Search Results

Search found 4838 results on 194 pages for 'binary heap'.

Page 38/194 | < Previous Page | 34 35 36 37 38 39 40 41 42 43 44 45  | Next Page >

• How to create real-life robots?

  - by Click Upvote

  Even before I learnt programming I've been fascinated with how robots could work. Now I know how the underlying programming instructions would be written, but what I don't understand is how those intructions are followed by the robot. For example, if I wrote this code: object=Robot.ScanSurroundings(300,400); if (Objects.isEatable(object)) { Robot.moveLeftArm(300,400); Robot.pickObject(object); } How would this program be followed by the CPU in a way that would make the robot do the physical action of looking to the left, moving his arm, and such? Is it done primarily in binary language/ASM? Lastly, where would i go if I wanted to learn how to create a robot?

  Read the article

• Building Boost with LSB C++ Compiler

  - by Alex Farber

  I want to build my program with LSB C++ Compiler from the Linux Standard Base http://www.linuxfoundation.org/collaborate/workgroups/lsb. Program depends on the Boost library, built with gcc 4.4 version. Compilation fails. Is it possible to build the Boost library with LSB C++ Compiler? Alternatively, is it possible to build the Boost library with some old gcc version, what version is recommended? My final goal is to get my executable and third-party Boost libraries running on most Linux distributions. Generally, what can be done to get better binary compatibility for Linux distributions, developing C++ closed-source application depending on the Boost library?

  Read the article

• Python: Unpack arbitary length bits for database storage

  - by sberry2A

  I have a binary data format consisting of 18,000+ packed int64s, ints, shorts, bytes and chars. The data is packed to minimize it's size, so they don't always use byte sized chunks. For example, a number whose min and max value are 31, 32 respectively might be stored with a single bit where the actual value is bitvalue + min, so 0 is 31 and 1 is 32. I am looking for the most efficient way to unpack all of these for subsequent processing and database storage. Right now I am able to read any value by using either struct.unpack, or BitBuffer. I use struct.unpack for any data that starts on a bit where (bit-offset % 8 == 0 and data-length % 8 == 0) and I use BitBuffer for anything else. I know the offset and size of every packed piece of data, so what is going to be the fasted way to completely unpack them? Many thanks.

  Read the article

• Trying to figure out how to check a checksum

  - by rross

  I'm trying to figure out how to check a checksum. My message looks like this: 38 0A 01 12 78 96 FE 00 F0 FB D0 FE F6 F6 being the checksum. I convert the preceding 12 sets in to binary and then add them together. Then attempt a bitwise operation to apply the 2s complement. I get a value of -1562, but I can't convert it back to hex to check if the value is correct. Can someone point me in the right direction? my code: string[] hexValue = {"38", "0A", "01", "12", "78", "96", "FE", "00", "F0", "FB", "D0", "FE"}; int totalValue = 0; foreach(string item in hexValue) { totalValue += Int32.Parse(item, NumberStyles.HexNumber); } int bAfter2sC = ~totalValue + 1; Console.Write("answer :" + bAfter2sC + "\n");

  Read the article

• C# Convert negative int to 11 bits

  - by Klemenko

  I need to convert numbers in interval [–1024, 1016]. I'm converting to 11 bits like that: string s = Convert.ToString(value, 2); //Convert to binary in a string int[] bits = s.PadLeft(11, '0') // Add 0's from left .Select(c => int.Parse(c.ToString())) // convert each char to int .ToArray(); // Convert IEnumerable from select to Array This works perfectly for signed integers [0, 1016]. But for negative integers I get 32 bits result. Do you have any idea how to convert negative integers to 11 bits array?

  Read the article

• Why is TreeSet<T> an internal type in .NET?

  - by Justin Niessner

  So, I was just digging around Reflector trying to find the implementation details of HashSet (out of sheer curiosity based on the answer to another question here) and noticed the following: internal class TreeSet<T> : ICollection<T>, IEnumerable<T>, ICollection, IEnumerable, ISerializable, IDeserializationCallback Without looking too deep into the details, it looks like a Self-Balancing Binary Search Tree. My question is, is there anybody out there with the insight as to why this class is internal? Is it simply because the other collection types use it internally and hide the complexities of a BST from the general masses...or am I way off base?

  Read the article

• What's a good algorithm for searching arrays N and M, in order to find elements in N that also exist

  - by GenTiradentes

  I have two arrays, N and M. they are both arbitrarily sized, though N is usually smaller than M. I want to find out what elements in N also exist in M, in the fastest way possible. To give you an example of one possible instance of the program, N is an array 12 units in size, and M is an array 1,000 units in size. I want to find which elements in N also exist in M. (There may not be any matches.) The more parallel the solution, the better. I used to use a hash map for this, but it's not quite as efficient as I'd like it to be. Typing this out, I just thought of running a binary search of M on sizeof(N) independent threads. (Using CUDA) I'll see how this works, though other suggestions are welcome.

  Read the article

• Tree + Recursion..

  - by RBA

  Hi.. I came across an article on Binary Trees Search . It uses intensive Recursive Algorithms.. I am just so confused with these stuff.. Please guide my path so as I understand these problems at ease, or any good website to read about recursion first and then solving these problems.. Please share your experience on it.. Its very urgent, and I want to learn these concepts as soon as possible.. Thankss... Regards.

  Read the article

• VB.NET encoding one character wrong

  - by Nick Spiers

  I have a byte array that I'm encoding to a string: Private Function GetKey() As String Dim ba() As Byte = {&H47, &H43, &H44, &H53, &H79, &H73, &H74, &H65, &H6D, &H73, &H89, &HA, &H1, &H32, &H31, &H36} Dim strReturn As String = Encoding.ASCII.GetString(ba) Return strReturn End Function Then I write that to a file via IO.File.AppendAllText. If I open that file in 010 Editor (to view the binary data) it displays as this: 47 43 44 53 79 73 74 65 6D 73 3F 0A 01 32 31 36 The original byte array contained 89 at position 11, and the encoded string contains 3F. If I change my encoding to Encoding.Default.GetString, it gives me: 47 43 44 53 79 73 74 65 6D 73 E2 80 B0 0A 01 32 31 36 Any help would be much appreciated!

  Read the article

• Dictionary not deserializing

  - by Shadow

  I'm having a problem where one Dictionary in my project is either not serializing or not deserializing. After deserializing, the data I serialized is simply not in the object. Here's the relevant snip of the class being serialized: class Person : ISerializable { private Dictionary<Relation,List<int>> Relationships = new Dictionary<Relation,List<int>>(); public Person(SerializationInfo info, StreamingContext context) { this.Relationships = (Dictionary<Relation, List<int>>) info.GetValue("Relationships", typeof(Dictionary<Relation, List<int>>)); } public void GetObjectData(SerializationInfo info, StreamingContext context) { info.AddValue("Relationships", this.Relationships); } } Note, this is binary serialization. Everything else in the project serializes and deserialzes correctly.

  Read the article

• Q on Python serialization/deserialization

  - by neil

  What chances do I have to instantiate, keep and serialize/deserialize to/from binary data Python classes reflecting this pattern (adopted from RFC 2246 [TLS]): enum { apple, orange } VariantTag; struct { uint16 number; opaque string<0..10>; /* variable length */ } V1; struct { uint32 number; opaque string[10]; /* fixed length */ } V2; struct { select (VariantTag) { /* value of selector is implicit */ case apple: V1; /* VariantBody, tag = apple */ case orange: V2; /* VariantBody, tag = orange */ } variant_body; /* optional label on variant */ } VariantRecord; Basically I would have to define a (variant) class VariantRecord, which varies depending on the value of VariantTag. That's not that difficult. The challenge is to find a most generic way to build a class, which serializes/deserializes to and from a byte stream... Pickle, Google protocol buffer, marshal is all not an option. I made little success with having an explicit "def serialize" in my class, but I'm not very happy with it, because it's not generic enough. I hope I could express the problem. My current solution in case VariantTag = apple would look like this, but I don't like it too much import binascii import struct class VariantRecord(object): def __init__(self, number, opaque): self.number = number self.opaque = opaque def serialize(self): out = struct.pack('>HB%ds' % len(self.opaque), self.number, len(self.opaque), self.opaque) return out v = VariantRecord(10, 'Hello') print binascii.hexlify(v.serialize()) >> 000a0548656c6c6f Regards

  Read the article

• Returning recursive ternary freaks out

  - by David Titarenco

  Hi, assume this following function: int binaryTree::findHeight(node *n) { if (n == NULL) { return 0; } else { return 1 + max(findHeight(n->left), findHeight(n->right)); } } Pretty standard recursive treeHeight function for a given binary search tree binaryTree. Now, I was helping a friend (he's taking an algorithms course), and I ran into some weird issue with this function that I couldn't 100% explain to him. With max being defined as max(a,b) ((a)>(b)?(a):(b)) (which happens to be the max definition in windef.h), the recursive function freaks out (it runs something like n^n times where n is the tree height). This obviously makes checking the height of a tree with 3000 elements take very, very long. However, if max is defined via templating, like std does it, everything is okay. So using std::max fixed his problem. I just want to know why. Also, why does the countLeaves function work fine, using the same programmatic recursion? int binaryTree::countLeaves(node *n) { if (n == NULL) { return 0; } else if (n->left == NULL && n->right == NULL) { return 1; } else { return countLeaves(n->left) + countLeaves(n->right); } } Is it because in returning the ternary function, the values a => countLeaves(n->left) and b => countLeaves(n->right) were recursively double called simply because they were the resultants? Thank you!

  Read the article

• Why can't the 'NonSerialized' attribute be used at the class level? How to prevent serialization of

  - by ck

  I have a data object that is deep-cloned using a binary serialization. This data object supports property changed events, for example, PriceChanged. Let's say I attached a handler to PriceChanged. When the code attempts to serialize PriceChanged, it throws an exception that the handler isn't marked as serializable. My alternatives: I can't easily remove all handlers from the event before serialization I don't want to mark the handler as serializable because I'd have to recursively mark all the handlers dependencies as well. I don't want to mark PriceChanged as NonSerialized - there are tens of events like this that could potentially have handlers. Ideally, I'd like .NET to just stop going down the object graph at that point and make that a 'leaf'. So why can't I just mark the handler class as 'NonSerialized'? -- I finally worked around this problem by making the handler implement ISerializable and doing nothing in the serialize constructor/ GetDataObject method. But, the handler still is serialized, just with all its dependencies set to null - so I had to account for that as well. Is there a better way to prevent serialization of an entire class?

  Read the article

• Log 2 N generic comparison tree

  - by Morano88

  Hey! I'm working on an algorithm for Redundant Binary Representation (RBR) where every two bits represent a digit. I designed the comparator that takes 4 bits and gives out 2 bits. I want to make the comparison in log 2 n so If I have X and Y .. I compare every 2 bits of X with every 2 bits of Y. This is smooth if the number of bits of X or Y equals n where (n = 2^X) i.e n = 2,4,8,16,32,... etc. Like this : However, If my input let us say is 6 or 10 .. then it becomes not smooth and I have to take into account some odd situations like this : I have a shallow experience in algorithms .. is there a generic way to do it .. so at the end I get only 2 bits no matter what the input is ? I just need hints or pseudo-code. If my question is not appropriate here .. so feel free to flag it or tell me to remove it. I'm using VHDL by the way!

  Read the article

• Count bits used in int

  - by sigvardsen

  If you have the binary number 10110 how can I get it to return 5? e.g a number that tells how many bits are used? There are some likewise examples listed below: 101 should return 3 000000011 should return 2 11100 should return 5 101010101 should return 9 How can this be obtained the easiest way in Java? I have come up with the following method but can i be done faster: public static int getBitLength(int value) { int l = 1; if (value >> 16 > 0) { value = value >> 16; l += 16; } if (value >> 8 > 0) { value = value >> 8; l += 8; } if (value >> 4 > 0) { value = value >> 4; l += 4; } if (value >> 2 > 0) { value = value >> 2; l += 2; } if (value >> 1 > 0) { value = value >> 1; l += 1; } return l; }

  Read the article

• problem with binarysearch algorithm

  - by arash

  hi friends,the code below belongs to binary search algorithm,user enter numbers in textbox1 and enter the number that he want to fing with binarysearch in textbox2.i have a problem with it,that is when i enter for example 15,21 in textbox1 and enter 15 in textbox2 and put brakpoint on the line i commented below,and i understood that it doesnt put the number in textbox2 in searchnums(commented),for more explanation i comment in code.thanks in advance public void button1_Click(object sender, EventArgs e) { int searchnums = Convert.ToInt32(textBox2.Text);//the problem is here,the value in textbox2 doesnt exist in searchnums and it has value 0. int result = binarysearch(searchnums); MessageBox.Show(result.ToString()); } public int binarysearch(int searchnum) { string[] source = textBox1.Text.Split(','); int[] nums = new int[source.Length]; for (int i = 0; i < source.Length; i++) { nums[i] = Convert.ToInt32(source[i]); } int first =0; int last = nums.Length; int mid = (int)Math.Floor(nums.Length / 2.0); while (1<= nums.Length) { if (searchnum < nums[mid]) { last = mid - 1; } if (searchnum > nums[mid]) { first = mid + 1; } else { return nums[mid]; } } return -1; }

  Read the article

• Extract history from Korn shell

  - by Luc

  I am not happy about the history file in binary format of the Korn shell. I like to "collect" some of my command lines, many of them actually, and for a long time. I'm talking about years. That doesn't seem easy in Korn because the history file is not plain text so I can't edit it, and a lot of junk is piling up in it. By "junk" I mean lines that I don'twant to keep, like 'cat' or 'man'. So I added these lines to my .profile: fc -ln 1 9999 ~/khistory.txt source ~/loghistory.sh ~/khistory.txt loghistory.sh contains a handful of sed and sort commands that gets rid of a lot of the junk. But apparently it is forbidden to run fc in the .profile file. I can't login whenever I do, the shell exits right away with signal 11. So I removed that 'fc -l' line from my .profile file and added it to the loghistory.sh script, but the shell still crashes. I also tried this line in my .profile: strings ~/.sh_history ~/khistory.txt source ~/loghistory.sh That doesn't crash, but the output is printed with an additional, random character in the beginning of many lines. I can run 'fc -l' on the command line, but that's no good. I need to automate that. But how? How can I extract my ksh history as plain text? TIA

  Read the article

• Detection of negative integers using bit operations

  - by Nawaz

  One approach to check if a given integer is negative or not, could be this: (using bit operations) int num_bits = sizeof(int) * 8; //assuming 8 bits per byte! int sign_bit = given_int & (1 << (num_bits-1)); //sign_bit is either 1 or 0 if ( sign_bit ) { cout << "given integer is negative"<<endl; } else { cout << "given integer is positive"<<endl; } The problem with this solution is that number of bits per byte couldn't be 8, it could be 9,10, 11 even 16 or 40 bits per byte. Byte doesn't necessarily mean 8 bits! Anyway, this problem can be easily fixed by writing, //CHAR_BIT is defined in limits.h int num_bits = sizeof(int) * CHAR_BIT; //no assumption. It seems fine now. But is it really? Is this Standard conformant? What if the negative integer is not represented as 2's complement? What if it's representation in a binary numeration system that doesn't necessitate only negative integers to have 1 in it's most significant bit? Can we write such code that will be both portable and standard conformant? Related topics: Size of Primitive data types Why is a boolean 1 byte and not 1 bit of size?

  Read the article

• Algorithm for assigning a unique series of bits for each user?

  - by Mark

  The problem seems simple at first: just assign an id and represent that in binary. The issue arises because the user is capable of changing as many 0 bits to a 1 bit. To clarify, the hash could go from 0011 to 0111 or 1111 but never 1010. Each bit has an equal chance of being changed and is independent of other changes. What would you have to store in order to go from hash - user assuming a low percentage of bit tampering by the user? I also assume failure in some cases so the correct solution should have an acceptable error rate. I would an estimate the maximum number of bits tampered with would be about 30% of the total set. I guess the acceptable error rate would depend on the number of hashes needed and the number of bits being set per hash. I'm worried with enough manipulation the id can not be reconstructed from the hash. The question I am asking I guess is what safe guards or unique positioning systems can I use to ensure this happens.

  Read the article

• In-order tree traversal

  - by Chris S

  I have the following text from an academic course I took a while ago about in-order traversal (they also call it pancaking) of a binary tree (not BST): In-order tree traversal Draw a line around the outside of the tree. Start to the left of the root, and go around the outside of the tree, to end up to the right of the root. Stay as close to the tree as possible, but do not cross the tree. (Think of the tree — its branches and nodes — as a solid barrier.) The order of the nodes is the order in which this line passes underneath them. If you are unsure as to when you go “underneath” a node, remember that a node “to the left” always comes first. Here's the example used (slightly different tree from below) However when I do a search on google, I get a conflicting definition. For example the wikipedia example: Inorder traversal sequence: A, B, C, D, E, F, G, H, I (leftchild,rootnode,right node) But according to (my understanding of) definition #1, this should be A, B, D, C, E, F, G, I, H Can anyone clarify which definition is correct? They might be both describing different traversal methods, but happen to be using the same name. I'm having trouble believing the peer-reviewed academic text is wrong, but can't be certain.

  Read the article

• Tree iterator, can you optimize this any further?

  - by Ron

  As a follow up to my original question about a small piece of this code I decided to ask a follow up to see if you can do better then what we came up with so far. The code below iterates over a binary tree (left/right = child/next ). I do believe there is room for one less conditional in here (the down boolean). The fastest answer wins! The cnt statement can be multiple statements so lets make sure this appears only once The child() and next() member functions are about 30x as slow as the hasChild() and hasNext() operations. Keep it iterative <-- dropped this requirement as the recursive solution presented was faster. This is C++ code visit order of the nodes must stay as they are in the example below. ( hit parents first then the children then the 'next' nodes). BaseNodePtr is a boost::shared_ptr as thus assignments are slow, avoid any temporary BaseNodePtr variables. Currently this code takes 5897ms to visit 62200000 nodes in a test tree, calling this function 200,000 times. void processTree (BaseNodePtr current, unsigned int & cnt ) { bool down = true; while ( true ) { if ( down ) { while (true) { cnt++; // this can/will be multiple statesments if (!current->hasChild()) break; current = current->child(); } } if ( current->hasNext() ) { down = true; current = current->next(); } else { down = false; current = current->parent(); if (!current) return; // done. } } }

  Read the article

• What is wrong with this code for reading binary files? [on hold]

  - by qed

  What is wrong with this code for reading binary files? It compiles OK, but will not print out the file as planned, in fact, it prints nothing at all. #include <iostream> #include <fstream> int main(int argc, const char *argv[]) { if (argc < 2) { ::std::cerr << "usage: " << argv[0] << " <filename>\n"; return 1; } ::std::basic_ifstream<unsigned char> in(argv[1], ::std::ios::binary); unsigned char uc; while (in.get(uc)) { printf("%02X ", uc); } // TODO: error handling, in case the file could not be opened or read return 0; }

  Read the article

• Neo4j OutOfMemory problem

  - by Edward83

  Hi! This is my source code of Main.java. It was grabbed from neo4j-apoc-1.0 examples. The goal of modification to store 1M records of 2 nodes and 1 relation: package javaapplication2; import org.neo4j.graphdb.GraphDatabaseService; import org.neo4j.graphdb.Node; import org.neo4j.graphdb.RelationshipType; import org.neo4j.graphdb.Transaction; import org.neo4j.kernel.EmbeddedGraphDatabase; public class Main { private static final String DB_PATH = "neo4j-store-1M"; private static final String NAME_KEY = "name"; private static enum ExampleRelationshipTypes implements RelationshipType { EXAMPLE } public static void main(String[] args) { GraphDatabaseService graphDb = null; try { System.out.println( "Init database..." ); graphDb = new EmbeddedGraphDatabase( DB_PATH ); registerShutdownHook( graphDb ); System.out.println( "Start of creating database..." ); int valIndex = 0; for(int i=0; i<1000; ++i) { for(int j=0; j<1000; ++j) { Transaction tx = graphDb.beginTx(); try { Node firstNode = graphDb.createNode(); firstNode.setProperty( NAME_KEY, "Hello" + valIndex ); Node secondNode = graphDb.createNode(); secondNode.setProperty( NAME_KEY, "World" + valIndex ); firstNode.createRelationshipTo( secondNode, ExampleRelationshipTypes.EXAMPLE ); tx.success(); ++valIndex; } finally { tx.finish(); } } } System.out.println("Ok, client processing finished!"); } finally { System.out.println( "Shutting down database ..." ); graphDb.shutdown(); } } private static void registerShutdownHook( final GraphDatabaseService graphDb ) { // Registers a shutdown hook for the Neo4j instance so that it // shuts down nicely when the VM exits (even if you "Ctrl-C" the // running example before it's completed) Runtime.getRuntime().addShutdownHook( new Thread() { @Override public void run() { graphDb.shutdown(); } } ); } } After a few iterations (around 150K) I got error message: "java.lang.OutOfMemoryError: Java heap space at java.nio.HeapByteBuffer.(HeapByteBuffer.java:39) at java.nio.ByteBuffer.allocate(ByteBuffer.java:312) at org.neo4j.kernel.impl.nioneo.store.PlainPersistenceWindow.(PlainPersistenceWindow.java:30) at org.neo4j.kernel.impl.nioneo.store.PersistenceWindowPool.allocateNewWindow(PersistenceWindowPool.java:534) at org.neo4j.kernel.impl.nioneo.store.PersistenceWindowPool.refreshBricks(PersistenceWindowPool.java:430) at org.neo4j.kernel.impl.nioneo.store.PersistenceWindowPool.acquire(PersistenceWindowPool.java:122) at org.neo4j.kernel.impl.nioneo.store.CommonAbstractStore.acquireWindow(CommonAbstractStore.java:459) at org.neo4j.kernel.impl.nioneo.store.AbstractDynamicStore.updateRecord(AbstractDynamicStore.java:240) at org.neo4j.kernel.impl.nioneo.store.PropertyStore.updateRecord(PropertyStore.java:209) at org.neo4j.kernel.impl.nioneo.xa.Command$PropertyCommand.execute(Command.java:513) at org.neo4j.kernel.impl.nioneo.xa.NeoTransaction.doCommit(NeoTransaction.java:443) at org.neo4j.kernel.impl.transaction.xaframework.XaTransaction.commit(XaTransaction.java:316) at org.neo4j.kernel.impl.transaction.xaframework.XaResourceManager.commit(XaResourceManager.java:399) at org.neo4j.kernel.impl.transaction.xaframework.XaResourceHelpImpl.commit(XaResourceHelpImpl.java:64) at org.neo4j.kernel.impl.transaction.TransactionImpl.doCommit(TransactionImpl.java:514) at org.neo4j.kernel.impl.transaction.TxManager.commit(TxManager.java:571) at org.neo4j.kernel.impl.transaction.TxManager.commit(TxManager.java:543) at org.neo4j.kernel.impl.transaction.TransactionImpl.commit(TransactionImpl.java:102) at org.neo4j.kernel.EmbeddedGraphDbImpl$TransactionImpl.finish(EmbeddedGraphDbImpl.java:329) at javaapplication2.Main.main(Main.java:62) 28.05.2010 9:52:14 org.neo4j.kernel.impl.nioneo.store.PersistenceWindowPool logWarn WARNING: [neo4j-store-1M\neostore.propertystore.db.strings] Unable to allocate direct buffer" Guys! Help me plzzz, what I did wrong, how can I repair it? Tested on platform Windows XP 32bit SP3. Maybe solution within creation custom configuration? thnx 4 every advice!

  Read the article

• Can I set Java max heap size for running from a jar file?

  - by Kip

  I am launching a java jar file which often requires more than the default 64MB max heap size. A 256MB heap size is sufficient for this app though. Is there anyway to specify (in the manifest maybe?) to always use a 256MB max heap size when launching the jar? (More specific details below, if needed.) This is a command-line app that I've written in Java, which does some image manipulation. On high-res images (about 12 megapixels and above, which is not uncommon) I get an OutOfMemoryError. Currently I'm launching the app from a jar file, i.e. java -jar MyApp.jar params... I can avoid an OutOfMemoryError by specifying 256MB max heap size on the command line, i.e.: java -Xmx256m -jar MyApp.jar params... However, I don't want to have to specify this, since I know that 256MB is sufficient even for high-res images. I'd like to have that information saved in the jar file. Is that possible?

  Read the article

• Designing a database file format

  - by RoliSoft

  I would like to design my own database engine for educational purposes, for the time being. Designing a binary file format is not hard nor the question, I've done it in the past, but while designing a database file format, I have come across a very important question: How to handle the deletion of an item? So far, I've thought of the following two options: Each item will have a "deleted" bit which is set to 1 upon deletion. Pro: relatively fast. Con: potentially sensitive data will remain in the file. 0x00 out the whole item upon deletion. Pro: potentially sensitive data will be removed from the file. Con: relatively slow. Recreating the whole database. Pro: no empty blocks which makes the follow-up question void. Con: it's a really good idea to overwrite the whole 4 GB database file because a user corrected a typo. I will sell this method to Twitter ASAP! Now let's say you already have a few empty blocks in your database (deleted items). The follow-up question is how to handle the insertion of a new item? Append the item to the end of the file. Pro: fastest possible. Con: file will get huge because of all the empty blocks that remain because deleted items aren't actually deleted. Search for an empty block exactly the size of the one you're inserting. Pro: may get rid of some blocks. Con: you may end up scanning the whole file at each insert only to find out it's very unlikely to come across a perfectly fitting empty block. Find the first empty block which is equal or larger than the item you're inserting. Pro: you probably won't end up scanning the whole file, as you will find an empty block somewhere mid-way; this will keep the file size relatively low. Con: there will still be lots of leftover 0x00 bytes at the end of items which were inserted into bigger empty blocks than they are. Rigth now, I think the first deletion method and the last insertion method are probably the "best" mix, but they would still have their own small issues. Alternatively, the first insertion method and scheduled full database recreation. (Probably not a good idea when working with really large databases. Also, each small update in that method will clone the whole item to the end of the file, thus accelerating file growth at a potentially insane rate.) Unless there is a way of deleting/inserting blocks from/to the middle of the file in a file-system approved way, what's the best way to do this? More importantly, how do databases currently used in production usually handle this?

  Read the article

< Previous Page | 34 35 36 37 38 39 40 41 42 43 44 45  | Next Page >