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  • How should I describe the process of learning someone else's code? (In an invoicing situation.)

    - by MattyG
    I have a contract to upgrade some in-house software for a large company. The company has requested multiple feature additions and a few bug fixes. This is my first freelance style job. First, I needed to become familiar with how the application worked - I learnt it as if I was a user. Next, I had to learn how the software worked. I started with broad concepts, and then narrowed down into necessary detail before working on each bug fix and feature. At least at the start of the project, it took me a lot longer to learn the existing code than it did to write the additional features. How can I describe the process of learning the existing code on the invoice? (This part of the company usually does things in-house, so doesn't have much experience dealing with software contractors like me, and I fear they may not understand the overhead of learning someone else's code). I don't want to just tack the learning time onto the actual feature upgrade, because in some cases this would make a 'simple task' look like it took me way too long. I want break the invoice into relevant steps, and communicate that I'm charging for the large overhead of learning someone else's code before being able to add my own to it. Is there a standard way of describing this sort of activity when billing for a job?

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  • How to handle monetary values in PHP and MySql?

    - by Songo
    I've inherited a huge pile of legacy code written in PHP on top of a MySQL database. The thing I noticed is that the application uses doubles for storage and manipulation of data. Now I came across of numerous posts mentioning how double are not suited for monetary operations because of the rounding errors. However, I have yet to come across a complete solution to how monetary values should be handled in PHP code and stored in a MySQL database. Is there a best practice when it comes to handling money specifically in PHP? Things I'm looking for are: How should the data be stored in the database? column type? size? How should the data be handling in normal addition, subtraction. multiplication or division? When should I round the values? How much rounding is acceptable if any? Is there a difference between handling large monetary values and low ones? Note: A VERY simplified sample code of how I might encounter money values in everyday life: $a= $_POST['price_in_dollars']; //-->(ex: 25.06) will be read as a string should it be cast to double? $b= $_POST['discount_rate'];//-->(ex: 0.35) value will always be less than 1 $valueToBeStored= $a * $b; //--> any hint here is welcomed $valueFromDatabase= $row['price']; //--> price column in database could be double, decimal,...etc. $priceToPrint=$valueFromDatabase * 0.25; //again cast needed or not? I hope you use this sample code as a means to bring out more use cases and not to take it literally of course. Bonus Question If I'm to use an ORM such as Doctrine or PROPEL, how different will it be to use money in my code.

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  • Ubiquitous Language and Custom types

    - by EdvRusj
    Note that my question is referring to those attributes that even on their own already represent a concept ( ie on their own provide a cohesive meaning ). Thus such attribute needs no additional functional support and as such is self-contained. I'm also well-aware that even with self-contained attributes the custom types may prove beneficial ( for example, they give the ability to add new behavior later, when business requirements change ). Thus, my question focuses only on whether custom types for self-contained attributes really enrich Ubiquitous Language UL a) I've read that in most cases, even simple, self-contained attributes should have custom, more descriptive types rather than basic value types ( double, string ... ), because among other things, descriptive types add to the UL, while the use of basic types instead weakens the language. I understand the importance of UL, but how does having a basic type for a self-contained attribute weaken the language, since with self-contained attributes the name of the attribute already adequately describes the concept and thus contributes to the UL vocabulary? For example, the term person_age already adequately explains the concept of quantifying the number of years a person has: class Person { string person_age; } so what could we possibly gain by also introducing the term ThingAge to the UL: class person { ThingAge person_age; } thanks

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  • Compressing/compacting messages over websocket on Node.js

    - by icelava
    We have a websocket implementation (Node.js/Sock.js) that exchanges data as JSON strings. As our use cases grow, so have the size of the data transmitted across the wire. The websocket protocol does not natively offer any compression feature, so in order to reduce the size of our messages we'd have to manually do something about the serialisation. There appear to be a variety of LZW implementations in Javascript, some which confuses me on their compatibility for in-browser use only versus transmission across the wire due to my lack of understanding on low-level encodings. More importantly, all of them seem to take a noticeable performance drag when Javascript is the engine doing the compression/decompression work, which is not desirable for mobile devices. Looking instead other forms of compact serialisation, MessagePack does not appear to have any active support in Javascript itself; BSON does not have any Javascript implementation; and an alternative BISON project that I tested does not deserialise everything back to their original values (large numbers), and it does not look like any further development will happen either. What are some other options others have explored for Node.js?

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  • How to represent a graph with multiple edges allowed between nodes and edges that can selectively disappear

    - by Pops
    I'm trying to figure out what sort of data structure to use for modeling some hypothetical, idealized network usage. In my scenario, a number of users who are hostile to each other are all trying to form networks of computers where all potential connections are known. The computers that one user needs to connect may not be the same as the ones another user needs to connect, though; user 1 might need to connect computers A, B and D while user 2 might need to connect computers B, C and E. Image generated with the help of NCTM Graph Creator I think the core of this is going to be an undirected cyclic graph, with nodes representing computers and edges representing Ethernet cables. However, due to the nature of the scenario, there are a few uncommon features that rule out adjacency lists and adjacency matrices (at least, without non-trivial modifications): edges can become restricted-use; that is, if one user acquires a given network connection, no other user may use that connection in the example, the green user cannot possibly connect to computer A, but the red user has connected B to E despite not having a direct link between them in some cases, a given pair of nodes will be connected by more than one edge in the example, there are two independent cables running from D to E, so the green and blue users were both able to connect those machines directly; however, red can no longer make such a connection if two computers are connected by more than one cable, each user may own no more than one of those cables I'll need to do several operations on this graph, such as: determining whether any particular pair of computers is connected for a given user identifying the optimal path for a given user to connect target computers identifying the highest-latency computer connection for a given user (i.e. longest path without branching) My first thought was to simply create a collection of all of the edges, but that's terrible for searching. The best thing I can think to do now is to modify an adjacency list so that each item in the list contains not only the edge length but also its cost and current owner. Is this a sensible approach? Assuming space is not a concern, would it be reasonable to create multiple copies of the graph (one for each user) rather than a single graph?

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  • Thoughts on type aliases/synonyms?

    - by Rei Miyasaka
    I'm going to try my best to frame this question in a way that doesn't result in a language war or list, because I think there could be a good, technical answer to this question. Different languages support type aliases to varying degrees. C# allows type aliases to be declared at the beginning of each code file, and they're valid only throughout that file. Languages like ML/Haskell use type aliases probably as much as they use type definitions. C/C++ are sort of a Wild West, with typedef and #define often being used seemingly interchangeably to alias types. The upsides of type aliasing don't invoke too much dispute: It makes it convenient to define composite types that are described naturally by the language, e.g. type Coordinate = float * float or type String = [Char]. Long names can be shortened: using DSBA = System.Diagnostics.DebuggerStepBoundaryAttribute. In languages like ML or Haskell, where function parameters often don't have names, type aliases provide a semblance of self-documentation. The downside is a bit more iffy: aliases can proliferate, making it difficult to read and understand code or to learn a platform. The Win32 API is a good example, with its DWORD = int and its HINSTANCE = HANDLE = void* and its LPHANDLE = HANDLE FAR* and such. In all of these cases it hardly makes any sense to distinguish between a HANDLE and a void pointer or a DWORD and an integer etc.. Setting aside the philosophical debate of whether a king should give complete freedom to their subjects and let them be responsible for themselves or whether they should have all of their questionable actions intervened, could there be a happy medium that would allow the benefits of type aliasing while mitigating the risk of its abuse? As an example, the issue of long names can be solved by good autocomplete features. Visual Studio 2010 for instance will alllow you to type DSBA in order to refer Intellisense to System.Diagnostics.DebuggerStepBoundaryAttribute. Could there be other features that would provide the other benefits of type aliasing more safely?

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  • You may be tempted by IaaS, but you should PaaS on that or your database cloud journey will be a short one

    - by B R Clouse
    Before we examine Consolidation, the next step in the journey to cloud, let's take a short detour to address a critical choice you will face at the outset of your journey: whether to deploy your databases in virtual machines or not. A common misconception we've encountered is the belief that moving to cloud computing can be accomplished by simply hosting one's current operating environment as-is within virtual machines, and then stacking those VMs together in a consolidated environment.  This solution is often described as "Infrastructure as a Service" (IaaS) because the building block for deployments is a VM, which behaves like a full complement of infrastructure.  This approach is easy to understand and may feel like a good first step, but it won't take your databases very far in the journey to cloud computing.  In fact, if you follow the IaaS fork in the road, your journey will end quickly, without realizing the full benefits of cloud computing.  The better option to is to rationalize the deployment stack so that VMs are needed only for exceptional cases.  By settling on a standard operating system and patch level, you create an infrastructure that potentially all of your databases can share.  Now, the building block will be database instances or possibly schemas within databases.  These components are the platforms on which you will deploy workloads, hence this is known as "Platform as a Service" (PaaS). PaaS opens the door to higher degrees of consolidation than IaaS, because with PaaS you will not need to accommodate the footprint (operating system, hypervisor, processes, ...) that each VM brings with it.  You will also reduce your maintenance overheard if you move forward without the VMs and their O/Ses to patch and monitor.  So while IaaS simply shuffles complex and varied environments into VMs,  PaaS actually reduces complexity by rationalizing to the small possible set of components.  Now we're ready to look at the consolidation options that PaaS provides -- in our next blog posting.

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  • Sucking Less Every Year ?

    - by AdityaGameProgrammer
    Sucking Less Every Year A trail of thought that had been on my mind for a while Quoting directly from the post I've often thought that sucking less every year is how humble programmers improve. You should be unhappy with code you wrote a year ago. If you aren't, that means either A) you haven't learned anything in a year, B) your code can't be improved, or C) you never revisit old code. All of these are the kiss of death for software developers. How often does this happen or not happen to you? How long before you see an actual improvement in your coding ? month, year? Do you ever revisit Your old code? How often does your old code plague you? or how often do you have to deal with your technical debt. It is definitely very painful to fix old bugs n dirty code that we may have done to quickly meet a deadline and those quick fixes ,some cases we may have to rewrite most of the application/code. No arguments about that. Some of the developers i had come across argued that they were already at the evolved stage where their coding doesn't need improvement or cant get improved anymore. Does this happen? If so how many years into coding on a particular language does one expect this to happen?

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  • How do you deal with poor management [closed]

    - by Sybiam
    I come from a company where during a project, we saw the client 3 time during the whole project. We were never informed when did the client came in office in order to discuss with him about his requirements. I did setup redmine and told them that if they have any request they can post an issue there. But they never really used redmine to publish anything. They would instead: harass a team member on the phone at any time of the day or night hand us over sheets of paper with new requests or changes hand us over new design (graphical) They requested how much time it would take us to finish the project, I gave them a date and a week to test everything and deployment. I calculated that time taking into account the current features we had to do. And then blamed us that our deadline was wrong and that we lied. But the truth is that one week before that deadline they added a couple of monster feature from nowhere and that week were we were supposed to test and deploy, my friends spent all day in the office changing all little things. After that project, my friend got some kind of depression and got scared everytime his phone rang. They kind of used him as a communication proxy. After that project of hell, (every body got pissed off on that project) as far as I know the designer who was working with us left work after that project and she had some kind of issue too with managers. My team also started looking for work somewhere else. At first I tried to get things straight with management, I tried to make a meeting to discuss about the communication issues and so on.. What really pissed me off and made me leave that job for good is the following. Me: "We have to discuss about what went wrong on the last project. It's quite important" Him: "Lets talk about it in a week or two. Just make a list of all the things you did wrong" Me: "We already have a new project and we want to prevent what happened on the last project to happen again" Him: "Just do it and well have our meeting in a week, make a list of all the thing you did wrong." It kind of ended there then he organized a meeting at a moment I wasn't unable to come. My friend discussed with him and tried to explained him that we really had to discuss about organization issue on how to manage a project. And his answer was pretty much: "During the meeting I don't want to ear how you want to us to manage a project but I want to know what you guys did wrong" After that I felt it wasn't even worth it discussing anything since they weren't even ready listening to us. Found a new job and I'm pretty happy with my choice. I'd like to know how you'd handle such situation. Is there anything to do to solve communication problem? After that project my friend got a depression and some other employee had their down too as far as I know. I wonder what else we can do other than leave these place as soon as possible. Feel sad for the people that are still there and get screamed at just because they need money in order to eat and finding an other job like that isn't that easy. note I died a little when our boss asked us to make a list of things we (programmers) did wrong. This is probably the stupidest request I ever got. If everybody thinks they did everything right, it doesn't mean that there is no problems. Individual problem are rarely the big issue. Colleagues help each others and solve theses issues to prevent problems.

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  • Pathfinding with MicroPather : costs calculations with sectors and portals

    - by Adan
    Hello, I'm considering using micropather to help me with pathfinding. I'm not using a discrete map : I'm working in 2d with sectors and portales. However, I'm just wondering what is the best way to compute costs with this library in this context. Just to be more clear about geometrical shapes I'm using : sectors are basically convex polygons, and portals are segments that lies on sector's edge. Micropather exposes a pure virtual Graph class that you must inherate and overrides 3 functions. I understand how pathfinding works, so there's no problem in overriding those functions. Right now, my implementation give me results, i.e I'm able to find a path in my map, but I'm not sure I'm using an optimal solution. For the AdjacentCost method : I just take the distance between sector's centers as the cost. I think a better solution should be to use the portal between the two sectors, compute its center, and then the cost should be : distance( sector A center, portal center ) + distance ( sector B center, portal center ). I'm pretty sure the approximation I'm using with just sector's center is enough for most cases, but maybe with thin and long sectors that are perpendicular, this approximation could mislead the A* algorithm. For the LeastCostEstimate method : I just take the midpoint of the two sectors. So, as you understand, I'm always working with sectors' centers, and it's working fine. And I'm pretty sure there's a better way to work. Any suggestions or feedbacks? Thanks in advance!

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  • Assignments in mock return values

    - by zerkms
    (I will show examples using php and phpunit but this may be applied to any programming language) The case: let's say we have a method A::foo that delegates some work to class M and returns the value as-is. Which of these solutions would you choose: $mock = $this->getMock('M'); $mock->expects($this->once()) ->method('bar') ->will($this->returnValue('baz')); $obj = new A($mock); $this->assertEquals('baz', $obj->foo()); or $mock = $this->getMock('M'); $mock->expects($this->once()) ->method('bar') ->will($this->returnValue($result = 'baz')); $obj = new A($mock); $this->assertEquals($result, $obj->foo()); or $result = 'baz'; $mock = $this->getMock('M'); $mock->expects($this->once()) ->method('bar') ->will($this->returnValue($result)); $obj = new A($mock); $this->assertEquals($result, $obj->foo()); Personally I always follow the 2nd solution, but just 10 minutes ago I had a conversation with couple of developers who said that it is "too tricky" and chose 3rd or 1st. So what would you usually do? And do you have any conventions to follow in such cases?

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  • Caching by in-memory dictionaries. Are we doing it all wrong?

    - by user73983
    This approach is pretty much the accepted way to do anything in our company. A simple example : when a piece of data for a customer is requested from a service, we fetch all the data for that customer(relevant part to the service) and save it in a in-memory dictionary then serve it from there on following requests(we run singleton services). Any update goes to DB, then updates the in memory dictionary. It seems all simple and harmless but as we implement more complicated business rules the cache gets out of sync and we have to deal with hard to find bugs. Sometimes we defer writing to database, keeping new data in cache till then. There are cases when we store millions of rows in memory because the table has many relations to other tables and we need to show aggregate data quickly. All this cache handling is a big part of our codebase and I sense this is not the right way to do it. All of this juggling adds too much noise to the code and it makes it hard to understand the actual business logic. However I don't think we can serve data in a reasonable amount of time if we have to hit the database every time. I am unhappy about the current situation but I don't have a better alternative. My only solution would be to use NHibernate 2nd level cache but I have nearly no experience with it. I know many campanies use Redis or MemCached heavily to gain performance but I have no idea how I would integrate them into our system. I also don't know if they can perform better than in-memory data structures and queries. Are there any alternative approaches that I should look into?

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  • Friday tips #2

    - by Chris Kawalek
    Welcome to our second Friday tips blog! You can ask us questions using the hash tag #AskOracleVirtualization on Twitter and we'll do our best to answer them. Today we've got a VDI related question on linked clones: Question: I want to use linked clones with Oracle Virtual Desktop Infrastructure. What are my options? Answer by John Renko, Consulting Developer, Oracle: First, linked clones are available with the Oracle VirtualBox hypervisor only. Second, your choice of storage will affect the rest of your architecture. If you are using a SAN presenting ISCSI LUNS, you can have linked clones with a Oracle Enterprise Linux based hypervisor running VirtualBox. OEL will use OCFS2 to allow VirtualBox to create the linked clones. Because of the OCFS2 requirement, a Solaris based VirtualBox hypervisor will not be able to support linked clones on remote ISCSI storage. If you using the local storage option on your hypervisors, you will have linked clones with Solaris or Linux based hypervisors running VirtualBox. In all cases, Oracle Virtual Desktop Infrastructure makes the right selection for creating clones - sparse or linked - behind the scenes. Plan your architecture accordingly if you want to ensure you have the higher performing linked clones.

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  • NHibernate Pitfalls: Cascades

    - by Ricardo Peres
    This is part of a series of posts about NHibernate Pitfalls. See the entire collection here. For entities that have associations – one-to-one, one-to-many, many-to-one or many-to-many –, NHibernate needs to know what to do with their related entities, in three particular moments: when saving, updating or deleting. In particular, there are two possible behaviors: either ignore these related entities or cascade changes to them. NHibernate allows setting the cascade behavior for each association, and the default behavior is not to cascade (ignore). The possible cascade options are: None Ignore, this is the default Save-Update If the entity is being saved or updated, also save any related entities that are either not saved or have been modified and associate these related entities to the root entity. Generally safe Delete If the entity is being deleted, also delete the related entities. This is only useful for parent-child relations Delete-Orphan Identical to Delete, with the addition that if once related entity is removed from the association – orphaned –, also delete it. Also only for parent-child All Combination of Save-Update and Delete, usually that’s what we want (for parent-child relations, of course) All-Delete-Orphan Same as All plus delete any related entities who lose their relationship In summary, Save-Update is generally what you want in most cases. As for the Delete variations, they should only be used if the related entities depend on the root entity (parent-child), so that deleting the root entity and not their related entities would result in a constraint violation on the database.

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  • Getting Audio from a Zone

    - by bleonard
    Now that I have Firefox and Java Web Start running from a zone, the last piece of the puzzle was audio (essential because most Flash content is accompanied by sound).  In the global zone there's a nice little utility called audiotest for testing your sound: bleonard@solaris:~$ audiotest Sound subsystem and version: SunOS Audio 4.0 (0x00040003) Platform: SunOS 5.11 snv_151a i86pc *** Scanning sound adapter #1 *** /dev/sound/audio810:0dsp (audio engine 0): audio810#0 - Performing audio playback test... <left> ................OK <right> ...............OK <stereo> ..............OK <measured sample rate 47727.00 Hz (-0.57%)> *** All tests completed OK *** Of course, before you can try audiotest in a zone, it must be installed: root@myzone:~# pkg install audio-utilities Packages to install: 1 Create boot environment: No DOWNLOAD PKGS FILES XFER (MB) Completed 1/1 6/6 0.4/0.4 PHASE ACTIONS Install Phase 20/20 PHASE ITEMS Package State Update Phase 1/1 Image State Update Phase 2/2 However, we'll need to do more than just install audiotest: root@myzone:~# audiotest /dev/mixer: No such file or directory The device file is missing from /dev. The audio devices also need to be added to the zone. For this we modify the zone configuration as follows: bleonard@solaris:~$ sudo zonecfg -z myzone Password: zonecfg:myzone> add device zonecfg:myzone:device> set match=/dev/audio* zonecfg:myzone:device> end zonecfg:myzone> add device zonecfg:myzone:device> set match=/dev/sound/* zonecfg:myzone:device> end zonecfg:myzone> add device zonecfg:myzone:device> set match=/dev/mixer* zonecfg:myzone:device> end zonecfg:myzone> add device zonecfg:myzone:device> set match=/dev/sndstat zonecfg:myzone:device> end zonecfg:myzone> verify zonecfg:myzone> exit Then reboot the zone: bleonard@solaris:~$ sudo zoneadm -z myzone reboot After which, audiotest should work: root@myzone:~# audiotest Sound subsystem and version: SunOS Audio 4.0 (0x00040003) Platform: SunOS 5.11 snv_151a i86pc *** Scanning sound adapter #1 *** /dev/sound/audio810:0dsp (audio engine 0): audio810#0 - Performing audio playback test... <left> ................OK <right> ...............OK <stereo> ..............OK <measured sample rate 48208.00 Hz (0.43%)> *** All tests completed OK *** You can also examine /dev/sndstat for additional information: root@myzone:~# cat /dev/sndstat SunOS Audio Framework Audio Devices: 0: audio810#0 Intel AC'97, ICH (DUPLEX) Mixers: 0: audio810#0 Intel AC'97, ICH AC'97 codec: SigmaTel STAC9700 However, when testing the sound from Firefox (from a user account other than root), such as this recent Flash presentation on Solaris availability, you may still be disappointed. This is simply a permissions problem, as the devices only have read and write permissions for root: root@myzone:~# ls -l /dev/audio* crw------- 1 root root 99, 3 Jul 1 10:21 /dev/audio crw------- 1 root root 99, 4 Jul 1 10:21 /dev/audioctl To address this: root@myzone:~# chmod 777 /dev/audio* root@myzone:~# chmod 777 /dev/sound/* And you should be all set.

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  • Attributes of an Ethical Programmer?

    - by ahmed
    Software that we write has ramifications in the real world. If not, it wouldn't be very useful. Thus, it has the potential to sweep across the world faster than a deadly manmade virus or to affect society every bit as much as genetic manipulation. Maybe we can't see how right now, but in the future our code will have ever-greater potential for harm or good. Of course, there's the issue of hacking. That's clearly a crime. Or is it that clear? Isn't hacking acceptable for our government in the event of national security? What about for other governments? Cases of life-and-death emergency? Tracking down deadbeat parents? Screening the genetic profile of job candidates? Where is the line drawn? Who decides? Do programmers have responsibility for how their code is used? What if a programmer writes code to pry into confidential information or copy-protected material? Does he bear responsibility along with the person who used the program? What about a programmer who knowingly or unknowingly writes code to "fix the books?" Should he be liable?

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  • Impact of Server Failure on Coherence Request Processing

    - by jpurdy
    Requests against a given cache server may be temporarily blocked for several seconds following the failure of other cluster members. This may cause issues for applications that can not tolerate multi-second response times even during failover processing (ignoring for the moment that in practice there are a variety of issues that make such absolute guarantees challenging even when there are no server failures). In general, Coherence is designed around the principle that failures in one member should not affect the rest of the cluster if at all possible. However, it's obvious that if that failed member was managing a piece of state that another member depends on, the second member will need to wait until a new member assumes responsibility for managing that state. This transfer of responsibility is (as of Coherence 3.7) performed by the primary service thread for each cache service. The finest possible granularity for transferring responsibility is a single partition. So the question becomes how to minimize the time spent processing each partition. Here are some optimizations that may reduce this period: Reduce the size of each partition (by increasing the partition count) Increase the number of JVMs across the cluster (increasing the total number of primary service threads) Increase the number of CPUs across the cluster (making sure that each JVM has a CPU core when needed) Re-evaluate the set of configured indexes (as these will need to be rebuilt when a partition moves) Make sure that the backing map is as fast as possible (in most cases this means running on-heap) Make sure that the cluster is running on hardware with fast CPU cores (since the partition processing is single-threaded) As always, proper testing is required to make sure that configuration changes have the desired effect (and also to quantify that effect).

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  • What's wrong with cplusplus.com?

    - by Kerrek SB
    This is perhaps not a perfectly suitable forum for this question, but let me give it a shot, at the risk of being moved away. There are several references for the C++ standard library, including the invaluable ISO standard, MSDN, IBM, cppreference, and cplusplus. Personally, when writing C++ I need a reference that has quick random access, short load times and usage examples, and I've been finding cplusplus.com pretty useful. However, I've been hearing negative opinions about that website frequently here on SO, so I would like to get specific: What are the errors, misconceptions or bad pieces of advice given by cplusplus.com? What are the risks of using it to make coding decisions? Let me add this point: I want to be able to answer questions here on SO with accurate quotes of the standard, and thus I would like to post immediately-usable links, and cplusplus.com would have been my choice site were it not for this issue. Update: There have been many great responses, and I have seriously changed my view on cplusplus.com. I'd like to list a few choice results here; feel free to suggest more (and keep posting answers). As of June 29, 2011: Incorrect description of some algorithms (e.g. remove). Information about the behaviour of functions is sometimes incorrect (atoi), fails to mention special cases (strncpy), or omits vital information (iterator invalidation). Examples contain deprecated code (#include style). Inexact terminology is doing a disservice to learners and the general community ("STL", "compiler" vs "toolchain"). Incorrect and misleading description of the typeid keyword.

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  • Why is math taught "backwards"? [closed]

    - by Yorirou
    A friend of mine showed me a pretty practical Java example. It was a riddle. I got excited and quickly solved the problem. After it, he showed me the mathematical explanation of my solution (he proved why is it good), and it was completely clear for me. This seems like natural approach for me: solve problems, and generalize. This is very familiar to me, I do it all the time when I am programming: I write a function. When I have to write a similar function, I generalize the problem, grab the generic parts, and refactor them to a function, and solve the original problems as a specialization of the general function. At the university (or at least where I study), things work backwards. The professors shows just the highest possible level of the solutions ("cryptic" mathematical formulas). My problem is that this is too abstract for me. There is no connection of my previous knowledge (== reality in my sense), so even if I can understand it, I can't really learn it properly. Others are learning these formulas word-by-word, and get good grades, since they can write exactly the same to the test, but this is not an option for me. I am a curious person, I can learn interesting things, but I can't learn just text. My brain is for storing toughts, not strings. There are proofs for the theories, but they are also really hard to understand because of this, and in most of the cases they are omitted. What is the reason for this? I don't understand why is it a good idea to show the really high level of abstraction and then leave the practical connections (or some important ideas / practical motivations) out?

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  • Strategies for managing use of types in Python

    - by dave
    I'm a long time programmer in C# but have been coding in Python for the past year. One of the big hurdles for me was the lack of type definitions for variables and parameters. Whereas I totally get the idea of duck typing, I do find it frustrating that I can't tell the type of a variable just by looking at it. This is an issue when you look at someone else's code where they've used ambiguous names for method parameters (see edit below). In a few cases, I've added asserts to ensure parameters comply with an expected type but this goes against the whole duck typing thing. On some methods, I'll document the expected type of parameters (eg: list of user objects), but even this seems to go against the idea of just using an object and let the runtime deal with exceptions. What strategies do you use to avoid typing problems in Python? Edit: Example of the parameter naming issues: If our code base we have a task object (ORM object) and a task_obj object (higher level object that embeds a task). Needless to say, many methods accept a parameter named 'task'. The method might expect a task or a task_obj or some other construct such as a dictionary of task properties - it is not clear. It is them up to be to look at how that parameter is used in order to work out what the method expects.

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  • Is there a common programming term for the problems of adding features to an already-featureful program?

    - by Jeremy Friesner
    I'm looking for a commonly used programming term to describe a software-engineering phenomenon, which (for lack of a better way to describe it) I'll illustrate first with a couple of examples-by-analogy: Scenario 1: We want to build/extend a subway system on the outskirts of a small town in Wyoming. There are the usual subway-problems to solve, of course (hiring the right construction company, choosing the best route, buying the subway cars), but other than that it's pretty straightforward to implement the system because there aren't a huge number of constraints to satisfy. Scenario 2: Same as above, except now we need to build/extend the subway system in downtown Los Angeles. Here we face all of the problems we did in case (1), but also additional problems -- most of the applicable space is already in use, and has a vocal constituency which will protest loudly if we inconvenience them by repurposing, redesigning, or otherwise modifying the infrastructure that they rely on. Because of this, extensions to the system happen either very slowly and expensively, or they don't happen at all. I sometimes see a similar pattern with software development -- adding a new feature to a small/simple program is straightforward, but as the program grows, adding further new features becomes more and more difficult, if only because it is difficult to integrate the new feature without adversely affecting any of the large number of existing use-cases or user-constituencies. (even with a robust, adaptable program design, you run into the problem of the user interface becoming so elaborate that the program becomes difficult to learn or use) Is there a term for this phenomenon?

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  • Using Queries with Coherence Write-Behind Caches

    - by jpurdy
    Applications that use write-behind caching and wish to query the logical entity set have the option of querying the NamedCache itself or querying the database. In the former case, no particular restrictions exist beyond the limitations intrinsic to the Coherence query engine itself. In the latter case, queries may see partially committed transactions (e.g. with a parent-child relationship, the version of the parent may be different than the version of the child objects) and/or significant version skew (the query may see the current version of one object and a far older version of another object). This is consistent with "read committed" semantics, but the read skew may be far greater than would ever occur in a non-cached environment. As is usually the case, the application developer may choose to accept these limitations (with the hope that they are sufficiently infrequent), or they may choose to validate the reads (perhaps via a version flag on the objects). This also applies to situations where a third party application (such as a reporting tool) is querying the database. In many cases, the database may only be in a consistent state after the Coherence cluster has been halted.

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  • IoT: Wearables!

    - by Tori Wieldt
    Wearables are a subset of the Internet of Things that has gained a lot of attention. Wearables can monitor your infant's heartrate, open your front door, or warn you when someone's trying to hack your enterprise network. From Devoxx UK to Oracle OpenWorld to Devoxx4kids, everyone seems to be doing something with wearables.  In this video, John McLear introduces the NFC Ring. It can be used to unlock doors, mobile phones, transfer information and link people. The software for developers is open source, so get coding! If you are coming to JavaOne or Oracle OpenWorld, join us for Dress Code 2.0, a wearables meetup. Put on your best wearables gear and come hang out with the Oracle Applications User Experience team and friends at the OTN Lounge. We'll discuss the finer points of use cases, APIs, integrations, UX design, and fashion and style considerations for wearable tech development. There will be gifts for attendees sporting wearable tech, while supplies last. What: Dress Code 2.0: A Wearables Meetup When: Tuesday, 30-September-2014, 4-6 PM Where: OTN Lounge at Oracle OpenWorld IoT - Wearable Resources The IoT Community on Java.net Wearables in the World of Enterprise Applications? Yep. The Paradox of Wearable Technologies Conference: Wearable Sensors and Electronics (Santa Clara, USA) Devoxx4Kids Workshop for Youth: Wearable tech! (Mountain View, USA)

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  • Forking a GPL dual licensed software with business owned copyrights

    - by Eric
    After receiving some threats of the copyrights holder of a dual licensed software(GPL2 and commercial) to buy the commercial version for projects in production, I am thinking to make a fork. In a case of GPL2 and commercially dual licensed with business owned copyrights software, is forking the GPL2 version an option? Also, is forking a good way to deal with such cases? Background information The software is a web CMS released under 2 versions a GPL2 free open source edition and a commercial edition including technical support and extra functionality. The problem is that now, basing their argumentation on the "distribution" definition of the GPL2, the company holding the copyrights argue that delivering the software and some extensions to a client is considered as a "distribution". And that such a "distribution" falls under the GPL2 obligation to release the custom made extension code. Custom made extensions are mainly designs, templates and very specific functionality. Basically they give me 3 choices: Buying the commercial licensed edition for projects based on the GPL in production, Deleting all the projects in production based on GPL2 version, Releasing all the extensions as GPL2 code. The first 2 options are nothing realistic for finished projects. The third option could be fine, but as most of the extensions are very specific, cleaning the code to make it usable by other users means lot of works and also I am not sure the clients will appreciate to have their website designs and specific functionality released publicly. The copyrights holding company even contacted some clients directly, giving them the "choice". I know that this is a very corporate interpretation of GPL2, and a such action is nothing close to legal, but as an independent developer, I don't want to take the risk to get involved in some long and tiring legal procedures. PS. This question was first asked on Stack Overflow where it felt out of the scope and closed, after reading the present site FAQ, discussing about software licensing seems fine.

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  • Looking for a better Factory pattern (Java)

    - by Sam Goldberg
    After doing a rough sketch of a high level object model, I am doing iterative TDD, and letting the other objects emerge as a refactoring of the code (as it increases in complexity). (That whole approach may be a discussion/argument for another day.) In any case, I am at the point where I am looking to refactor code blocks currently in an if-else blocks into separate objects. This is because there is another another value combination which creates new set of logical sub-branches. To be more specific, this is a trading system feature, where buy orders have different behavior than sell orders. Responses to the orders have a numeric indicator field which describes some event that occurred (e.g. fill, cancel). The combination of this numeric indicator field plus whether it is a buy or sell, require different processing buy the code. Creating a family of objects to separate the code for the unique handling each of the combinations of the 2 fields seems like a good choice at this point. The way I would normally do this, is to create some Factory object which when called with the 2 relevant parameters (indicator, buysell), would return the correct subclass of the object. Some times I do this pattern with a map, which allows to look up a live instance (or constructor to use via reflection), and sometimes I just hard code the cases in the Factory class. So - for some reason this feels like not good design (e.g. one object which knows all the subclasses of an interface or parent object), and a bit clumsy. Is there a better pattern for solving this kind of problem? And if this factory method approach makes sense, can anyone suggest a nicer design?

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