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  • Floating point undesireable in highly critical code?

    - by Kirt Undercoffer
    Question 11 in the Software Quality section of "IEEE Computer Society Real-World Software Engineering Problems", Naveda, Seidman, lists fp computation as undesirable because "the accuracy of the computations cannot be guaranteed". This is in the context of computing acceleration for an emergency braking system for a high speed train. This thinking seems to be invoking possible errors in small differences between measurements of a moving object but small differences at slow speeds aren't a problem (or shouldn't be), small differences between two measurements at high speed are irrelevant - can there be a problem with small roundoff errors during deceleration for an emergency braking system? This problem has been observed with airplane braking systems resulting in hydroplaning but could this actually happen in the context of a high speed train? The concern about fp errors seems to not be well-founded in this context. Any insight? The fp is used for acceleration so perhaps the concern is inching over a speed limit? But fp should be just fine if they use a double in whatever implementation language. The actual problem in the text states: During the inspection of the code for the emergency braking system of a new high speed train (a highly critical, real-time application), the review team identifies several characteristics of the code. Which of these characteristics are generally viewed as undesirable? The code contains three recursive functions (well that one is obvious). The computation of acceleration uses floating point arithmetic. All other computations use integer arithmetic. The code contains one linked list that uses dynamic memory allocation (second obvious problem). All inputs are checked to determine that they are within expected bounds before they are used.

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  • Floating point undesirable in highly critical code?

    - by Kirt Undercoffer
    Question 11 in the Software Quality section of "IEEE Computer Society Real-World Software Engineering Problems", Naveda, Seidman, lists fp computation as undesirable because "the accuracy of the computations cannot be guaranteed". This is in the context of computing acceleration for an emergency braking system for a high speed train. This thinking seems to be invoking possible errors in small differences between measurements of a moving object but small differences at slow speeds aren't a problem (or shouldn't be), small differences between two measurements at high speed are irrelevant - can there be a problem with small roundoff errors during deceleration for an emergency braking system? This problem has been observed with airplane braking systems resulting in hydroplaning but could this actually happen in the context of a high speed train? The concern about fp errors seems to not be well-founded in this context. Any insight? The fp is used for acceleration so perhaps the concern is inching over a speed limit? But fp should be just fine if they use a double in whatever implementation language. The actual problem in the text states: During the inspection of the code for the emergency braking system of a new high speed train (a highly critical, real-time application), the review team identifies several characteristics of the code. Which of these characteristics are generally viewed as undesirable? The code contains three recursive functions (well that one is obvious). The computation of acceleration uses floating point arithmetic. All other computations use integer arithmetic. The code contains one linked list that uses dynamic memory allocation (second obvious problem). All inputs are checked to determine that they are within expected bounds before they are used.

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  • external disk dont work on ubuntu

    - by Skirki
    i have problem with in my ubuntu: when i connect external imation apollo disc i dont see a file system. Disk is working because in windows OS on this same computer it works as well. when i typed dmesg i got following logs [12913.260078] usb 4-1: new low speed USB device using ohci_hcd and address 15 [12913.440072] usb 4-1: device descriptor read/64, error -62 [12913.730058] usb 4-1: device descriptor read/64, error -62 [12914.020085] usb 4-1: new low speed USB device using ohci_hcd and address 16 [12914.200082] usb 4-1: device descriptor read/64, error -62 [12914.490150] usb 4-1: device descriptor read/64, error -62 [12914.780064] usb 4-1: new low speed USB device using ohci_hcd and address 17 [12915.200070] usb 4-1: device not accepting address 17, error -62 [12915.380081] usb 4-1: new low speed USB device using ohci_hcd and address 18 [12915.800065] usb 4-1: device not accepting address 18, error -62 [12915.800100] hub 4-0:1.0: unable to enumerate USB device on port 1 i trying to fix that by use commands: cd /sys/bus/pci/drivers/ehci_hcd echo -n "0000:00:02.1" unbind but it did not match the result and i don't have any other idea

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  • 2d ball collision code problem XNA, over accelerated balls and stick together sometimes. help please? [closed]

    - by Sivan
    public static void Collision(Ball ball1, Ball ball2) { Vector3 x = new Vector3((ball1.BallPosition.X - ball2.BallPosition.X), (ball1.BallPosition.Y - ball2.BallPosition.Y), 0); x.Normalize(); Vector3 v1 = new Vector3(ball1.Speed, 0); float x1 = Vector3.Dot(x, v1); Vector3 v1x = x * x1; Vector3 v1y = v1 - v1x; x = -x; Vector3 v2 = new Vector3(ball2.Speed, 0); float x2 = Vector3.Dot(x, v2); Vector3 v2x = x * x2; Vector3 v2y = v2 - v2x; float m1 = 12, m2 = 4; float combinedMass = m1 + m2; Vector3 newVelA = (v1x * ((m1 - m2) / combinedMass)) + (v2x * ((2f * m2) / combinedMass)) + v1y; Vector3 newVelB = (v1x * ((2f * m1) / combinedMass)) + (v2x * ((m2 - m1) / combinedMass)) + v2y; ball1.Speed = new Vector2(newVelA.X, newVelA.Y); ball2.Speed = new Vector2(newVelB.X,newVelB.Y ); }

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  • My python program always brings down my internet connection after several hours running, how do I debug and fix this problem?

    - by Shane
    I'm writing a python script checking/monitoring several server/websites status(response time and similar stuff), it's a GUI program and I use separate thread to check different server/website, and the basic structure of each thread is using an infinite while loop to request that site every random time period(15 to 30 seconds), once there's changes in website/server each thread will start a new thread to do a thorough check(requesting more pages and similar stuff). The problem is, my internet connection always got blocked/jammed/messed up after several hours running of this script, the situation is, from my script side I got urlopen error timed out each time it's requesting a page, and from my FireFox browser side I cannot open any site. But the weird thing is, the moment I close my script my Internet connection got back on immediately which means now I can surf any site through my browser, so it must be the script causing all the problem. I've checked the program carefully and even use del to delete any connection once it's used, still get the same problem. I only use urllib2, urllib, mechanize to do network requests. Anybody knows why such thing happens? How do I debug this problem? Is there a tool or something to check my network status once such situation occurs? It's really bugging me for a while... By the way I'm behind a VPN, does it have something to do with this problem? Although I don't think so because my network always get back on once the script closed, and the VPN connection never drops(as it appears) during the whole process.

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  • Connecting via ShrewSoft VPN client means no LAN internet access (Windows 7 64 bit) - any advice please?

    - by iwishiknewmoreaboutnetworking
    I have a Windows 7 64 bit desktop machine which is connected to a LAN. I recently installed ShrewSoft VPN client v 2.1.7 on my machine so that I can connect to a license server hosted by my customer. They are running a Cisco VPN server and I originally tried (unsuccessfully!) to use the Cisco VPN client for Windows 64 bit but the default gateway wasn't being configured correctly after loading in my pcf file. Using ShrewSoft I am able to import the same pcf file, and successfully connect to the machine I need to using the VPN client software. The client machine I need to connect to has IP address 1.52.90.33. The problem is that when I am connected to the customer network using the VPN client application (and after a few minutes) I lose my LAN internet connection. I can only presume that this is because, by default the ShrewSoft VPN client application automatically tunnels all traffic through the VPN connection. I know there is an option to switch off the "Tunnel All" option on the Policy tab of the application and enter a Remote Network Resource (to "Include" or "Exclude") as "Address" and "Netmask" IP addresses however I am not sure what I need to enter here. Here is my ipconfig output before connecting to the VPN (with suffixes blanked out): Windows IP Configuration Ethernet adapter Local Area Connection: Connection-specific DNS Suffix . : ***.*** Link-local IPv6 Address . . . . . : fe80::8de3:9dbe:393a:33ba%11 IPv4 Address. . . . . . . . . . . : 150.237.13.17 Subnet Mask . . . . . . . . . . . : 255.255.255.0 Default Gateway . . . . . . . . . : 150.237.13.1 Tunnel adapter 6TO4 Adapter: Connection-specific DNS Suffix . : ***.*** IPv6 Address. . . . . . . . . . . : 2002:96ed:d11::96ed:d11 Default Gateway . . . . . . . . . : 2002:c058:6301::c058:6301 Tunnel adapter Local Area Connection* 9: Connection-specific DNS Suffix . : IPv6 Address. . . . . . . . . . . : 2001:0:4137:9e76:2cf9:38c4:6912:f2ee Link-local IPv6 Address . . . . . : fe80::2cf9:38c4:6912:f2ee%12 Default Gateway . . . . . . . . . : Tunnel adapter isatap.***.***: Media State . . . . . . . . . . . : Media disconnected Connection-specific DNS Suffix . : ***.*** Here is my route print output before connecting to the VPN: =========================================================================== Interface List 11...20 cf 30 9d ec 2a ......Realtek RTL8168D/8111D Family PCI-E Gigabit Ethern et NIC (NDIS 6.20) 1...........................Software Loopback Interface 1 14...00 00 00 00 00 00 00 e0 Microsoft 6to4 Adapter 12...00 00 00 00 00 00 00 e0 Teredo Tunneling Pseudo-Interface 13...00 00 00 00 00 00 00 e0 Microsoft ISATAP Adapter #2 =========================================================================== IPv4 Route Table =========================================================================== Active Routes: Network Destination Netmask Gateway Interface Metric 0.0.0.0 0.0.0.0 150.237.13.1 150.237.13.17 2 127.0.0.0 255.0.0.0 On-link 127.0.0.1 306 127.0.0.1 255.255.255.255 On-link 127.0.0.1 306 127.255.255.255 255.255.255.255 On-link 127.0.0.1 306 150.237.13.0 255.255.255.0 On-link 150.237.13.17 257 150.237.13.17 255.255.255.255 On-link 150.237.13.17 257 150.237.13.255 255.255.255.255 On-link 150.237.13.17 257 224.0.0.0 240.0.0.0 On-link 127.0.0.1 306 224.0.0.0 240.0.0.0 On-link 150.237.13.17 257 255.255.255.255 255.255.255.255 On-link 12

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  • HTG Explains: Are You Using IPv6 Yet? Should You Even Care?

    - by Chris Hoffman
    IPv6 is extremely important for the long-term health of the Internet. But is your Internet service provider providing IPv6 connectivity yet? Does your home network support it? Should you even care if you’re using IPv6 yet? Switching from IPv4 to IPv6 will give the Internet a much larger pool of IP addresses. It should also allow every device to have its own public IP address, rather than be hidden behind a NAT router. IPv6 is Important Long-Term IPv6 is very important for the long-term health of the Internet. There are only about 3.7 billion public IPv4 addresses. This may sound like a lot, but it isn’t even one IP address for each person on the planet. Considering people have more and more Internet-connected devices — everything from light bulbs to thermostats are starting to become network-connected — the lack of IP addresses is already proving to be a serious problem. This may not affect those of us in well-off developed countries just yet, but developing countries are already running out of IPv4 addresses. So, if you work at an Internet service provider, manage Internet-connected servers, or develop software or hardware — yes, you should care about IPv6! You should be deploying it and ensuring your software and hardware works properly with it. It’s important to prepare for the future before the current IPv4 situation becomes completely unworkable. But, if you’re just typical user or even a typical geek with a home Internet connection and a home network, should you really care about your home network just yet? Probably not. What You Need to Use IPv6 To use IPv6, you’ll need three things: An IPv6-Compatible Operating System: Your operating system’s software must be capable of using IPv6. All modern desktop operating systems should be compatible — Windows Vista and newer versions of Windows, as well as modern versions of Mac OS X and Linux. Windows XP doesn’t have IPv6 support installed by default, but you shouldn’t be using Windows XP anymore, anyway. A Router With IPv6 Support: Many — maybe even most — consumer routers in the wild don’t support IPv6. Check your router’s specifications details to see if it supports IPv6 if you’re curious. If you’re going to buy a new router, you’ll probably want to get one with IPv6 support to future-proof yourself. If you don’t have an IPv6-enabled router yet, you don’t need to buy a new one just to get it. An ISP With IPv6 Enabled:  Your Internet service provider must also have IPv6 set up on their end. Even if you have modern software and hardware on your end, your ISP has to provide an IPv6 connection for you to use it. IPv6 is rolling out steadily, but slowly — there’s a good chance your ISP hasn’t enabled it for you yet. How to Tell If You’re Using IPv6 The easiest way to tell if you have IPv6 connectivity is to visit a website like testmyipv6.com. This website allows you to connect to it in different ways — click the links near the top to see if you can connect to the website via different types of connections. If you can’t connect via IPv6, it’s either because your operating system is too old (unlikely), your router doesn’t support IPv6 (very possible), or because your ISP hasn’t enabled it for you yet (very likely). Now What? If you can connect to the test website above via IPv6, congratulations! Everything is working as it should. Your ISP is doing a good job of rolling out IPv6 rather than dragging its feet. There’s a good chance you won’t have IPv6 working properly, however. So what should you do about this — should you head to Amazon and buy a new IPv6-enabled router or switch to an ISP that offers IPv6? Should you use a “tunnel broker,” as the test site recommends, to tunnel into IPv6 via your IPv4 connection? Well, probably not. Typical users shouldn’t have to worry about this yet. Connecting to the Internet via IPv6 shouldn’t be perceptibly faster, for example. It’s important for operating system vendors, hardware companies, and Internet service providers to prepare for the future and get IPv6 working, but you don’t need to worry about this on your home network. IPv6 is all about future-proofing. You shouldn’t be racing to implement this at home yet or worrying about it too much — but, when you need to buy a new router, try to buy one that supports IPv6. Image Credit: Adobe of Chaos on Flickr, hisperati on Flickr, Vox Efx on Flickr     

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  • Lockdown users on Windows Server 2012

    - by el.severo
    I set up a Active Directory on a server machine with Windows Server 2012 and I'd like to create some users with limitations like Windows Steady State does in Windows XP (locally). Seen already the Windows SteadyState Handbook (with Windows Server 2008), but I'd like to know if anyone has tried this before, the limitations are the following: 1. Prevent locked or roaming user profiles that cannot be found on the computer from logging on 2. Do not cache copies of locked or roaming user profiles for users who have previously logged on to this computer 3. Do not allow Windows to compute and store passwords using LAN Manager Hash values 4. Do not store usernames or passwords used to log on to the Windows Live ID or the domain 5. Prevent users from creating folders and files on drive C:\ 6. Lock profile to prevent the user from making permanent changes 7. Remove the Control Panel, Printer and Network Settings from the Classic Start menu 8. Remove the Favorites icon 9. Remove the My Network Places icon 10. Remove the Frequently Used Program list 11. Remove the Shared documents folder from My Computer 12. Remove control Panel icon 13. Remove the Set Program Access and Defaults icon 14. Remove the Network Connection(Connect To)icon 15. Remove the Printers and Faxes icon 16. Remove the Run icon 17. Prevent access to Windows Explorer features: Folder Options, Customize Toolbar, and the Notification Area 18. Prevent access to the taskbar 19. Prevent access to the command prompt 20. Prevent access to the registry editor 21. Prevent access to the Task Manager 22. Prevent access to Microsoft Management Console utilities 23. Prevent users from adding or removing printers 24. Prevent users from locking the computer 25. Prevent password changes (also requires the Control Panel icon to be removed) 26. Disable System Tools and other management programs 27. Prevent users from saving files to the desktop 28. Hide A Drive 29. Hide B Drive 30. Hide C Drive 31. Prevent changes to Internet Explorer registry settings 32. Empty the Temporary Internet Files folder when Internet Explorer is closed 33. Remove Internet Options 34. Remove General tab in Internet Options 35. Remove Security tab in Internet Options 36. Remove Privacy tab in Internet Options 37. Remove Content tab in Internet Options 38. Remove Connections tab in Internet Options 39. Remove Programs tab in Internet Options 40. Remove Advanced tab in Internet Options 41. Set a home page (Internet Explorer) 42. Restrict the possibility to change desktop image 43. Restrict the possibility to change wallpaper 44. Restrict usb flash drives Any suggestions for this? UPDATE: As @Dan suggested me I'd like to specify that would be applied to a educational scenario where students can login from a computer and want to add some restrictions to them.

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  • Is JPA + EJB to much slow (or heavy) for over Internet transactions?

    - by Xavier Callejas
    Hi, I am developing a stand-alone java client application that connects to a Glassfish v3 application for JPA/EJB facade style transactions. In other words, my client application do not connect directly to the database to CRUD, but it transfers JPA objets using EJB stateless sessions. I have scenarios where this client application will be used in an external network connected with a VPN over Internet with a client connection of 512kbp/DSL, and a simple query takes so much time, I'm seeing the traffic graph and when I merge a entity in the client application I see megabytes of traffic (I couldn't believe how a purchase order entity could weight more than 1 mb). I have LAZY fetch in almost every many-to-many relationship, but I have a lot of many-to-one relationships between entities (but this is the great advantage of JPA!). Could I do something to accelerate the the speed of transactions between JPA/EJB server and the remote java client? Thank you in advance.

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  • Mailing Lists Are Parties. Or They Should Be.

    <b>Luis Villa's Internet Home:</b> "I can&#8217;t go to bed because Mairin is right on the internet and so I want to (1) say she&#8217;s awesome and (2) add two cents on mailing lists and using the power of a web interface to make them better. Bear with me; maybe this is completely off-base (probably I should just stick to law), but it has been bouncing around in my head for years and maybe me writing it down will help the lightbulb go off for someone who can actually implement it :)"

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  • How can I configure WCF to use x509 certificates over the internet?

    - by Ben Laan
    I need to use an x509 certificate to get secure message level authentication from a rich client via the internet to a secure WCF Web Service. Specifically, I am looking for a working step-by-step guide to setup, configuration, coding, and deployment, including creating a 'dev' certificate, installing it, and obtaining a 'real' certificate for production.

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