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• while(true) and loop-breaking - anti-pattern?

  - by KeithS

  Consider the following code: public void doSomething(int input) { while(true) { TransformInSomeWay(input); if(ProcessingComplete(input)) break; DoSomethingElseTo(input); } } Assume that this process involves a finite but input-dependent number of steps; the loop is designed to terminate on its own as a result of the algorithm, and is not designed to run indefinitely (until cancelled by an outside event). Because the test to see if the loop should end is in the middle of a logical set of steps, the while loop itself currently doesn't check anything meaningful; the check is instead performed at the "proper" place within the conceptual algorithm. I was told that this is bad code, because it is more bug-prone due to the ending condition not being checked by the loop structure. It's more difficult to figure out how you'd exit the loop, and could invite bugs as the breaking condition might be bypassed or omitted accidentally given future changes. Now, the code could be structured as follows: public void doSomething(int input) { TransformInSomeWay(input); while(!ProcessingComplete(input)) { DoSomethingElseTo(input); TransformInSomeWay(input); } } However, this duplicates a call to a method in code, violating DRY; if TransformInSomeWay were later replaced with some other method, both calls would have to be found and changed (and the fact that there are two may be less obvious in a more complex piece of code). You could also write it like: public void doSomething(int input) { var complete = false; while(!complete) { TransformInSomeWay(input); complete = ProcessingComplete(input); if(!complete) { DoSomethingElseTo(input); } } } ... but you now have a variable whose only purpose is to shift the condition-checking to the loop structure, and also has to be checked multiple times to provide the same behavior as the original logic. For my part, I say that given the algorithm this code implements in the real world, the original code is the most readable. If you were going through it yourself, this is the way you'd think about it, and so it would be intuitive to people familiar with the algorithm. So, which is "better"? is it better to give the responsibility of condition checking to the while loop by structuring the logic around the loop? Or is it better to structure the logic in a "natural" way as indicated by requirements or a conceptual description of the algorithm, even though that may mean bypassing the loop's built-in capabilities?

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• Collision detection by sliding against a plane in XNA

  - by Bevin

  Hello, I am attempting to engineer a collision detection algorithm for a custom Minecraft client I'm making. Basically, the entire world is made up of cubes, and the player (or camera) needs to be able to stand on and move against these cubes. The result I want is illustrated in this image: The green line is the player's movement vector. When the player is brushing up against a plane of one of the cubes, I want the vector to change to one that is perpendicular with the plane. The vector should, however, keep all of it's velocity in the plane's direction, yet lose all velocity towards the plane. I hope I've made my question clear. What is the best and most efficient way to implement a collision detection system like this? Also, will a system like this allow for a simple gravity component?

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• Elfsign Object Signing on Solaris

  - by danx

  Elfsign Object Signing on Solaris Don't let this happen to you—use elfsign! Solaris elfsign(1) is a command that signs and verifies ELF format executables. That includes not just executable programs (such as ls or cp), but other ELF format files including libraries (such as libnvpair.so) and kernel modules (such as autofs). Elfsign has been available since Solaris 10 and ELF format files distributed with Solaris, since Solaris 10, are signed by either Sun Microsystems or its successor, Oracle Corporation. When an ELF file is signed, elfsign adds a new section the ELF file, .SUNW_signature, that contains a RSA public key signature and other information about the signer. That is, the algorithm used, algorithm OID, signer CN/OU, and time stamp. The signature section can later be verified by elfsign or other software by matching the signature in the file agains the ELF file contents (excluding the signature). ELF executable files may also be signed by a 3rd-party or by the customer. This is useful for verifying the origin and authenticity of executable files installed on a system. The 3rd-party or customer public key certificate should be installed in /etc/certs/ to allow verification by elfsign. For currently-released versions of Solaris, only cryptographic framework plugin libraries are verified by Solaris. However, all ELF files may be verified by the elfsign command at any time. Elfsign Algorithms Elfsign signatures are created by taking a digest of the ELF section contents, then signing the digest with RSA. To verify, one takes a digest of ELF file and compares with the expected digest that's computed from the signature and RSA public key. Originally elfsign took a MD5 digest of a SHA-1 digest of the ELF file sections, then signed the resulting digest with RSA. In Solaris 11.1 then Solaris 11.1 SRU 7 (5/2013), the elfsign crypto algorithms available have been expanded to keep up with evolving cryptography. The following table shows the available elfsign algorithms: Elfsign Algorithm Solaris Release Comments elfsign sign -F rsa_md5_sha1   S10, S11.0, S11.1 Default for S10. Not recommended* elfsign sign -F rsa_sha1 S11.1 Default for S11.1. Not recommended elfsign sign -F rsa_sha256 S11.1 patch SRU7+   Recommended ___ *Most or all CAs do not accept MD5 CSRs and do not issue MD5 certs due to MD5 hash collision problems. RSA Key Length. I recommend using RSA-2048 key length with elfsign is RSA-2048 as the best balance between a long expected "life time", interoperability, and performance. RSA-2048 keys have an expected lifetime through 2030 (and probably beyond). For details, see Recommendation for Key Management: Part 1: General, NIST Publication SP 800-57 part 1 (rev. 3, 7/2012, PDF), tables 2 and 4 (pp. 64, 67). Step 1: create or obtain a key and cert The first step in using elfsign is to obtain a key and cert from a public Certificate Authority (CA), or create your own self-signed key and cert. I'll briefly explain both methods. Obtaining a Certificate from a CA To obtain a cert from a CA, such as Verisign, Thawte, or Go Daddy (to name a few random examples), you create a private key and a Certificate Signing Request (CSR) file and send it to the CA, following the instructions of the CA on their website. They send back a signed public key certificate. The public key cert, along with the private key you created is used by elfsign to sign an ELF file. The public key cert is distributed with the software and is used by elfsign to verify elfsign signatures in ELF files. You need to request a RSA "Class 3 public key certificate", which is used for servers and software signing. Elfsign uses RSA and we recommend RSA-2048 keys. The private key and CSR can be generated with openssl(1) or pktool(1) on Solaris. Here's a simple example that uses pktool to generate a private RSA_2048 key and a CSR for sending to a CA: $ pktool gencsr keystore=file format=pem outcsr=MYCSR.p10 \ subject="CN=canineswworks.com,OU=Canine SW object signing" \ outkey=MYPRIVATEKEY.key $ openssl rsa -noout -text -in MYPRIVATEKEY.key Private-Key: (2048 bit) modulus: 00:d2:ef:42:f2:0b:8c:96:9f:45:32:fc:fe:54:94: . . . [omitted for brevity] . . . c9:c7 publicExponent: 65537 (0x10001) privateExponent: 26:14:fc:49:26:bc:a3:14:ee:31:5e:6b:ac:69:83: . . . [omitted for brevity] . . . 81 prime1: 00:f6:b7:52:73:bc:26:57:26:c8:11:eb:6c:dc:cb: . . . [omitted for brevity] . . . bc:91:d0:40:d6:9d:ac:b5:69 prime2: 00:da:df:3f:56:b2:18:46:e1:89:5b:6c:f1:1a:41: . . . [omitted for brevity] . . . f3:b7:48:de:c3:d9:ce:af:af exponent1: 00:b9:a2:00:11:02:ed:9a:3f:9c:e4:16:ce:c7:67: . . . [omitted for brevity] . . . 55:50:25:70:d3:ca:b9:ab:99 exponent2: 00:c8:fc:f5:57:11:98:85:8e:9a:ea:1f:f2:8f:df: . . . [omitted for brevity] . . . 23:57:0e:4d:b2:a0:12:d2:f5 coefficient: 2f:60:21:cd:dc:52:76:67:1a:d8:75:3e:7f:b0:64: . . . [omitted for brevity] . . . 06:94:56:d8:9d:5c:8e:9b $ openssl req -noout -text -in MYCSR.p10 Certificate Request: Data: Version: 2 (0x2) Subject: OU=Canine SW object signing, CN=canineswworks.com Subject Public Key Info: Public Key Algorithm: rsaEncryption Public-Key: (2048 bit) Modulus: 00:d2:ef:42:f2:0b:8c:96:9f:45:32:fc:fe:54:94: . . . [omitted for brevity] . . . c9:c7 Exponent: 65537 (0x10001) Attributes: Signature Algorithm: sha1WithRSAEncryption b3:e8:30:5b:88:37:68:1c:26:6b:45:af:5e:de:ea:60:87:ea: . . . [omitted for brevity] . . . 06:f9:ed:b4 Secure storage of RSA private key. The private key needs to be protected if the key signing is used for production (as opposed to just testing). That is, protect the key to protect against unauthorized signatures by others. One method is to use a PIN-protected PKCS#11 keystore. The private key you generate should be stored in a secure manner, such as in a PKCS#11 keystore using pktool(1). Otherwise others can sign your signature. Other secure key storage mechanisms include a SCA-6000 crypto card, a USB thumb drive stored in a locked area, a dedicated server with restricted access, Oracle Key Manager (OKM), or some combination of these. I also recommend secure backup of the private key. Here's an example of generating a private key protected in the PKCS#11 keystore, and a CSR. $ pktool setpin # use if PIN not set yet Enter token passphrase: changeme Create new passphrase: Re-enter new passphrase: Passphrase changed. $ pktool gencsr keystore=pkcs11 label=MYPRIVATEKEY \ format=pem outcsr=MYCSR.p10 \ subject="CN=canineswworks.com,OU=Canine SW object signing" $ pktool list keystore=pkcs11 Enter PIN for Sun Software PKCS#11 softtoken: Found 1 asymmetric public keys. Key #1 - RSA public key: MYPRIVATEKEY Here's another example that uses openssl instead of pktool to generate a private key and CSR: $ openssl genrsa -out cert.key 2048 $ openssl req -new -key cert.key -out MYCSR.p10 Self-Signed Cert You can use openssl or pktool to create a private key and a self-signed public key certificate. A self-signed cert is useful for development, testing, and internal use. The private key created should be stored in a secure manner, as mentioned above. The following example creates a private key, MYSELFSIGNED.key, and a public key cert, MYSELFSIGNED.pem, using pktool and displays the contents with the openssl command. $ pktool gencert keystore=file format=pem serial=0xD06F00D lifetime=20-year \ keytype=rsa hash=sha256 outcert=MYSELFSIGNED.pem outkey=MYSELFSIGNED.key \ subject="O=Canine Software Works, OU=Self-signed CA, CN=canineswworks.com" $ pktool list keystore=file objtype=cert infile=MYSELFSIGNED.pem Found 1 certificates. 1. (X.509 certificate) Filename: MYSELFSIGNED.pem ID: c8:24:59:08:2b:ae:6e:5c:bc:26:bd:ef:0a:9c:54:de:dd:0f:60:46 Subject: O=Canine Software Works, OU=Self-signed CA, CN=canineswworks.com Issuer: O=Canine Software Works, OU=Self-signed CA, CN=canineswworks.com Not Before: Oct 17 23:18:00 2013 GMT Not After: Oct 12 23:18:00 2033 GMT Serial: 0xD06F00D0 Signature Algorithm: sha256WithRSAEncryption $ openssl x509 -noout -text -in MYSELFSIGNED.pem Certificate: Data: Version: 3 (0x2) Serial Number: 3496935632 (0xd06f00d0) Signature Algorithm: sha256WithRSAEncryption Issuer: O=Canine Software Works, OU=Self-signed CA, CN=canineswworks.com Validity Not Before: Oct 17 23:18:00 2013 GMT Not After : Oct 12 23:18:00 2033 GMT Subject: O=Canine Software Works, OU=Self-signed CA, CN=canineswworks.com Subject Public Key Info: Public Key Algorithm: rsaEncryption Public-Key: (2048 bit) Modulus: 00:bb:e8:11:21:d9:4b:88:53:8b:6c:5a:7a:38:8b: . . . [omitted for brevity] . . . bf:77 Exponent: 65537 (0x10001) Signature Algorithm: sha256WithRSAEncryption 9e:39:fe:c8:44:5c:87:2c:8f:f4:24:f6:0c:9a:2f:64:84:d1: . . . [omitted for brevity] . . . 5f:78:8e:e8 $ openssl rsa -noout -text -in MYSELFSIGNED.key Private-Key: (2048 bit) modulus: 00:bb:e8:11:21:d9:4b:88:53:8b:6c:5a:7a:38:8b: . . . [omitted for brevity] . . . bf:77 publicExponent: 65537 (0x10001) privateExponent: 0a:06:0f:23:e7:1b:88:62:2c:85:d3:2d:c1:e6:6e: . . . [omitted for brevity] . . . 9c:e1:e0:0a:52:77:29:4a:75:aa:02:d8:af:53:24: c1 prime1: 00:ea:12:02:bb:5a:0f:5a:d8:a9:95:b2:ba:30:15: . . . [omitted for brevity] . . . 5b:ca:9c:7c:19:48:77:1e:5d prime2: 00:cd:82:da:84:71:1d:18:52:cb:c6:4d:74:14:be: . . . [omitted for brevity] . . . 5f:db:d5:5e:47:89:a7:ef:e3 exponent1: 32:37:62:f6:a6:bf:9c:91:d6:f0:12:c3:f7:04:e9: . . . [omitted for brevity] . . . 97:3e:33:31:89:66:64:d1 exponent2: 00:88:a2:e8:90:47:f8:75:34:8f:41:50:3b:ce:93: . . . [omitted for brevity] . . . ff:74:d4:be:f3:47:45:bd:cb coefficient: 4d:7c:09:4c:34:73:c4:26:f0:58:f5:e1:45:3c:af: . . . [omitted for brevity] . . . af:01:5f:af:ad:6a:09:bf Step 2: Sign the ELF File object By now you should have your private key, and obtained, by hook or crook, a cert (either from a CA or use one you created (a self-signed cert). The next step is to sign one or more objects with your private key and cert. Here's a simple example that creates an object file, signs, verifies, and lists the contents of the ELF signature. $ echo '#include <stdio.h>\nint main(){printf("Hello\\n");}'>hello.c $ make hello cc -o hello hello.c $ elfsign verify -v -c MYSELFSIGNED.pem -e hello elfsign: no signature found in hello. $ elfsign sign -F rsa_sha256 -v -k MYSELFSIGNED.key -c MYSELFSIGNED.pem -e hello elfsign: hello signed successfully. format: rsa_sha256. signer: O=Canine Software Works, OU=Self-signed CA, CN=canineswworks.com. signed on: October 17, 2013 04:22:49 PM PDT. $ elfsign list -f format -e hello rsa_sha256 $ elfsign list -f signer -e hello O=Canine Software Works, OU=Self-signed CA, CN=canineswworks.com $ elfsign list -f time -e hello October 17, 2013 04:22:49 PM PDT $ elfsign verify -v -c MYSELFSIGNED.key -e hello elfsign: verification of hello failed. format: rsa_sha256. signer: O=Canine Software Works, OU=Self-signed CA, CN=canineswworks.com. signed on: October 17, 2013 04:22:49 PM PDT. Signing using the pkcs11 keystore To sign the ELF file using a private key in the secure pkcs11 keystore, replace "-K MYSELFSIGNED.key" in the "elfsign sign" command line with "-T MYPRIVATEKEY", where MYPRIVATKEY is the pkcs11 token label. Step 3: Install the cert and test on another system Just signing the object isn't enough. You need to copy or install the cert and the signed ELF file(s) on another system to test that the signature is OK. Your public key cert should be installed in /etc/certs. Use elfsign verify to verify the signature. Elfsign verify checks each cert in /etc/certs until it finds one that matches the elfsign signature in the file. If one isn't found, the verification fails. Here's an example: $ su Password: # rm /etc/certs/MYSELFSIGNED.key # cp MYSELFSIGNED.pem /etc/certs # exit $ elfsign verify -v hello elfsign: verification of hello passed. format: rsa_sha256. signer: O=Canine Software Works, OU=Self-signed CA, CN=canineswworks.com. signed on: October 17, 2013 04:24:20 PM PDT. After testing, package your cert along with your ELF object to allow elfsign verification after your cert and object are installed or copied. Under the Hood: elfsign verification Here's the steps taken to verify a ELF file signed with elfsign. The steps to sign the file are similar except the private key exponent is used instead of the public key exponent and the .SUNW_signature section is written to the ELF file instead of being read from the file. Generate a digest (SHA-256) of the ELF file sections. This digest uses all ELF sections loaded in memory, but excludes the ELF header, the .SUNW_signature section, and the symbol table Extract the RSA signature (RSA-2048) from the .SUNW_signature section Extract the RSA public key modulus and public key exponent (65537) from the public key cert Calculate the expected digest as follows:     signaturepublicKeyExponent % publicKeyModulus Strip the PKCS#1 padding (most significant bytes) from the above. The padding is 0x00, 0x01, 0xff, 0xff, . . ., 0xff, 0x00. If the actual digest == expected digest, the ELF file is verified (OK). Further Information elfsign(1), pktool(1), and openssl(1) man pages. "Signed Solaris 10 Binaries?" blog by Darren Moffat (2005) shows how to use elfsign. "Simple CLI based CA on Solaris" blog by Darren Moffat (2008) shows how to set up a simple CA for use with self-signed certificates. "How to Create a Certificate by Using the pktool gencert Command" System Administration Guide: Security Services (available at docs.oracle.com)

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• Setting up a VPN connection to Amazon VPC - routing

  - by Keeno

  I am having some real issues setting up a VPN between out office and AWS VPC. The "tunnels" appear to be up, however I don't know if they are configured correctly. The device I am using is a Netgear VPN Firewall - FVS336GV2 If you see in the attached config downloaded from VPC (#3 Tunnel Interface Configuration), it gives me some "inside" addresses for the tunnel. When setting up the IPsec tunnels do I use the inside tunnel IP's (e.g. 169.254.254.2/30) or do I use my internal network subnet (10.1.1.0/24) I have tried both, when I tried the local network (10.1.1.x) the tracert stops at the router. When I tried with the "inside" ips, the tracert to the amazon VPC (10.0.0.x) goes out over the internet. this all leads me to the next question, for this router, how do I set up stage #4, the static next hop? What are these seemingly random "inside" addresses and where did amazon generate them from? 169.254.254.x seems odd? With a device like this, is the VPN behind the firewall? I have tweaked any IP addresses below so that they are not "real". I am fully aware, this is probably badly worded. Please if there is any further info/screenshots that will help, let me know. Amazon Web Services Virtual Private Cloud IPSec Tunnel #1 ================================================================================ #1: Internet Key Exchange Configuration Configure the IKE SA as follows - Authentication Method : Pre-Shared Key - Pre-Shared Key : --- - Authentication Algorithm : sha1 - Encryption Algorithm : aes-128-cbc - Lifetime : 28800 seconds - Phase 1 Negotiation Mode : main - Perfect Forward Secrecy : Diffie-Hellman Group 2 #2: IPSec Configuration Configure the IPSec SA as follows: - Protocol : esp - Authentication Algorithm : hmac-sha1-96 - Encryption Algorithm : aes-128-cbc - Lifetime : 3600 seconds - Mode : tunnel - Perfect Forward Secrecy : Diffie-Hellman Group 2 IPSec Dead Peer Detection (DPD) will be enabled on the AWS Endpoint. We recommend configuring DPD on your endpoint as follows: - DPD Interval : 10 - DPD Retries : 3 IPSec ESP (Encapsulating Security Payload) inserts additional headers to transmit packets. These headers require additional space, which reduces the amount of space available to transmit application data. To limit the impact of this behavior, we recommend the following configuration on your Customer Gateway: - TCP MSS Adjustment : 1387 bytes - Clear Don't Fragment Bit : enabled - Fragmentation : Before encryption #3: Tunnel Interface Configuration Your Customer Gateway must be configured with a tunnel interface that is associated with the IPSec tunnel. All traffic transmitted to the tunnel interface is encrypted and transmitted to the Virtual Private Gateway. The Customer Gateway and Virtual Private Gateway each have two addresses that relate to this IPSec tunnel. Each contains an outside address, upon which encrypted traffic is exchanged. Each also contain an inside address associated with the tunnel interface. The Customer Gateway outside IP address was provided when the Customer Gateway was created. Changing the IP address requires the creation of a new Customer Gateway. The Customer Gateway inside IP address should be configured on your tunnel interface. Outside IP Addresses: - Customer Gateway : 217.33.22.33 - Virtual Private Gateway : 87.222.33.42 Inside IP Addresses - Customer Gateway : 169.254.254.2/30 - Virtual Private Gateway : 169.254.254.1/30 Configure your tunnel to fragment at the optimal size: - Tunnel interface MTU : 1436 bytes #4: Static Routing Configuration: To route traffic between your internal network and your VPC, you will need a static route added to your router. Static Route Configuration Options: - Next hop : 169.254.254.1 You should add static routes towards your internal network on the VGW. The VGW will then send traffic towards your internal network over the tunnels. IPSec Tunnel #2 ================================================================================ #1: Internet Key Exchange Configuration Configure the IKE SA as follows - Authentication Method : Pre-Shared Key - Pre-Shared Key : --- - Authentication Algorithm : sha1 - Encryption Algorithm : aes-128-cbc - Lifetime : 28800 seconds - Phase 1 Negotiation Mode : main - Perfect Forward Secrecy : Diffie-Hellman Group 2 #2: IPSec Configuration Configure the IPSec SA as follows: - Protocol : esp - Authentication Algorithm : hmac-sha1-96 - Encryption Algorithm : aes-128-cbc - Lifetime : 3600 seconds - Mode : tunnel - Perfect Forward Secrecy : Diffie-Hellman Group 2 IPSec Dead Peer Detection (DPD) will be enabled on the AWS Endpoint. We recommend configuring DPD on your endpoint as follows: - DPD Interval : 10 - DPD Retries : 3 IPSec ESP (Encapsulating Security Payload) inserts additional headers to transmit packets. These headers require additional space, which reduces the amount of space available to transmit application data. To limit the impact of this behavior, we recommend the following configuration on your Customer Gateway: - TCP MSS Adjustment : 1387 bytes - Clear Don't Fragment Bit : enabled - Fragmentation : Before encryption #3: Tunnel Interface Configuration Outside IP Addresses: - Customer Gateway : 217.33.22.33 - Virtual Private Gateway : 87.222.33.46 Inside IP Addresses - Customer Gateway : 169.254.254.6/30 - Virtual Private Gateway : 169.254.254.5/30 Configure your tunnel to fragment at the optimal size: - Tunnel interface MTU : 1436 bytes #4: Static Routing Configuration: Static Route Configuration Options: - Next hop : 169.254.254.5 You should add static routes towards your internal network on the VGW. The VGW will then send traffic towards your internal network over the tunnels. EDIT #1 After writing this post, I continued to fiddle and something started to work, just not very reliably. The local IPs to use when setting up the tunnels where indeed my network subnets. Which further confuses me over what these "inside" IP addresses are for. The problem is, results are not consistent what so ever. I can "sometimes" ping, I can "sometimes" RDP using the VPN. Sometimes, Tunnel 1 or Tunnel 2 can be up or down. When I came back into work today, Tunnel 1 was down, so I deleted it and re-created it from scratch. Now I cant ping anything, but Amazon AND the router are telling me tunnel 1/2 are fine. I guess the router/vpn hardware I have just isnt up to the job..... EDIT #2 Now Tunnel 1 is up, Tunnel 2 is down (I didn't change any settings) and I can ping/rdp again. EDIT #3 Screenshot of route table that the router has built up. Current state (tunnel 1 still up and going string, 2 is still down and wont re-connect)

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• Puppet's automatically generated certificates failing

  - by gparent

  I am running a default configuration of Puppet on Debian Squeeze 6.0.4. The server's FQDN is master.example.com. The client's FQDN is client.example.com. I am able to contact the puppet master and send a CSR. I sign it using puppetca -sa but the client will still not connect. Date of both machines is within 2 seconds of Tue Apr 3 20:59:00 UTC 2012 as I wrote this sentence. This is what appears in /var/log/syslog: Apr 3 17:03:52 localhost puppet-agent[18653]: Reopening log files Apr 3 17:03:52 localhost puppet-agent[18653]: Starting Puppet client version 2.6.2 Apr 3 17:03:53 localhost puppet-agent[18653]: Could not retrieve catalog from remote server: SSL_connect returned=1 errno=0 state=SSLv3 read server certificate B: certificate verify failed Apr 3 17:03:53 localhost puppet-agent[18653]: Using cached catalog Apr 3 17:03:53 localhost puppet-agent[18653]: Could not retrieve catalog; skipping run Here is some interesting output: OpenSSL client test: client:~# openssl s_client -host master.example.com -port 8140 -cert /var/lib/puppet/ssl/certs/client.example.com.pem -key /var/lib/puppet/ssl/private_keys/client.example.com.pem -CAfile /var/lib/puppet/ssl/certs/ca.pem CONNECTED(00000003) depth=1 /CN=Puppet CA: master.example.com verify return:1 depth=0 /CN=master.example.com verify error:num=7:certificate signature failure verify return:1 depth=0 /CN=master.example.com verify return:1 18509:error:1409441B:SSL routines:SSL3_READ_BYTES:tlsv1 alert decrypt error:s3_pkt.c:1102:SSL alert number 51 18509:error:140790E5:SSL routines:SSL23_WRITE:ssl handshake failure:s23_lib.c:188: client:~# master's certificate: root@master:/etc/puppet# openssl x509 -text -noout -in /etc/puppet/ssl/certs/master.example.com.pem Certificate: Data: Version: 3 (0x2) Serial Number: 2 (0x2) Signature Algorithm: sha1WithRSAEncryption Issuer: CN=Puppet CA: master.example.com Validity Not Before: Apr 2 20:01:28 2012 GMT Not After : Apr 2 20:01:28 2017 GMT Subject: CN=master.example.com Subject Public Key Info: Public Key Algorithm: rsaEncryption RSA Public Key: (1024 bit) Modulus (1024 bit): 00:a9:c1:f9:4c:cd:0f:68:84:7b:f4:93:16:20:44: 7a:2b:05:8e:57:31:05:8e:9c:c8:08:68:73:71:39: c1:86:6a:59:93:6e:53:aa:43:11:83:5b:2d:8c:7d: 54:05:65:c1:e1:0e:94:4a:f0:86:58:c3:3d:4f:f3: 7d:bd:8e:29:58:a6:36:f4:3e:b2:61:ec:53:b5:38: 8e:84:ac:5f:a3:e3:8c:39:bd:cf:4f:3c:ff:a9:65: 09:66:3c:ba:10:14:69:d5:07:57:06:28:02:37:be: 03:82:fb:90:8b:7d:b3:a5:33:7b:9b:3a:42:51:12: b3:ac:dd:d5:58:69:a9:8a:ed Exponent: 65537 (0x10001) X509v3 extensions: X509v3 Basic Constraints: critical CA:FALSE Netscape Comment: Puppet Ruby/OpenSSL Internal Certificate X509v3 Key Usage: critical Digital Signature, Key Encipherment X509v3 Subject Key Identifier: 8C:2F:14:84:B6:A1:B5:0C:11:52:36:AB:E5:3F:F2:B9:B3:25:F3:1C X509v3 Extended Key Usage: critical TLS Web Server Authentication, TLS Web Client Authentication Signature Algorithm: sha1WithRSAEncryption 7b:2c:4f:c2:76:38:ab:03:7f:c6:54:d9:78:1d:ab:6c:45:ab: 47:02:c7:fd:45:4e:ab:b5:b6:d9:a7:df:44:72:55:0c:a5:d0: 86:58:14:ae:5f:6f:ea:87:4d:78:e4:39:4d:20:7e:3d:6d:e9: e2:5e:d7:c9:3c:27:43:a4:29:44:85:a1:63:df:2f:55:a9:6a: 72:46:d8:fb:c7:cc:ca:43:e7:e1:2c:fe:55:2a:0d:17:76:d4: e5:49:8b:85:9f:fa:0e:f6:cc:e8:28:3e:8b:47:b0:e1:02:f0: 3d:73:3e:99:65:3b:91:32:c5:ce:e4:86:21:b2:e0:b4:15:b5: 22:63 root@master:/etc/puppet# CA's certificate: root@master:/etc/puppet# openssl x509 -text -noout -in /etc/puppet/ssl/certs/ca.pem Certificate: Data: Version: 3 (0x2) Serial Number: 1 (0x1) Signature Algorithm: sha1WithRSAEncryption Issuer: CN=Puppet CA: master.example.com Validity Not Before: Apr 2 20:01:05 2012 GMT Not After : Apr 2 20:01:05 2017 GMT Subject: CN=Puppet CA: master.example.com Subject Public Key Info: Public Key Algorithm: rsaEncryption RSA Public Key: (1024 bit) Modulus (1024 bit): 00:b5:2c:3e:26:a3:ae:43:b8:ed:1e:ef:4d:a1:1e: 82:77:78:c2:98:3f:e2:e0:05:57:f0:8d:80:09:36: 62:be:6c:1a:21:43:59:1d:e9:b9:4d:e0:9c:fa:09: aa:12:a1:82:58:fc:47:31:ed:ad:ad:73:01:26:97: ef:d2:d6:41:6b:85:3b:af:70:00:b9:63:e9:1b:c3: ce:57:6d:95:0e:a6:d2:64:bd:1f:2c:1f:5c:26:8e: 02:fd:d3:28:9e:e9:8f:bc:46:bb:dd:25:db:39:57: 81:ed:e5:c8:1f:3d:ca:39:cf:e7:f3:63:75:f6:15: 1f:d4:71:56:ed:84:50:fb:5d Exponent: 65537 (0x10001) X509v3 extensions: X509v3 Basic Constraints: critical CA:TRUE Netscape Comment: Puppet Ruby/OpenSSL Internal Certificate X509v3 Key Usage: critical Certificate Sign, CRL Sign X509v3 Subject Key Identifier: 8C:2F:14:84:B6:A1:B5:0C:11:52:36:AB:E5:3F:F2:B9:B3:25:F3:1C Signature Algorithm: sha1WithRSAEncryption 1d:cd:c6:65:32:42:a5:01:62:46:87:10:da:74:7e:8b:c8:c9: 86:32:9e:c2:2e:c1:fd:00:79:f0:ef:d8:73:dd:7e:1b:1a:3f: cc:64:da:a3:38:ad:49:4e:c8:4d:e3:09:ba:bc:66:f2:6f:63: 9a:48:19:2d:27:5b:1d:2a:69:bf:4f:f4:e0:67:5e:66:84:30: e5:85:f4:49:6e:d0:92:ae:66:77:50:cf:45:c0:29:b2:64:87: 12:09:d3:10:4d:91:b6:f3:63:c4:26:b3:fa:94:2b:96:18:1f: 9b:a9:53:74:de:9c:73:a4:3a:8d:bf:fa:9c:c0:42:9d:78:49: 4d:70 root@master:/etc/puppet# Client's certificate: client:~# openssl x509 -text -noout -in /var/lib/puppet/ssl/certs/client.example.com.pem Certificate: Data: Version: 3 (0x2) Serial Number: 3 (0x3) Signature Algorithm: sha1WithRSAEncryption Issuer: CN=Puppet CA: master.example.com Validity Not Before: Apr 2 20:01:36 2012 GMT Not After : Apr 2 20:01:36 2017 GMT Subject: CN=client.example.com Subject Public Key Info: Public Key Algorithm: rsaEncryption RSA Public Key: (1024 bit) Modulus (1024 bit): 00:ae:88:6d:9b:e3:b1:fc:47:07:d6:bf:ea:53:d1: 14:14:9b:35:e6:70:43:e0:58:35:76:ac:c5:9d:86: 02:fd:77:28:fc:93:34:65:9d:dd:0b:ea:21:14:4d: 8a:95:2e:28:c9:a5:8d:a2:2c:0e:1c:a0:4c:fa:03: e5:aa:d3:97:98:05:59:3c:82:a9:7c:0e:e9:df:fd: 48:81:dc:33:dc:88:e9:09:e4:19:d6:e4:7b:92:33: 31:73:e4:f2:9c:42:75:b2:e1:9f:d9:49:8c:a7:eb: fa:7d:cb:62:22:90:1c:37:3a:40:95:a7:a0:3b:ad: 8e:12:7c:6e:ad:04:94:ed:47 Exponent: 65537 (0x10001) X509v3 extensions: X509v3 Basic Constraints: critical CA:FALSE Netscape Comment: Puppet Ruby/OpenSSL Internal Certificate X509v3 Key Usage: critical Digital Signature, Key Encipherment X509v3 Subject Key Identifier: 8C:2F:14:84:B6:A1:B5:0C:11:52:36:AB:E5:3F:F2:B9:B3:25:F3:1C X509v3 Extended Key Usage: critical TLS Web Server Authentication, TLS Web Client Authentication Signature Algorithm: sha1WithRSAEncryption 33:1f:ec:3c:91:5a:eb:c6:03:5f:a1:58:60:c3:41:ed:1f:fe: cb:b2:40:11:63:4d:ba:18:8a:8b:62:ba:ab:61:f5:a0:6c:0e: 8a:20:56:7b:10:a1:f9:1d:51:49:af:70:3a:05:f9:27:4a:25: d4:e6:88:26:f7:26:e0:20:30:2a:20:1d:c4:d3:26:f1:99:cf: 47:2e:73:90:bd:9c:88:bf:67:9e:dd:7c:0e:3a:86:6b:0b:8d: 39:0f:db:66:c0:b6:20:c3:34:84:0e:d8:3b:fc:1c:a8:6c:6c: b1:19:76:65:e6:22:3c:bf:ff:1c:74:bb:62:a0:46:02:95:fa: 83:41 client:~#

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• Depth interpolation for z-buffer, with scanline

  - by Twodordan

  I have to write my own software 3d rasterizer, and so far I am able to project my 3d model made of triangles into 2d space: I rotate, translate and project my points to get a 2d space representation of each triangle. Then, I take the 3 triangle points and I implement the scanline algorithm (using linear interpolation) to find all points[x][y] along the edges(left and right) of the triangles, so that I can scan the triangle horizontally, row by row, and fill it with pixels. This works. Except I have to also implement z-buffering. This means that knowing the rotated&translated z coordinates of the 3 vertices of the triangle, I must interpolate the z coordinate for all other points I find with my scanline algorithm. The concept seems clear enough, I first find Za and Zb with these calculations: var Z_Slope = (bottom_point_z - top_point_z) / (bottom_point_y - top_point_y); var Za = top_point_z + ((current_point_y - top_point_y) * Z_Slope); Then for each Zp I do the same interpolation horizontally: var Z_Slope = (right_z - left_z) / (right_x - left_x); var Zp = left_z + ((current_point_x - left_x) * Z_Slope); And of course I add to the zBuffer, if current z is closer to the viewer than the previous value at that index. (my coordinate system is x: left - right; y: top - bottom; z: your face - computer screen;) The problem is, it goes haywire. The project is here and if you select the "Z-Buffered" radio button, you'll see the results... (note that the rest of the options before "Z-Buffered" use the Painter's algorithm to correctly order the triangles. I also use the painter's algorithm -only- to draw the wireframe in "Z-Buffered" mode for debugging purposes) PS: I've read here that you must turn the z's into their reciprocals (meaning z = 1/z) before you interpolate. I tried that, and it appears that there's no change. What am I missing? (could anyone clarify, precisely where you must turn z into 1/z and where to turn it back?)

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• Do I need path finding to make AI avoid obstacles?

  - by yannicuLar

  How do you know when a path-finding algorithm is really needed? There are contexts, where you just want to improve AI navigation to avoid an object, like a space -ship that won't crash on a planet or a car that already knows where to steer, but needs small corrections to avoid a road bump. As I've seen on similar posts, the obvious solution is to implement some path-finding algorithm, most likely like A*, and let your AI-controlled object to navigate through the path. Now, I have the necessary skills to implement a path-finding algorithm, and I'm not being lazy here, but I'm still a bit skeptical on if this is really needed. I have the impression that path-finding is appropriate to navigate through a maze, or picking a path when there are many alternatives. But in obstacle avoidance, when you do know the path, but need to make slight corrections, is path finding really necessary? Even when the obstacles are too sparse or small ? I mean, in real life, when you're driving and notice a bump on the road, you will just have to pick between steering a bit on the left (and have the bump on your right side) or the other way around. You will not consider stopping, or going backwards. A path finding would be appropriate when you need to pick a route through the city, right ? So, are there any other methods to help AI navigation, except path-finding? And if there are, how do you know when path-fining is the appropriate algorithm ? Thanks for any thoughts

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• A Cautionary Tale About Multi-Source JNDI Configuration

  - by scott.s.nelson(at)oracle.com

  Here's a bit of fun with WebLogic JDBC configurations.  I ran into this issue after reading that p13nDataSource and cgDataSource-NonXA should not be configured as multi-source. There were some issues changing them to use the basic JDBC connection string and when rolling back to the bad configuration the server went "Boom".  Since one purpose behind this blog is to share lessons learned, I just had to post this. If you write your descriptors manually (as opposed to generating them using the WLS console) and put a comma-separated list of JNDI addresses like this: <jdbc-data-source-params> <jndi-name>weblogic.jdbc.jts.commercePool,contentDataSource, contentVersioningDataSource,portalFrameworkPool</jndi-name> <algorithm-type>Load-Balancing</algorithm-type> <data-source-list>portalDataSource-rac0,portalDataSource-rac1</data-source-list> <failover-request-if-busy>false</failover-request-if-busy> </jdbc-data-source-params> so long as the first address resolves, it will still work. Sort of.  If you call this connection to do an update, only one node of the RAC instance is updated. Other wonderful side-effects include the server refusing to start sometimes. The proper way to list the JNDI sources is one per node, like this: <jdbc-data-source-params> <jndi-name>weblogic.jdbc.jts.commercePool</jndi-name> <jndi-name>contentDataSource</jndi-name> <jndi-name>contentVersioningDataSource</jndi-name> <jndi-name>portalFrameworkPool</jndi-name> <algorithm-type>Load-Balancing</algorithm-type> <data-source-list>portalDataSource-rac0, portalDataSource-rac1, portalDataSource-rac2 </data-source-list> <failover-request-if-busy>false</failover-request-if-busy> </jdbc-data-source-params>(Props to Sandeep Seshan for locating the root cause)

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• A new mission statement for my school's algorithms class

  - by Eric Fode

  The teacher at Eastern Washington University that is now teaching the algorithms course is new to eastern and as a result the course has changed drastically mostly in the right direction. That being said I feel that the class could use a more specific, and industry oriented (since that is where most students will go, though suggestions for an academia oriented class are also welcome) direction, having only worked in industry for 2 years I would like the community's (a wider and much more collectively experienced and in the end plausibly more credible) opinion on the quality of this as a statement for the purpose an algorithms class, and if I am completely off target your suggestion for the purpose of a required Jr. level Algorithms class that is standalone (so no other classes focusing specifically on algorithms are required). The statement is as follows: The purpose of the algorithms class is to do three things: Primarily, to teach how to learn, do basic analysis, and implement a given algorithm found outside of the class. Secondly, to teach the student how to model a problem in their mind so that they can find a an existing algorithm or have a direction to start the development of a new algorithm. Third, to overview a variety of algorithms that exist and to deeply understand and analyze one algorithm in each of the basic algorithmic design strategies: Divide and Conquer, Reduce and Conquer, Transform and Conquer, Greedy, Brute Force, Iterative Improvement and Dynamic Programming. The Question in short is: do you agree with this statement of the purpose of an algorithms course, so that it would be useful in the real world, if not what would you suggest?

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• Find points whose pairwise distances approximate a given distance matrix

  - by Stephan Kolassa

  Problem. I have a symmetric distance matrix with entries between zero and one, like this one: D = ( 0.0 0.4 0.0 0.5 ) ( 0.4 0.0 0.2 1.0 ) ( 0.0 0.2 0.0 0.7 ) ( 0.5 1.0 0.7 0.0 ) I would like to find points in the plane that have (approximately) the pairwise distances given in D. I understand that this will usually not be possible with strictly correct distances, so I would be happy with a "good" approximation. My matrices are smallish, no more than 10x10, so performance is not an issue. Question. Does anyone know of an algorithm to do this? Background. I have sets of probability densities between which I calculate Hellinger distances, which I would like to visualize as above. Each set contains no more than 10 densities (see above), but I have a couple of hundred sets. What I did so far. I did consider posting at math.SE, but looking at what gets tagged as "geometry" there, it seems like this kind of computational geometry question would be more on-topic here. If the community thinks this should be migrated, please go ahead. This looks like a straightforward problem in computational geometry, and I would assume that anyone involved in clustering might be interested in such a visualization, but I haven't been able to google anything. One simple approach would be to randomly plonk down points and perturb them until the distance matrix is close to D, e.g., using Simulated Annealing, or run a Genetic Algorithm. I have to admit that I haven't tried that yet, hoping for a smarter way. One specific operationalization of a "good" approximation in the sense above is Problem 4 in the Open Problems section here, with k=2. Now, while finding an algorithm that is guaranteed to find the minimum l1-distance between D and the resulting distance matrix may be an open question, it still seems possible that there at least is some approximation to this optimal solution. If I don't get an answer here, I'll mail the gentleman who posed that problem and ask whether he knows of any approximation algorithm (and post any answer I get to that here).

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• Draw multiple objects with textures

  - by Simplex

  I want to draw cubes using textures. void OperateWithMainMatrix(ESContext* esContext, GLfloat offsetX, GLfloat offsetY, GLfloat offsetZ) { UserData *userData = (UserData*) esContext->userData; ESMatrix modelview; ESMatrix perspective; //Manipulation with matrix ... glVertexAttribPointer(userData->positionLoc, 3, GL_FLOAT, GL_FALSE, 0, cubeFaces); //in cubeFaces coordinates verticles cube glVertexAttribPointer(userData->normalLoc, 3, GL_FLOAT, GL_FALSE, 0, cubeFaces); //for normals (use in fragment shaider for textures) glEnableVertexAttribArray(userData->positionLoc); glEnableVertexAttribArray(userData->normalLoc); // Load the MVP matrix glUniformMatrix4fv(userData->mvpLoc, 1, GL_FALSE, (GLfloat*)&userData->mvpMatrix.m[0][0]); //Bind base map glActiveTexture(GL_TEXTURE0); glBindTexture(GL_TEXTURE_CUBE_MAP, userData->baseMapTexId); //Set the base map sampler to texture unit to 0 glUniform1i(userData->baseMapLoc, 0); // Draw the cube glDrawArrays(GL_TRIANGLES, 0, 36); } (coordinates transformation is in OperateWithMainMatrix() ) Then Draw() function is called: void Draw(ESContext *esContext) { UserData *userData = esContext->userData; // Set the viewport glViewport(0, 0, esContext->width, esContext->height); // Clear the color buffer glClear(GL_COLOR_BUFFER_BIT); // Use the program object glUseProgram(userData->programObject); OperateWithMainMatrix(esContext, 0.0f, 0.0f, 0.0f); eglSwapBuffers(esContext->eglDisplay, esContext->eglSurface); } This work fine, but if I try to draw multiple cubes (next code for example): void Draw(ESContext *esContext) { ... // Use the program object glUseProgram(userData->programObject); OperateWithMainMatrix(esContext, 2.0f, 0.0f, 0.0f); OperateWithMainMatrix(esContext, 1.0f, 0.0f, 0.0f); OperateWithMainMatrix(esContext, 0.0f, 0.0f, 0.0f); OperateWithMainMatrix(esContext, -1.0f, 0.0f, 0.0f); OperateWithMainMatrix(esContext, -2.0f, 0.0f, 0.0f); eglSwapBuffers(esContext->eglDisplay, esContext->eglSurface); } A side faces overlapes frontal face. The side face of the right cube overlaps frontal face of the center cube. How can i remove this effect and display miltiple cubes without it?

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• Should I always be checking every neighbor when building voxel meshes?

  - by Raven Dreamer

  I've been playing around with Unity3d, seeing if I can make a voxel-based engine out of it (a la Castle Story, or Minecraft). I've dynamically built a mesh from a volume of cubes, and now I'm looking into reducing the number of vertices built into each mesh, as right now, I'm "rendering" vertices and triangles for cubes that are fully hidden within the larger voxel volume. The simple solution is to check each of the 6 directions for each cube, and only add the face to the mesh if the neighboring voxel in that direction is "empty". Parsing a voxel volume is BigO(N^3), and checking the 6 neighbors keeps it BigO(7*N^3)-BigO(N^3). The one thing this results in is a lot of redundant calls, as the same voxel will be polled up to 7 times, just to build the mesh. My question, then, is: Is there a way to parse a cubic volume (and find which faces have neighbors) with fewer redundant calls? And perhaps more importantly, does it matter (as BigO complexity is the same in both cases)?

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• Hardware instancing for voxel engine

  - by Menno Gouw

  i just did the tutorial on Hardware Instancing from this source: http://www.float4x4.net/index.php/2011/07/hardware-instancing-for-pc-in-xna-4-with-textures/. Somewhere between 900.000 and 1.000.000 draw calls for the cube i get this error "XNA Framework HiDef profile supports a maximum VertexBuffer size of 67108863." while still running smoothly on 900k. That is slightly less then 100x100x100 which are a exactly a million. Now i have seen voxel engines with very "tiny" voxels, you easily get to 1.000.000 cubes in view with rough terrain and a decent far plane. Obviously i can optimize a lot in the geometry buffer method, like rendering only visible faces of a cube or using larger faces covering multiple cubes if the area is flat. But is a vertex buffer of roughly 67mb the max i can work with or can i create multiple?

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• Set vertex position

  - by user1806687

  Can anyone tell me how to set the positions of model vertices? I want to be able to change the position of some of the vertices of a Model. Is there any way to make that happen? And make the changed visible at that moment. EDIT: Well, the thing is,I have a model, a cube, that is made up of four "thin" cubes(top,bottom,left side, right side), so I get this cube with "hole" in the middle. And I want to scale it on Y axis. If I do Scale(0,2,0) it will scale the whole object meaning, it will double the Y size of left and right side, but also double the size of the top and bottom cube, which I do not want. Same for X axis I want to double the size of top and bottom cubes but not the left and right one. Hope you can help

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• Why doesn't light continuous on my model?

  - by nosferat

  I created a basic textured cube model with Blender to practice modeling, and then I imported it into Unity. After I put up some lighting it looks pretty ugly. The light is not continuous on a row of textured cubes: What is more odd, the light on the blocks that makes up the floor is continuous. What am I doing wrong? UPDATE This is how it looks like without textures: https://dl.dropbox.com/u/45620018/without%20textures.PNG If I would not know that these are perfect cubes, I'd say there is a slight curve on surface. I also tried lightening the texture but it also didn't help: https://dl.dropbox.com/u/45620018/lighter%20texture.PNG I just simply exported the model from Blender and did not set up any normals or things like that. However I also did not do any special woth the floor brick model.

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• Octrees as data structure

  - by Christian Frantz

  In my cube world, I want to use octrees to represent my chunks of 20x20x20 cubes for frustum and occlusion culling. I understand how octrees work, I just dont know if I'm going about this the right way. My base octree class is taken from here: http://www.xnawiki.com/index.php/Octree What I'm wondering is how to apply occlusion culling using this class. Does it make sense to have one octree for each cube chunk? Or should I make the octree bigger? Since I'm using cubes, each cube should fit into a node without overlap so that won't be an issue

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• BoundingBox Intersection Problems

  - by Deukalion

  When I try to render two cubes, same sizes, one beside the other. With the same proportions (XYZ). My problem is, why do a Box1.BoundingBox.Contains(Box2.BoundingBox) == ContaintmentType.Intersects - when it clearly doesn't? I'm trying to place objects with BoundingBoxes as "intersection" checking, but this simple example clearly shows that this doesn't work. Why is that? I also try checking height of the next object to be placed, by checking intersection, adding each boxes height += (Max.Y - Min.Y) to a Height value, so when I add a new Box it has a height value. This works, but sometimes due to strange behavior it adds extra values when there isn't anything there. This is an example of what I mean: BoundingBox box1 = GetBoundaries(new Vector3(0, 0, 0), new Vector3(128, 64, 128)); BoundingBox box2 = GetBoundaries(new Vector3(128, 0, 0), new Vector3(128, 64, 128)); if (box1.Contains(box2) == ContainmentType.Intersects) { // This will be executed System.Windows.Forms.MessageBox.Show("Intersects = True"); } if (box1.Contains(box2) == ContainmentType.Disjoint) { System.Windows.Forms.MessageBox.Show("Disjoint = True"); } if (box1.Contains(box2) == ContainmentType.Contains) { System.Windows.Forms.MessageBox.Show("Contains = True"); } Test Method: public BoundingBox GetBoundaries(Vector3 position, Vector3 size) { Vector3[] vertices = new Vector3[8]; vertices[0] = position + new Vector3(-0.5f, 0.5f, -0.5f) * size; vertices[1] = position + new Vector3(-0.5f, 0.5f, 0.5f) * size; vertices[2] = position + new Vector3(0.5f, 0.5f, -0.5f) * size; vertices[3] = position + new Vector3(0.5f, 0.5f, 0.5f) * size; vertices[4] = position + new Vector3(-0.5f, -0.5f, -0.5f) * size; vertices[5] = position + new Vector3(-0.5f, -0.5f, 0.5f) * size; vertices[6] = position + new Vector3(0.5f, -0.5f, -0.5f) * size; vertices[7] = position + new Vector3(0.5f, -0.5f, 0.5f) * size; return BoundingBox.CreateFromPoints(vertices); } Box 1 should start at x -64, Box 2 should start at x 64 which means they never overlap. If I add Box 2 to 129 instead it creates a small gap between the cubes which is not pretty. So, the question is how can I place two cubes beside eachother and make them understand that they do not overlap or actually intersect? Because this way I can never automatically check for intersections or place cube beside eachother.

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• creating objects from trivial graph format text file. java. dijkstra algorithm.

  - by user560084

  i want to create objects, vertex and edge, from trivial graph format txt file. one of programmers here suggested that i use trivial graph format to store data for dijkstra algorithm. the problem is that at the moment all the information, e.g., weight, links, is in the sourcecode. i want to have a separate text file for that and read it into the program. i thought about using a code for scanning through the text file by using scanner. but i am not quite sure how to create different objects from the same file. could i have some help please? the file is v0 Harrisburg v1 Baltimore v2 Washington v3 Philadelphia v4 Binghamton v5 Allentown v6 New York # v0 v1 79.83 v0 v5 81.15 v1 v0 79.75 v1 v2 39.42 v1 v3 103.00 v2 v1 38.65 v3 v1 102.53 v3 v5 61.44 v3 v6 96.79 v4 v5 133.04 v5 v0 81.77 v5 v3 62.05 v5 v4 134.47 v5 v6 91.63 v6 v3 97.24 v6 v5 87.94 and the dijkstra algorithm code is Downloaded from: http://en.literateprograms.org/Special:Downloadcode/Dijkstra%27s_algorithm_%28Java%29 */ import java.util.PriorityQueue; import java.util.List; import java.util.ArrayList; import java.util.Collections; class Vertex implements Comparable<Vertex> { public final String name; public Edge[] adjacencies; public double minDistance = Double.POSITIVE_INFINITY; public Vertex previous; public Vertex(String argName) { name = argName; } public String toString() { return name; } public int compareTo(Vertex other) { return Double.compare(minDistance, other.minDistance); } } class Edge { public final Vertex target; public final double weight; public Edge(Vertex argTarget, double argWeight) { target = argTarget; weight = argWeight; } } public class Dijkstra { public static void computePaths(Vertex source) { source.minDistance = 0.; PriorityQueue<Vertex> vertexQueue = new PriorityQueue<Vertex>(); vertexQueue.add(source); while (!vertexQueue.isEmpty()) { Vertex u = vertexQueue.poll(); // Visit each edge exiting u for (Edge e : u.adjacencies) { Vertex v = e.target; double weight = e.weight; double distanceThroughU = u.minDistance + weight; if (distanceThroughU < v.minDistance) { vertexQueue.remove(v); v.minDistance = distanceThroughU ; v.previous = u; vertexQueue.add(v); } } } } public static List<Vertex> getShortestPathTo(Vertex target) { List<Vertex> path = new ArrayList<Vertex>(); for (Vertex vertex = target; vertex != null; vertex = vertex.previous) path.add(vertex); Collections.reverse(path); return path; } public static void main(String[] args) { Vertex v0 = new Vertex("Nottinghill_Gate"); Vertex v1 = new Vertex("High_Street_kensignton"); Vertex v2 = new Vertex("Glouchester_Road"); Vertex v3 = new Vertex("South_Kensignton"); Vertex v4 = new Vertex("Sloane_Square"); Vertex v5 = new Vertex("Victoria"); Vertex v6 = new Vertex("Westminster"); v0.adjacencies = new Edge[]{new Edge(v1, 79.83), new Edge(v6, 97.24)}; v1.adjacencies = new Edge[]{new Edge(v2, 39.42), new Edge(v0, 79.83)}; v2.adjacencies = new Edge[]{new Edge(v3, 38.65), new Edge(v1, 39.42)}; v3.adjacencies = new Edge[]{new Edge(v4, 102.53), new Edge(v2, 38.65)}; v4.adjacencies = new Edge[]{new Edge(v5, 133.04), new Edge(v3, 102.53)}; v5.adjacencies = new Edge[]{new Edge(v6, 81.77), new Edge(v4, 133.04)}; v6.adjacencies = new Edge[]{new Edge(v0, 97.24), new Edge(v5, 81.77)}; Vertex[] vertices = { v0, v1, v2, v3, v4, v5, v6 }; computePaths(v0); for (Vertex v : vertices) { System.out.println("Distance to " + v + ": " + v.minDistance); List<Vertex> path = getShortestPathTo(v); System.out.println("Path: " + path); } } } and the code for scanning file is import java.util.Scanner; import java.io.File; import java.io.FileNotFoundException; public class DataScanner1 { //private int total = 0; //private int distance = 0; private String vector; private String stations; private double [] Edge = new double []; /*public int getTotal(){ return total; } */ /* public void getMenuInput(){ KeyboardInput in = new KeyboardInput; System.out.println("Enter the destination? "); String val = in.readString(); return val; } */ public void readFile(String fileName) { try { Scanner scanner = new Scanner(new File(fileName)); scanner.useDelimiter (System.getProperty("line.separator")); while (scanner.hasNext()) { parseLine(scanner.next()); } scanner.close(); } catch (FileNotFoundException e) { e.printStackTrace(); } } public void parseLine(String line) { Scanner lineScanner = new Scanner(line); lineScanner.useDelimiter("\\s*,\\s*"); vector = lineScanner.next(); stations = lineScanner.next(); System.out.println("The current station is " + vector + " and the destination to the next station is " + stations + "."); //total += distance; //System.out.println("The total distance is " + total); } public static void main(String[] args) { /* if (args.length != 1) { System.err.println("usage: java TextScanner2" + "file location"); System.exit(0); } */ DataScanner1 scanner = new DataScanner1(); scanner.readFile(args[0]); //int total =+ distance; //System.out.println(""); //System.out.println("The total distance is " + scanner.getTotal()); } }

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• Diagonal line of sight with two corners

  - by Ash Blue

  Right now I'm using Bresenham's line algorithm for line of sight. The problem is I've found an edge case where players can look through walls. Occurs when the player looks between two corners of a wall with a gap on the other side at specific angles. The result I want is for the tile between two walls to be marked invalid as so. What is the fastest way to modify Bresenham's line algorithm to solve this? If there isn't a good solution, is there a better suited algorithm? Any ideas are welcome. Please note the solution should also be capable of supporting 3d. Edit: For the working source code and an interactive demo of the completed product please see http://ashblue.github.io/javascript-pathfinding/

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• "Best fit" to avoid reuse of object instances in a collection

  - by Simon

  Imagine I have a collection of object instances which represent activities for a user to undertake. Dependent on user attributes, I have to randomly select instances to present activities to the user. For some users, I need to present more activities to them than there are available activities in which case, I want to use the following algorithm. If all available activities have already been presented to the user, then re-select a "used" activity, selecting the earliest presented activity ordered by frequency of use. In other words, try to reduce repetition and where repetition is unavoidable, use the instances which have been repeated less often and were presented furthest back in time. Before I go on to code that algorithm, I wondered if there is some existing pattern I can re-use? [EDIT] "Furthest back in time" is not relevant as I will pass the algorithm an ordered collection of used instances where the first entry is the first presented.

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• 3D RTS pathfinding

  - by xcrypt

  I understand the A* algorithm, but I have some trouble doing it in 3D to suit the needs of my RTS Basically, in the game I'm making, there will be agents with different sizes of OBB collision boxes. I can use steering behaviours for avoiding other agents, so I don't need complete dynamic pathfinding. However, there is a problem because different agents have different collision geometry, and structures can be placed in almost any place. This means that there might be a gap between two structures where some agents can go through and some can't. A solution I have found to this problem is to do a sweep of the collision geometry of the agent from start node of the edge the pf algorithm is currently testing, to the end node of that edge. But this is probably a bit overkill since every edge the algorithm tests would also have to create and test with a collision geometry sweep. What are some reasonable approaches to this problem? I should mention that I'd prefer not to use navmeshes, I prefer waypoints because my entire system is based on it atm.

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• How can I obtain in-game data from Warcraft 3 from an external process?

  - by Slav

  I am implementing a behavior algorithm and would like to test it with my lovely Warcraft III game to watch how it will fight against real players. The problem I'm having is that I don't know how to obtain information about in-game state (units, structures, environment, etc.) from the running WC3 game. My algorithm needs access to the hard drive and possibly distributed computing, that's why JASS (WC3's editor language) isn't appropriate; I need to run my algorithm from a separate process. Direct3D hooking is an approach, but it wasn't done for WC3 yet and a significant drawback of that approach would be the inability to watch how the AI performs online, since it uses the viewport to issue commands. How I read in-game data from WC3 in a different process in a fastest and easiest way?

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• ADOMD & Excel Integration

  - by koumides

  All, We have an Excel spreadsheet that uses ADOMD to query OLAP cubes and present the data in Excel. We are using version 2.8 at the moment of the ADOMD API. As far as I know there is an ADOMD.NET API for querying OLAP cubes. Can this new .NET version used from inside Excel ? Many Thanks, MK

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• Logging errors caused by exceptions deep in the application

  - by Kaleb Pederson

  What are best-practices for logging deep within an application's source? Is it bad practice to have multiple event log entries for a single error? For example, let's say that I have an ETL system whose transform step involves: a transformer, pipeline, processing algorithm, and processing engine. In brief, the transformer takes in an input file, parses out records, and sends the records through the pipeline. The pipeline aggregates the results of the processing algorithm (which could do serial or parallel processing). The processing algorithm sends each record through one or more processing engines. So, I have at least four levels: Transformer - Pipeline - Algorithm - Engine. My code might then look something like the following: class Transformer { void Process(InputSource input) { try { var inRecords = _parser.Parse(input.Stream); var outRecords = _pipeline.Transform(inRecords); } catch (Exception ex) { var inner = new ProcessException(input, ex); _logger.Error("Unable to parse source " + input.Name, inner); throw inner; } } } class Pipeline { IEnumerable<Result> Transform(IEnumerable<Record> records) { // NOTE: no try/catch as I have no useful information to provide // at this point in the process var results = _algorithm.Process(records); // examine and do useful things with results return results; } } class Algorithm { IEnumerable<Result> Process(IEnumerable<Record> records) { var results = new List<Result>(); foreach (var engine in Engines) { foreach (var record in records) { try { engine.Process(record); } catch (Exception ex) { var inner = new EngineProcessingException(engine, record, ex); _logger.Error("Engine {0} unable to parse record {1}", engine, record); throw inner; } } } } } class Engine { Result Process(Record record) { for (int i=0; i<record.SubRecords.Count; ++i) { try { Validate(record.subRecords[i]); } catch (Exception ex) { var inner = new RecordValidationException(record, i, ex); _logger.Error( "Validation of subrecord {0} failed for record {1}", i, record ); } } } } There's a few important things to notice: A single error at the deepest level causes three log entries (ugly? DOS?) Thrown exceptions contain all important and useful information Logging only happens when failure to do so would cause loss of useful information at a lower level. Thoughts and concerns: I don't like having so many log entries for each error I don't want to lose important, useful data; the exceptions contain all the important but the stacktrace is typically the only thing displayed besides the message. I can log at different levels (e.g., warning, informational) The higher level classes should be completely unaware of the structure of the lower-level exceptions (which may change as the different implementations are replaced). The information available at higher levels should not be passed to the lower levels. So, to restate the main questions: What are best-practices for logging deep within an application's source? Is it bad practice to have multiple event log entries for a single error?

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• Come up with a real-world problem in which only the best solution will do (a problem from Introduction to algorithms) [closed]

  - by Mike

  EDITED (I realized that the question certainly needs a context) The problem 1.1-5 in the book of Thomas Cormen et al Introduction to algorithms is: "Come up with a real-world problem in which only the best solution will do. Then come up with one in which a solution that is “approximately” the best is good enough." I'm interested in its first statement. And (from my understanding) it is asked to name a real-world problem where only the exact solution will work as opposed to a real-world problem where good-enough solution will be ok. So what is the difference between the exact and good enough solution. Consider some physics problem for example the simulation of the fulid flow in the permeable medium. To make this simulation happen some simplyfing assumptions have to be made when deriving a mathematical model. Otherwise the model becomes at least complex and unsolvable. Virtually any particle in the universe has its influence on the fluid flow. But not all particles are equal. Those that form the permeable medium are much more influental than the ones located light years away. Then when the mathematical model needs to be solved an exact solution can rarely be found unless the mathematical model is simple enough (wich probably means the model isn't close to reality). We take an approximate numerical method and after hours of coding and days of verification come up with the program or algorithm which is a solution. And if the model and an algorithm give results close to a real problem by some degree that is good enough soultion. Its worth noting the difference between exact solution algorithm and exact computation result. When considering real-world problems and real-world computation machines I believe all physical problems solutions where any calculations are taken can not be exact because universal physical constants are represented approximately in the computer. Any numbers are represented with the limited precision, at least limited by amount of memory available to computing machine. I can imagine plenty of problems where good-enough, good to some degree solution will work, like train scheduling, automated trading, satellite orbit calculation, health care expert systems. In that cases exact solutions can't be derived due to constraints on computation time, limitations in computer memory or due to the nature of problems. I googled this question and like what this guy suggests: there're kinds of mathematical problems that need exact solutions (little note here: because the question is taken from the book "Introduction to algorithms" the term "solution" means an algorithm or a program, which in this case gives exact answer on each input). But that's probably more of theoretical interest. So I would like to narrow down the question to: What are the real-world practical problems where only the best (exact) solution algorithm or program will do (but not the good-enough solution)? There are problems like breaking of cryptographic ciphers where only exact solution matters in practice and again in practice the process of deciphering without knowing a secret should take reasonable amount of time. Returning to the original question this is the problem where good-enough (fast-enough) solution will do there's no practical need in instant crack though it's desired. So the quality of "best" can be understood in any sense: exact, fastest, requiring least memory, having minimal possible network traffic etc. And still I want this question to be theoretical if possible. In a sense that there may be example of computer X that has limited resource R of amount Y where the best solution to problem P is the one that takes not more than available Y for inputs of size N*Y. But that's the problem of finding solution for P on computer X which is... well, good enough. My final thought that we live in a world where it is required from programming solutions to practical purposes to be good enough. In rare cases really very very good but still not the best ones. Isn't it? :) If it's not can you provide an example? Or can you name any such unsolved problem of practical interest?

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