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  • Write a JavaScript that accepts a number from the user using the “prompt” function

    - by A sw A
    Write a JavaScript that accepts a number from the user using the “prompt” function. Then it draws a table in the HTML document that has the user specified number of rows and columns. In each table data, it displays the result of the math operation (row raised to the power of column). For example, if the user enters the number 3, the JavaScript should draw the following table: 1 1 1 2 4 8 3 9 27

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  • Good Form for Random Number Generator?

    - by JackCJR
    I wanted to get a few opinions on doing a random number generator. I read through a couple different ways to do it and this is the way that I created after doing a little reading. Is it acceptable form? Any foreseeable issues? function master(){ function generate(){ var pickFrom= "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"; var j = pickFrom.length; var i = Math.floor(Math.random()*j+1); //Generates a random number var code = pickFrom.charAt(i) //Picks a number based on what number was picked. document.write(code) } x = 1; while(x){ generate(); x--; } } master();

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  • "Possible SYN flooding" in log despite low number of SYN_RECV connections

    - by al4
    Recently we had an apache server which was responding very slowly due to SYN flooding. The workaround for this was to enable tcp_syncookies (net.ipv4.tcp_syncookies=1 in /etc/sysctl.conf). I posted a question about this here if you want more background. After enabling syncookies we started seeing the following message in /var/log/messages approximately every 60 seconds: [84440.731929] possible SYN flooding on port 80. Sending cookies. Vinko Vrsalovic informed me that this means the syn backlog is getting full, so I raised tcp_max_syn_backlog to 4096. At some point I also lowered tcp_synack_retries to 3 (down from the default of 5) by issuing sysctl -w net.ipv4.tcp_synack_retries=3. After doing this, the frequency seemed to drop, with the interval of the messages varying between roughly 60 and 180 seconds. Next I issued sysctl -w net.ipv4.tcp_max_syn_backlog=65536, but am still getting the message in the log. Throughout all this I've been watching the number of connections in SYN_RECV state (by running watch --interval=5 'netstat -tuna |grep "SYN_RECV"|wc -l'), and it never goes higher than about 240, much much lower than the size of the backlog. Yet I have a Red Hat server which hovers around 512 (limit on this server is the default of 1024). Are there any other tcp settings which would limit the size of the backlog or am I barking up the wrong tree? Should the number of SYN_RECV connections in netstat -tuna correlate to the size of the backlog? Update As best I can tell I'm dealing with legitimate connections here, netstat -tuna|wc -l hovers around 5000. I've been researching this today and found this post from a last.fm employee, which has been rather useful. I've also discovered that the tcp_max_syn_backlog has no effect when syncookies are enabled (as per this link) So as a next step I set the following in sysctl.conf: net.ipv4.tcp_syn_retries = 3 # default=5 net.ipv4.tcp_synack_retries = 3 # default=5 net.ipv4.tcp_max_syn_backlog = 65536 # default=1024 net.core.wmem_max = 8388608 # default=124928 net.core.rmem_max = 8388608 # default=131071 net.core.somaxconn = 512 # default = 128 net.core.optmem_max = 81920 # default = 20480 I then setup my response time test, ran sysctl -p and disabled syncookies by sysctl -w net.ipv4.tcp_syncookies=0. After doing this the number of connections in the SYN_RECV state still remained around 220-250, but connections were starting to delay again. Once I noticed these delays I re-enabled syncookies and the delays stopped. I believe what I was seeing was still an improvement from the initial state, however some requests were still delayed which is much worse than having syncookies enabled. So it looks like I'm stuck with them enabled until we can get some more servers online to cope with the load. Even then, I'm not sure I see a valid reason to disable them again as they're only sent (apparently) when the server's buffers get full. But the syn backlog doesn't appear to be full with only ~250 connections in the SYN_RECV state! Is it possible that the SYN flooding message is a red herring and it's something other than the syn_backlog that's filling up? If anyone has any other tuning options I haven't tried yet I'd be more than happy to try them out, but I'm starting to wonder if the syn_backlog setting isn't being applied properly for some reason.

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  • C++ question on prime numbers.

    - by user278330
    Hello. I am trying to make a program that determines if the number is prime or composite. I have gotten thus far. Could you give me any ideas so that it will work? All primes will , however, because composites have values that are both r0 and r==0, they will always be classified as prime. How can I fix this? int main() { int pNumber, limit, x, r; limit = 0; x = 2; cout << "Please enter any positive integer: " ; cin >> pNumber; if (pNumber < 0) { cout << "Invalid. Negative Number. " << endl; return 0; } else if (pNumber == 0) { cout << "Invalid. Zero has an infinite number of divisors, and therefore neither composite nor prime." << endl; return 0; } else if (pNumber == 1) { cout << "Valid. However, one is neither prime nor composite" << endl; return 0; } else { while (limit < pNumber) { r = pNumber % x; x++; limit++; } if (r == 0) cout << "Your number is composite" << endl; else cout << "Your number is prime" << endl; } return 0; }

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  • C++ question on prime numbers.

    - by user278330
    Hello. I am trying to make a program that determines if the number is prime or composite. I have gotten thus far. Could you give me any ideas so that it will work? All primes will , however, because composites have values that are both r0 and r==0, they will always be classified as prime. How can I fix this? int main() { int pNumber, limit, x, r; limit = 0; x = 2; cout << "Please enter any positive integer: " ; cin >> pNumber; if (pNumber < 0) { cout << "Invalid. Negative Number. " << endl; return 0; } else if (pNumber == 0) { cout << "Invalid. Zero has an infinite number of divisors, and therefore neither composite nor prime." << endl; return 0; } else if (pNumber == 1) { cout << "Valid. However, one is neither prime nor composite" << endl; return 0; } else { while (limit < pNumber) { r = pNumber % x; x++; limit++; } if (r == 0) cout << "Your number is composite" << endl; else cout << "Your number is prime" << endl; } return 0; }

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  • MS Access Premiere Products Exercise

    - by rynwtts
    I am working with Microsoft Access, Premiere Products Exercises for a college course. I can't seem to get past a specific question. We are working with DBDL and E-R Diagrams. The question is here. Indicate the changes you need to make to the design of the Premiere Products database to support the following situation. A customer is not necessarily represented by a single sales rep but can be represented by several sales reps. when a customer places an order, the sales rep who gets the commission on the order must be one of the collection of sales reps who represents the customer. In the database already each customer is represented by a sales rep. Which yields a one to one relationship. I need to enable a customer to have several sales reps, and make it so that only those sales rep will be eligible for commission upon each order.

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  • Sun Solaris - Find out number of processors and cores

    - by Adrian
    Our SPARC server is running Sun Solaris 10; I would like to find out the actual number of processors and the number of cores for each processor. The output of psrinfo and prtdiag is ambiguous: $psrinfo -v Status of virtual processor 0 as of: dd/mm/yyyy hh:mm:ss on-line since dd/mm/yyyy hh:mm:ss. The sparcv9 processor operates at 1592 MHz, and has a sparcv9 floating point processor. Status of virtual processor 1 as of: dd/mm/yyyy hh:mm:ss on-line since dd/mm/yyyy hh:mm:ss. The sparcv9 processor operates at 1592 MHz, and has a sparcv9 floating point processor. Status of virtual processor 2 as of: dd/mm/yyyy hh:mm:ss on-line since dd/mm/yyyy hh:mm:ss. The sparcv9 processor operates at 1592 MHz, and has a sparcv9 floating point processor. Status of virtual processor 3 as of: dd/mm/yyyy hh:mm:ss on-line since dd/mm/yyyy hh:mm:ss. The sparcv9 processor operates at 1592 MHz, and has a sparcv9 floating point processor. _ $prtdiag -v System Configuration: Sun Microsystems sun4u Sun Fire V445 System clock frequency: 199 MHZ Memory size: 32GB ==================================== CPUs ==================================== E$ CPU CPU CPU Freq Size Implementation Mask Status Location --- -------- ---------- --------------------- ----- ------ -------- 0 1592 MHz 1MB SUNW,UltraSPARC-IIIi 3.4 on-line MB/C0/P0 1 1592 MHz 1MB SUNW,UltraSPARC-IIIi 3.4 on-line MB/C1/P0 2 1592 MHz 1MB SUNW,UltraSPARC-IIIi 3.4 on-line MB/C2/P0 3 1592 MHz 1MB SUNW,UltraSPARC-IIIi 3.4 on-line MB/C3/P0 _ $more /etc/release Solaris 10 8/07 s10s_u4wos_12b SPARC Copyright 2007 Sun Microsystems, Inc. All Rights Reserved. Use is subject to license terms. Assembled 16 August 2007 Patch Cluster - EIS 29/01/08(v3.1.5) What other methods can I use? EDITED: It looks like we have a 4 processor system with one core each: $psrinfo -p 4 _ $psrinfo -pv The physical processor has 1 virtual processor (0) UltraSPARC-IIIi (portid 0 impl 0x16 ver 0x34 clock 1592 MHz) The physical processor has 1 virtual processor (1) UltraSPARC-IIIi (portid 1 impl 0x16 ver 0x34 clock 1592 MHz) The physical processor has 1 virtual processor (2) UltraSPARC-IIIi (portid 2 impl 0x16 ver 0x34 clock 1592 MHz) The physical processor has 1 virtual processor (3) UltraSPARC-IIIi (portid 3 impl 0x16 ver 0x34 clock 1592 MHz)

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  • Why is a FLAC encoded from a decoded MP3 bigger than the MP3?

    - by Ryan Thompson
    To be more precise than in the title, suppose I have a MP3 file that is 320 kbps. If I decompress it, then logically, all the data except for roughly 320 kilobits out of each second of audio should be redundant data, able to be compressed away. So, when I encode the decompressed file to FLAC, or any other lossless codec, why is it so much larger? On a related note, is it theoretically possible to losslessly recover the source mp3 audio from a decompressed wav? (I know the mp3 itself is lossy. I'm asking if it's possible to re-encode without any further loss.) EDIT: Let me clarify the related question, and the rationale behind it. Suppose I have a wav that was decompressed from an MP3 file (and assume I don't have the mp3 itself for some reason). If I don't want to lose any more quality, I can re-encode it with FLAC or any other lossless encoder and get a larger file just to maintain the same quality. Or, I can re-encode it to mp3 again and get the same size as the original but lose more data. Obviously, neither of these cases is ideal. I can either have the original size or the original quality, but not both (I mean the quality of the original mp3, not the original lossless source). My question is: Can we get both? Is it theoretically possible to recover the lossy compressed data from the lossy decompressed data, without losing even more? If it is possible, I could imagine a lossless compression algorithm that compresses the audio with FLAC. Then it also scans the audio for any signs of previous lossy compression, and if detected, recompresses it losslessly to the original lossy file. Then it keeps whichever file is smaller.

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  • another "SSH connect to host github.com port 22: Bad file number"

    - by Mariusz
    Hello. I have a problem with my first-time ssh connection. Yes, I've already done yours guides, already tried your "Dealing with firewalls and proxies" article and the problem is still occuring. I am using Win7 32bit, Windows Firewall is disabled, haven't any third-party firewalls, ESET Nod32 Antivirus is not blocking any ports, I am not using any PROXY (neither local proxy) . Here goes the logs: Ordinary SSH connection try C:\Users\Mariusz>ssh -vvv [email protected] OpenSSH_4.6p1, OpenSSL 0.9.8e 23 Feb 2007 debug2: ssh_connect: needpriv 0 debug1: Connecting to github.com [207.97.227.239] port 22. debug1: connect to address 207.97.227.239 port 22: Not owner ssh: connect to host github.com port 22: Bad file number NCAT connection try C:\Users\Mariusz>ncat github.com 22 Strange connect error from 207.97.227.239 (10013): No error 10013 = WSAEACCES I think that method called "smart-http-support" won't be usable for me because I haven't created repo yet. I have just GIT INIT locally, and finished at step GIT PUSH, which returns the same: ssh: connect to host github.com port 22: Bad file number fatal: The remote end hung up unexpectedly corkscrew method (first article from yours guide) . While PUTTYing (with pageant in bg), after inputing login - an error is occuring (MessageBox): Disconnected: No supported authentication methods available And in terminal such message is printing out: Server refused our key Key I have generated correctly, using ssh-keygen. I tried not method by editing ~/.ssh/config yet because I had thought that because I haven't PUSHed anything to my remote repo so I won't be able to CLONE anything. Method called ssh-forwarding is not for my, cause it "requires access to an external ssh server" and I haven't any at this time. What else could I do? Thanks in advance for any help. Mariusz.

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  • dhcpd pool exhaustion - What's the result?

    - by jarmund
    I have a DHCP server that serves leases to several houndred, maybe up to a thousand, different clients on an average day. The pool consists of 242 IPs, and due to the highly dynamic nature of the network, it's enough 99% of the time (most devices are gone from the network in a few minutes), despite having a lease time of 3600. Now, imagine if more clients than that connect to the network during an hour. The sollution is obvious: Decrease lease time, or increase the DHCP pool, however, what i would like to know: What happens when dhcpd has exhausted the pool? Are new DHCP requests simply ignored?

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  • What if a computer with Ethernet

    - by George Nixon
    I'm just revising for an exam on Networks and Data Communications, and there's one thing I don't get about CSMA/CD and Ethernet. It's supposed to be fairly stable, for instance if a computer drops out of the network, it's not a problem like it might be in a token ring network (I think). But Ethernet works by all the other computers waiting for the currently transmitting computer to finish what it's doing, and then the others use CMSA/CD to determine who goes next. What if one computer malfunctioned and kept sending a continuous stream of data in an infinite loop? In fact, is there a standard time for pcs to transmit before they yield to others?

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  • Small maximum number of connections on a Linux router

    - by Eugene
    I have a Linux box acting as a router with no iptables or other firewall and no networking applications running on it, just pure router. I've put it in a test environment that generates many TCP connections, each having unique source and destination IP, and those connections go through this router. I'm observing that number of connections successfully created rise to approximately 500 and then no more connections can be created for several minutes, then another 100 connections can be created and there is another pause, and so on. If 10 connections for each source-destination pair are created, then maximum numbers go about 10 times up, so the problem is probably with many connections from different IPs. As traffic is simply routed, it doesn't have to do with number of file descriptors, iptables connection tracking and other things often proposed to check in similar cases. The box has plenty of free RAM and CPU, both NICs are gigabit. The kernel is 2.6.32. I've already tried increasing net.core.*mem_max, net.core.netdev_max_backlog and txqueuelen on both NICs, with completely no effect. What else should I check ? Is there some rate-limit in the kernel itself ?

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  • file read performance degrades as number of files increases

    - by bfallik-bamboom
    We're observing poor file read IO results that we'd like to better understand. We can use fio to write 100 files with a sustained aggregate throughput of ~700MB/s. When we switch the test to read instead of write, the aggregate throughput is only ~55MB/s. The drop seems related to the number of files since the throughput for read and write are comparable for a single file then diverge proportionally as we increase the number of files. The test server has 24 CPU cores, 48GB of memory, and is running CentOS 6.0. The disk hardware is a RAID 6 array with 12 disks and a Dell H800 controller. This device is partitioned with ext4 using the default settings. Increasing the readahead (using blockdev) improves the read throughput significantly but it still doesn't match write speed. For instance, increasing the readahead from 128KB to 1M improved the read throughput to ~145MB/s. Is this a known performance issue in our OS/disk/filesystem configuration? If so, how can we tell? If not, what tools or tests can we use to further isolate the issue? Thanks.

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  • How can I check cells for number series?

    - by Stephen Younger
    I have a bit of a problem evaluating an excel cell. Example: M M M M M M M M M 1 2 3 4 5 6 7 8 9 2;5;7 1;9 3;5;7;9 I have a number of excel cells which contain numbers (months). In the first column I have a series of numbers. I want to use conditional formatting to color the corresponding cells in the right columns. If correctly colored I would get something like this: M M M M M M M M M 1 2 3 4 5 6 7 8 9 2;5;7 X X X 1;9 X X 3;5;7;9 X X X X The formula I have now is this: IF(ISNUMBER(FIND(L$22;$K23));$H23;"") but the problem is that cells are colored too which contain part of a number. If I enter 10;15 as input I get this: M M M M M M M M M M M M M M M 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 10;15 X X X X because 1 and 5 are found too. I only want column 10 and 15 to be marked. How can I change the formula or the input?

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  • mysqld - master to slave replication using rsync innodb, sequence number issues

    - by Luis
    I've read several of the related topics posted here, but I have not been able to avoid this innodb error. The steps I've taken to replicate data from a Slackware server - 5.5.27-log (S) to a FreeBSD slave - 5.5.21-log (F) were these: (S) flush tables with read lock; (S) in another terminal show master status; (S) stop mysqld via command line in third terminal; (F) while both servers are stopped, rsync mysql datadir from (S), excluding master.info, mysql-bin and relay-* files; (F) start mysqld (skip-slave) 121018 12:03:29 InnoDB: Error: page 7 log sequence number 456388912904 InnoDB: is in the future! Current system log sequence number 453905468629. InnoDB: Your database may be corrupt or you may have copied the InnoDB InnoDB: tablespace but not the InnoDB log files. See InnoDB: http://dev.mysql.com/doc/refman/5.5/en/forcing-innodb-recovery.html InnoDB: for more information. This kind of error happens for a lot of tables. I know I can use dump, but the database is large, ca. 70GB and the systems are slow (old), so would like to get this replication to work with data transfer. What should I try to solve this issue?

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  • Copy past speed very slow for a large number of files on Windows [closed]

    - by Arno2501
    I've run the following test I've created a folder containing 15'000 files of 400 bytes using this batch : @ECHO off SET times=15000 FOR /L %%i IN (1,1,%times%) DO ( fsutil file createnew filename%%i.txt 400 ) then I copy past it on my Windows Computer using this command : robocopy LargeNumberOfFiles\ LargeNumberOfFiles2\ After it has completed I can see that the transfer rate was 915810 Bytes/sec this is less than 1 MB/s. It took me several seconds to copy 7 MBytes Please note that this is very slow. I've tried the same with a folder with a single file of 50 Mbytes and the transfer rate is 1219512195 Bytes/sec. (yeah GB/s) instantaneous. Why copying large number of files take so much time - ressources on a windows filesystem ? Please note that I've tried to do the same on a linux system which runs on the same computer in a virtual machine (vmware player) with ext3 filesystem. I use the cp command and the copy is instantaneous ! Please also note the following : no antivirus I've tested that behaviour on multiple windows computers (always ntfs) i always get comparable results (transfer rate under 1MB/s avg 7-8 seconds to copy 7 MBytes) I've tested on multiple linux ext3 system the copy is always instantaneous for that amount (15000 files of 400 bytes) The question is about understanding what makes windows filesystem so slow to copy large number of files compared to a linux one for instance.

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  • computing "node closure" of graph with removal

    - by Fakrudeen
    Given a directed graph, the goal is to combine the node with the nodes it is pointing to and come up with minimum number of these [lets give the name] super nodes. The catch is once you combine the nodes you can't use those nodes again. [first node as well as all the combined nodes - that is all the members of one super node] The greedy approach would be to pick the node with maximum out degree and combine that node with nodes it is pointing to and remove all of them. Do this every time with the nodes which are not removed yet from graph. The greedy is O(V), but this won't necessarily output minimum number super nodes. So what is the best algorithm to do this?

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  • how to use 3D map Actionscript class in mxml file for display map.

    - by nemade-vipin
    hello friends, I have created the application in which I have to use 3D map Action Script class in mxml file to display a map in form. that is in tab navigator last tab. My ActionScript 3D map class is(FlyingDirections):- package src.SBTSCoreObject { import src.SBTSCoreObject.JSONDecoder; import com.google.maps.InfoWindowOptions; import com.google.maps.LatLng; import com.google.maps.LatLngBounds; import com.google.maps.Map3D; import com.google.maps.MapEvent; import com.google.maps.MapOptions; import com.google.maps.MapType; import com.google.maps.MapUtil; import com.google.maps.View; import com.google.maps.controls.NavigationControl; import com.google.maps.geom.Attitude; import com.google.maps.interfaces.IPolyline; import com.google.maps.overlays.Marker; import com.google.maps.overlays.MarkerOptions; import com.google.maps.services.Directions; import com.google.maps.services.DirectionsEvent; import com.google.maps.services.Route; import flash.display.Bitmap; import flash.display.DisplayObject; import flash.display.DisplayObjectContainer; import flash.display.Loader; import flash.display.LoaderInfo; import flash.display.Sprite; import flash.events.Event; import flash.events.IOErrorEvent; import flash.events.MouseEvent; import flash.events.TimerEvent; import flash.filters.DropShadowFilter; import flash.geom.Point; import flash.net.URLLoader; import flash.net.URLRequest; import flash.net.navigateToURL; import flash.text.TextField; import flash.text.TextFieldAutoSize; import flash.text.TextFormat; import flash.utils.Timer; import flash.utils.getTimer; public class FlyingDirections extends Map3D { /** * Panoramio home page. */ private static const PANORAMIO_HOME:String = "http://www.panoramio.com/"; /** * The icon for the car. */ [Embed("assets/car-icon-24px.png")] private static const Car:Class; /** * The Panoramio icon. */ [Embed("assets/iw_panoramio.png")] private static const PanoramioIcon:Class; /** * We animate a zoom in to the start the route before the car starts * to move. This constant sets the time in seconds over which this * zoom occurs. */ private static const LEAD_IN_DURATION:Number = 3; /** * Duration of the trip in seconds. */ private static const TRIP_DURATION:Number = 40; /** * Constants that define the geometry of the Panoramio image markers. */ private static const BORDER_T:Number = 3; private static const BORDER_L:Number = 10; private static const BORDER_R:Number = 10; private static const BORDER_B:Number = 3; private static const GAP_T:Number = 2; private static const GAP_B:Number = 1; private static const IMAGE_SCALE:Number = 1; /** * Trajectory that the camera follows over time. Each element is an object * containing properties used to generate parameter values for flyTo(..). * fraction = 0 corresponds to the start of the trip; fraction = 1 * correspondsto the end of the trip. */ private var FLY_TRAJECTORY:Array = [ { fraction: 0, zoom: 6, attitude: new Attitude(0, 0, 0) }, { fraction: 0.2, zoom: 8.5, attitude: new Attitude(30, 30, 0) }, { fraction: 0.5, zoom: 9, attitude: new Attitude(30, 40, 0) }, { fraction: 1, zoom: 8, attitude: new Attitude(50, 50, 0) }, { fraction: 1.1, zoom: 8, attitude: new Attitude(130, 50, 0) }, { fraction: 1.2, zoom: 8, attitude: new Attitude(220, 50, 0) }, ]; /** * Number of panaramio photos for which we load data. We&apos;ll select a * subset of these approximately evenly spaced along the route. */ private static const NUM_GEOTAGGED_PHOTOS:int = 50; /** * Number of panaramio photos that we actually show. */ private static const NUM_SHOWN_PHOTOS:int = 7; /** * Scaling between real trip time and animation time. */ private static const SCALE_TIME:Number = 0.001; /** * getTimer() value at the instant that we start the trip. If this is 0 then * we have not yet started the car moving. */ private var startTimer:int = 0; /** * The current route. */ private var route:Route; /** * The polyline for the route. */ private var polyline:IPolyline; /** * The car marker. */ private var marker:Marker; /** * The cumulative duration in seconds over each step in the route. * cumulativeStepDuration[0] is 0; cumulativeStepDuration[1] adds the * duration of step 0; cumulativeStepDuration[2] adds the duration * of step 1; etc. */ private var cumulativeStepDuration:/*Number*/Array = []; /** * The cumulative distance in metres over each vertex in the route polyline. * cumulativeVertexDistance[0] is 0; cumulativeVertexDistance[1] adds the * distance to vertex 1; cumulativeVertexDistance[2] adds the distance to * vertex 2; etc. */ private var cumulativeVertexDistance:Array; /** * Array of photos loaded from Panoramio. This array has the same format as * the &apos;photos&apos; property within the JSON returned by the Panoramio API * (see http://www.panoramio.com/api/), with additional properties added to * individual photo elements to hold the loader structures that fetch * the actual images. */ private var photos:Array = []; /** * Array of polyline vertices, where each element is in world coordinates. * Several computations can be faster if we can use world coordinates * instead of LatLng coordinates. */ private var worldPoly:/*Point*/Array; /** * Whether the start button has been pressed. */ private var startButtonPressed:Boolean = false; /** * Saved event from onDirectionsSuccess call. */ private var directionsSuccessEvent:DirectionsEvent = null; /** * Start button. */ private var startButton:Sprite; /** * Alpha value used for the Panoramio image markers. */ private var markerAlpha:Number = 0; /** * Index of the current driving direction step. Used to update the * info window content each time we progress to a new step. */ private var currentStepIndex:int = -1; /** * The fly directions map constructor. * * @constructor */ public function FlyingDirections() { key="ABQIAAAA7QUChpcnvnmXxsjC7s1fCxQGj0PqsCtxKvarsoS-iqLdqZSKfxTd7Xf-2rEc_PC9o8IsJde80Wnj4g"; super(); addEventListener(MapEvent.MAP_PREINITIALIZE, onMapPreinitialize); addEventListener(MapEvent.MAP_READY, onMapReady); } /** * Handles map preintialize. Initializes the map center and zoom level. * * @param event The map event. */ private function onMapPreinitialize(event:MapEvent):void { setInitOptions(new MapOptions({ center: new LatLng(-26.1, 135.1), zoom: 4, viewMode: View.VIEWMODE_PERSPECTIVE, mapType:MapType.PHYSICAL_MAP_TYPE })); } /** * Handles map ready and looks up directions. * * @param event The map event. */ private function onMapReady(event:MapEvent):void { enableScrollWheelZoom(); enableContinuousZoom(); addControl(new NavigationControl()); // The driving animation will be updated on every frame. addEventListener(Event.ENTER_FRAME, enterFrame); addStartButton(); // We start the directions loading now, so that we&apos;re ready to go when // the user hits the start button. var directions:Directions = new Directions(); directions.addEventListener( DirectionsEvent.DIRECTIONS_SUCCESS, onDirectionsSuccess); directions.addEventListener( DirectionsEvent.DIRECTIONS_FAILURE, onDirectionsFailure); directions.load("48 Pirrama Rd, Pyrmont, NSW to Byron Bay, NSW"); } /** * Adds a big blue start button. */ private function addStartButton():void { startButton = new Sprite(); startButton.buttonMode = true; startButton.addEventListener(MouseEvent.CLICK, onStartClick); startButton.graphics.beginFill(0x1871ce); startButton.graphics.drawRoundRect(0, 0, 150, 100, 10, 10); startButton.graphics.endFill(); var startField:TextField = new TextField(); startField.autoSize = TextFieldAutoSize.LEFT; startField.defaultTextFormat = new TextFormat("_sans", 20, 0xffffff, true); startField.text = "Start!"; startButton.addChild(startField); startField.x = 0.5 * (startButton.width - startField.width); startField.y = 0.5 * (startButton.height - startField.height); startButton.filters = [ new DropShadowFilter() ]; var container:DisplayObjectContainer = getDisplayObject() as DisplayObjectContainer; container.addChild(startButton); startButton.x = 0.5 * (container.width - startButton.width); startButton.y = 0.5 * (container.height - startButton.height); var panoField:TextField = new TextField(); panoField.autoSize = TextFieldAutoSize.LEFT; panoField.defaultTextFormat = new TextFormat("_sans", 11, 0x000000, true); panoField.text = "Photos provided by Panoramio are under the copyright of their owners."; container.addChild(panoField); panoField.x = container.width - panoField.width - 5; panoField.y = 5; } /** * Handles directions success. Starts flying the route if everything * is ready. * * @param event The directions event. */ private function onDirectionsSuccess(event:DirectionsEvent):void { directionsSuccessEvent = event; flyRouteIfReady(); } /** * Handles click on the start button. Starts flying the route if everything * is ready. */ private function onStartClick(event:MouseEvent):void { startButton.removeEventListener(MouseEvent.CLICK, onStartClick); var container:DisplayObjectContainer = getDisplayObject() as DisplayObjectContainer; container.removeChild(startButton); startButtonPressed = true; flyRouteIfReady(); } /** * If we have loaded the directions and the start button has been pressed * start flying the directions route. */ private function flyRouteIfReady():void { if (!directionsSuccessEvent || !startButtonPressed) { return; } var directions:Directions = directionsSuccessEvent.directions; // Extract the route. route = directions.getRoute(0); // Draws the polyline showing the route. polyline = directions.createPolyline(); addOverlay(directions.createPolyline()); // Creates a car marker that is moved along the route. var car:DisplayObject = new Car(); marker = new Marker(route.startGeocode.point, new MarkerOptions({ icon: car, iconOffset: new Point(-car.width / 2, -car.height) })); addOverlay(marker); transformPolyToWorld(); createCumulativeArrays(); // Load Panoramio data for the region covered by the route. loadPanoramioData(directions.bounds); var duration:Number = route.duration; // Start a timer that will trigger the car moving after the lead in time. var leadInTimer:Timer = new Timer(LEAD_IN_DURATION * 1000, 1); leadInTimer.addEventListener(TimerEvent.TIMER, onLeadInDone); leadInTimer.start(); var flyTime:Number = -LEAD_IN_DURATION; // Set up the camera flight trajectory. for each (var flyStep:Object in FLY_TRAJECTORY) { var time:Number = flyStep.fraction * duration; var center:LatLng = latLngAt(time); var scaledTime:Number = time * SCALE_TIME; var zoom:Number = flyStep.zoom; var attitude:Attitude = flyStep.attitude; var elapsed:Number = scaledTime - flyTime; flyTime = scaledTime; flyTo(center, zoom, attitude, elapsed); } } /** * Loads Panoramio data for the route bounds. We load data about more photos * than we need, then select a subset lying along the route. * @param bounds Bounds within which to fetch images. */ private function loadPanoramioData(bounds:LatLngBounds):void { var params:Object = { order: "popularity", set: "full", from: "0", to: NUM_GEOTAGGED_PHOTOS.toString(10), size: "small", minx: bounds.getWest(), miny: bounds.getSouth(), maxx: bounds.getEast(), maxy: bounds.getNorth() }; var loader:URLLoader = new URLLoader(); var request:URLRequest = new URLRequest( "http://www.panoramio.com/map/get_panoramas.php?" + paramsToString(params)); loader.addEventListener(Event.COMPLETE, onPanoramioDataLoaded); loader.addEventListener(IOErrorEvent.IO_ERROR, onPanoramioDataFailed); loader.load(request); } /** * Transforms the route polyline to world coordinates. */ private function transformPolyToWorld():void { var numVertices:int = polyline.getVertexCount(); worldPoly = new Array(numVertices); for (var i:int = 0; i < numVertices; ++i) { var vertex:LatLng = polyline.getVertex(i); worldPoly[i] = fromLatLngToPoint(vertex, 0); } } /** * Returns the time at which the route approaches closest to the * given point. * @param world Point in world coordinates. * @return Route time at which the closest approach occurs. */ private function getTimeOfClosestApproach(world:Point):Number { var minDistSqr:Number = Number.MAX_VALUE; var numVertices:int = worldPoly.length; var x:Number = world.x; var y:Number = world.y; var minVertex:int = 0; for (var i:int = 0; i < numVertices; ++i) { var dx:Number = worldPoly[i].x - x; var dy:Number = worldPoly[i].y - y; var distSqr:Number = dx * dx + dy * dy; if (distSqr < minDistSqr) { minDistSqr = distSqr; minVertex = i; } } return cumulativeVertexDistance[minVertex]; } /** * Returns the array index of the first element that compares greater than * the given value. * @param ordered Ordered array of elements. * @param value Value to use for comparison. * @return Array index of the first element that compares greater than * the given value. */ private function upperBound(ordered:Array, value:Number, first:int=0, last:int=-1):int { if (last < 0) { last = ordered.length; } var count:int = last - first; var index:int; while (count > 0) { var step:int = count >> 1; index = first + step; if (value >= ordered[index]) { first = index + 1; count -= step - 1; } else { count = step; } } return first; } /** * Selects up to a given number of photos approximately evenly spaced along * the route. * @param ordered Array of photos, each of which is an object with * a property &apos;closestTime&apos;. * @param number Number of photos to select. */ private function selectEvenlySpacedPhotos(ordered:Array, number:int):Array { var start:Number = cumulativeVertexDistance[0]; var end:Number = cumulativeVertexDistance[cumulativeVertexDistance.length - 2]; var closestTimes:Array = []; for each (var photo:Object in ordered) { closestTimes.push(photo.closestTime); } var selectedPhotos:Array = []; for (var i:int = 0; i < number; ++i) { var idealTime:Number = start + ((end - start) * (i + 0.5) / number); var index:int = upperBound(closestTimes, idealTime); if (index < 1) { index = 0; } else if (index >= ordered.length) { index = ordered.length - 1; } else { var errorToPrev:Number = Math.abs(idealTime - closestTimes[index - 1]); var errorToNext:Number = Math.abs(idealTime - closestTimes[index]); if (errorToPrev < errorToNext) { --index; } } selectedPhotos.push(ordered[index]); } return selectedPhotos; } /** * Handles completion of loading the Panoramio index data. Selects from the * returned photo indices a subset of those that lie along the route and * initiates load of each of these. * @param event Load completion event. */ private function onPanoramioDataLoaded(event:Event):void { var loader:URLLoader = event.target as URLLoader; var decoder:JSONDecoder = new JSONDecoder(loader.data as String); var allPhotos:Array = decoder.getValue().photos; for each (var photo:Object in allPhotos) { var latLng:LatLng = new LatLng(photo.latitude, photo.longitude); photo.closestTime = getTimeOfClosestApproach(fromLatLngToPoint(latLng, 0)); } allPhotos.sortOn("closestTime", Array.NUMERIC); photos = selectEvenlySpacedPhotos(allPhotos, NUM_SHOWN_PHOTOS); for each (photo in photos) { var photoLoader:Loader = new Loader(); // The images aren&apos;t on panoramio.com: we can&apos;t acquire pixel access // using "new LoaderContext(true)". photoLoader.load( new URLRequest(photo.photo_file_url)); photo.loader = photoLoader; // Save the loader info: we use this to find the original element when // the load completes. photo.loaderInfo = photoLoader.contentLoaderInfo; photoLoader.contentLoaderInfo.addEventListener( Event.COMPLETE, onPhotoLoaded); } } /** * Creates a MouseEvent listener function that will navigate to the given * URL in a new window. * @param url URL to which to navigate. */ private function createOnClickUrlOpener(url:String):Function { return function(event:MouseEvent):void { navigateToURL(new URLRequest(url)); }; } /** * Handles completion of loading an individual Panoramio image. * Adds a custom marker that displays the image. Initially this is made * invisible so that it can be faded in as needed. * @param event Load completion event. */ private function onPhotoLoaded(event:Event):void { var loaderInfo:LoaderInfo = event.target as LoaderInfo; // We need to find which photo element this image corresponds to. for each (var photo:Object in photos) { if (loaderInfo == photo.loaderInfo) { var imageMarker:Sprite = createImageMarker(photo.loader, photo.owner_name, photo.owner_url); var options:MarkerOptions = new MarkerOptions({ icon: imageMarker, hasShadow: true, iconAlignment: MarkerOptions.ALIGN_BOTTOM | MarkerOptions.ALIGN_LEFT }); var latLng:LatLng = new LatLng(photo.latitude, photo.longitude); var marker:Marker = new Marker(latLng, options); photo.marker = marker; addOverlay(marker); // A hack: we add the actual image after the overlay has been added, // which creates the shadow, so that the shadow is valid even if we // don&apos;t have security privileges to generate the shadow from the // image. marker.foreground.visible = false; marker.shadow.alpha = 0; var imageHolder:Sprite = new Sprite(); imageHolder.addChild(photo.loader); imageHolder.buttonMode = true; imageHolder.addEventListener( MouseEvent.CLICK, createOnClickUrlOpener(photo.photo_url)); imageMarker.addChild(imageHolder); return; } } trace("An image was loaded which could not be found in the photo array."); } /** * Creates a custom marker showing an image. */ private function createImageMarker(child:DisplayObject, ownerName:String, ownerUrl:String):Sprite { var content:Sprite = new Sprite(); var panoramioIcon:Bitmap = new PanoramioIcon(); var iconHolder:Sprite = new Sprite(); iconHolder.addChild(panoramioIcon); iconHolder.buttonMode = true; iconHolder.addEventListener(MouseEvent.CLICK, onPanoramioIconClick); panoramioIcon.x = BORDER_L; panoramioIcon.y = BORDER_T; content.addChild(iconHolder); // NOTE: we add the image as a child only after we&apos;ve added the marker // to the map. Currently the API requires this if it&apos;s to generate the // shadow for unprivileged content. // Shrink the image, so that it doesn&apos;t obcure too much screen space. // Ideally, we&apos;d subsample, but we don&apos;t have pixel level access. child.scaleX = IMAGE_SCALE; child.scaleY = IMAGE_SCALE; var imageW:Number = child.width; var imageH:Number = child.height; child.x = BORDER_L + 30; child.y = BORDER_T + iconHolder.height + GAP_T; var authorField:TextField = new TextField(); authorField.autoSize = TextFieldAutoSize.LEFT; authorField.defaultTextFormat = new TextFormat("_sans", 12); authorField.text = "author:"; content.addChild(authorField); authorField.x = BORDER_L; authorField.y = BORDER_T + iconHolder.height + GAP_T + imageH + GAP_B; var ownerField:TextField = new TextField(); ownerField.autoSize = TextFieldAutoSize.LEFT; var textFormat:TextFormat = new TextFormat("_sans", 14, 0x0e5f9a); ownerField.defaultTextFormat = textFormat; ownerField.htmlText = "<a href=\"" + ownerUrl + "\" target=\"_blank\">" + ownerName + "</a>"; content.addChild(ownerField); ownerField.x = BORDER_L + authorField.width; ownerField.y = BORDER_T + iconHolder.height + GAP_T + imageH + GAP_B; var totalW:Number = BORDER_L + Math.max(imageW, ownerField.width + authorField.width) + BORDER_R; var totalH:Number = BORDER_T + iconHolder.height + GAP_T + imageH + GAP_B + ownerField.height + BORDER_B; content.graphics.beginFill(0xffffff); content.graphics.drawRoundRect(0, 0, totalW, totalH, 10, 10); content.graphics.endFill(); var marker:Sprite = new Sprite(); marker.addChild(content); content.x = 30; content.y = 0; marker.graphics.lineStyle(); marker.graphics.beginFill(0xff0000); marker.graphics.drawCircle(0, totalH + 30, 3); marker.graphics.endFill(); marker.graphics.lineStyle(2, 0xffffff); marker.graphics.moveTo(30 + 10, totalH - 10); marker.graphics.lineTo(0, totalH + 30); return marker; } /** * Handles click on the Panoramio icon. */ private function onPanoramioIconClick(event:MouseEvent):void { navigateToURL(new URLRequest(PANORAMIO_HOME)); } /** * Handles failure of a Panoramio image load. */ private function onPanoramioDataFailed(event:IOErrorEvent):void { trace("Load of image failed: " + event); } /** * Returns a string containing cgi query parameters. * @param Associative array mapping query parameter key to value. * @return String containing cgi query parameters. */ private static function paramsToString(params:Object):String { var result:String = ""; var separator:String = ""; for (var key:String in params) { result += separator + encodeURIComponent(key) + "=" + encodeURIComponent(params[key]); separator = "&"; } return result; } /** * Called once the lead-in flight is done. Starts the car driving along * the route and starts a timer to begin fade in of the Panoramio * images in 1.5 seconds. */ private function onLeadInDone(event:Event):void { // Set startTimer non-zero so that the car starts to move. startTimer = getTimer(); // Start a timer that will fade in the Panoramio images. var fadeInTimer:Timer = new Timer(1500, 1); fadeInTimer.addEventListener(TimerEvent.TIMER, onFadeInTimer); fadeInTimer.start(); } /** * Handles the fade in timer&apos;s TIMER event. Sets markerAlpha above zero * which causes the frame enter handler to fade in the markers. */ private function onFadeInTimer(event:Event):void { markerAlpha = 0.01; } /** * The end time of the flight. */ private function get endTime():Number { if (!cumulativeStepDuration || cumulativeStepDuration.length == 0) { return startTimer; } return startTimer + cumulativeStepDuration[cumulativeStepDuration.length - 1]; } /** * Creates the cumulative arrays, cumulativeStepDuration and * cumulativeVertexDistance. */ private function createCumulativeArrays():void { cumulativeStepDuration = new Array(route.numSteps + 1); cumulativeVertexDistance = new Array(polyline.getVertexCount() + 1); var polylineTotal:Number = 0; var total:Number = 0; var numVertices:int = polyline.getVertexCount(); for (var stepIndex:int = 0; stepIndex < route.numSteps; ++stepIndex) { cumulativeStepDuration[stepIndex] = total; total += route.getStep(stepIndex).duration; var startVertex:int = stepIndex >= 0 ? route.getStep(stepIndex).polylineIndex : 0; var endVertex:int = stepIndex < (route.numSteps - 1) ? route.getStep(stepIndex + 1).polylineIndex : numVertices; var duration:Number = route.getStep(stepIndex).duration; var stepVertices:int = endVertex - startVertex; var latLng:LatLng = polyline.getVertex(startVertex); for (var vertex:int = startVertex; vertex < endVertex; ++vertex) { cumulativeVertexDistance[vertex] = polylineTotal; if (vertex < numVertices - 1) { var nextLatLng:LatLng = polyline.getVertex(vertex + 1); polylineTotal += nextLatLng.distanceFrom(latLng); } latLng = nextLatLng; } } cumulativeStepDuration[stepIndex] = total; } /** * Opens the info window above the car icon that details the given * step of the driving directions. * @param stepIndex Index of the current step. */ private function openInfoForStep(stepIndex:int):void { // Sets the content of the info window. var content:String; if (stepIndex >= route.numSteps) { content = "<b>" + route.endGeocode.address + "</b>" + "<br /><br />" + route.summaryHtml; } else { content = "<b>" + stepIndex + ".</b> " + route.getStep(stepIndex).descriptionHtml; } marker.openInfoWindow(new InfoWindowOptions({ contentHTML: content })); } /** * Displays the driving directions step appropriate for the given time. * Opens the info window showing the step instructions each time we * progress to a new step. * @param time Time for which to display the step. */ private function displayStepAt(time:Number):void { var stepIndex:int = upperBound(cumulativeStepDuration, time) - 1; var minStepIndex:int = 0; var maxStepIndex:int = route.numSteps - 1; if (stepIndex >= 0 && stepIndex <= maxStepIndex && currentStepIndex != stepIndex) { openInfoForStep(stepIndex); currentStepIndex = stepIndex; } } /** * Returns the LatLng at which the car should be positioned at the given * time. * @param time Time for which LatLng should be found. * @return LatLng. */ private function latLngAt(time:Number):LatLng { var stepIndex:int = upperBound(cumulativeStepDuration, time) - 1; var minStepIndex:int = 0; var maxStepIndex:int = route.numSteps - 1; if (stepIndex < minStepIndex) { return route.startGeocode.point; } else if (stepIndex > maxStepIndex) { return route.endGeocode.point; } var stepStart:Number = cumulativeStepDuration[stepIndex]; var stepEnd:Number = cumulativeStepDuration[stepIndex + 1]; var stepFraction:Number = (time - stepStart) / (stepEnd - stepStart); var startVertex:int = route.getStep(stepIndex).polylineIndex; var endVertex:int = (stepIndex + 1) < route.numSteps ? route.getStep(stepIndex + 1).polylineIndex : polyline.getVertexCount(); var stepVertices:int = endVertex - startVertex; var stepLeng

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  • Is this a File Header / Magic Number?

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    I've got 120,000 files (way more, actually; this is just an arbitrary subset) of an unknown type. Linux file does not identify them (not that they're necessarily Linux files), nor do any other methods I've tried. There are only two hints about them that I currently have. One is that I suspect some compression is employed -- I have metadata that claims the file sizes are always some amount larger than what I observe. The other is that in 100,000 of these files, the first 16 bytes are always: ff ee ee dd 00 00 00 00 01 00 00 00 00 00 00 00 That really looks like a file header/magic number to me, but I just can't place it. Does anyone know what kind of files this would indicate? Alternatively, can anyone convince me that these suspiciously common bytes certainly do not indicate a specific file type? UPDATE I don't know the exact reverse-engineering details, but most of the files in our case are zips after the first 29(? or so) bytes are ignored. So in practice the problem is solved (we know how to process the files) but in theory the question is still unanswered -- I don't know which application routinely prepends about 29 bytes to its zips. [I'm not sure if I should leave the question open or not at this point.]

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    Whilst doing exam revision I am having trouble answering the following question from the book, "An Introduction to the Theory of Computation" by Sipser. Unfortunately there's no solution to this question in the book. Explain why the following is not a legitimate Turing machine. M = { The input is a polynomial p over variables x1, ..., xn Try all possible settings of x1, ..., xn to integer values Evaluate p on all of these settings If any of these settings evaluates to 0, accept; otherwise reject. } This is driving me crazy! I suspect it is because the set of integers is infinite? Does this somehow exceed the alphabet's allowable size? Thanks!

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