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  • How to get REALLY fast python over a simple loop

    - by totallymike
    I'm working on a spoj problem, INTEST. The goal is to specify the number of test cases (n) and a divisor (k), then feed your program n numbers. The program will accept each number on a newline of stdin and after receiving the nth number, will tell you how many were divisible by k. The only challenge in this problem is getting your code to be FAST because it k can be anything up to 10^7 and the test cases can be as high as 10^9. I'm trying to write it in python and having trouble speeding it up. Any ideas? import sys first_in = raw_input() thing = first_in.split() n = int(thing[0]) k = int(thing[1]) total = 0 i = 0 for line in sys.stdin: t = int(line) if t % k == 0: total += 1 print total

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  • Recieve and forward all packets to another port

    - by question
    Debian 5, iptables Server N1 Some video-streaming server without external IP. Server N2 Debian server with ip 1.1.1.1. Server N1 is configured to send videostream to 1.1.1.1:1111. How to forward all recieved packages from 1.1.1.1:1111 to another port on the same server, for example to 1.1.1.1:2222? Something like that? echo 1 > /proc/sys/net/ipv4/ip_forward iptables -t nat -A PREROUTING -i eth1 -p tcp --dport 1111 -j REDIRECT --to-port 2222

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  • How to make my WPF application as FAST as Outlook

    - by Raul Otaño
    The commons WPF applications take some time for loading medium complex views, once the view is loaded it works fine. For example in a Master - Detail view, if the Detail view is very complex and use different DataTemplates take some seconds (2-3 seconds) for load the view. When i open the Outlook application, for instance, it renders complex views and it is relative much more fast. Is there a way for increase the performance of my WPF application? Maybe a way for not loading the template's data every time that change the "master" item, and load it only one time in the app time live? i will appreciate any suggestion.

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  • How to fast rendering UITableView

    - by pubudu
    In my program has two view controller. first one has one button.and second one has tableview with custom cell. in this cell has 5 textviews. when i click button of first tableview.it shows second view controller. Its is very slow rendering table view with 5 , 6 rows.it is working well with simulator.but it is very slow with actual i pad. when i click the button i have to wait 2,3 second with button pressed status.and after it view the second view controller it also very slow rendering.i can see it render rows. [tableView dequeueReusableCellWithIdentifier:CellIdentifier]; this one also i used.when i comment this table from my second view.it navigate first view controller to second view controller very fast. how can i solve this issue?

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  • Algorithm for non-contiguous netmask match

    - by Gianluca
    Hi, I have to write a really really fast algorithm to match an IP address to a list of groups, where each group is defined using a notation like 192.168.0.0/252.255.0.255. As you can see, the bitmask can contain zeros even in the middle, so the traditional "longest prefix match" algorithms won't work. If an IP matches two groups, it will be assigned to the group containing most 1's in the netmask. I'm not working with many entries (let's say < 1000) and I don't want to use a data structure requiring a large memory footprint (let's say 1-2 MB), but it really has to be fast (of course I can't afford a linear search). Do you have any suggestion? Thanks guys. UPDATE: I found something quite interesting at http://www.cse.usf.edu/~ligatti/papers/grouper-conf.pdf, but it's still too memory-hungry for my utopic use case

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  • Detecting Xml namespace fast

    - by Anna Tjsoken
    Hello there, This may be a very trivial problem I'm trying to solve, but I'm sure there's a better way of doing it. So please go easy on me. I have a bunch of XSD files that are internal to our application, we have about 20-30 Xml files that implement datasets based off those XSDs. Some Xml files are small (<100Kb), others are about 3-4Mb with a few being over 10Mb. I need to find a way of working out what namespace these Xml files are in order to provide (something like) intellisense based off the XSD. The implementation of this is not an issue - another developer has written the code for this. But I'm not sure the best (and fastest!) way of detecting the namespace is without the use of XmlDocument (which does a full parse). I'm using C# 3.5 and the documents come through as a Stream (some are remote files). All the files are *.xml (I can detect if it was extension based) but unfortunately the Xml namespace is the only way. Right now I've tried XmlDocument but I've found it to be innefficient and slow as the larger documents are awaiting to be parsed (even the 100Kb docs). public string GetNamespaceForDocument(Stream document); Something like the above is my method signature - overloads include string for "content". Would a RegEx (compiled) pattern be good? How does Visual Studio manage this so efficiently? Another college has told me to find a fast Xml parser in C/C++, parse the content and have a stub that gives back the namespace as its slower in .NET, is this a good idea?

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  • Simple, fast SQL queries for flat files.

    - by plinehan
    Does anyone know of any tools to provide simple, fast queries of flat files using a SQL-like declarative query language? I'd rather not pay the overhead of loading the file into a DB since the input data is typically thrown out almost immediately after the query is run. Consider the data file, "animals.txt": dog 15 cat 20 dog 10 cat 30 dog 5 cat 40 Suppose I want to extract the highest value for each unique animal. I would like to write something like: cat animals.txt | foo "select $1, max(convert($2 using decimal)) group by $1" I can get nearly the same result using sort: cat animals.txt | sort -t " " -k1,1 -k2,2nr And I can always drop into awk from there, but this all feels a bit awkward (couldn't resist) when a SQL-like language would seem to solve the problem so cleanly. I've considered writing a wrapper for SQLite that would automatically create a table based on the input data, and I've looked into using Hive in single-processor mode, but I can't help but feel this problem has been solved before. Am I missing something? Is this functionality already implemented by another standard tool? Halp!

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  • Python: OSX Library for fast full screen jpg/png display

    - by Parand
    Frustrated by lack of a simple ACDSee equivalent for OS X, I'm looking to hack one up for myself. I'm looking for a gui library that accommodates: Full screen image display High quality image fit-to-screen (for display) Low memory usage Fast display Reasonable learning curve (the simpler the better) Looks like there are several choices, so which is the best? Here are some I've run across: PyOpenGL PyGame PyQT wxpython I don't have any particular experience with any of these, nor any strong desire to become an expert - I'm looking for the simplest solution. What do you recommend? [Update] For those not familiar with ACDSee, here's what it does that I care about: Simple list/thubmnail display of images in a directory Sort by name/size/type Ability to view images full screen Single-key delete while viewing full screen Move to next/previous image while viewing full screen Ability to select a group of images for: move to / copy to directory delete resize ACDSee has a bunch of niceties as well, such as remembering directories you've moved images to in the past, remembering your resize settings, displaying the total size of the images you've selected, etc. I've tried most of the options I could find (including Xee) and none of them quite get there. Please keep in mind that this is a programming/library question, not a criticism of any of the existing tools.

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  • MySQL ORDER BY DESC is fast but ASC is very slow

    - by Pepper
    Hello, I'm completely stumped on this one. For some reason when I sort this query by DESC it's super fast, but if sorted by ASC it's extremely slow. This takes about 150 milliseconds: SELECT posts.id FROM posts USE INDEX (published) WHERE posts.feed_id IN ( 4953,622,1,1852,4952,76,623,624,10 ) ORDER BY posts.published DESC LIMIT 0, 50; This takes about 32 seconds: SELECT posts.id FROM posts USE INDEX (published) WHERE posts.feed_id IN ( 4953,622,1,1852,4952,76,623,624,10 ) ORDER BY posts.published ASC LIMIT 0, 50; The EXPLAIN is the same for both queries. id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE posts index NULL published 5 NULL 50 Using where I've tracked it down to "USE INDEX (published)". If I take that out it's the same performance both ways. But the EXPLAIN shows the query is less efficient overall. id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE posts range feed_id feed_id 4 \N 759 Using where; Using filesort And here's the table. CREATE TABLE `posts` ( `id` int(20) NOT NULL AUTO_INCREMENT, `feed_id` int(11) NOT NULL, `post_url` varchar(255) NOT NULL, `title` varchar(255) NOT NULL, `content` blob, `author` varchar(255) DEFAULT NULL, `published` int(12) DEFAULT NULL, `updated` datetime NOT NULL, `created` datetime NOT NULL, PRIMARY KEY (`id`), UNIQUE KEY `post_url` (`post_url`,`feed_id`), KEY `feed_id` (`feed_id`), KEY `published` (`published`) ) ENGINE=InnoDB AUTO_INCREMENT=196530 DEFAULT CHARSET=latin1; Is there a fix for this? Thanks!

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  • Why do my CouchDB databases grow so fast?

    - by konrad
    I was wondering why my CouchDB database was growing to fast so I wrote a little test script. This script changes an attributed of a CouchDB document 1200 times and takes the size of the database after each change. After performing these 1200 writing steps the database is doing a compaction step and the db size is measured again. In the end the script plots the databases size against the revision numbers. The benchmarking is run twice: The first time the default number of document revision (=1000) is used (_revs_limit). The second time the number of document revisions is set to 1. The first run produces the following plot The second run produces this plot For me this is quite an unexpected behavior. In the first run I would have expected a linear growth as every change produces a new revision. When the 1000 revisions are reached the size value should be constant as the older revisions are discarded. After the compaction the size should fall significantly. In the second run the first revision should result in certain database size that is then keeps during the following writing steps as every new revision leads to the deletion of the previous one. I could understand if there is a little bit of overhead needed to manage the changes but this growth behavior seems weird to me. Can anybody explain this phenomenon or correct my assumptions that lead to the wrong expectations?

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  • .net real time stream processing - needed huge and fast RAM buffer

    - by mack369
    The application I'm developing communicates with an digital audio device, which is capable of sending 24 different voice streams at the same time. The device is connected via USB, using FTDI device (serial port emulator) and D2XX Drivers (basic COM driver is to slow to handle transfer of 4.5Mbit). Basically the application consist of 3 threads: Main thread - GUI, control, ect. Bus reader - in this thread data is continuously read from the device and saved to a file buffer (there is no logic in this thread) Data interpreter - this thread reads the data from file buffer, converts to samples, does simple sample processing and saves the samples to separate wav files. The reason why I used file buffer is that I wanted to be sure that I won't loose any samples. The application doesn't use recording all the time, so I've chosen this solution because it was safe. The application works fine, except that buffered wave file generator is pretty slow. For 24 parallel records of 1 minute, it takes about 4 minutes to complete the recording. I'm pretty sure that eliminating the use of hard drive in this process will increase the speed much. The second problem is that the file buffer is really heavy for long records and I can't clean this up until the end of data processing (it would slow down the process even more). For RAM buffer I need at lest 1GB to make it work properly. What is the best way to allocate such a big amount of memory in .NET? I'm going to use this memory in 2 threads so a fast synchronization mechanism needed. I'm thinking about a cycle buffer: one big array, the Bus Reader saves the data, the Data Interpreter reads it. What do you think about it? [edit] Now for buffering I'm using classes BinaryReader and BinaryWriter based on a file.

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  • Looking for a fast, compact, streamable, multi-language, strongly typed serialization format

    - by sanity
    I'm currently using JSON (compressed via gzip) in my Java project, in which I need to store a large number of objects (hundreds of millions) on disk. I have one JSON object per line, and disallow linebreaks within the JSON object. This way I can stream the data off disk line-by-line without having to read the entire file at once. It turns out that parsing the JSON code (using http://www.json.org/java/) is a bigger overhead than either pulling the raw data off disk, or decompressing it (which I do on the fly). Ideally what I'd like is a strongly-typed serialization format, where I can specify "this object field is a list of strings" (for example), and because the system knows what to expect, it can deserialize it quickly. I can also specify the format just by giving someone else its "type". It would also need to be cross-platform. I use Java, but work with people using PHP, Python, and other languages. So, to recap, it should be: Strongly typed Streamable (ie. read a file bit by bit without having to load it all into RAM at once) Cross platform (including Java and PHP) Fast Free (as in speech) Any pointers?

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  • Perl's Devel::LeakTrace::Fast Pointing to blank files and evals

    - by kt
    I am using Devel::LeakTrace::Fast to debug a memory leak in a perl script designed as a daemon which runs an infinite loop with sleeps until interrupted. I am having some trouble both reading the output and finding documentation to help me understand the output. The perldoc doesn't contain much information on the output. Most of it makes sense, such as pointing to globals in DBI. Intermingled with the output, however, are several leaked SV(<LOCATION>) from (eval #) line # Where the numbers are numbers and <LOCATION> is a location in memory. The script itself is not using eval at any point - I have not investigated each used module to see if evals are present. Mostly what I want to know is how to find these evals (if possible). I also find the following entries repeated over and over again leaked SV(<LOCATION>) from line # Where line # is always the same #. Not very helpful in tracking down what file that line is in.

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  • Fast way to manually mod a number

    - by Nikolai Mushegian
    I need to be able to calculate (a^b) % c for very large values of a and b (which individually are pushing limit and which cause overflow errors when you try to calculate a^b). For small enough numbers, using the identity (a^b)%c = (a%c)^b%c works, but if c is too large this doesn't really help. I wrote a loop to do the mod operation manually, one a at a time: private static long no_Overflow_Mod(ulong num_base, ulong num_exponent, ulong mod) { long answer = 1; for (int x = 0; x < num_exponent; x++) { answer = (answer * num_base) % mod; } return answer; } but this takes a very long time. Is there any simple and fast way to do this operation without actually having to take a to the power of b AND without using time-consuming loops? If all else fails, I can make a bool array to represent a huge data type and figure out how to do this with bitwise operators, but there has to be a better way.

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  • C# / Silverlight / WPF / Fast rendering lots of circles

    - by Walt W
    I want to render a lot of circles or small graphics within either silverlight or wpf (around 1000-10000) as fast and as frequently as possible. If I have to go to DX or OGL, that's fine, but I'm wondering about doing this within either of those two frameworks first (read: it's OK if an answer is WPF-only or Silverlight-only). Also, if there is a way to access DX through WPF and render on a surface that way, I would be interested in that as well. So, what's the fastest way to draw a load of circles? They can be as plain as necessary, but they do need to have a radius. Currently I'm using DrawingVisual and a DrawingContext.DrawEllipse() command for each circle, then rendering the visual to a RenderTargetBItmap, but it becomes very slow as the number of circles rises. By the way, these circles move every frame, so caching isn't really an option unless you're going to suggest caching the individual circles . . . But their sizes are dynamic, so I'm not sure that's a great approach.

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  • Way to store a large dictionary with low memory footprint + fast lookups (on Android)

    - by BobbyJim
    I'm developing an android word game app that needs a large (~250,000 word dictionary) available. I need: reasonably fast look ups e.g. constant time preferable, need to do maybe 200 lookups a second on occasion to solve a word puzzle and maybe 20 lookups within 0.2 second more often to check words the user just spelled. EDIT: Lookups are typically asking "Is in the dictionary?". I'd like to support up to two wildcards in the word as well, but this is easy enough by just generating all possible letters the wildcards could have been and checking the generated words (i.e. 26 * 26 lookups for a word with two wildcards). as it's a mobile app, using as little memory as possible and requiring only a small initial download for the dictionary data is top priority. My first naive attempts used Java's HashMap class, which caused an out of memory exception. I've looked into using the SQL lite databases available on android, but this seems like overkill. What's a good way to do what I need?

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  • Apache mod_rewrite - forward domain root to subdirectory

    - by DuFace
    I have what I originally assumed to be a simple problem. I am using shared hosting for my website (so I don't have access to the Apache configuration) and have only been given a single folder to store all my content in. This is all well and good but it means that all my subdomains must have their virtual document root's inside public_html, meaning they effectively become a folder on my main domain. What I'd like to do is organise my public_html something like this: public_html/ www/ index.php ... sub1/ index.php ... some_library/ ... This way, all my web content is still in public_html but only a small fraction of it will be served to the client. I can easily achieve this for all the subdomains, but it's the primary domain that I'm having issues with. I created a .htaccess file in public_html with the following: Options +SymLinksIfOwnerMatch # I'm not allowed to use FollowSymLinks RewriteEngine on RewriteBase / RewriteCond %{REQUEST_URI} !^/www [NC] RewriteRule ^(.*)$ /www/$1 [L] This works fairly well, but for some strange reason www.example.com/stuff is translated into a request for www.example.com/www/stuff and hence a 404 error is given. It was my understanding that unless an 'R' flag was specified, mod_rewrite was purely internal so I can't understand why the request is generated as that implies (to me at least) redirection. I assumed this would be a trivial problem to solve as all I actually want to do is forward all requests for the root of www.example.com to a subdirectory, but I've spent hours searching for answers and none are quite correct. I find it difficult to believe I'm the only person to have this issue. I apologise if this question has been answered on here before, I did search and trawl but couldn't find an appropriate answer. Please could someone shed some light on this?

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  • Fast find object by string property

    - by Andrew Kalashnikov
    Hello, colleagues. I've got task to fast find object by its string property. Object: class DicDomain { public virtual string Id{ get; set; } public virtual string Name { get; set; } } For storing my object I use List[T] dictionary where T is DicDomain for now . I've got 5-10 such lists, which contain about 500-20000 at each one. Task is find objects by its Name. I use next code now: List<T> entities = dictionary.FindAll(s => s.Name.Equals(word, StringComparison.OrdinalIgnoreCase)); I've got some questions: Is my search speed optimal. I think now. Data structure. It List good for this task. What about hashtable,sorted... Method Find. May be i should use string intern?? I haven't much exp at these tasks. Can u give me good advice for increase perfomance. Thanks

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  • I need a fast runtime expression parser

    - by Chris Lively
    I need to locate a fast, lightweight expression parser. Ideally I want to pass it a list of name/value pairs (e.g. variables) and a string containing the expression to evaluate. All I need back from it is a true/false value. The types of expressions should be along the lines of: varA == "xyz" and varB==123 Basically, just a simple logic engine whose expression is provided at runtime. UPDATE At minimum it needs to support ==, !=, , =, <, <= Regarding speed, I expect roughly 5 expressions to be executed per request. We'll see somewhere in the vicinity of 100/requests a second. Our current pages tend to execute in under 50ms. Usually there will only be 2 or 3 variables involved in any expression. However, I'll need to load approximately 30 into the parser prior to execution. UPDATE 2012/11/5 Update about performance. We implemented nCalc nearly 2 years ago. Since then we've expanded it's use such that we average 40+ expressions covering 300+ variables on post backs. There are now thousands of post backs occurring per second with absolutely zero performance degradation. We've also extended it to include a handful of additional functions, again with no performance loss. In short, nCalc met all of our needs and exceeded our expectations.

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  • IIS 6.0 Rewrite rules for Wordpress (Forward slash not working and other things)

    - by DigitalBlade
    Hi, I am using Wordpress 3.0.4 on IIS 6.0 and Windows Server 2003, hosted by a company. I was having lots of issues using permalinks. I have fixed most, but now I have an issue with a forward-slash not being added to the address. This would be fine on most websites, but not on IIS for some reason. Specifically, if I go to "mysite.com/wp-admin" I can log-in and get to the dashboard, but as soon as I click anything there i am redirected to a broken link. For example: "mysite.com/post-new.php". If I add the slash at the end it's fine. So I tried to have a rewrite rule to automatically add the slash to such address: RewriteRule /wp-admin /wp-admin/ [L] But it still doesn't work. For your reference, here's the complete file: [ISAPI_Rewrite] RewriteBase / RewriteCond ${REQUEST_FILENAME} !-f RewriteCond ${REQUEST_FILENAME} !-d # For special WordPress folders (e.g. theme, admin, etc.) RewriteRule /wp-admin /wp-admin/ [L] RewriteRule /wp-(.*) /wp-$1 [L] RewriteRule /(.*\.(?:jpg|jpeg|gif|css|txt|xml|html|png|js)) /$1 [I,L] # Rules to ensure that normal content gets through RewriteRule /images/(.*) /images/$1 [L] RewriteRule /favicon.ico /favicon.ico [L] RewriteRule /robots.txt /robots.txt [L] RewriteRule /phpmyadmin/(.*) /phpmyadmin/$1 [L] RewriteRule /phpmyadmin /phpmyadmin/ [L] # For all WordPress pages RewriteRule ^/$ /index.php [L] RewriteRule /(.*) /index.php/$1 [L] Any ideas? Thanks in advance

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  • Very fast document similarity

    - by peyton
    Hello, I am trying to determine document similarity between a single document and each of a large number of documents (n ~= 1 million) as quickly as possible. More specifically, the documents I'm comparing are e-mails; they are grouped (i.e., there are folders or tags) and I'd like to determine which group is most appropriate for a new e-mail. Fast performance is critical. My a priori assumption is that the cosine similarity between term vectors is appropriate for this application; please comment on whether this is a good measure to use or not! I have already taken into account the following possibilities for speeding up performance: Pre-normalize all the term vectors Calculate a term vector for each group (n ~= 10,000) rather than each e-mail (n ~= 1,000,000); this would probably be acceptable for my application, but if you can think of a reason not to do it, let me know! I have a few questions: If a new e-mail has a new term never before seen in any of the previous e-mails, does that mean I need to re-compute all of my term vectors? This seems expensive. Is there some clever way to only consider vectors which are likely to be close to the query document? Is there some way to be more frugal about the amount of memory I'm using for all these vectors? Thanks!

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  • Fast serialization/deserialization of structs

    - by user256890
    I have huge amont of geographic data represented in simple object structure consisting only structs. All of my fields are of value type. public struct Child { readonly float X; readonly float Y; readonly int myField; } public struct Parent { readonly int id; readonly int field1; readonly int field2; readonly Child[] children; } The data is chunked up nicely to small portions of Parent[]-s. Each array contains a few thousands Parent instances. I have way too much data to keep all in memory, so I need to swap these chunks to disk back and forth. (One file would result approx. 2-300KB). What would be the most efficient way of serializing/deserializing the Parent[] to a byte[] for dumpint to disk and reading back? Concerning speed, I am particularly interested in fast deserialization, write speed is not that critical. Would simple BinarySerializer good enough? Or should I hack around with StructLayout (see accepted answer)? I am not sure if that would work with array field of Parent.children. UPDATE: Response to comments - Yes, the objects are immutable (code updated) and indeed the children field is not value type. 300KB sounds not much but I have zillions of files like that, so speed does matter.

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  • C code Error: free(): invalid next size (fast):

    - by user1436057
    I got an error from my code, but I'm not sure where to fix it. Here's the explanation of what my code does: I'm writing some code that will read an input file and store each line as an object (char type) in an array. The first line of the input file is a number. This number tells me how many lines that I should read and store in the array. Here's my code: int main(int argc, char *argv[]){ FILE *fp; char **path; int num, i; ... /*after reading the first line and store the number value in num*/ path = malloc(num *sizeof(char)); i=0; while (!feof(fp)) { char buffer[500]; int length = 0; for (ch = fgetc(fp); ch != EOF && ch != '\n'; ch = fgetc(fp)) { buffer[length++] = ch; } if(ch == '\n' && ch!= EOF){ buffer[length] = '\0'; path[i] = malloc(strlen(buffer)+1); strcpy(path[i], buffer); i++; } } ... free(path); } After running the code, I get this *** glibc detected *** free(): invalid next size (fast): I have searched around and know this is malloc/free error, but I don't exactly know to fix it. Any help would be great. Thanks!

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  • accessing google maps via UIWebView - illegal?

    - by Karin
    New to iPhone development. Working on first app. I'm accessing google maps via UIWebView to forward geocode an address using "http://maps.google.com/maps?q=my address". It works, although it has this quirk of requiring you to hit "Back" button and then the "Detail" button (provided by the navigation bar) to get back to the screen from whence you started. If anyone knows why it does this, I'd love to hear. My real question, however, is this a legal use of google maps? Since I intend this app for commercial use, am I violating Google's rules + regs? If it is illegal, what's my alternative? Thanks.

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  • C++ method declaration, class definition problem

    - by John Fra.
    I have 2 classes: A and B. Some methods of class A need to use class B and the opposite(class B has methods that need to use class A). So I have: class A; class B { method1(A a) { } } class A { method1(B b) { } void foo() { } } and everything works fine. But when I try to call foo() of class A from B::method1 like this: class B { method1(A a) { a.foo(); } } I get as result compile errors of forward declaration and use of incomplete type. But why is this happening? (I have declared class A before using it?)

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