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• Various problems with software raid1 array built with Samsung 840 Pro SSDs

  - by Andy B

  I am bringing to ServerFault a problem that is tormenting me for 6+ months. I have a CentOS 6 (64bit) server with an md software raid-1 array with 2 x Samsung 840 Pro SSDs (512GB). Problems: Serious write speed problems: root [~]# time dd if=arch.tar.gz of=test4 bs=2M oflag=sync 146+1 records in 146+1 records out 307191761 bytes (307 MB) copied, 23.6788 s, 13.0 MB/s real 0m23.680s user 0m0.000s sys 0m0.932s When doing the above (or any other larger copy) the load spikes to unbelievable values (even over 100) going up from ~ 1. When doing the above I've also noticed very weird iostat results: Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util sda 0.00 1589.50 0.00 54.00 0.00 13148.00 243.48 0.60 11.17 0.46 2.50 sdb 0.00 1627.50 0.00 16.50 0.00 9524.00 577.21 144.25 1439.33 60.61 100.00 md1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 md2 0.00 0.00 0.00 1602.00 0.00 12816.00 8.00 0.00 0.00 0.00 0.00 md0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 And it keeps it this way until it actually writes the file to the device (out from swap/cache/memory). The problem is that the second SSD in the array has svctm and await roughly 100 times larger than the second. For some reason the wear is different between the 2 members of the array root [~]# smartctl --attributes /dev/sda | grep -i wear 177 Wear_Leveling_Count 0x0013 094% 094 000 Pre-fail Always - 180 root [~]# smartctl --attributes /dev/sdb | grep -i wear 177 Wear_Leveling_Count 0x0013 070% 070 000 Pre-fail Always - 1005 The first SSD has a wear of 6% while the second SSD has a wear of 30%!! It's like the second SSD in the array works at least 5 times as hard as the first one as proven by the first iteration of iostat (the averages since reboot): Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util sda 10.44 51.06 790.39 125.41 8803.98 1633.11 11.40 0.33 0.37 0.06 5.64 sdb 9.53 58.35 322.37 118.11 4835.59 1633.11 14.69 0.33 0.76 0.29 12.97 md1 0.00 0.00 1.88 1.33 15.07 10.68 8.00 0.00 0.00 0.00 0.00 md2 0.00 0.00 1109.02 173.12 10881.59 1620.39 9.75 0.00 0.00 0.00 0.00 md0 0.00 0.00 0.41 0.01 3.10 0.02 7.42 0.00 0.00 0.00 0.00 What I've tried: I've updated the firmware to DXM05B0Q (following reports of dramatic improvements for 840Ps after this update). I have looked for "hard resetting link" in dmesg to check for cable/backplane issues but nothing. I have checked the alignment and I believe they are aligned correctly (1MB boundary, listing below) I have checked /proc/mdstat and the array is Optimal (second listing below). root [~]# fdisk -ul /dev/sda Disk /dev/sda: 512.1 GB, 512110190592 bytes 255 heads, 63 sectors/track, 62260 cylinders, total 1000215216 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00026d59 Device Boot Start End Blocks Id System /dev/sda1 2048 4196351 2097152 fd Linux raid autodetect Partition 1 does not end on cylinder boundary. /dev/sda2 * 4196352 4605951 204800 fd Linux raid autodetect Partition 2 does not end on cylinder boundary. /dev/sda3 4605952 814106623 404750336 fd Linux raid autodetect root [~]# fdisk -ul /dev/sdb Disk /dev/sdb: 512.1 GB, 512110190592 bytes 255 heads, 63 sectors/track, 62260 cylinders, total 1000215216 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x0003dede Device Boot Start End Blocks Id System /dev/sdb1 2048 4196351 2097152 fd Linux raid autodetect Partition 1 does not end on cylinder boundary. /dev/sdb2 * 4196352 4605951 204800 fd Linux raid autodetect Partition 2 does not end on cylinder boundary. /dev/sdb3 4605952 814106623 404750336 fd Linux raid autodetect /proc/mdstat root # cat /proc/mdstat Personalities : [raid1] md0 : active raid1 sdb2[1] sda2[0] 204736 blocks super 1.0 [2/2] [UU] md2 : active raid1 sdb3[1] sda3[0] 404750144 blocks super 1.0 [2/2] [UU] md1 : active raid1 sdb1[1] sda1[0] 2096064 blocks super 1.1 [2/2] [UU] unused devices: Running a read test with hdparm root [~]# hdparm -t /dev/sda /dev/sda: Timing buffered disk reads: 664 MB in 3.00 seconds = 221.33 MB/sec root [~]# hdparm -t /dev/sdb /dev/sdb: Timing buffered disk reads: 288 MB in 3.01 seconds = 95.77 MB/sec But look what happens if I add --direct root [~]# hdparm --direct -t /dev/sda /dev/sda: Timing O_DIRECT disk reads: 788 MB in 3.01 seconds = 262.08 MB/sec root [~]# hdparm --direct -t /dev/sdb /dev/sdb: Timing O_DIRECT disk reads: 534 MB in 3.02 seconds = 176.90 MB/sec Both tests increase but /dev/sdb doubles while /dev/sda increases maybe 20%. I just don't know what to make of this. As suggested by Mr. Wagner I've done another read test with dd this time and it confirms the hdparm test: root [/home2]# dd if=/dev/sda of=/dev/null bs=1G count=10 10+0 records in 10+0 records out 10737418240 bytes (11 GB) copied, 38.0855 s, 282 MB/s root [/home2]# dd if=/dev/sdb of=/dev/null bs=1G count=10 10+0 records in 10+0 records out 10737418240 bytes (11 GB) copied, 115.24 s, 93.2 MB/s So sda is 3 times faster than sdb. Or maybe sdb is doing also something else besides what sda does. Is there some way to find out if sdb is doing more than what sda does? UPDATE Again, as suggested by Mr. Wagner, I have swapped the 2 SSDs. And as he thought it would happen, the problem moved from sdb to sda. So I guess I'll RMA one of the SSDs. I wonder if the cage might be problematic. What is wrong with this array? Please help!

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• Considerations Before Hiring Logo Design Services

  These days, hiring a logo design service is not easy. Just enter a keyword "logo design" in a search engine and you will see thousands of result pages full of online logo design services. Certainly, ... [Author: Gisselle Gloria - Web Design and Development - October 05, 2009]

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• How do I list installed software with the installed size?

  - by Lewis Goddard

  I would like to have a list the installed software on my machine, with the disk space consumed by them alongside. I would prefer to be able to order by largest/smallest, but that is not a necessity. I am the sort of person who will install software to try it, and never clean up after myself. As a result, my 7GB (Windows and my Data are on separate partitions, as well as a swap area) Ubuntu 11.04 partition is suffering, and has started regularly showing warning messages. I have cleaned my browser cache, as well as everything under Package Cleaner in Ubuntu Tweak, and am left with 149.81 MB off free space.

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• Any suggestions how it would be good to promote software in a small company ?

  - by Derfder

  Ok, I know if I am Red hat or other giant and offer some support etc. I can be profitable, in fact, Red Hat is doing quite well. However, what about a small company where I create a small program. e.g. an instant messenger for a windows or linux (just as an illustration) and I want to sell it. But how can I sell it if it is free and everybody can download it? Any advice? I like the idea of FSF by Richard Stallman, however I am missing the way how to sell my software under GNU/GPL licence. Any advice, how can I solve this problem? Any profitable small business software developers around with their opinion? Any links or names of small companies taht I can look at and study their model of business?

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• What do I need to do, to get placed in any software company?

  - by Anto Aravinth

  I'm doing my 3rd year CSE Engineering. I guess this is the right time to ask this question! As in the next year, I'm going to do projects, "get my hands dirty". And there is only few days left out, as I know many people in Stack Overflow are working in Software field, I thought to ask these question. Does the project that I'm doing in my final year need to be excellent? If so, what kind of project to do? And how do you say that the project is excellent or not? Writing the code is very fun and serious at times. But the code should have a good algorithm? And mostly in any software companies interview, what kind of question they ask? Not but not the least, mastering in any particular language speaks in interviews?

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• SQL Rally Relational Database Design Pre-Con Preview

  - by drsql

  On May 9, 2012, I will be presenting a pre-con session at the SQL Rally in Dallas, TX on relational database design. The fact is, database design is a topic that demands more than a simple one hour session to really do it right. So in my Relational Database Design Workshop, we will have seven times the amount of time in the typical session, giving us time to cover our topics in a bit more detail, look at a lot more designs/code, and even get some time to do some design as a group. Our topics will...(read more)

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• How Can Someone With Minimum Programming Experience Publish an App of an Existing Program not found in the Software Centre?

  - by Brenton Horne

  There's a free mathematics software that I would like to see in Ubuntu Software Centre, called, 'Sage.' I have minimal experience in programming, so I'm basically here asking if someone could either tell me how to accomplish this without said instructions being completely over my head or if someone could do it for me. For further information here's the sage homepage: http://sagemath.org/ and the .tar.lzma file for its installation is ~500MB and it takes around 2.2 GB on the HDD when installed, I found at least on 32 bit i386 Ubuntu 12.04 LTS. Any help will be greatly appreciated!

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• What is the worst software bug in history? [closed]

  - by Amir Rezaei

  By having for example money and human suffering as the metric. What is the worst software bug in history? Note this is a specific question. Last month automaker Toyota announced a recall of 160,000 of its Prius hybrid vehicles following reports of vehicle warning lights illuminating for no reason, and cars' gasoline engines stalling unexpectedly. But unlike the large-scale auto recalls of years past, the root of the Prius issue wasn't a hardware problem -- it was a programming error in the smart car's embedded code. The Prius had a software bug.

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• Cross-Cultural Design (great video from HFI) - #usableapps #UX #L10n

  - by ultan o'broin

  Great video from HFI Animate, featuring user-centered design for emerging markets called Cross Cultural Design: Getting It Right the First Time. Cross Cultural Design: Getting It Right the First Time Apala Lahiri Chavan talks about the issues involved in designing solutions for Africa, India, China and more markets! Design for the local customer's ecosystem - and their feelings! Timely reminder of the important of global and local research in UX!

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• One man software developer product success stories? [on hold]

  - by EugeneKr

  I've got a bad feeling that this question is not appropriate here.. Hopefully you can point me to the right place to ask such a thing (not google though, been there). I want to create my own product, but for some reason have no ideas, so decided to see what people have already done. I would like to start by myself too. I don't mind expanding, but at later stages when it is absolutely necessary. Anyway, to give you an example. There is a guy who created bingo card generation software, then somebody made a wedding planner software and they seem to be doing pretty fine. I would like to know more such cases to draw inspiration from. Do you know such people or maybe you are one of them? Also, if there are places on the net where they dwell, don't hesitate to tell me :) Thanks!

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• Software Center won't take into account my changed OpenID name: any idea?

  - by Pascal Av

  Failing to install IntelliJ from the Software Center, I realized my login is wrong in the /etc/apt/auth.conf entry that the install process generates. In this file, I see my original OpenID, that's the one which got automatically generated when signing up on Launchpad. It contains my last name so I changed it. I purged conf and binaries for Ubuntu One, reinstalled, deleted all listed "Devices" from app, all "Applications" from Launchpad. Deleted ~/.cache/software-center/, reboot, but still: When installing IntelliJ, the auth.conf file receives my original OpenID, not the modified one Problem is that the commercial subscription, for IntelliJ private PPA, uses my modified OpenID, so authentication attempt fails. I can't remove nor modify this subscription, even by changing back my OpenID into Launchpad. Any idea to solve this?

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• Where does Ubuntu Software Center store its (language) settings?

  - by guntbert

  On a fresh install (13.04) I see a strange mix of languages in Software Center The menu (like my system language) is in English, but the descriptions are in German. I want the descriptions in English too. I am using a german keyboard and have German installed too (for giving support to students with German as system language :-)) In system settings I have moved German below English - so it should be ignored, I have logged out after that. I have cleared the "Software Center Cache" with Ubuntu Tweak. The picture remains the same.

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• Software Design and documentation – what do people use that has proved valuable?

  - by eddyparkinson

  When creating software, what do you use to design, document and visualize. Looking for evidence/examples. e.g. Use cases, Pseudo code, Gantt chats, PERT charts, DFD, decision trees, decision tables (Answers maybe used to help teach students) What do you use to help with creating software. Also why; when has it proved valuable? --- Edit -- Proved valuable: The pattern so far suggests that the style of UML tool used is linked to an objective. e.g. "get it straight in MY head", explain to business mangers, quality control.

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• Should I install programs from a source tarball (`.tar.gz`), from the Ubuntu Software Centre, or from elsewhere?

  - by Flimm

  There are several ways to install an application in Ubuntu: You can download a source tarball (generally a .tar.gz or a .tar.bz2 file) and install it manually. (See How to install a .tar.gz (or .tar.bz2) file?) You can download a .deb file and install it manually, using dpkg or the Software Centre. You can search for the application in the Ubuntu Software Centre and install it there, or use apt with the official Ubuntu repositories. You can find a PPA or a third-party repo, and install it from there. What are the pros and cons of each method? Please discuss security implications, frequency of updates and program reliability of each method in your answer.

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• .net design pattern question

  - by user359562

  Hi. I am trying to understand design pattern problems. I am trying to modify the code like this in winforms and trying to see if any design pattern suits my requirement. Please suggest which is the best design pattern in this scenario. This is very basic code containing 2 tab pages which might have different controls can be added dynamically and read out different files on click of particular tab. To elaborate more... I have written this code to learn and understand design pattern. This is just a scenario where user click on a particular tab which will show dynamic controls generated. public partial class Form1 : Form { public Form1() { InitializeComponent(); } private void tabControl1_SelectedIndexChanged(object sender, EventArgs e) { if (tabControl1.SelectedTab.Name.Equals("tabPage1")) { GeneratedynamicControlsForTab1(); } else if (tabControl1.SelectedTab.Name.Equals("tabPage2")) { GeneratedynamicControlsForTab2(); } } private void GeneratedynamicControlsForTab1() { Label label1 = new Label(); label1.Text = "Label1"; tabPage1.Controls.Add(label1); ReadCSVFile(); } private void GeneratedynamicControlsForTab2() { tabPage1.Controls.Clear(); Label label2 = new Label(); label2.Text = "Label2"; tabPage2.Controls.Add(label2); ReadTextFile(); } private void ReadCSVFile() { } private void ReadTextFile() { } }

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• Are there design patterns or generalised approaches for particle simulations?

  - by romeovs

  I'm working on a project (for college) in C++. The goal is to write a program that can more or less simulate a beam of particles flying trough the LHC synchrotron. Not wanting to rush into things, me and my team are thinking about how to implement this and I was wondering if there are general design patterns that are used to solve this kind of problem. The general approach we came up with so far is the following: there is a World that holds all objects you can add objects to this world such as Particle, Dipole and Quadrupole time is cut up into discrete steps, and at each point in time, for each Particle the magnetic and electric forces that each object in the World generates are calculated and summed up (luckily electro-magnetism is linear). each Particle moves accordingly (using a simple estimation approach to solve the differential movement equations) save the Particle positions repeat This seems a good approach but, for instance, it is hard to take into account symmetries that might be present (such as the magnetic field of each Quadrupole) and is this thus suboptimal. To take into account such symmetries as that of the Quadrupole field, it would be much easier to (also) make space discrete and somehow store form of the Quadrupole field somewhere. (Since 2532 or so Quadrupoles are stored this should lead to a massive gain of performance, not having to recalculate each Quadrupole field) So, are there any design patterns? Is the World-approach feasible or is it old-fashioned, bad programming? What about symmetry, how is that generally taken into acount?

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• Are Java's public fields just a tragic historical design flaw at this point?

  - by Avi Flax

  It seems to be Java orthodoxy at this point that one should basically never use public fields for object state. (I don't necessarily agree, but that's not relevant to my question.) Given that, would it be right to say that from where we are today, it's clear that Java's public fields were a mistake/flaw of the language design? Or is there a rational argument that they're a useful and important part of the language, even today? Thanks! Update: I know about the more elegant approaches, such as in C#, Python, Groovy, etc. I'm not directly looking for those examples. I'm really just wondering if there's still someone deep in a bunker, muttering about how wonderful public fields really are, and how the masses are all just sheep, etc. Update 2: Clearly static final public fields are the standard way to create public constants. I was referring more to using public fields for object state (even immutable state). I'm thinking that it does seem like a design flaw that one should use public fields for constants, but not for state… a language's rules should be enforced naturally, by syntax, not by guidelines.

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• Interface (contract), Generics (universality), and extension methods (ease of use). Is it a right design?

  - by Saeed Neamati

  I'm trying to design a simple conversion framework based on these requirements: All developers should follow a predefined set of rules to convert from the source entity to the target entity Some overall policies should be able to be applied in a central place, without interference with developers' code Both the creation of converters and usage of converter classes should be easy To solve these problems in C# language, A thought came to my mind. I'm writing it here, though it doesn't compile at all. But let's assume that C# compiles this code: I'll create a generic interface called IConverter public interface IConverter<TSource, TTarget> where TSource : class, new() where TTarget : class, new() { TTarget Convert(TSource source); List<TTarget> Convert(List<TSource> sourceItems); } Developers would implement this interface to create converters. For example: public class PhoneToCommunicationChannelConverter : IConverter<Phone, CommunicationChannle> { public CommunicationChannel Convert(Phone phone) { // conversion logic } public List<CommunicationChannel> Convert(List<Phone> phones) { // conversion logic } } And to make the usage of this conversion class easier, imagine that we add static and this keywords to methods to turn them into Extension Methods, and use them this way: List<Phone> phones = GetPhones(); List<CommunicationChannel> channels = phones.Convert(); However, this doesn't even compile. With those requirements, I can think of some other designs, but they each lack an aspect. Either the implementation would become more difficult or chaotic and out of control, or the usage would become truly hard. Is this design right at all? What alternatives I might have to achieve those requirements?

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• What single piece of software do you most admire, and why?

  - by Burton

  As a developer, I too often find fault with the software that I use day to day. Unintuitive interfaces, etc. But there are those rare exceptions. Regardless of whether the software in question is a programmers' tool, tell me about software you have used: What has inspired admiration? What software made you re-remember simplicity? (or whatever gauge of awesomeness works for you). Only one piece of software per post, please.

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• Abstracting functionality

  - by Ralf Westphal

  Originally posted on: http://geekswithblogs.net/theArchitectsNapkin/archive/2014/08/22/abstracting-functionality.aspxWhat is more important than data? Functionality. Yes, I strongly believe we should switch to a functionality over data mindset in programming. Or actually switch back to it. Focus on functionality Functionality once was at the core of software development. Back when algorithms were the first thing you heard about in CS classes. Sure, data structures, too, were important - but always from the point of view of algorithms. (Niklaus Wirth gave one of his books the title “Algorithms + Data Structures” instead of “Data Structures + Algorithms” for a reason.) The reason for the focus on functionality? Firstly, because software was and is about doing stuff. Secondly because sufficient performance was hard to achieve, and only thirdly memory efficiency. But then hardware became more powerful. That gave rise to a new mindset: object orientation. And with it functionality was devalued. Data took over its place as the most important aspect. Now discussions revolved around structures motivated by data relationships. (John Beidler gave his book the title “Data Structures and Algorithms: An Object Oriented Approach” instead of the other way around for a reason.) Sure, this data could be embellished with functionality. But nevertheless functionality was second. When you look at (domain) object models what you mostly find is (domain) data object models. The common object oriented approach is: data aka structure over functionality. This is true even for the most modern modeling approaches like Domain Driven Design. Look at the literature and what you find is recommendations on how to get data structures right: aggregates, entities, value objects. I´m not saying this is what object orientation was invented for. But I´m saying that´s what I happen to see across many teams now some 25 years after object orientation became mainstream through C++, Delphi, and Java. But why should we switch back? Because software development cannot become truly agile with a data focus. The reason for that lies in what customers need first: functionality, behavior, operations. To be clear, that´s not why software is built. The purpose of software is to be more efficient than the alternative. Money mainly is spent to get a certain level of quality (e.g. performance, scalability, security etc.). But without functionality being present, there is nothing to work on the quality of. What customers want is functionality of a certain quality. ASAP. And tomorrow new functionality needs to be added, existing functionality needs to be changed, and quality needs to be increased. No customer ever wanted data or structures. Of course data should be processed. Data is there, data gets generated, transformed, stored. But how the data is structured for this to happen efficiently is of no concern to the customer. Ask a customer (or user) whether she likes the data structured this way or that way. She´ll say, “I don´t care.” But ask a customer (or user) whether he likes the functionality and its quality this way or that way. He´ll say, “I like it” (or “I don´t like it”). Build software incrementally From this very natural focus of customers and users on functionality and its quality follows we should develop software incrementally. That´s what Agility is about. Deliver small increments quickly and often to get frequent feedback. That way less waste is produced, and learning can take place much easier (on the side of the customer as well as on the side of developers). An increment is some added functionality or quality of functionality.[1] So as it turns out, Agility is about functionality over whatever. But software developers’ thinking is still stuck in the object oriented mindset of whatever over functionality. Bummer. I guess that (at least partly) explains why Agility always hits a glass ceiling in projects. It´s a clash of mindsets, of cultures. Driving software development by demanding small increases in functionality runs against thinking about software as growing (data) structures sprinkled with functionality. (Excuse me, if this sounds a bit broad-brush. But you get my point.) The need for abstraction In the end there need to be data structures. Of course. Small and large ones. The phrase functionality over data does not deny that. It´s not functionality instead of data or something. It´s just over, i.e. functionality should be thought of first. It´s a tad more important. It´s what the customer wants. That´s why we need a way to design functionality. Small and large. We need to be able to think about functionality before implementing it. We need to be able to reason about it among team members. We need to be able to communicate our mental models of functionality not just by speaking about them, but also on paper. Otherwise reasoning about it does not scale. We learned thinking about functionality in the small using flow charts, Nassi-Shneiderman diagrams, pseudo code, or UML sequence diagrams. That´s nice and well. But it does not scale. You can use these tools to describe manageable algorithms. But it does not work for the functionality triggered by pressing the “1-Click Order” on an amazon product page for example. There are several reasons for that, I´d say. Firstly, the level of abstraction over code is negligible. It´s essentially non-existent. Drawing a flow chart or writing pseudo code or writing actual code is very, very much alike. All these tools are about control flow like code is.[2] In addition all tools are computationally complete. They are about logic which is expressions and especially control statements. Whatever you code in Java you can fully (!) describe using a flow chart. And then there is no data. They are about control flow and leave out the data altogether. Thus data mostly is assumed to be global. That´s shooting yourself in the foot, as I hope you agree. Even if it´s functionality over data that does not mean “don´t think about data”. Right to the contrary! Functionality only makes sense with regard to data. So data needs to be in the picture right from the start - but it must not dominate the thinking. The above tools fail on this. Bottom line: So far we´re unable to reason in a scalable and abstract manner about functionality. That´s why programmers are so driven to start coding once they are presented with a problem. Programming languages are the only tool they´ve learned to use to reason about functional solutions. Or, well, there might be exceptions. Mathematical notation and SQL may have come to your mind already. Indeed they are tools on a higher level of abstraction than flow charts etc. That´s because they are declarative and not computationally complete. They leave out details - in order to deliver higher efficiency in devising overall solutions. We can easily reason about functionality using mathematics and SQL. That´s great. Except for that they are domain specific languages. They are not general purpose. (And they don´t scale either, I´d say.) Bummer. So to be more precise we need a scalable general purpose tool on a higher than code level of abstraction not neglecting data. Enter: Flow Design. Abstracting functionality using data flows I believe the solution to the problem of abstracting functionality lies in switching from control flow to data flow. Data flow very naturally is not about logic details anymore. There are no expressions and no control statements anymore. There are not even statements anymore. Data flow is declarative by nature. With data flow we get rid of all the limiting traits of former approaches to modeling functionality. In addition, nomen est omen, data flows include data in the functionality picture. With data flows, data is visibly flowing from processing step to processing step. Control is not flowing. Control is wherever it´s needed to process data coming in. That´s a crucial difference and needs some rewiring in your head to be fully appreciated.[2] Since data flows are declarative they are not the right tool to describe algorithms, though, I´d say. With them you don´t design functionality on a low level. During design data flow processing steps are black boxes. They get fleshed out during coding. Data flow design thus is more coarse grained than flow chart design. It starts on a higher level of abstraction - but then is not limited. By nesting data flows indefinitely you can design functionality of any size, without losing sight of your data. Data flows scale very well during design. They can be used on any level of granularity. And they can easily be depicted. Communicating designs using data flows is easy and scales well, too. The result of functional design using data flows is not algorithms (too low level), but processes. Think of data flows as descriptions of industrial production lines. Data as material runs through a number of processing steps to be analyzed, enhances, transformed. On the top level of a data flow design might be just one processing step, e.g. “execute 1-click order”. But below that are arbitrary levels of flows with smaller and smaller steps. That´s not layering as in “layered architecture”, though. Rather it´s a stratified design à la Abelson/Sussman. Refining data flows is not your grandpa´s functional decomposition. That was rooted in control flows. Refining data flows does not suffer from the limits of functional decomposition against which object orientation was supposed to be an antidote. Summary I´ve been working exclusively with data flows for functional design for the past 4 years. It has changed my life as a programmer. What once was difficult is now easy. And, no, I´m not using Clojure or F#. And I´m not a async/parallel execution buff. Designing the functionality of increments using data flows works great with teams. It produces design documentation which can easily be translated into code - in which then the smallest data flow processing steps have to be fleshed out - which is comparatively easy. Using a systematic translation approach code can mirror the data flow design. That way later on the design can easily be reproduced from the code if need be. And finally, data flow designs play well with object orientation. They are a great starting point for class design. But that´s a story for another day. To me data flow design simply is one of the missing links of systematic lightweight software design. There are also other artifacts software development can produce to get feedback, e.g. process descriptions, test cases. But customers can be delighted more easily with code based increments in functionality. ? No, I´m not talking about the endless possibilities this opens for parallel processing. Data flows are useful independently of multi-core processors and Actor-based designs. That´s my whole point here. Data flows are good for reasoning and evolvability. So forget about any special frameworks you might need to reap benefits from data flows. None are necessary. Translating data flow designs even into plain of Java is possible. ?

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• Winforms Which Design Pattern / Agile Methodology to choose

  - by ZedBee

  I have developed desktop (winforms) applications without following any proper design pattern or agile methodologies. Now I have been given the task to re-write an existing ERP application in C# (Winforms). I have been reading about Domain Driven Design, scrum, extreme programming, layered architecture etc. Its quite confusing and really hard (because of time limitations) to go and try each and every method and then deciding which way to go. Its very hard for me to understand the bigger picture and see which pattern and agile methodology to follow. To be more specific about what I want to know is that: Is it possible to follow Domain Driven Design and still be agile. Should I choose Extreme programming or scrum in this specific scenario Where does MVP and MVVM fits, which one would be a better option for me

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• What design patterns are used in diagramming tools?

  - by TheMachineCharmer

  Diagram.net is good diagramming tool. I need to understand what design patterns are used by this tool so that I can understand how it works. What design patterns are used in this tool? What design patterns are generally used for diagramming tools? I would also like to know how can I use this to develop very simple diagramming tool (Only rectangular nodes and straight links). NOTE/Caution: I am doing this for FUN so please don't direct me to existing tools(I might down vote.. just kiddin ;).

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• android call log like design

  - by Alxandr

  I'm trying to create a design for a list that looks like (and mostly behaves like) the call log, like shown here: I don't need all the design, but what I'm trying to achieve is the two-columned design with the splitter in-between, and the behavior that if I click on the main item (the left part) one thing happens (in this case, you open some details about the call), and if you press the outer right part something else happens (you call the contact). I'm pretty new to android, but I've managed to do most of the designs I wanted so far, so I don't need the entire layout for this one, only the part that does the splitting and the splitter. And if possible it would be nice to know how to map the clicks appropriately, though I think I might be able to find that out by my self.

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• View centric design with Django

  - by wishi_

  Hi! I'm relatively new to Django and I'm designing a website that primarily needs usability experience, speaking of optimized CSS, HTML5 and UI stuff. It's very easy to use Django for data/Model centric design. Just designing a couple of Python classes and ./manage.py syncdb - there's your Model. But I'm dealing with a significant amount of View centric challenges. (Different user classes, different tasks, different design challenges.) The official Django tutorial cursorily goes through using a "Template". Is there any Design centric guide for Django, or a set of Templates that are ready and useable? I don't want to start from scratch using JS, HTML5, Ajax and everything. From the Model layer perspective Django is very rapid and delivering a working base system. I wonder whether there's something like that for the Views.

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• Alternative design for a synonyms table?

  - by Majid

  I am working on an app which is to suggest alternative words/phrases for input text. I have doubts about what might be a good design for the synonyms table. Design considerations: number of synonyms is variable, i.e. football has one synonym (soccer), but in particular has two (particularly, specifically) if football is a synonym to soccer, the relation exists in the opposite direction as well. our goal is to query a word and find its synonyms we want to keep the table small and make adding new words easy What comes to my mind is a two column design with col a = word and col b = delimited list of synonyms Is there any better alternative? What about using two tables, one for words and the other for relations?

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