win 16 subsystem - Page 70

mips number of clock cycles and how improving code

- by Hooman

I'm really new in MIPS and I have these questions which I found so many dissimil answers for them ... if someone can help, it would be great. Thanks How many clock cycles does this code take? #Macro Instructions li $t0, 32 # 1 or 2 cycles ? # lui $at, Upper 16-bits of value # ori Rd, $at, Lower 16-bits of value # ----------------------------------- # ori Rt, $0, value # # Which set of instructions will be executed? div $t2, $t2, $t0 # 41 cycles? # bne Rt, $0, # break $0 # ok: div Rs, Rt # mflo Rd #Integer Instruction lw $t2, 0($t13) # 1 cycles? sw $t2, 0($t3) # 1 cycles? How those 4 lines of codes can be significantly improved? by avoiding to use Macros or ... ?

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Demo on Data Guard Protection From Lost-Write Corruption

- by Rene Kundersma

Today I received the news a new demo has been made available on OTN for Data Guard protection from lost-write corruption. Since this is a typical MAA solution and a very nice demo I decided to mention this great feature also in this blog even while it's a recommended best practice for some time. When lost writes occur an I/O subsystem acknowledges the completion of the block write even though the write I/O did not occur in the persistent storage. On a subsequent block read on the primary database, the I/O subsystem returns the stale version of the data block, which might be used to update other blocks of the database, thereby corrupting it. Lost writes can occur after an OS or storage device driver failure, faulty host bus adapters, disk controller failures and volume manager errors. In the demo a data block lost write occurs when an I/O subsystem acknowledges the completion of the block write, while in fact the write did not occur in the persistent storage. When a primary database lost write corruption is detected by a Data Guard physical standby database, Redo Apply (MRP) will stop and the standby will signal an ORA-752 error to explicitly indicate a primary lost write has occurred (preventing corruption from spreading to the standby database). Links: MOS (1302539.1). "Best Practices for Corruption Detection, Prevention, and Automatic Repair - in a Data Guard Configuration" Demo MAA Best Practices Rene Kundersma

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2D Platformer Collision Handling

- by defender-zone

Hello, everyone! I am trying to create a 2D platformer (Mario-type) game and I am some having some issues with handling collisions properly. I am writing this game in C++, using SDL for input, image loading, font loading, etcetera. I am also using OpenGL via the FreeGLUT library in conjunction with SDL to display graphics. My method of collision detection is AABB (Axis-Aligned Bounding Box), which is really all I need to start with. What I need is an easy way to both detect which side the collision occurred on and handle the collisions properly. So, basically, if the player collides with the top of the platform, reposition him to the top; if there is a collision to the sides, reposition the player back to the side of the object; if there is a collision to the bottom, reposition the player under the platform. I have tried many different ways of doing this, such as trying to find the penetration depth and repositioning the player backwards by the penetration depth. Sadly, nothing I've tried seems to work correctly. Player movement ends up being very glitchy and repositions the player when I don't want it to. Part of the reason is probably because I feel like this is something so simple but I'm over-thinking it. If anyone thinks they can help, please take a look at the code below and help me try to improve on this if you can. I would like to refrain from using a library to handle this (as I want to learn on my own) or the something like the SAT (Separating Axis Theorem) if at all possible. Thank you in advance for your help! void world1Level1CollisionDetection() { for(int i; i < blocks; i++) { if (de2dCheckCollision(ball,block[i],0.0f,0.0f)==true) { int up = 0; int left = 0; int right = 0; int down = 0; if(ball.coords[0] < block[i].coords[0] && block[i].coords[0] < ball.coords[2] && ball.coords[2] < block[i].coords[2]) { left = 1; } if(block[i].coords[0] < ball.coords[0] && ball.coords[0] < block[i].coords[2] && block[i].coords[2] < ball.coords[2]) { right = 1; } if(ball.coords[1] < block[i].coords[1] && block[i].coords[1] < ball.coords[3] && ball.coords[3] < block[i].coords[3]) { up = 1; } if(block[i].coords[1] < ball.coords[1] && ball.coords[1] < block[i].coords[3] && block[i].coords[3] < ball.coords[3]) { down = 1; } cout << left << ", " << right << ", " << up << ", " << down << ", " << endl; if (left == 1) { ball.coords[0] = block[i].coords[0] - 16.0f; ball.coords[2] = block[i].coords[0] - 0.0f; } if (right == 1) { ball.coords[0] = block[i].coords[2] + 0.0f; ball.coords[2] = block[i].coords[2] + 16.0f; } if (down == 1) { ball.coords[1] = block[i].coords[3] + 0.0f; ball.coords[3] = block[i].coords[3] + 16.0f; } if (up == 1) { ball.yspeed = 0.0f; ball.gravity = 0.0f; ball.coords[1] = block[i].coords[1] - 16.0f; ball.coords[3] = block[i].coords[1] - 0.0f; } } if (de2dCheckCollision(ball,block[i],0.0f,0.0f)==false) { ball.gravity = -0.5f; } } } To explain what some of this code means: The blocks variable is basically an integer that is storing the amount of blocks, or platforms. I am checking all of the blocks using a for loop, and the number that the loop is currently on is represented by integer i. The coordinate system might seem a little weird, so that's worth explaining. coords[0] represents the x position (left) of the object (where it starts on the x axis). coords[1] represents the y position (top) of the object (where it starts on the y axis). coords[2] represents the width of the object plus coords[0] (right). coords[3] represents the height of the object plus coords[1] (bottom). de2dCheckCollision performs an AABB collision detection. Up is negative y and down is positive y, as it is in most games. Hopefully I have provided enough information for someone to help me successfully. If there is something I left out that might be crucial, let me know and I'll provide the necessary information. Finally, for anyone who can help, providing code would be very helpful and much appreciated. Thank you again for your help!

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Don't Miss At Devoxx!!!

- by Yolande Poirier

Come by IoT Hack Fest which starts with the session: kickstart your Raspberry Pi and/or Leap Motion project, part II on Tuesday from 9:30am to 12:00pm to learn how to start a project with the Raspberry Pi and Leap Motion. In the afternoon, you can still join a project and create your own project with the help of experts on Raspberry Pi, Leap Motion and other boards. At the Oracle booth, Java experts will be available to answer your questions and demo the new features of the Java Platform, including Java Embedded, JavaFX, Java SE and Java EE. This year, the chess game that was first demoed at JavaOne keynotes last September will be showcased at Devoxx. Duke is coming to Devoxx this year. You can get your picture taken with Duke on Tuesday, Wednesday and Thursday (Nov. 12-14) from 12:00 to 18:00 Beer bash will be Tuesday from 17:30-19:30 and Wednesday/Thursday from 18:00 to 20:00 at the booth. Oracle is raffling off five Raspberry Pi's and a number of books every day. Make sure to stop by and get your badge scanned to enter the raffle. Raffles are Tuesday at 19:15 and Wednesday/Thursday at 19:45 at the Oracle booth. The main conference sessions from Oracle Java experts are: Wednesday 13 November Beyond Beauty: JavaFX, Parallax, Touch, Raspberry Pi, Gyroscopes, and Much More Angela Caicedo, Senior Member, Technical Staff, Oracle Room 7, 12:00–13:00 Lambda: A Peek Under the Hood, Brian Goetz, Software Architect, Oracle Room 8, 12:00–13:00 In Full Flow: Java 8 Lambdas in the Stream, Paul Sandoz, Software Developer, Oracle Room 8, 14:00–15:00 The Modular Java Platform and Project Jigsaw, Mark Reinhold, Chief Architect, Java Platform Group, Oracle, Room 8, 15:10–16:10 The Curious Case of JavaScript on the JVM, Attila Szegedi, Principal Member, Technical Staff, Oracle, Room 5, 16:40–17:40 Is It a Car? Is It a Computer? No, It’s a Raspberry Pi JavaFX Informatics System. Simon Ritter, Principal Technology Evangelist, Oracle Room 7, 16:40–17:40 Thursday 14 November Java EE 7: What’s New in the Java EE Platform Linda DeMichiel, Consulting Member, Technical Staff, Oracle, Room 8, 10:50–11:50 Java Microbenchmark Harness: The Lesser of the Two Evils, Aleksey Shipilev, Principal Member, Technical Staff, Oracle. Room 6, 14:00–15:00 Practical Restful Persistence, Shaun Smith, Senior Principal Product Manager, Oracle Room 8, 17:50–18:50 Friday 15 November Avatar.js, Server-Side JavaScript on the Java Platform, Jean-Francois Denise, Software Developer, Oracle Room 8, 11:50–12:50

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Monitor resolution messed up, monitor is unknown.

- by Kaustubh P

Is there anyway to reset my monitor? My moitor is using the xorg.conf file. I use 10.04, without any Graphics Card. My monitor is an Acer X193W, with a native resolution of 1440x900. This is my xorg.conf file: Section "Screen" Identifier "Configured Screen Device" Device "Configured Video Device" Monitor "Test" DefaultDepth 16 SubSection "Display" Depth 16 Modes "1440x900_60.00" EndSubSection EndSection #Section "Device" # Identifier "Configured Video Device" # HorizSync # VertRefresh #EndSection I still cant view the native resolution, even when defined in the xorg file. An way I can revert to the default, or delete some files, to make the system detect the monitor again? My last resort is the cvt method, and adding it to the xrandr file. EDIT: I use Intel Drivers. My /proc/fb contains 0 VGA16 VGA

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The Joy Of Hex

- by Jim Giercyk

While working on a mainframe integration project, it occurred to me that some basic computer concepts are slipping into obscurity. For example, just about anyone can tell you that a 64-bit processor is faster than a 32-bit processer. A grade school child could tell you that a computer “speaks” in ‘1’s and ‘0’s. Some people can even tell you that there are 8 bits in a byte. However, I have found that even the most seasoned developers often can’t explain the theory behind those statements. That is not a knock on programmers; in the age of IntelliSense, what reason do we have to work with data at the bit level? Many computer theory classes treat bit-level programming as a thing of the past, no longer necessary now that storage space is plentiful. The trouble with that mindset is that the world is full of legacy systems that run programs written in the 1970’s. Today our jobs require us to extract data from those systems, regardless of the format, and that often involves low-level programming. Because it seems knowledge of the low-level concepts is waning in recent times, I thought a review would be in order. CHARACTER: See Spot Run HEX: 53 65 65 20 53 70 6F 74 20 52 75 6E DECIMAL: 83 101 101 32 83 112 111 116 32 82 117 110 BINARY: 01010011 01100101 01100101 00100000 01010011 01110000 01101111 01110100 00100000 01010010 01110101 01101110 In this example, I have broken down the words “See Spot Run” to a level computers can understand – machine language. CHARACTER: The character level is what is rendered by the computer. A “Character Set” or “Code Page” contains 256 characters, both printable and unprintable. Each character represents 1 BYTE of data. For example, the character string “See Spot Run” is 12 Bytes long, exclusive of the quotation marks. Remember, a SPACE is an unprintable character, but it still requires a byte. In the example I have used the default Windows character set, ASCII, which you can see here: http://www.asciitable.com/ HEX: Hex is short for hexadecimal, or Base 16. Humans are comfortable thinking in base ten, perhaps because they have 10 fingers and 10 toes; fingers and toes are called digits, so it’s not much of a stretch. Computers think in Base 16, with numeric values ranging from zero to fifteen, or 0 – F. Each decimal place has a possible 16 values as opposed to a possible 10 values in base 10. Therefore, the number 10 in Hex is equal to the number 16 in Decimal. DECIMAL: The Decimal conversion is strictly for us humans to use for calculations and conversions. It is much easier for us humans to calculate that [30 – 10 = 20] in decimal than it is for us to calculate [1E – A = 14] in Hex. In the old days, an error in a program could be found by determining the displacement from the entry point of a module. Since those values were dumped from the computers head, they were in hex. A programmer needed to convert them to decimal, do the equation and convert back to hex. This gets into relative and absolute addressing, a topic for another day. BINARY: Binary, or machine code, is where any value can be expressed in 1s and 0s. It is really Base 2, because each decimal place can have a possibility of only 2 characters, a 1 or a 0. In Binary, the number 10 is equal to the number 2 in decimal. Why only 1s and 0s? Very simply, computers are made up of lots and lots of transistors which at any given moment can be ON ( 1 ) or OFF ( 0 ). Each transistor is a bit, and the order that the transistors fire (or not fire) is what distinguishes one value from another in the computers head (or CPU). Consider 32 bit vs 64 bit processing…..a 64 bit processor has the capability to read 64 transistors at a time. A 32 bit processor can only read half as many at a time, so in theory the 64 bit processor should be much faster. There are many more factors involved in CPU performance, but that is the fundamental difference. DECIMAL HEX BINARY 0 0 0000 1 1 0001 2 2 0010 3 3 0011 4 4 0100 5 5 0101 6 6 0110 7 7 0111 8 8 1000 9 9 1001 10 A 1010 11 B 1011 12 C 1100 13 D 1101 14 E 1110 15 F 1111 Remember that each character is a BYTE, there are 2 HEX characters in a byte (called nibbles) and 8 BITS in a byte. I hope you enjoyed reading about the theory of data processing. This is just a high-level explanation, and there is much more to be learned. It is safe to say that, no matter how advanced our programming languages and visual studios become, they are nothing more than a way to interpret bits and bytes. There is nothing like the joy of hex to get the mind racing.

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my webserver with 16GB ram shows all RAM as used, but is it really, see the 'top'

- by Alex

I have some questions about my web server. Its a LAMP web server running centos 5.5 and php5, mysql5. The server gets hundreds (maybe thousand) of concurrent users during peak hours. I'm trying to optimize a little and understand "top". From what I can see: all 16GB of my ram have been used up? does that mean that my server needs more memory? My swap is only 2GB, should it be increased? usually during peak hours my server load average first number is about 2.5-3. What could I do to optimize the server so that the load average even during peak doesn't go above 1? In the past I was told a good working server should stay under 1 load, is this still true? Although even during load of 2.5-3, server pages and applications seem to load with pretty good speed. what should the memory size in php.ini be set to? top - 14:30:18 up 2 days, 12:41, 5 users, load average: 1.25, 1.74, 2.92 Tasks: 305 total, 2 running, 302 sleeping, 0 stopped, 1 zombie Cpu(s): 6.3%us, 0.9%sy, 0.0%ni, 92.5%id, 0.2%wa, 0.0%hi, 0.1%si, 0.0%st Mem: 16427200k total, 16111472k used, 315728k free, 3120316k buffers Swap: 2104496k total, 268k used, 2104228k free, 6216756k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 29080 apache 15 0 358m 36m 5192 S 20.2 0.2 2:08.40 httpd 29093 apache 18 0 357m 36m 5192 S 18.2 0.2 2:02.52 httpd 29079 apache 15 0 370m 49m 5832 S 10.0 0.3 2:32.14 httpd 1812 apache 15 0 370m 49m 5196 S 7.3 0.3 2:25.30 httpd 5204 apache 15 0 358m 36m 5168 S 5.3 0.2 0:59.28 httpd 29075 apache 15 0 370m 48m 5184 S 3.3 0.3 2:15.93 httpd 9712 apache 15 0 360m 38m 5180 S 3.0 0.2 0:54.81 httpd 29072 apache 16 0 358m 36m 5192 S 2.7 0.2 2:24.43 httpd 6310 apache 17 0 388m 67m 5180 S 2.3 0.4 0:58.85 httpd 8674 apache 15 0 343m 21m 4980 S 2.0 0.1 0:07.91 httpd 29085 apache 15 0 371m 49m 5224 S 2.0 0.3 2:16.86 httpd 29083 apache 15 0 370m 48m 5196 S 1.7 0.3 2:10.64 httpd 5575 apache 15 0 357m 36m 5228 S 1.3 0.2 0:53.78 httpd 29066 apache 15 0 379m 59m 5860 R 1.3 0.4 2:11.93 httpd 29078 apache 15 0 370m 48m 5188 S 1.3 0.3 2:14.52 httpd 29084 apache 15 0 370m 48m 5208 S 1.0 0.3 2:02.49 httpd 29089 apache 15 0 370m 48m 5188 S 1.0 0.3 2:27.61 httpd 29082 apache 15 0 390m 68m 5188 S 0.7 0.4 2:32.48 httpd 29984 apache 15 0 358m 36m 5228 S 0.7 0.2 2:08.32 httpd 3571 root 16 0 13400 1792 848 S 0.3 0.0 2:37.89 top 4419 mysql 15 0 668m 175m 7204 S 0.3 1.1 3:32.25 mysqld 28181 root 15 0 90460 3624 2680 S 0.3 0.0 0:17.60 sshd 29091 apache 15 0 390m 69m 5196 S 0.3 0.4 2:29.99 httpd 32476 root 15 0 12900 1320 848 R 0.3 0.0 0:06.46 top 1 root 15 0 10372 680 572 S 0.0 0.0 0:02.01 init 2 root RT -5 0 0 0 S 0.0 0.0 0:00.51 migration/0 3 root 34 19 0 0 0 S 0.0 0.0 0:00.07 ksoftirqd/0 4 root RT -5 0 0 0 S 0.0 0.0 0:00.00 watchdog/0 5 root RT -5 0 0 0 S 0.0 0.0 0:00.12 migration/1 6 root 34 19 0 0 0 S 0.0 0.0 0:00.03 ksoftirqd/1 7 root RT -5 0 0 0 S 0.0 0.0 0:00.00 watchdog/1 8 root RT -5 0 0 0 S 0.0 0.0 0:00.06 migration/2 9 root 34 19 0 0 0 S 0.0 0.0 0:00.03 ksoftirqd/2 10 root RT -5 0 0 0 S 0.0 0.0 0:00.00 watchdog/2 11 root RT -5 0 0 0 S 0.0 0.0 0:00.06 migration/3 12 root 34 19 0 0 0 S 0.0 0.0 0:00.04 ksoftirqd/3 13 root RT -5 0 0 0 S 0.0 0.0 0:00.00 watchdog/3 14 root RT -5 0 0 0 S 0.0 0.0 0:01.45 migration/4 15 root 34 19 0 0 0 S 0.0 0.0 0:00.01 ksoftirqd/4 16 root RT -5 0 0 0 S 0.0 0.0 0:00.00 watchdog/4 17 root RT -5 0 0 0 S 0.0 0.0 0:00.22 migration/5 18 root 34 19 0 0 0 S 0.0 0.0 0:00.01 ksoftirqd/5 19 root RT -5 0 0 0 S 0.0 0.0 0:00.00 watchdog/5 20 root RT -5 0 0 0 S 0.0 0.0 0:00.15 migration/6 21 root 34 19 0 0 0 S 0.0 0.0 0:00.02 ksoftirqd/6 22 root RT -5 0 0 0 S 0.0 0.0 0:00.00 watchdog/6 23 root RT -5 0 0 0 S 0.0 0.0 0:00.15 migration/7 24 root 34 19 0 0 0 S 0.0 0.0 0:00.01 ksoftirqd/7 25 root RT -5 0 0 0 S 0.0 0.0 0:00.00 watchdog/7 26 root RT -5 0 0 0 S 0.0 0.0 0:00.19 migration/8 27 root 34 19 0 0 0 S 0.0 0.0 0:00.04 ksoftirqd/8 28 root RT -5 0 0 0 S 0.0 0.0 0:00.00 watchdog/8 29 root RT -5 0 0 0 S 0.0 0.0 0:00.34 migration/9 30 root 34 19 0 0 0 S 0.0 0.0 0:00.03 ksoftirqd/9 31 root RT -5 0 0 0 S 0.0 0.0 0:00.00 watchdog/9 32 root RT -5 0 0 0 S 0.0 0.0 0:00.16 migration/10 33 root 34 19 0 0 0 S 0.0 0.0 0:00.04 ksoftirqd/10 34 root RT -5 0 0 0 S 0.0 0.0 0:00.00 watchdog/10 35 root RT -5 0 0 0 S 0.0 0.0 0:00.12 migration/11 36 root 34 19 0 0 0 S 0.0 0.0 0:00.05 ksoftirqd/11 37 root RT -5 0 0 0 S 0.0 0.0 0:00.00 watchdog/11 38 root RT -5 0 0 0 S 0.0 0.0 0:00.35 migration/12

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IPTables masquerading with one NIC

- by Tuinslak

Hi, I am running an OpenVPN server with only one NIC. This is my current layout: public.ip > Cisco firewall > lan.ip > OpenVPN server lan.ip = 192.168.22.70 The Cisco firewall forwards the requests to the oVPN server, thus so far everything works and clients are able to connect. However, all clients connected should be able to access 3 networks: lan1: 192.168.200.0 (vpn lan) > tun0 lan2: 192.168.110.0 (office lan) > eth1 (gw 192.168.22.1) lan3: 192.168.22.0 (server lan) > eth1 (broadcast network) So tun0 is mapped to eth1. Iptables output: # iptables-save # Generated by iptables-save v1.4.2 on Wed Feb 16 14:14:20 2011 *filter :INPUT ACCEPT [327:26098] :FORWARD DROP [305:31700] :OUTPUT ACCEPT [291:27378] -A INPUT -i lo -j ACCEPT -A INPUT -i tun0 -j ACCEPT -A INPUT -i ! tun0 -p udp -m udp --dport 67 -j REJECT --reject-with icmp-port-unreachable -A INPUT -i ! tun0 -p udp -m udp --dport 53 -j REJECT --reject-with icmp-port-unreachable -A FORWARD -d 192.168.200.0/24 -i tun0 -j DROP -A FORWARD -s 192.168.200.0/24 -i tun0 -j ACCEPT -A FORWARD -d 192.168.200.0/24 -i eth1 -j ACCEPT COMMIT # Completed on Wed Feb 16 14:14:20 2011 # Generated by iptables-save v1.4.2 on Wed Feb 16 14:14:20 2011 *nat :PREROUTING ACCEPT [302:26000] :POSTROUTING ACCEPT [3:377] :OUTPUT ACCEPT [49:3885] -A POSTROUTING -o eth1 -j MASQUERADE COMMIT # Completed on Wed Feb 16 14:14:20 2011 Yet, clients are unable to ping any ip (including 192.168.200.1, which is the oVPN's IP) When the machine was directly connected to the internet, with 2 NICs, it was quite simply solved with masquerading and adding static routes in the oVPN client's config. However, as masquerading won't accept virtual interfaces (eth0:0, etc) I am unable to get masquerading to work again (and I'm not even sure whether I need virtual interfaces). Thanks. Edit: OpenVPN server: # ifconfig eth1 Link encap:Ethernet HWaddr ba:e6:64:ec:57:ac inet addr:192.168.22.70 Bcast:192.168.22.255 Mask:255.255.255.0 inet6 addr: fe80::b8e6:64ff:feec:57ac/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:6857 errors:0 dropped:0 overruns:0 frame:0 TX packets:4044 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:584046 (570.3 KiB) TX bytes:473691 (462.5 KiB) Interrupt:14 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:334 errors:0 dropped:0 overruns:0 frame:0 TX packets:334 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:33773 (32.9 KiB) TX bytes:33773 (32.9 KiB) tun0 Link encap:UNSPEC HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00 inet addr:192.168.200.1 P-t-P:192.168.200.2 Mask:255.255.255.255 UP POINTOPOINT RUNNING NOARP MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:100 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) ifconfig on a client: # ifconfig eth0 Link encap:Ethernet HWaddr 00:22:64:71:11:56 inet addr:192.168.110.94 Bcast:192.168.110.255 Mask:255.255.255.0 inet6 addr: fe80::222:64ff:fe71:1156/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:3466 errors:0 dropped:0 overruns:0 frame:0 TX packets:1838 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:997924 (974.5 KiB) TX bytes:332406 (324.6 KiB) Interrupt:17 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:37847 errors:0 dropped:0 overruns:0 frame:0 TX packets:37847 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:2922444 (2.7 MiB) TX bytes:2922444 (2.7 MiB) tun0 Link encap:UNSPEC HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00 inet addr:192.168.200.30 P-t-P:192.168.200.29 Mask:255.255.255.255 UP POINTOPOINT RUNNING NOARP MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:689 errors:0 dropped:18 overruns:0 carrier:0 collisions:0 txqueuelen:100 RX bytes:0 (0.0 B) TX bytes:468778 (457.7 KiB) wlan0 Link encap:Ethernet HWaddr 00:16:ea:db:ae:86 UP BROADCAST MULTICAST MTU:1500 Metric:1 RX packets:704699 errors:0 dropped:0 overruns:0 frame:0 TX packets:730176 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:520385963 (496.2 MiB) TX bytes:225210422 (214.7 MiB) static routes line at the end of the client's config (I've been playing around with the 192.168.200.0 -- (un)commenting to see if anything changes): route 192.168.200.0 255.255.255.0 route 192.168.110.0 255.255.255.0 route 192.168.22.0 255.255.255.0 route on a vpn client: # route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 192.168.200.29 0.0.0.0 255.255.255.255 UH 0 0 0 tun0 192.168.22.0 192.168.200.29 255.255.255.0 UG 0 0 0 tun0 192.168.200.0 192.168.200.29 255.255.255.0 UG 0 0 0 tun0 192.168.110.0 192.168.200.29 255.255.255.0 UG 0 0 0 tun0 192.168.110.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 0.0.0.0 192.168.110.1 0.0.0.0 UG 0 0 0 eth0 edit: Weirdly enough, if I set push "redirect-gateway def1" in the server config, (and thus routes all traffic through VPN, which is not what I want), it seems to work.

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Azure – Part 5 – Repository Pattern for Table Service

- by Shaun

In my last post I created a very simple WCF service with the user registration functionality. I created an entity for the user data and a DataContext class which provides some methods for operating the entities such as add, delete, etc. And in the service method I utilized it to add a new entity into the table service. But I didn’t have any validation before registering which is not acceptable in a real project. So in this post I would firstly add some validation before perform the data creation code and show how to use the LINQ for the table service. LINQ to Table Service Since the table service utilizes ADO.NET Data Service to expose the data and the managed library of ADO.NET Data Service supports LINQ we can use it to deal with the data of the table service. Let me explain with my current example: I would like to ensure that when register a new user the email address should be unique. So I need to check the account entities in the table service before add. If you remembered, in my last post I mentioned that there’s a method in the TableServiceContext class – CreateQuery, which will create a IQueryable instance from a given type of entity. So here I would create a method under my AccountDataContext class to return the IQueryable<Account> which named Load. 1: public class AccountDataContext : TableServiceContext 2: { 3: private CloudStorageAccount _storageAccount; 4: 5: public AccountDataContext(CloudStorageAccount storageAccount) 6: : base(storageAccount.TableEndpoint.AbsoluteUri, storageAccount.Credentials) 7: { 8: _storageAccount = storageAccount; 9: 10: var tableStorage = new CloudTableClient(_storageAccount.TableEndpoint.AbsoluteUri, 11: _storageAccount.Credentials); 12: tableStorage.CreateTableIfNotExist("Account"); 13: } 14: 15: public void Add(Account accountToAdd) 16: { 17: AddObject("Account", accountToAdd); 18: SaveChanges(); 19: } 20: 21: public IQueryable<Account> Load() 22: { 23: return CreateQuery<Account>("Account"); 24: } 25: } The method returns the IQueryable<Account> so that I can perform the LINQ operation on it. And back to my service class, I will use it to implement my validation. 1: public bool Register(string email, string password) 2: { 3: var storageAccount = CloudStorageAccount.FromConfigurationSetting("DataConnectionString"); 4: var accountToAdd = new Account(email, password) { DateCreated = DateTime.Now }; 5: var accountContext = new AccountDataContext(storageAccount); 6: 7: // validation 8: var accountNumber = accountContext.Load() 9: .Where(a => a.Email == accountToAdd.Email) 10: .Count(); 11: if (accountNumber > 0) 12: { 13: throw new ApplicationException(string.Format("Your account {0} had been used.", accountToAdd.Email)); 14: } 15: 16: // create entity 17: try 18: { 19: accountContext.Add(accountToAdd); 20: return true; 21: } 22: catch (Exception ex) 23: { 24: Trace.TraceInformation(ex.ToString()); 25: } 26: return false; 27: } I used the Load method to retrieve the IQueryable<Account> and use Where method to find the accounts those email address are the same as the one is being registered. If it has I through an exception back to the client side. Let’s run it and test from my simple client application. Oops! Looks like we encountered an unexpected exception. It said the “Count” is not support by the ADO.NET Data Service LINQ managed library. That is because the table storage managed library (aka. TableServiceContext) is based on the ADO.NET Data Service and it supports very limit LINQ operation. Although I didn’t find a full list or documentation about which LINQ methods it supports I could even refer a page on msdn here. It gives us a roughly summary of which query operation the ADO.NET Data Service managed library supports and which doesn't. As you see the Count method is not in the supported list. Not only the query operation, there inner lambda expression in the Where method are limited when using the ADO.NET Data Service managed library as well. For example if you added (a => !a.DateDeleted.HasValue) in the Where method to exclude those deleted account it will raised an exception said "Invalid Input". Based on my experience you should always use the simple comparison (such as ==, >, <=, etc.) on the simple members (such as string, integer, etc.) and do not use any shortcut methods (such as string.Compare, string.IsNullOrEmpty etc.). 1: // validation 2: var accountNumber = accountContext.Load() 3: .Where(a => a.Email == accountToAdd.Email) 4: .ToList() 5: .Count; 6: if (accountNumber > 0) 7: { 8: throw new ApplicationException(string.Format("Your account {0} had been used.", accountToAdd.Email)); 9: } We changed the a bit and try again. Since I had created an account with my mail address so this time it gave me an exception said that the email had been used, which is correct. Repository Pattern for Table Service The AccountDataContext takes the responsibility to save and load the account entity but only for that specific entity. Is that possible to have a dynamic or generic DataContext class which can operate any kinds of entity in my system? Of course yes. Although there's no typical database in table service we can threat the entities as the records, similar with the data entities if we used OR Mapping. As we can use some patterns for ORM architecture here we should be able to adopt the one of them - Repository Pattern in this example. We know that the base class - TableServiceContext provide 4 methods for operating the table entities which are CreateQuery, AddObject, UpdateObject and DeleteObject. And we can create a relationship between the enmity class, the table container name and entity set name. So it's really simple to have a generic base class for any kinds of entities. Let's rename the AccountDataContext to DynamicDataContext and make the type of Account as a type parameter if it. 1: public class DynamicDataContext<T> : TableServiceContext where T : TableServiceEntity 2: { 3: private CloudStorageAccount _storageAccount; 4: private string _entitySetName; 5: 6: public DynamicDataContext(CloudStorageAccount storageAccount) 7: : base(storageAccount.TableEndpoint.AbsoluteUri, storageAccount.Credentials) 8: { 9: _storageAccount = storageAccount; 10: _entitySetName = typeof(T).Name; 11: 12: var tableStorage = new CloudTableClient(_storageAccount.TableEndpoint.AbsoluteUri, 13: _storageAccount.Credentials); 14: tableStorage.CreateTableIfNotExist(_entitySetName); 15: } 16: 17: public void Add(T entityToAdd) 18: { 19: AddObject(_entitySetName, entityToAdd); 20: SaveChanges(); 21: } 22: 23: public void Update(T entityToUpdate) 24: { 25: UpdateObject(entityToUpdate); 26: SaveChanges(); 27: } 28: 29: public void Delete(T entityToDelete) 30: { 31: DeleteObject(entityToDelete); 32: SaveChanges(); 33: } 34: 35: public IQueryable<T> Load() 36: { 37: return CreateQuery<T>(_entitySetName); 38: } 39: } I saved the name of the entity type when constructed for performance matter. The table name, entity set name would be the same as the name of the entity class. The Load method returned a generic IQueryable instance which supports the lazy load feature. Then in my service class I changed the AccountDataContext to DynamicDataContext and that's all. 1: var accountContext = new DynamicDataContext<Account>(storageAccount); Run it again and register another account. The DynamicDataContext now can be used for any entities. For example, I would like the account has a list of notes which contains 3 custom properties: Account Email, Title and Content. We create the note entity class. 1: public class Note : TableServiceEntity 2: { 3: public string AccountEmail { get; set; } 4: public string Title { get; set; } 5: public string Content { get; set; } 6: public DateTime DateCreated { get; set; } 7: public DateTime? DateDeleted { get; set; } 8: 9: public Note() 10: : base() 11: { 12: } 13: 14: public Note(string email) 15: : base(email, string.Format("{0}_{1}", email, Guid.NewGuid().ToString())) 16: { 17: AccountEmail = email; 18: } 19: } And no need to tweak the DynamicDataContext we can directly go to the service class to implement the logic. Notice here I utilized two DynamicDataContext instances with the different type parameters: Note and Account. 1: public class NoteService : INoteService 2: { 3: public void Create(string email, string title, string content) 4: { 5: var storageAccount = CloudStorageAccount.FromConfigurationSetting("DataConnectionString"); 6: var accountContext = new DynamicDataContext<Account>(storageAccount); 7: var noteContext = new DynamicDataContext<Note>(storageAccount); 8: 9: // validate - email must be existed 10: var accounts = accountContext.Load() 11: .Where(a => a.Email == email) 12: .ToList() 13: .Count; 14: if (accounts <= 0) 15: throw new ApplicationException(string.Format("The account {0} does not exsit in the system please register and try again.", email)); 16: 17: // save the note 18: var noteToAdd = new Note(email) { Title = title, Content = content, DateCreated = DateTime.Now }; 19: noteContext.Add(noteToAdd); 20: } 21: } And updated our client application to test the service. I didn't implement any list service to show all notes but we can have a look on the local SQL database if we ran it at local development fabric. Summary In this post I explained a bit about the limited LINQ support for the table service. And then I demonstrated about how to use the repository pattern in the table service data access layer and make the DataContext dynamically. The DynamicDataContext I created in this post is just a prototype. In fact we should create the relevant interface to make it testable and for better structure we'd better separate the DataContext classes for each individual kind of entity. So it should have IDataContextBase<T>, DataContextBase<T> and for each entity we would have class AccountDataContext<Account> : IDataContextBase<Account>, DataContextBase<Account> { … } class NoteDataContext<Note> : IDataContextBase<Note>, DataContextBase<Note> { … } Besides the structured data saving and loading, another common scenario would be saving and loading some binary data such as images, files. In my next post I will show how to use the Blob Service to store the bindery data - make the account be able to upload their logo in my example. Hope this helps, Shaun All documents and related graphics, codes are provided "AS IS" without warranty of any kind. Copyright © Shaun Ziyan Xu. This work is licensed under the Creative Commons License.

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Ubuntu KVM Networking

- by Guest

I have two VMs ( linux based VM ) running on a UBUNTU/QEMU KVM. I am looking at a simple networking model, where in the VMs have public address and need to talk to the outside world and the outside world should be able to talk to the VMs as well. I did this Created a bridge with A.B.C.D/16 ( class B address ) eth2 is part of the brige with A.B.C.E /32 host address VM's interface ( through TAP ) has A.B.C.F / 16 address eth2 and VM interface are both part of the bridge. Now however, I am unable to ping these address from the outside world. If i remove eth2 from the bridge, I am able to ping the eth2. Please let me know what is going on. Guest

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Unable to enumerate USB device

- by takeshin

Hello, My syslog is constantly filled with messages like this: Oct 16 11:48:35 my-laptop kernel: [61470.980078] hub 1-0:1.0: unable to enumerate USB device on port 2 Oct 16 11:48:35 my-laptop kernel: [61471.192079] hub 3-0:1.0: unable to enumerate USB device on port 2 The only USB device I use is Microsoft Natural Wireless Laser Mouse 7000. The laptop model is HP dv9500, Ubuntu 10.10, but the same was in the versions before. How can I fix this? Edit: Here's the output of sudo lsusb: Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 003 Device 003: ID 045e:071d Microsoft Corp. Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub All USB devices seems to be working fine. I have some problems with DVD-R and sound card, but they are not USB.

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Having Trouble Granting Access Via Squid

- by Muhnamana

I'm by far no expert at this but how do I grant access to Squid? I'm current using 2.7.STABLE9. I've read you need to add a couple of lines, an acl and http_access line. So here's what I added and where. I highly doubt this is right since I'm trying to connect via my laptop and Firefox is yelling at me saying the proxy server is refusing connections. ACL Part: # Example rule allowing access from your local networks. # Adapt to list your (internal) IP networks from where browsing # should be allowed **acl all_computers scr 192.168.1.0/255.255.255.0** acl localnet src 10.0.0.0/8 # RFC1918 possible internal network acl localnet src 172.16.0.0/12 # RFC1918 possible internal network acl localnet src 192.168.0.0/16 # RFC1918 possible internal network http_access part: # Example rule allowing access from your local networks. # Adapt localnet in the ACL section to list your (internal) IP networks # from where browsing should be allowed #http_access allow localnet http_access allow localhost http_access allow all_computers Any suggestions on what I'm doing wrong?

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No network connectivity (not wired or wireless) - RT5390

- by Ben Udy

I am starting to think I simply need to accept a small loss and sell my new ASUS K73E. Because I really don't enjoy computing when I have to deal with Windough$ and this windows 7 64 bit on my new ASUS is even worse than the old machines with XP. I have written to ASUS and they simply say "We don't support Linux" and while Ralink's website says they do support Linux I can't get anyone to tell me what model Ralink card might be in my machine. Is anyone out there who might be able to give me some useful advice???? Here is the answer to command lspci nn && lsusb && lsmod && rfkill list all: di,snd_seq snd 54244 16 snd_hda_codec_realtek,snd_hda_intel,snd_hda_codec,snd_hwdep,snd_pcm_oss,snd_mixer_oss,snd_pcm,snd_seq_oss,snd_rawmidi,snd_seq,snd_timer,snd_seq_device uvcvideo 57374 0 videodev 34361 1 uvcvideo v4l1_compat 13251 2 uvcvideo,videodev soundcore 6620 1 snd snd_page_alloc 7076 2 snd_hda_intel,snd_pcm psmouse 63677 0 serio_raw 3978 0 lp 7028 0 parport 32635 2 ppdev,lp fbcon 35102 71 tileblit 1999 1 fbcon font 7557 1 fbcon bitblit 4707 1 fbcon softcursor 1189 1 bitblit video 17375 0 output 1871 1 video vga16fb 11385 1 vgastate 8961 1 vga16fb ahci 32360 2 di,snd_seq snd 54244 16 snd_hda_codec_realtek,snd_hda_intel,snd_hda_codec,snd_hwdep,snd_pcm_oss,snd_mixer_oss,snd_pcm,snd_seq_oss,snd_rawmidi,snd_seq,snd_timer,snd_seq_device uvcvideo 57374 0 videodev 34361 1 uvcvideo v4l1_compat 13251 2 uvcvideo,videodev soundcore 6620 1 snd snd_page_alloc 7076 2 snd_hda_intel,snd_pcm psmouse 63677 0 serio_raw 3978 0 lp 7028 0 parport 32635 2 ppdev,lp fbcon 35102 71 tileblit 1999 1 fbcon font 7557 1 fbcon bitblit 4707 1 fbcon softcursor 1189 1 bitblit video 17375 0 output 1871 1 video vga16fb 11385 1 vgastate 8961 1 vga16fb ahci 32360 2 Edit #2 lspci 00:00.0 Host bridge: Intel Corporation Device 0104 (rev 09) 00:02.0 VGA compatible controller: Intel Corporation Device 0116 (rev 09) 00:16.0 Communication controller: Intel Corporation Cougar Point HECI Controller #1 (rev 04) 00:1a.0 USB Controller: Intel Corporation Cougar Point USB Enhanced Host Controller #2 (rev 05) 00:1b.0 Audio device: Intel Corporation Cougar Point High Definition Audio Controller (rev 05) 00:1c.0 PCI bridge: Intel Corporation Cougar Point PCI Express Root Port 1 (rev b5) 00:1c.1 PCI bridge: Intel Corporation Cougar Point PCI Express Root Port 2 (rev b5) 00:1c.5 PCI bridge: Intel Corporation Cougar Point PCI Express Root Port 6 (rev b5) 00:1d.0 USB Controller: Intel Corporation Cougar Point USB Enhanced Host Controller #1 (rev 05) 00:1f.0 ISA bridge: Intel Corporation Device 1c49 (rev 05) 00:1f.2 SATA controller: Intel Corporation Cougar Point 6 port SATA AHCI Controller (rev 05) 00:1f.3 SMBus: Intel Corporation Cougar Point SMBus Controller (rev 05) 02:00.0 Network controller: RaLink Device 5390 03:00.0 Ethernet controller: Atheros Communications Device 1083 (rev c0) lsusb Bus 002 Device 002: ID 8087:0024 Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 001 Device 003: ID 13d3:5710 IMC Networks Bus 001 Device 002: ID 8087:0024 Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Thanks for the suggestion because this gave me a model for Ralink RT5390. I have now gone to Ralink.com and downloaded (via Windows 7) the driver package (it is a bz2 file). I hope I can figure out how to install it. And FYI - I was not able to run su (not authorized?) and dmidecode didn't exist (probably needs to be downloaded BUT no internet yet in Ubuntu)

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Installing Cairo to get FastRWeb working for R gWidgetsWWW2 -pkg

- by hhh

I want to install FastRWeb for R but it requires some Cairo. How can I install the Cairo? compilation terminated. make: *** [xlib-backend.o] Error 1 ERROR: compilation failed for package ‘Cairo’ * removing ‘/home/xfz/R/i686-pc-linux-gnu-library/2.13/Cairo’ ERROR: dependency ‘Cairo’ is not available for package ‘FastRWeb’ * removing ‘/home/xfz/R/i686-pc-linux-gnu-library/2.13/FastRWeb’ The downloaded packages are in ‘/tmp/Rtmpno8hhF/downloaded_packages’ Warning messages: 1: In install.packages("FastRWeb", , "http://rforge.net/", type = "source") : installation of package 'Cairo' had non-zero exit status 2: In install.packages("FastRWeb", , "http://rforge.net/", type = "source") : installation of package 'FastRWeb' had non-zero exit status I cannot find what the Cairo is here, 16 entries with this search term below. It is apparently some library. $ apt-cache search libcairo|wc 16 132 996 Perhaps related http://stackoverflow.com/questions/9826128/r-making-r-rook-program-into-rscript-program-r http://stackoverflow.com/questions/9812547/r-gui-vizualiser-with-command-line-access-browser-based-letting-users-to-s Some related packages FastRWeb and RServe for the gWidgetsWWW2 -pkg.

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Thinkpad brightness steps error using FN+Home/End

- by petermolnar

I've met the following problem: normally my T400 (Lenovo Thinkpad) has 16 steps of brightness, and Windows utilizes it correctly. After a fresh install & minor tweaks Mint 12 (which is based on 11.10 Ubuntu) I only had 6 steps which was way to few. Listing /sys/class/backlight showed 3 entried. I removed the acpi-tools package, one of the disapperared - and I now have 10 steps! Therefore I think if I can reduce the entries to 1 I'm going to have 16 steps, since the stepping will be 1 instead of 2 (or 3). /sys/class/backlight/ intel_backlight -> ../../devices/pci0000:00/0000:00:02.0/drm/card0/card0-LVDS-1/intel_backlight thinkpad_screen -> ../../devices/virtual/backlight/thinkpad_screen The problem is that I'm unable to trace back what are the configs / daemons / kernel options triggers these two. More strangely, I discovered a strange behaviour. I monitored watch -n1 "cat /sys/class/backlight/thinkpad_screen/actual_brightness" and watch -n1 "cat /sys/class/backlight/intel_backlight/actual_brightness" while changing the brightness with FN+home/end combinations from max to min. The outcome is the following: brighness intel thinkpad --------- ----- -------- MAX 2408475 7 | 1955115 5 | 1435640 3 | 1246740 1 | 1086175 0 | 1010615 6 | 859495 4 | 689485 2 v 481695 0 MIN 217235 0 brighness intel thinkpad --------- ----- -------- MIN 217235 0 | 481695 2 | 689485 4 | 859495 6 | 1010615 7 | 1086175 1 | 1246740 3 | 1435640 5 v 1955115 7 MAX 2408475 0 When stepping from MIN to MAX, there's no difference between the last 2 steps. Also, the OSD icon (Cinnamon desktop, default theme) goes from full to min in 4 steps and from full to min once again in 4 steps. So... it seems that the intel entry is working correctly, showing correct values. The thinkpad entry however twists the things and even showing incorrect values. Does anyone have any idea how to get rid of the thinkpad entry? System data: Linux Mint 12 3.0.0-16 kernel Lenovo ThinkPad T400 Cinnamon 1.4 desktop For any additional info, please tell me what do you need. EDIT I'm sorry, I forgot to mention, I added acpi_backlight=vendor to GRUB cmdline as well, this is the result of the semi-better working than the default.

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Grub messed up on dual boot machine - can't boot live usb

- by Sam

I have a laptop on which I had Win 7 and Ubuntu 12.04 installed. The hdd has two partitions (one primary and one extended). Grub wasn't loaing initially so I ran the boot disk repair tool which seemed to sort it out. However, I mistakenly removed python (long story) from the Ubuntu OS and this obviously messed up Ubuntu a lot. So I decided to reintsall both Win7 and Ubuntu 12.04 in an attempt to get things back fresh. Win 7 went fine, but now when I try and use the Live USB to install Ubuntu I get: error: no such device: grub rescue I guess grub is still there despite the Win 7 reinstall and it can't find the partition for Ubuntu (which I deleted prior to the fresh install). I have tried fixmbr in windows console and the boot-repair-disk utility, but no joy. I cannot boot the live usb so no access to linux. A real mess. Any suggestions from the community?

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Ubuntu 11.10 crashes all browsers often

- by murat

I have been using ubuntu 11.10 for 1 year,today it made me surprised. When I open google chrome it just closes itself. Firstly i thought that it is just for chrome and tried Firefox : It also closes itself and one thing more : I tried desktop programs such as image viewer it also closes itself.I restarted it but there is no changing.What can do this ? is it virus or another system problem ? I did not have any problem like this until today.. $ google-chrome (google-chrome:7064): Gtk-WARNING **: Unable to locate theme engine in module_path: "pixmap", (google-chrome:7064): Gtk-WARNING **: Unable to locate theme engine in module_path: "pixmap", (google-chrome:7064): Gtk-WARNING **: Unable to locate theme engine in module_path: "pixmap", (google-chrome:7064): Gtk-WARNING **: Unable to locate theme engine in module_path: "pixmap", --2012-04-04 19:33:14-- https://clients2.google.com/cr/report Resolving clients2.google.com... 173.194.70.100, 173.194.70.101, 173.194.70.102, ... Connecting to clients2.google.com|173.194.70.100|:443... connected. HTTP request sent, awaiting response... 200 OK Length: unspecified [text/html] 2012-04-04 19:33:19 (888 KB/s) - `/dev/fd/3' saved [16] (exe:7166): Gtk-WARNING **: Unable to locate theme engine in module_path: "pixmap", (exe:7166): Gtk-WARNING **: Unable to locate theme engine in module_path: "pixmap", (exe:7166): Gtk-WARNING **: Unable to locate theme engine in module_path: "pixmap", (exe:7166): Gtk-WARNING **: Unable to locate theme engine in module_path: "pixmap", Moonlight: 3.99.0.3 Moonlight: Attempting to load libmoonloaderxpi (exe:7201): Gtk-WARNING **: Unable to locate theme engine in module_path: "pixmap", (exe:7201): Gtk-WARNING **: Unable to locate theme engine in module_path: "pixmap", (exe:7201): Gtk-WARNING **: Unable to locate theme engine in module_path: "pixmap", (exe:7201): Gtk-WARNING **: Unable to locate theme engine in module_path: "pixmap", Failed to open VDPAU backend libvdpau_nvidia.so: cannot open shared object file: No such file or directory Segmentation fault After trying to install libvdpau1 error is changed : google-chrome --2012-04-04 20:05:03-- https://clients2.google.com/cr/report Resolving clients2.google.com... 173.194.70.113, 173.194.70.138, 173.194.70.139, ... Connecting to clients2.google.com|173.194.70.113|:443... connected. HTTP request sent, awaiting response... Moonlight: 3.99.0.3 Moonlight: Attempting to load libmoonloaderxpi 200 OK Length: unspecified [text/html] Saving to: `/dev/fd/3' [<=> ] 0 --.-K/s f4c55117d1b4656e [ <= ] 16 --.-K/s in 0s 2012-04-04 20:05:12 (337 KB/s) - `/dev/fd/3' saved [16] Segmentation fault

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Why is chunk size often a power of two?

- by danijar

There are many Minecraft clones out there and I am working on my own implementation. A principle of terrain rendering is tiling the whole world in fixed size chunks to reduce the effort of localized changes. In Minecraft the chunk size is 16 x 16 x 256 as far as I now. And in clones I also always saw chunk sizes of a power of the number 2. Is there any reason for that, maybe performance or memory related? I know that powers of 2 play a special role in binary computers but what has that to do with the chunk size?

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CLI program to download album art

- by John Baber

I'd like to be able to do this: $ pwd /home/$USER/music/ripped_music/Monty_Python-Instant_Record_Collection $ ls 01.The_Executive_Intro.mp3 ... 16.The_Lumberjack_Song.mp3 $ mystery_command_or_script . $ ls 01.The_Executive_Intro.mp3 ... 16.The_Lumberjack_Song.mp3 album_cover.jpg $ Somewhere in the guts of Rhythmbox, totem, etc. this is being done. I'd like to be able to do it myself. I don't need help actually writing a script. I'd really just like to know if there's something like CDDB for album covers. (Scraping albumart.org is the current working solution.)

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Displaying Raw Images using WPF.

An article describing how to display 8-bit and 16-bit Raw images using WPF.

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ZFS for Database Log Files

- by user12620111

I've been troubled by drop outs in CPU usage in my application server, characterized by the CPUs suddenly going from close to 90% CPU busy to almost completely CPU idle for a few seconds. Here is an example of a drop out as shown by a snippet of vmstat data taken while the application server is under a heavy workload. # vmstat 1 kthr memory page disk faults cpu r b w swap free re mf pi po fr de sr s3 s4 s5 s6 in sy cs us sy id 1 0 0 130160176 116381952 0 16 0 0 0 0 0 0 0 0 0 207377 117715 203884 70 21 9 12 0 0 130160160 116381936 0 25 0 0 0 0 0 0 0 0 0 200413 117162 197250 70 20 9 11 0 0 130160176 116381920 0 16 0 0 0 0 0 0 1 0 0 203150 119365 200249 72 21 7 8 0 0 130160176 116377808 0 19 0 0 0 0 0 0 0 0 0 169826 96144 165194 56 17 27 0 0 0 130160176 116377800 0 16 0 0 0 0 0 0 0 0 1 10245 9376 9164 2 1 97 0 0 0 130160176 116377792 0 16 0 0 0 0 0 0 0 0 2 15742 12401 14784 4 1 95 0 0 0 130160176 116377776 2 16 0 0 0 0 0 0 1 0 0 19972 17703 19612 6 2 92 14 0 0 130160176 116377696 0 16 0 0 0 0 0 0 0 0 0 202794 116793 199807 71 21 8 9 0 0 130160160 116373584 0 30 0 0 0 0 0 0 18 0 0 203123 117857 198825 69 20 11 This behavior occurred consistently while the application server was processing synthetic transactions: HTTP requests from JMeter running on an external machine. I explored many theories trying to explain the drop outs, including: Unexpected JMeter behavior Network contention Java Garbage Collection Application Server thread pool problems Connection pool problems Database transaction processing Database I/O contention Graphing the CPU %idle led to a breakthrough: Several of the drop outs were 30 seconds apart. With that insight, I went digging through the data again and looking for other outliers that were 30 seconds apart. In the database server statistics, I found spikes in the iostat "asvc_t" (average response time of disk transactions, in milliseconds) for the disk drive that was being used for the database log files. Here is an example: extended device statistics r/s w/s kr/s kw/s wait actv wsvc_t asvc_t %w %b device 0.0 2053.6 0.0 8234.3 0.0 0.2 0.0 0.1 0 24 c3t60080E5...F4F6d0s0 0.0 2162.2 0.0 8652.8 0.0 0.3 0.0 0.1 0 28 c3t60080E5...F4F6d0s0 0.0 1102.5 0.0 10012.8 0.0 4.5 0.0 4.1 0 69 c3t60080E5...F4F6d0s0 0.0 74.0 0.0 7920.6 0.0 10.0 0.0 135.1 0 100 c3t60080E5...F4F6d0s0 0.0 568.7 0.0 6674.0 0.0 6.4 0.0 11.2 0 90 c3t60080E5...F4F6d0s0 0.0 1358.0 0.0 5456.0 0.0 0.6 0.0 0.4 0 55 c3t60080E5...F4F6d0s0 0.0 1314.3 0.0 5285.2 0.0 0.7 0.0 0.5 0 70 c3t60080E5...F4F6d0s0 Here is a little more information about my database configuration: The database and application server were running on two different SPARC servers. Storage for the database was on a storage array connected via 8 gigabit Fibre Channel Data storage and log file were on different physical disk drives Reliable low latency I/O is provided by battery backed NVRAM Highly available: Two Fibre Channel links accessed via MPxIO Two Mirrored cache controllers The log file physical disks were mirrored in the storage device Database log files on a ZFS Filesystem with cutting-edge technologies, such as copy-on-write and end-to-end checksumming Why would I be getting service time spikes in my high-end storage? First, I wanted to verify that the database log disk service time spikes aligned with the application server CPU drop outs, and they did: At first, I guessed that the disk service time spikes might be related to flushing the write through cache on the storage device, but I was unable to validate that theory. After searching the WWW for a while, I decided to try using a separate log device: # zpool add ZFS-db-41 log c3t60080E500017D55C000015C150A9F8A7d0 The ZFS log device is configured in a similar manner as described above: two physical disks mirrored in the storage array. This change to the database storage configuration eliminated the application server CPU drop outs: Here is the zpool configuration: # zpool status ZFS-db-41 pool: ZFS-db-41 state: ONLINE scan: none requested config: NAME STATE ZFS-db-41 ONLINE c3t60080E5...F4F6d0 ONLINE logs c3t60080E5...F8A7d0 ONLINE Now, the I/O spikes look like this: extended device statistics r/s w/s kr/s kw/s wait actv wsvc_t asvc_t %w %b device 0.0 1053.5 0.0 4234.1 0.0 0.8 0.0 0.7 0 75 c3t60080E5...F8A7d0s0 extended device statistics r/s w/s kr/s kw/s wait actv wsvc_t asvc_t %w %b device 0.0 1131.8 0.0 4555.3 0.0 0.8 0.0 0.7 0 76 c3t60080E5...F8A7d0s0 extended device statistics r/s w/s kr/s kw/s wait actv wsvc_t asvc_t %w %b device 0.0 1167.6 0.0 4682.2 0.0 0.7 0.0 0.6 0 74 c3t60080E5...F8A7d0s0 0.0 162.2 0.0 19153.9 0.0 0.7 0.0 4.2 0 12 c3t60080E5...F4F6d0s0 extended device statistics r/s w/s kr/s kw/s wait actv wsvc_t asvc_t %w %b device 0.0 1247.2 0.0 4992.6 0.0 0.7 0.0 0.6 0 71 c3t60080E5...F8A7d0s0 0.0 41.0 0.0 70.0 0.0 0.1 0.0 1.6 0 2 c3t60080E5...F4F6d0s0 extended device statistics r/s w/s kr/s kw/s wait actv wsvc_t asvc_t %w %b device 0.0 1241.3 0.0 4989.3 0.0 0.8 0.0 0.6 0 75 c3t60080E5...F8A7d0s0 extended device statistics r/s w/s kr/s kw/s wait actv wsvc_t asvc_t %w %b device 0.0 1193.2 0.0 4772.9 0.0 0.7 0.0 0.6 0 71 c3t60080E5...F8A7d0s0 We can see the steady flow of 4k writes to the ZIL device from O_SYNC database log file writes. The spikes are from flushing the transaction group. Like almost all problems that I run into, once I thoroughly understand the problem, I find that other people have documented similar experiences. Thanks to all of you who have documented alternative approaches. Saved for another day: now that the problem is obvious, I should try "zfs:zfs_immediate_write_sz" as recommended in the ZFS Evil Tuning Guide. References: The ZFS Intent Log Solaris ZFS, Synchronous Writes and the ZIL Explained ZFS Evil Tuning Guide: Cache Flushes ZFS Evil Tuning Guide: Tuning ZFS for Database Performance

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How do I know if my serial adapter card is working?

- by Ingram

I just installed a 2 port serial adapter in my Ubuntu 10.10 system, then I tried following this tutorial that I used on my old system to connect to a cisco router (my old system had an onboard serial adapter, and the tutorial worked just fine). I can't get my system to connect to the cisco router, so I'm wondering if the card even works in Ubuntu. How can I tell if the card actually works with Ubuntu? #dmesg | grep tty [ 0.000000] console [tty0] enabled [ 0.358667] serial8250: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A [ 0.358994] 00:0c: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A [ 0.359128] ttyS1: detected caps 00000700 should be 00000100 [ 0.359132] 0000:03:00.0: ttyS1 at MMIO 0xfeafd000 (irq = 16) is a 16C950/954 [ 0.359191] ttyS2: detected caps 00000700 should be 00000100 [ 0.359195] 0000:03:00.0: ttyS2 at MMIO 0xfeafd200 (irq = 16) is a 16C950/954

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Why the overhead when allocating objects/arrays in Java?

- by Gnijuohz

How many bytes an array occupies in Java? Assume It's a 64bit machine and also assume there are N elements in an array, so all these elements would take up 2*N, 4*N or 8*N bytes for different types of array. And a lecture in Coursera says that it would occupy 2*N+24, 4*N+24 or 8*N+24 bytes for a N element array and the 24 bytes is called overhead, but didn't explain why the overhead is needed. Also objects have overheads, which is 16 bytes. What exactly are these overheads? What are these 24/16 bytes composed of? Also, do these overheads only exist in Java? How about C, C++ and Python?

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Configurable tables in sql database

- by dot

I have the following tables in my database: Config Table: ====================================== Start_Range | End Range | Config_id 10 | 15 | 1 ====================================== Available_UserIDs ========================== ID | UserID | Used_YN | 1 | 10 | t | 1 | 11 | f | 1 | 12 | f | 1 | 13 | f | 1 | 14 | f | 1 | 15 | f | ========================== Users ========================== UserId | FName | LName | 10 |John | Doe | ========================== This is used in a reservation system of sorts... which lets an administrator specify a range of numbers that will be assigned to users in the config table. Once the range has been defined, the system then populates the Available_userIDs table with all the numbers in between the range, and sets the Used_YN flag to false As users sign up, they grab the next user_id number that's not in use... and reserve it. Then the system adds a record to the Users table. Once the admin has specified a range, it is possible that they can change it. For example, they can start with 10-15... and then when the range is used up, they should be able to specify another range like 16 - 99. I've put a unique constraint on the Available_UserIDs table, as well as on the Users table - to ensure that UserIds can't be duplicated. My questions are as follows: What's the best way to prevent the admins from using a range that's already in use? I thought of the following options: -- check either the Users table to see if the start range or ending range numbers are being used. If they are, assume that all the numbers in between are in use too, and reject the range. -- let them specify whatever they want, try to populate the Available_UserIDs table. If there are duplicates, just ignore that specific error message from the database and continue on. How do I find gaps in the number ranges? For example, if they specify 10-15, and then 20-25, it'd be nice to be able to somehow suggest on my web page that 16-19 is currently available. I found this article: http://stackoverflow.com/questions/1312101/how-to-find-a-gap-in-running-counter-with-sql But it only seems to return the first available number... so in my example above, it would only return the number 16. I'm sure there's a simpler way to do things that I'm overlooking!

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algorithm for project euler problem no 18

- by Valentino Ru

Problem number 18 from Project Euler's site is as follows: By starting at the top of the triangle below and moving to adjacent numbers on the row below, the maximum total from top to bottom is 23. 3 7 4 2 4 6 8 5 9 3 That is, 3 + 7 + 4 + 9 = 23. Find the maximum total from top to bottom of the triangle below: 75 95 64 17 47 82 18 35 87 10 20 04 82 47 65 19 01 23 75 03 34 88 02 77 73 07 63 67 99 65 04 28 06 16 70 92 41 41 26 56 83 40 80 70 33 41 48 72 33 47 32 37 16 94 29 53 71 44 65 25 43 91 52 97 51 14 70 11 33 28 77 73 17 78 39 68 17 57 91 71 52 38 17 14 91 43 58 50 27 29 48 63 66 04 68 89 53 67 30 73 16 69 87 40 31 04 62 98 27 23 09 70 98 73 93 38 53 60 04 23 NOTE: As there are only 16384 routes, it is possible to solve this problem by trying every route. However, Problem 67, is the same challenge with a triangle containing one-hundred rows; it cannot be solved by brute force, and requires a clever method! ;o) The formulation of this problems does not make clear if the "Traversor" is greedy, meaning that he always choosed the child with be higher value the maximum of every single walkthrough is asked The NOTE says, that it is possible to solve this problem by trying every route. This means to me, that is is also possible without! This leads to my actual question: Assumed that not the greedy one is the max, is there any algorithm that finds the max walkthrough value without trying every route and that doesn't act like the greedy algorithm? I implemented an algorithm in Java, putting the values first in a node structure, then applying the greedy algorithm. The result, however, is cosidered as wrong by Project Euler. sum = 0; void findWay(Node node){ sum += node.value; if(node.nodeLeft != null && node.nodeRight != null){ if(node.nodeLeft.value > node.nodeRight.value){ findWay(node.nodeLeft); }else{ findWay(node.nodeRight); } } }

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