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  • Quickest way to compare a buch of array or list of values.

    - by zapping
    Can you please let me know on the quickest and efficient way to compare a large set of values. Its like there are a list of parent codes(string) and each code has a series of child values(string). The child lists have to be compared with each other and find out duplicates and count how many times they repeat. code1(code1_value1, code1_value2, code3_value3, ..., code1_valueN); code2(code2_value1, code1_value2, code2_value3, ..., code2_valueN); code3(code2_value1, code3_value2, code3_value3, ..., code3_valueN); . . . codeN(codeN_value1, codeN_value2, codeN_value3, ..., codeN_valueN); The lists are huge say like there are 100 parent codes and each has about 250 values in them. There will not be duplicates within a code list. Doing it in java and the solution i could figure out is. Store the values of first set of code in as codeMap.put(codeValue, duplicateCount). The count initialized to 0. Then compare the rest of the values with this. If its in the map then increment the count otherwise append it to the map. The downfall of this is to get the duplicates. Another iteration needs to be performed on a very large list. An alternative is to maintain another hashmap for duplicates like duplicateCodeMap.put(codeValue, duplicateCount) and change the initial hashmap to codeMap.put(codeValue, codeValue). Speed is what is requirement. Hope one of you can help me with it.

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  • PHP Arrays: Pop an array of single-element arrays into one array.

    - by Rob Drimmie
    Using a proprietary framework, I am frequently finding myself in the situation where I get a resultset from the database in the following format: array(5) { [0] => array(1) { ["id"] => int(241) } [1] => array(1) { ["id"] => int(2) } [2] => array(1) { ["id"] => int(81) } [3] => array(1) { ["id"] => int(560) } [4] => array(1) { ["id"] => int(10) } } I'd much rather have a single array of ids, such as: array(5) { [0] => int(241) [1] => int(2) [2] => int(81) [3] => int(560) [4] => int(10) } To get there, I frequently find myself writing: $justIds = array(); foreach( $allIds as $id ) { $justIds[] = $id["id"]; } Is there a more efficient way to do this?

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  • Optimized 2D Tile Scrolling in OpenGL

    - by silicus
    Hello, I'm developing a 2D sidescrolling game and I need to optimize my tiling code to get a better frame rate. As of right now I'm using a texture atlas and 16x16 tiles for 480x320 screen resolution. The level scrolls in both directions, and is significantly larger than 1 screen (thousands of pixels). I use glTranslate for the actual scrolling. So far I've tried: Drawing only the on-screen tiles using glTriangles, 2 per square tile (too much overhead) Drawing the entire map as a Display List (great on a small level, way to slow on a large one) Partitioning the map into Display Lists half the size of the screen, then culling display lists (still slows down for 2-directional scrolling, overdraw is not efficient) Any advice is appreciated, but in particular I'm wondering: I've seen Vertex Arrays/VBOs suggested for this because they're dynamic. What's the best way to take advantage of this? If I simply keep 1 screen of vertices plus a bit of overdraw, I'd have to recopy the array every few frames to account for the change in relative coordinates (shift everything over and add the new rows/columns). If I use more overdraw this doesn't seem like a big win; it's like the half-screen display list idea. Does glScissor give any gain if used on a bunch of small tiles like this, be it a display list or a vertex array/VBO Would it be better just to build the level out of large textures and then use glScissor? Would losing the memory saving of tiling be an issue for mobile development if I do this (just curious, I'm currently on a PC)? This approach was mentioned here Thanks :)

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  • Project Euler #119 Make Faster

    - by gangqinlaohu
    Trying to solve Project Euler problem 119: The number 512 is interesting because it is equal to the sum of its digits raised to some power: 5 + 1 + 2 = 8, and 8^3 = 512. Another example of a number with this property is 614656 = 28^4. We shall define an to be the nth term of this sequence and insist that a number must contain at least two digits to have a sum. You are given that a2 = 512 and a10 = 614656. Find a30. Question: Is there a more efficient way to find the answer than just checking every number until a30 is found? My Code int currentNum = 0; long value = 0; for (long a = 11; currentNum != 30; a++){ //maybe a++ is inefficient int test = Util.sumDigits(a); if (isPower(a, test)) { currentNum++; value = a; System.out.println(value + ":" + currentNum); } } System.out.println(value); isPower checks if a is a power of test. Util.sumDigits: public static int sumDigits(long n){ int sum = 0; String s = "" + n; while (!s.equals("")){ sum += Integer.parseInt("" + s.charAt(0)); s = s.substring(1); } return sum; } program has been running for about 30 minutes (might be overflow on the long). Output (so far): 81:1 512:2 2401:3 4913:4 5832:5 17576:6 19683:7 234256:8 390625:9 614656:10 1679616:11 17210368:12 34012224:13 52521875:14 60466176:15 205962976:16 612220032:17

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  • Accessing HTML DOM elements from javascript using `.childNodes`

    - by Martin
    I'm wondering about the .childNodes property, I have the code below, and for some reason I get 18 children, while 6 are HTMLInputElements as expected, and the rest are undefined. What is this about? Is there an efficient way to iterate over the input elements? <html> <head> <script> window.onload = function(e){ form = document.getElementById('myForm'); alert(form.childNodes.length); for(i=0; i<form.childNodes.length; i++){ alert(form[i]); } } </script> </head> <body> <form id='myForm' action="haha" method="post"> Name: <input type="text" id="fnameAdd" name="name" /><br /> Phone1: <input type="text" id="phone1Add" name="phone1" /><br /> Phone2: <input type="text" id="phone2Add" name="phone2" /><br /> E-Mail: <input type="text" id="emailAdd" name="email" /><br /> Address: <input type="text" id="addressAdd" name="address" /><br /> <input type="submit" value="Save" /> </body> </html>

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  • Is programming overrated?

    - by aengine
    [Subjective and intended to be a community wiki] I am sorry for such an offensive question: But here are my arguments Most of the progress in "computing" has came from non-programming sources. i.e. People invented faster microprocessors and better routers and novel memory devices. I dont think on average people are writting more efficient programs than those written 10 years ago. And the newer and popular languages are infact slower than C. though speed is one of the lesser criterias. Most of the progress came from novel paradigms. Web, Internet, Cloud computing and Social networking are novel paradigms and did not involve progress in programming as such. Heck even facebook was written in PHP and not some extreme language. Though it did face scalability issues (same with twitter) but i believe money and better programmers (who came in much later) took care of that. Thus ideating capability trumped programming capability/ Even things like Map-Reduce, Column oriented database and Probablistic algorithms (E.g. bloom filters) came from hardcore Algorithms research, rather than some programming convention. Thus my final point is why programming skill is so overstressed? To point a recent example about how only 10% of programmers can "write code" (binary search) without debugging. Isnt it a bit hypocritical, considering your real successs lies in coming up with better algorithm or a novel feature rather than getting right first time???

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  • Find messages from certain key till certain key while being able to remove stale keys.

    - by Alfred
    My problem Let's say I add messages to some sort of datastructure: 1. "dude" 2. "where" 3. "is" 4. "my" 5. "car" Asking for messages from index[4,5] should return: "my","car". Next let's assume that after a while I would like to purge old messages because they aren't useful anymore and I want to save memory. Let's say at time x messages[1-3] became stale. I assume that it would be most efficient to just do the deletion once every x seconds. Next my datastructure should contain: 4. "my" 5. "car" My solution? I was thinking of using a concurrentskiplistset or concurrentskiplist map. Also I was thinking of deleting the old messages from inside a newSingleThreadScheduledExecutor. I would like to know how you would implement(efficiently/thread-safe) this or maybe use a library?

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  • Adding new elements into DOM using JavaScript (appendChild)

    - by KatieK
    I sometimes need to add elements (such as a new link and image) to an existing HTML page, but I only have access to a small portion of the page far from where I need to insert elements. I want to use DOM based JavaScript techniques, and I must avoid using document.write(). Thus far, I've been using something like this: // Create new image element var newImg = document.createElement("img"); newImg.src = "images/button.jpg"; newImg.height = "50"; newImg.width = "150"; newImg.alt = "Click Me"; // Create new link element var newLink = document.createElement("a"); newLink.href = "/dir/signup.html"; // Append new image into new link newLink.appendChild(newImg); // Append new link (with image) into its destination on the page document.getElementById("newLinkDestination").appendChild(newLink); Is there a more efficient way that I could use to accomplish the same thing? It all seems necessary, but I'd like to know if there's a better way I could be doing this. Thanks!

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  • What is the best way to get a reference to a spring bean in the backend layers?

    - by java_pill
    I have two spring config files and I'm specifying them in my web.xml as in below. web.xml snippet .. <context-param> <param-name>contextConfigLocation</param-name> <param-value>WEB-INF/classes/domain-context.xml WEB-INF/classes/client-ws.xml</param-value> </context-param> <listener> <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class> </listener> .. From my domain object I have to invoke a Web Service Client and in order to get a reference to the Web Service client I do this: ApplicationContext context = new ClassPathXmlApplicationContext("client-ws.xml"); //b'cos I don't want to use WebApplicationContextUtils ProductServiceClient client = (ProductServiceClient) context.getBean("productClient"); .. client.find(prodID); //calls a Web Service .. However, I have concerns that looking up the client-ws.xml file and getting a reference to the ProductServiceClient bean is not efficient. I thought of getting it using WebApplicationContextUtils. However, I don't want my domain objects to have a dependency on the ServletContext (a web/control layer object) because WebApplicationContextUtils depends on ServletContext. What is the best way to get a reference to a spring bean in the backend layers? Thanks!

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  • Parallelizing L2S Entity Retrieval

    - by MarkB
    Assuming a typical domain entity approach with SQL Server and a dbml/L2S DAL with a logic layer on top of that: In situations where lazy loading is not an option, I have settled on a convention where getting a list of entities does not also get each item's child entities (no loading), but getting a single entity does (eager loading). Since getting a single entity also gets children, it causes a cascading effect in which each child then gets its children too. This sounds bad, but as long as the model is not too deep, I usually don't see performance problems that outweigh the benefits of the ease of use. So if I want to get a list in which each of the items is fully hydrated with children, I combine the GetList and GetItem methods. So I'll get a list and then loop through it getting each item with the full cascade. Even this is generally acceptable in many of the projects I've worked on - but I have recently encountered situations with larger models and/or more data in which it needs to be more efficient. I've found that partitioning the loop and executing it on multiple threads yields excellent results. In my first experiment with a list of 50 items from one particular project, I did 5 threads of 10 items each and got a 3X improvement in time. Of course, the mileage will vary depending on the project but all else being equal this is clearly a big opportunity. However, before I go further, I was wondering what others have done that have already been through this. What are some good approaches to parallelizing this type of thing?

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  • Image Gurus: Optimize my Python PNG transparency function

    - by ozone
    I need to replace all the white(ish) pixels in a PNG image with alpha transparency. I'm using Python in AppEngine and so do not have access to libraries like PIL, imagemagick etc. AppEngine does have an image library, but is pitched mainly at image resizing. I found the excellent little pyPNG module and managed to knock up a little function that does what I need: make_transparent.py pseudo-code for the main loop would be something like: for each pixel: if pixel looks "quite white": set pixel values to transparent otherwise: keep existing pixel values and (assuming 8bit values) "quite white" would be: where each r,g,b value is greater than "240" AND each r,g,b value is within "20" of each other This is the first time I've worked with raw pixel data in this way, and although works, it also performs extremely poorly. It seems like there must be a more efficient way of processing the data without iterating over each pixel in this manner? (Matrices?) I was hoping someone with more experience in dealing with these things might be able to point out some of my more obvious mistakes/improvements in my algorithm. Thanks!

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  • so i got an econ degree...computing science or software systems (software engineering) degree ?

    - by sofreakinghigh
    okay so here's the story. i want to work in developing software (not QA or writing tests), so although I am currently starting computing science this summer, i came across Software Systems (aka s.e.) program which is "applied" but under computing science.... so what is the difference between the 2 disciplines ? if i choose software engineering, would it require more in depth expertise with calculus (i fail at it), and more coding time ? i am looking for a way to write better and more efficient code. I want to go to school, so i wont get lazy. i want to pick a program that would directly aid me in writing and developing software. graduating with an Econ degree in last year doesn't really help in landing jobs requiring comp sci/software engineering degrees....i should've studied harder in Economics (and maybe land a job) but i was obsessed with learning how to program with various languages since day 1 at University, but i didn't think i was smart enough to pass comp sci courses (so i just relied on books + irc...) and my parents said software jobs are being outsourced to India so i thought this obsession was just a "phase" and i should keep it as a hobby. but yes, it's quite funny why i hadn't pursued this field much earlier. as Joelonsoftware.com says economics degree starts with a bang (microeconomics the only course you only need really)....predicting stock prices (ridiculous!) + realizing China's potential power to meltdown US economy and vice versa + interest rate is inversely related to bond premium which is inversely related to stock market it would absolutely awesome if there was a program that combined finance + programming.

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  • Long primitive or AtomicLong for a counter?

    - by Rich
    Hi I have a need for a counter of type long with the following requirements/facts: Incrementing the counter should take as little time as possible. The counter will only be written to by one thread. Reading from the counter will be done in another thread. The counter will be incremented regularly (as much as a few thousand times per second), but will only be read once every five seconds. Precise accuracy isn't essential, only a rough idea of the size of the counter is good enough. The counter is never cleared, decremented. Based upon these requirements, how would you choose to implement your counter? As a simple long, as a volatile long or using an AtomicLong? Why? At the moment I have a volatile long but was wondering whether another approach would be better. I am also incrementing my long by doing ++counter as opposed to counter++. Is this really any more efficient (as I have been led to believe elsewhere) because there is no assignment being done? Thanks in advance Rich

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  • Python : How do you find the CPU consumption for a piece of code?

    - by Yugal Jindle
    Background: I have a django application, it works and responds pretty well on low load, but on high load like 100 users/sec, it consumes 100% CPU and then due to lack of CPU slows down. Problem : Profiling the application gives me time taken by functions. This time increases on high load. Time consumed may be due to complex calculation or for waiting for CPU. so, how to find the CPU cycles consumed by a piece of code ? Since, reducing the CPU consumption will increase the response time. I might have written extremely efficient code and need to add more CPU power OR I might have some stupid code taking the CPU and causing the slow down ? Any help is appreciated ! Update: I am using Jmeter to profile my webapp, it gives me a throughput of 2 requests/sec. [ 100 users] I get a average time of 36 seconds on 100 request vs 1.25 sec time on 1 request. More Info Configuration Nginx + Uwsgi with 4 workers No database used, using a responses from a REST API On 1st hit the response of REST API gets cached, therefore doesn't makes a difference. Using ujson for json parsing. Curious to Know: Python-Django is used by so many orgs for so many big sites, then there must be some high end Debug / Memory-CPU analysis tools. All those I found were casual snippets of code that perform profiling.

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  • Is there a way to receive data as unsigned char over UDP on Qt?

    - by user269037
    I need to send floating point numbers using a UDP connection to a Qt application. Now in Qt the only function available is qint64 readDatagram ( char * data, qint64 maxSize, QHostAddress * address = 0, quint16 * port = 0 ) which accepts data in the form of signed character buffer. I can convert my float into a string and send it but it will obviously not be very efficient converting a 4 byte float into a much longer sized character buffer. I got hold of these 2 functions to convert a 4 byte float into an unsinged 32 bit integer to transfer over network which works fine for a simple C++ UDP program but for Qt I need to receive the data as unsigned char. Is it possible to avoid converting the floatinf point data into a string and then sending it? uint32_t htonf(float f) { uint32_t p; uint32_t sign; if (f < 0) { sign = 1; f = -f; } else { sign = 0; } p = ((((uint32_t)f)&0x7fff)<<16) | (sign<<31); // Whole part and sign. p |= (uint32_t)(((f - (int)f) * 65536.0f))&0xffff; // Fraction. return p; } float ntohf(uint32_t p) { float f = ((p>>16)&0x7fff); // Whole part. f += (p&0xffff) / 65536.0f; // Fraction. if (((p>>31)&0x1) == 0x1) { f = -f; } // Sign bit set. return f; }

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  • Is it possible to create multi-tiered WHERE statements in mySQL

    - by Brendan
    I'm currently developing a program that will generate reports based upon lead data. My issue is that I'm running 3 queries for something that I would like to only have to run one query for. For instance, I want to gather data for leads generated in the past day submission_date > (NOW() - INTERVAL 1 DAY) and I would like to find out how many total leads there were, and how many sold leads there were in that timeframe. (sold=1 / sold=0). The issue comes with the fact that this query is currently being done with 2 queries, one with WHEREsold= 1 and one with WHEREsold= 0. This is all well and good, but when I want to generate this data for the past day,week,month,year,and all time I will have to run 10 queries to obtain this data. I feel like there HAS to be a more efficient way of doing this. I know I can create a mySQL function for this, but I don't see how this could solve the problem. Thanks!!

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  • Interview Q: sorting an almost sorted array (elements misplaced by no more than k)

    - by polygenelubricants
    I was asked this interview question recently: You're given an array that is almost sorted, in that each of the N elements may be misplaced by no more than k positions from the correct sorted order. Find a space-and-time efficient algorithm to sort the array. I have an O(N log k) solution as follows. Let's denote arr[0..n) to mean the elements of the array from index 0 (inclusive) to N (exclusive). Sort arr[0..2k) Now we know that arr[0..k) are in their final sorted positions... ...but arr[k..2k) may still be misplaced by k! Sort arr[k..3k) Now we know that arr[k..2k) are in their final sorted positions... ...but arr[2k..3k) may still be misplaced by k Sort arr[2k..4k) .... Until you sort arr[ik..N), then you're done! This final step may be cheaper than the other steps when you have less than 2k elements left In each step, you sort at most 2k elements in O(k log k), putting at least k elements in their final sorted positions at the end of each step. There are O(N/k) steps, so the overall complexity is O(N log k). My questions are: Is O(N log k) optimal? Can this be improved upon? Can you do this without (partially) re-sorting the same elements?

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  • Sorting by some field and fetching whole tree from DB

    - by Niaxon
    Hello everyone, I am trying to do file browser in a tree form and have a problem to sort it somehow. I use PHP and MySQL for that. I've created mixed (nested set + adjacency) table 'element' with the following fields: element_id, left_key, right_key, level, parent_id, element_name, element_type (enum: 'folder','file'), element_size. Let's not discuss right now that it is better to move information about element (name, type, size) into other table. Function to scan specified directory and fill table work correctly. Noteworthy, i am adding elements to tree in specific order: folders first and only files. After that i can easily fetch and display whole table on the page using simple query: SELECT * FROM element WHERE 1=1 ORDER BY left_key With the result of that query and another function i can generate correct html code (<ul><li>... and so on). Now back to the question (finally, huh?). I am struggling to add sorting functionality. For example i want to order my result by size. Here i need to keep in my mind whole hierarchy of tree and rule: folders first, files later. I believe i can do that by generating in PHP recursive query: SELECT * FROM element WHERE parent_id = {$parentId} ORDER BY element_type (so folders would be first), size (or name for example) After that for each result which is folder i will send another query to get it's content. Also it's possible to fetch whole tree by left_key and after that sort it in PHP as array but i guess that would be worse :) I wonder if there is better and more efficient way to do such thing?

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  • Why does the order of the loops affect performance when iterating over a 2D array? [closed]

    - by Mark
    Possible Duplicate: Which of these two for loops is more efficient in terms of time and cache performance Below are two programs that are almost identical except that I switched the i and j variables around. They both run in different amounts of time. Could someone explain why this happens? Version 1 #include <stdio.h> #include <stdlib.h> main () { int i,j; static int x[4000][4000]; for (i = 0; i < 4000; i++) { for (j = 0; j < 4000; j++) { x[j][i] = i + j; } } } Version 2 #include <stdio.h> #include <stdlib.h> main () { int i,j; static int x[4000][4000]; for (j = 0; j < 4000; j++) { for (i = 0; i < 4000; i++) { x[j][i] = i + j; } } }

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  • Cleaner method for list comprehension clean-up

    - by Dan McGrath
    This relates to my previous question: Converting from nested lists to a delimited string I have an external service that sends data to us in a delimited string format. It is lists of items, up to 3 levels deep. Level 1 is delimited by '|'. Level 2 is delimited by ';' and level 3 is delimited by ','. Each level or element can have 0 or more items. An simplified example is: a,b;c,d|e||f,g|h;; We have a function that converts this to nested lists which is how it is manipulated in Python. def dyn_to_lists(dyn): return [[[c for c in b.split(',')] for b in a.split(';')] for a in dyn.split('|')] For the example above, this function results in the following: >>> dyn = "a,b;c,d|e||f,g|h;;" >>> print (dyn_to_lists(dyn)) [[['a', 'b'], ['c', 'd']], [['e']], [['']], [['f', 'g']], [['h'], [''], ['']]] For lists, at any level, with only one item, we want it as a scalar rather than a 1 item list. For lists that are empty, we want them as just an empty string. I've came up with this function, which does work: def dyn_to_min_lists(dyn): def compress(x): return "" if len(x) == 0 else x if len(x) != 1 else x[0] return compress([compress([compress([item for item in mv.split(',')]) for mv in attr.split(';')]) for attr in dyn.split('|')]) Using this function and using the example above, it returns: [[['a', 'b'], ['c', 'd']], 'e', '', ['f', 'g'], ['h', '', '']] Being new to Python, I'm not confident this is the best way to do it. Are there any cleaner ways to handle this? This will potentially have large amounts of data passing through it, are there any more efficient/scalable ways to achieve this?

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  • Better way to compare neighboring cells in matrix

    - by HyperCube
    Suppose I have a matrix of size 100x100 and I would like to compare each pixel to its direct neighbor (left, upper, right, lower) and then do some operations on the current matrix or a new one of the same size. A sample code in Python/Numpy could look like the following: (the comparison 0.5 has no meaning, I just want to give a working example for some operation while comparing the neighbors) import numpy as np my_matrix = np.random.rand(100,100) new_matrix = np.array((100,100)) my_range = np.arange(1,99) for i in my_range: for j in my_range: if my_matrix[i,j+1] > 0.5: new_matrix[i,j+1] = 1 if my_matrix[i,j-1] > 0.5: new_matrix[i,j-1] = 1 if my_matrix[i+1,j] > 0.5: new_matrix[i+1,j] = 1 if my_matrix[i-1,j] > 0.5: new_matrix[i-1,j] = 1 if my_matrix[i+1,j+1] > 0.5: new_matrix[i+1,j+1] = 1 if my_matrix[i+1,j-1] > 0.5: new_matrix[i+1,j-1] = 1 if my_matrix[i-1,j+1] > 0.5: new_matrix[i-1,j+1] = 1 This can get really nasty if I want to step into one neighboring cell and start from it to do a similar task... Do you have some suggestions how this can be done in a more efficient manner? Is this even possible?

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  • C# Hook Forms / Windows / Dialogs etc. (via HWND?) to Capture Video Buffer (D3D Device?)

    - by Drax
    I am looking to create a very simple C# application which runs Full-Screen in Direct3D, and is able to grab the Desktop 'scene', mapping each Window from the Desktop to a Textured Polygon in my D3D Scene... I'm hoping to create a simplistic "3D Desktop" type of application as an experiment, and I'm wondering if there is a specific method for doing something like the following: 1)Get a list of all the Windows open on the Desktop (List of HWNDs?). 2)Grab the X,Y position of each Window, as well as the Width and Height. 3)Grab the Rendered image of each Window (magic happens here). 4)Create a new Texture/Surface in D3D using the Width and Height of the Window(s), and apply the Image we grabbed as a Texture. Is there an efficient 'best practice' for acquiring the actual image(s) being rendered to the Desktop? Is there also a 'best practice' for "extending the desktop" to a virtual second, third, etc. "desktop" and being able to swap between them, including creating a unique instance of the task-bar for each virtual desktop. Thanks a million for any suggestions!

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  • Obj-C Sending Messages Between Classes

    - by user544359
    I'm a newbie in iPhone Programming. I'm trying to send a message from one view controller to another. The idea is that viewControllerA takes information from the user and sends it to viewControllerB. viewControllerB is then supposed to display the information in a label. viewControllerA.h #import <UIKit/UIKit.h> @interface viewControllerA : UIViewController { int num; } -(IBAction)do; @end viewControllerA.m #import "viewControllerA.h" #import "viewControllerB.h" @implementation viewControllerA - (IBAction)do { //initializing int for example num = 2; viewControllerB *viewB = [[viewControllerB alloc] init]; [viewB display:num]; [viewB release]; //viewA is presented as a ModalViewController, so it dismisses itself to return to the //original view, i know it is not efficient [self dismissModalViewControllerAnimated:YES]; } - (void)dealloc { [super dealloc]; } @end viewControllerB.h #import <UIKit/UIKit.h> @interface viewControllerB : UIViewController { IBOutlet UILabel *label; } - (IBAction)openA; - (void)display:(NSInteger)myNum; @end viewControllerB.m #import "viewControllerB.h" #import "viewControllerA.h" @implementation viewControllerB - (IBAction)openA { //presents viewControllerA when a button is pressed viewControllerA *viewA = [[viewControllerA alloc] init]; [self presentModalViewController:viewA animated:YES]; } - (void)display:(NSInteger)myNum { NSLog(@"YES"); [label setText:[NSString stringWithFormat:@"%d", myNum]]; } @end YES is logged successfully, but the label's text does not change. I have made sure that all of my connections in Interface Builder are correct, in fact there are other (IBAction) methods in my program that change the text of this very label, and all of those other methods work perfectly... Any ideas, guys? You don't need to give me a full solution, any bits of information will help. Thanks.

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  • Looping Through Database Query

    - by DrakeNET
    I am creating a very simple script. The purpose of the script is to pull a question from the database and display all answers associated with that particular question. We are dealing with two tables here and there is a foreign key from the question database to the answer database so answers are associated with questions. Hope that is enough explanation. Here is my code. I was wondering if this is the most efficient way to complete this or is there an easier way? <html> <head> <title>Advise Me</title> <head> <body> <h1>Today's Question</h1> <?php //Establish connection to database require_once('config.php'); require_once('open_connection.php'); //Pull the "active" question from the database $todays_question = mysql_query("SELECT name, question FROM approvedQuestions WHERE status = active") or die(mysql_error()); //Variable to hold $todays_question aQID $questionID = mysql_query("SELECT commentID FROM approvedQuestions WHERE status = active") or die(mysql_error()); //Print today's question echo $todays_question; //Print comments associated with today's question $sql = "SELECT commentID FROM approvedQuestions WHERE status = active"; $result_set = mysql_query($sql); $result_num = mysql_numrows($result_set); for ($a = 0; $a < $result_num; $a++) { echo $sql; } ?> </body> </html>

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  • Does the Java Memory Model (JSR-133) imply that entering a monitor flushes the CPU data cache(s)?

    - by Durandal
    There is something that bugs me with the Java memory model (if i even understand everything correctly). If there are two threads A and B, there are no guarantees that B will ever see a value written by A, unless both A and B synchronize on the same monitor. For any system architecture that guarantees cache coherency between threads, there is no problem. But if the architecture does not support cache coherency in hardware, this essentially means that whenever a thread enters a monitor, all memory changes made before must be commited to main memory, and the cache must be invalidated. And it needs to be the entire data cache, not just a few lines, since the monitor has no information which variables in memory it guards. But that would surely impact performance of any application that needs to synchronize frequently (especially things like job queues with short running jobs). So can Java work reasonably well on architectures without hardware cache-coherency? If not, why doesn't the memory model make stronger guarantees about visibility? Wouldn't it be more efficient if the language would require information what is guarded by a monitor? As i see it the memory model gives us the worst of both worlds, the absolute need to synchronize, even if cache coherency is guaranteed in hardware, and on the other hand bad performance on incoherent architectures (full cache flushes). So shouldn't it be more strict (require information what is guarded by a monitor) or more lose and restrict potential platforms to cache-coherent architectures? As it is now, it doesn't make too much sense to me. Can somebody clear up why this specific memory model was choosen? EDIT: My use of strict and lose was a bad choice in retrospect. I used "strict" for the case where less guarantees are made and "lose" for the opposite. To avoid confusion, its probably better to speak in terms of stronger or weaker guarantees.

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