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  • Database Design Question: GUID + Natural Numbers

    - by Alan
    For a database I'm building, I've decided to use natural numbers as the primary key. I'm aware of the advantages that GUID's allow, but looking at the data, the bulk of row's data were GUID keys. I want to generate XML records from the database data, and one problem with natural numbers is that I don't want to expose my database key's to the outside world, and allow users to guess "keys." I believe GUID's solve this problem. So, I think the solution is to generate a sparse, unique iD derived from the natural ID (hopefully it would be 2-way), or just add an extra column in the database and store a guid (or some other multibyte id) The derived value is nicer because there is no storage penalty, but it would be easier to reverse and guess compared to a GUID. I'm (buy) curious as to what others on SO have done, and what insights they have.

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  • Mean of Sampleset and powered Sampleset

    - by Milla Well
    I am working on an ICA implementation wich is based on the assumption, that all source signals are independent. So I checked on the basic concepts of Dependence vs. Correlation and tried to show this example on sample data from numpy import * from numpy.random import * k = 1000 s = 10000 mn = 0 mnPow = 0 for i in arange(1,k): a = randn(s) a = a-mean(a) mn = mn + mean(a) mnPow = mnPow + mean(a**3) print "Mean X: ", mn/k print "Mean X^3: ", mnPow/k But I couldn't produce the last step of this example E(X^3) = 0: >> Mean X: -1.11174580826e-18 >> Mean X^3: -0.00125229267144 First value I would consider to be zero, but second value is too large, isn't it? Since I subtract the mean of a, I expected the mean of a^3 to be zero as well. Does the problem lie in the random number generator, the precision of the numerical values in my misunderstanding of the concepts of mean and expected value?

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  • How to get some randomized concats based on 2 columns from 1 table?

    - by Nils Riedemann
    Hey folks, i have a large user Database (13k+), and for some reason i need to create random names. The users table has "first_name" and "last_name". Now i want to have 10 concats of full_name and last_name of two completely random rows. Is that even possible with SQL? My other idea was just to create a full_names and last_names table … but that would'nt be as much challenging. Oh, and it should not take up too much performance :) (so order by rand() is not an option ;))

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  • PHP: find 2 or more numbers from a list of N numbers that can add up towards a given ammount

    - by Splash
    Hi Guys, I am trying to create a little php script that can make my life a bit easier. Basically, I am going to have 21 text fields on a page where I am going to input 20 different numbers. In the last field I will enter a number let's call it the TOTAL AMMOUNT. All I want the script to do is to point out which numbers from the 20 fields added up will come up to TOTAL AMMOUNT. Example: field1= 25.23 field2= 34.45 field3= 56.67 field4= 63.54 field5= 87.54 .... field20= 4.2 Total Ammount= 81.90 Output: field1+fields3=81.90 Some of the fields might have 0 as value because sometimes I only need to enter 5-15 fields and the maximum will be 20. If someone can help me out with the php code for this, will be greatly appreciated.

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  • Formating phone numbers

    - by Sven
    Our customers often fill out "incorrect" formated phone-numbers. Do anyone know if there is any lib or standard to convert numbers into a more international style? This is a Swedish example but we have customers around the globe and i don't what to manually handle implementations for everyone. input often is like this: 0555 11122 and the wanted result is something like this: +46(0)555-11122 I can do the formating myself but different countries have different variations and systems so a C/Java/C# lib or a standard method to handle this would be great.

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  • Count the number of ways in which a number 'A' can be broken into a sum of 'B' numbers such that all numbers are co-prime to 'C'

    - by rajneesh2k10
    I came across the solution of a problem which involve dynamic-programming approach, solved using a three dimensional matrix. Link to actual problem is: http://community.topcoder.com/stat?c=problem_statement&pm=12189&rd=15177 Solution to this problem is here under MuddyRoad2: http://apps.topcoder.com/wiki/display/tc/SRM+555 In the last paragraph of explanation, author describes a dynamic programming approach to count the number of ways in which a number 'A' can be broken into a sum of 'B' numbers (not necessarily different), such that every number is co-prime to 3 and the order in which these numbers appear does matter. I am not able to grasp that approach. Can anyone help me understand how DP is acting here. I can't understand what is a state here and how it is derived from the previous state.

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  • Sorting 1 million 8-digit numbers in 1MB of RAM

    - by Favourite Chigozie Onwuemene
    I have a computer with 1M of RAM and no other local storage. I must use it to accept 1 million 8-digit decimal numbers over a TCP connection, sort them, and then send the sorted list out over another TCP connection. The list of numbers may contain duplicates, which I must not discard. The code will be placed in ROM, so I need not subtract the size of my code from the 1M. I already have code to drive the ethernet port and handle TCP/IP connections, and it requires 2k for its state data, including a 1k buffer via which the code will read and write data. Is there a solution to this problem?

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  • Replace text in code with counting numbers

    - by Gpx
    Hi, due to testing and time measuring i have to write some kind of log into existing c# winforms code in Visual Studio 2010. I want to hold the changes and the work very small so my question is about replacing text in my call by counting numbers. Lets say i want to past a line like Log.WriteLine(position) many times in the code and then replace "position" with numbers starting from 1 to n in on turn. I cant use a counter in this case because of many loops i don´t get the right position. Thanks for any suggestions, Gpx

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  • C++ function for picking from a list where each element has a distinct probability

    - by Stuart
    I have an array of structs and one of the fields in the struct is a float. I want to pick one of the structs where the probability of picking it is relative to the value of the float. ie struct s{ float probability; ... } sArray s[50]; What is the fastest way to decide which s to pick? Is there a function for this? If I knew the sum of all the probability fields (Note it will not be 1), then could I iterate through each s and compare probability/total_probability with a random number, changing the random number for each s? ie if( (float) (rand() / RAND_MAX) < probability)...

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  • Pulling international street addresses / phone numbers from free-form text

    - by spitzanator
    Hey, folks. I'm looking for some regular expressions to help grab street addresses and phone numbers from free-form text (a la Gmail). Given some text: "John, I went to the store today, and it was awesome! Did you hear that they moved to 500 Green St.? ... Give me a call at +14252425424 when you get a chance." I'd like to be able to pull out: 500 Green St. (recognized as a street address) +14252425424 (recognized as a phone number) What makes this problem easier is that I don't care about parsing text that gets pulled out. That is, I don't care that Green is the name of the road or that 425 is the area code. I just want to grab strings that "look like" addresses or telephone numbers. Unfortunately, this needs to work internationally, as best as possible. Anyone have any leads? Thanks!

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  • autoTab and allowed only numbers

    - by Abu Hamzah
    is there any easy way of implementing two feature 1) auto tab and 2) allowed only numbers i have a SSN box below as soon as the user enter three digits will skip to the next .. so on and so forth..... <TR> <TD nowrap><b>Social Security Number</b></TD> <TD align="left" nowrap colspan="4"> <INPUT NAME= "SSN1" TYPE= "TEXT" SIZE= "3" MAXLENGTH= "3" VALUE= ""> <INPUT NAME= "SSN2" TYPE= "TEXT" SIZE= "2" MAXLENGTH= "2" VALUE= ""> <INPUT NAME= "SSN3" TYPE= "TEXT" SIZE= "4" MAXLENGTH= "4" VALUE= ""> </TD> </tr> also i wanted to restrict to have only numbers.

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  • remove the spaces...

    - by tekknolagi
    !/usr/bin/python import random lower_a = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z'] upper_a = ['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z'] num = ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9'] all = [] all = " ".join("".join(lower_a) + "".join(upper_a) + "".join(num)) all = all.split() x = 0 while x < 10: for i in range(7): a = random.choice(all) print a, print x += 1 what i want to do is remove the spaces from the output what it gives now is Z 3 a A I K R G B i N 9 c E v g E r A N 8 e B 6 d v H O c a V 8 c x y b g 2 W a T T f 8 H T r 6 E p D K l 5 p u x q 8 P Z 9 T n I W X n B Q

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  • fastest method for minimum of two numbers

    - by user85030
    I was going through mit's opencourseware related to performance engineering. The quickest method (requiring least number of clock cycles) for finding the minimum of two numbers(say x and y) is stated as: min= y^((x^y) & -(x<y)) The output of the expression x < y can be 0 or 1 (assuming C is being used) which then changes to -0 or -1. I understand that xor can be used to swap two numbers. Questions: 1. How is -0 different from 0 and -1 in terms of binary? 2. How is that result used with the and operator to get the minimum? Thanks in advance.

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  • Multiplying numbers on horizontal, vertial, and diagonal lines

    - by untwisted
    I'm currently working on a project Euler problem (www.projecteuler.net) for fun but have hit a stumbling block. One of the problem provides a 20x20 grid of numbers and asks for the greatest product of 4 numbers on a straight line. This line can be either horizontal, vertical, or diagonal. Using a procedural language I'd have no problem solving this, but part of my motivation for doing these problems in the first place is to gain more experience and learn more Haskell. As of right now I'm reading in the grid and converting it to a list of list of ints, eg -- [[Int]]. This makes the horizontal multiplication trivial, and by transposing this grid the vertical also becomes trivial. The diagonal is what is giving me trouble. I've thought of a few ways where I could use explicit array slicing or indexing, to get a solution, but it seems overly complicated and hackey. I believe there is probably an elegant, functional solution here, and I'd love to hear what others can come up with.

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  • Python - read numbers from text file and put into list

    - by user1647372
    So like the title says im starting to learn some python and im having trouble picking up on this technique. What I need to accomplish is to read in some numbers and store them in a list. The text file looks like the following: 0 0 3 50 50 100 4 20 Basically these are coordinates and directions to be used for python's turtle to make shapes. I got that part down the only problem is getting them in a correct format. So what I can not figure out is how to get those numbers from the file into [ [0, 0, 3, 50], [50, 100, 4, 20] ] A list, with each four coordinates being a list in that one big list. Heres my attempt but it as I said I need some help - thank you. polyShape=[] infile = open(name,"r") num = int(infile.readline(2)) while num != "": polyShape.append(num) num = int(infile.readline(2)) infile.close()

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  • Interview Q: given an array of numbers, return array of products of all other numbers (no division)

    - by polygenelubricants
    I was asked this question in a job interview, and I'd like to know how others would solve it. I'm most comfortable with Java, but solutions in other languages are welcome. Given an array of numbers, nums, return an array of numbers products, where products[i] is the product of all nums[j], j != i. Input : [1, 2, 3, 4, 5] Output: [(2*3*4*5), (1*3*4*5), (1*2*4*5), (1*2*3*5), (1*2*3*4)] = [120, 60, 40, 30, 24] You must do this in O(N) without using division.

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  • Random DNS Client Issue with BIND9/Windows Server 2003 DNS

    - by upkels
    Within our office, we have a local server running DNS, for internal related "domains", (e.g. .internal, .office, .lan, .vpn, etc.). Randomly, only the hosts configured with those extensions will stop resolving on the Windows-based workstations. Sometimes it'll work for a couple weeks without issue on one machine, then suddenly stop working, or it'll happen on another 15 times per day. It's completely random for all workstations. When troubleshooting, I have opened up a command prompt, and issued various nslookup commands for some of these hosts, and they resolve, however I've been told that nslookup uses different "libraries" for name resolution than other applications such as web browsers, email clients, etc. The only solution thus far, is manually restarting the Windows DNS Client on each workstation when this happens. Issuing the ipconfig /flushdns command multiple times helps every now and then, but is not successful enough to even attempt before restarting the DNS Client. I have tried two different DNS servers; BIND9, and Windows Server 2003 R2 DNS, and the behavior is the same. We have a single Netgear JGS524 switch all workstations and servers are connected to within the office, and a Linksys SR224G switch in another department with workstations attached.

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  • Random MKAnnotationView is tapped when there are overlapping annotations

    - by Alexandre Gellibert
    I cannot believe this bug/problem doesn't have any solution! In my iphone application, I'm using MapKit with MKMapView and custom MKAnnotationView. The problem is when annotations overlap (in my app, annotations are photos and those photos may overlap) and when you tap on the annotation that appears on front, other annotation (on back) receives the event (seems to be random). I didn't find any way to send the event to the front annotation. Z ordering and Order of overlapping annotations questions on stackoverflow did not help me that much. Please any idea is welcome (even ugly ones)! Here's some of my code (nothing fancy, very common): CustomAnnotation.h @interface CustomAnnotation : NSObject <MKAnnotation> { @private CustomAnnotationView* view; } @property (nonatomic, retain) CustomAnnotationView* view; @end CustomAnnotation.m @implementation CustomAnnotation @synthetize view; CustomAnnotationView.h @interface CustomAnnotationView : MKAnnotationView { } @end CustomAnnotationView.m @implementation CustomAnnotationView - (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event{ // Do something related to the annotation tapped } @end Main class ... // Annotations are added and some of them overlaps with others. - (void)addAnnotation:(CustomAnnotation*)annotation { [map addAnnotation:annotation]; } ... - (MKAnnotationView *)mapView:(MKMapView *)mapView viewForAnnotation:(id <MKAnnotation>)annotation { NSString* identifier = getIdentifierFromAnnotation(annotation); CustomAnnotationView* view; if(!(view = (CustomAnnotationView*)[map dequeueReusableAnnotationViewWithIdentifier:identifier])) { view = [[CustomAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier: identifier]; [(CustomAnnotation*)annotation setView:view]; [view release]; } return view; }

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  • ASP.Net MVC: "Random" URLs getting generated by URL.Action

    - by Daniel Magliola
    I have 2 very similar routes, just because i'm trying to generate two different URLs for the same resource (same Controller/Action), and both are very similar. These are the routes definitions: routes.MapRoute("Post2.Mp3", "sites/{siteSlug}/post/{brand}/aconstant-{slug}.mp3", new { controller = "Posts", action = "Mp3" }, new { siteSlug = @"[A-Za-z0-9-_]+", slug = @"[^(aconstant\-)][A-Za-z0-9-_]+", brand = @"[A-Za-z0-9-_]+" }); routes.MapRoute("Post.Mp3", "sites/{siteSlug}/post/{slug}.mp3", new { controller = "Posts", action = "Mp3" }, new { siteSlug = @"[A-Za-z0-9-_]+", slug = @"[A-Za-z0-9-_]+" }); "brand" is going to be my site name, which is the same as "aconstant" in those routes. Now, if I try this: Url.Action("ShowMp3", "Posts", new { siteSlug = post.Site.Slug, slug = post.Slug, origin = "origfeedwithaudio", brand = "aconstant" }) sometimes I get the URL I expect: /sites/site-Name/post/aconstant/aconstant-post-Name.mp3 but sometimes, I get this: /sites/site-Name/post/post-Name.mp3?brand=aconstant By sometimes, I mean that different sets of "slugs" give me one or the other. I haven't seen the same set of slugs give me different URLs. I haven't found any reasonable rule for when i'm getting one or the other, it seems random. What is going on here? How can I be getting different URLs based on esentially the same arguments? Thanks! Daniel

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  • CakePHP 1.3 and Uploadifive/Uploadify - Change Upload Filename to a random string

    - by CaboONE
    I have somehow implemented UPLOADIFIVE in my CakePHP application. Everything seems to work great including uploading multiple files and inserting the correct information in the Database. Based on the following code, I would like to UPLOAD AND SAVE EVERY FILE WITH A RANDOM NAME TAKING INTO ACCOUNT THE CURRENT DATE OR SOMETHING SIMILAR. How could I accomplish this? In my Photos Controller I have the following function: // This function is called at every file upload. It uploads the file onto the server // and save the corresponding image name, etc, to the database table `photos`. function upload() { $uploadDir = '/img/uploads/photos/'; if (!empty($_FILES)) { debug($_FILES); $tempFile = $_FILES['Filedata']['tmp_name'][0]; $uploadDir = $_SERVER['DOCUMENT_ROOT'] . $uploadDir; $targetFile = $uploadDir . $_FILES['Filedata']['name'][0]; // Validate the file type $fileTypes = array('jpg', 'jpeg', 'gif', 'png'); // Allowed file extensions $fileParts = pathinfo($_FILES['Filedata']['name'][0]); // Validate the filetype if (in_array($fileParts['extension'], $fileTypes)) { // Save the file move_uploaded_file($tempFile,$targetFile); $_POST['image'] = $_FILES['Filedata']['name'][0]; $this->Photo->create(); if ($this->Photo->save($_POST)) { $this->Session->setFlash($targetFile, 'default', array('class' => 'alert_success')); $this->redirect(array('action' => 'index')); } } else { // The file type wasn't allowed //echo 'Invalid file type.'; $this->Session->setFlash(__('The photo could not be saved. Please, try again.', true)); } } } In my View file - admin_add.ctp I have added the following function $('#file_upload').uploadifive({ 'auto' : false, 'uploadScript' : '/photos/upload', 'buttonText' : 'BROWSE FILES', 'method' : 'post', 'onAddQueueItem' : function(file) { this.data('uploadifive').settings.formData = { 'photocategory_id' : $('#PhotoPhotocategoryId').val() }; } }); <input type="file" name="file_upload" id="file_upload" />

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  • Cassandra random read speed

    - by Jody Powlette
    We're still evaluating Cassandra for our data store. As a very simple test, I inserted a value for 4 columns into the Keyspace1/Standard1 column family on my local machine amounting to about 100 bytes of data. Then I read it back as fast as I could by row key. I can read it back at 160,000/second. Great. Then I put in a million similar records all with keys in the form of X.Y where X in (1..10) and Y in (1..100,000) and I queried for a random record. Performance fell to 26,000 queries per second. This is still well above the number of queries we need to support (about 1,500/sec) Finally I put ten million records in from 1.1 up through 10.1000000 and randomly queried for one of the 10 million records. Performance is abysmal at 60 queries per second and my disk is thrashing around like crazy. I also verified that if I ask for a subset of the data, say the 1,000 records between 3,000,000 and 3,001,000, it returns slowly at first and then as they cache, it speeds right up to 20,000 queries per second and my disk stops going crazy. I've read all over that people are storing billions of records in Cassandra and fetching them at 5-6k per second, but I can't get anywhere near that with only 10mil records. Any idea what I'm doing wrong? Is there some setting I need to change from the defaults? I'm on an overclocked Core i7 box with 6gigs of ram so I don't think it's the machine. Here's my code to fetch records which I'm spawning into 8 threads to ask for one value from one column via row key: ColumnPath cp = new ColumnPath(); cp.Column_family = "Standard1"; cp.Column = utf8Encoding.GetBytes("site"); string key = (1+sRand.Next(9)) + "." + (1+sRand.Next(1000000)); ColumnOrSuperColumn logline = client.get("Keyspace1", key, cp, ConsistencyLevel.ONE); Thanks for any insights

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