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  • Create a fast algorithm for a "weighted" median

    - by Hameer Abbasi
    Suppose we have a set S with k elements of 2-dimensional vectors, (x, n). What would be the most efficient algorithm to calculate the median of the weighted set? By "weighted set", I mean that the number x has a weight n. Here is an example (inefficient due to sorting) algorithm, where Sx is the x-part, and Sn is the n-part. Assume that all co-ordinate pairs are already arranged in Sx, with the respective changes also being done in Sn, and the sum of n is sumN: sum <= 0; i<= 0 while(sum < sumN) sum <= sum + Sn(i) ++i if(sum > sumN/2) return Sx(i) else return (Sx(i)*Sn(i) + Sx(i+1)*Sn(i+1))/(Sn(i) + Sn(i+1)) EDIT: Would this hold in two or more dimensions, if we were to calculate the median first in one dimension, then in another, with n being the sum along that dimension in the second pass?

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  • How can I provide values for non-grouped columns in NHibernate?

    - by ddc0660
    I have a criteria query: Session.CreateCriteria<Sell043Report>() .SetProjection(.ProjectionList() .Add(LambdaProjection.GroupProperty<Sell043Report>(r => r.location)) .Add(LambdaProjection.GroupProperty<Sell043Report>(r => r.agent)) .Add(LambdaProjection.GroupProperty<Sell043Report>(r => r.cusip)) .Add(LambdaProjection.GroupProperty<Sell043Report>(r => r.SettlementDate)) .Add(LambdaProjection.GroupProperty<Sell043Report>(r => r.salePrice)) .Add(LambdaProjection.GroupProperty<Sell043Report>(r => r.foreignFx)) .Add(LambdaProjection.GroupProperty<Sell043Report>(r => r.batchNumber)) .Add(LambdaProjection.GroupProperty<Sell043Report>(r => r.origSaleDate)) .Add(LambdaProjection.GroupProperty<Sell043Report>(r => r.planName)) .Add(LambdaProjection.GroupProperty<Sell043Report>(r => r.dateTimeAdded)) .Add(LambdaProjection.Sum<Sell043Report>(r => r.shares)) .Add(LambdaProjection.Sum<Sell043Report>(r => r.netMoney)) .Add(LambdaProjection.Sum<Sell043Report>(r => r.grossMoney)) .Add(LambdaProjection.Sum<Sell043Report>(r => r.taxWithheld)) .Add(LambdaProjection.Sum<Sell043Report>(r => r.fees))) .List<Sell043Report>(); that generates the following SQL: SELECT this_.location as y0_, this_.agent as y1_, this_.cusip as y2_, this_.SettlementDate as y3_, this_.salePrice as y4_, this_.foreignFx as y5_, this_.batchNumber as y6_, this_.origSaleDate as y7_, this_.planName as y8_, this_.dateTimeAdded as y9_, sum(this_.shares) as y10_, sum(this_.netMoney) as y11_, sum(this_.grossMoney) as y12_, sum(this_.taxWithheld) as y13_, sum(this_.fees) as y14_ FROM MIS_IPS_Sell043Report this_ GROUP BY this_.location, this_.agent, this_.cusip, this_.SettlementDate, this_.salePrice, this_.foreignFx, this_.batchNumber, this_.origSaleDate, this_.planName, this_.dateTimeAdded however the Sell043Report table has additional columns than those listed in the SELECT statement so I'm receiving this error when attempting to get a list of Sell043Reports: System.ArgumentException: The value "System.Object[]" is not of type "xyz.Sell043Report" and cannot be used in this generic collection. I suspect the problem is that I'm not selecting all of the columns for a Sell043Report and so it doesn't know how to map the dataset to the object. I'm trying to achieve something like this: SELECT this_.location as y0_, this_.agent as y1_, this_.cusip as y2_, this_.SettlementDate as y3_, this_.salePrice as y4_, this_.foreignFx as y5_, this_.batchNumber as y6_, this_.origSaleDate as y7_, this_.planName as y8_, this_.dateTimeAdded as y9_, sum(this_.shares) as y10_, sum(this_.netMoney) as y11_, sum(this_.grossMoney) as y12_, sum(this_.taxWithheld) as y13_, sum(this_.fees) as y14_, '' as Address1, '' as Address2 // etc FROM MIS_IPS_Sell043Report this_ GROUP BY this_.location, this_.agent, this_.cusip, this_.SettlementDate, this_.salePrice, this_.foreignFx, this_.batchNumber, this_.origSaleDate, this_.planName, this_.dateTimeAdded How can I do this using NHibernate?

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  • Visually and audibly unambiguous subset of the Latin alphabet?

    - by elliot42
    Imagine you give someone a card with the code "5SBDO0" on it. In some fonts, the letter "S" is difficult to visually distinguish from the number five, (as with number zero and letter "O"). Reading the code out loud, it might be difficult to distinguish "B" from "D", necessitating saying "B as in boy," "D as in dog," or using a "phonetic alphabet" instead. What's the biggest subset of letters and numbers that will, in most cases, both look unambiguous visually and sound unambiguous when read aloud? Background: We want to generate a short string that can encode as many values as possible while still being easy to communicate. Imagine you have a 6-character string, "123456". In base 10 this can encode 10^6 values. In hex "1B23DF" you can encode 16^6 values in the same number of characters, but this can sound ambiguous when read aloud. ("B" vs. "D") Likewise for any string of N characters, you get (size of alphabet)^N values. The string is limited to a length of about six characters, due to wanting to fit easily within the capacity of human working memory capacity. Thus to find the max number of values we can encode, we need to find that largest unambiguous set of letters/numbers. There's no reason we can't consider the letters G-Z, and some common punctuation, but I don't want to have to go manually pairwise compare "does G sound like A?", "does G sound like B?", "does G sound like C" myself. As we know this would be O(n^2) linguistic work to do =)...

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  • Cant install software

    - by user53209
    So I just installed the ubuntu 11.10 .. And when i goto software center and try to download any software(use source).. all i get is a window saying that "Failed to download repository information" , "check your internet connection" and W:Failed to fetch bzip2:/var/lib/apt/lists/partial/archive.ubuntu.com_ubuntu_dists_oneiric_restricted_binary-i386_Packages Hash Sum mismatch , W:Failed to fetch bzip2:/var/lib/apt/lists/partial/archive.ubuntu.com_ubuntu_dists_oneiric_universe_binary-i386_Packages Hash Sum mismatch , W:Failed to fetch bzip2:/var/lib/apt/lists/partial/archive.ubuntu.com_ubuntu_dists_oneiric_multiverse_binary-i386_Packages Hash Sum mismatch , W:Failed to fetch htt p ://archive.ubuntu.com/ubuntu/dists/oneiric/main/i18n/Index No Hash entry in Release file /var/lib/apt/lists/partial/archive.ubuntu.com_ubuntu_dists_oneiric_main_i18n_Index , W:Failed to fetch http ://archive.ubuntu.com/ubuntu/dists/oneiric/multiverse/i18n/Index No Hash entry in Release file /var/lib/apt/lists/partial/archive.ubuntu.com_ubuntu_dists_oneiric_multiverse_i18n_Index , W:Failed to fetch htt ://archive.ubuntu.com/ubuntu/dists/oneiric/restricted/i18n/Index No Hash entry in Release file /var/lib/apt/lists/partial/archive.ubuntu.com_ubuntu_dists_oneiric_restricted_i18n_Index , W:Failed to fetch ht tp://archive.ubuntu.com/ubuntu/dists/oneiric/universe/i18n/Index No Hash entry in Release file /var/lib/apt/lists/partial/archive.ubuntu.com_ubuntu_dists_oneiric_universe_i18n_Index , W:Failed to fetch bzip2:/var/lib/apt/lists/partial/archive.ubuntu.com_ubuntu_dists_oneiric-updates_main_source_Sources Hash Sum mismatch , W:Failed to fetch bzip2:/var/lib/apt/lists/partial/archive.ubuntu.com_ubuntu_dists_oneiric-updates_restricted_binary-i386_Packages Hash Sum mismatch , W:Failed to fetch bzip2:/var/lib/apt/lists/partial/archive.ubuntu.com_ubuntu_dists_oneiric-updates_universe_binary-i386_Packages Hash Sum mismatch , W:Failed to fetch bzip2:/var/lib/apt/lists/partial/archive.ubuntu.com_ubuntu_dists_oneiric-updates_multiverse_binary-i386_Packages Hash Sum mismatch , W:Failed to fetch h tp://archive.ubuntu.com/ubuntu/dists/oneiric-updates/main/i18n/Index No Hash entry in Release file /var/lib/apt/lists/partial/archive.ubuntu.com_ubuntu_dists_oneiric-updates_main_i18n_Index , W:Failed to fetch h ttp://archive.ubuntu.com/ubuntu/dists/oneiric-updates/multiverse/i18n/Index No Hash entry in Release file /var/lib/apt/lists/partial/archive.ubuntu.com_ubuntu_dists_oneiric-updates_multiverse_i18n_Index , W:Failed to fetch ht tp://archive.ubuntu.com/ubuntu/dists/oneiric-updates/restricted/i18n/Index No Hash entry in Release file /var/lib/apt/lists/partial/archive.ubuntu.com_ubuntu_dists_oneiric-updates_restricted_i18n_Index , W:Failed to fetch htt p://archive.ubuntu.com/ubuntu/dists/oneiric-updates/universe/i18n/Index No Hash entry in Release file /var/lib/apt/lists/partial/archive.ubuntu.com_ubuntu_dists_oneiric-updates_universe_i18n_Index , W:Failed to fetch bzip2:/var/lib/apt/lists/partial/archive.ubuntu.com_ubuntu_dists_oneiric-backports_main_source_Sources Hash Sum mismatch , W:Failed to fetch bzip2:/var/lib/apt/lists/partial/archive.ubuntu.com_ubuntu_dists_oneiric-backports_restricted_binary-i386_Packages Hash Sum mismatch , W:Failed to fetch bzip2:/var/lib/apt/lists/partial/archive.ubuntu.com_ubuntu_dists_oneiric-backports_universe_binary-i386_Packages Hash Sum mismatch , W:Failed to fetch bzip2:/var/lib/apt/lists/partial/archive.ubuntu.com_ubuntu_dists_oneiric-backports_multiverse_binary-i386_Packages Hash Sum mismatch , W:Failed to fetch h ttp://archive.ubuntu.com/ubuntu/dists/oneiric-backports/main/i18n/Index No Hash entry in Release file /var/lib/apt/lists/partial/archive.ubuntu.com_ubuntu_dists_oneiric-backports_main_i18n_Index , W:Failed to fetch h ttp://archive.ubuntu.com/ubuntu/dists/oneiric-backports/multiverse/i18n/Index No Hash entry in Release file /var/lib/apt/lists/partial/archive.ubuntu.com_ubuntu_dists_oneiric-backports_multiverse_i18n_Index , W:Failed to fetch ht tp://archive.ubuntu.com/ubuntu/dists/oneiric-backports/restricted/i18n/Index No Hash entry in Release file /var/lib/apt/lists/partial/archive.ubuntu.com_ubuntu_dists_oneiric-backports_restricted_i18n_Index , W:Failed to fetch ht tp://archive.ubuntu.com/ubuntu/dists/oneiric-backports/universe/i18n/Index No Hash entry in Release file /var/lib/apt/lists/partial/archive.ubuntu.com_ubuntu_dists_oneiric-backports_universe_i18n_Index , W:Failed to fetch bzip2:/var/lib/apt/lists/partial/archive.ubuntu.com_ubuntu_dists_oneiric-security_main_source_Sources Hash Sum mismatch , E:Some index files failed to download. They have been ignored, or old ones used instead." Neglect the http typos, its to evade the 2 hyperlink.. I tried making a file in the apt.conf.d folder also, and added proxy entries, also set the system proxy.. and also the "network proxy", but nothing works.. And now I cant install any software!! Help needed

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  • How can I sum number of rows of a table in SQL ORACLE?

    - by Christian Magro
    Dear community I have the follow instruction on SQL ORACLE: SELECT COUNT(FE_DAY) FROM TI_DATE WHERE (FE_MO = 02 AND FE_YEAR in ('2011', '2012')) GROUP BY FE_DAY In this instruction effectively obtain like SQL Answer a list of number that they sum=10 .But How can I don't show rows .I need only show the row's sum=10 I tried to apply the follow SQL instruction also: SELECT SUM(COUNT(FE_DAY)) FROM TI_DATE WHERE (FE_MO = 02 AND FE_YEAR in ('2011', '2012')) GROUP BY FE_DAY But the answer was 57, different of the number of rows, that I need.

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  • How to make a SUM of Dictionary Value nested into a list with LINQ ?

    - by user551108
    Hi All, I have a product object declared as : Product { int ProductID; string ProductName; int ProductTypeID; string ProductTypeName; int UnitsSold Dictionary <string, int> UnitsSoldByYear; } I want to make a sum on UnitsSold and UnitsSoldByYear properties with a Linq query but I didn't know how to make this kind of sum on a dictionary ! Here is my begining linq query code : var ProductTypeSum = from i in ProductsList group i by new { i.ProductTypeID, i.ProductTypeName} into pt select new { ProductTypeID= pt.Key.ProductTypeID, ProductTypeName= pt.Key.ProductTypeName, UnitsSoldSum= pt.Sum(i => i.UnitsSold), // How to make a Dictionary sum here } Thank you for your help !

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  • Finding k elements of length-n list that sum to less than t in O(nlogk) time

    - by tresbot
    This is from Programming Pearls ed. 2, Column 2, Problem 8: Given a set of n real numbers, a real number t, and an integer k, how quickly can you determine whether there exists a k-element subset of the set that sums to at most t? One easy solution is to sort and sum the first k elements, which is our best hope to find such a sum. However, in the solutions section Bentley alludes to a solution that takes nlog(k) time, though he gives no hints for how to find it. I've been struggling with this; one thought I had was to go through the list and add all the elements less than t/k (in O(n) time); say there are m1 < k such elements, and they sum to s1 < t. Then we are left needing k - m1 elements, so we can scan through the list again in O(n) time looking for all elements less than (t - s1)/(k - m1). Add in again, to get s2 and m2, then again if m2 < k, look for all elements less than (t - s2)/(k - m2). So: def kSubsetSumUnderT(inList, k, t): outList = [] s = 0 m = 0 while len(outList) < k: toJoin = [i for i in inList where i < (t - s)/(k - m)] if len(toJoin): if len(toJoin) >= k - m: toJoin.sort() if(s0 + sum(toJoin[0:(k - m - 1)]) < t: return True return False outList = outList + toJoin s += sum(toJoin) m += len(toJoin) else: return False My intuition is that this might be the O(nlog(k)) algorithm, but I am having a hard time proving it to myself. Thoughts?

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  • How do I sync a subset of tables between two databases on the same mysql database server

    - by Mike
    would like to be able to sync a subset of tables between two mysql databases that are running on the same server. One of the databases acts as the master where inserts, updates and deletes can be made. The second database uses those same tables for read-only operations. I do not want to use federated tables to achieve this. The long term goal will be to separate the 2 databases to multiple servers, The second database that has the subset of tables as read-only may also be replicated a few times over to distribute geographically for load and performance purposes each with unqiue data.... Once that is achieved, I plan to use binlog to replicate those specific tables on the secondary databases. In the meantime, I'd like to keep these tables in sync. Is there a more elegant way to do this than other than using a cronjob and mysqldump?

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  • Sum if ONLY all the cells have a value?

    - by Mike
    Hi I need to sum 9 cells of data, each one on a separate sheet, but always in the same location. I only want a figure returned when all the cells have data, even if it's a 0. But, if one of the cells is blank I want a blank return. I'm trying to get my head around, making it up actually, where the IFs and ISBLANK and SUMS would go. Any pointers would be greatly appreciated. SUM(IF(ISBLANK(RANGEA,OR(RANGEB),0,ALLRANGES))) Many thanks Michael

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  • the error "invalid literal for int() with base 10:" keeps coming up

    - by ratce003
    I'm trying to write a very simple program, I want to print out the sum of all the multiples of 3 and 5 below 100, but, an error keeps accuring, saying "invalid literal for int() with base 10:" my program is as follows: sum = "" sum_int = int(sum) for i in range(1, 101): if i % 5 == 0: sum += i elif i % 3 == 0: sum += i else: sum += "" print sum Any help would be much appreciated.

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  • Converting a C++ Checksum function to Java

    - by user1897599
    I'm trying to convert this C++ checksum to Java but for the time being I've failed. What am I doing wrong? What is it supposed to do? It is supposed to return a positive checksum for a buffer in OpenGL Here's the C part. DWORD QuickChecksum(DWORD *data, int size){ if(!data) { return 0x0; } DWORD sum; DWORD tmp; sum = *data; for(int i = 1; i < (size/4); i++) { tmp = data[i]; tmp = (DWORD)(sum >> 29) + tmp; tmp = (DWORD)(sum >> 17) + tmp; sum = (DWORD)(sum << 3) ^ tmp; } return sum; } And here is what I have tried in Java. As far As I know DWORD is 32bit so I use int in a long to get a unsigned int which should be done in java with ? I've been looking at this problem so much now that I've grown blind to it. public static long getChecksum(byte[] data, int size) { long sum, tmp; sum = getInt(new byte[]{data[0], data[1], data[2], data[3]},true) & 0xFF; for(int I = 4; I < data.length; I += 4) { tmp = getInt(new byte[]{data[I],data[I+1],data[I+2],data[I+3]},true) & 0xFF; tmp = (sum >>> 29) + tmp; tmp = (sum >>> 17) + tmp; sum = (sum << 3) ^ tmp; } return sum & 0xFF; } private static int getInt(byte[] bytes, boolean big) { ByteBuffer bb = ByteBuffer.wrap(bytes); return bb.getInt(); } Thank you all for your help!

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  • How to: Check which table is the biggest, in SQL Server

    - by AngelEyes
    The company I work with had it's DB double its size lately, so I needed to find out which tables were the biggest. I found this on the web, and decided it's worth remembering! Taken from http://www.sqlteam.com/article/finding-the-biggest-tables-in-a-database, the code is from http://www.sqlteam.com/downloads/BigTables.sql   /************************************************************************************** * *  BigTables.sql *  Bill Graziano (SQLTeam.com) *  [email protected] *  v1.1 * **************************************************************************************/ DECLARE @id INT DECLARE @type CHARACTER(2) DECLARE @pages INT DECLARE @dbname SYSNAME DECLARE @dbsize DEC(15, 0) DECLARE @bytesperpage DEC(15, 0) DECLARE @pagesperMB DEC(15, 0) CREATE TABLE #spt_space   (      objid    INT NULL,      ROWS     INT NULL,      reserved DEC(15) NULL,      data     DEC(15) NULL,      indexp   DEC(15) NULL,      unused   DEC(15) NULL   ) SET nocount ON -- Create a cursor to loop through the user tables DECLARE c_tables CURSOR FOR   SELECT id   FROM   sysobjects   WHERE  xtype = 'U' OPEN c_tables FETCH NEXT FROM c_tables INTO @id WHILE @@FETCH_STATUS = 0   BEGIN       /* Code from sp_spaceused */       INSERT INTO #spt_space                   (objid,                    reserved)       SELECT objid = @id,              SUM(reserved)       FROM   sysindexes       WHERE  indid IN ( 0, 1, 255 )              AND id = @id       SELECT @pages = SUM(dpages)       FROM   sysindexes       WHERE  indid < 2              AND id = @id       SELECT @pages = @pages + Isnull(SUM(used), 0)       FROM   sysindexes       WHERE  indid = 255              AND id = @id       UPDATE #spt_space       SET    data = @pages       WHERE  objid = @id       /* index: sum(used) where indid in (0, 1, 255) - data */       UPDATE #spt_space       SET    indexp = (SELECT SUM(used)                        FROM   sysindexes                        WHERE  indid IN ( 0, 1, 255 )                               AND id = @id) - data       WHERE  objid = @id       /* unused: sum(reserved) - sum(used) where indid in (0, 1, 255) */       UPDATE #spt_space       SET    unused = reserved - (SELECT SUM(used)                                   FROM   sysindexes                                   WHERE  indid IN ( 0, 1, 255 )                                          AND id = @id)       WHERE  objid = @id       UPDATE #spt_space       SET    ROWS = i.ROWS       FROM   sysindexes i       WHERE  i.indid < 2              AND i.id = @id              AND objid = @id       FETCH NEXT FROM c_tables INTO @id   END SELECT TOP 25 table_name = (SELECT LEFT(name, 25)                             FROM   sysobjects                             WHERE  id = objid),               ROWS = CONVERT(CHAR(11), ROWS),               reserved_kb = Ltrim(Str(reserved * d.low / 1024., 15, 0) + ' ' + 'KB'),               data_kb = Ltrim(Str(data * d.low / 1024., 15, 0) + ' ' + 'KB'),               index_size_kb = Ltrim(Str(indexp * d.low / 1024., 15, 0) + ' ' + 'KB'),               unused_kb = Ltrim(Str(unused * d.low / 1024., 15, 0) + ' ' + 'KB') FROM   #spt_space,        MASTER.dbo.spt_values d WHERE  d.NUMBER = 1        AND d.TYPE = 'E' ORDER  BY reserved DESC DROP TABLE #spt_space CLOSE c_tables DEALLOCATE c_tables

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  • Windows Server task manager displays much higher memory use than sum of all processes' working set s

    - by Sleepless
    I have a 16 GB Windows Server 2008 x64 machine mostly running SQL Server 2008. The free memory as seen in Task Manager is very low (128 MB at the moment), i.e. about 15.7 GB are used. So far, so good. Now when I try to narrow down the process(es) using the most memory I get confused: None of the processes have more than 200MB Working Set Size as displayed in the 'Processes' tab of Task Manager. Well, maybe the Working Set Size isn't the relevant counter? To figure that out I used a PowerShell command [1] to sum up each individual property of the process object in sort of a brute force approach - surely one of them must add up to the 15.7 GB, right? Turns out none of them does, with the closest being VirtualMemorySize (around 12.7 GB) and PeakVirtualMemorySize (around 14.7 GB). WTF? To put it another way: Which of the numerous memory related process information is the "correct" one, i.e. counts towards the server's physical memory as displayed in the Task Manager's 'Performance' tab? Thank you all! [1] $erroractionpreference="silentlycontinue"; get-process | gm | where-object {$.membertype -eq "Property"} | foreach-object {$.name; (get-process | measure-object -sum $_.name ).sum / 1MB}

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  • Normal map lighting bug in bottom right quadrant

    - by Ryan Capote
    I am currently working on getting normal maps working in my project, and have run into a problem with lighting. As you can see, the normals in the bottom right quadrant of the lighting isn't calculating the correct direction to the light or something. Best seen by the red light If I use flat normals (z normal = 1.0), it seems to be working fine: normals for the tile sheet: Shader: #version 330 uniform sampler2D uDiffuseTexture; uniform sampler2D uNormalsTexture; uniform sampler2D uSpecularTexture; uniform sampler2D uEmissiveTexture; uniform sampler2D uWorldNormals; uniform sampler2D uShadowMap; uniform vec4 uLightColor; uniform float uConstAtten; uniform float uLinearAtten; uniform float uQuadradicAtten; uniform float uColorIntensity; in vec2 TexCoords; in vec2 GeomSize; out vec4 FragColor; float sample(vec2 coord, float r) { return step(r, texture2D(uShadowMap, coord).r); } float occluded() { float PI = 3.14; vec2 normalized = TexCoords.st * 2.0 - 1.0; float theta = atan(normalized.y, normalized.x); float r = length(normalized); float coord = (theta + PI) / (2.0 * PI); vec2 tc = vec2(coord, 0.0); float center = sample(tc, r); float sum = 0.0; float blur = (1.0 / GeomSize.x) * smoothstep(0.0, 1.0, r); sum += sample(vec2(tc.x - 4.0*blur, tc.y), r) * 0.05; sum += sample(vec2(tc.x - 3.0*blur, tc.y), r) * 0.09; sum += sample(vec2(tc.x - 2.0*blur, tc.y), r) * 0.12; sum += sample(vec2(tc.x - 1.0*blur, tc.y), r) * 0.15; sum += center * 0.16; sum += sample(vec2(tc.x + 1.0*blur, tc.y), r) * 0.15; sum += sample(vec2(tc.x + 2.0*blur, tc.y), r) * 0.12; sum += sample(vec2(tc.x + 3.0*blur, tc.y), r) * 0.09; sum += sample(vec2(tc.x + 4.0*blur, tc.y), r) * 0.05; return sum * smoothstep(1.0, 0.0, r); } float calcAttenuation(float distance) { float linearAtten = uLinearAtten * distance; float quadAtten = uQuadradicAtten * distance * distance; float attenuation = 1.0 / (uConstAtten + linearAtten + quadAtten); return attenuation; } vec3 calcFragPosition(void) { return vec3(TexCoords*GeomSize, 0.0); } vec3 calcLightPosition(void) { return vec3(GeomSize/2.0, 0.0); } float calcDistance(vec3 fragPos, vec3 lightPos) { return length(fragPos - lightPos); } vec3 calcLightDirection(vec3 fragPos, vec3 lightPos) { return normalize(lightPos - fragPos); } vec4 calcFinalLight(vec2 worldUV, vec3 lightDir, float attenuation) { float diffuseFactor = dot(normalize(texture2D(uNormalsTexture, worldUV).rgb), lightDir); vec4 diffuse = vec4(0.0); vec4 lightColor = uLightColor * uColorIntensity; if(diffuseFactor > 0.0) { diffuse = vec4(texture2D(uDiffuseTexture, worldUV.xy).rgb, 1.0); diffuse *= diffuseFactor; lightColor *= diffuseFactor; } else { discard; } vec4 final = (diffuse + lightColor); if(texture2D(uWorldNormals, worldUV).g > 0.0) { return final * attenuation; } else { return final * occluded(); } } void main(void) { vec3 fragPosition = calcFragPosition(); vec3 lightPosition = calcLightPosition(); float distance = calcDistance(fragPosition, lightPosition); float attenuation = calcAttenuation(distance); vec2 worldPos = gl_FragCoord.xy / vec2(1024, 768); vec3 lightDir = calcLightDirection(fragPosition, lightPosition); lightDir = (lightDir*0.5)+0.5; float atten = calcAttenuation(distance); vec4 emissive = texture2D(uEmissiveTexture, worldPos); FragColor = calcFinalLight(worldPos, lightDir, atten) + emissive; }

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  • Improving SQL Code

    - by jeremib
    I'm using Pervasive SQL. I have the following UNION of mulitple SQL statements. Is there a way to clean this up, especially the Pay Date an the Loc No fields that are selected in each statement. Is there a way to pull this out and have only one place to need to change those two fields? ( SELECT '23400' as Gl_Number, y.Plan as Description, 0 as Hours, ROUND(SUM(Ee_Curr),2) as Debit, 0 as Credit FROM "PR_YLOC" y LEFT JOIN PR_SUMM s ON (s.Summ_No = y.Summ_No) WHERE y.Loc_No = 1041 AND s.Pay_Date = '2010-04-02' AND y.Code IN (100, 105, 110) AND y.Type = 3 GROUP BY y.Plan ) UNION ( SELECT '72000' as Gl_Number, y.Plan, 0, ROUND(SUM(Er_Curr),2), 0 FROM "PR_YLOC" y LEFT JOIN PR_SUMM s ON (s.Summ_No = y.Summ_No) WHERE y.Loc_No = 1041 AND s.Pay_Date = '2010-04-02' AND y.Code IN (100, 105, 110) AND y.Type = 3 GROUP BY y.Plan ) UNION ( SELECT '24800', c.Plan, 0, ROUND(SUM(Ee_Amt),2), 0 FROM "PR_CDED" c WHERE Pay_Date = '2010-04-02' AND Loc_No = 1041 AND Code = 100 GROUP BY c.Plan ) UNION ( SELECT '24800', c.Plan, 0, 0, ROUND(SUM(Ee_Amt),2) FROM "PR_CDED" c WHERE Pay_Date = '2010-04-02' AND Loc_No = 1041 AND Code = 115 GROUP BY c.Plan ) UNION ( SELECT '24150', c.Plan, 0, 0, ROUND(SUM(Ee_Amt),2) FROM "PR_CDED" c WHERE Pay_Date = '2010-04-02' AND Loc_No = 1041 AND Code = 241 GROUP BY c.Plan ) UNION ( SELECT '24150', c.Plan, 0, ROUND(SUM(Ee_Amt),2), 0 FROM "PR_CDED" c WHERE Pay_Date = '2010-04-02' AND Loc_No = 1041 AND Code = 239 GROUP BY c.Plan ) UNION ( SELECT '24120', c.Plan, 0, ROUND(SUM(Ee_Amt),2), 0 FROM "PR_CDED" c WHERE Pay_Date = '2010-04-02' AND Loc_No = 1041 AND Code = 230 GROUP BY c.Plan ) UNION ( SELECT '24100', c.Plan, 0, ROUND(SUM(Ee_Amt),2), 0 FROM "PR_CDED" c WHERE Pay_Date = '2010-04-02' AND Loc_No = 1041 AND Code = 225 GROUP BY c.Plan ) UNION ( SELECT '23800', c.Plan, 0, ROUND(SUM(Ee_Amt),2), 0 FROM "PR_CDED" c WHERE Pay_Date = '2010-04-02' AND Loc_No = 1041 AND Code = 245 GROUP BY c.Plan ) UNION ( select m.Def_Dept as Gl_Number, t.Short_Desc, (SELECT SUM(Hours) FROM pr_earn en WHERE en.Loc_No = e.Loc_No AND en.Emp_No = e.Emp_No AND en.Pay_Date = e.Pay_Date AND en.Pay_Code = e.Pay_Code) as Hours, (SELECT SUM(Pay_Amt) FROM pr_earn en WHERE en.Loc_No = e.Loc_No AND en.Emp_No = e.Emp_No AND en.Pay_Date = e.Pay_Date AND en.Pay_Code = e.Pay_Code) as Debit, 0 from pr_earn e left join pr_mast m on (e.Loc_No = m.Loc_No and e.Emp_No = m.Emp_No) left join pr_ptype t ON (t.Code = e.Pay_Code) where e.loc_no = 1041 and e.pay_date = '2010-04-02' group by m.Def_Dept, t.Short_Desc ) Thanks

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  • Optimal two variable linear regression SQL statement (censoring outliers)

    - by Dave Jarvis
    Problem Am looking to apply the y = mx + b equation (where m is SLOPE, b is INTERCEPT) to a data set, which is retrieved as shown in the SQL code. The values from the (MySQL) query are: SLOPE = 0.0276653965651912 INTERCEPT = -57.2338357550468 SQL Code SELECT ((sum(t.YEAR) * sum(t.AMOUNT)) - (count(1) * sum(t.YEAR * t.AMOUNT))) / (power(sum(t.YEAR), 2) - count(1) * sum(power(t.YEAR, 2))) as SLOPE, ((sum( t.YEAR ) * sum( t.YEAR * t.AMOUNT )) - (sum( t.AMOUNT ) * sum(power(t.YEAR, 2)))) / (power(sum(t.YEAR), 2) - count(1) * sum(power(t.YEAR, 2))) as INTERCEPT FROM (SELECT D.AMOUNT, Y.YEAR FROM CITY C, STATION S, YEAR_REF Y, MONTH_REF M, DAILY D WHERE -- For a specific city ... -- C.ID = 8590 AND -- Find all the stations within a 15 unit radius ... -- SQRT( POW( C.LATITUDE - S.LATITUDE, 2 ) + POW( C.LONGITUDE - S.LONGITUDE, 2 ) ) <15 AND -- Gather all known years for that station ... -- S.STATION_DISTRICT_ID = Y.STATION_DISTRICT_ID AND -- The data before 1900 is shaky; insufficient after 2009. -- Y.YEAR BETWEEN 1900 AND 2009 AND -- Filtered by all known months ... -- M.YEAR_REF_ID = Y.ID AND -- Whittled down by category ... -- M.CATEGORY_ID = '001' AND -- Into the valid daily climate data. -- M.ID = D.MONTH_REF_ID AND D.DAILY_FLAG_ID <> 'M' GROUP BY Y.YEAR ORDER BY Y.YEAR ) t Data The data is visualized here (with five outliers highlighted): Questions How do I return the y value against all rows without repeating the same query to collect and collate the data? That is, how do I "reuse" the list of t values? How would you change the query to eliminate outliers (at an 85% confidence interval)? The following results (to calculate the start and end points of the line) appear incorrect. Why are the results off by ~10 degrees (e.g., outliers skewing the data)? (1900 * 0.0276653965651912) + (-57.2338357550468) = -4.66958228 (2009 * 0.0276653965651912) + (-57.2338357550468) = -1.65405406 I would have expected the 1900 result to be around 10 (not -4.67) and the 2009 result to be around 11.50 (not -1.65). Thank you!

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  • Optimal two variable linear regression SQL statement

    - by Dave Jarvis
    Problem Am looking to apply the y = mx + b equation (where m is SLOPE, b is INTERCEPT) to a data set, which is retrieved as shown in the SQL code. The values from the (MySQL) query are: SLOPE = 0.0276653965651912 INTERCEPT = -57.2338357550468 SQL Code SELECT ((sum(t.YEAR) * sum(t.AMOUNT)) - (count(1) * sum(t.YEAR * t.AMOUNT))) / (power(sum(t.YEAR), 2) - count(1) * sum(power(t.YEAR, 2))) as SLOPE, ((sum( t.YEAR ) * sum( t.YEAR * t.AMOUNT )) - (sum( t.AMOUNT ) * sum(power(t.YEAR, 2)))) / (power(sum(t.YEAR), 2) - count(1) * sum(power(t.YEAR, 2))) as INTERCEPT FROM (SELECT D.AMOUNT, Y.YEAR FROM CITY C, STATION S, YEAR_REF Y, MONTH_REF M, DAILY D WHERE -- For a specific city ... -- C.ID = 8590 AND -- Find all the stations within a 5 unit radius ... -- SQRT( POW( C.LATITUDE - S.LATITUDE, 2 ) + POW( C.LONGITUDE - S.LONGITUDE, 2 ) ) <15 AND -- Gather all known years for that station ... -- S.STATION_DISTRICT_ID = Y.STATION_DISTRICT_ID AND -- The data before 1900 is shaky; and insufficient after 2009. -- Y.YEAR BETWEEN 1900 AND 2009 AND -- Filtered by all known months ... -- M.YEAR_REF_ID = Y.ID AND -- Whittled down by category ... -- M.CATEGORY_ID = '001' AND -- Into the valid daily climate data. -- M.ID = D.MONTH_REF_ID AND D.DAILY_FLAG_ID <> 'M' GROUP BY Y.YEAR ORDER BY Y.YEAR ) t Data The data is visualized here: Questions How do I return the y value against all rows without repeating the same query to collect and collate the data? That is, how do I "reuse" the list of t values? How would you change the query to eliminate outliers (at an 85% confidence interval)? The following results (to calculate the start and end points of the line) appear incorrect. Why are the results off by ~10 degrees (e.g., outliers skewing the data)? (1900 * 0.0276653965651912) + (-57.2338357550468) = -4.66958228 (2009 * 0.0276653965651912) + (-57.2338357550468) = -1.65405406 I would have expected the 1900 result to be around 10 (not -4.67) and the 2009 result to be around 11.50 (not -1.65). Thank you!

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  • Optimal two variable linear regression calculation

    - by Dave Jarvis
    Problem Am looking to apply the y = mx + b equation (where m is SLOPE, b is INTERCEPT) to a data set, which is retrieved as shown in the SQL code. The values from the (MySQL) query are: SLOPE = 0.0276653965651912 INTERCEPT = -57.2338357550468 SQL Code SELECT ((sum(t.YEAR) * sum(t.AMOUNT)) - (count(1) * sum(t.YEAR * t.AMOUNT))) / (power(sum(t.YEAR), 2) - count(1) * sum(power(t.YEAR, 2))) as SLOPE, ((sum( t.YEAR ) * sum( t.YEAR * t.AMOUNT )) - (sum( t.AMOUNT ) * sum(power(t.YEAR, 2)))) / (power(sum(t.YEAR), 2) - count(1) * sum(power(t.YEAR, 2))) as INTERCEPT, FROM (SELECT D.AMOUNT, Y.YEAR FROM CITY C, STATION S, YEAR_REF Y, MONTH_REF M, DAILY D WHERE -- For a specific city ... -- C.ID = 8590 AND -- Find all the stations within a 15 unit radius ... -- SQRT( POW( C.LATITUDE - S.LATITUDE, 2 ) + POW( C.LONGITUDE - S.LONGITUDE, 2 ) ) < 15 AND -- Gather all known years for that station ... -- S.STATION_DISTRICT_ID = Y.STATION_DISTRICT_ID AND -- The data before 1900 is shaky; insufficient after 2009. -- Y.YEAR BETWEEN 1900 AND 2009 AND -- Filtered by all known months ... -- M.YEAR_REF_ID = Y.ID AND -- Whittled down by category ... -- M.CATEGORY_ID = '001' AND -- Into the valid daily climate data. -- M.ID = D.MONTH_REF_ID AND D.DAILY_FLAG_ID <> 'M' GROUP BY Y.YEAR ORDER BY Y.YEAR ) t Data The data is visualized here: Question The following results (to calculate the start and end points of the line) appear incorrect. Why are the results off by ~10 degrees (e.g., outliers skewing the data)? (1900 * 0.0276653965651912) + (-57.2338357550468) = -4.66958228 (2009 * 0.0276653965651912) + (-57.2338357550468) = -1.65405406 I would have expected the 1900 result to be around 10 (not -4.67) and the 2009 result to be around 11.50 (not -1.65). Related Sites Least absolute deviations Robust regression Thank you!

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  • Remove redundant SQL code

    - by Dave Jarvis
    Code The following code calculates the slope and intercept for a linear regression against a slathering of data. It then applies the equation y = mx + b against the same result set to calculate the value of the regression line for each row. Can the two separate sub-selects be joined so that the data and its slope/intercept are calculated without executing the data gathering part of the query twice? SELECT AVG(D.AMOUNT) as AMOUNT, Y.YEAR * ymxb.SLOPE + ymxb.INTERCEPT as REGRESSION_LINE, Y.YEAR as YEAR, MAKEDATE(Y.YEAR,1) as AMOUNT_DATE FROM CITY C, STATION S, YEAR_REF Y, MONTH_REF M, DAILY D, (SELECT ((avg(t.AMOUNT * t.YEAR)) - avg(t.AMOUNT) * avg(t.YEAR)) / (stddev( t.AMOUNT ) * stddev( t.YEAR )) as CORRELATION, ((sum(t.YEAR) * sum(t.AMOUNT)) - (count(1) * sum(t.YEAR * t.AMOUNT))) / (power(sum(t.YEAR), 2) - count(1) * sum(power(t.YEAR, 2))) as SLOPE, ((sum( t.YEAR ) * sum( t.YEAR * t.AMOUNT )) - (sum( t.AMOUNT ) * sum(power(t.YEAR, 2)))) / (power(sum(t.YEAR), 2) - count(1) * sum(power(t.YEAR, 2))) as INTERCEPT FROM ( SELECT AVG(D.AMOUNT) as AMOUNT, Y.YEAR as YEAR, MAKEDATE(Y.YEAR,1) as AMOUNT_DATE FROM CITY C, STATION S, YEAR_REF Y, MONTH_REF M, DAILY D WHERE $X{ IN, C.ID, CityCode } AND SQRT( POW( C.LATITUDE - S.LATITUDE, 2 ) + POW( C.LONGITUDE - S.LONGITUDE, 2 ) ) < $P{Radius} AND S.STATION_DISTRICT_ID = Y.STATION_DISTRICT_ID AND Y.YEAR BETWEEN 1900 AND 2009 AND M.YEAR_REF_ID = Y.ID AND M.CATEGORY_ID = $P{CategoryCode} AND M.ID = D.MONTH_REF_ID AND D.DAILY_FLAG_ID <> 'M' GROUP BY Y.YEAR ) t ) ymxb WHERE $X{ IN, C.ID, CityCode } AND SQRT( POW( C.LATITUDE - S.LATITUDE, 2 ) + POW( C.LONGITUDE - S.LONGITUDE, 2 ) ) < $P{Radius} AND S.STATION_DISTRICT_ID = Y.STATION_DISTRICT_ID AND Y.YEAR BETWEEN 1900 AND 2009 AND M.YEAR_REF_ID = Y.ID AND M.CATEGORY_ID = $P{CategoryCode} AND M.ID = D.MONTH_REF_ID AND D.DAILY_FLAG_ID <> 'M' GROUP BY Y.YEAR Question How do I execute the duplicate bits only once per query, instead of twice? The duplicate bit is the WHERE clause: $X{ IN, C.ID, CityCode } AND SQRT( POW( C.LATITUDE - S.LATITUDE, 2 ) + POW( C.LONGITUDE - S.LONGITUDE, 2 ) ) < $P{Radius} AND S.STATION_DISTRICT_ID = Y.STATION_DISTRICT_ID AND Y.YEAR BETWEEN 1900 AND 2009 AND M.YEAR_REF_ID = Y.ID AND M.CATEGORY_ID = $P{CategoryCode} AND M.ID = D.MONTH_REF_ID AND D.DAILY_FLAG_ID <> 'M' Related http://stackoverflow.com/questions/1595659/how-to-eliminate-duplicate-calculation-in-sql Thank you!

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  • In Wireshark's Protocol Hierarchy Statistics screen, is the total byte count of a capture the sum of the Bytes column or just the top line (Frame)?

    - by Howiecamp
    Part 1 - I'm looking at Wireshark's Protocol Hierarchy Statistics screen (sample below), is the total byte count of the capture the sum of the Bytes column or just the top line (Frame)? I'm 99% that it's the latter because of protocol rollup but I wanted to conform. Part 2 - From Wireshark documentation on this screen, "Protocol layers can consist of packets that won't contain any higher layer protocol, so the sum of all higher layer packets may not sum up to the protocols packet count. Example: In the screenshot TCP has 85,83% but the sum of the subprotocols (HTTP, ...) is much less. This may be caused by TCP protocol overhead, e.g. TCP ACK packets won't be counted as packets of the higher layer)." Can you explain this?

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  • C# Why can't I find Sum() of this HashSet. says "Arithmetic operation resulted in an overflow."

    - by user2332665
    I was trying to solve this problem projecteuler,problem125 this is my solution in python(just for understanding the logic) import math lim=10**8 found=set() for start in xrange(1,int(math.sqrt(lim))): sos = start*start for i in xrange(start+1,int(math.sqrt(lim))): sos += (i*i) if sos >= lim: break s=str(int(sos)) if s==s[::-1]: found.add(sos) print sum(found) the same code I wrote in C# is as follows using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace ConsoleApplication1 { class Program { public static bool isPalindrome(string s) { string temp = ""; for (int i=s.Length-1;i>=0;i-=1){temp+=s[i];} return (temp == s); } static void Main(string[] args) { int lim = Convert.ToInt32(Math.Pow(10,8)); var found = new HashSet<int>(); for (int start = 1; start < Math.Sqrt(lim); start += 1) { int s = start *start; for (int i = start + 1; start < Math.Sqrt(lim); i += 1) { s += i * i; if (s > lim) { break; } if (isPalindrome(s.ToString())) { found.Add(s); } } } Console.WriteLine(found.Sum()); } } } the code debugs fine until it gives an exception at Console.WriteLine(found.Sum()); (line31). Why can't I find Sum() of the set found

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  • If all variables are a subset of the superkey, is the database design 5NF? [migrated]

    - by Lukazoid
    I have a table called LogMessages, which has the following columns: Level A numeric value which represents Trace, Debug, Info, Warning, Error or Fatal Time A UTC time Message Foreign key to a Messages table Source Foreign key to a Sources table User Foreign key to a Users table From what I can see, all of these columns are a part of the super key; if any single value differs to an existing row, a new row can be created. My question is, does this design comply to fifth normal form? I am unsure as some groups of data will be repeating, however I don't believe this violates 5NF? (correct me if I'm wrong)

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  • Why does async BeginReceiveFrom never time out on a raw socket?

    - by James Hugard
    Writing an asynchronous Ping using Raw Sockets in F#, to enable parallel requests using as few threads as possible. Not using "System.Net.NetworkInformation.Ping", because it appears to allocate one thread per request. Am also interested in using F# async workflows. The synchronous version below correctly times out when the target host does not exist/respond, but the asynchronous version hangs. Both work when the host does respond. Not sure if this is a .NET issue, or an F# one... Any ideas? (note: the process must run as Admin to allow Raw Socket access) This throws a timeout: let result = Ping.Ping ( IPAddress.Parse( "192.168.33.22" ), 1000 ) However, this hangs: let result = Ping.AsyncPing ( IPAddress.Parse( "192.168.33.22" ), 1000 ) |> Async.RunSynchronously Here's the code... module Ping open System open System.Net open System.Net.Sockets open System.Threading //---- ICMP Packet Classes type IcmpMessage (t : byte) = let mutable m_type = t let mutable m_code = 0uy let mutable m_checksum = 0us member this.Type with get() = m_type member this.Code with get() = m_code member this.Checksum = m_checksum abstract Bytes : byte array default this.Bytes with get() = [| m_type m_code byte(m_checksum) byte(m_checksum >>> 8) |] member this.GetChecksum() = let mutable sum = 0ul let bytes = this.Bytes let mutable i = 0 // Sum up uint16s while i < bytes.Length - 1 do sum <- sum + uint32(BitConverter.ToUInt16( bytes, i )) i <- i + 2 // Add in last byte, if an odd size buffer if i <> bytes.Length then sum <- sum + uint32(bytes.[i]) // Shuffle the bits sum <- (sum >>> 16) + (sum &&& 0xFFFFul) sum <- sum + (sum >>> 16) sum <- ~~~sum uint16(sum) member this.UpdateChecksum() = m_checksum <- this.GetChecksum() type InformationMessage (t : byte) = inherit IcmpMessage(t) let mutable m_identifier = 0us let mutable m_sequenceNumber = 0us member this.Identifier = m_identifier member this.SequenceNumber = m_sequenceNumber override this.Bytes with get() = Array.append (base.Bytes) [| byte(m_identifier) byte(m_identifier >>> 8) byte(m_sequenceNumber) byte(m_sequenceNumber >>> 8) |] type EchoMessage() = inherit InformationMessage( 8uy ) let mutable m_data = Array.create 32 32uy do base.UpdateChecksum() member this.Data with get() = m_data and set(d) = m_data <- d this.UpdateChecksum() override this.Bytes with get() = Array.append (base.Bytes) (this.Data) //---- Synchronous Ping let Ping (host : IPAddress, timeout : int ) = let mutable ep = new IPEndPoint( host, 0 ) let socket = new Socket( AddressFamily.InterNetwork, SocketType.Raw, ProtocolType.Icmp ) socket.SetSocketOption( SocketOptionLevel.Socket, SocketOptionName.SendTimeout, timeout ) socket.SetSocketOption( SocketOptionLevel.Socket, SocketOptionName.ReceiveTimeout, timeout ) let packet = EchoMessage() let mutable buffer = packet.Bytes try if socket.SendTo( buffer, ep ) <= 0 then raise (SocketException()) buffer <- Array.create (buffer.Length + 20) 0uy let mutable epr = ep :> EndPoint if socket.ReceiveFrom( buffer, &epr ) <= 0 then raise (SocketException()) finally socket.Close() buffer //---- Entensions to the F# Async class to allow up to 5 paramters (not just 3) type Async with static member FromBeginEnd(arg1,arg2,arg3,arg4,beginAction,endAction,?cancelAction): Async<'T> = Async.FromBeginEnd((fun (iar,state) -> beginAction(arg1,arg2,arg3,arg4,iar,state)), endAction, ?cancelAction=cancelAction) static member FromBeginEnd(arg1,arg2,arg3,arg4,arg5,beginAction,endAction,?cancelAction): Async<'T> = Async.FromBeginEnd((fun (iar,state) -> beginAction(arg1,arg2,arg3,arg4,arg5,iar,state)), endAction, ?cancelAction=cancelAction) //---- Extensions to the Socket class to provide async SendTo and ReceiveFrom type System.Net.Sockets.Socket with member this.AsyncSendTo( buffer, offset, size, socketFlags, remoteEP ) = Async.FromBeginEnd( buffer, offset, size, socketFlags, remoteEP, this.BeginSendTo, this.EndSendTo ) member this.AsyncReceiveFrom( buffer, offset, size, socketFlags, remoteEP ) = Async.FromBeginEnd( buffer, offset, size, socketFlags, remoteEP, this.BeginReceiveFrom, (fun asyncResult -> this.EndReceiveFrom(asyncResult, remoteEP) ) ) //---- Asynchronous Ping let AsyncPing (host : IPAddress, timeout : int ) = async { let ep = IPEndPoint( host, 0 ) use socket = new Socket( AddressFamily.InterNetwork, SocketType.Raw, ProtocolType.Icmp ) socket.SetSocketOption( SocketOptionLevel.Socket, SocketOptionName.SendTimeout, timeout ) socket.SetSocketOption( SocketOptionLevel.Socket, SocketOptionName.ReceiveTimeout, timeout ) let packet = EchoMessage() let outbuffer = packet.Bytes try let! result = socket.AsyncSendTo( outbuffer, 0, outbuffer.Length, SocketFlags.None, ep ) if result <= 0 then raise (SocketException()) let epr = ref (ep :> EndPoint) let inbuffer = Array.create (outbuffer.Length + 256) 0uy let! result = socket.AsyncReceiveFrom( inbuffer, 0, inbuffer.Length, SocketFlags.None, epr ) if result <= 0 then raise (SocketException()) return inbuffer finally socket.Close() }

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  • How to detect a timeout when using asynchronous Socket.BeginReceive?

    - by James Hugard
    Writing an asynchronous Ping using Raw Sockets in F#, to enable parallel requests using as few threads as possible. Not using "System.Net.NetworkInformation.Ping", because it appears to allocate one thread per request. Am also interested in using F# async workflows. The synchronous version below correctly times out when the target host does not exist/respond, but the asynchronous version hangs. Both work when the host does respond. Not sure if this is a .NET issue, or an F# one... Any ideas? (note: the process must run as Admin to allow Raw Socket access) This throws a timeout: let result = Ping.Ping ( IPAddress.Parse( "192.168.33.22" ), 1000 ) However, this hangs: let result = Ping.AsyncPing ( IPAddress.Parse( "192.168.33.22" ), 1000 ) |> Async.RunSynchronously Here's the code... module Ping open System open System.Net open System.Net.Sockets open System.Threading //---- ICMP Packet Classes type IcmpMessage (t : byte) = let mutable m_type = t let mutable m_code = 0uy let mutable m_checksum = 0us member this.Type with get() = m_type member this.Code with get() = m_code member this.Checksum = m_checksum abstract Bytes : byte array default this.Bytes with get() = [| m_type m_code byte(m_checksum) byte(m_checksum >>> 8) |] member this.GetChecksum() = let mutable sum = 0ul let bytes = this.Bytes let mutable i = 0 // Sum up uint16s while i < bytes.Length - 1 do sum <- sum + uint32(BitConverter.ToUInt16( bytes, i )) i <- i + 2 // Add in last byte, if an odd size buffer if i <> bytes.Length then sum <- sum + uint32(bytes.[i]) // Shuffle the bits sum <- (sum >>> 16) + (sum &&& 0xFFFFul) sum <- sum + (sum >>> 16) sum <- ~~~sum uint16(sum) member this.UpdateChecksum() = m_checksum <- this.GetChecksum() type InformationMessage (t : byte) = inherit IcmpMessage(t) let mutable m_identifier = 0us let mutable m_sequenceNumber = 0us member this.Identifier = m_identifier member this.SequenceNumber = m_sequenceNumber override this.Bytes with get() = Array.append (base.Bytes) [| byte(m_identifier) byte(m_identifier >>> 8) byte(m_sequenceNumber) byte(m_sequenceNumber >>> 8) |] type EchoMessage() = inherit InformationMessage( 8uy ) let mutable m_data = Array.create 32 32uy do base.UpdateChecksum() member this.Data with get() = m_data and set(d) = m_data <- d this.UpdateChecksum() override this.Bytes with get() = Array.append (base.Bytes) (this.Data) //---- Synchronous Ping let Ping (host : IPAddress, timeout : int ) = let mutable ep = new IPEndPoint( host, 0 ) let socket = new Socket( AddressFamily.InterNetwork, SocketType.Raw, ProtocolType.Icmp ) socket.SetSocketOption( SocketOptionLevel.Socket, SocketOptionName.SendTimeout, timeout ) socket.SetSocketOption( SocketOptionLevel.Socket, SocketOptionName.ReceiveTimeout, timeout ) let packet = EchoMessage() let mutable buffer = packet.Bytes try if socket.SendTo( buffer, ep ) <= 0 then raise (SocketException()) buffer <- Array.create (buffer.Length + 20) 0uy let mutable epr = ep :> EndPoint if socket.ReceiveFrom( buffer, &epr ) <= 0 then raise (SocketException()) finally socket.Close() buffer //---- Entensions to the F# Async class to allow up to 5 paramters (not just 3) type Async with static member FromBeginEnd(arg1,arg2,arg3,arg4,beginAction,endAction,?cancelAction): Async<'T> = Async.FromBeginEnd((fun (iar,state) -> beginAction(arg1,arg2,arg3,arg4,iar,state)), endAction, ?cancelAction=cancelAction) static member FromBeginEnd(arg1,arg2,arg3,arg4,arg5,beginAction,endAction,?cancelAction): Async<'T> = Async.FromBeginEnd((fun (iar,state) -> beginAction(arg1,arg2,arg3,arg4,arg5,iar,state)), endAction, ?cancelAction=cancelAction) //---- Extensions to the Socket class to provide async SendTo and ReceiveFrom type System.Net.Sockets.Socket with member this.AsyncSendTo( buffer, offset, size, socketFlags, remoteEP ) = Async.FromBeginEnd( buffer, offset, size, socketFlags, remoteEP, this.BeginSendTo, this.EndSendTo ) member this.AsyncReceiveFrom( buffer, offset, size, socketFlags, remoteEP ) = Async.FromBeginEnd( buffer, offset, size, socketFlags, remoteEP, this.BeginReceiveFrom, (fun asyncResult -> this.EndReceiveFrom(asyncResult, remoteEP) ) ) //---- Asynchronous Ping let AsyncPing (host : IPAddress, timeout : int ) = async { let ep = IPEndPoint( host, 0 ) use socket = new Socket( AddressFamily.InterNetwork, SocketType.Raw, ProtocolType.Icmp ) socket.SetSocketOption( SocketOptionLevel.Socket, SocketOptionName.SendTimeout, timeout ) socket.SetSocketOption( SocketOptionLevel.Socket, SocketOptionName.ReceiveTimeout, timeout ) let packet = EchoMessage() let outbuffer = packet.Bytes try let! result = socket.AsyncSendTo( outbuffer, 0, outbuffer.Length, SocketFlags.None, ep ) if result <= 0 then raise (SocketException()) let epr = ref (ep :> EndPoint) let inbuffer = Array.create (outbuffer.Length + 256) 0uy let! result = socket.AsyncReceiveFrom( inbuffer, 0, inbuffer.Length, SocketFlags.None, epr ) if result <= 0 then raise (SocketException()) return inbuffer finally socket.Close() }

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