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  • In TCP/IP terms, how does a download speed limiter in an office work?

    - by TessellatingHeckler
    Assume an office of people, they want to limit HTTP downloads to a max of 40% bandwidth of their internet connection speed so that it doesn't block other traffic. We say "it's not supported in your firewall", and they say the inevitable line "we used to be able to do it with our Netgear/DLink/DrayTek". Thinking about it, a download is like this: HTTP GET request Server sends file data as TCP packets Client acknowledges receipt of TCP packets Repeat until download finished. The speed is determined by how fast the server sends data to you, and how fast you acknowledge it. So, to limit download speed, you have two choices: 1) Instruct the server to send data to you more slowly - and I don't think there's any protocol feature to request that in TCP or HTTP. 2) Acknowledge packets more slowly by limiting your upload speed, and also ruin your upload speed. How do devices do this limiting? Is there a standard way?

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  • Can I increase the link speed of the RAS Server on our MS Win2k3 box?

    - by Ducain
    We are running a Win2K3 Server box, and I'm a remote employee that connects via VPN. I've been frustrated for some time by the connection speed over the VPN (the office HQ has a decent speed and I have a biz class connection here), and decided to do some checking today. This morning, I was dialed in and looked at the networking tab of the task manager, and I see that the adapter for the RAS Server (the box has 4 Gigabit adapters) has a speed that seems far too low. The speed for the RAS Server link hovers between 300 - 600 Kbps. The local connection (and others) all say 1 Gbps. Can I set this to a higher speed? Is this information accurate? Thanks for the input.

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  • Multimaster Keepalived Configuration (Virtual IP with Load Balancing)

    - by Rad Akefirad
    Here are requirements: 1. High Availability 2. Load Balancing First configuration 1. Two linux servers have been configured with one static IP for each: 10.17.243.11, 10.17.243.12 2. Keepalived has been installed and configured with one VRRP instance to provide one virtual IP (10.17.243.10 as VIP, 10.17.243.11 as master and 10.17.243.12 as backup). 3. Everything works fine. The VIP is assigned to the master server (10.17.243.11) as long as it is up and running. As soon as it goes down, the VIP will be assigned to the backup server (10.17.243.12). 4. The problem here is all communication goes to the master server. Second configuration 1. I found active-active configuration for Keepalived which is possible by defining more than one VRRP instance. So that both server have two IPs (real 10.17.243.11 and virtual 10.17.243.10 for server #1 and real 10.17.243.12 and virtual 10.17.243.20 for server #2. 2. Everything works fine. we have two VIPs which are accessible (HA). But all communication coming to each IP still goes to one single machine (either server #1 or #2 depending on the IP). However I found some tricks on the DNS to overcome this limitation. But it's not acceptable in our case. Question: Is there any way to have one virtual IP which is assigned to both servers? By that I mean both servers are handling some part of workload (like the thing we do in web server load balancing)? By using either keepalived or some other tools? Thanks in advance.

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  • How should I perform database maintenance on a 24x7 system

    - by solublefish
    I'm a software developer who inherited a part-time DBA role. I'm responsible for an application backed by a small, high-volume 24x7 database on SQL Server 2008. While there's other stuff in the DB, the critical piece is a 50GB, 7.5M row table that serves 100K requests/sec during peak load, and about half that at "night". This is 99%+ read traffic, but the writes are constant, and required. I need to be able to perform periodic maintenance without a maintenance window. Say an index rebuild, a job to purge old data, Windows Update, or hardware upgrade. Most of the advice I've seen is along the lines of "MAKE a maintenance window." While I appreciate the sentiment, I hope there's another way. If it will solve this problem, I do have the ability to purchase new hardware or modify the database, the clients (a set of web services servers), and much of the application code (ADO.NET + ASP.NET). I've been thinking along the lines of using the warm spare (or a 3rd server) to do the maintenance, and then "swap" it into production. 1 Synchronize the spare by restoring backups, including a current transaction log. 2 Perform the maintenance tasks. 3 Reconfigure clients to connect to the spare server. Existing connections are finished within a minute or so. 4 The spare server is now the production server. The problem remaining is that the new production server is now out of date by however long it took to perform maintenance. Is there some way that the original production server can be made to queue up changes and merge them to the spare between steps 2 and 3? Any other ideas?

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  • Keepalived for more than 20 virtual addresses

    - by cvaldemar
    I have set up keepalived on two Debian machines for high availability, but I've run into the maximum number of virtual IP's I can assign to my vrrp_instance. How would I go about configuring and failing over 20+ virtual IP's? This is the, very simple, setup: LB01: 10.200.85.1 LB02: 10.200.85.2 Virtual IPs: 10.200.85.100 - 10.200.85.200 Each machine is also running Apache (later Nginx) binding on the virtual IPs for SSL client certificate termination and proxying to backend webservers. The reason I need so many VIP's is the inability to use VirtualHost on HTTPS. This is my keepalived.conf: vrrp_script chk_apache2 { script "killall -0 apache2" interval 2 weight 2 } vrrp_instance VI_1 { interface eth0 state MASTER virtual_router_id 51 priority 101 virtual_ipaddress { 10.200.85.100 . . all the way to . 10.200.85.200 } An identical configuration is on the BACKUP machine, and it's working fine, but only up to the 20th IP. I have found a HOWTO discussing this problem. Basically, they suggest having just one VIP and routing all traffic "via" this one IP, and "all will be well". Is this a good approach? I'm running pfSense firewalls in front of the machines. Quote from the above link: ip route add $VNET/N via $VIP or route add $VNET netmask w.x.y.z gw $VIP Thanks in advance. EDIT: @David Schwartz said it would make sense to add a route, so I tried adding a static route to the pfSense firewall, but that didn't work as I expected it would. pfSense route: Interface: LAN Destination network: 10.200.85.200/32 (virtual IP) Gateway: 10.200.85.100 (floating virtual IP) Description: Route to VIP .100 I also made sure I had packet forwarding enabled on my hosts: $ cat /etc/sysctl.conf net.ipv4.ip_forward=1 net.ipv4.ip_nonlocal_bind=1 Am I doing this wrong? I also removed all VIPs from the keepalived.conf so it only fails over 10.200.85.100.

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  • How to make speed of scrolling more slower in this jQuery scrolling script?

    - by Jitendra Vyas
    Currently in example speed and step both are are 1. but i need much slower speed of scrolling. How to get full control over speed. I want the clouds to move much slower Example http://jsfiddle.net/cHZG6/1/ Code (function($) { $.fn.scrollingBackground = function(options) { // settings and defaults. var settings = options || {}; var speed = settings.speed || 1; var step = settings.step || 1; var direction = settings.direction || 'rtl'; var animStep; // build up a string to pass to animate: if (direction === 'rtl') { animStep = "-=" + step + "px"; } else if (direction === 'ltr') { animStep = '+=' + step + "px"; } var element = this; // perform the animation forever: var animate = function() { element.animate({ backgroundPosition: animStep + " 0px" }, speed, animate); }; animate(); }; })(jQuery); $("#header").scrollingBackground({ speed: 1, step: 1, direction: 'ltr' }); $("#header-2").scrollingBackground({ speed: 1, step: 1, direction: 'rtl' });

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  • Wireless Network Performance Issues

    - by colithium
    My brand new Dell XPS system has been running flawlessly except its abysmal download speeds. I have tried isolating every variable I could possibly think of but I can't figure out the problem. I've talked to Dell and Belkin without making progress (thought I'd try). Here are the speeds: Note that most of the time, upload speeds are actually much faster than download speeds (around 4.0 Mb/s which is better than most other devices on the network) It's not the ISP. The slowdown happens even when transferring files inside the network. Plus every other wireless device gets approximately this: It's not the wireless router. It's a Lynksis WRT160N v1 with the latest firmware (1.02.2). Plus everything else connected to it has normal speeds. It's not the browser. Speeds are the same in IE, FF, and when transferring files with Windows between computers. It's not the wireless adapter. I've tried a Belkin N Wireless USB Adapter (which works fine on another computer) and a Dell Wireless Draft 802.11n WLAN Mini-Card. They have the same slow speeds when connected to the problem computer. It's not the adapter connection. One adapter used USB and the other is a Mini-Card. It's not antenna placement. With the same antenna position and the same device, I get different speeds when connected to the problem computer vs a good computer. Plus everything reports the connection speed as at least 11Mbps and good signal strength. I've tried disabling IPv6 since it sometimes causes weird problems. I've tried disabling Windows Firewall/anti-virus. I've ensured the computer has updated drivers for both adapters. I've ensured that Windows is up to date and so is the BIOS. For the USB adapter I ensured that that USB port functioned at normal speeds with other USB devices. What else could it possibly be? I finally received my copy of Windows 7 and will be trying that. I'd rather not install Windows 7 because of a particular program that will stop working so a solution besides that is welcome. Specs: Vista x64 Core i7 920 6GB RAM 500GB HD GTX 260

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  • Tips / techniques for high-performance C# server sockets

    - by McKenzieG1
    I have a .NET 2.0 server that seems to be running into scaling problems, probably due to poor design of the socket-handling code, and I am looking for guidance on how I might redesign it to improve performance. Usage scenario: 50 - 150 clients, high rate (up to 100s / second) of small messages (10s of bytes each) to / from each client. Client connections are long-lived - typically hours. (The server is part of a trading system. The client messages are aggregated into groups to send to an exchange over a smaller number of 'outbound' socket connections, and acknowledgment messages are sent back to the clients as each group is processed by the exchange.) OS is Windows Server 2003, hardware is 2 x 4-core X5355. Current client socket design: A TcpListener spawns a thread to read each client socket as clients connect. The threads block on Socket.Receive, parsing incoming messages and inserting them into a set of queues for processing by the core server logic. Acknowledgment messages are sent back out over the client sockets using async Socket.BeginSend calls from the threads that talk to the exchange side. Observed problems: As the client count has grown (now 60-70), we have started to see intermittent delays of up to 100s of milliseconds while sending and receiving data to/from the clients. (We log timestamps for each acknowledgment message, and we can see occasional long gaps in the timestamp sequence for bunches of acks from the same group that normally go out in a few ms total.) Overall system CPU usage is low (< 10%), there is plenty of free RAM, and the core logic and the outbound (exchange-facing) side are performing fine, so the problem seems to be isolated to the client-facing socket code. There is ample network bandwidth between the server and clients (gigabit LAN), and we have ruled out network or hardware-layer problems. Any suggestions or pointers to useful resources would be greatly appreciated. If anyone has any diagnostic or debugging tips for figuring out exactly what is going wrong, those would be great as well. Note: I have the MSDN Magazine article Winsock: Get Closer to the Wire with High-Performance Sockets in .NET, and I have glanced at the Kodart "XF.Server" component - it looks sketchy at best.

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  • iptable CLUSTERIP won't work

    - by Rad Akefirad
    We have some requirements which explained here. We tried to satisfy them without any success as described. Here is the brief information: Here are requirements: 1. High Availability 2. Load Balancing Current Configuration: Server #1: one static (real) IP for each 10.17.243.11 Server #2: one static (real) IP for each 10.17.243.12 Cluster (virtual and shared among all servers) IP: 10.17.243.15 I tried to use CLUSTERIP to have the cluster IP by the following: on the server #1 iptables -I INPUT -i eth0 -d 10.17.243.15 -j CLUSTERIP --new --hashmode sourceip --clustermac 01:00:5E:00:00:20 --total-nodes 2 --local-node 1 on the server #2 iptables -I INPUT -i eth0 -d 10.17.243.15 -j CLUSTERIP --new --hashmode sourceip --clustermac 01:00:5E:00:00:20 --total-nodes 2 --local-node 2 When we try to ping 10.17.243.15 there is no reply. And the web service (tomcat on port 8080) is not accessible either. However we managed to get the packets on both servers by using TCPDUMP. Some useful information: iptable roules (iptables -L -n -v): Chain INPUT (policy ACCEPT 21775 packets, 1470K bytes) pkts bytes target prot opt in out source destination 0 0 CLUSTERIP all -- eth0 * 0.0.0.0/0 10.17.243.15 CLUSTERIP hashmode=sourceip clustermac=01:00:5E:00:00:20 total_nodes=2 local_node=1 hash_init=0 Chain FORWARD (policy ACCEPT 0 packets, 0 bytes) pkts bytes target prot opt in out source destination Chain OUTPUT (policy ACCEPT 14078 packets, 44M bytes) pkts bytes target prot opt in out source destination Log messages: ... kernel: [ 7.329017] e1000e: eth3 NIC Link is Up 100 Mbps Full Duplex, Flow Control: None ... kernel: [ 7.329133] e1000e 0000:05:00.0: eth3: 10/100 speed: disabling TSO ... kernel: [ 7.329567] ADDRCONF(NETDEV_CHANGE): eth3: link becomes ready ... kernel: [ 71.333285] ip_tables: (C) 2000-2006 Netfilter Core Team ... kernel: [ 71.341804] nf_conntrack version 0.5.0 (16384 buckets, 65536 max) ... kernel: [ 71.343168] ipt_CLUSTERIP: ClusterIP Version 0.8 loaded successfully ... kernel: [ 108.456043] device eth0 entered promiscuous mode ... kernel: [ 112.678859] device eth0 left promiscuous mode ... kernel: [ 117.916050] device eth0 entered promiscuous mode ... kernel: [ 140.168848] device eth0 left promiscuous mode TCPDUMP while pinging: tcpdump: listening on eth0, link-type EN10MB (Ethernet), capture size 65535 bytes 12:11:55.335528 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto ICMP (1), length 84) 10.17.243.1 > 10.17.243.15: ICMP echo request, id 16162, seq 2390, length 64 12:11:56.335778 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto ICMP (1), length 84) 10.17.243.1 > 10.17.243.15: ICMP echo request, id 16162, seq 2391, length 64 12:11:57.336010 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto ICMP (1), length 84) 10.17.243.1 > 10.17.243.15: ICMP echo request, id 16162, seq 2392, length 64 12:11:58.336287 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto ICMP (1), length 84) 10.17.243.1 > 10.17.243.15: ICMP echo request, id 16162, seq 2393, length 64 And there is no ping reply as I said. Does anyone know which part I missed? Thanks in advance.

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  • Any high-profile open source finance projects?

    - by Gayle
    Is there a high profile open source project in the finance industry - specifically the investment banking area - that I could contribute to (ideally .NET)? I'd like to beef up my resume in this field. I would prefer something in the algorithmic trading field, but am open to any route (e.g. front-office applications, etc).

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  • High performance web (-services) applications

    - by User Friendly
    Hi, I'd like to become a guru in high performance web & web-services applications. What technologies/patterns/skills do you reccomend to look at? Basically, I have good skills at ASP.NET/.NET based web development, but I'd like to know how big things are built (on any platform, not depending on .net technology stack). Thank you.

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  • Delphi/Pascal training in high school/college/university

    - by Bruce McGee
    Are Delphi/Pascal being taught in any high schools/colleges/universities, particularly in Canada and the US? I was surprised how many schools in the UK are teaching Delphi. Their largest exam board is even dropping PHP/C#/C in 2011 and encouraging Delphi. I also remember that CodeGear was going to provide development tool licenses to Russian schools a couple of years ago. I'd like to know if it's being taught closer to (my) home.

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  • PHP Stop Word List

    - by Dom Hodgson
    I'm playing about with a stop words within my code I have an array full of words that I'd like to check, and an array of words I want to check against. At the moment I'm looping through the array one at at a time and removing the word if its in_array vs the stop word list but I wonder if there's a better way of doing it, I've looked at array_diff and such however if I have multiple stop words in the first array, array_diff only appears to remove the first occurrence. The focus is on speed and memory usage but speed more so. Thanks

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  • Windows Disk I/O Analysis

    - by Jonathon
    It appears that we are having a problem with the disk i/o speed on our Windows 2003 Enterprise Edition server (64-bit). As we were initializing a database that created two 1G tablespaces on 3 different machines, it became obvious that the two smaller machines (each 32-bit Windows 2003 Standard Edition with less RAM) killed the larger machine when creating the files. The larger machine took 10x as long to create the tablespaces than did the other machines. Now, I am left wondering how that could be. What programs or scripts would you guys recommend for tracking down the I/O problem? I think the issue may be with the controller card (all boxes are hardware RAID 10, but have different controller cards), but I would like to check the actual disk I/O speed as well, so I have some hard numbers to work with. Any help would be appreciated.

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  • High-Quality Text-To-Speech engine for personal use

    - by phihag
    I'm looking for a high-quality TTS engine that I can afford (let's say less than 1000$). So far, I've tried flite and festival. However, while the results are certainly understandable, technical texts are hard to follow. Commercial TTS solutions from Loquendo and Readspeaker sound way better. However, these companies don't seem to be willing to sell their product to mere mortals - I can't find a price on either's homepage. So, what are good TTS solutions for personal use?

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  • Release build in MVS 2010 professional v/s express for C

    - by yCalleecharan
    Hi, recently I discovered that "executing" a C program as a release build instead of a debug build optimizes the code and makes it run much faster. This is accessed through project properties configuration manager menu. I would like to know if this feature is the same in the professional version and the express edition of MVS 2010 in terms of speed optimization. I have the express edition. Also, I would like to know if C programs run with the same speed as in both the professional and express editions. I understand that the professional edition has many "software" tools for the serious programmer. Thanks a lot..

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  • High-level languages for out-of-the-box GUI desktop application programming

    - by Omeoe
    After I discontinued programming in C++ while entering into web authoring I was spoilt by PHP's high level constructs like hash tables or its dynamic, weak typing. I remembered the angst of C/C++ pointers and the maze of low-level Win32 API handles and message loops and that prevented me from utilizing environments like Code::Blocks for desktop applications. I am also not very fond of bulky, statically-typed C#/.NET environment. Any other ideas?

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  • How to make an object move again after being stopped by collision in Unity?

    - by Matthew Underwood
    I have a player object which position is always centered on the main camera's viewport. This object has a Rigidbody 2D, a box and circle collider. The player moves around a level, the level has a polygon collider attached. I move the camera until the object hits against the collider, which stops the movement of the camera by setting its speed to 0. The problem happens when I want to move the camera / player object away from the collider. As the speed is already at 0, it cannot move away from the collider. The script attached to the player object, checks for collisions and applies the speed to 0 on the main camera's test script. using UnityEngine; using System.Collections; public class move : MonoBehaviour { public float speed; public test testing; // Use this for initialization void Start () { speed = 10F; testing = Camera.main.GetComponent<test>(); } // Update is called once per frame void FixedUpdate () { Vector3 p = Camera.main.ViewportToWorldPoint(new Vector3(0.5F, 0.5F, Camera.main.nearClipPlane)); transform.position = new Vector3(p.x, p.y, -1); } void OnCollisionEnter2D(Collision2D col) { testing.speed = 0; } void OnCollisionExit2D(Collision2D col) { testing.speed = 10F; } } This is the script attached to the main camera; just a simple script that changes the camera's position. using UnityEngine; using System.Collections; public class test : MonoBehaviour { public float speed; public float translationY; public float translationX; // Use this for initialization void Start () { speed = 10F; } void FixedUpdate () { translationY = Input.GetAxis("Vertical") * speed * Time.deltaTime; translationX = Input.GetAxis("Horizontal") * speed * Time.deltaTime; transform.Translate(translationX, translationY, 0); } } The player object isn't kinematic and is a fixed angle, the colliders aren't triggers and the polygon collider isn't a trigger either. The player is the red square, the collider is the pink area. -- EDIT -- From the latest change the collider set up for the player So if the X speed was disabled. It wouldnt move into the side of the polygon colider which is good, but yet you couldnt move away from it. And moving down would move inside the colider.

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  • procedure that swaps the bytes (low/high) of a Word variable

    - by Altar
    Hi. I have this procedure that swaps the bytes (low/high) of a Word variable (It does the same stuff as System.Swap function). The procedure works when the compiler optimization is OFF but not when it is ON. Can anybody help me with this? { UNSAFE! IT IS NOW WORKING WHEN COMPILER OPTIMIZATION IS ON ! } procedure SwapWord_NotWorking(VAR TwoBytes: word); asm Mov EBX, TwoBytes Mov AX, [EBX] XCHG AL,AH Mov [EBX], AX end;

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  • Tips for maximizing Nginx requests/sec?

    - by linkedlinked
    I'm building an analytics package, and project requirements state that I need to support 1 billion hits per day. Yep, "billion". In other words, no less than 12,000 hits per second sustained, and preferably some room to burst. I know I'll need multiple servers for this, but I'm trying to get maximum performance out of each node before "throwing more hardware at it". Right now, I have the hits-tracking portion completed, and well optimized. I pretty much just save the requests straight into Redis (for later processing with Hadoop). The application is Python/Django with a gunicorn for the gateway. My 2GB Ubuntu 10.04 Rackspace server (not a production machine) can serve about 1200 static files per second (benchmarked using Apache AB against a single static asset). To compare, if I swap out the static file link with my tracking link, I still get about 600 requests per second -- I think this means my tracker is well optimized, because it's only a factor of 2 slower than serving static assets. However, when I benchmark with millions of hits, I notice a few things -- No disk usage -- this is expected, because I've turned off all Nginx logs, and my custom code doesn't do anything but save the request details into Redis. Non-constant memory usage -- Presumably due to Redis' memory managing, my memory usage will gradually climb up and then drop back down, but it's never once been my bottleneck. System load hovers around 2-4, the system is still responsive during even my heaviest benchmarks, and I can still manually view http://mysite.com/tracking/pixel with little visible delay while my (other) server performs 600 requests per second. If I run a short test, say 50,000 hits (takes about 2m), I get a steady, reliable 600 requests per second. If I run a longer test (tried up to 3.5m so far), my r/s degrades to about 250. My questions -- a. Does it look like I'm maxing out this server yet? Is 1,200/s static files nginx performance comparable to what others have experienced? b. Are there common nginx tunings for such high-volume applications? I have worker threads set to 64, and gunicorn worker threads set to 8, but tweaking these values doesn't seem to help or harm me much. c. Are there any linux-level settings that could be limiting my incoming connections? d. What could cause my performance to degrade to 250r/s on long-running tests? Again, the memory is not maxing out during these tests, and HDD use is nil. Thanks in advance, all :)

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  • High accuracy cpu timers

    - by John Robertson
    An expert in highly optimized code once told me that an important part of his strategy was the availability of extremely high performance timers on the CPU. Does anyone know what those are and how one can access them to test various code optimizations? While I am interested regardless, I also wanted to ask whether it is possible to access them from something higher than assembly (or with only a little assembly) via visual studio C++?

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  • how to fast compute distance between high dimension vectors

    - by chyojn
    assume there are three group of high dimension vectors: {a_1, a_2, ..., a_N}, {b_1, b_2, ... , b_N}, {c_1, c_2, ..., c_N}. each of my vector can be represented as: x = a_i + b_j + c_k, where 1 <=i, j, k <= N. then the vector is encoded as (i, j, k) wich is then can be decoded as x = a_i + b_j + c_k. my question is, if there are two vector: x = (i_1, j_1, k_1), y = (i_2, j_2, k_2), is there a method to compute the euclidian distance of these two vector without decode x and y.

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