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  • Rainbow Tables: How to improve upon them??

    - by CVS-2600Hertz-wordpress-com
    I recently obtained the l0pht-CD for windows and tried it out on my PC and It WORKS!! http://2600hertz.wordpress.com/2009/12/22/100-windows-xp-vista-7-password-recovery/ I have also read http://kestas.kuliukas.com/RainbowTables/ I'm designing a "Login-Simulator" that stores pwd-s in a similar manner. The current implementation will be vulnerable to the above attack. Plz could anyone illustrate (in as simple terms as possible), how to strengthen the rainbow tables against such an attack. MY GOAL : Build "Login-Simulator" to be as secure as possible. (Read Hacking Competition ;-) ) Thank You.

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  • Can NSUserDefaults be used for pausing the application during a phone call ?

    - by Anil Kumar
    Friends, currently I dont have iphone to test and using Simulator for testing purposes. I am Just curious to know whether an application continues to run even after a phone call.. here i have no option to test this from simulator. If it terminates then how can i pause things.. and continue after a phone call. Is NSUserDefaults can be used for my case. As far I understood NSuserDefaults are used to store data that is required when the App is next time loaded. But here I dont want my App to terminate instead pause until Call ends and continue as uninterrupted later. Please clear me about this. Sorry I am still a beginner so I request for no harsh replies if my question looks stupid. Thanks in Advance

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  • How can I send email from my application ?

    - by srikanth rongali
    I want to attach a video and send email from my application. I downloaded apples example code MailComposer. I compiled it. I did not get any errors or warnings. I sent the mail to my mail id. But, I could not see any mail in my inbox. I am working on simulator. I did not set any senders email id in simulator. How can I know whether the code is working or not ? Thank You.

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  • Image Size for Animation!

    - by taimur-hamza
    Hi Everybody, I m new to iphone app development and i need some help. I have a list of 30 images that i have to animate and display with 0.1 second interval. I put all the images in an Array using this imageletter.animationImages = [NSArray arrayWithObjects:[UIImage imageNamed:@"1.png"], ...... ,nil] And then animate it using these statements, [imageletter setAnimationDuration:16]; [imageletter startAnimating]; [NSTimer scheduledTimerWithTimeInterval:mytime target:self selector:@selector(StopAfterCertainTime) userInfo:nil repeats:NO]; Now the problem is that the size of each image is 8kb , it runs fine on iphone simulator but crashes on device. When i used 30 other images of 4kb each it runs fine both on simulator and device. Can anybody tell me what is the ideal size for such kind of task. Thanks

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  • How can find out the system default currency symbol on BlackBerry?

    - by ageektrapped
    I have a need to display a currency value in my application. There doesn't seem to be an easy way to do this with the RIM API, so I'm reduced to creating my own solution (a common refrain for BlackBerry development, unfortunately) Currently I'm using the Formatter class, from javax.microedition.locale like so protected String formatResult(double result) { try { Locale l = Locale.getDefaultForSystem(); Formatter formatter = new Formatter(l.toString()); return formatter.formatCurrency(result); } catch (UnsupportedLocaleException e) { return "This fails for the default locale because BlackBerry sucks"; } } I always hit the catch block in the simulator. Since this doesn't work by default on the simulator, I'm hesitant to put it in the application. So I have two questions: Can anyone tell me if the above solution is the way to go? And how to fix it, of course. Is there a way I can retrieve the currency symbol for the current locale programmatically so I can format myself?

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  • How can I use a pre-populated core data DB on my device.

    - by KingAndrew
    Hi all, I have developed my app using core data. It works fine in the simulator. When I deploy it to the device the DB is empty. It is 49k where it should be 484k. Basically it is not populated. Since I don't write to the DB when the app is running I need to provide a populated DB to the App. So I copied the populated DB from the simulator to resources and then deploy. Still no luck. the populated DB is in MyApp.app and the AppDelegate is reading from the Documents directory. How do I either get it in the documents directory or get the app delegate to look in the app? Thanks in advance, Andrew

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  • What is the right way to implement communication between java objects?

    - by imoschak
    I'm working on an academic project which simulates a rather large queuing procedure in java. The core of the simulator rests within one package where there exist 8 classes, each one implementing a single concept. Every class in the project follows SRP. These classes encapsulate the behavior of the simulator and inter-connect every other class in the project. The problem that has arisen is that most of these 8 classes are, as is logical i think, tightly coupled and each one has to have working knowledge of every other class in this package in order to be able to call methods from it when needed. The application needs only one instance of each class so it might be better to create static fields for each class in a new class and use that to make calls -instead of preserving a reference in each class for every other class in the package (which I'm certain that is incorrect)-, but is this considered a correct design solution? or is there a design pattern maybe that better suits my needs?

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  • How to use a self-signed SSL certificate when developing with Trigger.io?

    - by user610345
    Our backend is in rails, and for several reasons the development environment has to be run with rails using a self-signed SSL certificate. This works fine on the desktop after manually trusting the certificate. Using Trigger.io, we're developing a mobile application targeting iOS from the same backend. It would be ideal for us to be able to run the rails server with SSL (so we can compare the browser output) and still have the iOS simulator connect properly without complaining about invalid certs. Production is using a proper ssl-cert, but what's the best way to set up the simulator?

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  • iDevice for Dummies: Can a device be assigned multiple provisions (Personal/Enterprise)?

    - by Alex
    Hi guys, Is it possible to assign multiple provisions to an iDevice? To be honest, I'm not sure if I'm using the correct terminology, but basically, I'm developing an iPad app for a company and I've only been testing it in the simulator because I don't have a registration to the developer program and they haven't setup their enterprise registration yet either. And I'm sure you all know how limited the simulator is... I don't really care about the $99 it costs to join, but what I'm worried about is having my iDevices locked permanently to my personal registration and unable to switch back and forth to the enterprise registration. I'd appreciate it if someone can explain to me how the registrations work. And keep in mind, I'm a dummy. :) Thanks in advance!

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  • The right way to implement communication between java objects

    - by imoschak
    I'm working on an academic project which simulates a rather large queuing procedure in java. The core of the simulator rests within one package where there exist 8 classes each one implementing a single concept. Every class in the project follows SRP. These classes encapsulate the behavior of the simulator and inter-connect every other class in the project. The problem that I has arisen is that most of these 8 classes are, as is logical i think, tightly coupled and each one has to have working knowledge of every other class in this package in order to be able to call methods from it when needed. The application needs only one instance of each class so it might be better to create static fields for each class in a new class and use that to make calls -instead of preserving a reference in each class for every other class in the package (which I'm certain that is incorrect)-, but is this considered a correct design solution? or is there a design pattern maybe that better suits my needs?

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  • Configuring CESoPSN using Cisco MWR 2941

    - by Rayne
    I'm trying to configure CESoPSN on two Cisco MWR 2941 routers, but the alarm LED lights are always lit. My configuration is modeled after this sample configuration. My setup is as follows: On the Cisco MWRs, E1 0/5 is configured to be CESoPSN, E1 0/9 is configured to be CESoPSN (CAS mode), and E1 0/7 is configured to be SAToP. The two MWRs are connected to each other via the GigabitEthernet port 0/2. The GigE ports are configured as a vlan because the ports are L2 ports and cannot be assigned an IP address directly. The two Cisco MWRs are connected to a traffic simulator, i.e. the traffic simulator will play out E1 traffic to MWR 1 and record the output traffic from MWR 2. On my traffic simulator, when it's connected to the E1 ports 0/5 and 0/9 (both CESoPSN configurations), the "Remote" alarm is on. However, when connected to the E1 ports 0/7 (SAToP configuration), no alarms were on. The GigE connection seems to be working fine (both LED lights on the 2 ports are green). The SAToP configuration seems to be fine too (Left LED is green, right LED is off on both E1 0/7 ports). However, both CESoPSN configurations seem to be not working (Left LED is green, right LED is yellow on both E1 0/5 and 0/9 ports). I don't know if there's anything wrong with my configuration for the CESoPSN, as I'm very new to this. The relevant portions of the configuration are as follows: MWR 1: controller E1 0/5 clock source internal cem-group 5 timeslots 1-31 description E1 CESoPSN example ! controller E1 0/7 clock source internal cem-group 7 unframed description E1 SATOP example ! controller E1 0/9 mode cas clock source internal cem-group 9 timeslots 1-24 description E1 CESoPSN CAS example ! interface Loopback0 ip address 30.30.30.1 255.255.255.255 ! interface GigabitEthernet0/2 switchport access vlan 100 mpls ip ! interface CEM0/5 no ip address cem 5 xconnect 30.30.30.2 305 encapsulation mpls ! ! interface CEM0/7 no ip address cem 7 xconnect 30.30.30.2 307 encapsulation mpls ! ! interface CEM0/9 no ip address cem 9 signaling inband-cas xconnect 30.30.30.2 309 encapsulation mpls ! ! interface Vlan100 ip address 50.50.50.1 255.255.255.0 no ptp enable mpls ip ! no ip classless ip forward-protocol nd ip route 30.30.30.2 255.255.255.255 50.50.50.2 ! MWR 2: controller E1 0/5 clock source internal cem-group 5 timeslots 1-31 description E1 CESoPSN example ! controller E1 0/7 clock source internal cem-group 7 unframed ! controller E1 0/9 mode cas clock source internal cem-group 9 timeslots 1-24 description E1 CESoPSN CAS example ! interface Loopback0 ip address 30.30.30.2 255.255.255.255 ! interface GigabitEthernet0/2 switchport access vlan 100 mpls ip ! interface CEM0/5 no ip address cem 5 xconnect 30.30.30.1 305 encapsulation mpls ! ! interface CEM0/7 no ip address cem 7 xconnect 30.30.30.1 307 encapsulation mpls ! ! interface CEM0/9 no ip address cem 9 signaling inband-cas xconnect 30.30.30.1 309 encapsulation mpls ! ! interface Vlan100 ip address 50.50.50.2 255.255.255.0 no ptp enable mpls ip ! no ip classless ip forward-protocol nd ip route 30.30.30.1 255.255.255.255 50.50.50.1 ! If anyone is familiar with CESoPSN configurations, please advise.

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  • AGENT: The World's Smartest Watch

    - by Rob Chartier
    AGENT: The World's Smartest Watch by Secret Labs + House of Horology Disclaimer: Most if not all of this content has been gleaned from the comments on the Kickstarter project page and comments section. Any discrepancies between this post and any documentation on agentwatches.com, kickstarter.com, etc.., those official sites take precedence. Overview The next generation smartwatch with brand-new technology. World-class developer tools, unparalleled battery life, Qi wireless charging. Kickstarter Page, Comments Funding period : May 21, 2013 - Jun 20, 2013 MSRP : $249 Other Urls http://www.agentwatches.com/ https://www.facebook.com/agentwatches http://twitter.com/agentwatches http://pinterest.com/agentwatches/ http://paper.li/robchartier/1371234640 Developer Story The first official launch of the preview SDK and emulator will happen on 20-Jun-2013.  All development will be done in Visual Studio 2012, using the .NET Micro Framework SDK 2.3.  The SDK will ship with the first round of the expected API for developers along with an emulator. With that said, there is no need to wait for the SDK.  You can download the tooling now and get started with Apps and Faces immediately.  The only thing that you will not be able to work with is the API; but for example, watch faces, you can start building the basic face rendering with the Bitmap graphics drawing in the .NET Micro Framework.   Does it look good? Before we dig into any more of the gory details, here are a few photos of the current available prototype models.   The watch on the tiny QI Charter   If you wander too far away from your phone, your watch will let you know with a vibration and a message, all but one button will dismiss the message.   An app showing the premium weather data!   Nice stitching on the straps, leather and silicon will be available, along with a few lengths to choose from (short, regular, long lengths). On to those gory details…. Hardware Specs Processor 120MHz ARM Cortex-M4 processor (ATSAM4SD32) with secondary AVR co-processor Flash & RAM 2MB of onboard flash and 160KB of RAM 1/4 of the onboard flash will be used by the OS The flash is permanent (non-volatile) storage. Bluetooth Bluetooth 4.0 BD/EDR + LE Bluetooth 4.0 is backwards compatible with Bluetooth 2.1, so classic Bluetooth functions (BD/EDR, SPP/AVRCP/PBAP/etc.) will work fine. Sensors 3D Accelerometer (Motion) ST LSM303DLHC Ambient Light Sensor Hardware power metering Vibration Motor (You can pulse it to create vibration patterns, not sure about the vibration strength - driven with PWM) No piezo/speaker or microphone. Other QI Wireless Charging, no NFC, no wall adapter included Custom LED Backlight No GPS in the watch. It uses the GPS in your phone. AGENT watch apps are deployed and debugged wirelessly from your PC via Bluetooth. RoHS, Pb-free Battery Expected to use a CR2430-sized rechargeable battery – replaceable (Mouser, Amazon) Estimated charging time from empty is 2 hours with provided charger 7 Days typical with Bluetooth on, 30 days with Bluetooth off (watch-face only mode) The battery should last at least 2 years, with 100s of charge cycles. Physical dimensions Roughly 38mm top-to-bottom on the front face 35mm left-to-right on the front face and around 12mm in depth 22mm strap Two ~1/16" hex screws to attach the watch pin The top watchcase material candidates are PVD stainless steel, brushed matte ceramic, and high-quality polycarbonate (TBD). The glass lens is mineral glass, Anti-glare glass lens Strap options Leather and silicon straps will be available Expected to have three sizes Display 1.28" Sharp Memory Display The display stays on 100% of the time. Dimensions: 128x128 pixels Buttons Custom "Pusher" buttons, they will not make noise like a mouse click, and are very durable. The top-left button activates the backlight; bottom-left changes apps; three buttons on the right are up/select/down and can be used for custom purposes by apps. Backup reset procedure is currently activated by holding the home/menu button and the top-right user button for about ten seconds Device Support Android 2.3 or newer iPhone 4S or newer Windows Phone 8 or newer Heart Rate monitors - Bluetooth SPP or Bluetooth LE (GATT) is what you'll want the heart monitor to support. Almost limitless Bluetooth device support! Internationalization & Localization Full UTF8 Support from the ground up. AGENT's user interface is in English. Your content (caller ID, music tracks, notifications) will be in your native language. We have a plan to cover most major character sets, with Latin characters pre-loaded on the watch. Simplified Chinese will be available Feature overview Phone lost alert Caller ID Music Control (possible volume control) Wireless Charging Timer Stopwatch Vibrating Alarm (possibly custom vibrations for caller id) A few default watch faces Airplane mode (by demand or low power) Can be turned off completely Customizable 3rd party watch faces, applications which can be loaded over bluetooth. Sample apps that maybe installed Weather Sample Apps not installed Exercise App Other Possible Skype integration over Bluetooth. They will provide an AGENT app for your smartphone (iPhone, Android, Windows Phone). You'll be able to use it to load apps onto the watch.. You will be able to cancel phone calls. With compatible phones you can also answer, end, etc. They are adopting the standard hands-free profile to provide these features and caller ID.

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  • World Record Batch Rate on Oracle JD Edwards Consolidated Workload with SPARC T4-2

    - by Brian
    Oracle produced a World Record batch throughput for single system results on Oracle's JD Edwards EnterpriseOne Day-in-the-Life benchmark using Oracle's SPARC T4-2 server running Oracle Solaris Containers and consolidating JD Edwards EnterpriseOne, Oracle WebLogic servers and the Oracle Database 11g Release 2. The workload includes both online and batch workload. The SPARC T4-2 server delivered a result of 8,000 online users while concurrently executing a mix of JD Edwards EnterpriseOne Long and Short batch processes at 95.5 UBEs/min (Universal Batch Engines per minute). In order to obtain this record benchmark result, the JD Edwards EnterpriseOne, Oracle WebLogic and Oracle Database 11g Release 2 servers were executed each in separate Oracle Solaris Containers which enabled optimal system resources distribution and performance together with scalable and manageable virtualization. One SPARC T4-2 server running Oracle Solaris Containers and consolidating JD Edwards EnterpriseOne, Oracle WebLogic servers and the Oracle Database 11g Release 2 utilized only 55% of the available CPU power. The Oracle DB server in a Shared Server configuration allows for optimized CPU resource utilization and significant memory savings on the SPARC T4-2 server without sacrificing performance. This configuration with SPARC T4-2 server has achieved 33% more Users/core, 47% more UBEs/min and 78% more Users/rack unit than the IBM Power 770 server. The SPARC T4-2 server with 2 processors ran the JD Edwards "Day-in-the-Life" benchmark and supported 8,000 concurrent online users while concurrently executing mixed batch workloads at 95.5 UBEs per minute. The IBM Power 770 server with twice as many processors supported only 12,000 concurrent online users while concurrently executing mixed batch workloads at only 65 UBEs per minute. This benchmark demonstrates more than 2x cost savings by consolidating the complete solution in a single SPARC T4-2 server compared to earlier published results of 10,000 users and 67 UBEs per minute on two SPARC T4-2 and SPARC T4-1. The Oracle DB server used mirrored (RAID 1) volumes for the database providing high availability for the data without impacting performance. Performance Landscape JD Edwards EnterpriseOne Day in the Life (DIL) Benchmark Consolidated Online with Batch Workload System Rack Units BatchRate(UBEs/m) Online Users Users /Units Users /Core Version SPARC T4-2 (2 x SPARC T4, 2.85 GHz) 3 95.5 8,000 2,667 500 9.0.2 IBM Power 770 (4 x POWER7, 3.3 GHz, 32 cores) 8 65 12,000 1,500 375 9.0.2 Batch Rate (UBEs/m) — Batch transaction rate in UBEs per minute Configuration Summary Hardware Configuration: 1 x SPARC T4-2 server with 2 x SPARC T4 processors, 2.85 GHz 256 GB memory 4 x 300 GB 10K RPM SAS internal disk 2 x 300 GB internal SSD 2 x Sun Storage F5100 Flash Arrays Software Configuration: Oracle Solaris 10 Oracle Solaris Containers JD Edwards EnterpriseOne 9.0.2 JD Edwards EnterpriseOne Tools (8.98.4.2) Oracle WebLogic Server 11g (10.3.4) Oracle HTTP Server 11g Oracle Database 11g Release 2 (11.2.0.1) Benchmark Description JD Edwards EnterpriseOne is an integrated applications suite of Enterprise Resource Planning (ERP) software. Oracle offers 70 JD Edwards EnterpriseOne application modules to support a diverse set of business operations. Oracle's Day in the Life (DIL) kit is a suite of scripts that exercises most common transactions of JD Edwards EnterpriseOne applications, including business processes such as payroll, sales order, purchase order, work order, and manufacturing processes, such as ship confirmation. These are labeled by industry acronyms such as SCM, CRM, HCM, SRM and FMS. The kit's scripts execute transactions typical of a mid-sized manufacturing company. The workload consists of online transactions and the UBE – Universal Business Engine workload of 61 short and 4 long UBEs. LoadRunner runs the DIL workload, collects the user’s transactions response times and reports the key metric of Combined Weighted Average Transaction Response time. The UBE processes workload runs from the JD Enterprise Application server. Oracle's UBE processes come as three flavors: Short UBEs < 1 minute engage in Business Report and Summary Analysis, Mid UBEs > 1 minute create a large report of Account, Balance, and Full Address, Long UBEs > 2 minutes simulate Payroll, Sales Order, night only jobs. The UBE workload generates large numbers of PDF files reports and log files. The UBE Queues are categorized as the QBATCHD, a single threaded queue for large and medium UBEs, and the QPROCESS queue for short UBEs run concurrently. Oracle's UBE process performance metric is Number of Maximum Concurrent UBE processes at transaction rate, UBEs/minute. Key Points and Best Practices Two JD Edwards EnterpriseOne Application Servers, two Oracle WebLogic Servers 11g Release 1 coupled with two Oracle Web Tier HTTP server instances and one Oracle Database 11g Release 2 database on a single SPARC T4-2 server were hosted in separate Oracle Solaris Containers bound to four processor sets to demonstrate consolidation of multiple applications, web servers and the database with best resource utilizations. Interrupt fencing was configured on all Oracle Solaris Containers to channel the interrupts to processors other than the processor sets used for the JD Edwards Application server, Oracle WebLogic servers and the database server. A Oracle WebLogic vertical cluster was configured on each WebServer Container with twelve managed instances each to load balance users' requests and to provide the infrastructure that enables scaling to high number of users with ease of deployment and high availability. The database log writer was run in the real time RT class and bound to a processor set. The database redo logs were configured on the raw disk partitions. The Oracle Solaris Container running the Enterprise Application server completed 61 Short UBEs, 4 Long UBEs concurrently as the mixed size batch workload. The mixed size UBEs ran concurrently from the Enterprise Application server with the 8,000 online users driven by the LoadRunner. See Also SPARC T4-2 Server oracle.com OTN JD Edwards EnterpriseOne oracle.com OTN Oracle Solaris oracle.com OTN Oracle Database 11g Release 2 Enterprise Edition oracle.com OTN Oracle Fusion Middleware oracle.com OTN Disclosure Statement Copyright 2012, Oracle and/or its affiliates. All rights reserved. Oracle and Java are registered trademarks of Oracle and/or its affiliates. Other names may be trademarks of their respective owners. Results as of 09/30/2012.

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  • Danger from the Deep

    <b>Linux Journal:</b> "If you remember my December Linux Journal column, I was excited about a particularly cool-looking submarine simulator, Danger from the Deep. This month, I'm proud to feature it."

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  • Extra fire simulation on iPad device

    - by Nezam
    I have with me an iOS app for iPad which creates a few fire simulations over a png.Well,its working well exactly how we wanted it but when we are testing it on a device,we get an extra fire simulation.Heres the screen: iPad Simulator: This is how it should display (iPad Simulation) iPad Device: This is how its displaying (iPad Device) M ready to share whichever portion of my code which gets me to my solution once someone gets hit here.Thanks in advance

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  • Organization &amp; Architecture UNISA Studies &ndash; Chap 5

    - by MarkPearl
    Learning Outcomes Describe the operation of a memory cell Explain the difference between DRAM and SRAM Discuss the different types of ROM Explain the concepts of a hard failure and a soft error respectively Describe SDRAM organization Semiconductor Main Memory The two traditional forms of RAM used in computers are DRAM and SRAM DRAM (Dynamic RAM) Divided into two technologies… Dynamic Static Dynamic RAM is made with cells that store data as charge on capacitors. The presence or absence of charge in a capacitor is interpreted as a binary 1 or 0. Because capacitors have natural tendency to discharge, dynamic RAM requires periodic charge refreshing to maintain data storage. The term dynamic refers to the tendency of the stored charge to leak away, even with power continuously applied. Although the DRAM cell is used to store a single bit (0 or 1), it is essentially an analogue device. The capacitor can store any charge value within a range, a threshold value determines whether the charge is interpreted as a 1 or 0. SRAM (Static RAM) SRAM is a digital device that uses the same logic elements used in the processor. In SRAM, binary values are stored using traditional flip flop logic configurations. SRAM will hold its data as along as power is supplied to it. Unlike DRAM, no refresh is required to retain data. SRAM vs. DRAM DRAM is simpler and smaller than SRAM. Thus it is more dense and less expensive than SRAM. The cost of the refreshing circuitry for DRAM needs to be considered, but if the machine requires a large amount of memory, DRAM turns out to be cheaper than SRAM. SRAMS are somewhat faster than DRAM, thus SRAM is generally used for cache memory and DRAM is used for main memory. Types of ROM Read Only Memory (ROM) contains a permanent pattern of data that cannot be changed. ROM is non volatile meaning no power source is required to maintain the bit values in memory. While it is possible to read a ROM, it is not possible to write new data into it. An important application of ROM is microprogramming, other applications include library subroutines for frequently wanted functions, System programs, Function tables. A ROM is created like any other integrated circuit chip, with the data actually wired into the chip as part of the fabrication process. To reduce costs of fabrication, we have PROMS. PROMS are… Written only once Non-volatile Written after fabrication Another variation of ROM is the read-mostly memory, which is useful for applications in which read operations are far more frequent than write operations, but for which non volatile storage is required. There are three common forms of read-mostly memory, namely… EPROM EEPROM Flash memory Error Correction Semiconductor memory is subject to errors, which can be classed into two categories… Hard failure – Permanent physical defect so that the memory cell or cells cannot reliably store data Soft failure – Random error that alters the contents of one or more memory cells without damaging the memory (common cause includes power supply issues, etc.) Most modern main memory systems include logic for both detecting and correcting errors. Error detection works as follows… When data is to be read into memory, a calculation is performed on the data to produce a code Both the code and the data are stored When the previously stored word is read out, the code is used to detect and possibly correct errors The error checking provides one of 3 possible results… No errors are detected – the fetched data bits are sent out An error is detected, and it is possible to correct the error. The data bits plus error correction bits are fed into a corrector, which produces a corrected set of bits to be sent out An error is detected, but it is not possible to correct it. This condition is reported Hamming Code See wiki for detailed explanation. We will probably need to know how to do a hemming code – refer to the textbook (pg. 188 – 189) Advanced DRAM organization One of the most critical system bottlenecks when using high-performance processors is the interface to main memory. This interface is the most important pathway in the entire computer system. The basic building block of main memory remains the DRAM chip. In recent years a number of enhancements to the basic DRAM architecture have been explored, and some of these are now on the market including… SDRAM (Synchronous DRAM) DDR-DRAM RDRAM SDRAM (Synchronous DRAM) SDRAM exchanges data with the processor synchronized to an external clock signal and running at the full speed of the processor/memory bus without imposing wait states. SDRAM employs a burst mode to eliminate the address setup time and row and column line precharge time after the first access In burst mode a series of data bits can be clocked out rapidly after the first bit has been accessed SDRAM has a multiple bank internal architecture that improves opportunities for on chip parallelism SDRAM performs best when it is transferring large blocks of data serially There is now an enhanced version of SDRAM known as double data rate SDRAM or DDR-SDRAM that overcomes the once-per-cycle limitation of SDRAM

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  • Polite busy-waiting with WRPAUSE on SPARC

    - by Dave
    Unbounded busy-waiting is an poor idea for user-space code, so we typically use spin-then-block strategies when, say, waiting for a lock to be released or some other event. If we're going to spin, even briefly, then we'd prefer to do so in a manner that minimizes performance degradation for other sibling logical processors ("strands") that share compute resources. We want to spin politely and refrain from impeding the progress and performance of other threads — ostensibly doing useful work and making progress — that run on the same core. On a SPARC T4, for instance, 8 strands will share a core, and that core has its own L1 cache and 2 pipelines. On x86 we have the PAUSE instruction, which, naively, can be thought of as a hardware "yield" operator which temporarily surrenders compute resources to threads on sibling strands. Of course this helps avoid intra-core performance interference. On the SPARC T2 our preferred busy-waiting idiom was "RD %CCR,%G0" which is a high-latency no-nop. The T4 provides a dedicated and extremely useful WRPAUSE instruction. The processor architecture manuals are the authoritative source, but briefly, WRPAUSE writes a cycle count into the the PAUSE register, which is ASR27. Barring interrupts, the processor then delays for the requested period. There's no need for the operating system to save the PAUSE register over context switches as it always resets to 0 on traps. Digressing briefly, if you use unbounded spinning then ultimately the kernel will preempt and deschedule your thread if there are other ready threads than are starving. But by using a spin-then-block strategy we can allow other ready threads to run without resorting to involuntary time-slicing, which operates on a long-ish time scale. Generally, that makes your application more responsive. In addition, by blocking voluntarily we give the operating system far more latitude regarding power management. Finally, I should note that while we have OS-level facilities like sched_yield() at our disposal, yielding almost never does what you'd want or naively expect. Returning to WRPAUSE, it's natural to ask how well it works. To help answer that question I wrote a very simple C/pthreads benchmark that launches 8 concurrent threads and binds those threads to processors 0..7. The processors are numbered geographically on the T4, so those threads will all be running on just one core. Unlike the SPARC T2, where logical CPUs 0,1,2 and 3 were assigned to the first pipeline, and CPUs 4,5,6 and 7 were assigned to the 2nd, there's no fixed mapping between CPUs and pipelines in the T4. And in some circumstances when the other 7 logical processors are idling quietly, it's possible for the remaining logical processor to leverage both pipelines. Some number T of the threads will iterate in a tight loop advancing a simple Marsaglia xor-shift pseudo-random number generator. T is a command-line argument. The main thread loops, reporting the aggregate number of PRNG steps performed collectively by those T threads in the last 10 second measurement interval. The other threads (there are 8-T of these) run in a loop busy-waiting concurrently with the T threads. We vary T between 1 and 8 threads, and report on various busy-waiting idioms. The values in the table are the aggregate number of PRNG steps completed by the set of T threads. The unit is millions of iterations per 10 seconds. For the "PRNG step" busy-waiting mode, the busy-waiting threads execute exactly the same code as the T worker threads. We can easily compute the average rate of progress for individual worker threads by dividing the aggregate score by the number of worker threads T. I should note that the PRNG steps are extremely cycle-heavy and access almost no memory, so arguably this microbenchmark is not as representative of "normal" code as it could be. And for the purposes of comparison I included a row in the table that reflects a waiting policy where the waiting threads call poll(NULL,0,1000) and block in the kernel. Obviously this isn't busy-waiting, but the data is interesting for reference. _table { border:2px black dotted; margin: auto; width: auto; } _tr { border: 2px red dashed; } _td { border: 1px green solid; } _table { border:2px black dotted; margin: auto; width: auto; } _tr { border: 2px red dashed; } td { background-color : #E0E0E0 ; text-align : right ; } th { text-align : left ; } td { background-color : #E0E0E0 ; text-align : right ; } th { text-align : left ; } Aggregate progress T = #worker threads Wait Mechanism for 8-T threadsT=1T=2T=3T=4T=5T=6T=7T=8 Park thread in poll() 32653347334833483348334833483348 no-op 415 831 124316482060249729303349 RD %ccr,%g0 "pause" 14262429269228623013316232553349 PRNG step 412 829 124616702092251029303348 WRPause(8000) 32443361333133483349334833483348 WRPause(4000) 32153308331533223347334833473348 WRPause(1000) 30853199322432513310334833483348 WRPause(500) 29173070315032223270330933483348 WRPause(250) 26942864294930773205338833483348 WRPause(100) 21552469262227902911321433303348

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  • Dealing with state problems in functional programming

    - by Andrew Martin
    I've learned how to program primarily from an OOP standpoint (like most of us, I'm sure), but I've spent a lot of time trying to learn how to solve problems the functional way. I have a good grasp on how to solve calculational problems with FP, but when it comes to more complicated problems I always find myself reverting to needing mutable objects. For example, if I'm writing a particle simulator, I will want particle "objects" with a mutable position to update. How are inherently "stateful" problems typically solved using functional programming techniques?

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  • want to build a replica of chartgame.com

    - by raj
    I want to develop a trading simulator based on technical analysis. my ideal application would exactly be chartgame.com currently chartgame.com doesnt have historical data for stocks beyond the year 2008 and I would like to have data until 2012 and have the capability to extend beyond if needed. what are the fundamentals to build an application like chartgame.com. If anyone here is willing to help I can arrange for the finances.let me know.

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  • Implementing traffic conditions in TORCS

    - by user1837811
    I am working on a project about "Effects of Traffic conditions and Track Complexity on Car Driving Behavior". Is it possible to implement traffic in TORCS, or should I use another car simulator? By the word "traffic" I mean there are cars running on both tracks in both directions and I can detect the distances, direction and speed of these cars. Depending on this information I can decide whether I should slow down, speed up and calculate the correct timing to overtake.

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