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• Threading Overview

  - by ACShorten

  One of the major features of the batch framework is the ability to support multi-threading. The multi-threading support allows a site to increase throughput on an individual batch job by splitting the total workload across multiple individual threads. This means each thread has fine level control over a segment of the total data volume at any time. The idea behind the threading is based upon the notion that "many hands make light work". Each thread takes a segment of data in parallel and operates on that smaller set. The object identifier allocation algorithm built into the product randomly assigns keys to help ensure an even distribution of the numbers of records across the threads and to minimize resource and lock contention. The best way to visualize the concept of threading is to use a "pie" analogy. Imagine the total workset for a batch job is a "pie". If you split that pie into equal sized segments, each segment would represent an individual thread. The concept of threading has advantages and disadvantages: Smaller elapsed runtimes - Jobs that are multi-threaded finish earlier than jobs that are single threaded. With smaller amounts of work to do, jobs with threading will finish earlier. Note: The elapsed runtime of the threads is rarely proportional to the number of threads executed. Even though contention is minimized, some contention does exist for resources which can adversely affect runtime. Threads can be managed individually – Each thread can be started individually and can also be restarted individually in case of failure. If you need to rerun thread X then that is the only thread that needs to be resubmitted. Threading can be somewhat dynamic – The number of threads that are run on any instance can be varied as the thread number and thread limit are parameters passed to the job at runtime. They can also be configured using the configuration files outlined in this document and the relevant manuals.Note: Threading is not dynamic after the job has been submitted Failure risk due to data issues with threading is reduced – As mentioned earlier individual threads can be restarted in case of failure. This limits the risk to the total job if there is a data issue with a particular thread or a group of threads. Number of threads is not infinite – As with any resource there is a theoretical limit. While the thread limit can be up to 1000 threads, the number of threads you can physically execute will be limited by the CPU and IO resources available to the job at execution time. Theoretically with the objects identifiers evenly spread across the threads the elapsed runtime for the threads should all be the same. In other words, when executing in multiple threads theoretically all the threads should finish at the same time. Whilst this is possible, it is also possible that individual threads may take longer than other threads for the following reasons: Workloads within the threads are not always the same - Whilst each thread is operating on the roughly the same amounts of objects, the amount of processing for each object is not always the same. For example, an account may have a more complex rate which requires more processing or a meter has a complex amount of configuration to process. If a thread has a higher proportion of objects with complex processing it will take longer than a thread with simple processing. The amount of processing is dependent on the configuration of the individual data for the job. Data may be skewed – Even though the object identifier generation algorithm attempts to spread the object identifiers across threads there are some jobs that use additional factors to select records for processing. If any of those factors exhibit any data skew then certain threads may finish later. For example, if more accounts are allocated to a particular part of a schedule then threads in that schedule may finish later than other threads executed. Threading is important to the success of individual jobs. For more guidelines and techniques for optimizing threading refer to Multi-Threading Guidelines in the Batch Best Practices for Oracle Utilities Application Framework based products (Doc Id: 836362.1) whitepaper available from My Oracle Support

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• Using Appendbuffers in unity for terrain generation

  - by Wardy

  Like many others I figured I would try and make the most of the monster processing power of the GPU but I'm having trouble getting the basics in place. CPU code: using UnityEngine; using System.Collections; public class Test : MonoBehaviour { public ComputeShader Generator; public MeshTopology Topology; void OnEnable() { var computedMeshPoints = ComputeMesh(); CreateMeshFrom(computedMeshPoints); } private Vector3[] ComputeMesh() { var size = (32*32) * 4; // 4 points added for each x,z pos var buffer = new ComputeBuffer(size, 12, ComputeBufferType.Append); Generator.SetBuffer(0, "vertexBuffer", buffer); Generator.Dispatch(0, 1, 1, 1); var results = new Vector3[size]; buffer.GetData(results); buffer.Dispose(); return results; } private void CreateMeshFrom(Vector3[] generatedPoints) { var filter = GetComponent<MeshFilter>(); var renderer = GetComponent<MeshRenderer>(); if (generatedPoints.Length > 0) { var mesh = new Mesh { vertices = generatedPoints }; var colors = new Color[generatedPoints.Length]; var indices = new int[generatedPoints.Length]; //TODO: build this different based on topology of the mesh being generated for (int i = 0; i < indices.Length; i++) { indices[i] = i; colors[i] = Color.blue; } mesh.SetIndices(indices, Topology, 0); mesh.colors = colors; mesh.RecalculateNormals(); mesh.Optimize(); mesh.RecalculateBounds(); filter.sharedMesh = mesh; } else { filter.sharedMesh = null; } } } GPU code: #pragma kernel Generate AppendStructuredBuffer<float3> vertexBuffer : register(u0); void genVertsAt(uint2 xzPos) { //TODO: put some height generation code here. // could even run marching cubes / dual contouring code. float3 corner1 = float3( xzPos[0], 0, xzPos[1] ); float3 corner2 = float3( xzPos[0] + 1, 0, xzPos[1] ); float3 corner3 = float3( xzPos[0], 0, xzPos[1] + 1); float3 corner4 = float3( xzPos[0] + 1, 0, xzPos[1] + 1 ); vertexBuffer.Append(corner1); vertexBuffer.Append(corner2); vertexBuffer.Append(corner3); vertexBuffer.Append(corner4); } [numthreads(32, 1, 32)] void Generate (uint3 threadId : SV_GroupThreadID, uint3 groupId : SV_GroupID) { uint2 currentXZ = unint2( groupId.x * 32 + threadId.x, groupId.z * 32 + threadId.z); genVertsAt(currentXZ); } Can anyone explain why when I call "buffer.GetData(results);" on the CPU after the compute dispatch call my buffer is full of Vector3(0,0,0), I'm not expecting any y values yet but I would expect a bunch of thread indexes in the x,z values for the Vector3 array. I'm not getting any errors in any of this code which suggests it's correct syntax-wise but maybe the issue is a logical bug. Also: Yes, I know I'm generating 4,000 Vector3's and then basically round tripping them. However, the purpose of this code is purely to learn how round tripping works between CPU and GPU in Unity.

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• methods DSA_do_verify and SHA1 (OpenSSL library for Windows)

  - by Rei

  i am working on a program to authenticate an ENC signature file by using OpenSSL for windows, and specifically methods DSA_do_verify(...) and SHA1(...) hash algorithm, but is having problems as the result from DSA_do_verify is always 0 (invalid). I am using the signature file of test set 4B from the IHO S-63 Data Protection Scheme, and also the SA public key (downloadable from IHO) for verification. Below is my program, can anyone help to see where i have gone wrong as i have tried many ways but failed to get the verification to be valid, thanks.. The signature file from test set 4B // Signature part R: 3F14 52CD AEC5 05B6 241A 02C7 614A D149 E7D6 C408. // Signature part S: 44BB A3DB 8C46 8D11 B6DB 23BE 1A79 55E6 B083 7429. // Signature part R: 93F5 EF86 1FF6 BA6F 1C2B B9BB 7F36 0C80 2F9B 2414. // Signature part S: 4877 8130 12B4 50D8 3688 B52C 7A84 8E26 D442 8B6E. // BIG p C16C BAD3 4D47 5EC5 3966 95D6 94BC 8BC4 7E59 8E23 B5A9 D7C5 CEC8 2D65 B682 7D44 E953 7848 4730 C0BF F1F4 CB56 F47C 6E51 054B E892 00F3 0D43 DC4F EF96 24D4 665B. // BIG q B7B8 10B5 8C09 34F6 4287 8F36 0B96 D7CC 26B5 3E4D. // BIG g 4C53 C726 BDBF BBA6 549D 7E73 1939 C6C9 3A86 9A27 C5DB 17BA 3CAC 589D 7B3E 003F A735 F290 CFD0 7A3E F10F 3515 5F1A 2EF7 0335 AF7B 6A52 11A1 1035 18FB A44E 9718. // BIG y 15F8 A502 11C2 34BB DF19 B3CD 25D1 4413 F03D CF38 6FFC 7357 BCEE 59E4 EBFD B641 6726 5E5F 0682 47D4 B50B 3B86 7A85 FB4D 6E01 8329 A993 C36C FD9A BFB6 ED6D 29E0. dataServer_pkeyfile.txt (extracted from above) // BIG p C16C BAD3 4D47 5EC5 3966 95D6 94BC 8BC4 7E59 8E23 B5A9 D7C5 CEC8 2D65 B682 7D44 E953 7848 4730 C0BF F1F4 CB56 F47C 6E51 054B E892 00F3 0D43 DC4F EF96 24D4 665B. // BIG q B7B8 10B5 8C09 34F6 4287 8F36 0B96 D7CC 26B5 3E4D. // BIG g 4C53 C726 BDBF BBA6 549D 7E73 1939 C6C9 3A86 9A27 C5DB 17BA 3CAC 589D 7B3E 003F A735 F290 CFD0 7A3E F10F 3515 5F1A 2EF7 0335 AF7B 6A52 11A1 1035 18FB A44E 9718. // BIG y 15F8 A502 11C2 34BB DF19 B3CD 25D1 4413 F03D CF38 6FFC 7357 BCEE 59E4 EBFD B641 6726 5E5F 0682 47D4 B50B 3B86 7A85 FB4D 6E01 8329 A993 C36C FD9A BFB6 ED6D 29E0. Program abstract: QbyteArray pk_data; QFile pk_file("./dataServer_pkeyfile.txt"); if (pk_file.open(QIODevice::Text | QIODevice::ReadOnly)) { pk_data.append(pk_file.readAll()); } pk_file.close(); unsigned char ptr_sha_hashed[20]; unsigned char *ptr_pk_data = (unsigned char *)pk_data.data(); // openssl SHA1 hashing algorithm SHA1(ptr_pk_data, pk_data.length(), ptr_sha_hashed); DSA_SIG *dsasig = DSA_SIG_new(); char ptr_r[] = "93F5EF861FF6BA6F1C2BB9BB7F360C802F9B2414"; //from tset 4B char ptr_s[] = "4877813012B450D83688B52C7A848E26D4428B6E"; //from tset 4B if (BN_hex2bn(&dsasig->r, ptr_r) == 0) return 0; if (BN_hex2bn(&dsasig->s, ptr_s) == 0) return 0; DSA *dsakeys = DSA_new(); //the following values are from the SA public key char ptr_p[] = "FCA682CE8E12CABA26EFCCF7110E526DB078B05EDECBCD1EB4A208F3AE1617AE01F35B91A47E6DF63413C5E12ED0899BCD132ACD50D99151BDC43EE737592E17"; char ptr_q[] = "962EDDCC369CBA8EBB260EE6B6A126D9346E38C5"; char ptr_g[] = "678471B27A9CF44EE91A49C5147DB1A9AAF244F05A434D6486931D2D14271B9E35030B71FD73DA179069B32E2935630E1C2062354D0DA20A6C416E50BE794CA4"; char ptr_y[] = "963F14E32BA5372928F24F15B0730C49D31B28E5C7641002564DB95995B15CF8800ED54E354867B82BB9597B158269E079F0C4F4926B17761CC89EB77C9B7EF8"; if (BN_hex2bn(&dsakeys->p, ptr_p) == 0) return 0; if (BN_hex2bn(&dsakeys->q, ptr_q) == 0) return 0; if (BN_hex2bn(&dsakeys->g, ptr_g) == 0) return 0; if (BN_hex2bn(&dsakeys->pub_key, ptr_y) == 0) return 0; int result; //valid = 1, invalid = 0, error = -1 result = DSA_do_verify(ptr_sha_hashed, 20, dsasig, dsakeys); //result is 0 (invalid)

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• WIF-less claim extraction from ACS: JWT

  - by Elton Stoneman

  ACS support for JWT still shows as "beta", but it meets the spec and it works nicely, so it's becoming the preferred option as SWT is losing favour. (Note that currently ACS doesn’t support JWT encryption, if you want encrypted tokens you need to go SAML). In my last post I covered pulling claims from an ACS token without WIF, using the SWT format. The JWT format is a little more complex, but you can still inspect claims just with string manipulation. The incoming token from ACS is still presented in the BinarySecurityToken element of the XML payload, with a TokenType of urn:ietf:params:oauth:token-type:jwt: <t:RequestSecurityTokenResponse xmlns:t="http://schemas.xmlsoap.org/ws/2005/02/trust">   <t:Lifetime>     <wsu:Created xmlns:wsu="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd">2012-08-31T07:39:55.337Z</wsu:Created>     <wsu:Expires xmlns:wsu="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd">2012-08-31T09:19:55.337Z</wsu:Expires>   </t:Lifetime>   <wsp:AppliesTo xmlns:wsp="http://schemas.xmlsoap.org/ws/2004/09/policy">     <EndpointReference xmlns="http://www.w3.org/2005/08/addressing">       <Address>http://localhost/x.y.z</Address>     </EndpointReference>   </wsp:AppliesTo>   <t:RequestedSecurityToken>     <wsse:BinarySecurityToken wsu:Id="_1eeb5cf4-b40b-40f2-89e0-a3343f6bd985-6A15D1EED0CDB0D8FA48C7D566232154" ValueType="urn:ietf:params:oauth:token-type:jwt" EncodingType="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-soap-message-security-1.0#Base64Binary" xmlns:wsu="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd" xmlns:wsse="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd">[ base64string ] </wsse:BinarySecurityToken>   </t:RequestedSecurityToken>   <t:TokenType>urn:ietf:params:oauth:token-type:jwt</t:TokenType>   <t:RequestType>http://schemas.xmlsoap.org/ws/2005/02/trust/Issue</t:RequestType>   <t:KeyType>http://schemas.xmlsoap.org/ws/2005/05/identity/NoProofKey</t:KeyType> </t:RequestSecurityTokenResponse> The token as a whole needs to be base-64 decoded. The decoded value contains a header, payload and signature, dot-separated; the parts are also base-64, but they need to be decoded using a no-padding algorithm (implementation and more details in this MSDN article on validating an Exchange 2013 identity token). The values are then in JSON; the header contains the token type and the hashing algorithm: "{"typ":"JWT","alg":"HS256"}" The payload contains the same data as in the SWT, but JSON rather than querystring format: {"aud":"http://localhost/x.y.z" "iss":"https://adfstest-bhw.accesscontrol.windows.net/" "nbf":1346398795 "exp":1346404795 "http://schemas.microsoft.com/ws/2008/06/identity/claims/authenticationinstant":"2012-08-31T07:39:53.652Z" "http://schemas.microsoft.com/ws/2008/06/identity/claims/authenticationmethod":"http://schemas.microsoft.com/ws/2008/06/identity/authenticationmethod/windows" "http://schemas.microsoft.com/ws/2008/06/identity/claims/windowsaccountname":"xyz" "http://schemas.xmlsoap.org/ws/2005/05/identity/claims/emailaddress":"[email protected]" "http://schemas.xmlsoap.org/ws/2005/05/identity/claims/upn":"[email protected]" "identityprovider":"http://fs.svc.x.y.z.com/adfs/services/trust"} The signature is in the third part of the token. Unlike SWT which is fixed to HMAC-SHA-256, JWT can support other protocols (the one in use is specified as the "alg" value in the header). How to: Validate an Exchange 2013 identity token contains an implementation of a JWT parser and validator; apart from the custom base-64 decoding part, it’s very similar to SWT extraction. I've wrapped the basic SWT and JWT in a ClaimInspector.aspx page on gitHub here: SWT and JWT claim inspector. You can drop it into any ASP.Net site and set the URL to be your redirect page in ACS. Swap ACS to issue SWT or JWT, and using the same page you can inspect the claims that come out.

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• An observation on .NET loops – foreach, for, while, do-while

  It’s very common that .NET programmers use “foreach” loop for iterating through collections. Following is my observation whilst I was testing simple scenario on loops. “for” loop is 30% faster than “foreach” and “while” loop is 50% faster than “foreach”. “do-while” is bit faster than “while”. Someone may feel that how does it make difference if I’m iterating only 1000 times in a loop. This test case is only for simple iteration. According to the "Data structure" concepts, best and worst cases are completely based on the data we provide to the algorithm. so we can not conclude that a "foreach" algorithm is not good. All I want to tell that we need to be little cautious even choosing the loops. Example:- You might want to chose quick sort when you want to sort more numbers. At the same time bubble sort may be effective than quick sort when you want to sort less numbers. Take a simple scenario, a request of a simple web application fetches the data of 10000 (10K) rows and iterating them for some business logic. Think, this application is being accessed by 1000 (1K) people simultaneously. In this simple scenario you are ending up with 10000000 (10Million or 1 Crore) iterations. below is the test scenario with simple console application to test 100 Million records. using System;using System.Collections.Generic;using System.Diagnostics;namespace ConsoleApplication1{ class Program { static void Main(string[] args) { var sw = new Stopwatch(); var numbers = GetSomeNumbers(); sw.Start(); foreach (var item in numbers) { } sw.Stop(); Console.WriteLine( String.Format("\"foreach\" took {0} milliseconds", sw.ElapsedMilliseconds)); sw.Reset(); sw.Start(); for (int i = 0; i < numbers.Count; i++) { } sw.Stop(); Console.WriteLine( String.Format("\"for\" loop took {0} milliseconds", sw.ElapsedMilliseconds)); sw.Reset(); sw.Start(); var it = 0; while (it++ < numbers.Count) { } sw.Stop(); Console.WriteLine( String.Format("\"while\" loop took {0} milliseconds", sw.ElapsedMilliseconds)); sw.Reset(); sw.Start(); var it2 = 0; do { } while (it2++ < numbers.Count); sw.Stop(); Console.WriteLine( String.Format("\"do-while\" loop took {0} milliseconds", sw.ElapsedMilliseconds)); } #region Get me 10Crore (100 Million) numbers private static List<int> GetSomeNumbers() { var lstNumbers = new List<int>(); var count = 100000000; for (var i = 1; i <= count; i++) { lstNumbers.Add(i); } return lstNumbers; } #endregion Get me some numbers }} In above example, I was just iterating through 100 Million numbers. You can see the time to execute various  loops provided in .NET Output "foreach" took 1108 milliseconds "for" loop took 727 milliseconds "while" loop took 596 milliseconds "do-while" loop took 594 milliseconds   Press any key to continue . . . So I feel we need to be careful while choosing the looping strategy. Please comment your thoughts. span.fullpost {display:none;}

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• Asp.net MVC Route class that supports catch-all parameter anywhere in the URL

  - by Robert Koritnik

  the more I think about it the more I believe it's possible to write a custom route that would consume these URL definitions: {var1}/{var2}/{var3} Const/{var1}/{var2} Const1/{var1}/Const2/{var2} {var1}/{var2}/Const as well as having at most one greedy parameter on any position within any of the upper URLs like {*var1}/{var2}/{var3} {var1}/{*var2}/{var3} {var1}/{var2}/{*var3} There is one important constraint. Routes with greedy segment can't have any optional parts. All of them are mandatory. Example This is an exemplary request http://localhost/Show/Topic/SubTopic/SubSubTopic/123/This-is-an-example This is URL route definition {action}/{*topicTree}/{id}/{title} Algorithm Parsing request route inside GetRouteData() should work like this: Split request into segments: Show Topic SubTopic SubSubTopic 123 This-is-an-example Process route URL definition starting from the left and assigning single segment values to parameters (or matching request segment values to static route constant segments). When route segment is defined as greedy, reverse parsing and go to the last segment. Parse route segments one by one backwards (assigning them request values) until you get to the greedy catch-all one again. When you reach the greedy one again, join all remaining request segments (in original order) and assign them to the greedy catch-all route parameter. Questions As far as I can think of this, it could work. But I would like to know: Has anyone already written this so I don't have to (because there are other aspects to parsing as well that I didn't mention (constraints, defaults etc.) Do you see any flaws in this algorithm, because I'm going to have to write it myself if noone has done it so far. I haven't thought about GetVirtuaPath() method at all.

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• Implementing Autocompletion in iPhone UITextField for contacts in address book

  - by nacho4d

  Hi, I would like to have a UITextField or UITextView in where as I do some input, alternatives will appear something similar to when you type an address in Mail Application, alternatives appear down and is possible tap them so get a better input user interface.(since there is no need to type the complete word or address or phone number) I do know how to fetch data from Address Book framework, also how to input text in UITextField/UITextView and its delegates but I don't know what kind of structure to use for fetching and showing data as the user do his/her input. I know basic CoreData if this matters, I hope I can get some help. UPDATE (2010/3/10): I don't have problem make a native-like GUI but I am asking about the algorithm, does any body knows what kind algorithm is best for this thing? maybe some binary tree? Or should I just fetch data from coredata everytime? Thanks Ignacio UPDATE (2010/03/28): I've been very busy these days, so I have not tried UISearchResults but it seems fine to me. BUT I wonder was there a necessity of deletion of the wining answer? I don't think is fair my reputation went down and couldn't see the winning answer. ;(

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• C++ behavior of for loops vs. while loops

  - by kjh

  As far as I understand, when you write a for-loop similar to this one for (int i = 0; i < SOME_NUM; i++) { if (true) do_something(); else do_something_else(); } The time complexity of this operation is mostly affected by the if (true) statement because the for-loop iterations don't actually involve any comparisons of i to SOME_NUM, the compiler will just essentially run the code inside the for-loop SOME_NUM times. Please correct me if I am wrong. However if this is correct, then how do the following nested for-loops behave? for (int i = 0; i < SOME_NUM; i++) { for (int j = 0; j < i; j++) { do_something(); } } The j in the inner for-loop is now upper bound by i, a value that changes every time the loop restarts. How will the compiler compile this? Do these nested for-loops essentially behave like a for-loop with while-loop inside of it? If you're writing an algorithm that uses nested for-loops where the inner counting variable depends on the outer counting variable should you be concerned about what this will do to the complexity of your algorithm?

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• Disco/MapReduce: Using results of previous iteration as input to new iteration

  - by muckabout

  Currently am implementing PageRank on Disco. As an iterative algorithm, the results of one iteration are used as input to the next iteration. I have a large file which represents all the links, with each row representing a page and the values in the row representing the pages to which it links. For Disco, I break this file into N chunks, then run MapReduce for one round. As a result, I get a set of (page, rank) tuples. I'd like to feed this rank to the next iteration. However, now my mapper needs two inputs: the graph file, and the pageranks. I would like to "zip" together the graph file and the page ranks, such that each line represents a page, it's rank, and it's out links. Since this graph file is separated into N chunks, I need to split the pagerank vector into N parallel chunks, and zip the regions of the pagerank vectors to the graph chunks This all seems more complicated than necessary, and as a pretty straightforward operation (with the quintessential mapreduce algorithm), it seems I'm missing something about Disco that could really simplify the approach. Any thoughts?

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• Embedded BI for ASP.NET

  - by Michael Shimmins

  Can anyone recommend a decent business intelligence & reporting application that can be integrated into an OEM application? Primary requirements are: Administrators can define cubes/dimensions etc (or we - the OEM - can predefine some) Report designers can easily inspect data by visually selecting dimensions, filters etc in an adhoc way that is quickly output with little upfront investment Report designers can design a report based on dimensions/filters and save their definition to be run as required Report viewers can view the reports defined by the report designers All of this plus in .NET that can be branded/integrated into our existing web application's look and feel. Permissions need to work off our user/groups system. I've found a few that look good, but they are all in Java and I don't want to ask our clients to install ASP.NET for the app, and then Java, tomcat etc just for reporting. Thanks

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• Get special numbers from a random number generator

  - by Wikeno

  I have a random number generator: int32_t ksp_random_table[GENERATOR_DEG] = { -1726662223, 379960547, 1735697613, 1040273694, 1313901226, 1627687941, -179304937, -2073333483, 1780058412, -1989503057, -615974602, 344556628, 939512070, -1249116260, 1507946756, -812545463, 154635395, 1388815473, -1926676823, 525320961, -1009028674, 968117788, -123449607, 1284210865, 435012392, -2017506339, -911064859, -370259173, 1132637927, 1398500161, -205601318, }; int front_pointer=3, rear_pointer=0; int32_t ksp_rand() { int32_t result; ksp_random_table[ front_pointer ] += ksp_random_table[ rear_pointer ]; result = ( ksp_random_table[ front_pointer ] >> 1 ) & 0x7fffffff; front_pointer++, rear_pointer++; if (front_pointer >= GENERATOR_DEG) front_pointer = 0; if (rear_pointer >= GENERATOR_DEG) rear_pointer = 0; return result; } void ksp_srand(unsigned int seed) { int32_t i, dst=0, kc=GENERATOR_DEG, word, hi, lo; word = ksp_random_table[0] = (seed==0) ? 1 : seed; for (i = 1; i < kc; ++i) { hi = word / 127773, lo = word % 127773; word = 16807 * lo - 2836 * hi; if (word < 0) word += 2147483647; ksp_random_table[++dst] = word; } front_pointer=3, rear_pointer=0; kc *= 10; while (--kc >= 0) ksp_rand(); } I'd like know what type of pseudo random number generation algorithm this is. My guess is a multiple linear congruential generator. And is there a way of seeding this algorithm so that after 987721(1043*947) numbers it would return 15 either even-only, odd-only or alternating odd and even numbers? It is a part of an assignment for a long term competition and i've got no idea how to solve it. I don't want the final solution, I'd like to learn how to do it myself.

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• cleaning up noise in an edge detection algoritum

  - by Faken

  I recently wrote an extremely basic edge detection algorithm that works on an array of chars. The program was meant to detect the edges of blobs of a single particular value on the array and worked by simply looking left, right, up and down on the array element and checking if one of those values is not the same as the value it was currently looking at. The goal was not to produce a mathematical line but rather a set of ordered points that represented a descritized closed loop edge. The algorithm works perfectly fine, except that my data contained a bit of noise hence would randomly produce edges where there should be no edges. This in turn wreaked havoc on some of my other programs down the line. There is two types of noise that the data contains. The first type is fairly sparse and somewhat random. The second type is a semi continuous straight line on the x=y axis. I know the source of the first type of noise, its a feature of the data and there is nothing i can do about it. As for the second type, i know it's my program's fault for causing it...though i haven't a hot clue exactly what is causing it. My question is: How should I go about removing the noise completely? I know that the correct data has points that are always beside each other and is very compact and ordered (with no gaps) and is a closed loop or multiple loops. The first type of noise is usually sparse and random, that could be easily taken care of by checking if any edges is next that noise point is also counted as an edge. If not, then the point is most defiantly noise and should be removed. However, the second type of noise, where we have a semi continuous line about x=y poses more of a problem. The line is sometimes continuous for random lengths (the longest was it went half way across my entire array unbroken). It is even possible for it to intersect the actual edge. Any ideas on how to do this?

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• certificate issues running app in windows 7 ?

  - by Jurjen

  Hi, I'm having some problems with my App. I'm using 'org.mentalis.security' assembly to create a certificate object from a 'pfx' file, this is the line of code where the exception occurs : Certificate cert = Certificate.CreateFromPfxFile(publicKey, certificatePassword); this has always worked and still does in production, but for some reason it throws an exception when run in windows 7 (tried it on 2 machines). CertificateException : Unable to import the PFX file! [error code = -2146893792] I can't find much on this message via google, but when checking the EventViewer I get an 'Audit Failure' every time this exception occurs: Event ID = 5061 Source = Microsoft Windows Security Task Category = system Integrity Keywords = Audit Failure Cryptographic operation. Subject: Security ID: NT AUTHORITY\IUSR Account Name: IUSR Account Domain: NT AUTHORITY Logon ID: 0x3e3 Cryptographic Parameters: Provider Name: Microsoft Software Key Storage Provider Algorithm Name: Not Available. Key Name: VriendelijkeNaam Key Type: User key. Cryptographic Operation: Operation: Open Key. Return Code: 0x2 ` I'm not sure why this isn't working on win 7, I've never had problems when I was running on Vista with this. I am running VS2008 as administrator but I guess that maybe the ASP.NET user doesn't have sufficient rights or something. It's pretty strangs that the 'Algorithm name' is 'Not Available' can anyone help me with this... TIA, Jurjen de Groot

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• Java SAX ContentHandler to create new objects for every root node

  - by behrk2

  Hello everyone, I am using SAX to parse some XML. Let's say I have the following XML document: <queue> <element A> 1 </element A> <element B> 2 </element B> </queue> <queue> <element A> 1 </element A> <element B> 2 </element B> </queue> <queue> <element A> 1 </element A> <element B> 2 </element B> </queue> And I also have an Elements class: public static Elements { String element; public Elements() { } public void setElement(String element){ this.element = element; } public String getElement(){ return element; } } I am looking to write a ContentHandler that follows the following algorithm: Vector v; for every <queue> root node { Element element = new Element(); for every <element> child node{ element.setElement(value of current element); } v.addElement(element); } So, I want to create a bunch of Element objects and add each to a vector...with each Element object containing its own String values (from the child nodes found within the root nodes. I know how to parse out the elements and all of those details, but can someone show me a sample of how to structure my ContentHandler to allow for the above algorithm? Thanks!

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• How do you efficiently implement a document similarity search system?

  - by Björn Lindqvist

  How do you implement a "similar items" system for items described by a set of tags? In my database, I have three tables, Article, ArticleTag and Tag. Each Article is related to a number of Tags via a many-to-many relationship. For each Article i want to find the five most similar articles to implement a "if you like this article you will like these too" system. I am familiar with Cosine similarity and using that algorithm works very well. But it is way to slow. For each article, I need to iterate over all articles, calculate the cosine similarity for the article pair and then select the five articles with the highest similarity rating. With 200k articles and 30k tags, it takes me half a minute to calculate the similar articles for a single article. So I need another algorithm that produces roughly as good results as cosine similarity but that can be run in realtime and which does not require me to iterate over the whole document corpus each time. Maybe someone can suggest an off-the-shelf solution for this? Most of the search engines I looked at does not enable document similarity searching.

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• Writing String to Stream and reading it back does not work

  - by Binary255

  I want to write a String to a Stream (a MemoryStream in this case) and read the bytes one by one. stringAsStream = new MemoryStream(); UnicodeEncoding uniEncoding = new UnicodeEncoding(); String message = "Message"; stringAsStream.Write(uniEncoding.GetBytes(message), 0, message.Length); Console.WriteLine("This:\t\t" + (char)uniEncoding.GetBytes(message)[0]); Console.WriteLine("Differs from:\t" + (char)stringAsStream.ReadByte()); The (undesired) result I get is: This: M Differs from: ? It looks like it's not being read correctly, as the first char of "Message" is 'M', which works when getting the bytes from the UnicodeEncoding instance but not when reading them back from the stream. What am I doing wrong? The bigger picture: I have an algorithm which will work on the bytes of a Stream, I'd like to be as general as possible and work with any Stream. I'd like to convert an ASCII-String into a MemoryStream, or maybe use another method to be able to work on the String as a Stream. The algorithm in question will work on the bytes of the Stream.

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• How Random is System.Guid.NewGuid()? (Take two)

  - by Vilx-

  Before you start marking this as a duplicate, read me out. The other question has a (most likely) incorrect accepted answer. I do not know how .NET generates its GUIDs, probably only Microsoft does, but there's a high chance it simply calls CoCreateGuid(). That function however is documented to be calling UuidCreate(). And the algorithms for creating an UUID are pretty well documented. Long story short, be as it may, it seems that System.Guid.NewGuid() indeed uses version 4 UUID generation algorithm, because all the GUIDs it generates matches the criteria (see for yourself, I tried a couple million GUIDs, they all matched). In other words, these GUIDs are almost random, except for a few known bits. This then again raises the question - how random IS this random? As every good little programmer knows, a pseudo-random number algorithm is only as random as its seed (aka entropy). So what is the seed for UuidCreate()? How ofter is the PRNG re-seeded? Is it cryptographically strong, or can I expect the same GUIDs to start pouring out if two computers accidentally call System.Guid.NewGuid() at the same time? And can the state of the PRNG be guessed if sufficiently many sequentially generated GUIDs are gathered?

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• How can I load file into web app through certain periods?

  - by Elena

  Hi all! I have next task: I need to load the same file into my web app several times, for example - twice a day! Suppose in that file I have information, that changes, and I need to load this info into my app to change the statistics for example. How can I load file several times (twice an hour, or twice a day)? What should I use? Is any algorithm to do that? I am not allowed to use external libraries like Quartz Scheduler. So I need to do it with Thread and/or Timer. Can anybody give me some example or algorithm how to do it. Where can I create the entry point to my Thread, can I do it in managed bean or I need some sort of filter/listener/servlet. I works with jsf and richFaces. Maybe in this technologies there are some algorithms to solve my problem. Any ideas? Thanks very much for help!

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• How should I go about implementing a points-to analysis in Maude?

  - by reprogrammer

  I'm going to implement a points-to analysis algorithm. I'd like to implement this analysis mainly based on the algorithm by Whaley and Lam. Whaley and Lam use a BDD based implementation of Datalog to represent and compute the points-to analysis relations. The following lists some of the relations that are used in a typical points-to analysis. Note that D(w, z) :- A(w, x),B(x, y), C(y, z) means D(w, z) is true if A(w, x), B(x, y), and C(y, z) are all true. BDD is the data structure used to represent these relations. Relations input vP0 (variable : V, heap : H) input store (base : V, field : F, source : V) input load (base : V, field : F, dest : V) input assign (dest : V, source : V) output vP (variable : V, heap : H) output hP (base : H, field : F, target : H) Rules vP(v, h) :- vP0(v, h) vP(v1, h) :- assign(v1, v2), vP(v2, h) hP(h1, f,h2) :- store(v1, f, v2), vP(v1, h1), vP(v2, h2) vP(v2, h2) :- load(v1, f, v2), vP(v1, h1), hP(h1, f, h2) I need to understand if Maude is a good environment for implementing points-to analysis. I noticed that Maude uses a BDD library called BuDDy. But, it looks like that Maude uses BDDs for a different purpose, i.e. unification. So, I thought I might be able to use Maude instead of a Datalog engine to compute the relations of my points-to analysis. I assume Maude propagates independent information concurrently. And this concurrency could potentially make my points-to analysis faster than sequential processing of rules. But, I don't know the best way to represent my relations in Maude. Should I implement BDD in Maude myself, or Maude's internal unification based on BDD has the same effect?

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• Scheme Infix to Postfix

  - by Cody

  Let me establish that this is part of a class assignment, so I'm definitely not looking for a complete code answer. Essentially we need to write a converter in Scheme that takes a list representing a mathematical equation in infix format and then output a list with the equation in postfix format. We've been provided with the algorithm to do so, simple enough. The issue is that there is a restriction against using any of the available imperative language features. I can't figure out how to do this in a purely functional manner. This is our fist introduction to functional programming in my program. I know I'm going to be using recursion to iterate over the list of items in the infix expression like such. (define (itp ifExpr) ( ; do some processing using cond statement (itp (cdr ifExpr)) )) I have all of the processing implemented (at least as best I can without knowing how to do the rest) but the algorithm I'm using to implement this requires that operators be pushed onto a stack and used later. My question is how do I implement a stack in this function that is available to all of the recursive calls as well?

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• Normalizing chains of .Skip() and .Take() calls

  - by dtb

  I'm trying to normalize arbitrary chains of .Skip() and .Take() calls to a single .Skip() call followed by an optional single .Take() call. Here are some examples of expected results, but I'm not sure if these are correct: .Skip(5) => .Skip(5) .Take(7) => .Skip(0).Take(7) .Skip(5).Skip(7) => .Skip(12) .Skip(5).Take(7) => .Skip(5).Take(7) .Take(7).Skip(5) => .Skip(5).Take(2) .Take(5).Take(7) => .Skip(0).Take(5) .Skip(5).Skip(7).Skip(11) => .Skip(23) .Skip(5).Skip(7).Take(11) => .Skip(12).Take(11) .Skip(5).Take(7).Skip(3) => .Skip(8).Take(4) .Skip(5).Take(7).Take(3) => .Skip(5).Take(4) .Take(11).Skip(5).Skip(3) => .Skip(8).Take(3) .Take(11).Skip(5).Take(7) => .Skip(5).Take(6) .Take(11).Take(5).Skip(3) => .Skip(3).Take(2) .Take(11).Take(5).Take(3) => .Skip(0).Take(3) Can anyone confirm these are the correct results to be expected? Here is the basic algorithm that I derived from the examples: class Foo { private int skip; private int? take; public Foo Skip(int value) { if (value < 0) value = 0; this.skip += value; if (this.take.HasValue) this.take -= value; return this; } public Foo Take(int value) { if (value < 0) value = 0; if (!this.take.HasValue || value < this.take) this.take = value; return this; } } Any idea how I can confirm if this is the correct algorithm?

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• C malloc assertion help

  - by Chris

  I am implementing a divide and conquer polynomial algorithm so i can bench it against an opencl implementation, but i can't seem to get malloc to work. When I run the program it allocates a bunch of stuff, checks some things, then sends the size/2 to the algorithm. Then when I hit the malloc line again it spits out this: malloc.c:3096: sYSMALLOc: Assertion `(old_top == (((mbinptr) (((char *) &((av)-bins[((1) - 1) * 2])) - __builtin_offsetof (struct malloc_chunk, fd)))) && old_size == 0) || ((unsigned long) (old_size) = (unsigned long)((((__builtin_offsetof (struct malloc_chunk, fd_nextsize))+((2 * (sizeof(size_t))) - 1)) & ~((2 * (sizeof(size_t))) - 1))) && ((old_top)-size & 0x1) && ((unsigned long)old_end & pagemask) == 0)' failed. Aborted The line in question is: int *out, .....other vars....; out = (int *)malloc(sizeof(int) * size * 2); I have checked size with fprintf and it is a positive int (usually 50 at that point). I have tried calling malloc with a plain number as well and i still get the error. I'm just stumped at what's going on, and nothing from google that I have found so far has been too helpful. Any ideas what's going on? I'm trying to figure out how to compile a newer GCC in case it's a compiler error, but i really doubt it.

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• How to form submit and show a different page in ASP.Net MVC?

  - by melaos

  hi guys i'm new to asp.net mvc.. so basically i just build up a two page app which takes the registration information of the user and post it to the database. i use a lot of jquery and ajax calls to retrieve data from the database using linq to sql stored proc object. and currently i'm stuck at one page where after the user submits the form it should redirect him to /Home/AddProduct. What i found was the error: Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that <machineKey> configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.Web.HttpException: Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that <machineKey> configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster. what used on my form are basically a combination of html controls, asp.net controls and some asp.net mvc type controls. i submit the form using action="/Home/ProductAdded" and after doing some googling i found i was supposed to add in the machine key but after doing so, the index page becomes unviewable. because it couldn't find the index file now. removing the action helps, but now it just doesn't go anywhere. so what am i missing here? i feel i'm missing a lot of fundamentals understanding about asp.net mvc and i don't even know how to submit a form and go to a different page here!!

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• Implementing parts of rfc4226 (HOTP) in mysql

  - by Moose Morals

  Like the title says, I'm trying to implement the programmatic parts of RFC4226 "HOTP: An HMAC-Based One-Time Password Algorithm" in SQL. I think I've got a version that works (in that for a small test sample, it produces the same result as the Java version in the code), but it contains a nested pair of hex(unhex()) calls, which I feel can be done better. I am constrained by a) needing to do this algorithm, and b) needing to do it in mysql, otherwise I'm happy to look at other ways of doing this. What I've got so far: -- From the inside out... -- Concatinate the users secret, and the number of time its been used -- find the SHA1 hash of that string -- Turn a 40 byte hex encoding into a 20 byte binary string -- keep the first 4 bytes -- turn those back into a hex represnetation -- convert that into an integer -- Throw away the most-significant bit (solves signed/unsigned problems) -- Truncate to 6 digits -- store into otp -- from the otpsecrets table select (conv(hex(substr(unhex(sha1(concat(secret, uses))), 1, 4)), 16, 10) & 0x7fffffff) % 1000000 into otp from otpsecrets; Is there a better (more efficient) way of doing this?

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• Using MinHash to find similiarities between 2 images

  - by Sung Meister

  I am using MinHash algorithm to find similar images between images. I have run across this post, How can I recognize slightly modified images? which pointed me to MinHash algorithm. Being a bit mathematically challenged, I was using a C# implementation from this blog post, Set Similarity and Min Hash. But while trying to use the implementation, I have run into 2 problems. What value should I set universe value to? When passing image byte array to HashSet, it only contains distinct byte values; thus comparing values from 1 ~ 256. What is this universe in MinHash? And what can I do to improve the C# MinHash implementation? Since HashSet<byte> contains values upto 256, similarity value always come out to 1. Here is the source that uses the C# MinHash implementation from Set Similarity and Min Hash: class Program { static void Main(string[] args) { var imageSet1 = GetImageByte(@".\Images\01.JPG"); var imageSet2 = GetImageByte(@".\Images\02.TIF"); //var app = new MinHash(256); var app = new MinHash(Math.Min(imageSet1.Count, imageSet2.Count)); double imageSimilarity = app.Similarity(imageSet1, imageSet2); Console.WriteLine("similarity = {0}", imageSimilarity); } private static HashSet<byte> GetImageByte(string imagePath) { using (var fs = new FileStream(imagePath, FileMode.Open, FileAccess.Read)) using (var br = new BinaryReader(fs)) { //List<int> bytes = br.ReadBytes((int)fs.Length).Cast<int>().ToList(); var bytes = new List<byte>(br.ReadBytes((int) fs.Length).ToArray()); return new HashSet<byte>(bytes); } } }

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