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  • What is the coolest thing you can do in <10 lines of simple code? Help me inspire beginners!

    - by Tom Ritter
    I'm looking for the coolest thing you can do in a few lines of simple code. I'm sure you can write a Mandelbrot set in Haskell in 15 lines but it's difficult to follow. My goal is to inspire students that programming is cool. We know that programming is cool because you can create anything you imagine - it's the ultimate creative outlet. I want to inspire these beginners and get them over as many early-learning humps as I can. Now, my reasons are selfish. I'm teaching an Intro to Computing course to a group of 60 half-engineering, half business majors; all freshmen. They are the students who came from underprivileged High schools. From my past experience, the group is generally split as follows: a few rock-stars, some who try very hard and kind of get it, the few who try very hard and barely get it, and the few who don't care. I want to reach as many of these groups as effectively as I can. Here's an example of how I'd use a computer program to teach: Here's an example of what I'm looking for: a 1-line VBS script to get your computer to talk to you: CreateObject("sapi.spvoice").Speak InputBox("Enter your text","Talk it") I could use this to demonstrate order of operations. I'd show the code, let them play with it, then explain that There's a lot going on in that line, but the computer can make sense of it, because it knows the rules. Then I'd show them something like this: 4(5*5) / 10 + 9(.25 + .75) And you can see that first I need to do is (5*5). Then I can multiply for 4. And now I've created the Object. Dividing by 10 is the same as calling Speak - I can't Speak before I have an object, and I can't divide before I have 100. Then on the other side I first create an InputBox with some instructions for how to display it. When I hit enter on the input box it evaluates or "returns" whatever I entered. (Hint: 'oooooo' makes a funny sound) So when I say Speak, the right side is what to Speak. And I get that from the InputBox. So when you do several things on a line, like: x = 14 + y; You need to be aware of the order of things. First we add 14 and y. Then we put the result (what it evaluates to, or returns) into x. That's my goal, to have a bunch of these cool examples to demonstrate and teach the class while they have fun. I tried this example on my roommate and while I may not use this as the first lesson, she liked it and learned something. Some cool mathematica programs that make beautiful graphs or shapes that are easy to understand would be good ideas and I'm going to look into those. Here are some complicated actionscript examples but that's a bit too advanced and I can't teach flash. What other ideas do you have?

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  • Proper network configuration for a KVM guest to be on the same networks at the host

    - by Steve Madsen
    I am running a Debian Linux server on Lenny. Within it, I am running another Lenny instance using KVM. Both servers are externally available, with public IPs, as well as a second interface with private IPs for the LAN. Everything works fine, except the VM sees all network traffic as originating from the host server. I suspect this might have something to do with the iptables-based firewall I'm running on the host. What I'd like to figure out is: how to I properly configure the host's networking such that all of these requirements are met? Both host and VMs have 2 network interfaces (public and private). Both host and VMs can be independently firewalled. Ideally, VM traffic does not have to traverse the host firewall. VMs see real remote IP addresses, not the host's. Currently, the host's network interfaces are configured as bridges. eth0 and eth1 do not have IP addresses assigned to them, but br0 and br1 do. /etc/network/interfaces on the host: # The primary network interface auto br1 iface br1 inet static address 24.123.138.34 netmask 255.255.255.248 network 24.123.138.32 broadcast 24.123.138.39 gateway 24.123.138.33 bridge_ports eth1 bridge_stp off auto br1:0 iface br1:0 inet static address 24.123.138.36 netmask 255.255.255.248 network 24.123.138.32 broadcast 24.123.138.39 # Internal network auto br0 iface br0 inet static address 192.168.1.1 netmask 255.255.255.0 network 192.168.1.0 broadcast 192.168.1.255 bridge_ports eth0 bridge_stp off This is the libvirt/qemu configuration file for the VM: <domain type='kvm'> <name>apps</name> <uuid>636b6620-0949-bc88-3197-37153b88772e</uuid> <memory>393216</memory> <currentMemory>393216</currentMemory> <vcpu>1</vcpu> <os> <type arch='i686' machine='pc'>hvm</type> <boot dev='hd'/> </os> <features> <acpi/> <apic/> <pae/> </features> <clock offset='utc'/> <on_poweroff>destroy</on_poweroff> <on_reboot>restart</on_reboot> <on_crash>restart</on_crash> <devices> <emulator>/usr/bin/kvm</emulator> <disk type='file' device='cdrom'> <target dev='hdc' bus='ide'/> <readonly/> </disk> <disk type='file' device='disk'> <source file='/raid/kvm-images/apps.qcow2'/> <target dev='vda' bus='virtio'/> </disk> <interface type='bridge'> <mac address='54:52:00:27:5e:02'/> <source bridge='br0'/> <model type='virtio'/> </interface> <interface type='bridge'> <mac address='54:52:00:40:cc:7f'/> <source bridge='br1'/> <model type='virtio'/> </interface> <serial type='pty'> <target port='0'/> </serial> <console type='pty'> <target port='0'/> </console> <input type='mouse' bus='ps2'/> <graphics type='vnc' port='-1' autoport='yes' keymap='en-us'/> </devices> </domain> Along with the rest of my firewall rules, the firewalling script includes this command to pass packets destined for a KVM guest: # Allow bridged packets to pass (for KVM guests). iptables -A FORWARD -m physdev --physdev-is-bridged -j ACCEPT (Not applicable to this question, but a side-effect of my bridging configuration appears to be that I can't ever shut down cleanly. The kernel eventually tells me "unregister_netdevice: waiting for br1 to become free" and I have to hard reset the system. Maybe a sign I've done something dumb?)

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  • Database - Designing an "Events" Table

    - by Alix Axel
    After reading the tips from this great Nettuts+ article I've come up with a table schema that would separate highly volatile data from other tables subjected to heavy reads and at the same time lower the number of tables needed in the whole database schema, however I'm not sure if this is a good idea since it doesn't follow the rules of normalization and I would like to hear your advice, here is the general idea: I've four types of users modeled in a Class Table Inheritance structure, in the main "user" table I store data common to all the users (id, username, password, several flags, ...) along with some TIMESTAMP fields (date_created, date_updated, date_activated, date_lastLogin, ...). To quote the tip #16 from the Nettuts+ article mentioned above: Example 2: You have a “last_login” field in your table. It updates every time a user logs in to the website. But every update on a table causes the query cache for that table to be flushed. You can put that field into another table to keep updates to your users table to a minimum. Now it gets even trickier, I need to keep track of some user statistics like how many unique times a user profile was seen how many unique times a ad from a specific type of user was clicked how many unique times a post from a specific type of user was seen and so on... In my fully normalized database this adds up to about 8 to 10 additional tables, it's not a lot but I would like to keep things simple if I could, so I've come up with the following "events" table: |------|----------------|----------------|--------------|-----------| | ID | TABLE | EVENT | DATE | IP | |------|----------------|----------------|--------------|-----------| | 1 | user | login | 201004190030 | 127.0.0.1 | |------|----------------|----------------|--------------|-----------| | 1 | user | login | 201004190230 | 127.0.0.1 | |------|----------------|----------------|--------------|-----------| | 2 | user | created | 201004190031 | 127.0.0.2 | |------|----------------|----------------|--------------|-----------| | 2 | user | activated | 201004190234 | 127.0.0.2 | |------|----------------|----------------|--------------|-----------| | 2 | user | approved | 201004190930 | 217.0.0.1 | |------|----------------|----------------|--------------|-----------| | 2 | user | login | 201004191200 | 127.0.0.2 | |------|----------------|----------------|--------------|-----------| | 15 | user_ads | created | 201004191230 | 127.0.0.1 | |------|----------------|----------------|--------------|-----------| | 15 | user_ads | impressed | 201004191231 | 127.0.0.2 | |------|----------------|----------------|--------------|-----------| | 15 | user_ads | clicked | 201004191231 | 127.0.0.2 | |------|----------------|----------------|--------------|-----------| | 15 | user_ads | clicked | 201004191231 | 127.0.0.2 | |------|----------------|----------------|--------------|-----------| | 15 | user_ads | clicked | 201004191231 | 127.0.0.2 | |------|----------------|----------------|--------------|-----------| | 15 | user_ads | clicked | 201004191231 | 127.0.0.2 | |------|----------------|----------------|--------------|-----------| | 15 | user_ads | clicked | 201004191231 | 127.0.0.2 | |------|----------------|----------------|--------------|-----------| | 2 | user | blocked | 201004200319 | 217.0.0.1 | |------|----------------|----------------|--------------|-----------| | 2 | user | deleted | 201004200320 | 217.0.0.1 | |------|----------------|----------------|--------------|-----------| Basically the ID refers to the primary key (id) field in the TABLE table, I believe the rest should be pretty straightforward. One thing that I've come to like in this design is that I can keep track of all the user logins instead of just the last one, and thus generate some interesting metrics with that data. Due to the nature of the events table I also thought of making some optimizations, such as: #9: Since there is only a finite number of tables and a finite (and predetermined) number of events, the TABLE and EVENTS columns could be setup as ENUMs instead of VARCHARs to save some space. #14: Store IPs as UNSIGNED INT with INET_ATON() instead of VARCHARs. Store DATEs as TIMESTAMPs instead of DATETIMEs. Use the ARCHIVE (or the CSV?) engine instead of InnoDB / MyISAM. Overall, each event would only consume 14 bytes which is okay for my traffic I guess. Pros: Ability to store more detailed data (such as logins). No need to design (and code for) almost a dozen additional tables (dates and statistics). Reduces a few columns per table and keeps volatile data separated. Cons: Non-relational (still not as bad as EAV): SELECT * FROM events WHERE id = 2 AND table = 'user' ORDER BY date DESC(); 6 bytes overhead per event (ID, TABLE and EVENT). I'm more inclined to go with this approach since the pros seem to far outweigh the cons, but I'm still a little bit reluctant.. Am I missing something? What are your thoughts on this? Thanks!

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  • puppet master REST API returns 403 when running under passenger works when master runs from command line

    - by Anadi Misra
    I am using the standard auth.conf provided in puppet install for the puppet master which is running through passenger under Nginx. However for most of the catalog, files and certitifcate request I get a 403 response. ### Authenticated paths - these apply only when the client ### has a valid certificate and is thus authenticated # allow nodes to retrieve their own catalog path ~ ^/catalog/([^/]+)$ method find allow $1 # allow nodes to retrieve their own node definition path ~ ^/node/([^/]+)$ method find allow $1 # allow all nodes to access the certificates services path ~ ^/certificate_revocation_list/ca method find allow * # allow all nodes to store their reports path /report method save allow * # unconditionally allow access to all file services # which means in practice that fileserver.conf will # still be used path /file allow * ### Unauthenticated ACL, for clients for which the current master doesn't ### have a valid certificate; we allow authenticated users, too, because ### there isn't a great harm in letting that request through. # allow access to the master CA path /certificate/ca auth any method find allow * path /certificate/ auth any method find allow * path /certificate_request auth any method find, save allow * path /facts auth any method find, search allow * # this one is not stricly necessary, but it has the merit # of showing the default policy, which is deny everything else path / auth any Puppet master however does not seems to be following this as I get this error on client [amisr1@blramisr195602 ~]$ sudo puppet agent --no-daemonize --verbose --server bangvmpllda02.XXXXX.com [sudo] password for amisr1: Starting Puppet client version 3.0.1 Warning: Unable to fetch my node definition, but the agent run will continue: Warning: Error 403 on SERVER: Forbidden request: XX.XXX.XX.XX(XX.XXX.XX.XX) access to /certificate_revocation_list/ca [find] at :110 Info: Retrieving plugin Error: /File[/var/lib/puppet/lib]: Failed to generate additional resources using 'eval_generate: Error 403 on SERVER: Forbidden request: XX.XXX.XX.XX(XX.XXX.XX.XX) access to /file_metadata/plugins [search] at :110 Error: /File[/var/lib/puppet/lib]: Could not evaluate: Error 403 on SERVER: Forbidden request: XX.XXX.XX.XX(XX.XXX.XX.XX) access to /file_metadata/plugins [find] at :110 Could not retrieve file metadata for puppet://devops.XXXXX.com/plugins: Error 403 on SERVER: Forbidden request: XX.XXX.XX.XX(XX.XXX.XX.XX) access to /file_metadata/plugins [find] at :110 Error: Could not retrieve catalog from remote server: Error 403 on SERVER: Forbidden request: XX.XXX.XX.XX(XX.XXX.XX.XX) access to /catalog/blramisr195602.XXXXX.com [find] at :110 Using cached catalog Error: Could not retrieve catalog; skipping run Error: Could not send report: Error 403 on SERVER: Forbidden request: XX.XXX.XX.XX(XX.XXX.XX.XX) access to /report/blramisr195602.XXXXX.com [save] at :110 and the server logs show XX.XXX.XX.XX - - [10/Dec/2012:14:46:52 +0530] "GET /production/certificate_revocation_list/ca? HTTP/1.1" 403 102 "-" "Ruby" XX.XXX.XX.XX - - [10/Dec/2012:14:46:52 +0530] "GET /production/file_metadatas/plugins?links=manage&recurse=true&&ignore=---+%0A++-+%22.svn%22%0A++-+CVS%0A++-+%22.git%22&checksum_type=md5 HTTP/1.1" 403 95 "-" "Ruby" XX.XXX.XX.XX - - [10/Dec/2012:14:46:52 +0530] "GET /production/file_metadata/plugins? HTTP/1.1" 403 93 "-" "Ruby" XX.XXX.XX.XX - - [10/Dec/2012:14:46:53 +0530] "POST /production/catalog/blramisr195602.XXXXX.com HTTP/1.1" 403 106 "-" "Ruby" XX.XXX.XX.XX - - [10/Dec/2012:14:46:53 +0530] "PUT /production/report/blramisr195602.XXXXX.com HTTP/1.1" 403 105 "-" "Ruby" thefile server conf file is as follows (and goin by what they say on puppet site, It is better to regulate access in auth.conf for reaching file server and then allow file server to server all) [files] path /apps/puppet/files allow * [private] path /apps/puppet/private/%H allow * [modules] allow * I am using server and client version 3 Nginx has been compiled using the following options nginx version: nginx/1.3.9 built by gcc 4.4.6 20120305 (Red Hat 4.4.6-4) (GCC) TLS SNI support enabled configure arguments: --prefix=/apps/nginx --conf-path=/apps/nginx/nginx.conf --pid-path=/apps/nginx/run/nginx.pid --error-log-path=/apps/nginx/logs/error.log --http-log-path=/apps/nginx/logs/access.log --with-http_ssl_module --with-http_gzip_static_module --add-module=/usr/lib/ruby/gems/1.8/gems/passenger-3.0.18/ext/nginx --add-module=/apps/Downloads/nginx/nginx-auth-ldap-master/ and the standard nginx puppet master conf server { ssl on; listen 8140 ssl; server_name _; passenger_enabled on; passenger_set_cgi_param HTTP_X_CLIENT_DN $ssl_client_s_dn; passenger_set_cgi_param HTTP_X_CLIENT_VERIFY $ssl_client_verify; passenger_min_instances 5; access_log logs/puppet_access.log; error_log logs/puppet_error.log; root /apps/nginx/html/rack/public; ssl_certificate /var/lib/puppet/ssl/certs/bangvmpllda02.XXXXXX.com.pem; ssl_certificate_key /var/lib/puppet/ssl/private_keys/bangvmpllda02.XXXXXX.com.pem; ssl_crl /var/lib/puppet/ssl/ca/ca_crl.pem; ssl_client_certificate /var/lib/puppet/ssl/certs/ca.pem; ssl_ciphers SSLv2:-LOW:-EXPORT:RC4+RSA; ssl_prefer_server_ciphers on; ssl_verify_client optional; ssl_verify_depth 1; ssl_session_cache shared:SSL:128m; ssl_session_timeout 5m; } Puppet is picking up the correct settings from the files mentioned because config print command points to /etc/puppet [amisr1@bangvmpllDA02 puppet]$ sudo puppet config print | grep conf async_storeconfigs = false authconfig = /etc/puppet/namespaceauth.conf autosign = /etc/puppet/autosign.conf catalog_cache_terminus = store_configs confdir = /etc/puppet config = /etc/puppet/puppet.conf config_file_name = puppet.conf config_version = "" configprint = all configtimeout = 120 dblocation = /var/lib/puppet/state/clientconfigs.sqlite3 deviceconfig = /etc/puppet/device.conf fileserverconfig = /etc/puppet/fileserver.conf genconfig = false hiera_config = /etc/puppet/hiera.yaml localconfig = /var/lib/puppet/state/localconfig name = config rest_authconfig = /etc/puppet/auth.conf storeconfigs = true storeconfigs_backend = puppetdb tagmap = /etc/puppet/tagmail.conf thin_storeconfigs = false I checked the firewall rules on this VM; 80, 443, 8140, 3000 are allowed. Do I still have to tweak any specifics to auth.conf for getting this to work?

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  • How to implement an offline reader writer lock

    - by Peter Morris
    Some context for the question All objects in this question are persistent. All requests will be from a Silverlight client talking to an app server via a binary protocol (Hessian) and not WCF. Each user will have a session key (not an ASP.NET session) which will be a string, integer, or GUID (undecided so far). Some objects might take a long time to edit (30 or more minutes) so we have decided to use pessimistic offline locking. Pessimistic because having to reconcile conflicts would be far too annoying for users, offline because the client is not permanently connected to the server. Rather than storing session/object locking information in the object itself I have decided that any aggregate root that may have its instances locked should implement an interface ILockable public interface ILockable { Guid LockID { get; } } This LockID will be the identity of a "Lock" object which holds the information of which session is locking it. Now, if this were simple pessimistic locking I'd be able to achieve this very simply (using an incrementing version number on Lock to identify update conflicts), but what I actually need is ReaderWriter pessimistic offline locking. The reason is that some parts of the application will perform actions that read these complex structures. These include things like Reading a single structure to clone it. Reading multiple structures in order to create a binary file to "publish" the data to an external source. Read locks will be held for a very short period of time, typically less than a second, although in some circumstances they could be held for about 5 seconds at a guess. Write locks will mostly be held for a long time as they are mostly held by humans. There is a high probability of two users trying to edit the same aggregate at the same time, and a high probability of many users needing to temporarily read-lock at the same time too. I'm looking for suggestions as to how I might implement this. One additional point to make is that if I want to place a write lock and there are some read locks, I would like to "queue" the write lock so that no new read locks are placed. If the read locks are removed withing X seconds then the write lock is obtained, if not then the write lock backs off; no new read-locks would be placed while a write lock is queued. So far I have this idea The Lock object will have a version number (int) so I can detect multi-update conflicts, reload, try again. It will have a string[] for read locks A string to hold the session ID that has a write lock A string to hold the queued write lock Possibly a recursion counter to allow the same session to lock multiple times (for both read and write locks), but not sure about this yet. Rules: Can't place a read lock if there is a write lock or queued write lock. Can't place a write lock if there is a write lock or queued write lock. If there are no locks at all then a write lock may be placed. If there are read locks then a write lock will be queued instead of a full write lock placed. (If after X time the read locks are not gone the lock backs off, otherwise it is upgraded). Can't queue a write lock for a session that has a read lock. Can anyone see any problems? Suggest alternatives? Anything? I'd appreciate feedback before deciding on what approach to take.

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  • How do I configure OpenVPN for accessing the internet with one NIC?

    - by Lekensteyn
    I've been trying to get OpenVPN to work for three days. After reading many questions, the HOWTO, the FAQ and even parts of a guide to Linux networking, I cannot get my an Internet connection to the Internet. I'm trying to set up a OpenVPN server on a VPS, which will be used for: secure access to the Internet bypassing port restrictions (directadmin/2222 for example) an IPv6 connection (my client does only have IPv4 connectivity, while the VPS has both IPv4 and native IPv6 connectivity) (if possible) I can connect to my server and access the machine (HTTP), but Internet connectivity fails completely. I'm using ping 8.8.8.8 for testing whether my connection works or not. Using tcpdump and iptables -t nat -A POSTROUTING -j LOG, I can confirm that the packets reach my server. If I ping to 8.8.8.8 on the VPS, I get an echo-reply from 8.8.8.8 as expected. When pinging from the client, I do not get an echo-reply. The VPS has only one NIC: etho. It runs on Xen. Summary: I want to have a secure connection between my laptop and the Internet using OpenVPN. If that works, I want to have IPv6 connectivity as well. Network setup and software: Home laptop (eth0: 192.168.2.10) (tap0: 10.8.0.2) | | (running Kubuntu 10.10; OpenVPN 2.1.0-3ubuntu1) | wifi | router/gateway (gateway 192.168.2.1) | INTERNET | VPS (eth0:1.2.3.4) (gateway, tap0: 10.8.0.1) (running Debian 6; OpenVPN 2.1.3-2) wifi and my home router should not cause problems since all traffic goes encrypted over UDP port 1194. I've turned IP forwarding on: # echo 1 > /proc/sys/net/ipv4/ip_forward iptables has been configured to allow forwarding traffic as well: iptables -F FORWARD iptables -A FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT iptables -A FORWARD -s 10.8.0.0/24 -j ACCEPT iptables -A FORWARD -j DROP I've tried each of these rules separately without luck (flushing the chains before executing): iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -o eth0 -j SNAT --to 1.2.3.4 iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -o eth0 -j MASQUERADE route -n before (server): 1.2.3.4 0.0.0.0 255.255.255.0 U 0 0 0 eth0 0.0.0.0 1.2.3.4 0.0.0.0 UG 0 0 0 eth0 route -n after (server): 1.2.3.4 0.0.0.0 255.255.255.0 U 0 0 0 eth0 10.8.0.0 0.0.0.0 255.255.255.0 U 0 0 0 tap0 0.0.0.0 1.2.3.4 0.0.0.0 UG 0 0 0 eth0 route -n before (client): 192.168.2.0 0.0.0.0 255.255.255.0 U 2 0 0 wlan0 169.254.0.0 0.0.0.0 255.255.0.0 U 1000 0 0 wlan0 0.0.0.0 192.168.2.1 0.0.0.0 UG 0 0 0 wlan0 route -n after (client): 1.2.3.4 192.168.2.1 255.255.255.255 UGH 0 0 0 wlan0 10.8.0.0 0.0.0.0 255.255.255.0 U 0 0 0 tap0 192.168.2.0 0.0.0.0 255.255.255.0 U 2 0 0 wlan0 169.254.0.0 0.0.0.0 255.255.0.0 U 1000 0 0 wlan0 0.0.0.0 10.8.0.1 128.0.0.0 UG 0 0 0 tap0 128.0.0.0 10.8.0.1 128.0.0.0 UG 0 0 0 tap0 0.0.0.0 192.168.2.1 0.0.0.0 UG 0 0 0 wlan0 SERVER config proto udp dev tap ca ca.crt cert server.crt key server.key dh dh1024.pem server 10.8.0.0 255.255.255.0 push "redirect-gateway def1" ifconfig-pool-persist ipp.txt keepalive 10 120 tls-auth ta.key 0 comp-lzo user nobody group nobody persist-key persist-tun log-append openvpn-log verb 3 mute 10 CLIENT config dev tap proto udp remote 1.2.3.4 1194 resolv-retry infinite nobind persist-key persist-tun ca ca.crt cert client.crt key client.key ns-cert-type server tls-auth ta.key 1 comp-lzo verb 3 mute 20 traceroute 8.8.8.8 works as expected (similar output without OpenVPN activated): 1 10.8.0.1 (10.8.0.1) 24.276 ms 26.891 ms 29.454 ms 2 gw03.sbp.directvps.nl (178.21.112.1) 31.161 ms 31.890 ms 34.458 ms 3 ge0-v0652.cr0.nik-ams.nl.as8312.net (195.210.57.105) 35.353 ms 36.874 ms 38.403 ms 4 ge0-v3900.cr0.nik-ams.nl.as8312.net (195.210.57.53) 41.311 ms 41.561 ms 43.006 ms 5 * * * 6 209.85.248.88 (209.85.248.88) 147.061 ms 36.931 ms 28.063 ms 7 216.239.49.36 (216.239.49.36) 31.109 ms 33.292 ms 216.239.49.28 (216.239.49.28) 64.723 ms 8 209.85.255.130 (209.85.255.130) 49.350 ms 209.85.255.126 (209.85.255.126) 49.619 ms 209.85.255.122 (209.85.255.122) 52.416 ms 9 google-public-dns-a.google.com (8.8.8.8) 41.266 ms 44.054 ms 44.730 ms If you have any suggestions, please comment or answer. Thanks in advance.

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  • Find optimal strategy and AI for the game 'Proximity'?

    - by smci
    'Proximity' is a strategy game of territorial domination similar to Othello, Go and Risk. Two players, uses a 10x12 hex grid. Game invented by Brian Cable in 2007. Seems to be a worthy game for discussing a) optimal algorithm then b) how to build an AI. Strategies are going to be probabilistic or heuristic-based, due to the randomness factor, and the insane branching factor (20^120). So it will be kind of hard to compare objectively. A compute time limit of 5s per turn seems reasonable. Game: Flash version here and many copies elsewhere on the web Rules: here Object: to have control of the most armies after all tiles have been placed. Each turn you received a randomly numbered tile (value between 1 and 20 armies) to place on any vacant board space. If this tile is adjacent to any ally tiles, it will strengthen each tile's defenses +1 (up to a max value of 20). If it is adjacent to any enemy tiles, it will take control over them if its number is higher than the number on the enemy tile. Thoughts on strategy: Here are some initial thoughts; setting the computer AI to Expert will probably teach a lot: minimizing your perimeter seems to be a good strategy, to prevent flips and minimize worst-case damage like in Go, leaving holes inside your formation is lethal, only more so with the hex grid because you can lose armies on up to 6 squares in one move low-numbered tiles are a liability, so place them away from your main territory, near the board edges and scattered. You can also use low-numbered tiles to plug holes in your formation, or make small gains along the perimeter which the opponent will not tend to bother attacking. a triangle formation of three pieces is strong since they mutually reinforce, and also reduce the perimeter Each tile can be flipped at most 6 times, i.e. when its neighbor tiles are occupied. Control of a formation can flow back and forth. Sometimes you lose part of a formation and plug any holes to render that part of the board 'dead' and lock in your territory/ prevent further losses. Low-numbered tiles are obvious-but-low-valued liabilities, but high-numbered tiles can be bigger liabilities if they get flipped (which is harder). One lucky play with a 20-army tile can cause a swing of 200 (from +100 to -100 armies). So tile placement will have both offensive and defensive considerations. Comment 1,2,4 seem to resemble a minimax strategy where we minimize the maximum expected possible loss (modified by some probabilistic consideration of the value ß the opponent can get from 1..20 i.e. a structure which can only be flipped by a ß=20 tile is 'nearly impregnable'.) I'm not clear what the implications of comments 3,5,6 are for optimal strategy. Interested in comments from Go, Chess or Othello players. (The sequel ProximityHD for XBox Live, allows 4-player -cooperative or -competitive local multiplayer increases the branching factor since you now have 5 tiles in your hand at any given time, of which you can only play one. Reinforcement of ally tiles is increased to +2 per ally.)

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  • Two network interfaces and two IP addresses on the same subnet in Linux

    - by Scott Duckworth
    I recently ran into a situation where I needed two IP addresses on the same subnet assigned to one Linux host so that we could run two SSL/TLS sites. My first approach was to use IP aliasing, e.g. using eth0:0, eth0:1, etc, but our network admins have some fairly strict settings in place for security that squashed this idea: They use DHCP snooping and normally don't allow static IP addresses. Static addressing is accomplished by using static DHCP entries, so the same MAC address always gets the same IP assignment. This feature can be disabled per switchport if you ask and you have a reason for it (thankfully I have a good relationship with the network guys and this isn't hard to do). With the DHCP snooping disabled on the switchport, they had to put in a rule on the switch that said MAC address X is allowed to have IP address Y. Unfortunately this had the side effect of also saying that MAC address X is ONLY allowed to have IP address Y. IP aliasing required that MAC address X was assigned two IP addresses, so this didn't work. There may have been a way around these issues on the switch configuration, but in an attempt to preserve good relations with the network admins I tried to find another way. Having two network interfaces seemed like the next logical step. Thankfully this Linux system is a virtual machine, so I was able to easily add a second network interface (without rebooting, I might add - pretty cool). A few keystrokes later I had two network interfaces up and running and both pulled IP addresses from DHCP. But then the problem came in: the network admins could see (on the switch) the ARP entry for both interfaces, but only the first network interface that I brought up would respond to pings or any sort of TCP or UDP traffic. After lots of digging and poking, here's what I came up with. It seems to work, but it also seems to be a lot of work for something that seems like it should be simple. Any alternate ideas out there? Step 1: Enable ARP filtering on all interfaces: # sysctl -w net.ipv4.conf.all.arp_filter=1 # echo "net.ipv4.conf.all.arp_filter = 1" >> /etc/sysctl.conf From the file networking/ip-sysctl.txt in the Linux kernel docs: arp_filter - BOOLEAN 1 - Allows you to have multiple network interfaces on the same subnet, and have the ARPs for each interface be answered based on whether or not the kernel would route a packet from the ARP'd IP out that interface (therefore you must use source based routing for this to work). In other words it allows control of which cards (usually 1) will respond to an arp request. 0 - (default) The kernel can respond to arp requests with addresses from other interfaces. This may seem wrong but it usually makes sense, because it increases the chance of successful communication. IP addresses are owned by the complete host on Linux, not by particular interfaces. Only for more complex setups like load- balancing, does this behaviour cause problems. arp_filter for the interface will be enabled if at least one of conf/{all,interface}/arp_filter is set to TRUE, it will be disabled otherwise Step 2: Implement source-based routing I basically just followed directions from http://lartc.org/howto/lartc.rpdb.multiple-links.html, although that page was written with a different goal in mind (dealing with two ISPs). Assume that the subnet is 10.0.0.0/24, the gateway is 10.0.0.1, the IP address for eth0 is 10.0.0.100, and the IP address for eth1 is 10.0.0.101. Define two new routing tables named eth0 and eth1 in /etc/iproute2/rt_tables: ... top of file omitted ... 1 eth0 2 eth1 Define the routes for these two tables: # ip route add default via 10.0.0.1 table eth0 # ip route add default via 10.0.0.1 table eth1 # ip route add 10.0.0.0/24 dev eth0 src 10.0.0.100 table eth0 # ip route add 10.0.0.0/24 dev eth1 src 10.0.0.101 table eth1 Define the rules for when to use the new routing tables: # ip rule add from 10.0.0.100 table eth0 # ip rule add from 10.0.0.101 table eth1 The main routing table was already taken care of by DHCP (and it's not even clear that its strictly necessary in this case), but it basically equates to this: # ip route add default via 10.0.0.1 dev eth0 # ip route add 130.127.48.0/23 dev eth0 src 10.0.0.100 # ip route add 130.127.48.0/23 dev eth1 src 10.0.0.101 And voila! Everything seems to work just fine. Sending pings to both IP addresses works fine. Sending pings from this system to other systems and forcing the ping to use a specific interface works fine (ping -I eth0 10.0.0.1, ping -I eth1 10.0.0.1). And most importantly, all TCP and UDP traffic to/from either IP address works as expected. So again, my question is: is there a better way to do this? This seems like a lot of work for a seemingly simple problem.

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  • Code Golf: Finite-state machine!

    - by Adam Matan
    Finite state machine A deterministic finite state machine is a simple computation model, widely used as an introduction to automata theory in basic CS courses. It is a simple model, equivalent to regular expression, which determines of a certain input string is Accepted or Rejected. Leaving some formalities aside, A run of a finite state machine is composed of: alphabet, a set of characters. states, usually visualized as circles. One of the states must be the start state. Some of the states might be accepting, usually visualized as double circles. transitions, usually visualized as directed arches between states, are directed links between states associated with an alphabet letter. input string, a list of alphabet characters. A run on the machine begins at the starting state. Each letter of the input string is read; If there is a transition between the current state and another state which corresponds to the letter, the current state is changed to the new state. After the last letter was read, if the current state is an accepting state, the input string is accepted. If the last state was not an accepting state, or a letter had no corresponding arch from a state during the run, the input string is rejected. Note: This short descruption is far from being a full, formal definition of a FSM; Wikipedia's fine article is a great introduction to the subject. Example For example, the following machine tells if a binary number, read from left to right, has an even number of 0s: The alphabet is the set {0,1}. The states are S1 and S2. The transitions are (S1, 0) -> S2, (S1, 1) -> S1, (S2, 0) -> S1 and (S2, 1) -> S2. The input string is any binary number, including an empty string. The rules: Implement a FSM in a language of your choice. Input The FSM should accept the following input: <States> List of state, separated by space mark. The first state in the list is the start state. Accepting states begin with a capital letter. <transitions> One or more lines. Each line is a three-tuple: origin state, letter, destination state) <input word> Zero or more characters, followed by a newline. For example, the aforementioned machine with 1001010 as an input string, would be written as: S1 s2 S1 0 s2 S1 1 S1 s2 0 S1 s2 1 s2 1001010 Output The FSM's run, written as <State> <letter> -> <state>, followed by the final state. The output for the example input would be: S1 1 -> S1 S1 0 -> s2 s2 0 -> S1 S1 1 -> S1 S1 0 -> s2 s2 1 -> s2 s2 0 -> S1 ACCEPT For the empty input '': S1 ACCEPT For 101: S1 1 -> S1 S1 0 -> s2 s2 1 -> s2 REJECT For '10X': S1 1 -> S1 S1 0 -> s2 s2 X REJECT Prize A nice bounty will be given to the most elegant and short solution. Reference implementation A reference Python implementation will be published soon.

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  • Linux policy routing - packets not coming back

    - by Bugsik
    i am trying to set up policy routing on my home server. My network looks like this: Host routed VPN gateway Internet link through VPN 192.168.0.35/24 ---> 192.168.0.5/24 ---> 192.168.0.1 DSL router 10.200.2.235/22 .... .... 10.200.0.1 VPN server The traffic from 192.168.0.32/27 should be and is routed through VPN. I wanted to define some routing policies to route some traffic from 192.168.0.5 through VPN as well - for start - from user with uid 2000. Policy routing is done using iptables mark target and ip rule fwmark. The problem: When connecting using user 2000 from 192.168.0.5 tcpdump shows outgoing packets, but nothing comes back. Traffic from 192.168.0.35 works fine (here I am not using fwmark but src policy). Here is my VPN gateway setup: # uname -a Linux placebo 3.2.0-34-generic #53-Ubuntu SMP Thu Nov 15 10:49:02 UTC 2012 i686 i686 i386 GNU/Linux # iptables -V iptables v1.4.12 # ip -V ip utility, iproute2-ss111117 IPtables rules (all policies in table filter are ACCEPT) # iptables -t mangle -nvL Chain PREROUTING (policy ACCEPT 770K packets, 314M bytes) pkts bytes target prot opt in out source destination Chain INPUT (policy ACCEPT 767K packets, 312M bytes) pkts bytes target prot opt in out source destination Chain FORWARD (policy ACCEPT 5520 packets, 1920K bytes) pkts bytes target prot opt in out source destination Chain OUTPUT (policy ACCEPT 782K packets, 901M bytes) pkts bytes target prot opt in out source destination 74 4707 MARK all -- * * 0.0.0.0/0 0.0.0.0/0 owner UID match 2000 MARK set 0x3 Chain POSTROUTING (policy ACCEPT 788K packets, 903M bytes) pkts bytes target prot opt in out source destination # iptables -t nat -nvL Chain PREROUTING (policy ACCEPT 996 packets, 51172 bytes) pkts bytes target prot opt in out source destination Chain INPUT (policy ACCEPT 7 packets, 432 bytes) pkts bytes target prot opt in out source destination Chain OUTPUT (policy ACCEPT 1364 packets, 112K bytes) pkts bytes target prot opt in out source destination Chain POSTROUTING (policy ACCEPT 2302 packets, 160K bytes) pkts bytes target prot opt in out source destination 119 7588 MASQUERADE all -- * vpn 0.0.0.0/0 0.0.0.0/0 Routing: # ip addr show 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: eth0: <BROADCAST,MULTICAST,PROMISC,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master lan state UNKNOWN qlen 1000 link/ether 00:40:63:f9:c3:8f brd ff:ff:ff:ff:ff:ff valid_lft forever preferred_lft forever 3: lan: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP link/ether 00:40:63:f9:c3:8f brd ff:ff:ff:ff:ff:ff inet 192.168.0.5/24 brd 192.168.0.255 scope global lan inet6 fe80::240:63ff:fef9:c38f/64 scope link valid_lft forever preferred_lft forever 4: vpn: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN qlen 100 link/none inet 10.200.2.235/22 brd 10.200.3.255 scope global vpn # ip rule show 0: from all lookup local 32764: from all fwmark 0x3 lookup VPN 32765: from 192.168.0.32/27 lookup VPN 32766: from all lookup main 32767: from all lookup default # ip route show table VPN default via 10.200.0.1 dev vpn 10.200.0.0/22 dev vpn proto kernel scope link src 10.200.2.235 192.168.0.0/24 dev lan proto kernel scope link src 192.168.0.5 # ip route show default via 192.168.0.1 dev lan metric 100 10.200.0.0/22 dev vpn proto kernel scope link src 10.200.2.235 192.168.0.0/24 dev lan proto kernel scope link src 192.168.0.5 TCP dump showing no traffic coming back when connection is made from 192.168.0.5 user 2000 # tcpdump -i vpn tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on vpn, link-type RAW (Raw IP), capture size 65535 bytes ### Traffic from user 2000 on 192.168.0.5 ### 10:19:05.629985 IP 10.200.2.235.37291 > 10.100-78-194.akamai.com.http: Flags [S], seq 2868799562, win 14600, options [mss 1460,sackOK,TS val 6887764 ecr 0,nop,wscale 4], length 0 10:19:21.678001 IP 10.200.2.235.37291 > 10.100-78-194.akamai.com.http: Flags [S], seq 2868799562, win 14600, options [mss 1460,sackOK,TS val 6891776 ecr 0,nop,wscale 4], length 0 ### Traffic from 192.168.0.35 ### 10:23:12.066174 IP 10.200.2.235.49247 > 10.100-78-194.akamai.com.http: Flags [S], seq 2294159276, win 65535, options [mss 1460,nop,wscale 4,nop,nop,TS val 557451322 ecr 0,sackOK,eol], length 0 10:23:12.265640 IP 10.100-78-194.akamai.com.http > 10.200.2.235.49247: Flags [S.], seq 2521908813, ack 2294159277, win 14480, options [mss 1367,sackOK,TS val 388565772 ecr 557451322,nop,wscale 1], length 0 10:23:12.276573 IP 10.200.2.235.49247 > 10.100-78-194.akamai.com.http: Flags [.], ack 1, win 8214, options [nop,nop,TS val 557451534 ecr 388565772], length 0 10:23:12.293030 IP 10.200.2.235.49247 > 10.100-78-194.akamai.com.http: Flags [P.], seq 1:480, ack 1, win 8214, options [nop,nop,TS val 557451552 ecr 388565772], length 479 10:23:12.574773 IP 10.100-78-194.akamai.com.http > 10.200.2.235.49247: Flags [.], ack 480, win 7776, options [nop,nop,TS val 388566081 ecr 557451552], length 0

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  • Eclipse Helios on OS X Snow Leopard crashes frequently when editing certain PHP files

    - by William
    I use Eclipse Helios (Eclipse Platform: 3.6.0.I20100608-0911, Eclipse IDE for PHP Developers: 1.3.0.20100617-0520) all the time on OS X (Snow Leopard), and it seems I only run into trouble whenever I'm editing a PHP file that's part of the WordPress blogging framework. When I move my cursor to a variable or function name, that often triggers the beach ball of death. I suspect Eclipse is trying to look up that variable/function and for some reason that causes an endless loop. Sometimes it's not just variables or functions. Just today I was trying to replace all occurrences of a quoted string. Every time I clicked "Replace All", the program would freeze immediately after the string was replaced and the text cursor was moved to the replaced position. I think the moving of the text cursor is important, because I got the same result when I searched for the string (thus moving the cursor), but NOT when I searched for a nonexistent string. I tried disabling everything in my preferences related to marked occurrences, hovering, code assistance, etc. Nothing helps. I use Eclipse for all my projects, and I find that it's only WordPress projects where this happens. Here's my eclipse.ini file: -startup ../../../plugins/org.eclipse.equinox.launcher_1.1.0.v20100507.jar --launcher.library ../../../plugins/org.eclipse.equinox.launcher.cocoa.macosx_1.1.0.v20100503 -product org.eclipse.epp.package.php.product --launcher.defaultAction openFile -showsplash org.eclipse.platform --launcher.XXMaxPermSize 512m --launcher.defaultAction openFile -vmargs -Dosgi.requiredJavaVersion=1.5 -XstartOnFirstThread -Dorg.eclipse.swt.internal.carbon.smallFonts -XX:PermSize=128m -XX:MaxPermSize=128m -XX:MaxGCPauseMillis=10 -XX:MaxHeapFreeRatio=70 -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:+CMSIncrementalPacing -XX:CompileThreshold=5 -Xms128m -Xmx512m -Xss2m -Xdock:icon=../Resources/Eclipse.icns -XstartOnFirstThread -Dorg.eclipse.swt.internal.carbon.smallFonts -framework ../../../plugins/org.eclipse.osgi.services_3.2.100.v20100503.jar I have 4GB of RAM, so I don't know if the problem is I'm underutilizing my resources. Here's what I see over and over in the error log: !ENTRY org.eclipse.jface 2 0 2011-01-16 16:26:21.533 !MESSAGE Keybinding conflicts occurred. They may interfere with normal accelerator operation. !SUBENTRY 1 org.eclipse.jface 2 0 2011-01-16 16:26:21.533 !MESSAGE A conflict occurred for ALT+COMMAND+Q P: Binding(ALT+COMMAND+Q P, ParameterizedCommand(Command(org.eclipse.ui.views.showView,Show View, Shows a particular view, Category(org.eclipse.ui.category.views,Views,Commands for opening views,true), org.eclipse.ui.handlers.ShowViewHandler@2a46d1, [Lorg.eclipse.ui.internal.commands.Parameter;@18f50c2,,true), [Lorg.eclipse.core.commands.Parameterization;@1ff1855), org.eclipse.ui.defaultAcceleratorConfiguration, org.eclipse.ui.contexts.window,,cocoa,system) Binding(ALT+COMMAND+Q P, ParameterizedCommand(Command(org.eclipse.ui.views.showView,Show View, Shows a particular view, Category(org.eclipse.ui.category.views,Views,Commands for opening views,true), org.eclipse.ui.handlers.ShowViewHandler@2a46d1, [Lorg.eclipse.ui.internal.commands.Parameter;@18f50c2,,true), [Lorg.eclipse.core.commands.Parameterization;@96b40c), org.eclipse.ui.defaultAcceleratorConfiguration, org.eclipse.ui.contexts.window,,cocoa,system) !ENTRY org.eclipse.core.net 1 0 2011-01-16 16:26:22.217 !MESSAGE System property http.proxyHost has been set to 127.0.0.1 by an external source. This value will be overwritten using the values from the preferences !ENTRY org.eclipse.core.net 1 0 2011-01-16 16:26:22.217 !MESSAGE System property http.proxyPort has been set to 8888 by an external source. This value will be overwritten using the values from the preferences !ENTRY org.eclipse.core.net 1 0 2011-01-16 16:26:22.218 !MESSAGE System property https.proxyHost has been set to 127.0.0.1 by an external source. This value will be overwritten using the values from the preferences !ENTRY org.eclipse.core.net 1 0 2011-01-16 16:26:22.219 !MESSAGE System property https.proxyPort has been set to 8888 by an external source. This value will be overwritten using the values from the preferences I did some experimenting with the particular script that's giving me trouble. It's a hybrid of HTML and PHP, so Eclipse has to do both HTML and PHP validation. I wondered if the HTML validation had something to do with it, so I created a new file, copied the contents over, and messed with the doctype element. I found that if I replaced the well-formed XHTML 1.0 Strict doctype element with a generic doctype (as such: <!DOCTYPE html>), then I did not crash the program just by moving the cursor around. I set all HTML validation rules to "Ignore", but it still didn't solve my problems. For now, I'm just going to echo the doctype using PHP instead of entering it literally. That seems to prevent crashes. I notice that when I move the cursor around the document, Eclipse displays the "xpath" to my current location at the bottom of the screen. Sometimes there's a delay while it figures out my current path. Perhaps when it's validating against the Strict doctype, it has problems quickly calculating the xpath as I move the cursor around? Maybe it has a stack overflow that causes it to crash.

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  • Solving Combinatory Problems with LINQ /.NET4

    - by slf
    I saw this article pop-up in my MSDN RSS feed, and after reading through it, and the sourced article here I began to wonder about the solution. The rules are simple: Find a number consisting of 9 digits in which each of the digits from 1 to 9 appears only once. This number must also satisfy these divisibility requirements: The number should be divisible by 9. If the rightmost digit is removed, the remaining number should be divisible by 8. If the rightmost digit of the new number is removed, the remaining number should be divisible by 7. And so on, until there's only one digit (which will necessarily be divisible by 1). This is his proposed monster LINQ query: // C# and LINQ solution to the numeric problem presented in: // http://software.intel.com/en-us/blogs/2009/12/07/intel-parallel-studio-great-for-serial-code-too-episode-1/ int[] oneToNine = new int[] { 1, 2, 3, 4, 5, 6, 7, 8, 9 }; // the query var query = from i1 in oneToNine from i2 in oneToNine where i2 != i1 && (i1 * 10 + i2) % 2 == 0 from i3 in oneToNine where i3 != i2 && i3 != i1 && (i1 * 100 + i2 * 10 + i3) % 3 == 0 from i4 in oneToNine where i4 != i3 && i4 != i2 && i4 != i1 && (i1 * 1000 + i2 * 100 + i3 * 10 + i4) % 4 == 0 from i5 in oneToNine where i5 != i4 && i5 != i3 && i5 != i2 && i5 != i1 && (i1 * 10000 + i2 * 1000 + i3 * 100 + i4 * 10 + i5) % 5 == 0 from i6 in oneToNine where i6 != i5 && i6 != i4 && i6 != i3 && i6 != i2 && i6 != i1 && (i1 * 100000 + i2 * 10000 + i3 * 1000 + i4 * 100 + i5 * 10 + i6) % 6 == 0 from i7 in oneToNine where i7 != i6 && i7 != i5 && i7 != i4 && i7 != i3 && i7 != i2 && i7 != i1 && (i1 * 1000000 + i2 * 100000 + i3 * 10000 + i4 * 1000 + i5 * 100 + i6 * 10 + i7) % 7 == 0 from i8 in oneToNine where i8 != i7 && i8 != i6 && i8 != i5 && i8 != i4 && i8 != i3 && i8 != i2 && i8 != i1 && (i1 * 10000000 + i2 * 1000000 + i3 * 100000 + i4 * 10000 + i5 * 1000 + i6 * 100 + i7 * 10 + i8) % 8 == 0 from i9 in oneToNine where i9 != i8 && i9 != i7 && i9 != i6 && i9 != i5 && i9 != i4 && i9 != i3 && i9 != i2 && i9 != i1 let number = i1 * 100000000 + i2 * 10000000 + i3 * 1000000 + i4 * 100000 + i5 * 10000 + i6 * 1000 + i7 * 100 + i8 * 10 + i9 * 1 where number % 9 == 0 select number; // run it! foreach (int n in query) Console.WriteLine(n); Octavio states "Note that no attempt at all has been made to optimize the code", what I'd like to know is what if we DID attempt to optimize this code. Is this really the best this code can get? I'd like to know how we can do this best with .NET4, in particular doing as much in parallel as we possibly can. I'm not necessarily looking for an answer in pure LINQ, assume .NET4 in any form (managed c++, c#, etc all acceptable).

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  • jQuery Validation hiding or tearing down jquery Modal Dialog on submit

    - by Programmin Tool
    Basically when clicking the modal created submit button, and calling jQuery('#FormName').submit(), it will run the validation and then call the method assigned in the submitHandler. After that it is either creating a new modal div or hiding the form, and I don't get why. I have debugged it and noticed that after the method call in the submitHandler, the form .is(':hidden') = true and this is true for the modal div also. I'm positive I've done this before but can't seem to figure out what I've done wrong this time. The odd this is a modal div is showing up on the screen, but it's completely devoid of content. (Even after putting in random text outside of the form. It's like it's a whole new modal div) Here are the set up methods: function setUpdateTaskDiv() { jQuery("#UpdateTaskForm").validate({ errorLabelContainer: "#ErrorDiv", wrapper: "div", rules: { TaskSubject: { required: true } }, messages: { TaskSubject: { required: 'Subject is required.' } }, onfocusout: false, onkeyup: false, submitHandler: function(label) { updateTaskSubject(null); } } ); jQuery('#UpdateDiv').dialog({ autoOpen: false, bgiframe: true, height: 400, width: 500, modal: true, beforeclose: function() { }, buttons: { Submit: function() { jQuery('#UpdateTaskForm').submit(); }, Cancel: function() { ... } } }); where: function updateTaskSubject(task) { //does nothing, it's just a shell right now } Doesn't really do anything right now. Here's the html: <div id="UpdateDiv"> <div id="ErrorDiv"> </div> <form method="post" id="UpdateTaskForm" action="Calendar.html"> <div> <div class="floatLeft"> Date: </div> <div class="floatLeft"> </div> <div class="clear"> </div> </div> <div> <div class="floatLeft"> Start Time: </div> <div class="floatLeft"> <select id="TaskStartDate" name="TaskStartDate"> </select> </div> <div class="clear"> </div> </div> <div> <div class="floatLeft"> End Time: </div> <div class="floatLeft"> <select id="TaskEndDate" name="TaskEndDate"> </select> </div> <div class="clear"> </div> </div> <div> <div class="floatLeft"> Subject: </div> <div class="floatLeft"> <textarea id="TaskSubject" name="TaskSubject" cols="30" rows="10"></textarea> </div> <div class="clear"> </div> </div> <div> <input type="hidden" id="TaskId" value="" /> </div> <div class="clear"></div> </form> </div> Odd Discovery Turns out that the examples that I got this to work all had the focus being put back on the modal itself. For example, using the validator to add messages to the error div. (Success or not) Without doing this, the modal dialog apparently thinks that it's done with what it needs to do and just hides everything. Not sure exactly why, but to stop this behavior some kind of focus has to be assigned to something within the div itself.

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  • Error Handling without Exceptions

    - by James
    While searching SO for approaches to error handling related to business rule validation , all I encounter are examples of structured exception handling. MSDN and many other reputable development resources are very clear that exceptions are not to be used to handle routine error cases. They are only to be used for exceptional circumstances and unexpected errors that may occur from improper use by the programmer (but not the user.) In many cases, user errors such as fields that are left blank are common, and things which our program should expect, and therefore are not exceptional and not candidates for use of exceptions. QUOTE: Remember that the use of the term exception in programming has to do with the thinking that an exception should represent an exceptional condition. Exceptional conditions, by their very nature, do not normally occur; so your code should not throw exceptions as part of its everyday operations. Do not throw exceptions to signal commonly occurring events. Consider using alternate methods to communicate to a caller the occurrence of those events and leave the exception throwing for when something truly out of the ordinary happens. For example, proper use: private void DoSomething(string requiredParameter) { if (requiredParameter == null) throw new ArgumentExpcetion("requiredParameter cannot be null"); // Remainder of method body... } Improper use: // Renames item to a name supplied by the user. Name must begin with an "F". public void RenameItem(string newName) { // Items must have names that begin with "F" if (!newName.StartsWith("F")) throw new RenameException("New name must begin with /"F/""); // Remainder of method body... } In the above case, according to best practices, it would have been better to pass the error up to the UI without involving/requiring .NET's exception handling mechanisms. Using the same example above, suppose one were to need to enforce a set of naming rules against items. What approach would be best? Having the method return a enumerated result? RenameResult.Success, RenameResult.TooShort, RenameResult.TooLong, RenameResult.InvalidCharacters, etc. Using an event in a controller class to report to the UI class? The UI calls the controller's RenameItem method, and then handles an AfterRename event that the controller raises and that has rename status as part of the event args? The controlling class directly references and calls a method from the UI class that handles the error, e.g. ReportError(string text). Something else... ? Essentially, I want to know how to perform complex validation in classes that may not be the Form class itself, and pass the errors back to the Form class for display -- but I do not want to involve exception handling where it should not be used (even though it seems much easier!) Based on responses to the question, I feel that I'll have to state the problem in terms that are more concrete: UI = User Interface, BLL = Business Logic Layer (in this case, just a different class) User enters value within UI. UI reports value to BLL. BLL performs routine validation of the value. BLL discovers rule violation. BLL returns rule violation to UI. UI recieves return from BLL and reports error to user. Since it is routine for a user to enter invalid values, exceptions should not be used. What is the right way to do this without exceptions?

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  • MVC Page not showing up, 404 not found

    - by mwright
    I have a very simple MVC site that is returning a 404 not found error when trying to load a page at the very beginning. I'm looking for some direction to troubleshoot this problem since there is really nothing to go on from the error message. The error I'm getting is: Description: HTTP 404. The resource you are looking for (or one of its dependencies) could have been removed, had its name changed, or is temporarily unavailable. Please review the following URL and make sure that it is spelled correctly. Requested URL: /Views/Other/Index.aspx Below I have included the code for the various pieces, routing rules are default: routes.MapRoute( "Default", // Route name "{controller}/{action}/{id}", // URL with parameters new { controller = "Home", action = "Index", id = UrlParameter.Optional} // Parameter defaults ); The site is using nested MasterPages, not sure if this is involved with the problem but trying to include as much detail as possible. I have: Controllers OtherController Views: Shared Folder: Site.Master Other Folder: Other.Master Index.aspx Site.Master Code: <%@ Master Language="C#" Inherits="System.Web.Mvc.ViewMasterPage" %> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" > <head runat="server"> <title> <asp:ContentPlaceHolder ID="TitleContent" runat="server" /> </title> </head> <body> <div> <asp:ContentPlaceHolder ID="MainContent" runat="server"> </asp:ContentPlaceHolder> </div> </body> </html> Other.Master Code: <%@ Master Language="C#" MasterPageFile="~/Views/Shared/Site.Master" Inherits="System.Web.Mvc.ViewMasterPage" %> <asp:Content ID="OtherTitle" ContentPlaceHolderID="TitleContent" runat="server"> OTHER PAGE - MASTER TITLE <asp:ContentPlaceHolder ID="OtherPageTitle" runat="server"> </asp:ContentPlaceHolder> </asp:Content> <asp:Content ID="OtherContent" ContentPlaceHolderID="MainContent" runat="server"> Some other content. <asp:ContentPlaceHolder ID="PageContent" runat="server"> </asp:ContentPlaceHolder> </asp:Content> Index.aspx Code: <%@ Page Title="" Language="C#" MasterPageFile="~/Views/Other/Other.Master" Inherits="System.Web.Mvc.ViewPage" %> <asp:Content ID="IndexTitle" ContentPlaceHolderID="OtherTitle" runat="server"> Home </asp:Content> <asp:Content ID="IndexContent" ContentPlaceHolderID="OtherContent" runat="server"> Index content </asp:Content> OtherController Code namespace MVCProject.Controllers { public class OtherController : Controller { // // GET: /Member/ public ActionResult Index() { // Have also tried: // return View("Index", "Other.Master"); return View(); } } }

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  • Find optimal/good-enough strategy and AI for the game 'Proximity'?

    - by smci
    'Proximity' is a strategy game of territorial domination similar to Othello, Go and Risk. Two players, uses a 10x12 hex grid. Game invented by Brian Cable in 2007. Seems to be a worthy game for discussing a) optimal algorithm then b) how to build an AI. Strategies are going to be probabilistic or heuristic-based, due to the randomness factor, and the insane branching factor (20^120). So it will be kind of hard to compare objectively. A compute time limit of 5s per turn seems reasonable. Game: Flash version here and many copies elsewhere on the web Rules: here Object: to have control of the most armies after all tiles have been placed. Each turn you received a randomly numbered tile (value between 1 and 20 armies) to place on any vacant board space. If this tile is adjacent to any ally tiles, it will strengthen each tile's defenses +1 (up to a max value of 20). If it is adjacent to any enemy tiles, it will take control over them if its number is higher than the number on the enemy tile. Thoughts on strategy: Here are some initial thoughts; setting the computer AI to Expert will probably teach a lot: minimizing your perimeter seems to be a good strategy, to prevent flips and minimize worst-case damage like in Go, leaving holes inside your formation is lethal, only more so with the hex grid because you can lose armies on up to 6 squares in one move low-numbered tiles are a liability, so place them away from your main territory, near the board edges and scattered. You can also use low-numbered tiles to plug holes in your formation, or make small gains along the perimeter which the opponent will not tend to bother attacking. a triangle formation of three pieces is strong since they mutually reinforce, and also reduce the perimeter Each tile can be flipped at most 6 times, i.e. when its neighbor tiles are occupied. Control of a formation can flow back and forth. Sometimes you lose part of a formation and plug any holes to render that part of the board 'dead' and lock in your territory/ prevent further losses. Low-numbered tiles are obvious-but-low-valued liabilities, but high-numbered tiles can be bigger liabilities if they get flipped (which is harder). One lucky play with a 20-army tile can cause a swing of 200 (from +100 to -100 armies). So tile placement will have both offensive and defensive considerations. Comment 1,2,4 seem to resemble a minimax strategy where we minimize the maximum expected possible loss (modified by some probabilistic consideration of the value ß the opponent can get from 1..20 i.e. a structure which can only be flipped by a ß=20 tile is 'nearly impregnable'.) I'm not clear what the implications of comments 3,5,6 are for optimal strategy. Interested in comments from Go, Chess or Othello players. (The sequel ProximityHD for XBox Live, allows 4-player -cooperative or -competitive local multiplayer increases the branching factor since you now have 5 tiles in your hand at any given time, of which you can only play one. Reinforcement of ally tiles is increased to +2 per ally.)

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  • How do I handle calls to AudioTrack from jni without crashing?

    - by icecream
    I was trying to write to an AudioTrack from a jni callback, and I get a signal 7 (SIGBUS), fault addr 00000000. I have looked at the Wolf3D example for odroid and they seem to use a android.os.Handler to post a Runnable that will do an update in the correct thread context. I have also tried AttachCurrentThread, but I fail in this case also. It works to play the sound when running from the constructor even if I wrap it in a thread and then post it to the handler. When I do the "same" via a callback from jni it fails. I assume I am braeaking some rules, but I haven't been able to figure out what they are. So far, I haven't found the answer here on SO. So I wonder if anyone knows how this should be done. EDIT: Answered below. The following code is to illustrate the problem. Java: package com.example.jniaudiotrack; import android.app.Activity; import android.media.AudioFormat; import android.media.AudioManager; import android.media.AudioTrack; import android.os.Bundle; import android.os.Handler; import android.util.Log; public class JniAudioTrackActivity extends Activity { AudioTrack mAudioTrack; byte[] mArr; public static final Handler mHandler = new Handler(); /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); mArr = new byte[2048]; for (int i = 0; i < 2048; i++) { mArr[i] = (byte) (Math.sin(i) * 128); } mAudioTrack = new AudioTrack(AudioManager.STREAM_MUSIC, 11025, AudioFormat.CHANNEL_CONFIGURATION_MONO, AudioFormat.ENCODING_PCM_8BIT, 2048, AudioTrack.MODE_STREAM); mAudioTrack.play(); new Thread(new Runnable() { public void run() { mHandler.post(new Runnable() { public void run() { mAudioTrack.write(mArr, 0, 2048); Log.i(TAG, "*** Handler from constructor ***"); } }); } }).start(); new Thread(new Runnable() { public void run() { audioFunc(); } }).start(); } public native void audioFunc(); @SuppressWarnings("unused") private void audioCB() { mHandler.post(new Runnable() { public void run() { mAudioTrack.write(mArr, 0, 2048); Log.i(TAG, "*** audioCB called ***"); } }); } private static final String TAG = "JniAudioTrackActivity"; static { System.loadLibrary("jni_audiotrack"); } } cpp: #include <jni.h> extern "C" { JNIEXPORT void Java_com_example_jniaudiotrack_JniAudioTrackActivity_audioFunc(JNIEnv* env, jobject obj); } JNIEXPORT void Java_com_example_jniaudiotrack_JniAudioTrackActivity_audioFunc(JNIEnv* env, jobject obj) { JNIEnv* jniEnv; JavaVM* vm; env->GetJavaVM(&vm); vm->AttachCurrentThread(&jniEnv, 0); jclass cls = env->GetObjectClass(obj); jmethodID audioCBID = env->GetMethodID(cls, "audioCB", "()V"); if (!audioCBID) { return; } env->CallVoidMethod(cls, audioCBID); } Trace snippet: I/DEBUG ( 1653): pid: 9811, tid: 9811 >>> com.example.jniaudiotrack <<< I/DEBUG ( 1653): signal 7 (SIGBUS), fault addr 00000000 I/DEBUG ( 1653): r0 00000800 r1 00000026 r2 00000001 r3 00000000 I/DEBUG ( 1653): r4 42385726 r5 41049e54 r6 bee25570 r7 ad00e540 I/DEBUG ( 1653): r8 000040f8 r9 41048200 10 41049e44 fp 00000000 I/DEBUG ( 1653): ip 000000f8 sp bee25530 lr ad02dbb5 pc ad012358 cpsr 20000010 I/DEBUG ( 1653): #00 pc 00012358 /system/lib/libdvm.so

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  • IIS7 FTP Setup - An error occured during the authentication process. 530 End Login failed

    - by robmzd
    I'm having a problem very similar to IIS 7.5 FTP IIS Manager Users Login Fail (530) on Windows Server 2008 R2 Standard. I have created an FTP site and IIS Manager user but am having trouble logging in. I could really do with getting this working with the IIS Manager user rather than by creating a new system user since I'm fairly restricted with those accounts. Here is the output when connecting locally through command prompt: C:\Windows\system32>ftp localhost Connected to MYSERVER. 220 Microsoft FTP Service User (MYSERVER:(none)): MyFtpLogin 331 Password required for MyFtpLogin. Password: *** 530-User cannot log in. Win32 error: Logon failure: unknown user name or bad password. Error details: An error occured during the authentication process. 530 End Login failed. I have followed the guide to configure ftp with iis manager authentication in iis 7 and Adding FTP Publishing to a Web Site in IIS 7 Things I have done and checked: The FTP Service is installed (along with FTP Extensibility). Local Service and Network Service have been given access to the site folder Permission has been given to the config files Granted read/write permissions to the FTP Root folder The Management Service is installed and running Enable remote connections is ticked with 'Windows credentials or IIS manager credentials' selected The IIS Manager User has been added to the server (root connection in the IIS connections branch) The new FTP site has been added IIS Manager Authentication has been added to the FTP authentication providers The IIS Manager user has been added to the IIS Manager Permissions list for the site Added Read/Write permissions for the user in the FTP Authorization Rules Here's a section of the applicationHost config file associated with the FTP site <site name="MySite" id="8"> <application path="/" applicationPool="MyAppPool"> <virtualDirectory path="/" physicalPath="D:\Websites\MySite" /> </application> <bindings> <binding protocol="http" bindingInformation="*:80:www.mydomain.co.uk" /> <binding protocol="ftp" bindingInformation="*:21:www.mydomain.co.uk" /> </bindings> <ftpServer> <security> <ssl controlChannelPolicy="SslAllow" dataChannelPolicy="SslAllow" /> <authentication> <basicAuthentication enabled="true" /> <customAuthentication> <providers> <add name="IisManagerAuth" enabled="true" /> </providers> </customAuthentication> </authentication> </security> </ftpServer> </site> ... <location path="MySite"> <system.ftpServer> <security> <authorization> <add accessType="Allow" users="MyFtpLogin" permissions="Read, Write" /> </authorization> </security> </system.ftpServer> </location> If I connect to the Site (not FTP) from my local IIS Manager using the same IIS Manager account details then it connects fine, I can browse files and change settings as I would locally (though I don't seem to have an option to upload files). Trying to connect via FTP though either through the browser or FileZilla etc... gives me: Status: Resolving address of www.mydomain.co.uk Status: Connecting to 123.456.12.123:21... Status: Connection established, waiting for welcome message... Response: 220 Microsoft FTP Service Command: USER MyFtpLogin Response: 331 Password required for MyFtpLogin. Command: PASS ********* Response: 530 User cannot log in. Error: Critical error Error: Could not connect to server I have tried collecting etw traces for ftp sessions, in the logs I get a FailBasicLogon followed by a FailCustomLogon, but no other info: FailBasicLogon SessionId={cad26a97-225d-45ba-ab1f-f6acd9046e55} | ErrorCode=0x8007052E StartCustomLogon SessionId={cad26a97-225d-45ba-ab1f-f6acd9046e55} | LogonProvider=IisManagerAuth StartCallProvider SessionId={cad26a97-225d-45ba-ab1f-f6acd9046e55} | provider=IisManagerAuth EndCallProvider SessionId={cad26a97-225d-45ba-ab1f-f6acd9046e55} EndCustomLogon SessionId={cad26a97-225d-45ba-ab1f-f6acd9046e55} FailCustomLogon SessionId={cad26a97-225d-45ba-ab1f-f6acd9046e55} | ErrorCode=0x8007052E FailFtpCommand SessionId={cad26a97-225d-45ba-ab1f-f6acd9046e55} | ReturnValue=0x8007052E | SubStatus=ERROR_DURING_AUTHENTICATION In the normal FTP logs I just get: 2012-10-23 16:13:11 123.456.12.123 - 123.456.12.123 21 ControlChannelOpened - - 0 0 e2d4e935-fb31-4f2c-af79-78d75d47c18e - 2012-10-23 16:13:11 123.456.12.123 - 123.456.12.123 21 USER MyFtpLogin 331 0 0 e2d4e935-fb31-4f2c-af79-78d75d47c18e - 2012-10-23 16:13:11 123.456.12.123 - 123.456.12.123 21 PASS *** 530 1326 41 e2d4e935-fb31-4f2c-af79-78d75d47c18e - 2012-10-23 16:13:11 123.456.12.123 - 123.456.12.123 21 ControlChannelClosed - - 0 0 e2d4e935-fb31-4f2c-af79-78d75d47c18e - If anyone has any ideas than I would be very grateful to hear them. Many thanks.

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  • Need help debugging a very basic PHP SOAP Hello world app

    - by WarDoGG
    I have been breaking my head at this, reading almost every article and tutorial there is on the web, but nothing doing.. i still cannot get my first web service application to work. I would really appreciate it if anyone could debug this code for me and provide me with a good explanation as to what is wrong and why. This will help indeed ! Thanks ! I have pasted below the entire codes that i am using making it easier to debug. I'm using the PHP5 SOAP extension. Here is my WSDL: <?xml version="1.0" encoding="utf-8"?> <wsdl:definitions name="testWebservice" xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/" xmlns:tm="http://microsoft.com/wsdl/mime/textMatching/" xmlns:soapenc="http://schemas.xmlsoap.org/soap/encoding/" xmlns:mime="http://schemas.xmlsoap.org/wsdl/mime/" xmlns:tns="http://tempuri.org/" xmlns:s1="http://microsoft.com/wsdl/types/" xmlns:s="http://www.w3.org/2001/XMLSchema" xmlns:soap12="http://schemas.xmlsoap.org/wsdl/soap12/" xmlns:http="http://schemas.xmlsoap.org/wsdl/http/" targetNamespace="http://tempuri.org/" xmlns:wsdl="http://schemas.xmlsoap.org/wsdl/"> <wsdl:types> <s:schema elementFormDefault="qualified" targetNamespace="http://tempuri.org/"> <s:import namespace="http://microsoft.com/wsdl/types/" /> <s:element name="getUser"> <s:complexType> <s:sequence> <s:element minOccurs="0" maxOccurs="1" name="username" type="s:string" /> <s:element minOccurs="0" maxOccurs="1" name="password" type="s:string" /> </s:sequence> </s:complexType> </s:element> <s:element name="getUserResponse"> <s:complexType> <s:sequence> <s:element minOccurs="0" maxOccurs="1" name="getUserResult" type="tns:userInfo" /> </s:sequence> </s:complexType> </s:element> <s:complexType name="userInfo"> <s:sequence> <s:element minOccurs="1" maxOccurs="1" name="ID" type="s:int" /> <s:element minOccurs="1" maxOccurs="1" name="authkey" type="s:int" /> </s:sequence> </s:complexType> </s:schema> </wsdl:types> <wsdl:message name="getUserSoapIn"> <wsdl:part name="parameters" element="tns:getUser" /> </wsdl:message> <wsdl:message name="getUserSoapOut"> <wsdl:part name="parameters" element="tns:getUserResponse" /> </wsdl:message> <wsdl:portType name="testWebservice"> <wsdl:operation name="getUser"> <wsdl:input message="tns:getUserSoapIn" /> <wsdl:output message="tns:getUserSoapOut" /> </wsdl:operation> </wsdl:portType> <wsdl:binding name="testWebserviceBinding" type="tns:testWebservice"> <soap:binding style="document" transport="http://schemas.xmlsoap.org/soap/http" /> <wsdl:operation name="getUser"> <soap:operation soapAction="http://tempuri.org/getUser" /> <wsdl:input> <soap:body use="literal" /> </wsdl:input> <wsdl:output> <soap:body use="literal" /> </wsdl:output> </wsdl:operation> </wsdl:binding> <wsdl:service name="testWebserviceService"> <wsdl:port name="testWebservicePort" binding="tns:testWebserviceBinding"> <soap:address location="http://127.0.0.1/nusoap/storytruck/index.php" /> </wsdl:port> </wsdl:service> </wsdl:definitions> and here is the PHP Code i use to setup the server: <?php function getUser($user,$pass) { return array('ID'=>1); } ini_set("soap.wsdl_cache_enabled", "0"); // disabling WSDL cache $server = new SoapServer("http://127.0.0.1/mywsdl.wsdl"); $server->addFunction('getUser'); $server->handle(); ?> and the code for the client: <?php $client = new SoapClient("http://127.0.0.1/index.php?wsdl", array('exceptions' => 0)); try { $result = $client->getUser("username","pass"); print_r($result); } catch (SoapFault $result) { print_r($result); } ?> Here is the ERROR output i am getting on the browser : SoapFault Object ( [message:protected] => Error cannot find parameter [string:Exception:private] => [code:protected] => 0 [file:protected] => C:\xampp\htdocs\client.php [line:protected] => 6 [trace:Exception:private] => Array ( [0] => Array ( [function] => __call [class] => SoapClient [type] => -> [args] => Array ( [0] => getUser [1] => Array ( [0] => username [1] => pass ) ) ) [1] => Array ( [file] => C:\xampp\htdocs\client.php [line] => 6 [function] => getUser [class] => SoapClient [type] => -> [args] => Array ( [0] => username [1] => pass ) ) ) [previous:Exception:private] => [faultstring] => Error cannot find parameter [faultcode] => SOAP-ENV:Client )

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  • Writing a code example

    - by Stefano Borini
    I would like to have your feedback regarding code examples. One of the most frustrating experiences I sometimes have when learning a new technology is finding useless examples. I think an example as the most precious thing that comes with a new library, language, or technology. It must be a starting point, a wise and unadulterated explanation on how to achieve a given result. A perfect example must have the following characteristics: Self contained: it should be small enough to be compiled or executed as a single program, without dependencies or complex makefiles. An example is also a strong functional test if you correctly installed the new technology. The more issues could arise, the more likely is that something goes wrong, and the more difficult is to debug and solve the situation. Pertinent: it should demonstrate one, and only one, specific feature of your software/library, involving the minimal additional behavior from external libraries. Helpful: the code should bring you forward, step by step, using comments or self-documenting code. Extensible: the example code should be a small “framework” or blueprint for additional tinkering. A learner can start by adding features to this blueprint. Recyclable: it should be possible to extract parts of the example to use in your own code Easy: An example code is not the place to show your code-fu skillz. Keep it easy. helpful acronym: SPHERE. Prototypical examples of violations of those rules are the following: Violation of self-containedness: an example spanning multiple files without any real need for it. If your example is a python program, keep everything into a single module file. Don’t sub-modularize it. In Java, try to keep everything into a single class, unless you really must partition some entity into a meaningful object you need to pass around (and java mandates one class per file, if I remember correctly). Violation of Pertinency: When showing how many different shapes you can draw, adding radio buttons and complex controls with all the possible choices for point shapes is a bad idea. You de-focalize your example code, introducing code for event handling, controls initialization etc., and this is not part the feature you want to demonstrate, they are unnecessary noise in the understanding of the crucial mechanisms providing the feature. Violation of Helpfulness: code containing dubious naming, wrong comments, hacks, and functions longer than one page of code. Violation of Extensibility: badly factored code that have everything into a single function, with potentially swappable entities embedded within the code. Example: if an example reads data from a file and displays it, create a method getData() returning a useful entity, instead of opening the file raw and plotting the stuff. This way, if the user of the library needs to read data from a HTTP server instead, he just has to modify the getData() module and use the example almost as-is. Another violation of Extensibility comes if the example code is not under a fully liberal (e.g. MIT or BSD) license. Violation of Recyclability: when the code layout is so intermingled that is difficult to easily copy and paste parts of it and recycle them into another program. Again, licensing is also a factor. Violation of Easiness: Yes, you are a functional-programming nerd and want to show how cool you are by doing everything on a single line of map, filter and so on, but that could not be helpful to someone else, who is already under pressure to understand your library, and now has to understand your code as well. And in general, the final rule: if it takes more than 10 minutes to do the following: compile the code, run it, read the source, and understand it fully, it means that the example is not a good one. Please let me know your opinion, either positive or negative, or experience on this regard.

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  • Explain the Peak and Flag Algorithm

    - by Isaac Levin
    EDIT Just was pointed that the requirements state peaks cannot be ends of Arrays. So I ran across this site http://codility.com/ Which gives you programming problems and gives you certificates if you can solve them in 2 hours. The very first question is one I have seen before, typically called the Peaks and Flags question. If you are not familiar A non-empty zero-indexed array A consisting of N integers is given. A peak is an array element which is larger than its neighbours. More precisely, it is an index P such that 0 < P < N - 1 and A[P - 1] < A[P] A[P + 1] . For example, the following array A: A[0] = 1 A[1] = 5 A[2] = 3 A[3] = 4 A[4] = 3 A[5] = 4 A[6] = 1 A[7] = 2 A[8] = 3 A[9] = 4 A[10] = 6 A[11] = 2 has exactly four peaks: elements 1, 3, 5 and 10. You are going on a trip to a range of mountains whose relative heights are represented by array A. You have to choose how many flags you should take with you. The goal is to set the maximum number of flags on the peaks, according to certain rules. Flags can only be set on peaks. What's more, if you take K flags, then the distance between any two flags should be greater than or equal to K. The distance between indices P and Q is the absolute value |P - Q|. For example, given the mountain range represented by array A, above, with N = 12, if you take: two flags, you can set them on peaks 1 and 5; three flags, you can set them on peaks 1, 5 and 10; four flags, you can set only three flags, on peaks 1, 5 and 10. You can therefore set a maximum of three flags in this case. Write a function that, given a non-empty zero-indexed array A of N integers, returns the maximum number of flags that can be set on the peaks of the array. For example, given the array above the function should return 3, as explained above. Assume that: N is an integer within the range [1..100,000]; each element of array A is an integer within the range [0..1,000,000,000]. Complexity: expected worst-case time complexity is O(N); expected worst-case space complexity is O(N), beyond input storage (not counting the storage required for input arguments). Elements of input arrays can be modified. So this makes sense, but I failed it using this code public int GetFlags(int[] A) { List<int> peakList = new List<int>(); for (int i = 0; i <= A.Length - 1; i++) { if ((A[i] > A[i + 1] && A[i] > A[i - 1])) { peakList.Add(i); } } List<int> flagList = new List<int>(); int distance = peakList.Count; flagList.Add(peakList[0]); for (int i = 1, j = 0, max = peakList.Count; i < max; i++) { if (Math.Abs(Convert.ToDecimal(peakList[j]) - Convert.ToDecimal(peakList[i])) >= distance) { flagList.Add(peakList[i]); j = i; } } return flagList.Count; } EDIT int[] A = new int[] { 7, 10, 4, 5, 7, 4, 6, 1, 4, 3, 3, 7 }; The correct answer is 3, but my application says 2 This I do not get, since there are 4 peaks (indices 1,4,6,8) and from that, you should be able to place a flag at 2 of the peaks (1 and 6) Am I missing something here? Obviously my assumption is that the beginning or end of an Array can be a peak, is this not the case? If this needs to go in Stack Exchange Programmers, I will move it, but thought dialog here would be helpful. EDIT

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  • OSX Server 3, Mac clients binding to OD and Profile Manager failing

    - by dbf
    I've made a setup containing a Mac Mini with OSX Server 3 (Mavericks 10.9.2) using Open Directory and Profile Manager (Mail, etc all set up and working). Now the thing is, internally on the local network, everything works great. Clients can bind to the OD and the users are able to login. I can install trust and settings profiles (either custom or group profiles) and all services in the profiles mentioned are being configured correctly. I can log in and out, hump around and do it a 100 times on different macs with different users, it works. My goal is to make this service publicly. The domain is with a FQDN which I own, for simplicity let's say server.domain.com. Now the only way for me to bind the clients to the OD is using LDAP mapping RCF2307 (without SSL) and a DN suffix of dc=server,dc=domain,dc=com using the Directory Utility. The options from server, or open directory will throw several errors like Connection failed to node '/LDAPv3/server.domain.com (2100). First of all I don't really understand the problem why clients can't bind to the OD like it does locally, with and without SSL (all ports are open, literally all ports are open, not just 389,636 and 1640, wasn't sure if I was missing any). When the clients are using LDAP mapping RFC2307 to bind (without SSL only), clients are able to authenticate, login and even load the Trust profile. But every Settings profile will fail with a Debug Message: Unable to find GUID in user record OD or fail to install saying missing user identification. Is there any way to get this to work without RFC2307? Because there is quite some stuff missing when using RFC2307 and not pull the mapping from the server or use open directory. Is this setup even possible? Or should I use VPN to authenticate with the OD? The network setup is a Modem/Router (DHCP off) with WAN NATted to an Airport Extreme (Using DHCP+NAT). The AE does notify with a double NAT message but I haven't had any problems with it on any other service. So WAN - 192.168.2.220 (static), AE - 10.0.1.* (dhcp) Output of DIG from the outside using dig server.domain.com ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0 ;; QUESTION SECTION: ;server.domain.com. IN A ;; ANSWER SECTION: server.domain.com. 77 IN A 91.50.*.* (valid WAN IP) ;; SERVER 172.*.*.1#53(172.*.*.1) (iPhone) DIG locally from a client and server (same output) ;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 2, ADDITIONAL: 0 ;; QUESTION SECTION: ;server.domain.com. IN A ;; ANSWER SECTION: server.domain.com. 10800 IN A 10.0.1.11 ;; AUTHORITY SECTION: server.domain.com. 10800 IN NS domain.com. (used for email send in relay) server.domain.com. 10800 IN NS server.domain.com. ;; SERVER 10.0.1.11#53(10.0.1.11) Are there any things I should check? Only have OSX. -- double NAT issue, plugged in the server directly on the Modem/Router with a static IP and issue remains. Guess that rules out the double NAT thing. -- changeip -checkhostname comes with There is nothing to change, e.g. success. Primary address = 10.0.1.11 Current HostName = server.domain.com DNS HostName = server.domain.com For now, I've made a workaround by using an admin account that forces a permanent VPN connection on boot. That means before it comes to the login, a connection is already made or underway. I will continue this post when I have more time, also locating all the necessary .log files of each application involved. I have some suspicions but have to debug a bit more when I have more time on my hands .. Unless, of course, I get sidetracked with having a life. Which is arguably not very likely. krypted.com

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  • Weighted round robins via TTL - possible?

    - by Joe Hopfgartner
    I currently use DNS round robin for load balancing, which works great. The records look like this (I have a ttl of 120 seconds) ;; ANSWER SECTION: orion.2x.to. 116 IN A 80.237.201.41 orion.2x.to. 116 IN A 87.230.54.12 orion.2x.to. 116 IN A 87.230.100.10 orion.2x.to. 116 IN A 87.230.51.65 I learned that not every ISP / device treats such a response the same way. For example some DNS servers rotate the addresses randomly or always cycle them through. Some just propagate the first entry, others try to determine which is best (regionally near) by looking at the ip address. However if the userbase is big enough (spreads over multiple ISPs etc) it balances pretty well. The discrepancies from highest to lowest loaded server hardly every exceeds 15%. However now I have the problem that I am introducing more servers into the systems, that not all have the same capacities. I currently only have 1gbps servers, but I want to work with 100mbit and also 10gbps servers too. So what I want is I want to introduce a server with 10 GBps with a weight of 100, a 1 gbps server with a weight of 10 and a 100 mbit server with a weight of 1. I used to add servers twice to bring more traffic to them (which worked nice. the bandwidth doubled almost.) But adding a 10gbit server 100 times to DNS is a bit rediculous. So I thought about using the TTL. If I give server A 240 seconds ttl and server B only 120 seconds (which is about about the minimum to use for round robin, as a lot of dns servers set to 120 if a lower ttl is specified.. so i have heard) I think something like this should occour in an ideal scenario: first 120 seconds 50% of requests get server A -> keep it for 240 seconds. 50% of requests get server B -> keep it for 120 seconds second 120 seconds 50% of requests still have server A cached -> keep it for another 120 seconds. 25% of requests get server A -> keep it for 240 seconds 25% of requests get server B -> keep it for 120 seconds third 120 seconds 25% will get server A (from the 50% of Server A that now expired) -> cache 240 sec 25% will get server B (from the 50% of Server A that now expired) -> cache 120 sec 25% will have server A cached for another 120 seconds 12.5% will get server B (from the 25% of server B that now expired) -> cache 120sec 12.5% will get server A (from the 25% of server B that now expired) -> cache 240 sec fourth 120 seconds 25% will have server A cached -> cache for another 120 secs 12.5% will get server A (from the 25% of b that now expired) -> cache 240 secs 12.5% will get server B (from the 25% of b that now expired) -> cache 120 secs 12.5% will get server A (from the 25% of a that now expired) -> cache 240 secs 12.5% will get server B (from the 25% of a that now expired) -> cache 120 secs 6.25% will get server A (from the 12.5% of b that now expired) -> cache 240 secs 6.25% will get server B (from the 12.5% of b that now expired) -> cache 120 secs 12.5% will have server A cached -> cache another 120 secs ... i think i lost something at this point but i think you get the idea.... As you can see this gets pretty complicated to predict and it will for sure not work out like this in practice. But it should definitely have an effect on the distribution! I know that weighted round robin exists and is just controlled by the root server. It just cycles through dns records when responding and returns dns records with a set propability that corresponds to the weighting. My DNS server does not support this, and my requirements are not that precise. If it doesnt weight perfectly its okay, but it should go into the right direction. I think using the TTL field could be a more elegant and easier solution - and it deosnt require a dns server that controls this dynamically, which saves resources - which is in my opinion the whole point of dns load balancing vs hardware load balancers. My question now is... are there any best prectices / methos / rules of thumb to weight round robin distribution using the TTL attribute of DNS records? Edit: The system is a forward proxy server system. The amount of Bandwidth (not requests) exceeds what one single server with ethernet can handle. So I need a balancing solution that distributes the bandwidth to several servers. Are there any alternative methods than using DNS? Of course I can use a load balancer with fibre channel etc, but the costs are rediciulous and it also increases only the width of the bottleneck and does not eliminate it. The only thing i can think of are anycast (is it anycast or multicast?) ip addresses, but I don't have the means to set up such a system.

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  • Remote host: can tracert, can telnet, can*not* browse: what gives?

    - by MacThePenguin
    One of my customers of the company I work for has made a change to their Internet connection, and now we can't connect to them any more from our LAN. To help me troubleshoot this issue, the network guy on the customer's site has configured their firewall so that a HTTPS connection to their public IP address is open to any IP. I should put https://<customer's IP> in my browser and get a web page. Well, it works from any network I've tried (even from my smartphone), just not from my company's LAN. I thought it may be an issue with our firewall (though I checked its rules and it allows outbound TCP port 443 to anywhere), so I just connected a PC directly to the network connection of our provider, bypassing out firewall completely, and still it didn't work (everything else worked). So I asked for help to our Internet provider's customer service, and they asked me to do a tracert to our customer's IP. The tracert is successful, as the final hop shown in the output is the host I want to reach. So they said there's no problem. :( I also tried telnet <customer's IP> 443 and that works as well: I get a blank page with the cursor blinking (I've tried using another random port and that gives me an error message, as it should). Still, from any browser of any PC in my LAN I can't open that URL. I tried checking the network traffic with Wireshark: I see the packages going through and answers coming back, thought the packets I see passing are far less than they are if I successfully connect to another HTTPS website. See the attached screenshot: I had to blur the IPs, anyway the longer string is my PC's local IP address, the shorter one is the customer's public IP. I don't know what else to try. This is the only IP doing this... Any idea what could I try to find a solution to this issue? Thanks, let me know if you need further details. Edit: when I say "it doesn't work" I mean: the page doesn't open, the browser keeps loading for a long time and eventually shows an error saying that the page cannot be opened. I'm not in my office now so I can't paste the exact message, but it's the usual message you get when the browser reaches its timeout. When I say "it works", I mean the browser loads and shows a webpage (it's the logon page for the customers' firewall admin interface: so there's the firewall brand's logo and there are fields to enter a user id and a password). Update 13/09/2012: tried again to connect to the customer's network through our Internet connection without a firewall. This is what I did: Run a Kubuntu 12.04 live distro on a spare laptop; Updated all the packages I could and installed WireShark; Attached it to my LAN and verified that I couldn't open https://<customer's IP>. Verified that the Wireshark trace for this attempt was the same as the one I've already posted; Verified that I could connect to another customer's host using rdesktop (it worked); Tried to rdesktop to <customer's IP>, here's the output: kubuntu@kubuntu:/etc$ rdesktop <customer's IP> Autoselected keyboard map en-us ERROR: recv: Connection reset by peer Disconnected the laptop from the LAN; Disconnected the firewall from the Extranet connection, connected the laptop instead. Set its network configuration so that I could access the Internet; Verified that I could connect to other websites in http and https and in RDP to other customers' hosts - it all worked as expected; Verified that I could still traceroute to <customer's IP>: I could; Verified that I still couldn't open https://<customer's IP> (same exact result as before); Checked the WireShark trace for this attempt and noticed a different behaviour: I could see packets going out to the customer's IP, but no replies at all; Tried to run rdesktop again, with a slightly different result: kubuntu@kubuntu:/etc/network$ rdesktop <customer's IP> Autoselected keyboard map en-us ERROR: <customer's IP>: unable to connect Finally gave up, put everything back as it was before, turned off the laptop and lost the WireShark traces I had saved. :( I still remember them very well though. :) Can you get anything out of it? Thank you very much. Update 12/09/2012 n.2: I followed the suggestion by MadHatter in the comments. From inside the firewall, this is what I get: user@ubuntu-mantis:~$ openssl s_client -connect <customer's IP>:443 CONNECTED(00000003) If I now type GET / the output pauses for several seconds and then I get: write:errno=104 I'm going to try the same, but bypassing the firewall, as soon as I can. Thanks. Update 12/09/2012 n.3: So, I think ISA Server is altering the results of my tests... I tried installing Wireshark directly on the firewall and monitoring the packets on the Extranet network card. When the destination is the customer's IP, whatever service I try to connect to (HTTPS, RDP or SAProuter), I can only see outbound packets and no response packets whatsoever from their side. It looks like ISA Server is "faking" the remote server's replies, that's why I get a connection using telnet or the openSSL client. This is the wireshark trace from inside our LAN: But this is the trace on the Extranet network card: This makes a bit more sense... I'll send this info to the customer's tech and see if he can make anything out of it. Thanks to all that took the time to read my question and post suggestions. I'll update this post again.

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  • How can I implement the Gale-Shapley stable marriage algorithm in Perl?

    - by srk
    Problem : We have equal number of men and women.each men has a preference score toward each woman. So do the woman for each man. each of the men and women have certain interests. Based on the interest we calculate the preference scores. So initially we have an input in a file having x columns. First column is the person(men/woman) id. id are nothing but 0.. n numbers.(first half are men and next half woman) the remaining x-1 columns will have the interests. these are integers too. now using this n by x-1 matrix... we have come up with a n by n/2 matrix. the new matrix has all men and woman as their rows and scores for opposite sex in columns. We have to sort the scores in descending order, also we need to know the id of person related to the scores after sorting. So here i wanted to use hash table. once we get the scores we need to make up pairs.. for which we need to follow some rules. My trouble is with the second matrix of n by n/2 that needs to give information of which man/woman has how much preference on a woman/man. I need these scores sorted so that i know who is the first preferred woman/man, 2nd preferred and so on for a man/woman. I hope to get good suggestions on the data structures i use.. I prefer php or perl. Thank you in advance Hey guys this is not an home work. This a little modified version of stable marriage algorithm. I have working solution. I am only working on optimizing my code. more info: It is very similar to stable marriage problem but here we need to calculate the scores based on the interests they share. So i have implemented it as the way you see in the wiki page http://en.wikipedia.org/wiki/Stable_marriage_problem. my problem is not solving the problem. i solved it and can run it. I am just trying to have a better solution. so i am asking suggestions on the type of data structure to use. Conceptually I tried using an array of hashes. where the array index give the person id and the hash in it gives the id's <= score's in sorted manner. I initially start with an array of hashes. now i sort the hashes on values, but i could not store the sorted hashes back in an array.So just stored the keys after sorting and used these to get the values from my initial unsorted hashes. Can we store the hashes after sorting ? Can you suggest a better structure ?

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