_pthread_once_t x = *once; /* unprotected access */ /*02*/ if ( x _fast_pthread_once_per_thread_epoch ) { /*03*/ check( pthread_mutex_lock(µ) == 0 ); /*04*/ if ( *once == FAST_PTHREAD_ONCE_INIT ) { /*05*/ *once = BEING_INITIALIZED; /*06*/ check( pthread_mutex_unlock(µ) == 0 ); /*07*/ (*func)(); /*08*/ check( pthread_mutex_lock(µ) == 0 ); /*09*/ global_epoch++; /*10*/ *once = global_epoch; /*11*/ check( pthread_cond_broadcast(&cv;) == 0 ); /*12*/ } else { /*13*/ while ( *once == BEING_INITIALIZED ) { /*14*/ check( pthread_cond_wait(&cv;, µ) == 0 ); /*15*/ } /*16*/ } /*17*/ _fast_pthread_once_per_thread_epoch = global_epoch; /*18*/ check (pthread_mutex_unlock(µ) == 0); } } This code from BOOST: #ifndef BOOST_THREAD_PTHREAD_ONCE_HPP #define BOOST_THREAD_PTHREAD_ONCE_HPP // once.hpp // // (C) Copyright 2007-8 Anthony Williams // // Distributed under the Boost Software License, Version 1.0. (See // accompanying file LICENSE_1_0.txt or copy at // http://www.boost.org/LICENSE_1_0.txt) #include #include #include #include "pthread_mutex_scoped_lock.hpp" #include #include #include namespace boost { struct once_flag { boost::uintmax_t epoch; }; namespace detail { BOOST_THREAD_DECL boost::uintmax_t& get_once_per_thread_epoch(); BOOST_THREAD_DECL extern boost::uintmax_t once_global_epoch; BOOST_THREAD_DECL extern pthread_mutex_t once_epoch_mutex; BOOST_THREAD_DECL extern pthread_cond_t once_epoch_cv; } #define BOOST_ONCE_INITIAL_FLAG_VALUE 0 #define BOOST_ONCE_INIT {BOOST_ONCE_INITIAL_FLAG_VALUE} // Based on Mike Burrows fast_pthread_once algorithm as described in // http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2444.html template void call_once(once_flag& flag,Function f) { static boost::uintmax_t const uninitialized_flag=BOOST_ONCE_INITIAL_FLAG_VALUE; static boost::uintmax_t const being_initialized=uninitialized_flag+1; boost::uintmax_t const epoch=flag.epoch; boost::uintmax_t& this_thread_epoch=detail::get_once_per_thread_epoch(); if(epoch #endif I right understand, boost don't use atomic operation, so code from boost not thread-safe?

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• Have suggestions for these assembly mnemonics?

  - by Noctis Skytower

  Greetings! Last semester in college, my teacher in the Computer Languages class taught us the esoteric language named Whitespace. In the interest of learning the language better with a very busy schedule (midterms), I wrote an interpreter and assembler in Python. An assembly language was designed to facilitate writing programs easily, and a sample program was written with the given assembly mnemonics. Now that it is summer, a new project has begun with the objective being to rewrite the interpreter and assembler for Whitespace 0.3, with further developments coming afterwards. Since there is so much extra time than before to work on its design, you are presented here with an outline that provides a revised set of mnemonics for the assembly language. This post is marked as a wiki for their discussion. Have you ever had any experience with assembly languages in the past? Were there some instructions that you thought should have been renamed to something different? Did you find yourself thinking outside the box and with a different paradigm than in which the mnemonics were named? If you can answer yes to any of those questions, you are most welcome here. Subjective answers are appreciated! Stack Manipulation (IMP: [Space]) Stack manipulation is one of the more common operations, hence the shortness of the IMP [Space]. There are four stack instructions. hold N Push the number onto the stack copy Duplicate the top item on the stack copy N Copy the nth item on the stack (given by the argument) onto the top of the stack swap Swap the top two items on the stack drop Discard the top item on the stack drop N Slide n items off the stack, keeping the top item Arithmetic (IMP: [Tab][Space]) Arithmetic commands operate on the top two items on the stack, and replace them with the result of the operation. The first item pushed is considered to be left of the operator. add Addition sub Subtraction mul Multiplication div Integer Division mod Modulo Heap Access (IMP: [Tab][Tab]) Heap access commands look at the stack to find the address of items to be stored or retrieved. To store an item, push the address then the value and run the store command. To retrieve an item, push the address and run the retrieve command, which will place the value stored in the location at the top of the stack. save Store load Retrieve Flow Control (IMP: [LF]) Flow control operations are also common. Subroutines are marked by labels, as well as the targets of conditional and unconditional jumps, by which loops can be implemented. Programs must be ended by means of [LF][LF][LF] so that the interpreter can exit cleanly. L: Mark a location in the program call L Call a subroutine goto L Jump unconditionally to a label if=0 L Jump to a label if the top of the stack is zero if<0 L Jump to a label if the top of the stack is negative return End a subroutine and transfer control back to the caller halt End the program I/O (IMP: [Tab][LF]) Finally, we need to be able to interact with the user. There are IO instructions for reading and writing numbers and individual characters. With these, string manipulation routines can be written. The read instructions take the heap address in which to store the result from the top of the stack. print chr Output the character at the top of the stack print int Output the number at the top of the stack input chr Read a character and place it in the location given by the top of the stack input int Read a number and place it in the location given by the top of the stack Question: How would you redesign, rewrite, or rename the previous mnemonics and for what reasons?

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• Authoritative sources about Database vs. Flatfile decision

  - by FastAl

  <tldr>looking for a reference to a book or other undeniably authoritative source that gives reasons when you should choose a database vs. when you should choose other storage methods. I have provided an un-authoritative list of reasons about 2/3 of the way down this post.</tldr> I have a situation at my company where a database is being used where it would be better to use another solution (in this case, an auto-generated piece of source code that contains a static lookup table, searched by binary sort). Normally, a database would be an OK solution even though the problem does not require a database, e.g, none of the elements of ACID are needed, as it is read-only data, updated about every 3-5 years (also requiring other sourcecode changes), and fits in memory, and can be keyed into via binary search (a tad faster than db, but speed is not an issue). The problem is that this code runs on our enterprise server, but is shared with several PC platforms (some disconnected, some use a central DB, etc.), and parts of it are managed by multiple programming units, parts by the DBAs, parts even by mathematicians in another department, etc. These hit their own platform’s version of their databases (containing their own copy of the static data). What happens is that every implementation, every little change, something different goes wrong. There are many other issues as well. I can’t even use a flatfile, because one mode of running on our enterprise server does not have permission to read files (only databases, and of course, its own literal storage, e.g., in-source table). Of course, other parts of the system use databases in proper, less obscure manners; there is no problem with those parts. So why don’t we just change it? I don’t have administrative ability to force a change. But I’m affected because sometimes I have to help fix the problems, but mostly because it causes outages and tons of extra IT time by other programmers and d*mmit that makes me mad! The reason neither management, nor the designers of the system, can see the problem is that they propose a solution that won’t work: increase communication; implement more safeguards and standards; etc. But every time, in a different part of the already-pared-down but still multi-step processes, a few different diligent, hard-working, top performing IT personnel make a unique subtle error that causes it to fail, sometimes after the last round of testing! And in general these are not single-person failures, but understandable miscommunications. And communication at our company is actually better than most. People just don't think that's the case because they haven't dug into the matter. However, I have it on very good word from somebody with extensive formal study of sociology and psychology that the relatively small amount of less-than-proper database usage in this gigantic cross-platform multi-source, multi-language project is bureaucratically un-maintainable. Impossible. No chance. At least with Human Beings in the loop, and it can’t be automated. In addition, the management and developers who could change this, though intelligent and capable, don’t understand the rigidity of this ‘how humans are’ issue, and are not convincible on the matter. The reason putting the static data in sourcecode will solve the problem is, although the solution is less sexy than a database, it would function with no technical drawbacks; and since the sharing of sourcecode already works very well, you basically erase any database-related effort from this section of the project, along with all the drawbacks of it that are causing problems. OK, that’s the background, for the curious. I won’t be able to convince management that this is an unfixable sociological problem, and that the real solution is coding around these limits of human nature, just as you would code around a bug in a 3rd party component that you can’t change. So what I have to do is exploit the unsuitableness of the database solution, and not do it using logic, but rather authority. I am aware of many reasons, and posts on this site giving reasons for one over the other; I’m not looking for lists of reasons like these (although you can add a comment if I've miss a doozy): WHY USE A DATABASE? instead of flatfile/other DB vs. file: if you need... Random Read / Transparent search optimization Advanced / varied / customizable Searching and sorting capabilities Transaction/rollback Locks, semaphores Concurrency control / Shared users Security 1-many/m-m is easier Easy modification Scalability Load Balancing Random updates / inserts / deletes Advanced query Administrative control of design, etc. SQL / learning curve Debugging / Logging Centralized / Live Backup capabilities Cached queries / dvlp & cache execution plans Interleaved update/read Referential integrity, avoid redundant/missing/corrupt/out-of-sync data Reporting (from on olap or oltp db) / turnkey generation tools [Disadvantages:] Important to get right the first time - professional design - but only b/c it's meant to last s/w & h/w cost Usu. over a network, speed issue (best vs. best design vs. local=even then a separate process req's marshalling/netwk layers/inter-p comm) indicies and query processing can stand in the way of simple processing (vs. flatfile) WHY USE FLATFILE: If you only need... Sequential Row processing only Limited usage append only (no reading, no master key/update) Only Update the record you're reading (fixed length recs only) Too big to fit into memory If Local disk / read-ahead network connection Portability / small system Email / cut & Paste / store as document by novice - simple format Low design learning curve but high cost later WHY USE IN-MEMORY/TABLE (tables, arrays, etc.): if you need... Processing a single db/ff record that was imported Known size of data Static data if hardcoding the table Narrow, unchanging use (e.g., one program or proc) -includes a class that will be shared, but encapsulates its data manipulation Extreme speed needed / high transaction frequency Random access - but search is dependent on implementation Following are some other posts about the topic: http://stackoverflow.com/questions/1499239/database-vs-flat-text-file-what-are-some-technical-reasons-for-choosing-one-over http://stackoverflow.com/questions/332825/are-flat-file-databases-any-good http://stackoverflow.com/questions/2356851/database-vs-flat-files http://stackoverflow.com/questions/514455/databases-vs-plain-text/514530 What I’d like to know is if anybody could recommend a hard, authoritative source containing these reasons. I’m looking for a paper book I can buy, or a reputable website with whitepapers about the issue (e.g., Microsoft, IBM), not counting the user-generated content on those sites. This will have a greater change to elicit a change that I’m looking for: less wasted programmer time, and more reliable programs. Thanks very much for your help. You win a prize for reading such a large post!

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• Are their any suggestions for this new assembly language?

  - by Noctis Skytower

  Greetings! Last semester in college, my teacher in the Computer Languages class taught us the esoteric language named Whitespace. In the interest of learning the language better with a very busy schedule (midterms), I wrote an interpreter and assembler in Python. An assembly language was designed to facilitate writing programs easily, and a sample program was written with the given assembly mnemonics. Now that it is summer, a new project has begun with the objective being to rewrite the interpreter and assembler for Whitespace 0.3, with further developments coming afterwards. Since there is so much extra time than before to work on its design, you are presented here with an outline that provides a revised set of mnemonics for the assembly language. This post is marked as a wiki for their discussion. Have you ever had any experience with assembly languages in the past? Were there some instructions that you thought should have been renamed to something different? Did you find yourself thinking outside the box and with a different paradigm than in which the mnemonics were named? If you can answer yes to any of those questions, you are most welcome here. Subjective answers are appreciated! Stack Manipulation (IMP: [Space]) Stack manipulation is one of the more common operations, hence the shortness of the IMP [Space]. There are four stack instructions. hold N Push the number onto the stack copy Duplicate the top item on the stack copy N Copy the nth item on the stack (given by the argument) onto the top of the stack swap Swap the top two items on the stack drop Discard the top item on the stack drop N Slide n items off the stack, keeping the top item Arithmetic (IMP: [Tab][Space]) Arithmetic commands operate on the top two items on the stack, and replace them with the result of the operation. The first item pushed is considered to be left of the operator. add Addition sub Subtraction mul Multiplication div Integer Division mod Modulo Heap Access (IMP: [Tab][Tab]) Heap access commands look at the stack to find the address of items to be stored or retrieved. To store an item, push the address then the value and run the store command. To retrieve an item, push the address and run the retrieve command, which will place the value stored in the location at the top of the stack. save Store load Retrieve Flow Control (IMP: [LF]) Flow control operations are also common. Subroutines are marked by labels, as well as the targets of conditional and unconditional jumps, by which loops can be implemented. Programs must be ended by means of [LF][LF][LF] so that the interpreter can exit cleanly. L: Mark a location in the program call L Call a subroutine goto L Jump unconditionally to a label if=0 L Jump to a label if the top of the stack is zero if<0 L Jump to a label if the top of the stack is negative return End a subroutine and transfer control back to the caller exit End the program I/O (IMP: [Tab][LF]) Finally, we need to be able to interact with the user. There are IO instructions for reading and writing numbers and individual characters. With these, string manipulation routines can be written. The read instructions take the heap address in which to store the result from the top of the stack. print chr Output the character at the top of the stack print int Output the number at the top of the stack input chr Read a character and place it in the location given by the top of the stack input int Read a number and place it in the location given by the top of the stack Question: How would you redesign, rewrite, or rename the previous mnemonics and for what reasons?

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• Are there any suggestions for these new assembly mnemonics?

  - by Noctis Skytower

  Greetings! Last semester in college, my teacher in the Computer Languages class taught us the esoteric language named Whitespace. In the interest of learning the language better with a very busy schedule (midterms), I wrote an interpreter and assembler in Python. An assembly language was designed to facilitate writing programs easily, and a sample program was written with the given assembly mnemonics. Now that it is summer, a new project has begun with the objective being to rewrite the interpreter and assembler for Whitespace 0.3, with further developments coming afterwards. Since there is so much extra time than before to work on its design, you are presented here with an outline that provides a revised set of mnemonics for the assembly language. This post is marked as a wiki for their discussion. Have you ever had any experience with assembly languages in the past? Were there some instructions that you thought should have been renamed to something different? Did you find yourself thinking outside the box and with a different paradigm than in which the mnemonics were named? If you can answer yes to any of those questions, you are most welcome here. Subjective answers are appreciated! Stack Manipulation (IMP: [Space]) Stack manipulation is one of the more common operations, hence the shortness of the IMP [Space]. There are four stack instructions. hold N Push the number onto the stack copy Duplicate the top item on the stack copy N Copy the nth item on the stack (given by the argument) onto the top of the stack swap Swap the top two items on the stack drop Discard the top item on the stack drop N Slide n items off the stack, keeping the top item Arithmetic (IMP: [Tab][Space]) Arithmetic commands operate on the top two items on the stack, and replace them with the result of the operation. The first item pushed is considered to be left of the operator. add Addition sub Subtraction mul Multiplication div Integer Division mod Modulo Heap Access (IMP: [Tab][Tab]) Heap access commands look at the stack to find the address of items to be stored or retrieved. To store an item, push the address then the value and run the store command. To retrieve an item, push the address and run the retrieve command, which will place the value stored in the location at the top of the stack. save Store load Retrieve Flow Control (IMP: [LF]) Flow control operations are also common. Subroutines are marked by labels, as well as the targets of conditional and unconditional jumps, by which loops can be implemented. Programs must be ended by means of [LF][LF][LF] so that the interpreter can exit cleanly. L: Mark a location in the program call L Call a subroutine goto L Jump unconditionally to a label if=0 L Jump to a label if the top of the stack is zero if<0 L Jump to a label if the top of the stack is negative return End a subroutine and transfer control back to the caller halt End the program I/O (IMP: [Tab][LF]) Finally, we need to be able to interact with the user. There are IO instructions for reading and writing numbers and individual characters. With these, string manipulation routines can be written. The read instructions take the heap address in which to store the result from the top of the stack. print chr Output the character at the top of the stack print int Output the number at the top of the stack input chr Read a character and place it in the location given by the top of the stack input int Read a number and place it in the location given by the top of the stack Question: How would you redesign, rewrite, or rename the previous mnemonics and for what reasons?

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• Listview with objectdatasource Delete not working

  - by Radhi

  Hello, i have one Listview in my Usercontrol & 1 objectdatasource binded with the ListView. now in objectdatasource's Deletemethod i have taken businessobject as argument but at runtime i am not getting value in my businessobject's properties... i also tried to use "Bind" instead of "eval" in ItemTemplate. but not getting any value at runtime in my DeleteMethod provided in objectdatasource's Deletecommand... can anybody help to know weather i am mising anything or what? my Listview's ItemTemplate <ItemTemplate> <asp:HiddenField ID="hidUserAchievementInfoId" runat="server" Value='<%# Bind("UserAchievementInfoId") %>' /> <asp:HiddenField ID="hidUserIdField" runat="server" Value='<%# Bind("UserId") %>' /> <tr> <td class="style1"> <asp:Label ID="AwardLabel" runat="server" Text="Award "></asp:Label> </td> <td> <asp:Label ID="lblAward" runat="server" Text='<%# Bind("Awards") %>'></asp:Label> </td> </tr> <tr> <td class="style1"> <asp:Label ID="FieldofAwardLabel" runat="server" Text="Field of Award "></asp:Label> </td> <td> <asp:Label ID="lblFieldofAward" runat="server" Text='<%# Bind("FieldofAward") %>'></asp:Label> </td> </tr> <tr> <td class="style1"> <asp:Label ID="TournamentLabel" runat="server" Text="Tournament "></asp:Label> </td> <td> <asp:Label ID="lblTournament" runat="server" Text='<%# Bind("Tournament") %>'></asp:Label> </td> </tr> <tr> <td class="style1"> <asp:Label ID="AwardYearLabel" runat="server" Text="Award Year "></asp:Label> </td> <td> <asp:Label ID="AwardYear" runat="server" Text='<%# Bind("AwardYear") %>'></asp:Label> </td> </tr> <tr> <td class="style1"> <asp:Label ID="AwardDescriptionLabel" runat="server" Text="Description "></asp:Label> </td> <td> <asp:Label ID="lblAwardDescription" runat="server" Text='<%# Bind("AwardDescription") %>'></asp:Label> </td> </tr> <tr> <td class="style1"> <asp:LinkButton ID="EditButton" runat="server" CommandName="Edit" Text="Edit"></asp:LinkButton> </td> <td> <asp:LinkButton ID="DeleteButton" runat="server" CommandName="Delete" Text="Delete"></asp:LinkButton> </td> </tr> </ItemTemplate> Delete Method used in objectdata source's Deletecommand public void DeleteUserAchievementInfo(UserAchivementInfoBO BOInstance) { try { Int64 UserAchievementInfoId=BOInstance.UserAchievementInfoId objUserBasicInfoServiceClient.DeleteUserAchievementInfo(UserAchievementInfoId); } catch (Exception ex) { HandleException.LogError(ex); } }

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• Trying to write a std::iterator : Compilation error

  - by Naveen

  I am trying to write an std::iterator for the CArray<Type,ArgType> MFC class. This is what I have done till now: template <class Type, class ArgType> class CArrayIterator : public std::iterator<std::random_access_iterator_tag, ArgType> { public: CArrayIterator(CArray<Type,ArgType>& array_in, int index_in = 0) : m_pArray(&array_in), m_index(index_in) { } void operator++() { ++m_index; } void operator++(int) { ++m_index; } void operator--() { --m_index; } void operator--(int) { --m_index; } void operator+=(int n) { m_index += n; } void operator-=(int n) { m_index -= n; } typename ArgType operator*() const{ return m_pArray->GetAt(m_index); } typename ArgType operator->() const { return m_pArray->GetAt(m_index); } bool operator==(const CArrayIterator& other) const { return m_pArray == other.m_pArray && m_index == other.m_index; } bool operator!=(const CArrayIterator& other) const { return ! (operator==(other)); } private: CArray<Type,ArgType>* m_pArray; int m_index; }; I also provided two helper functions to create the iterators like this: template<class Type, class ArgType> CArrayIterator<Type,ArgType> make_begin(CArray<Type,ArgType>& array_in) { return CArrayIterator<Type,ArgType>(array_in, 0); } template<class Type, class ArgType> CArrayIterator<Type,ArgType> make_end(CArray<Type,ArgType>& array_in) { return CArrayIterator<Type,ArgType>(array_in, array_in.GetSize()); } To test the code, I wrote a simple class A and tried to use it like this: class A { public: A(int n): m_i(n) { } int get() const { return m_i; } private: int m_i; }; struct Test { void operator()(A* p) { std::cout<<p->get()<<"\n"; } }; int main(int argc, char **argv) { CArray<A*, A*> b; b.Add(new A(10)); b.Add(new A(20)); std::for_each(make_begin(b), make_end(b), Test()); return 0; } But when I compile this code, I get the following error: Error 4 error C2784: 'bool std::operator <(const std::_Tree<_Traits &,const std::_Tree<_Traits &)' : could not deduce template argument for 'const std::_Tree<_Traits &' from 'CArrayIterator' C:\Program Files\Microsoft Visual Studio 9.0\VC\include\xutility 1564 Vs8Console Can anybody throw some light on what I am doing wrong and how it can be corrected? I am using VC9 compiler if it matters.

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• Why isn't my algorithm for find the biggest and smallest inputs working?

  - by Matt Ellen

  I have started a new job, and with it comes a new language: Ironpython. Thankfully a good language :D Before starting I got to grips with Python on the whole, but that was only a week's worth of learning. Now I'm writing actual code. I've been charged with writing an algorithm that finds the best input parameter to collect data with. The basic algorithm is (as I've been instructed): Set the input parameter to a good guess Start collecting data When data is available stop collecting find the highest point If the point before this (i.e. for the previous parameter value) was higher and the point before that was lower then we've found the max otherwise the input parameter is increased by the initial guess. goto 2 If the max is found then the min needs to be found. To do this the algorithm carries on increasing the input, but by 1/10 of the max, until the current point is greater than the previous point and the point before that is also greater. Once the min is found then the algorithm stops. Currently I have a simplified data generator outputting the sin of the input, so that I know that the min value should be PI and the max value should be PI/2 The main Python code looks like this (don't worry, this is just for my edification, I don't write real code like this): import sys sys.path.append(r"F:\Programming Source\C#\PythonHelp\PythonHelp\bin\Debug") import clr clr.AddReferenceToFile("PythonHelpClasses.dll") import PythonHelpClasses from PHCStruct import Helper from System import Math helper = Helper() def run(): b = PythonHelpClasses.Executor() a = PythonHelpClasses.HasAnEvent() b.Input = 0.0 helper.__init__() def AnEventHandler(e): b.Stop() h = helper h.lastLastVal, h.lastVal, h.currentVal = h.lastVal, h.currentVal, e.Number if h.lastLastVal < h.lastVal and h.currentVal < h.lastVal and h.NotPast90: h.NotPast90 = False h.bestInput = h.lastInput inputInc = 0.0 if h.NotPast90: inputInc = Math.PI/10.0 else: inputInc = h.bestInput/10.0 if h.lastLastVal > h.lastVal and h.currentVal > h.lastVal and h.NotPast180: h.NotPast180 = False if h.NotPast180: h.lastInput, b.Input = b.Input, b.Input + inputInc b.Start(a) else: print "Best input:", h.bestInput print "Last input:", h.lastInput b.Stop() a.AnEvent += AnEventHandler b.Start(a) PHCStruct.py: class Helper(): def __init__(self): self.currentVal = 0 self.lastVal = 0 self.lastLastVal = 0 self.NotPast90 = True self.NotPast180 = True self.bestInput = 0 self.lastInput = 0 PythonHelpClasses has two small classes I wrote in C# before I realised how to do it in Ironpython. Executor runs a delegate asynchronously while it's running member is true. The important code: public void Start(HasAnEvent hae) { running = true; RunDelegate r = new RunDelegate(hae.UpdateNumber); AsyncCallback ac = new AsyncCallback(UpdateDone); IAsyncResult ar = r.BeginInvoke(Input, ac, null); } public void Stop() { running = false; } public void UpdateDone(IAsyncResult ar) { RunDelegate r = (RunDelegate)((AsyncResult)ar).AsyncDelegate; r.EndInvoke(ar); if (running) { AsyncCallback ac = new AsyncCallback(UpdateDone); IAsyncResult ar2 = r.BeginInvoke(Input, ac, null); } } HasAnEvent has a function that generates the sin of its input and fires an event with that result as its argument. i.e.: public void UpdateNumber(double val) { AnEventArgs e = new AnEventArgs(Math.Sin(val)); System.Threading.Thread.Sleep(1000); if (null != AnEvent) { AnEvent(e); } } The sleep is in there just to slow things down a bit. The problem I am getting is that the algorithm is not coming up with the best input being PI/2 and the final input being PI, but I can't see why. Also the best and final inputs are different each time I run the programme. Can anyone see why? Also when the algorithm terminates the best and final inputs are printed to the screen multiple times, not just once. Can someone explain why?

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• Function signature-like expressions as C++ template arguments

  - by Jeff Lee

  I was looking at Don Clugston's FastDelegate mini-library and noticed a weird syntactical trick with the following structure: TemplateClass< void( int, int ) > Object; It almost appears as if a function signature is being used as an argument to a template instance declaration. This technique (whose presence in FastDelegate is apparently due to one Jody Hagins) was used to simplify the declaration of template instances with a semi-arbitrary number of template parameters. To wit, it allowed this something like the following: // A template with one parameter template<typename _T1> struct Object1 { _T1 m_member1; }; // A template with two parameters template<typename _T1, typename _T2> struct Object2 { _T1 m_member1; _T2 m_member2; }; // A forward declaration template<typename _Signature> struct Object; // Some derived types using "function signature"-style template parameters template<typename _Dummy, typename _T1> struct Object<_Dummy(_T1)> : public Object1<_T1> {}; template<typename _Dummy, typename _T1, typename _T2> struct Object<_Dummy(_T1, _T2)> : public Object2<_T1, _T2> {}; // A. "Vanilla" object declarations Object1<int> IntObjectA; Object2<int, char> IntCharObjectA; // B. Nifty, but equivalent, object declarations typedef void UnusedType; Object< UnusedType(int) > IntObjectB; Object< UnusedType(int, char) > IntCharObjectB; // C. Even niftier, and still equivalent, object declarations #define DeclareObject( ... ) Object< UnusedType( __VA_ARGS__ ) > DeclareObject( int ) IntObjectC; DeclareObject( int, char ) IntCharObjectC; Despite the real whiff of hackiness, I find this kind of spoofy emulation of variadic template arguments to be pretty mind-blowing. The real meat of this trick seems to be the fact that I can pass textual constructs like "Type1(Type2, Type3)" as arguments to templates. So here are my questions: How exactly does the compiler interpret this construct? Is it a function signature? Or, is it just a text pattern with parentheses in it? If the former, then does this imply that any arbitrary function signature is a valid type as far as the template processor is concerned? A follow-up question would be that since the above code sample is valid code, why doesn't the C++ standard just allow you to do something like the following, which is does not compile? template<typename _T1> struct Object { _T1 m_member1; }; // Note the class identifier is also "Object" template<typename _T1, typename _T2> struct Object { _T1 m_member1; _T2 m_member2; }; Object<int> IntObject; Object<int, char> IntCharObject;

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• How do I prove I should put a table of values in source code instead of a database table?

  - by FastAl

  <tldr>looking for a reference to a book or other undeniably authoritative source that gives reasons when you should choose a database vs. when you should choose other storage methods. I have provided an un-authoritative list of reasons about 2/3 of the way down this post.</tldr> I have a situation at my company where a database is being used where it would be better to use another solution (in this case, an auto-generated piece of source code that contains a static lookup table, searched by binary sort). Normally, a database would be an OK solution even though the problem does not require a database, e.g, none of the elements of ACID are needed, as it is read-only data, updated about every 3-5 years (also requiring other sourcecode changes), and fits in memory, and can be keyed into via binary search (a tad faster than db, but speed is not an issue). The problem is that this code runs on our enterprise server, but is shared with several PC platforms (some disconnected, some use a central DB, etc.), and parts of it are managed by multiple programming units, parts by the DBAs, parts even by mathematicians in another department, etc. These hit their own platform’s version of their databases (containing their own copy of the static data). What happens is that every implementation, every little change, something different goes wrong. There are many other issues as well. I can’t even use a flatfile, because one mode of running on our enterprise server does not have permission to read files (only databases, and of course, its own literal storage, e.g., in-source table). Of course, other parts of the system use databases in proper, less obscure manners; there is no problem with those parts. So why don’t we just change it? I don’t have administrative ability to force a change. But I’m affected because sometimes I have to help fix the problems, but mostly because it causes outages and tons of extra IT time by other programmers and d*mmit that makes me mad! The reason neither management, nor the designers of the system, can see the problem is that they propose a solution that won’t work: increase communication; implement more safeguards and standards; etc. But every time, in a different part of the already-pared-down but still multi-step processes, a few different diligent, hard-working, top performing IT personnel make a unique subtle error that causes it to fail, sometimes after the last round of testing! And in general these are not single-person failures, but understandable miscommunications. And communication at our company is actually better than most. People just don't think that's the case because they haven't dug into the matter. However, I have it on very good word from somebody with extensive formal study of sociology and psychology that the relatively small amount of less-than-proper database usage in this gigantic cross-platform multi-source, multi-language project is bureaucratically un-maintainable. Impossible. No chance. At least with Human Beings in the loop, and it can’t be automated. In addition, the management and developers who could change this, though intelligent and capable, don’t understand the rigidity of this ‘how humans are’ issue, and are not convincible on the matter. The reason putting the static data in sourcecode will solve the problem is, although the solution is less sexy than a database, it would function with no technical drawbacks; and since the sharing of sourcecode already works very well, you basically erase any database-related effort from this section of the project, along with all the drawbacks of it that are causing problems. OK, that’s the background, for the curious. I won’t be able to convince management that this is an unfixable sociological problem, and that the real solution is coding around these limits of human nature, just as you would code around a bug in a 3rd party component that you can’t change. So what I have to do is exploit the unsuitableness of the database solution, and not do it using logic, but rather authority. I am aware of many reasons, and posts on this site giving reasons for one over the other; I’m not looking for lists of reasons like these (although you can add a comment if I've miss a doozy): WHY USE A DATABASE? instead of flatfile/other DB vs. file: if you need... Random Read / Transparent search optimization Advanced / varied / customizable Searching and sorting capabilities Transaction/rollback Locks, semaphores Concurrency control / Shared users Security 1-many/m-m is easier Easy modification Scalability Load Balancing Random updates / inserts / deletes Advanced query Administrative control of design, etc. SQL / learning curve Debugging / Logging Centralized / Live Backup capabilities Cached queries / dvlp & cache execution plans Interleaved update/read Referential integrity, avoid redundant/missing/corrupt/out-of-sync data Reporting (from on olap or oltp db) / turnkey generation tools [Disadvantages:] Important to get right the first time - professional design - but only b/c it's meant to last s/w & h/w cost Usu. over a network, speed issue (best vs. best design vs. local=even then a separate process req's marshalling/netwk layers/inter-p comm) indicies and query processing can stand in the way of simple processing (vs. flatfile) WHY USE FLATFILE: If you only need... Sequential Row processing only Limited usage append only (no reading, no master key/update) Only Update the record you're reading (fixed length recs only) Too big to fit into memory If Local disk / read-ahead network connection Portability / small system Email / cut & Paste / store as document by novice - simple format Low design learning curve but high cost later WHY USE IN-MEMORY/TABLE (tables, arrays, etc.): if you need... Processing a single db/ff record that was imported Known size of data Static data if hardcoding the table Narrow, unchanging use (e.g., one program or proc) -includes a class that will be shared, but encapsulates its data manipulation Extreme speed needed / high transaction frequency Random access - but search is dependent on implementation Following are some other posts about the topic: http://stackoverflow.com/questions/1499239/database-vs-flat-text-file-what-are-some-technical-reasons-for-choosing-one-over http://stackoverflow.com/questions/332825/are-flat-file-databases-any-good http://stackoverflow.com/questions/2356851/database-vs-flat-files http://stackoverflow.com/questions/514455/databases-vs-plain-text/514530 What I’d like to know is if anybody could recommend a hard, authoritative source containing these reasons. I’m looking for a paper book I can buy, or a reputable website with whitepapers about the issue (e.g., Microsoft, IBM), not counting the user-generated content on those sites. This will have a greater change to elicit a change that I’m looking for: less wasted programmer time, and more reliable programs. Thanks very much for your help. You win a prize for reading such a large post!

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• Calling system commands from Perl

  - by Dan J

  In an older version of our code, we called out from Perl to do an LDAP search as follows: # Pass the base DN in via the ldapsearch-specific environment variable # (rather than as the "-b" paramater) to avoid problems of shell # interpretation of special characters in the DN. $ENV{LDAP_BASEDN} = $ldn; $lcmd = "ldapsearch -x -T -1 -h $gLdapServer" . <snip> " > $lworkfile 2>&1"; system($lcmd); if (($? != 0) || (! -e "$lworkfile")) { # Handle the error } The code above would result in a successful LDAP search, and the output of that search would be in the file $lworkfile. Unfortunately, we recently reconfigured openldap on this server so that a "BASE DC=" is specified in /etc/openldap/ldap.conf and /etc/ldap.conf. That change seems to mean ldapsearch ignores the LDAP_BASEDN environment variable, and so my ldapsearch fails. I've tried a couple of different fixes but without success so far: (1) I tried going back to using the "-b" argument to ldapsearch, but escaping the shell metacharacters. I started writing the escaping code: my $ldn_escaped = $ldn; $ldn_escaped =~ s/\/\\/g; $ldn_escaped =~ s/`/\`/g; $ldn_escaped =~ s/$/\$/g; $ldn_escaped =~ s/"/\"/g; That threw up some Perl errors because I haven't escaped those regexes properly in Perl (the line number matches the regex with the backticks in). Backticks found where operator expected at /tmp/mycommand line 404, at end of line At the same time I started to doubt this approach and looked for a better one. (2) I then saw some Stackoverflow questions (here and here) that suggested a better solution. Here's the code: print("Processing..."); # Pass the arguments to ldapsearch by invoking open() with an array. # This ensures the shell does NOT interpret shell metacharacters. my(@cmd_args) = ("-x", "-T", "-1", "-h", "$gLdapPool", "-b", "$ldn", <snip> ); $lcmd = "ldapsearch"; open my $lldap_output, "-|", $lcmd, @cmd_args; while (my $lline = <$lldap_output>) { # I can parse the contents of my file fine } $lldap_output->close; The two problems I am having with approach (2) are: a) Calling open or system with an array of arguments does not let me pass > $lworkfile 2>&1 to the command, so I can't stop the ldapsearch output being sent to screen, which makes my output look ugly: Processing...ldap_bind: Success (0) additional info: Success b) I can't figure out how to choose which location (i.e. path and file name) to the file handle passed to open, i.e. I don't know where $lldap_output is. Can I move/rename it, or inspect it to find out where it is (or is it not actually saved to disk)? Based on the problems with (2), this makes me think I should return back to approach (1), but I'm not quite sure how to

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• Odd behavior when recursively building a return type for variadic functions

  - by Dennis Zickefoose

  This is probably going to be a really simple explanation, but I'm going to give as much backstory as possible in case I'm wrong. Advanced apologies for being so verbose. I'm using gcc4.5, and I realize the c++0x support is still somewhat experimental, but I'm going to act on the assumption that there's a non-bug related reason for the behavior I'm seeing. I'm experimenting with variadic function templates. The end goal was to build a cons-list out of std::pair. It wasn't meant to be a custom type, just a string of pair objects. The function that constructs the list would have to be in some way recursive, with the ultimate return value being dependent on the result of the recursive calls. As an added twist, successive parameters are added together before being inserted into the list. So if I pass [1, 2, 3, 4, 5, 6] the end result should be {1+2, {3+4, 5+6}}. My initial attempt was fairly naive. A function, Build, with two overloads. One took two identical parameters and simply returned their sum. The other took two parameters and a parameter pack. The return value was a pair consisting of the sum of the two set parameters, and the recursive call. In retrospect, this was obviously a flawed strategy, because the function isn't declared when I try to figure out its return type, so it has no choice but to resolve to the non-recursive version. That I understand. Where I got confused was the second iteration. I decided to make those functions static members of a template class. The function calls themselves are not parameterized, but instead the entire class is. My assumption was that when the recursive function attempts to generate its return type, it would instantiate a whole new version of the structure with its own static function, and everything would work itself out. The result was: "error: no matching function for call to BuildStruct<double, double, char, char>::Go(const char&, const char&)" The offending code: static auto Go(const Type& t0, const Type& t1, const Types&... rest) -> std::pair<Type, decltype(BuildStruct<Types...>::Go(rest...))> My confusion comes from the fact that the parameters to BuildStruct should always be the same types as the arguments sent to BuildStruct::Go, but in the error code Go is missing the initial two double parameters. What am I missing here? If my initial assumption about how the static functions would be chosen was incorrect, why is it trying to call the wrong function rather than just not finding a function at all? It seems to just be mixing types willy-nilly, and I just can't come up with an explanation as to why. If I add additional parameters to the initial call, it always burrows down to that last step before failing, so presumably the recursion itself is at least partially working. This is in direct contrast to the initial attempt, which always failed to find a function call right away. Ultimately, I've gotten past the problem, with a fairly elegant solution that hardly resembles either of the first two attempts. So I know how to do what I want to do. I'm looking for an explanation for the failure I saw. Full code to follow since I'm sure my verbal description was insufficient. First some boilerplate, if you feel compelled to execute the code and see it for yourself. Then the initial attempt, which failed reasonably, then the second attempt, which did not. #include <iostream> using std::cout; using std::endl; #include <utility> template<typename T1, typename T2> std::ostream& operator <<(std::ostream& str, const std::pair<T1, T2>& p) { return str << "[" << p.first << ", " << p.second << "]"; } //Insert code here int main() { Execute(5, 6, 4.3, 2.2, 'c', 'd'); Execute(5, 6, 4.3, 2.2); Execute(5, 6); return 0; } Non-struct solution: template<typename Type> Type BuildFunction(const Type& t0, const Type& t1) { return t0 + t1; } template<typename Type, typename... Rest> auto BuildFunction(const Type& t0, const Type& t1, const Rest&... rest) -> std::pair<Type, decltype(BuildFunction(rest...))> { return std::pair<Type, decltype(BuildFunction(rest...))> (t0 + t1, BuildFunction(rest...)); } template<typename... Types> void Execute(const Types&... t) { cout << BuildFunction(t...) << endl; } Resulting errors: test.cpp: In function 'void Execute(const Types& ...) [with Types = {int, int, double, double, char, char}]': test.cpp:33:35: instantiated from here test.cpp:28:3: error: no matching function for call to 'BuildFunction(const int&, const int&, const double&, const double&, const char&, const char&)' Struct solution: template<typename... Types> struct BuildStruct; template<typename Type> struct BuildStruct<Type, Type> { static Type Go(const Type& t0, const Type& t1) { return t0 + t1; } }; template<typename Type, typename... Types> struct BuildStruct<Type, Type, Types...> { static auto Go(const Type& t0, const Type& t1, const Types&... rest) -> std::pair<Type, decltype(BuildStruct<Types...>::Go(rest...))> { return std::pair<Type, decltype(BuildStruct<Types...>::Go(rest...))> (t0 + t1, BuildStruct<Types...>::Go(rest...)); } }; template<typename... Types> void Execute(const Types&... t) { cout << BuildStruct<Types...>::Go(t...) << endl; } Resulting errors: test.cpp: In instantiation of 'BuildStruct<int, int, double, double, char, char>': test.cpp:33:3: instantiated from 'void Execute(const Types& ...) [with Types = {int, int, double, double, char, char}]' test.cpp:38:41: instantiated from here test.cpp:24:15: error: no matching function for call to 'BuildStruct<double, double, char, char>::Go(const char&, const char&)' test.cpp:24:15: note: candidate is: static std::pair<Type, decltype (BuildStruct<Types ...>::Go(BuildStruct<Type, Type, Types ...>::Go::rest ...))> BuildStruct<Type, Type, Types ...>::Go(const Type&, const Type&, const Types& ...) [with Type = double, Types = {char, char}, decltype (BuildStruct<Types ...>::Go(BuildStruct<Type, Type, Types ...>::Go::rest ...)) = char] test.cpp: In function 'void Execute(const Types& ...) [with Types = {int, int, double, double, char, char}]': test.cpp:38:41: instantiated from here test.cpp:33:3: error: 'Go' is not a member of 'BuildStruct<int, int, double, double, char, char>'

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• Monorail - Form submission using GET instead of POST

  - by Septih

  Hello, I'm writing some additions to a Castle MonoRail based site involving an Add and an Edit form. The add form works fine and uses POST but the edit form uses GET. The only major difference I can see is that the edit method is called with the Id of the object being edited in the query string. When the submit button is pressed on the edit form, the only argument passed is this object Id again. Here is the code for the edit form: <form action="edit.ashx" method="post"> <h3>Coupon Description</h3> <textarea name="comments" width="200">$comments</textarea> <br/><br/> <h3>Coupon Actions</h3> <br/> <div>Give Stories</div> <ul class="checklist" style="overflow:auto;height:144px;width:100%"> #foreach ($story in $stories.Values) <li> <label> #set ($associated = "") #foreach($storyId in $storyIds) #if($story.Id == $storyId) #set($associated = " checked='true'") #end #end <input type="checkbox" name="chk_${story.Id}" id="chk_${story.Id}" value="true" class="checkbox" $associated/> $story.Name </label> </li> #end </ul> <br/><br/> <div>Give Credit Amount</div> <input type="text" name="credit" value="$credit" /> <br/><br/> <h3>Coupon Uses</h3> <input type="checkbox" name="multi" #if($multi) checked="true" #end /> Multi-Use Coupon?<br/><br/> <b>OR</b> <br/> <br/> Number of Uses per Coupon: <input type="text" name="uses" value="$uses" /> <br/> <input type="submit" name="Save" /> </form> The differences between this and the add form is the velocity stuff to do with association and the values of the inputs being from the PropertyBag. The Method dealing with this on the controller starts like this: public void Edit(int id) { Coupon coupon = Coupon.GetRepository(User.Site.Id).FindById(id).Value; if(coupon == null) { RedirectToReferrer(); return; } IFutureQueryOfList<Story> stories = Story.GetRepository(User.Site.Id).OnlyReturnEnabled().FindAll("Name", true); if (Params["Save"] == null) { ... } } It reliably gets called but a breakpoint on the Params["Save"] lets me see that the HttpMethod is "GET" and the only arguments passed (In the Form and the Request) are the object Id and additional HTTP headers. At the end of the day I'm not that familiar with MonoRail and this may be a stupid mistake on my behalf, but I would very much appreciate being made a fool out of if it fixes the problem! :) Thanks

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• How do I use constructor dependency injection to supply Models from a collection to their ViewModels

  - by GraemeF

  I'm using constructor dependency injection in my WPF application and I keep running into the following pattern, so would like to get other people's opinion on it and hear about alternative solutions. The goal is to wire up a hierarchy of ViewModels to a similar hierarchy of Models, so that the responsibility for presenting the information in each model lies with its own ViewModel implementation. (The pattern also crops up under other circumstances but MVVM should make for a good example.) Here's a simplified example. Given that I have a model that has a collection of further models: public interface IPerson { IEnumerable<IAddress> Addresses { get; } } public interface IAddress { } I would like to mirror this hierarchy in the ViewModels so that I can bind a ListBox (or whatever) to a collection in the Person ViewModel: public interface IPersonViewModel { ObservableCollection<IAddressViewModel> Addresses { get; } void Initialize(); } public interface IAddressViewModel { } The child ViewModel needs to present the information from the child Model, so it's injected via the constructor: public class AddressViewModel : IAddressViewModel { private readonly IAddress _address; public AddressViewModel(IAddress address) { _address = address; } } The question is, what is the best way to supply the child Model to the corresponding child ViewModel? The example is trivial, but in a typical real case the ViewModels have more dependencies - each of which has its own dependencies (and so on). I'm using Unity 1.2 (although I think the question is relevant across the other IoC containers), and I am using Caliburn's view strategies to automatically find and wire up the appropriate View to a ViewModel. Here is my current solution: The parent ViewModel needs to create a child ViewModel for each child Model, so it has a factory method added to its constructor which it uses during initialization: public class PersonViewModel : IPersonViewModel { private readonly Func<IAddress, IAddressViewModel> _addressViewModelFactory; private readonly IPerson _person; public PersonViewModel(IPerson person, Func<IAddress, IAddressViewModel> addressViewModelFactory) { _addressViewModelFactory = addressViewModelFactory; _person = person; Addresses = new ObservableCollection<IAddressViewModel>(); } public ObservableCollection<IAddressViewModel> Addresses { get; private set; } public void Initialize() { foreach (IAddress address in _person.Addresses) Addresses.Add(_addressViewModelFactory(address)); } } A factory method that satisfies the Func<IAddress, IAddressViewModel> interface is registered with the main UnityContainer. The factory method uses a child container to register the IAddress dependency that is required by the ViewModel and then resolves the child ViewModel: public class Factory { private readonly IUnityContainer _container; public Factory(IUnityContainer container) { _container = container; } public void RegisterStuff() { _container.RegisterInstance<Func<IAddress, IAddressViewModel>>(CreateAddressViewModel); } private IAddressViewModel CreateAddressViewModel(IAddress model) { IUnityContainer childContainer = _container.CreateChildContainer(); childContainer.RegisterInstance(model); return childContainer.Resolve<IAddressViewModel>(); } } Now, when the PersonViewModel is initialized, it loops through each Address in the Model and calls CreateAddressViewModel() (which was injected via the Func<IAddress, IAddressViewModel> argument). CreateAddressViewModel() creates a temporary child container and registers the IAddress model so that when it resolves the IAddressViewModel from the child container the AddressViewModel gets the correct instance injected via its constructor. This seems to be a good solution to me as the dependencies of the ViewModels are very clear and they are easily testable and unaware of the IoC container. On the other hand, performance is OK but not great as a lot of temporary child containers can be created. Also I end up with a lot of very similar factory methods. Is this the best way to inject the child Models into the child ViewModels with Unity? Is there a better (or faster) way to do it in other IoC containers, e.g. Autofac? How would this problem be tackled with MEF, given that it is not a traditional IoC container but is still used to compose objects?

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• Trying to configure HWIC-3G-HSPA

  - by user1174838

  I'm trying to configure a couple of Cisco 1941 routes. The are both identical routers. Each as a HWIC-1T (Smart Serial interface) and a HWIC-3G-HSPA 3G interface. These routers are to be sent to remote sites. We have connectivity to one of the sites but if remote site A gors down we lose connectivity to remote site B. The HWIC-1T is the primary WAN interface using frame relay joining the two remote sites We want the HWIC-3G-HSPA to be usable for direct connectivity from head office to remote site B, and also the HWIC-3G-HSPA is do be used for comms between the remote sites when the frame relay is down (happens quite a bit). I initialy tried to do dynamic routing using EIGRP however in my lab setup of laptop - 1941 - 1941 - laptop, I was unable to get end to end connectivity. I later settled on static routing and have got end to end connectivity but only over frame relay, not the HWIC-3G-HSPA. The sanitized running config for remote site A: version 15.1 service tcp-keepalives-in service tcp-keepalives-out service timestamps debug datetime msec service timestamps log datetime msec service password-encryption service udp-small-servers service tcp-small-servers ! hostname remoteA ! boot-start-marker boot-end-marker ! ! logging buffered 51200 warnings enable secret 5 censored ! no aaa new-model clock timezone wst 8 0 ! no ipv6 cef ip source-route ip cef ! ip domain name yourdomain.com multilink bundle-name authenticated ! chat-script gsm "" "ATDT*98*1#" TIMEOUT 30 "CONNECT" ! username admin privilege 15 secret 5 censored ! controller Cellular 0/1 ! interface Embedded-Service-Engine0/0 no ip address shutdown ! interface GigabitEthernet0/0 ip address 192.168.2.5 255.255.255.0 duplex auto speed auto ! interface GigabitEthernet0/1 no ip address shutdown duplex auto speed auto ! interface Serial0/0/0 ip address 10.1.1.2 255.255.255.252 encapsulation frame-relay cdp enable frame-relay interface-dlci 16 frame-relay lmi-type ansi ! interface Cellular0/1/0 ip address negotiated encapsulation ppp dialer in-band dialer idle-timeout 2147483 dialer string gsm dialer-group 1 async mode interactive ppp chap hostname censored ppp chap password 7 censored cdp enable ! interface Cellular0/1/1 no ip address encapsulation ppp ! interface Dialer0 no ip address ! ip forward-protocol nd ! no ip http server no ip http secure-server ! ip route 0.0.0.0 0.0.0.0 Serial0/0/0 210 permanent ip route 0.0.0.0 0.0.0.0 Cellular0/1/0 220 permanent ip route 172.31.2.0 255.255.255.0 Cellular0/1/0 permanent ip route 192.168.3.0 255.255.255.0 10.1.1.1 permanent ip route 192.168.3.0 255.255.255.0 Cellular0/1/0 210 permanent ! access-list 1 permit any dialer-list 1 protocol ip list 1 ! control-plane ! line con 0 logging synchronous login local line aux 0 line 2 no activation-character no exec transport preferred none transport input all transport output pad telnet rlogin lapb-ta mop udptn v120 ssh stopbits 1 line 0/1/0 exec-timeout 0 0 script dialer gsm login modem InOut no exec transport input all rxspeed 7200000 txspeed 5760000 line 0/1/1 no exec rxspeed 7200000 txspeed 5760000 line vty 0 4 access-class 23 in privilege level 15 password 7 censored login local transport input all line vty 5 15 access-class 23 in privilege level 15 password 7 censored login local transport input all line vty 16 1370 password 7 censored login transport input all ! scheduler allocate 20000 1000 end The sanitized running config for remote site B: version 15.1 service tcp-keepalives-in service tcp-keepalives-out service timestamps debug datetime msec service timestamps log datetime msec service password-encryption service udp-small-servers service tcp-small-servers ! hostname remoteB ! boot-start-marker boot-end-marker ! logging buffered 51200 warnings enable secret 5 censored ! no aaa new-model clock timezone wst 8 0 ! no ipv6 cef ip source-route ip cef ! no ip domain lookup ip domain name yourdomain.com multilink bundle-name authenticated ! chat-script gsm "" "ATDT*98*1#" TIMEOUT 30 "CONNECT" username admin privilege 15 secret 5 censored ! controller Cellular 0/1 ! interface Embedded-Service-Engine0/0 no ip address shutdown ! interface GigabitEthernet0/0 ip address 192.168.3.1 255.255.255.0 duplex auto speed auto ! interface GigabitEthernet0/1 no ip address shutdown duplex auto speed auto ! interface Serial0/0/0 ip address 10.1.1.1 255.255.255.252 encapsulation frame-relay clock rate 2000000 cdp enable frame-relay interface-dlci 16 frame-relay lmi-type ansi frame-relay intf-type dce ! interface Cellular0/1/0 ip address negotiated encapsulation ppp dialer in-band dialer idle-timeout 2147483 dialer string gsm dialer-group 1 async mode interactive ppp chap hostname censored ppp chap password 7 censored ppp ipcp dns request cdp enable ! interface Cellular0/1/1 no ip address encapsulation ppp ! interface Dialer0 no ip address ! ip forward-protocol nd ! no ip http server no ip http secure-server ! ip route 0.0.0.0 0.0.0.0 Serial0/0/0 210 permanent ip route 0.0.0.0 0.0.0.0 Cellular0/1/0 220 permanent ip route 172.31.2.0 255.255.255.0 Cellular0/1/0 permanent ip route 192.168.2.0 255.255.255.0 10.1.1.2 permanent ip route 192.168.2.0 255.255.255.0 Cellular0/1/0 210 permanent ! kron occurrence PING in 1 recurring policy-list ICMP ! access-list 1 permit any dialer-list 1 protocol ip list 1 ! control-plane ! line con 0 logging synchronous login local line aux 0 line 2 no activation-character no exec transport preferred none transport input all transport output pad telnet rlogin lapb-ta mop udptn v120 ssh stopbits 1 line 0/1/0 exec-timeout 0 0 script dialer gsm login modem InOut no exec transport input all rxspeed 7200000 txspeed 5760000 line 0/1/1 no exec rxspeed 7200000 txspeed 5760000 line vty 0 4 access-class 23 in privilege level 15 password 7 censored login transport input all line vty 5 15 access-class 23 in privilege level 15 password 7 censored login transport input all line vty 16 1370 password 7 censored login transport input all ! scheduler allocate 20000 1000 end The last problem I'm having is the 3G interfaces go down after only a few minutes of inactivity. I've tried using kron to ping the local HWIC-3G-HSPA interface (cellular 0/1/0) every minute but that hasn't been successful. Manually pinging the IP assigned (by the telco) to ce0/1/0 does bring the interface up. Any ideas? Thanks

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• Ladder-like word game in Java

  - by sasquatch90

  I've found this question http://stackoverflow.com/questions/2844190/choosing-design-method-for-ladder-like-word-game and I would also like to do this kind of program. I've written some code but already have two issues. Here's what I already have : GRID : public class Grid { public Grid(){} public Grid( Element e ){} } ELEMENT : public class Element { final int INVISIBLE = 0; final int EMPTY = 1; final int FIRST_LETTER = 2; final int OTHER_LETTER = 3; private int state; private String letter; public Element(){} //empty block public Element(int state){ this("", 0); } //filled block public Element(String s, int state){ this.state = state; this.letter = s; } public static void changeState(int s){ } public int getState(){ return state; } public boolean equalLength(){ return true; } public boolean equalValue(){ return true; } @Override public String toString(){ return "["+letter+"]"; } } MAIN: import java.util.Scanner; public class Main { public static void main(String[] args){ Scanner sc = new Scanner(System.in); System.out.println("Height: "); while (!sc.hasNextInt()) { System.out.println("int, please!"); sc.next(); } final int height = sc.nextInt(); Grid[] game = new Grid[height]; for(int i = 1; i <= height; i++) { String s; do { System.out.println("Length " + i + ", please!"); s = sc.next(); } while (s.length() != i); Element[] line = new Element[s.length()+1]; Element single = null; String[] temp = null; //issue here temp = s.split(""); System.out.println("s.length: "+s.length()); System.out.println("temp.length: "+temp.length); // for(String str : temp){ System.out.println("str:"+str); } for (int k = 0 ; k < temp.length ; k++) { if( k == 0 ){ single = new Element(temp[k], 2); System.out.println("single1: "+single); } else{ single = new Element(temp[k], 3); System.out.println("single2: "+single); } line[k] = single; } for (Element l : line) { System.out.println("line:"+l); } //issue here game[i] = line; } // for (Grid g : game) { System.out.println(g); } } } And sample output for debug : Height: 3 Length 1, please! A s.length: 1 temp.length: 2 str: str:A single1: [] single2: [A] line:[] line:[A] Here's what I think it should work like. I grab a word from user. Next create Grid element for whole game. Then for each line I create Element[] array called line. I split the given text and here's the first problem. Why string.split() adds a whitespace ? You can see clearly in output that it is added for no reason. How can I get rid of it (now I had to add +1 to the length of line just to run the code). Continuing I'm throwing the splitted text into temporary String array and next from each letter I create Element object and throw it to line array. Apart of this empty space output looks fine. But next problem is with Grid. I've created constructor taking Element as an argument, but still I can't throw line as Grid[] elements because of 'incompatible types'. How can I fix that ? Am I even doing it right ? Maybe I should get rid of line as Element[] and just create Grid[][] ?

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• Modern alternatives to Java

  - by Ralph

  I have been a Java developer for 14 years and have written an enterprise-level (~500 kloc) Swing application that uses most of the standard library APIs. Recently, I have become disappointed with the progress that the language has made to "modernize" itself, and am looking for an alternative for ongoing development. I have considered moving to the .NET platform, but I have issues with using something the only runs well in Windows (I know about Mono, but that is still far behind Microsoft). I also plan on buying a new Macbook Pro as soon as Apple releases their new rumored Arrandale-based machines and want to develop in an environment that will feel "at home" in Unix/Linux. I have considered using Python or Ruby, but the standard Java library is arguably the largest of any modern language. In JVM-based languages, I looked at Groovy, but am disappointed with its performance. Rumor has it that with the soon-to-be released JDK7, with its InvokeDynamic instruction, this will improve, but I don't know how much. Groovy is also not truly a functional language, although it provides closures and some of the "functional" features on collections. It does not embrace immutability. I have narrowed my search down to two JVM-based alternatives: Scala and Clojure. Each has its strengths and weaknesses. I am looking for opinions. I am not an expert at either of these languages; I have read 2 1/2 books on Scala and am currently reading Stu Halloway's book on Clojure. Scala is strongly statically typed. I know the dynamic language folks claim that static typing is a crutch for not doing unit testing, but it does provide a mechanism for compile-time location of a whole class of errors. Scala is more concise than Java, but not as much as Clojure. Scala's inter-operation with Java seems to be better than Clojure's, in that most Java operations are easier to do in Scala than in Clojure. For example, I can find no way in Clojure to create a non-static initialization block in a class derived from a Java superclass. For example, I like the Apache commons CLI library for command line argument parsing. In Java and Scala, I can create a new Options object and add Option items to it in an initialization block as follows (Java code): final Options options = new Options() { { addOption(new Option("?", "help", false, "Show this usage information"); // other options } }; I can't figure out how to the same thing in Clojure (except by using (doit...)), although that may reflect my lack of knowledge of the language. Clojure's collections are optimized for immutability. They rarely require copy-on-write semantics. I don't know if Scala's immutable collections are implemented using similar algorithms, but Rich Hickey (Clojure's inventor) goes out of his way to explain how that language's data structures are efficient. Clojure was designed from the beginning for concurrency (as was Scala) and with modern multi-core processors, concurrency takes on more importance, but I occasionally need to write simple non-concurrent utilities, and Scala code probably runs a little faster for these applications since it discourages, but does not prohibit, "simple" mutability. One could argue that one-off utilities do not have to be super-fast, but sometimes they do tasks that take hours or days to complete. I know that there is no right answer to this "question", but I thought I would open it up for discussion. Are there other JVM-based languages that can be used for enterprise level development?

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• Php template caching design

  - by Thomas

  Hello to all, I want to include caching in my app design. Caching templates for starters. The design I have used so far is very modular. I have created an ORM implementation for all my tables and each table is represented by the corresponding class. All the requests are handled by one controller which routes them to the appropriate webmethod functions. I am using a template class for handling UI parts. What I have in mind for caching includes the implementation of a separate Cache class for handling caching with the flexibility to either store in files, apc or memcache. Right now I am testing with file caching. Some thoughts Should I include the logic of checking for cached versions in the Template class or in the webmethods which handle the incoming requests and which eventually call the Template class. In the first case, things are pretty simple as I will not have to change anything more than pass the template class an extra argument (whether to load from cache or not). In the second case however, I am thinking of checking for a cached version immediately in the webmethod and if found return it. This will save all the processing done until the logic reaches the template (first case senario). Both senarios however, rely on an accurate mechanism of invalidating caches, which brings as to Invalidating caches As I see it (and you can add your input freely) a template cached file, becomes invalidate if: a. the expiration set, is reached. b. the template file itself is updated (ie by the developer when adding a new line) c. the webmethod that handles the request changes (ie the developer adds/deletes something in the code) d. content coming from the db and ending in the template file is modified I am thinking of storing a json encoded array inside the cached file. The first value will be the expiration timestamp of the cache. The second value will be the modification time of the php file with the code handling the request (to cope with option c above) The third will be the content itself The validation process I am considering, according to the above senarios, is: a. If the expiration of the cached file (stored in the array) is reached, delete the cache file b. if the cached file's mod time is smaller than the template's skeleton file mod time, delete the cached file c. if the mod time of the php file is greated than the one stored in the cache, delete the cached file. d. This is tricky. In the ORM implementation I ahve added event handlers (which fire when adding, updating, deleting objects). I could delete the cache file every time an object thatprovides content to the template, is modified. The problem is how to keep track which cached files correpond to each schema object. Take this example, a user has his shortprofile page and a full profile page (2 templates) These templates can be cached. Now, every time the user modifies his profile, the event handler would need to know which templates or cached files correspond to the User, so that these files can be deleted. I could store them in the db but I am looking for a beter approach

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• how to add a function to that program, and call that function from the command line in the function

  - by user336291

  a#include "smallsh.h" /*include file for example*/ /*program buffers and work pointers*/ static char inpbuf[MAXBUF], tokbuf[2*MAXBUF], *ptr = inpbuf, *tok = tokbuf; userin(p) /*print prompt and read a line*/ char *p; { int c, count; /*initialization for later routines*/ ptr = inpbuf; tok = tokbuf; /*display prompt*/ printf("%s ",p); for(count = 0;;) { if((c = getchar()) == EOF) return(EOF); if(count<MAXBUF) inpbuf[count++] = c; if(c == '\n' && count <MAXBUF) { inpbuf[count] = '\0'; return(count); } /*if line too long restart*/ if(c == '\n') { printf("smallsh:input line too long\n"); count = 0; printf("%s",p); } } } gettok(outptr) /*get token and place into tokbuf*/ char **outptr; { int type; *outptr = tok; /*strip white space*/ for(;*ptr == ' ' || *ptr == '\t'; ptr++) ; *tok++ = *ptr; switch(*ptr++) { case '\n': type = EOL; break; case '&': type = AMPERSAND; break; case ';': type = SEMICOLON; break; case '#': type = POUND; break; default: type = ARG; while(inarg(*ptr)) *tok++ = *ptr++; } *tok++ = '\0'; return(type); } static char special[]= {' ', '\t', '&', ':', '\n', '\0'}; inarg(c) /*are we in an ordinary argument*/ char c; { char *wrk; for(wrk = special;*wrk != '\0';wrk++) if(c == *wrk) return(0); return(1); } #include "smallsh.h" procline() /*process input line*/ { char *arg[MAXARG+1]; /*pointer array for runcommand*/ int toktype; /*type of token in command*/ int narg; /*number of arguments so far*/ int type; /*FOREGROUND or BACKGROUND*/ for(narg = 0;;) { /*loop FOREVER*/ /*take action according to token type*/ switch(toktype = gettok(&arg[narg])) { case ARG: if(narg<MAXARG) narg++; break; case EOL: case SEMICOLON: case AMPERSAND: case POUND: type = (toktype == AMPERSAND) ? BACKGROUND : FOREGROUND; if(narg!=0) { arg[narg] = NULL; runcommand(arg, type); } if((toktype == EOL)||(toktype=POUND)) return; narg = 0; break; } } } #include "smallsh.h" /*execute a command with optional wait*/ runcommand(cline,where) char **cline; int where; { int pid, exitstat, ret; if((pid = fork()) <0) { perror("smallsh"); return(-1); } if(pid == 0) { /*child*/ execvp(*cline, cline); perror(*cline); exit(127); } /*code for parent*/ /*if background process print pid and exit*/ if(where == BACKGROUND) { printf("[Process id %d]\n", pid); return(0); } /*wait until process pid exists*/ while( (ret=wait(&exitstat)) != pid && ret != -1) ; return(ret == -1 ? -1 : exitstat); } #include "smallsh.h" char *prompt = "Command>"; /*prompt*/ main() { while(userin(prompt) != EOF) procline(); }

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• Insane SmartGWT + GWT situation... Error on instantiating ListGridRecord?

  - by Xandel

  Hi all, I am asking this here in the hope that someone has maybe come across this situation too... I have posted this on the SmartGWT forum: I am having an issue when trying to instantiate a ListGridRecord object on my server side. I am using the ListGrid on the client side, I want to use GWT's RPC to pass back an array of ListGridRecord objects to populate the grid with. I know that SmartGWT is designed to link to a datasource but I want full control over when I populate the grid and this shouldn't be as much of a nightmare as it is to do. I have searched high and low and cannot find anyone complaining about the same thing. The exception however (listed below) has come up (in my search findings) as a possible memory error - where increasing the memory (-Xmx512m argument) has apparently solved the problem. It did not, however, sort out mine. If anyone can shed any light on this I would greatly appreciate it! Here are my details: Developing using Eclipse Galileo on Ubuntu 9.04 (Jaunty) and GWT 2.0.3, I built the initial GWT project using the webAppCreator bundled with the GWT 2.0.3 release and imported the project into Eclipse as described on the GWT Getting Started Page (as using the GWT Eclipse plugin caused even more nightmares when trying to connect to a database - this is apparently due to using the Google App Engine and turning it off as all the posts suggested only causes ClassNotFound exceptions). The line that causes the error is literally: ListGridRecord a = new ListGridRecord(); The error I get is the following: 00:00:25.916 [WARN] Exception while dispatching incoming RPC call com.google.gwt.user.server.rpc.UnexpectedException : Service method 'public abstract java.lang.String za.co.company.product.client.service.EmployeeServi ce.getAllEmployeeAsListGridRecord()' threw an unexpected exception: java.lang.UnsatisfiedLinkError: com.smartgwt.client.util.LogUtil.setJSNIErrorHandl er()V at com.google.gwt.user.server.rpc.RPC.encodeResponseF orFailure(RPC.java:378) at com.google.gwt.user.server.rpc.RPC.invokeAndEncode Response(RPC.java:581) at com.google.gwt.user.server.rpc.RemoteServiceServle t.processCall(RemoteServiceServlet.java:188) at com.google.gwt.user.server.rpc.RemoteServiceServle t.processPost(RemoteServiceServlet.java:224) at com.google.gwt.user.server.rpc.AbstractRemoteServi ceServlet.doPost(AbstractRemoteServiceServlet.java :62) at javax.servlet.http.HttpServlet.service(HttpServlet .java:637) at javax.servlet.http.HttpServlet.service(HttpServlet .java:717) at org.mortbay.jetty.servlet.ServletHolder.handle(Ser vletHolder.java:487) at org.mortbay.jetty.servlet.ServletHandler.handle(Se rvletHandler.java:362) at org.mortbay.jetty.security.SecurityHandler.handle( SecurityHandler.java:216) at org.mortbay.jetty.servlet.SessionHandler.handle(Se ssionHandler.java:181) at org.mortbay.jetty.handler.ContextHandler.handle(Co ntextHandler.java:729) at org.mortbay.jetty.webapp.WebAppContext.handle(WebA ppContext.java:405) at org.mortbay.jetty.handler.HandlerWrapper.handle(Ha ndlerWrapper.java:152) at org.mortbay.jetty.handler.RequestLogHandler.handle (RequestLogHandler.java:49) at org.mortbay.jetty.handler.HandlerWrapper.handle(Ha ndlerWrapper.java:152) at org.mortbay.jetty.Server.handle(Server.java:324) at org.mortbay.jetty.HttpConnection.handleRequest(Htt pConnection.java:505) at org.mortbay.jetty.HttpConnection$RequestHandler.co ntent(HttpConnection.java:843) at org.mortbay.jetty.HttpParser.parseNext(HttpParser. java:647) at org.mortbay.jetty.HttpParser.parseAvailable(HttpPa rser.java:211) at org.mortbay.jetty.HttpConnection.handle(HttpConnec tion.java:380) at org.mortbay.io.nio.SelectChannelEndPoint.run(Selec tChannelEndPoint.java:395) at org.mortbay.thread.QueuedThreadPool$PoolThread.run (QueuedThreadPool.java:488) Caused by: java.lang.UnsatisfiedLinkError: com.smartgwt.client.util.LogUtil.setJSNIErrorHandl er()V at com.smartgwt.client.util.LogUtil.setJSNIErrorHandl er(Native Method) at com.smartgwt.client.core.JsObject.(JsObjec t.java:30) at za.co.company.product.server.service.EmployeeServi ceImpl.getAllEmployeeAsListGridRecord(EmployeeServ iceImpl.java:83) at sun.reflect.NativeMethodAccessorImpl.invoke0(Nativ e Method) at sun.reflect.NativeMethodAccessorImpl.invoke(Native MethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(De legatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at com.google.gwt.user.server.rpc.RPC.invokeAndEncode Response(RPC.java:562) at com.google.gwt.user.server.rpc.RemoteServiceServle t.processCall(RemoteServiceServlet.java:188) at com.google.gwt.user.server.rpc.RemoteServiceServle t.processPost(RemoteServiceServlet.java:224) at com.google.gwt.user.server.rpc.AbstractRemoteServi ceServlet.doPost(AbstractRemoteServiceServlet.java :62) at javax.servlet.http.HttpServlet.service(HttpServlet .java:637) at javax.servlet.http.HttpServlet.service(HttpServlet .java:717) at org.mortbay.jetty.servlet.ServletHolder.handle(Ser vletHolder.java:487) at org.mortbay.jetty.servlet.ServletHandler.handle(Se rvletHandler.java:362) at org.mortbay.jetty.security.SecurityHandler.handle( SecurityHandler.java:216) at org.mortbay.jetty.servlet.SessionHandler.handle(Se ssionHandler.java:181) at org.mortbay.jetty.handler.ContextHandler.handle(Co ntextHandler.java:729) at org.mortbay.jetty.webapp.WebAppContext.handle(WebA ppContext.java:405) at org.mortbay.jetty.handler.HandlerWrapper.handle(Ha ndlerWrapper.java:152) at org.mortbay.jetty.handler.RequestLogHandler.handle (RequestLogHandler.java:49) at org.mortbay.jetty.handler.HandlerWrapper.handle(Ha ndlerWrapper.java:152) at org.mortbay.jetty.Server.handle(Server.java:324) at org.mortbay.jetty.HttpConnection.handleRequest(Htt pConnection.java:505) at org.mortbay.jetty.HttpConnection$RequestHandler.co ntent(HttpConnection.java:843) at org.mortbay.jetty.HttpParser.parseNext(HttpParser. java:647) at org.mortbay.jetty.HttpParser.parseAvailable(HttpPa rser.java:211) at org.mortbay.jetty.HttpConnection.handle(HttpConnec tion.java:380) at org.mortbay.io.nio.SelectChannelEndPoint.run(Selec tChannelEndPoint.java:395) at org.mortbay.thread.QueuedThreadPool$PoolThread.run (QueuedThreadPool.java:488) Thanks in advance! Xandel

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• Do you have suggestions for these assembly mnemonics?

  - by Noctis Skytower

  Greetings! Last semester in college, my teacher in the Computer Languages class taught us the esoteric language named Whitespace. In the interest of learning the language better with a very busy schedule (midterms), I wrote an interpreter and assembler in Python. An assembly language was designed to facilitate writing programs easily, and a sample program was written with the given assembly mnemonics. Now that it is summer, a new project has begun with the objective being to rewrite the interpreter and assembler for Whitespace 0.3, with further developments coming afterwards. Since there is so much extra time than before to work on its design, you are presented here with an outline that provides a revised set of mnemonics for the assembly language. This post is marked as a wiki for their discussion. Have you ever had any experience with assembly languages in the past? Were there some instructions that you thought should have been renamed to something different? Did you find yourself thinking outside the box and with a different paradigm than in which the mnemonics were named? If you can answer yes to any of those questions, you are most welcome here. Subjective answers are appreciated! Stack Manipulation (IMP: [Space]) Stack manipulation is one of the more common operations, hence the shortness of the IMP [Space]. There are four stack instructions. hold N Push the number onto the stack copy Duplicate the top item on the stack copy N Copy the nth item on the stack (given by the argument) onto the top of the stack swap Swap the top two items on the stack drop Discard the top item on the stack drop N Slide n items off the stack, keeping the top item Arithmetic (IMP: [Tab][Space]) Arithmetic commands operate on the top two items on the stack, and replace them with the result of the operation. The first item pushed is considered to be left of the operator. add Addition sub Subtraction mul Multiplication div Integer Division mod Modulo Heap Access (IMP: [Tab][Tab]) Heap access commands look at the stack to find the address of items to be stored or retrieved. To store an item, push the address then the value and run the store command. To retrieve an item, push the address and run the retrieve command, which will place the value stored in the location at the top of the stack. save Store load Retrieve Flow Control (IMP: [LF]) Flow control operations are also common. Subroutines are marked by labels, as well as the targets of conditional and unconditional jumps, by which loops can be implemented. Programs must be ended by means of [LF][LF][LF] so that the interpreter can exit cleanly. L: Mark a location in the program call L Call a subroutine goto L Jump unconditionally to a label if=0 L Jump to a label if the top of the stack is zero if<0 L Jump to a label if the top of the stack is negative return End a subroutine and transfer control back to the caller halt End the program I/O (IMP: [Tab][LF]) Finally, we need to be able to interact with the user. There are IO instructions for reading and writing numbers and individual characters. With these, string manipulation routines can be written. The read instructions take the heap address in which to store the result from the top of the stack. print chr Output the character at the top of the stack print int Output the number at the top of the stack input chr Read a character and place it in the location given by the top of the stack input int Read a number and place it in the location given by the top of the stack Question: How would you redesign, rewrite, or rename the previous mnemonics and for what reasons?

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• Confusion on C++ Python extensions. Things like getting C++ values for python values.

  - by Matthew Mitchell

  I'm wanted to convert some of my python code to C++ for speed but it's not as easy as simply making a C++ function and making a few function calls. I have no idea how to get a C++ integer from a python integer object. I have an integer which is an attribute of an object that I want to use. I also have integers which are inside a list in the object which I need to use. I wanted to test making a C++ extension with this function: def setup_framebuffer(surface,flip=False): #Create texture if not done already if surface.texture is None: create_texture(surface) #Render child to parent if surface.frame_buffer is None: surface.frame_buffer = glGenFramebuffersEXT(1) glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, c_uint(int(surface.frame_buffer))) glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, GL_TEXTURE_2D, surface.texture, 0) glPushAttrib(GL_VIEWPORT_BIT) glViewport(0,0,surface._scale[0],surface._scale[1]) glMatrixMode(GL_PROJECTION) glLoadIdentity() #Load the projection matrix if flip: gluOrtho2D(0,surface._scale[0],surface._scale[1],0) else: gluOrtho2D(0,surface._scale[0],0,surface._scale[1]) That function calls create_texture, so I will have to pass that function to the C++ function which I will do with the third argument. This is what I have so far, while trying to follow information on the python documentation: #include <Python.h> #include <GL/gl.h> static PyMethodDef SpamMethods[] = { ... {"setup_framebuffer", setup_framebuffer, METH_VARARGS,"Loads a texture from a Surface object to the OpenGL framebuffer."}, ... {NULL, NULL, 0, NULL} /* Sentinel */ }; static PyObject * setup_framebuffer(PyObject *self, PyObject *args){ bool flip; PyObject *create_texture, *arg_list,*pyflip,*frame_buffer_id; if (!PyArg_ParseTuple(args, "OOO", &surface,&pyflip,&create_texture)){ return NULL; } if (PyObject_IsTrue(pyflip) == 1){ flip = true; }else{ flip = false; } Py_XINCREF(create_texture); //Create texture if not done already if(texture == NULL){ arglist = Py_BuildValue("(O)", surface) result = PyEval_CallObject(create_texture, arglist); Py_DECREF(arglist); if (result == NULL){ return NULL; } Py_DECREF(result); } Py_XDECREF(create_texture); //Render child to parent frame_buffer_id = PyObject_GetAttr(surface, Py_BuildValue("s","frame_buffer")) if(surface.frame_buffer == NULL){ glGenFramebuffersEXT(1,frame_buffer_id); } glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, surface.frame_buffer)); glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, GL_TEXTURE_2D, surface.texture, 0); glPushAttrib(GL_VIEWPORT_BIT); glViewport(0,0,surface._scale[0],surface._scale[1]); glMatrixMode(GL_PROJECTION); glLoadIdentity(); //Load the projection matrix if (flip){ gluOrtho2D(0,surface._scale[0],surface._scale[1],0); }else{ gluOrtho2D(0,surface._scale[0],0,surface._scale[1]); } Py_INCREF(Py_None); return Py_None; } PyMODINIT_FUNC initcscalelib(void){ PyObject *module; module = Py_InitModule("cscalelib", Methods); if (m == NULL){ return; } } int main(int argc, char *argv[]){ /* Pass argv[0] to the Python interpreter */ Py_SetProgramName(argv[0]); /* Initialize the Python interpreter. Required. */ Py_Initialize(); /* Add a static module */ initscalelib(); }

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• Where are the function address literals in c++?

  - by academicRobot

  First of all, maybe literals is not the right term for this concept, but its the closest I could think of (not literals in the sense of functions as first class citizens). <UPDATE> After some reading with help from answer by Chris Dodd, what I'm looking for is literal function addresses as template parameters. Chris' answer indicates how to do this for standard functions, but how can the addresses of member functions be used as template parameters? Since the standard prohibits non-static member function addresses as template parameters (c++03 14.3.2.3), I suspect the work around is quite complicated. Any ideas for a workaround? Below the original form of the question is left as is for context. </UPDATE> The idea is that when you make a conventional function call, it compiles to something like this: callq <immediate address> But if you make a function call using a function pointer, it compiles to something like this: mov <memory location>,%rax callq *%rax Which is all well and good. However, what if I'm writing a template library that requires a callback of some sort with a specified argument list and the user of the library is expected to know what function they want to call at compile time? Then I would like to write my template to accept a function literal as a template parameter. So, similar to template <int int_literal> struct my_template {...};` I'd like to write template <func_literal_t func_literal> struct my_template {...}; and have calls to func_literal within my_template compile to callq <immediate address>. Is there a facility in C++ for this, or a work around to achieve the same effect? If not, why not (e.g. some cataclysmic side effects)? How about C++0x or another language? Solutions that are not portable are fine. Solutions that include the use of member function pointers would be ideal. I'm not particularly interested in being told "You are a <socially unacceptable term for a person of low IQ>, just use function pointers/functors." This is a curiosity based question, and it seems that it might be useful in some (albeit limited) applications. It seems like this should be possible since function names are just placeholders for a (relative) memory address, so why not allow more liberal use (e.g. aliasing) of this placeholder. p.s. I use function pointers and functions objects all the the time and they are great. But this post got me thinking about the don't pay for what you don't use principle in relation to function calls, and it seems like forcing the use of function pointers or similar facility when the function is known at compile time is a violation of this principle, though a small one. Edit The intent of this question is not to implement delegates, rather to identify a pattern that will embed a conventional function call, (in immediate mode) directly into third party code, possibly a template.

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• Optimizing python code performance when importing zipped csv to a mongo collection

  - by mark

  I need to import a zipped csv into a mongo collection, but there is a catch - every record contains a timestamp in Pacific Time, which must be converted to the local time corresponding to the (longitude,latitude) pair found in the same record. The code looks like so: def read_csv_zip(path, timezones): with ZipFile(path) as z, z.open(z.namelist()[0]) as input: csv_rows = csv.reader(input) header = csv_rows.next() check,converters = get_aux_stuff(header) for csv_row in csv_rows: if check(csv_row): row = { converter[0]:converter[1](value) for converter, value in zip(converters, csv_row) if allow_field(converter) } ts = row['ts'] lng, lat = row['loc'] found_tz_entry = timezones.find_one(SON({'loc': {'$within': {'$box': [[lng-tz_lookup_radius, lat-tz_lookup_radius],[lng+tz_lookup_radius, lat+tz_lookup_radius]]}}})) if found_tz_entry: tz_name = found_tz_entry['tz'] local_ts = ts.astimezone(timezone(tz_name)).replace(tzinfo=None) row['tz'] = tz_name else: local_ts = (ts.astimezone(utc) + timedelta(hours = int(lng/15))).replace(tzinfo = None) row['local_ts'] = local_ts yield row def insert_documents(collection, source, batch_size): while True: items = list(itertools.islice(source, batch_size)) if len(items) == 0: break; try: collection.insert(items) except: for item in items: try: collection.insert(item) except Exception as exc: print("Failed to insert record {0} - {1}".format(item['_id'], exc)) def main(zip_path): with Connection() as connection: data = connection.mydb.data timezones = connection.timezones.data insert_documents(data, read_csv_zip(zip_path, timezones), 1000) The code proceeds as follows: Every record read from the csv is checked and converted to a dictionary, where some fields may be skipped, some titles be renamed (from those appearing in the csv header), some values may be converted (to datetime, to integers, to floats. etc ...) For each record read from the csv, a lookup is made into the timezones collection to map the record location to the respective time zone. If the mapping is successful - that timezone is used to convert the record timestamp (pacific time) to the respective local timestamp. If no mapping is found - a rough approximation is calculated. The timezones collection is appropriately indexed, of course - calling explain() confirms it. The process is slow. Naturally, having to query the timezones collection for every record kills the performance. I am looking for advises on how to improve it. Thanks. EDIT The timezones collection contains 8176040 records, each containing four values: > db.data.findOne() { "_id" : 3038814, "loc" : [ 1.48333, 42.5 ], "tz" : "Europe/Andorra" } EDIT2 OK, I have compiled a release build of http://toblerity.github.com/rtree/ and configured the rtree package. Then I have created an rtree dat/idx pair of files corresponding to my timezones collection. So, instead of calling collection.find_one I call index.intersection. Surprisingly, not only there is no improvement, but it works even more slowly now! May be rtree could be fine tuned to load the entire dat/idx pair into RAM (704M), but I do not know how to do it. Until then, it is not an alternative. In general, I think the solution should involve parallelization of the task. EDIT3 Profile output when using collection.find_one: >>> p.sort_stats('cumulative').print_stats(10) Tue Apr 10 14:28:39 2012 ImportDataIntoMongo.profile 64549590 function calls (64549180 primitive calls) in 1231.257 seconds Ordered by: cumulative time List reduced from 730 to 10 due to restriction <10> ncalls tottime percall cumtime percall filename:lineno(function) 1 0.012 0.012 1231.257 1231.257 ImportDataIntoMongo.py:1(<module>) 1 0.001 0.001 1230.959 1230.959 ImportDataIntoMongo.py:187(main) 1 853.558 853.558 853.558 853.558 {raw_input} 1 0.598 0.598 370.510 370.510 ImportDataIntoMongo.py:165(insert_documents) 343407 9.965 0.000 359.034 0.001 ImportDataIntoMongo.py:137(read_csv_zip) 343408 2.927 0.000 287.035 0.001 c:\python27\lib\site-packages\pymongo\collection.py:489(find_one) 343408 1.842 0.000 274.803 0.001 c:\python27\lib\site-packages\pymongo\cursor.py:699(next) 343408 2.542 0.000 271.212 0.001 c:\python27\lib\site-packages\pymongo\cursor.py:644(_refresh) 343408 4.512 0.000 253.673 0.001 c:\python27\lib\site-packages\pymongo\cursor.py:605(__send_message) 343408 0.971 0.000 242.078 0.001 c:\python27\lib\site-packages\pymongo\connection.py:871(_send_message_with_response) Profile output when using index.intersection: >>> p.sort_stats('cumulative').print_stats(10) Wed Apr 11 16:21:31 2012 ImportDataIntoMongo.profile 41542960 function calls (41542536 primitive calls) in 2889.164 seconds Ordered by: cumulative time List reduced from 778 to 10 due to restriction <10> ncalls tottime percall cumtime percall filename:lineno(function) 1 0.028 0.028 2889.164 2889.164 ImportDataIntoMongo.py:1(<module>) 1 0.017 0.017 2888.679 2888.679 ImportDataIntoMongo.py:202(main) 1 2365.526 2365.526 2365.526 2365.526 {raw_input} 1 0.766 0.766 502.817 502.817 ImportDataIntoMongo.py:180(insert_documents) 343407 9.147 0.000 491.433 0.001 ImportDataIntoMongo.py:152(read_csv_zip) 343406 0.571 0.000 391.394 0.001 c:\python27\lib\site-packages\rtree-0.7.0-py2.7.egg\rtree\index.py:384(intersection) 343406 379.957 0.001 390.824 0.001 c:\python27\lib\site-packages\rtree-0.7.0-py2.7.egg\rtree\index.py:435(_intersection_obj) 686513 22.616 0.000 38.705 0.000 c:\python27\lib\site-packages\rtree-0.7.0-py2.7.egg\rtree\index.py:451(_get_objects) 343406 6.134 0.000 33.326 0.000 ImportDataIntoMongo.py:162(<dictcomp>) 346 0.396 0.001 30.665 0.089 c:\python27\lib\site-packages\pymongo\collection.py:240(insert) EDIT4 I have parallelized the code, but the results are still not very encouraging. I am convinced it could be done better. See my own answer to this question for details.

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