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• MS Marketing Strategy

  - by Aaron Kowall

  I found this week’s Windows Phone 8 event interesting.  Not just because it looks like some fantastic new features in the new OS but because of the wait for release.  If I were a Nokia shareholder (which I am not) I’d be very unhappy with MS announcing that Windows Phone 8 will NOT work with current hardware.  So, there are some very nice Lumia devices that are now end-of-life that have arrived relatively recently at carriers and retailers. I understand that MS needs to demonstrate progress against iOS and Android and that there is some Windows 8 tie-in that they are trying to capitalize (and MS IS still all about Windows).  However, it’s a bit of a kick to partners that have invested in the platform with pretty decent devices (Samsung, HTC and of course Nokia). Personally, I’m still using a Samsung Foucs.  I was seriously considering upgrading to a Lumia 900 (we just got Lync mobile available) but will now wait it out until new devices arrive with Windows 8.  If MS had waited to announce, I would happily have upgraded to the Lumia and when I found out it couldn’t be upgraded then that would be a gamble I took and lost and I’d live with it.  Now, however, I can see the future and know that waiting is the better option for me so that is 1 sale Nokia will miss out on.  Based on some chats I’ve seen on mobile forums I’m certainly far from the only one. I’m sure glad I’m not in charge of marketing at MS.  There are tough decisions to be made there and I’m pretty sure you piss somebody off regardless. Technorati Tags: WP8,Lumia,Nokia,Samsung

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• Which is the best way to catch an expiring domain name? [closed]

  - by newspeak

  I know a similar question has been asked, but I really don't know what to do. There is this .com domain which is currently on redemption period and should likely be available again within a month. I was wondering which is the best way to get it at a reasonable price. I don't think it's a highly valuable domain, it shows to have very bad ranking and has 0 exact same searches according to adwords. Why it is valuable to me is very simple: I have a project responding to this name. I already own the .net domain and would love to have the .com. I discovered the domain was going to be available thanks to an email I received by a backorder site. I did some research and these guys have a bad reputation on the web. I did further research and found that more reputable (at least in theory) companies should be the likes of snapnames, pool, namejet, godaddy, etc. I am a bit suspicious using these drop cathing services: What if they shill bids? What if they make it go into auction even if I'm the only person interested? What if I raise attention and interest to the domain by backordering? I just would rather wait for it to be deleted and available again to register it manually. It is really not an interesting domain name, and I don't think anyone would care to have it. But what if the domain is already being watched by the domain industry sharks? I did a whois research and my desired domain nameserves point to domcollect.com, which appears to be an auction site. What if I decide to wait for manual registration and I miss the chance to get it? I'm willing to spend the 60/70$ fees these sites require, but not really more than that. Suggestions? Thank you very much. I'm a bit confused and undecided.

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• How should a team share/store game content during development?

  - by irwinb

  Other than Dropbox, what out there has been especially useful for storing and sharing game content like images during development (similar feature set to Dropbox like working offline, automatic syncing and support for windows/osx)? We are looking into hosting our own SharePoint server but it seems to be really focused on documents... Maybe Box.net would work? EDIT For code, we are using Git. To be more precise, I was looking for an easy, automatic way for content produced by artists/audio engineers to be available to everyone. Features like approvals of assets don't hurt either. Following the answer linked by Tetrad, Alienbrain looked pretty interesting but..is way out of our budget (may be something to invest in in the future). What ended up doing... We were going to go with Box.net but downloading the sync apps for desktop use required us to wait to be contacted by them for some reason. We did not have much time to wait so we ended up going with Dropbox Teams. Box.net has a nice feature set but we never really felt held back without them. Thanks for the help :).

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• ??OPEN CURSOR?BULK COLLECT

  - by Liu Maclean(???)

  ????T.askmaclean.com?????bulk collect?open cursor???, ?????????  ??????: ???? OPEN_CURSOR ????SQL?? ???????. ?????? ????? ???????????????? ????? test_soruce create table zengfankun_temp01 as select * from dba_objects;select count(*) from zengfankun_temp01;–12,6826analyze table zengfankun_temp01 compute statistics; create or replace procedure test_open_cursor istype type_owner is table of zengfankun_temp01.owner%type index by binary_integer;type type_object_name is table of zengfankun_temp01.object_name%type index by binary_integer;type type_object_id is table of zengfankun_temp01.object_id%type index by binary_integer;type type_object_type is table of zengfankun_temp01.object_type%type index by binary_integer;type type_last_ddl_time is table of zengfankun_temp01.last_ddl_time%type index by binary_integer; l_ary_owner type_owner;l_ary_object_name type_object_name;l_ary_object_id type_object_id;l_ary_object_type type_object_type;l_ary_last_ddl_time type_last_ddl_time; cursor cur_object isselect owner,object_name,object_id,object_type,last_ddl_timefrom zengfankun_temp01order by owner,object_name,object_type,last_ddl_time;OPEN_START number;OPEN_END number;FETCH_START number;FETCH_END number;beginDBMS_OUTPUT.ENABLE (buffer_size=>null) ;OPEN_START:=dbms_utility.get_time();open cur_object;OPEN_END :=dbms_utility.get_time();dbms_output.put_line(‘OPEN_TIME:’||TO_CHAR(OPEN_END-OPEN_START));loopFETCH_START:=dbms_utility.get_time();fetch cur_object bulk collect intol_ary_owner,l_ary_object_name,l_ary_object_id,l_ary_object_type,l_ary_last_ddl_timelimit 10000;FETCH_END:=dbms_utility.get_time();dbms_output.put_line(‘FETCH_TIME:’||TO_CHAR(FETCH_END-FETCH_START)||’ ROWCOUNT:’||cur_object%rowCount); exit when cur_object%notfound or cur_object%notfound is null;end loop;end test_open_cursor; OPEN_TIME:12FETCH_TIME:21 ROWCOUNT:10000FETCH_TIME:3 ROWCOUNT:20000FETCH_TIME:3 ROWCOUNT:30000FETCH_TIME:3 ROWCOUNT:40000FETCH_TIME:3 ROWCOUNT:50000FETCH_TIME:3 ROWCOUNT:60000FETCH_TIME:3 ROWCOUNT:70000FETCH_TIME:3 ROWCOUNT:80000FETCH_TIME:3 ROWCOUNT:90000FETCH_TIME:3 ROWCOUNT:100000FETCH_TIME:3 ROWCOUNT:110000FETCH_TIME:3 ROWCOUNT:120000FETCH_TIME:1 ROWCOUNT:126826 ???? OPEN_TIME:0FETCH_TIME:18 ROWCOUNT:10000FETCH_TIME:3 ROWCOUNT:20000FETCH_TIME:3 ROWCOUNT:30000FETCH_TIME:3 ROWCOUNT:40000FETCH_TIME:3 ROWCOUNT:50000FETCH_TIME:3 ROWCOUNT:60000FETCH_TIME:3 ROWCOUNT:70000FETCH_TIME:3 ROWCOUNT:80000FETCH_TIME:3 ROWCOUNT:90000FETCH_TIME:3 ROWCOUNT:100000FETCH_TIME:3 ROWCOUNT:110000FETCH_TIME:3 ROWCOUNT:120000FETCH_TIME:2 ROWCOUNT:126826 SQL?????????, ????????????.??OPEN CURSOR ????0???????????3??.??N? ??????. ???? ?N? ?????????? ??????. ??????????????? ??????????. ?????????10000??? ???????????????????clear???, ???????????: ?OPEN CURSOR ?????, PL/SQL????SQL????PARSE SQL????????, ??????OPEN CURSOR????SNAPSHOT SCN ??SCN, ??Oracle?????FETCH?????,???????????????? ????FETCH ??????????????,???????Current Block, The most recent version of block , ?????SCN >> Snapshot scn, ????UNDO???? ???SCN ???Best Block ,???Read Consistentcy;???? ???UNDO SNAPSHOT???????????????Best Block??,???????ORA-1555??? ????????, ??????????,???????????????char(2000)????, ???????????????,????bulk collect fetch??fetch 10 ???,????????OPEN CURSOR?????PARSE??SQL????????, ??????????fetch bulk collect??????????10????,??”_trace_pin_time”????Server Process?pin CR block???,??????????Fetch Bulk Collect limit 10??10?buffer?pin? [oracle@nas ~]$ sqlplus / as sysdba SQL*Plus: Release 11.2.0.3.0 Production on Wed Aug 1 11:36:52 2012 Copyright (c) 1982, 2011, Oracle. All rights reserved. Connected to: Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production With the Partitioning, OLAP, Data Mining and Real Application Testing options SQL> select * from global_name; GLOBAL_NAME -------------------------------------------------------------------------------- http://www.askmaclean.com SQL> create table maclean (t1 char(2000)) tablespace users pctfree 99; Table created. SQL> begin 2 for i in 1..200 loop 3 insert into maclean values('MACLEAN'); 4 commit ; 5 end loop; 6 end; 7 / PL/SQL procedure successfully completed. SQL> exec dbms_stats.gather_table_stats('','MACLEAN'); PL/SQL procedure successfully completed. SQL> select count(*) from maclean; COUNT(*) ---------- 200 SQL> select blocks,num_rows from dba_tables where table_name='MACLEAN'; BLOCKS NUM_ROWS ---------- ---------- 244 200 SQL> alter system set "_trace_pin_time"=1 scope=spfile; System altered. SQL> startup force; ORACLE instance started. Total System Global Area 3140026368 bytes Fixed Size 2232472 bytes Variable Size 1795166056 bytes Database Buffers 1325400064 bytes Redo Buffers 17227776 bytes Database mounted. Database opened. SQL> alter session set events '10046 trace name context forever,level 12'; Session altered. SQL> SQL> SQL> declare 2 cursor v_cursor is 3 select * from sys.maclean; 4 type v_type is table of sys.maclean%rowtype index by binary_integer; 5 rec_tab v_type; 6 begin 7 open v_cursor; 8 dbms_lock.sleep(30); 9 loop 10 fetch v_cursor bulk collect 11 into rec_tab limit 10; 12 dbms_lock.sleep(10); 13 exit when v_cursor%notfound; 14 end loop; 15 end; 16 / ?????10046 trace+ pin trace: PARSING IN CURSOR #47499559136872 len=337 dep=0 uid=0 oct=47 lid=0 tim=1343836146412056 hv=496860239 ad='11a11dbb0' sqlid='4zh7954ftuz2g' declare cursor v_cursor is select * from sys.maclean; type v_type is table of sys.maclean%rowtype index by binary_integer; rec_tab v_type; begin open v_cursor; dbms_lock.sleep(30); loop fetch v_cursor bulk collect into rec_tab limit 10; dbms_lock.sleep(10); exit when v_cursor%notfound; end loop; end; END OF STMT PARSE #47499559136872:c=0,e=346,p=0,cr=0,cu=0,mis=0,r=0,dep=0,og=1,plh=0,tim=1343836146412051 ===================== PARSING IN CURSOR #47499559126280 len=25 dep=1 uid=0 oct=3 lid=0 tim=1343836146414939 hv=3296884535 ad='11a11d250' sqlid='2mb1493284xtr' SELECT * FROM SYS.MACLEAN END OF STMT PARSE #47499559126280:c=1999,e=2427,p=0,cr=0,cu=0,mis=1,r=0,dep=1,og=1,plh=2568761675,tim=1343836146414937 EXEC #47499559126280:c=0,e=55,p=0,cr=0,cu=0,mis=0,r=0,dep=1,og=1,plh=2568761675,tim=1343836146415104 ????? ? SELECT * FROM SYS.MACLEAN? PARSE ????? , ????FETCH???????pin ????????, ????OPEN CURSOR????? *** 2012-08-01 11:49:36.424 WAIT #47499559136872: nam='PL/SQL lock timer' ela= 30009361 duration=0 p2=0 p3=0 obj#=-1 tim=1343836176424782 ???30s pin ktewh26: kteinpscan dba 0x10a6202:4 time 1039048805 pin ktewh27: kteinmap dba 0x10a6202:4 time 1039048847 pin kdswh11: kdst_fetch dba 0x10a6203:1 time 1039048898 pin kdswh11: kdst_fetch dba 0x10a6204:1 time 1039048961 pin kdswh11: kdst_fetch dba 0x10a6205:1 time 1039049004 pin kdswh11: kdst_fetch dba 0x10a6206:1 time 1039049042 pin kdswh11: kdst_fetch dba 0x10a6207:1 time 1039049089 pin kdswh11: kdst_fetch dba 0x10a6208:1 time 1039049123 pin kdswh11: kdst_fetch dba 0x10a6209:1 time 1039049159 pin kdswh11: kdst_fetch dba 0x10a620a:1 time 1039049191 pin kdswh11: kdst_fetch dba 0x10a620b:1 time 1039049225 pin kdswh11: kdst_fetch dba 0x10a620c:1 time 1039049260 kdst_fetch???fetch??????? , ??fetch?10?? ???????FETCH FETCH #47499559126280:c=0,e=536,p=0,cr=12,cu=0,mis=0,r=10,dep=1,og=1,plh=2568761675,tim=1343836176425542 *** 2012-08-01 11:49:46.428 WAIT #47499559136872: nam='PL/SQL lock timer' ela= 10002694 duration=0 p2=0 p3=0 obj#=-1 tim=134383618642829 ????10s pin kdswh11: kdst_fetch dba 0x10a620d:1 time 1049052211 pin kdswh11: kdst_fetch dba 0x10a620e:1 time 1049052264 pin kdswh11: kdst_fetch dba 0x10a620f:1 time 1049052299 pin kdswh11: kdst_fetch dba 0x10a6211:1 time 1049052332 pin kdswh11: kdst_fetch dba 0x10a6212:1 time 1049052364 pin kdswh11: kdst_fetch dba 0x10a6213:1 time 1049052398 pin kdswh11: kdst_fetch dba 0x10a6214:1 time 1049052430 pin kdswh11: kdst_fetch dba 0x10a6215:1 time 1049052462 pin kdswh11: kdst_fetch dba 0x10a6216:1 time 1049052494 pin kdswh11: kdst_fetch dba 0x10a6217:1 time 1049052525 FETCH #47499559126280:c=0,e=371,p=0,cr=10,cu=0,mis=0,r=10,dep=1,og=1,plh=2568761675,tim=1343836186428807 ??pin 10????, ???fetch ?? WAIT #47499559136872: nam='PL/SQL lock timer' ela= 10002864 duration=0 p2=0 p3=0 obj#=-1 tim=1343836196431754 pin kdswh11: kdst_fetch dba 0x10a6218:1 time 1059055662 pin kdswh11: kdst_fetch dba 0x10a6219:1 time 1059055714 pin kdswh11: kdst_fetch dba 0x10a621a:1 time 1059055748 pin kdswh11: kdst_fetch dba 0x10a621b:1 time 1059055781 pin kdswh11: kdst_fetch dba 0x10a621c:1 time 1059055815 pin kdswh11: kdst_fetch dba 0x10a621d:1 time 1059055848 pin kdswh11: kdst_fetch dba 0x10a621e:1 time 1059055883 pin kdswh11: kdst_fetch dba 0x10a621f:1 time 1059055915 pin kdswh11: kdst_fetch dba 0x10a6221:1 time 1059055953 pin kdswh11: kdst_fetch dba 0x10a6222:1 time 1059055992 FETCH #47499559126280:c=0,e=385,p=0,cr=10,cu=0,mis=0,r=10,dep=1,og=1,plh=2568761675,tim=1343836196432274 ???? ??????? DBA????? ............................ ???? WAIT #47499559136872: nam='PL/SQL lock timer' ela= 10002933 duration=0 p2=0 p3=0 obj#=-1 tim=1343836366495589 pin kdswh11: kdst_fetch dba 0x10a62f6:1 time 1229119497 pin kdswh11: kdst_fetch dba 0x10a62f7:1 time 1229119545 pin kdswh11: kdst_fetch dba 0x10a62f8:1 time 1229119576 pin kdswh11: kdst_fetch dba 0x10a62f9:1 time 1229119610 pin kdswh11: kdst_fetch dba 0x10a62fa:1 time 1229119644 pin kdswh11: kdst_fetch dba 0x10a62fb:1 time 1229119671 pin kdswh11: kdst_fetch dba 0x10a62fc:1 time 1229119703 pin kdswh11: kdst_fetch dba 0x10a62fd:1 time 1229119730 pin kdswh11: kdst_fetch dba 0x10a62fe:1 time 1229119760 pin kdswh11: kdst_fetch dba 0x10a62ff:1 time 1229119787 FETCH #47499559126280:c=0,e=340,p=0,cr=10,cu=0,mis=0,r=10,dep=1,og=1,plh=2568761675,tim=1343836366496067 ??????DBA? 0x10a6203 , ??DBA ? 0x10a62ff ???????DBA??MACLEAN????????,???DBA???Maclean????? getbfno?????dba??????????? CREATE OR REPLACE FUNCTION getbfno (p_dba IN VARCHAR2) RETURN VARCHAR2 IS l_str VARCHAR2 (255) DEFAULT NULL; l_fno VARCHAR2 (15); l_bno VARCHAR2 (15); BEGIN l_fno := DBMS_UTILITY.data_block_address_file (TO_NUMBER (LTRIM (p_dba, '0x'), 'xxxxxxxx' ) ); l_bno := DBMS_UTILITY.data_block_address_block (TO_NUMBER (LTRIM (p_dba, '0x'), 'xxxxxxxx' ) ); l_str := 'datafile# is:' || l_fno || CHR (10) || 'datablock is:' || l_bno || CHR (10) || 'dump command:alter system dump datafile ' || l_fno || ' block ' || l_bno || ';'; RETURN l_str; END; / Function created. SQL> select getbfno('0x10a6203') from dual; GETBFNO('0X10A6203') -------------------------------------------------------------------------------- datafile# is:4 datablock is:680451 dump command:alter system dump datafile 4 block 680451; SQL> select getbfno('0x10a62ff') from dual; GETBFNO('0X10A62FF') -------------------------------------------------------------------------------- datafile# is:4 datablock is:680703 dump command:alter system dump datafile 4 block 680703; SQL> select dbms_rowid.rowid_block_number(min(rowid)),dbms_rowid.rowid_relative_fno(min(rowid)) from maclean; DBMS_ROWID.ROWID_BLOCK_NUMBER(MIN(ROWID)) ----------------------------------------- DBMS_ROWID.ROWID_RELATIVE_FNO(MIN(ROWID)) ----------------------------------------- 680451 4 SQL> select dbms_rowid.rowid_block_number(max(rowid)),dbms_rowid.rowid_relative_fno(max(rowid)) from maclean; DBMS_ROWID.ROWID_BLOCK_NUMBER(MAX(ROWID)) ----------------------------------------- DBMS_ROWID.ROWID_RELATIVE_FNO(MAX(ROWID)) ----------------------------------------- 680703 4 ???????3???: 1.?OPEN CURSOR ?????, PL/SQL????SQL????PARSE SQL????????, ??????OPEN CURSOR????SNAPSHOT SCN ??SCN, ??Oracle?????FETCH?????,???????????????? 2.????FETCH ?????????????? 3. ???open cursor+ fetch bulk collect???”?????????”

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• problem with piping in my own implementation of shell

  - by codemax

  Hey guys, i am implementing my own shell. I want to involve piping. i searched here and i got a code. But it is not working.Can any one help me? this is my code #include <sys/types.h> #include <sys/wait.h> #include <sys/ipc.h> #include <fcntl.h> #include <unistd.h> #include <string.h> #include <iostream> #include <cstdlib> using namespace std; char temp1[81][81],temp2[81][81] ,*cmdptr1[40], *cmdptr2[40]; void process(char**,int); int arg_count, count; int arg_cnt[2]; int pip,tok; char input[81]; int fds[2]; void process( char* cmd[])//, int arg_count ) { pid_t pid; pid = fork(); //char path[81]; //getcwd(path,81); //strcat(path,"/"); //strcat(path,cmd[0]); if(pid < 0) { cout << "Fork Failed" << endl; exit(-1); } else if( pid == 0 ) { execvp( cmd[0] , cmd ); } else { wait(NULL); } } void pipe(char **cmd1, char**cmd2) { cout<<endl<<endl<<"in pipe"<<endl; for(int i=0 ; i<arg_cnt[0] ; i++) { cout<<cmdptr1[i]<<" "; } cout<<endl; for(int i=0 ; i<arg_cnt[1] ; i++) { cout<<cmdptr2[i]<<" "; } pipe(fds); if (fork() == 0 ) { dup2(fds[1], 1); close(fds[0]); close(fds[1]); process(cmd1); } if (fork() == 0) { dup2(fds[0], 0); close(fds[0]); close(fds[1]); process(cmd2); } close(fds[0]); close(fds[1]); wait(NULL); } void pipecommand(char** cmd1, char** cmd2) { cout<<endl<<endl; for(int i=0 ; i<arg_cnt[0] ; i++) { cout<<cmd1[i]<<" "; } cout<<endl; for(int i=0 ; i<arg_cnt[1] ; i++) { cout<<cmd2[i]<<" "; } int fds[2]; // file descriptors pipe(fds); // child process #1 if (fork() == 0) { // Reassign stdin to fds[0] end of pipe. dup2(fds[0], STDIN_FILENO); close(fds[1]); close(fds[0]); process(cmd2); // child process #2 if (fork() == 0) { // Reassign stdout to fds[1] end of pipe. dup2(fds[1], STDOUT_FILENO); close(fds[0]); close(fds[1]); // Execute the first command. process(cmd1); } wait(NULL); } close(fds[1]); close(fds[0]); wait(NULL); } void splitcommand1() { tok++; int k,done=0,no=0; arg_count = 0; for(int i=count ; input[i] != '\0' ; i++) { k=0; while(1) { count++; if(input[i] == ' ') { break; } if((input[i] == '\0')) { done = 1; break; } if(input[i] == '|') { pip = 1; done = 1; break; } temp1[arg_count][k++] = input[i++]; } temp1[arg_count][k++] = '\0'; arg_count++; if(done == 1) { break; } } for(int i=0 ; i<arg_count ; i++) { cmdptr1[i] = temp1[i]; } arg_cnt[tok] = arg_count; } void splitcommand2() { tok++; cout<<"count is :"<<count<<endl; int k,done=0,no=0; arg_count = 0; for(int i=count ; input[i] != '\0' ; i++) { k=0; while(1) { count++; if(input[i] == ' ') { break; } if((input[i] == '\0')) { done = 1; break; } if(input[i] == '|') { pip = 1; done = 1; cout<<"PIP"; break; } temp2[arg_count][k++] = input[i++]; } temp2[arg_count][k++] = '\0'; arg_count++; if(done == 1) { break; } } for(int i=0 ; i<arg_count ; i++) { cmdptr2[i] = temp2[i]; } arg_cnt[tok] = arg_count; } int main() { cout<<endl<<endl<<"Welcome to unique shell !!!!!!!!!!!"<<endl; tok=-1; while(1) { cout<<endl<<"***********UNIQUE**********"<<endl; cin.getline(input,81); count = 0,pip=0; splitcommand1(); if(pip == 1) { count++; splitcommand2(); } cout<<endl<<endl; if(strcmp(cmdptr1[0], "exit") == 0 ) { cout<<endl<<"EXITING UNIQUE SHELL"<<endl; exit(0); } //cout<<endl<<"Arg count is :"<<arg_count<<endl; if(pip == 1) { cout<<endl<<endl<<"in main :"; for(int i=0 ; i<arg_cnt[0] ; i++) { cout<<cmdptr1[i]<<" "; } cout<<endl; for(int i=0 ; i<arg_cnt[1] ; i++) { cout<<cmdptr2[i]<<" "; } pipe(cmdptr1, cmdptr2); } else { process (cmdptr1);//,arg_count); } } } I know it is not well coded. But try to help me :(

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• Parallelism in .NET – Part 16, Creating Tasks via a TaskFactory

  - by Reed

  The Task class in the Task Parallel Library supplies a large set of features.  However, when creating the task, and assigning it to a TaskScheduler, and starting the Task, there are quite a few steps involved.  This gets even more cumbersome when multiple tasks are involved.  Each task must be constructed, duplicating any options required, then started individually, potentially on a specific scheduler.  At first glance, this makes the new Task class seem like more work than ThreadPool.QueueUserWorkItem in .NET 3.5. In order to simplify this process, and make Tasks simple to use in simple cases, without sacrificing their power and flexibility, the Task Parallel Library added a new class: TaskFactory. The TaskFactory class is intended to “Provide support for creating and scheduling Task objects.”  Its entire purpose is to simplify development when working with Task instances.  The Task class provides access to the default TaskFactory via the Task.Factory static property.  By default, TaskFactory uses the default TaskScheduler to schedule tasks on a ThreadPool thread.  By using Task.Factory, we can automatically create and start a task in a single “fire and forget” manner, similar to how we did with ThreadPool.QueueUserWorkItem: Task.Factory.StartNew(() => this.ExecuteBackgroundWork(myData) ); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } This provides us with the same level of simplicity we had with ThreadPool.QueueUserWorkItem, but even more power.  For example, we can now easily wait on the task: // Start our task on a background thread var task = Task.Factory.StartNew(() => this.ExecuteBackgroundWork(myData) ); // Do other work on the main thread, // while the task above executes in the background this.ExecuteWorkSynchronously(); // Wait for the background task to finish task.Wait(); TaskFactory simplifies creation and startup of simple background tasks dramatically. In addition to using the default TaskFactory, it’s often useful to construct a custom TaskFactory.  The TaskFactory class includes an entire set of constructors which allow you to specify the default configuration for every Task instance created by that factory.  This is particularly useful when using a custom TaskScheduler.  For example, look at the sample code for starting a task on the UI thread in Part 15: // Given the following, constructed on the UI thread // TaskScheduler uiScheduler = TaskScheduler.FromCurrentSynchronizationContext(); // When inside a background task, we can do string status = GetUpdatedStatus(); (new Task(() => { statusLabel.Text = status; })) .Start(uiScheduler); This is actually quite a bit more complicated than necessary.  When we create the uiScheduler instance, we can use that to construct a TaskFactory that will automatically schedule tasks on the UI thread.  To do that, we’d create the following on our main thread, prior to constructing our background tasks: // Construct a task scheduler from the current SynchronizationContext (UI thread) var uiScheduler = TaskScheduler.FromCurrentSynchronizationContext(); // Construct a new TaskFactory using our UI scheduler var uiTaskFactory = new TaskFactory(uiScheduler); If we do this, when we’re on a background thread, we can use this new TaskFactory to marshal a Task back onto the UI thread.  Our previous code simplifies to: // When inside a background task, we can do string status = GetUpdatedStatus(); // Update our UI uiTaskFactory.StartNew( () => statusLabel.Text = status); Notice how much simpler this becomes!  By taking advantage of the convenience provided by a custom TaskFactory, we can now marshal to set data on the UI thread in a single, clear line of code!

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• My Interview with Microsoft

  - by Victor Hurdugaci

  This post is for those who want to apply or have already applied (but not finished the interview) for a Microsoft Job. The recruitment process is quite similar for everyone and consists of a few steps. Application E-Mail Interview Phone Interview On Site Interview I will tell you my story and how I went through the four phases. 1. Application My blog's title (Ex Nihilo Nihil Fit) means "Nothing Comes Out of Nothing". You can't get a job at Microsoft by not doing anything - this is true for anything else. The first step you need to complete is the application process. For this, many options are available. You can... ... apply online on Microsoft's Careers website as I did ... send your CV to different e-mail addresses (there are some dedicated e-mails for different positions) ... apply through some 3rd party organization (job shop, campus recruitment, job agency, etc) On MS Careers you just have to post your CV and choose the job you want. That's all! No recommendation letter, no cover letter, no nothing. Of course, not every CV passes the selection process. Here are some tips for improving your resume (worked for me): Don't write it just before applying! Write a draft version, wait a few days and then review it. This way you will find a lot of mistakes and stupid things you wrote initially. If you review it immediately after writing, your mind will not be criticism oriented and will just ignore mistakes. Repeat the write-wait-review process as many times as necessary, until you find that the review revealed no mistakes. After you did the final review and the CV is bullet-proof, ask others to review it. They will definitely find inconsistencies and mistakes and this will make you feel stupid. This is good because will open your eyes will make you go into an 'I want to improve' mode. You'll try to correct everything. After you come up with a modified version go again through steps 1 and 2. Repeat this as many times as necessary. [Special thanks to Lucian Sasu, Nadia Comanici, Andrei Ciobanu, Monica Balan and Lavinia Tanase for reviewing my CV!] Make it short and give only relevant facts. Initially, I come up with a 5 pages CV because I wrote every single technology with which I worked. There were a lot irrelevant things, I wrote Windows Workflow Foundation just because I played with it for a few days. I added extensive descriptions for every project, made a personal details section (name, birth date, address, etc) of 1/2 page. Others suggested to cut everything that was not necessary. You don't need to give extensive descriptions, just add a few words. For example, I wrote "VS Image Visualizer - Visual Studio 2008 debug visualizer for images" and added a link to the project's page - you submit formatted andcan embed links. Add something that makes it different. I don't know if this makes a difference, but I added some lines to separate items just like in the picture below. Definitely Microsoft gets thousands of CVs per day. You need something special. Don't lie! Tell exactly what you did and what is the proficiency level of your skills. For example, don't write "Advanced" for UML if you don't know the difference between composition and aggregation. Be realistic and don't under/over estimate yourself. Use the spell chick. Make sure everything is written in correct English and there are no grammar/spelling mistakes. Noddy likes a WC with grammar mi takes. You mght fail just because of that. Once you completed your CV, choose the job that suits best your needs, apply and wait... The waiting is a problem because all these big companies like Microsoft, Google, Mozilla, Apple, etc. will contact you only if they find something interesting in your application. If you're not suitable, then no rejection is sent. I applied for an Intern Software Development Engineer position at Microsoft Redmond. I cannot apply for a full time position because I want to finish the master program on time, in the next summer - an internship is just what I need. 2. E-Mail Interview January 20, 2010. Two months since I submitted the CV. I wasn't hoping anymore that MS will contact me, when I got an e-mail titled: "Victor Hurdugaci ES DK" from Holly Peterson saying: Read more >>

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• Class Loading Deadlocks

  - by tomas.nilsson

  Mattis follows up on his previous post with one more expose on Class Loading Deadlocks As I wrote in a previous post, the class loading mechanism in Java is very powerful. There are many advanced techniques you can use, and when used wrongly you can get into all sorts of trouble. But one of the sneakiest deadlocks you can run into when it comes to class loading doesn't require any home made class loaders or anything. All you need is classes depending on each other, and some bad luck. First of all, here are some basic facts about class loading: 1) If a thread needs to use a class that is not yet loaded, it will try to load that class 2) If another thread is already loading the class, the first thread will wait for the other thread to finish the loading 3) During the loading of a class, one thing that happens is that the <clinit method of a class is being run 4) The <clinit method initializes all static fields, and runs any static blocks in the class. Take the following class for example: class Foo { static Bar bar = new Bar(); static { System.out.println("Loading Foo"); } } The first time a thread needs to use the Foo class, the class will be initialized. The <clinit method will run, creating a new Bar object and printing "Loading Foo" But what happens if the Bar object has never been used before either? Well, then we will need to load that class as well, calling the Bar <clinit method as we go. Can you start to see the potential problem here? A hint is in fact #2 above. What if another thread is currently loading class Bar? The thread loading class Foo will have to wait for that thread to finish loading. But what happens if the <clinit method of class Bar tries to initialize a Foo object? That thread will have to wait for the first thread, and there we have the deadlock. Thread one is waiting for thread two to initialize class Bar, thread two is waiting for thread one to initialize class Foo. All that is needed for a class loading deadlock is static cross dependencies between two classes (and a multi threaded environment): class Foo { static Bar b = new Bar(); } class Bar { static Foo f = new Foo(); } If two threads cause these classes to be loaded at exactly the same time, we will have a deadlock. So, how do you avoid this? Well, one way is of course to not have these circular (static) dependencies. On the other hand, it can be very hard to detect these, and sometimes your design may depend on it. What you can do in that case is to make sure that the classes are first loaded single threadedly, for example during an initialization phase of your application. The following program shows this kind of deadlock. To help bad luck on the way, I added a one second sleep in the static block of the classes to trigger the unlucky timing. Notice that if you uncomment the "//Foo f = new Foo();" line in the main method, the class will be loaded single threadedly, and the program will terminate as it should. public class ClassLoadingDeadlock { // Start two threads. The first will instansiate a Foo object, // the second one will instansiate a Bar object. public static void main(String[] arg) { // Uncomment next line to stop the deadlock // Foo f = new Foo(); new Thread(new FooUser()).start(); new Thread(new BarUser()).start(); } } class FooUser implements Runnable { public void run() { System.out.println("FooUser causing class Foo to be loaded"); Foo f = new Foo(); System.out.println("FooUser done"); } } class BarUser implements Runnable { public void run() { System.out.println("BarUser causing class Bar to be loaded"); Bar b = new Bar(); System.out.println("BarUser done"); } } class Foo { static { // We are deadlock prone even without this sleep... // The sleep just makes us more deterministic try { Thread.sleep(1000); } catch(InterruptedException e) {} } static Bar b = new Bar(); } class Bar { static { try { Thread.sleep(1000); } catch(InterruptedException e) {} } static Foo f = new Foo(); }

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• Better documentation for tasks waiting on resources

  - by SQLOS Team

  The sys.dm_os_waiting_tasks DMV contains a wealth of useful information about tasks waiting on a resource, but until now detailed information about the resource being consumed - sys.dm_os_waiting_tasks.resource_description - hasn't been documented, apart from a rather self-evident "Description of the resource that is being consumed."   Thanks to a recent Connect suggestion this column will get more information added. Here is a summary of the possible values that can appear in this column - Note this information is current for SQL Server 2008 R2 and Denali:   Thread-pool resource owner:•       threadpool id=scheduler<hex-address> Parallel query resource owner:•       exchangeEvent id={Port|Pipe}<hex-address> WaitType=<exchange-wait-type> nodeId=<exchange-node-id> Exchange-wait-type can be one of the following.•       e_waitNone•       e_waitPipeNewRow•       e_waitPipeGetRow•       e_waitSynchronizeConsumerOpen•       e_waitPortOpen•       e_waitPortClose•       e_waitRange Lock resource owner:<type-specific-description> id=lock<lock-hex-address> mode=<mode> associatedObjectId=<associated-obj-id>               <type-specific-description> can be:• For DATABASE: databaselock subresource=<databaselock-subresource> dbid=<db-id>• For FILE: filelock fileid=<file-id> subresource=<filelock-subresource> dbid=<db-id>• For OBJECT: objectlock lockPartition=<lock-partition-id> objid=<obj-id> subresource=<objectlock-subresource> dbid=<db-id>• For PAGE: pagelock fileid=<file-id> pageid=<page-id> dbid=<db-id> subresource=<pagelock-subresource>• For Key: keylock  hobtid=<hobt-id> dbid=<db-id>• For EXTENT: extentlock fileid=<file-id> pageid=<page-id> dbid=<db-id>• For RID: ridlock fileid=<file-id> pageid=<page-id> dbid=<db-id>• For APPLICATION: applicationlock hash=<hash> databasePrincipalId=<role-id> dbid=<db-id>• For METADATA: metadatalock subresource=<metadata-subresource> classid=<metadatalock-description> dbid=<db-id>• For HOBT: hobtlock hobtid=<hobt-id> subresource=<hobt-subresource> dbid=<db-id>• For ALLOCATION_UNIT: allocunitlock hobtid=<hobt-id> subresource=<alloc-unit-subresource> dbid=<db-id> <mode> can be:• Sch-S• Sch-M• S• U• X• IS• IU• IX• SIU• SIX• UIX• BU• RangeS-S• RangeS-U• RangeI-N• RangeI-S• RangeI-U• RangeI-X• RangeX-S• RangeX-U• RangeX-X External resource owner:•       External ExternalResource=<wait-type> Generic resource owner:•       TransactionMutex TransactionInfo Workspace=<workspace-id>•       Mutex•       CLRTaskJoin•       CLRMonitorEvent•       CLRRWLockEvent•       resourceWait Latch resource owner:•       <db-id>:<file-id>:<page-in-file>•       <GUID>•       <latch-class> (<latch-address>)   Further Information Slava Oks's weblog: sys.dm_os_waiting_tasks.Informit.com: Identifying Blocking Using sys.dm_os_waiting_tasks - Ken Henderson   - Guy

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• PASS Summit 2011 &ndash; Part III

  - by Tara Kizer

  Well we’re about a month past PASS Summit 2011, and yet I haven’t finished blogging my notes! Between work and home life, I haven’t been able to come up for air in a bit.  Now on to my notes… On Thursday of the PASS Summit 2011, I attended Klaus Aschenbrenner’s (blog|twitter) “Advanced SQL Server 2008 Troubleshooting”, Joe Webb’s (blog|twitter) “SQL Server Locking & Blocking Made Simple”, Kalen Delaney’s (blog|twitter) “What Happened? Exploring the Plan Cache”, and Paul Randal’s (blog|twitter) “More DBA Mythbusters”.  I think my head grew two times in size from the Thursday sessions.  Just WOW! I took a ton of notes in Klaus' session.  He took a deep dive into how to troubleshoot performance problems.  Here is how he goes about solving a performance problem: Start by checking the wait stats DMV System health Memory issues I/O issues I normally start with blocking and then hit the wait stats.  Here’s the wait stat query (Paul Randal’s) that I use when working on a performance problem.  He highlighted a few waits to be aware of such as WRITELOG (indicates IO subsystem problem), SOS_SCHEDULER_YIELD (indicates CPU problem), and PAGEIOLATCH_XX (indicates an IO subsystem problem or a buffer pool problem).  Regarding memory issues, Klaus recommended that as a bare minimum, one should set the “max server memory (MB)” in sp_configure to 2GB or 10% reserved for the OS (whichever comes first).  This is just a starting point though! Regarding I/O issues, Klaus talked about disk partition alignment, which can improve SQL I/O performance by up to 100%.  You should use 64kb for NTFS cluster, and it’s automatic in Windows 2008 R2. Joe’s locking and blocking presentation was a good session to really clear up the fog in my mind about locking.  One takeaway that I had no idea could be done was that you can set a timeout in T-SQL code view LOCK_TIMEOUT.  If you do this via the application, you should trap error 1222. Kalen’s session went into execution plans.  The minimum size of a plan is 24k.  This adds up fast especially if you have a lot of plans that don’t get reused much.  You can use sys.dm_exec_cached_plans to check how often a plan is being reused by checking the usecounts column.  She said that we can use DBCC FLUSHPROCINDB to clear out the stored procedure cache for a specific database.  I didn’t know we had this available, so this was great to hear.  This will be less intrusive when an emergency comes up where I’ve needed to run DBCC FREEPROCCACHE. Kalen said one should enable “optimize for ad hoc workloads” if you have an adhoc loc.  This stores only a 300-byte stub of the first plan, and if it gets run again, it’ll store the whole thing.  This helps with plan cache bloat.  I have a lot of systems that use prepared statements, and Kalen says we simulate those calls by using sp_executesql.  Cool! Paul did a series of posts last year to debunk various myths and misconceptions around SQL Server.  He continues to debunk things via “DBA Mythbusters”.  You can get a PDF of a bunch of these here.  One of the myths he went over is the number of tempdb data files that you should have.  Back in 2000, the recommendation was to have as many tempdb data files as there are CPU cores on your server.  This no longer holds true due to the numerous cores we have on our servers.  Paul says you should start out with 1/4 to 1/2 the number of cores and work your way up from there.  BUT!  Paul likes what Bob Ward (twitter) says on this topic: 8 or less cores –> set number of files equal to the number of cores Greater than 8 cores –> start with 8 files and increase in blocks of 4 One common myth out there is to set your MAXDOP to 1 for an OLTP workload with high CXPACKET waits.  Instead of that, dig deeper first.  Look for missing indexes, out-of-date statistics, increase the “cost threshold for parallelism” setting, and perhaps set MAXDOP at the query level.  Paul stressed that you should not plan a backup strategy but instead plan a restore strategy.  What are your recoverability requirements?  Once you know that, now plan out your backups. As Paul always does, he talked about DBCC CHECKDB.  He said how fabulous it is.  I didn’t want to interrupt the presentation, so after his session had ended, I asked Paul about the need to run DBCC CHECKDB on your mirror systems.  You could have data corruption occur at the mirror and not at the principal server.  If you aren’t checking for data corruption on your mirror systems, you could be failing over to a corrupt database in the case of a disaster or even a planned failover.  You can’t run DBCC CHECKDB against the mirrored database, but you can run it against a snapshot off the mirrored database.

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• Airline mess - what a journey

  - by Mike Dietrich

  What a day, what a journey ... Flew this noon from Munich to Zuerich for catch my ongoing flight to San Francisco with Swiss. And that day did start very well as Lufthansa messed up the connection flight by 42 minutes for a 35 minute flight. And as I was obviously the only passenger connection to San Francisco nobody picked me up at the airplane to bring me directly to my connection as Swiss did for the 8 passengers connection to Miami. So I missed my flight. What a start - and many thanks to Lufthansa. I was not the only one missing a connection as Lufthansa/Swiss had canceled the flight before due to "technical problems". In Zuerich Swiss did rebook me via Frankfurt with Lufthansa to board a United Airlines flight to San Francisco. "Ouch" I thought. I had my share of experience with United already as they've messed up my luggage on the way to San Francisco some years ago and it took them five (!!!) days to fly my bag over and deliver it. But actually it was the only option today. So I said "Yes". A big mistake as I've learned later on. The Frankfurt flight was delayed as well "due to a late incoming aircraft". But there was plenty of time. And I went to the Swiss counter at the gate and let them check if my baggage is on that flight to Frankfurt. They've said "Yes". Boarding the plane with a delay of 45 minutes (the typical Lufthansa delay these days) I spotted my Rimowa trolley right next to the plane on the airfield. So I was sure that it will be send to Frankfurt. In Frankfurt I went to the United counter once it did open - had to go through the passport check they do for US flights as well - and they've said "Yes, your luggage is with us". Well ... Arriving in San Francisco with just a bit of a some minutes delay and a very fast immigration procedure I saw the first bags with Priority tags getting pushed to the baggage claim - but mine was not there. I did wait ... and wait ... and wait. Well, thanks United, you did it again!!! I flew twice in the past years United Airlines - and in both cases they've messed up my luggage on the way to San Francisco. How lovely is that ... Now the real fun started again as the lady at the "Lost and Found" counter for luggage spotted my luggage in her system in Zuerich - and told me it's supposed to be sent with LH1191 to Frankfurt on Sept 27. But this was yesterday in Europe - it's already Sept 28 - and I saw my luggage in front of the airplane. So I'd suppose it's in Frankfurt already. But what could she do? Nothing but doing the awful paperwork. And "No Mr Dietrich, we don't call international numbers". Thank you, United. Next time I'll try to get a contract for a US land line in advance. They can't even tell you which plane will bring your luggage. It may be tomorrow with UA flight arriving around 4pm in SFO. I'm looking forward to some hours in the wonderful United Airlines call center waiting line. Last time I did spend 60-90 minutes every day until I got my luggage. If it takes again that long then OOW will be over by then. I love airline travel - and especially with United Airlines. And by the way ... they gave us these nice fancy packages during the flight:  That looks good - what's in that box??? Yes, really ... a bag of potato chips. Pure fat - very healthy.  I doubt that I'll ever fly United Airlines again!!!

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• .NET Code Evolution

  - by Alois Kraus

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

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• Multiple update panels and multiple postbacks cause entire page to refresh...

  - by Matt

  I'm having the same problem I had yesterday... The solution Aristos provided helped solve the problem, but I have other places sending updatepanel postbacks causing the same problem. When an update panel is updated and another request for an update is called before it has a chance to render the first updates, the entire page refreshes instead of just the update panel. I used fiddler to see what was going on and here's what happens... If I wait for the request to return before doing another request I get this: 21443|updatePanel|dnn_ctr1107_CRM_SalesTool_LeadsUpdatePanel| But if I don't wait, I get this: 66|pageRedirect||http://mysite.com/salesdashboard.aspx| The code from the previous question is still the same except I added UpdateMode="Conditional" to the update panel. Any ideas? Or is the only solution to this making sure that 2+ updates for any number of update panels (as long as they're on the same page) never happen? Thanks, Matt

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• Help calling def from class.

  - by wtzolt

  Hello, Noob question... class msgbox: def __init__(self, lbl_msg = '', dlg_title = ''): self.wTree = gtk.glade.XML('msgbox.glade') self.wTree.get_widget('dialog1').set_title(dlg_title) self.wTree.get_widget('label1').set_text(lbl_msg) self.wTree.signal_autoconnect( {'on_okbutton1_clicked':self.done} ) def done(self,w): self.wTree.get_widget('dialog1').destroy() class Fun(object): wTree = None def __init__(self): self.wTree = gtk.glade.XML( "main.glade" ) self.wTree.signal_autoconnect( {'on_buttonOne' : self.one,} ) gtk.main() @yieldsleep def one(self, widget, data=None): self.msg = msgbox('Please wait...','') yield 500 self.msg = msgbox().done() # <----------------??? self.msg = msgbox('Done!','') With this i get an error: messageBox().done() TypeError: done() takes exactly 2 arguments (1 given) How can i make the dialog box with "please wait" to close before the second dialog box with "done" appears?? Thank you.

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• How can I replace this semaphore with a monitor?

  - by Kurru

  Hi In previous question of mine, someone had meantioned that using Semaphores were expensive in C# compared to using a monitor. So I ask this, how can I replace the semaphore in this code with a monitor? I need function1 to return its value after function2 (in a separate thread) has been completed. I had replaced the Semaphore.WaitOne with a Monitor.Wait and the Semaphore.Release with a Monitor.PulseAll but the PulseAll was being triggered before the Wait causing the program to hang. Any idea how to avoid that race condition? Semaphore semaphore = new Semaphore(0,1); byte b; public byte Function1() { // new thread starting in Function2; semaphore.WaitOne(); return b; } public void Function2() { // do some thing b = 0; semaphore.Release(); }

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• How to check misspelled email during user registration

  - by Nulldevice

  I use an email registration and confirmation in my project (yes, I know about OpenID. In my counry, a main email service lack it). Sometimes users misspell their email addresses. I know about this due to "message could not be delivered" letters in a mailbox. A misspelled address is absolutely correct, because I check it with a regular expression - say, [email protected] intstead of [email protected]. And I do not want to duplicate a email field in a registration form (who likes it?). Request processing routine cannot wait for email delivery - it could take an unpredictable time. So, my script will return to user a confirmation message "An email was sent". And the user will wait for it forever (of cause, not - he/she will turn to an alternative project with a more perfect registration system). Does someone knows how it can be improved (in any programming language)?

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• Execute a function when a <link> element has finished loading

  - by nornagon

  I'm using jQuery Masonry to lay out my page, but I'm using a custom @font-face font. The problem being that Masonry doesn't know the metrics of the font until it's loaded. The Masonry docs suggest that you use $(window).load() instead of $(document).ready() to call the layout functions, but I don't want to have to wait until all the images etc. load. I can specify the dimensions of the images exactly, so Masonry doesn't need to wait until they're loaded. It's just the text that's the problem. How can I get jQuery to call a callback when the <link> element that links in the font finishes loading?

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• is there any light weight javascript date picker

  - by Zain Shaikh

  I am using JQuery Date picker, but it is too much heavy, the minified version of ui.datepicker.min.js is of 44 KB. the images of datepicker have their own weigh. the jquery framework is of 59 KB. and total images on page are of around 80 KB the total html of page is around 70 KB and the css file size is around 72 KB. and much more, and all the things go upto 600 KB. which is 0.6 MB. do you think user will wait for 600 KB to be downloaded in the browser? it may take upto 8 - 10 secs. and I dont think that user will wait for such long time. I want to keep my website light weight. is there any light weight javascript date picker.

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• how to preload more than one but not all images of a slideshow with jquery

  - by wtip

  I'd like to create a web based stop motion video player. Basically a slideshow that shows 2-4 images per second. Each image might be a maximum of 20KB. I don't want to preload all images in the slideshow as there might be thousands, however I need to preload more than just the next image in the show as this will not playback fast enough (because of the playback speed the browser needs to be loading more than one image at a time). I've been looking at using the jQuery Cycle Plugin (http://malsup.com/jquery/cycle/) with a addSlide type function but don't know how to make it work. Would something like this might work? -Slideshow starts -image is played back -preloader will attempt to load up to the next 60 images -playback will wait for the next image in line to completely load, but will not wait for all 59 others. The playback / preloading order is important for this application.

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• MSDN Example of handling an exception from the TPL - Is this a race condition?

  - by David

  I'm looking at the TPL exception handling example from MSDN @ http://msdn.microsoft.com/en-us/library/dd537614(v=VS.100).aspx The basic form of the code is: Task task1 = Task.Factory.StartNew(() => { throw new IndexOutOfRangeException(); }); try { task1.Wait(); } catch (AggregateException ae) { throw ae.Flatten(); } My question is: Is this a race condition? What happens if task1 throws before the try has executed? Am I missing something that stops this being a race? Shouldn't it be written like this instead: try { Task task1 = Task.Factory.StartNew(() => { throw new IndexOutOfRangeException(); }); task1.Wait(); } catch (AggregateException ae) { throw ae.Flatten(); }

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• Error releasing Grails plugin

  - by Don

  Hi, I checked out the trunk of my plugin from the Grails svn repo, made some changes, incremented the version number to 0.2.1, then ran release-plugin. It failed with the error shown below: Checking in plugin zip... Updating from SVN... Updated to revision 61343. Committing local, please wait... Enter a SVN commit message: Fixed bug with controller dependency version and upgraded to grails 1.2.2 Committing code. Please wait... Failed to stat working directory: svn: Commit failed (details follow): svn: Authentication required for '<https://svn.codehaus.org:443> grails-plugins primary Subversion repository' Application context shutting down... Application context shutdown. It's possible that my password is not correct, but I'm pretty sure it is. Does anyone know what the problem could be, and is there some way I can verify that the password I'm using is correct?

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• take out objects from randomizer obj c

  - by David Pollak

  hello everyone, I'm a new "developer" trying to build some iPhone app I'm making an app which gets text from a list of objects in a NSArray and then randomizes them and display one in a TextView, here's the code: - (IBAction)azione{ NSArray *myArray= [NSArray arrayWithObjects: @"Pasta",@"Pizza",@"Wait",@"Go", nil]; int length = [myArray count]; int chosen = arc4random() % length; testo.text = [myArray objectAtIndex: chosen]; } what I want to do now, is when I open the app and get a random object, to take it out from the list, so that it won't be picked again ex. I open the appI get "Pizza"Do the action againI don't get "Pizza" anymore, only "Pasta" "Wait" and "Go" What should I do ? Which code should I use ? Thanks for answers

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• Navigate touch-tone menus via modem

  - by Kongress

  I have a system that I need to programmatically interface with that requires a set of numbers to be dialed after the phone line is picked up, like a standard automated phone answering system. For instance, dial the number 123-456-7890, wait for the line to be answered, wait 15 seconds for the voice prompt, dial 1234#, hang up. The question is, can I and how do I do that through a modem? I know how to dial a number through a modem, it's simply ATDT[phone number], but that will attempt to initiate a data connection which will not allow touch-tone number entry. Would a voice modem provide the necessary capability? If so, could anyone provide example commands to accomplish this?

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• Simple, non-blocking way to sleep?

  - by OverTheRainbow

  Hello I googled for this and read some threads here, but I haven't found a simple way to have a VB.Net application sleep for a little while and still keep the application responsive: Imports System.Net Imports System.IO Imports System.Text Imports System.Text.RegularExpressions Imports System.Threading.Thread [...] 'How to keep screen frop freezing? While True ListBox1.Items.Clear() ListBox1.Items.Add("blah") 'Not much difference ListBox1.Refresh() 'Wait 1mn Sleep(60000) End While Is there really no simple, non-blocking solution to have a VB.Net application wait for a few seconds? Thank you.

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• How to know when a pop-down menu needs to be closed

  - by Pieter

  I'm experimenting with pop-down menus (inside floating DIVs). Making them appear with onmouseover attributes is no problem, but I'm not sure how I can make the menu close properly. I figured the best way to know when to close the menu is wait until the mouse is no longer hovering over the HTML element that called the menu or the menu itself, then wait one second, and then close the menu. Is my idea something that can be implemented, perhaps with some jQuery? Or is there a better and more efficient alternative?

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