# Search Results

• ### Why is my implementation of the Sieve of Atkin overlooking numbers close to the specified limit?

##### - by Ross G
My implementation either overlooks primes near the limit or composites near the limit. while some limits work and others don't. I'm am completely confused as to what is wrong. def AtkinSieve (limit): results = [2,3,5] sieve = [False]*limit factor = int(math.sqrt(lim)) for i in range(1,factor): for j in range(1, factor): n = 4*i**2+j**2 if (n <= lim) and (n % 12 == 1 or n % 12 == 5): sieve[n] = not sieve[n] n = 3*i**2+j**2 if (n <= lim) and (n % 12 == 7): sieve[n] = not sieve[n] if i>j: n = 3*i**2-j**2 if (n <= lim) and (n % 12 == 11): sieve[n] = not sieve[n] for index in range(5,factor): if sieve[index]: for jndex in range(index**2, limit, index**2): sieve[jndex] = False for index in range(7,limit): if sieve[index]: results.append(index) return results For example, when I generate a primes to the limit of 1000, the Atkin sieve misses the prime 997, but includes the composite 965. But if I generate up the limit of 5000, the list it returns is completely correct.

• ### Why is my implementation of the Sieve of Atkin overlooking numbers close to the specified limit?

##### - by Ross G
My implementation either overlooks primes near the limit or composites near the limit. while some limits work and others don't. I'm am completely confused as to what is wrong. def AtkinSieve (limit): results = [2,3,5] sieve = [False]*limit factor = int(math.sqrt(lim)) for i in range(1,factor): for j in range(1, factor): n = 4*i**2+j**2 if (n <= lim) and (n % 12 == 1 or n % 12 == 5): sieve[n] = not sieve[n] n = 3*i**2+j**2 if (n <= lim) and (n % 12 == 7): sieve[n] = not sieve[n] if i>j: n = 3*i**2-j**2 if (n <= lim) and (n % 12 == 11): sieve[n] = not sieve[n] for index in range(5,factor): if sieve[index]: for jndex in range(index**2, limit, index**2): sieve[jndex] = False for index in range(7,limit): if sieve[index]: results.append(index) return results For example, when I generate a primes to the limit of 1000, the Atkin sieve misses the prime 997, but includes the composite 965. But if I generate up the limit of 5000, the list it returns is completely correct.

• ### R how to find NA values after using addNA function

##### - by screechOwl
I have a data frame with a bunch of categorical variables. Some of them contain NA's and I use the addNA function to convert them to an explicit factor level. My problem comes when I try to treat them as NA's they don't seem to register. Here's my example data set and attempts to 'find' NA's: df1 <- data.frame(id = 1:200, y =rbinom(200, 1, .5), var1 = factor(rep(c('abc','def','ghi','jkl'),50))) df1\$var2 <- factor(rep(c('ab c','ghi','jkl','def'),50)) df1\$var3 <- factor(rep(c('abc','ghi','nop','xyz'),50)) df1[df1\$var1 == 'abc','var1'] <- NA df1\$var1 <- addNA(df1\$var1) df1\$isNaCol <- ifelse(df1\$var1 == NA, 1, 0);summary(df1\$isNaCol) df1\$isNaCol <- ifelse(is.na(df1\$var1), 1, 0);summary(df1\$isNaCol) df1\$isNaCol <- ifelse(df1\$var1 == 'NA', 1, 0);summary(df1\$isNaCol) df1\$isNaCol <- ifelse(df1\$var1 == '<NA>', 1, 0);summary(df1\$isNaCol) Also when I type ??addNA I don't get any matches. Is this a gray-market function or something? Any suggestions would be appreciated.

• ### How can you transform a set of numbers into mostly whole ones?

##### - by Alice
Small amount of background: I am working on a converter that bridges between a map maker (Tiled) that outputs in XML, and an engine (Angel2D) that inputs lua tables. Most of this is straight forward However, Tiled outputs in pixel offsets (integers of absolute values), while Angel2D inputs OpenGL units (floats of relative values); a conversion factor between these two is needed (for example, 32px = 1gu). Since OpenGL units are abstract, and the camera can zoom in or out if the objects are too small or big, the actual conversion factor isn't important; I could use a random number, and the user would merely have to zoom in or out. But it would be best if the conversion factor was selected such that most numbers outputted were small and whole (or fractions of small whole numbers), because that makes it easier to work with (and the whole point of the OpenGL units is that they are easy to work with). How would I find such a conversion factor reliably? My first attempt was to use the smallest number given; this resulted in no fractions below 1, but often lead to lots of decimal places where the factors didn't line up. Then I tried the mode of the sequence, which lead to the largest number of 1's possible, but often lead to very long floats for background images. My current approach gets the GCD of the whole sequence, which, when it works, works great, but can easily be thrown off course by a single bad apple. Note that while I could easily just pass the numbers I am given along, or pick some fixed factor, or use one of the conversions I specified above, I am looking for a method to reliably scale this list of integers to small, whole numbers or simple fractions, because this would most likely be unsurprising to the end user; this is not a one off conversion. The end users tend to use 1.0 as their "base" for manipulations (because it's simple and obvious), so it would make more sense for the sizes of entities to cluster around this.

• ### How to extend this design for a generic converter in java?

##### - by Jay
Here is a small currency converter piece of code: public enum CurrencyType { DOLLAR(1), POUND(1.2), RUPEE(.25); private CurrencyType(double factor) { this.factor = factor; } private double factor; public double getFactor() { return factor; } } public class Currency { public Currency(double value, CurrencyType type) { this.value = value; this.type = type; } private CurrencyType type; private double value; public CurrencyType getCurrencyType() { return type; } public double getCurrencyValue() { return value; } public void setCurrenctyValue(double value){ this.value = value; } } public class CurrencyConversion { public static Currency convert(Currency c1, Currency c2) throws Exception { if (c1 != null && c2 != null) { c2.setCurrenctyValue(c1.getCurrencyValue() * c1.getCurrencyType().getFactor() * c2.getCurrencyType().getFactor()); return c2; } else throw new Exception(); } } I would like to improve this code to make it work for different units of conversion, for example: kgs to pounds, miles to kms, etc etc. Something that looks like this: public class ConversionManager<T extends Convertible> { public T convert(T c1, T c2) { //return null; } } Appreciate your ideas and suggestions.

• ### A temporary disagreement

##### - by Tony Davis
Last month, Phil Factor caused a furore amongst some MVPs with an article that attempted to offer simple advice to developers regarding the use of table variables, versus local and global temporary tables, in their code. Phil makes clear that the table variables do come with some fairly major limitations.no distribution statistics, no parallel query plans for queries that modify table variables.but goes on to suggest that for reasonably small-scale strategic uses, and with a bit of due care and testing, table variables are a "good thing". Not everyone shares his opinion; in fact, I imagine he was rather aghast to learn that there were those felt his article was akin to pulling the pin out of a grenade and tossing it into the database; table variables should be avoided in almost all cases, according to their advice, in favour of temp tables. In other words, a fairly major feature of SQL Server should be more-or-less 'off limits' to developers. The problem with temp tables is that, because they are scoped either in the procedure or the connection, it is easy to allow them to hang around for too long, eating up precious memory and bulking up the shared tempdb database. Unless they are explicitly dropped, global temporary tables, and local temporary tables created within a connection rather than within a stored procedure, will persist until the connection is closed or, with connection pooling, until the connection is reused. It's also quite common with ASP.NET applications to have connection leaks, as Bill Vaughn explains in his chapter in the "SQL Server Deep Dives" book, meaning that the web page exits without closing the connection object, maybe due to an error condition. This will then hang around in the heap for what might be hours before picked up by the garbage collector. Table variables are much safer in this regard, since they are batch-scoped and so are cleaned up automatically once the batch is complete, which also means that they are intuitive to use for the developer because they conform to scoping rules that are closer to those in procedural code. On the surface then, an ideal way to deal with issues related to tempdb memory hogging. So why did Phil qualify his recommendation to use Table Variables? This is another of those cases where, like scalar UDFs and table-valued multi-statement UDFs, developers can sometimes get into trouble with a relatively benign-looking feature, due to way it's been implemented in SQL Server. Once again the biggest problem is how they are handled internally, by the SQL Server query optimizer, which can make very poor choices for JOIN orders and so on, in the absence of statistics, especially when joining to tables with highly-skewed data. The resulting execution plans can be horrible, as will be the resulting performance. If the JOIN is to a large table, that will hurt. Ideally, Microsoft would simply fix this issue so that developers can't get burned in this way; they've been around since SQL Server 2000, so Microsoft has had a bit of time to get it right. As I commented in regard to UDFs, when developers discover issues like with such standard features, the database becomes an alien planet to them, where death lurks around each corner, and they continue to avoid these "killer" features years after the problems have been eventually resolved. In the meantime, what is the right approach? Is it to say "hammers can kill, don't ever use hammers", or is it to try to explain, as Phil's article and follow-up blog post have tried to do, what the feature was intended for, why care must be applied in its use, and so enable developers to make properly-informed decisions, without requiring them to delve deep into the inner workings of SQL Server? Cheers, Tony.

• ### Windows Server 2003 Licensing

##### - by Phil
Hi all, I'm looking to get a Windows Server 2003 box in the middle of my linux network. :( I'm just concerned about CAL licensing for it. No devices will access any network server function of Windows Server 2003. I don't need Windows for DHCP or DNS or file and print sharing. I have linux boxes to do that! xD I just need a box running Windows (of some variety) to host those few apps that have to run on Windows like my AV management console. In short do I need any CALs for my server if its not acting as server itself. I think Windows Server 2003 comes with 5 CALs which can be per user for the admins to use RDP? Thanks, Phil

• ### WHM Cpanel Enable/Install MBstring module

##### - by Phil Jackson
Hi, this is my second post here and only my second day dealing with my own dedicated server. I have no previous experience in this field so please bear with me. I have successfully created a package and linked up my domain yesterday. I am getting an error regarding mb_convert_encoding() wich after doing some reading discover I have to enable or install a module?? Any way, my cpanel is "cPanel 11.25.0-R46156 - WHM 11.25.0 - X 3.9" and after some searching found mainsoftwareModule Installers but cannot find any to do with mbstrings. Could anyone point me in the right direction in what or where I should be looking?? Any help much appreciated, Regards, Phil

• ### Windows 2003 Server R2SP2 throws even ID 2269 after installing Excel WebPart in MOSS3

##### - by Phil
We recently added an Excel workbook webpart (read only excel file - no editing) on our Sharepoint 2007 server. Once we did that, approximately 3-4 times an hour event ID 2269 is shown in the Application Log and a few minutes after that, an event id 1002 is displayed in the system long and the Sharepoint Offfce Servers Application pool shuts down. We've already check the "Bypass traverse checking and DCOM settings) per the MS KB and I have opened a ticket with MS Support. Problem is that MS Suppoert (sharepoint) thinks it is an IIS problem and the IIS people think it is a Sharepoint issue. Anyone else seen this problem? If we remove the Excel webpart, everything goes back to normal. The App Pools, SP and SP Central Admin sites are all using the same domain service account. Thanks in advance, Phil

• ### USB drivers installed twice

##### - by stupid-phil
Hello, I have a problem with usb drivers on Windows 7 64bit When I start up my laptop, the mouse I have plugged into a usb port does not work. I have to open the device manager, where there are two "Standard Enhanced PCI to USB Host Controller" entries. One is marked as faulty (yellow triangle). I uninstall this. Scan for changes. Then it re-appears, but not marked as faulty. And the mouse works. I have to do this every time I reboot. A colleague has the same problem. Both DELL laptops, but different models. I've tried uninstalling all USB controllers, but after a reboot, they are all reinstalled with the faulty entry. This only started happening in the last few weeks. Any help appreciated. It's driving me nuts. Thanks Phil

• ### Should I use android AccountManager?

##### - by Phil
I've seen AccountManager in the android SDK, and can see it is used for storing account information, but I can't find any general discussion of what it is intended for. Anyone know of any helpful discussions of what the intention behind AccountManager is and what it buys you Any opinions of what type of Accounts this is suitable for? Would this be where you'd put your user's account information for a general web service? Regards Phil

• ### MySQL - connection and security

##### - by Phil Jackson
Hi, I was wondering if someone could tell me if there is any potential security breeches that could occur by connecting to a sql database that does not reside at 'localhost' i.e. via ip address? Regards, Phil

• ### Move mouse cursor using javascript in Chrome or Firefox using any method (Plugin, GreaseMonkey?)

##### - by Phil
Hi, I have need to move the mouse cursor position in the browser, I can use any method as long as its in Google Chrome or Firefox, one or the other. In the best case, I would like to control the mouse position with javascript. Any easy way to do this? Thanks! Phil

• ### Is there a 64-bit version of Microsoft Common Controls (MSCOMCTL.OCX)?

##### - by phil
Did Microsoft port MSCOMCTL.OCX to 64-bit? I don't have it installed and I can't find it for download or find anything saying that it doesn't exist. Thanks, Phil

• ### UK IP address lookup API

##### - by Phil Jackson
Hi, im looking for a UK IP address lookup api ( or PHP script ) to find the location of a user. I want to produce more relevent results for a user when searching a directory. All the ones I have found just say 'UK' and dont get any more information than that. Can anyone point me in the right direction? Regards, Phil

• ### creating email forwarding accounts on the fly using PHP

##### - by Phil Jackson
Hi, i was wondering if it was possible to create email forwading accounts on the fly as I have created subdomains for uses profiles i.e. user.profile.com and was wondering if I could create [email protected] to forward to their email account? Regards, Phil

• ### Error when restoring SSAS cube: MemberKeyesUnique element at line xxx cannot appear under (...)/Hier

##### - by Phil
Hi, I'm getting this error when trying to restore an SSAS database from a backup: The ddl2:MemberKeysUnique element at line 63, column 4862 (namespace http://schemas.microsoft.com/analysisservices/2003/engine/2) cannot appear under Load/ObjectDefinition/Dimension/Hierarchies/Hierarchy. Google hasn't turned up any helpful solutions. (a lot of people found that installing SP2 made the error go away but this has always previously worked in our environment) I don't really understand what the error means. Can somebody interpret or suggest a fix? Thanks, Phil

• ### SSAS dimension source table changed - how to propagate changes to analysis server?

##### - by Phil
Hi, Sorry if the question isn't phrased very well but I'm new to SSAS and don't know the correct terms. I have changed the name of a table and its columns. I am using said table as a dimension for my cube, so now the cube won't process. Presumably I need to make updates in the analysis server to reflect changes to the source database? I have no idea where to start - any help gratefully received. Thanks Phil

• ### Dynamic casting using a generic interface

##### - by Phil Whittaker
Hi Is there any way to cast to a dynamic generic interface.. Site s = new Site(); IRepository<Site> obj = (IRepository<s.GetType()>)ServiceLocator.Current.GetInstance(t) obviously the above won't compile with this cast. Is there anyway to do a dynamic cast of a generic interface. I have tried adding a non generic interface but the system is looses objects in the Loc container. Thanks Phil

• ### ocupation and business type drop down lists

##### - by Phil Jackson
Hi, does anyone know of an API or where I could get hold of data/script to create a <select> drop down lists for occupation and job type? Regards, Phil

• ### Protecing Code and Licencing

##### - by Phil Jackson
Hi, I have been creating a cross browser compatible ( = ie 6 + standards complaint browsers ) Online Instant Messenger What I would like to know is what licensing would I need to protect my code? how would i go about getting a license and where from? My code is in PHP, and jQuery. Regards, Phil

• ### Do I need to drop index on temp table?

##### - by Phil
Hi, Fairly simple question, but I don't see it anywhere else on SO: Do indexes (indices?) on a temporary table get automatically deleted with the temporary table? I'd imagine they do but I don't really know how to check to make sure. Thanks, Phil

• ### .htaccess or PHP protection code against multiple speedy requests

##### - by Phil Jackson
Hi, I am looking for ideas for how I can stop external scripts connecting with my site. I'm looking for the same kind of idea behind Google. As in if a certain amount of requests are made per a certain amount of time then block the IP address or something. I thought there maybe a htaccess solution if not, I will write a PHP one. Any ideas or links to existing methods or scripts is much appreciated. Regards Phil