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  • CUDA, more threads for same work = Longer run time despite better occupancy, Why?

    - by zenna
    I encountered a strange problem where increasing my occupancy by increasing the number of threads reduced performance. I created the following program to illustrate the problem: #include <stdio.h> #include <stdlib.h> #include <cuda_runtime.h> __global__ void less_threads(float * d_out) { int num_inliers; for (int j=0;j<800;++j) { //Do 12 computations num_inliers += threadIdx.x*1; num_inliers += threadIdx.x*2; num_inliers += threadIdx.x*3; num_inliers += threadIdx.x*4; num_inliers += threadIdx.x*5; num_inliers += threadIdx.x*6; num_inliers += threadIdx.x*7; num_inliers += threadIdx.x*8; num_inliers += threadIdx.x*9; num_inliers += threadIdx.x*10; num_inliers += threadIdx.x*11; num_inliers += threadIdx.x*12; } if (threadIdx.x == -1) d_out[blockIdx.x*blockDim.x+threadIdx.x] = num_inliers; } __global__ void more_threads(float *d_out) { int num_inliers; for (int j=0;j<800;++j) { // Do 4 computations num_inliers += threadIdx.x*1; num_inliers += threadIdx.x*2; num_inliers += threadIdx.x*3; num_inliers += threadIdx.x*4; } if (threadIdx.x == -1) d_out[blockIdx.x*blockDim.x+threadIdx.x] = num_inliers; } int main(int argc, char* argv[]) { float *d_out = NULL; cudaMalloc((void**)&d_out,sizeof(float)*25000); more_threads<<<780,128>>>(d_out); less_threads<<<780,32>>>(d_out); return 0; } Note both kernels should do the same amount of work in total, the (if threadIdx.x == -1 is a trick to stop the compiler optimising everything out and leaving an empty kernel). The work should be the same as more_threads is using 4 times as many threads but with each thread doing 4 times less work. Significant results form the profiler results are as followsL: more_threads: GPU runtime = 1474 us,reg per thread = 6,occupancy=1,branch=83746,divergent_branch = 26,instructions = 584065,gst request=1084552 less_threads: GPU runtime = 921 us,reg per thread = 14,occupancy=0.25,branch=20956,divergent_branch = 26,instructions = 312663,gst request=677381 As I said previously, the run time of the kernel using more threads is longer, this could be due to the increased number of instructions. Why are there more instructions? Why is there any branching, let alone divergent branching, considering there is no conditional code? Why are there any gst requests when there is no global memory access? What is going on here! Thanks

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  • Generics and Performance question.

    - by Tarmon
    Hey Everyone, I was wondering if anyone could look over a class I wrote, I am receiving generic warnings in Eclipse and I am just wondering if it could be cleaned up at all. All of the warnings I received are surrounded in ** in my code below. The class takes a list of strings in the form of (hh:mm AM/PM) and converts them into HourMinute objects in order to find the first time in the list that comes after the current time. I am also curious about if there are more efficient ways to do this. This works fine but the student in me just wants to find out how I could do this better. public class FindTime { private String[] hourMinuteStringArray; public FindTime(String[] hourMinuteStringArray){ this.hourMinuteStringArray = hourMinuteStringArray; } public int findTime(){ HourMinuteList hourMinuteList = convertHMStringArrayToHMArray(hourMinuteStringArray); Calendar calendar = new GregorianCalendar(); int hour = calendar.get(Calendar.HOUR_OF_DAY); int minute = calendar.get(Calendar.MINUTE); HourMinute now = new HourMinute(hour,minute); int nearestTimeIndex = findNearestTimeIndex(hourMinuteList, now); return nearestTimeIndex; } private int findNearestTimeIndex(HourMinuteList hourMinuteList, HourMinute now){ HourMinute current; int position = 0; Iterator<HourMinute> iterator = **hourMinuteList.iterator()**; while(iterator.hasNext()){ current = (HourMinute) iterator.next(); if(now.compareTo(current) == -1){ return position; } position++; } return position; } private static HourMinuteList convertHMStringArrayToHMArray(String[] times){ FindTime s = new FindTime(new String[1]); HourMinuteList list = s.new HourMinuteList(); String[] splitTime = new String[3]; for(String time : times ){ String[] tempFirst = time.split(":"); String[] tempSecond = tempFirst[1].split(" "); splitTime[0] = tempFirst[0]; splitTime[1] = tempSecond[0]; splitTime[2] = tempSecond[1]; int hour = Integer.parseInt(splitTime[0]); int minute = Integer.parseInt(splitTime[1]); HourMinute hm; if(splitTime[2] == "AM"){ hm = s.new HourMinute(hour,minute); } else if((splitTime[2].equals("PM")) && (hour < 12)){ hm = s.new HourMinute(hour + 12,minute); } else{ hm = s.new HourMinute(hour,minute); } **list.add(hm);** } return list; } class **HourMinuteList** extends **ArrayList** implements RandomAccess{ } class HourMinute implements **Comparable** { int hour; int minute; public HourMinute(int hour, int minute) { setHour(hour); setMinute(minute); } int getMinute() { return this.minute; } String getMinuteString(){ if(this.minute < 10){ return "0" + this.minute; }else{ return "" + this.minute; } } int getHour() { return this.hour; } void setHour(int hour) { this.hour = hour; } void setMinute(int minute) { this.minute = minute; } @Override public int compareTo(Object aThat) { if (aThat instanceof HourMinute) { HourMinute that = (HourMinute) aThat; if (this.getHour() == that.getHour()) { if (this.getMinute() > that.getMinute()) { return 1; } else if (this.getMinute() < that.getMinute()) { return -1; } else { return 0; } } else if (this.getHour() > that.getHour()) { return 1; } else if (this.getHour() < that.getHour()) { return -1; } else { return 0; } } return 0; } } If you have any questions let me know. Thanks, Rob

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  • mongodb read/write performance and mongo hosting in the cloud

    - by z3cko
    we are currently developing a high traffic rails application with facebooker (facebook game). since amazon simpledb (aws-sdb) is really slow, we are thinking of using a dedicated mongodb server as offered by mongoHQ for example. questions: what is the read/writes peak value for a mongodb server running on a amazon ec2 instance? what would be a recommended setup for a ec2 hosted app with mongodb - a master on amazon EBS and replicas on the ec2 instances? any examples or experiences? is there a company that offers mongodb hosting in the cloud? thanks, mz

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  • dynamics CRM performance question

    - by tomo
    Hello Dynamics CRM gurus :) My boss asked me to do a research on available CMSes on market because cms we are using currently is rather a mess. For me as a .NET developer it would be great to choose and implement Dynamics CRM because of extensibility and perfect integration with .NET environment and well-known tools. All marketing blahbla sounds great but I'd like to know about common DISADVANTAGES, ISSUES concerning this system. The most important is how it is performing in a company with about 150 concurrent and very active users. I heard that is't really slow comparing to competitors system. Thanks in advance Best regards, Tomasz.

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  • Best method to compress JSON string in term of performance and compress radio

    - by Eric Yin
    For a JSON string, contains all kinds of settings, numbers, string etc. Total JSON string fairly fall into 10k~50K range. I want to compress it before save to database. So I wonder which compress method should I choose, I am using c# 4, I know I can choose gzip and deflate but the compression radio is not good (although speed is good). More specific, compress can be a little slow (since only once) but should be small. Decompress should be lighting fast since decompress happens lots. Please give some advice.

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  • Server 2008R2 in Extra Small Windows Azure Instance?

    - by Shawn Eary
    Windows Azure hosting for an Extra Small (XS) Windows VM seems to come out to be about $10 a month right now. I think this XS instance gives you the equivalent of a 1 GHZ CPU with 768MB of RAM. I think the minimum requirements for Server 2008 is 1GHZ CPU with 512MB of RAM. Also, I think the minimum requirements for SQL Server Express is 1GHZ CPU with 256 MB of RAM and that the minimum requirements for Team Foundation Server Express 11 Beta is 2.2 GHZ CPU with 1 Gig of RAM (this 2.2 GHZ part could be a problem for my 1 GHZ XS VM...). Given the performance of the XS Azure instance, would I be able to install: a very basic MVC web site; a free instance of SQL Server Express; a free single user instance of Team Foundation Server Express 11 Beta and run the XS VM instance without serious crashing? I know there are other Shared WebHost providers that can provide these features for me, but those hosting providers have the following disadvantages: They sometimes cost a lot of money after all of the "addons" are in place They probably don't provide the level of security and employee integrity that Microsoft can provide They don't provide the total control that an Azure VM seems to provide

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  • android geting data from sql

    - by sagar
    Hello i m new to android. i wont to connect to sql server for store and get data so so me one can help me sending code of android for do it.. i had tried to do tht with java nd it was workink but now i wont to create a aplication for android my java code is :: import java.sql.*; public class MysqlTest { public static void main (String[] args) { Connection conn = null; try { String userName = "pietro"; //change it to your username String password = "pietro"; //change it to your password String url = "jdbc:mysql://192.168.0.67:3306/registro"; Class.forName("com.mysql.jdbc.Driver").newInstance(); conn = DriverManager.getConnection(url, userName, password); Statement s = (Statement) conn.createStatement(); // code for create a tabel in server s.execute("create table School2 (rolno integer,sub text)"); // code for create a tabel in server s.execute("insert into School2(rolno,sub)values(10,'java')"); //code for add value in tabel s.execute("select rolno,sub from School2");//code for add value in tabel s.close(); System.out.println("Database connection established"); } catch (Exception e) { System.err.println("Cannot connect to database server"); } finally { if (conn != null) { try { conn.close (); System.out.println("Database connection terminated"); } catch (Exception e) { /* ignore close errors */ } } } } }

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  • Poor DB4O performance - What am I doing wrong?

    - by Jon
    I read Rob Conery's post about Object databases and thought I'd give it a go. I have a class lets say Book with 15 properties mostly string, some int, one Datetime and 2 decimals. I used Rob's code to open the database file etc to test on a Winforms project not a Web project. So I did the following: for(int i = 0; i < 1000000; i++) { var Book = new Book(); //Assign variables s.Save(Book); } s.CommitChanges(); This took at least a couple of minutes. I then tried to retrieve all data to test speed: var spp = s.All<Passports>(); This one line was quick, however, then doing: sppp.Count() as well as a seperate test doing a foreach loop and incrementing a counter took a couple of minutes. This seems quite slow to me. Am I doing something wrong or am I expecting too much?

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  • Cloud Database Service Latency/Performance

    - by Gcoop
    Hi All, I am running a heavy traffic site and our server is beginning to get to its limits, at the moment the entire LAMP stack is on one box (not ideal). I would like to move the database onto it's own box or onto a cloud service, but from my previous experience moving the database off the same box as the webserver increases the latency of reads quite dramatically slowing down the site. Is using a cloud service for this going to overcome this problem, because as far as I can tell its essentially the same situation (as moving it onto a separate box in my control)? In which case why is there so much popularity around cloud based database services at the moment? Are cloud based database services so quick that the latency of reads is so low that its almost like having it on the same box in the same datacentre?

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  • How to handle large dataset with JPA (or at least with Hibernate)?

    - by Roman
    I need to make my web-app work with really huge datasets. At the moment I get either OutOfMemoryException or output which is being generated 1-2 minutes. Let's put it simple and suppose that we have 2 tables in DB: Worker and WorkLog with about 1000 rows in the first one and 10 000 000 rows in the second one. Latter table has several fields including 'workerId' and 'hoursWorked' fields among others. What we need is: count total hours worked by each user; list of work periods for each user. The most straightforward approach (IMO) for each task in plain SQL is: 1) select Worker.name, sum(hoursWorked) from Worker, WorkLog where Worker.id = WorkLog.workerId group by Worker.name; //results of this query should be transformed to Multimap<Worker, Long> 2) select Worker.name, WorkLog.start, WorkLog.hoursWorked from Worker, WorkLog where Worker.id = WorkLog.workerId; //results of this query should be transformed to Multimap<Worker, Period> //if it was JDBC then it would be vitally //to set resultSet.setFetchSize (someSmallNumber), ~100 So, I have two questions: how to implement each of my approaches with JPA (or at least with Hibernate); how would you handle this problem (with JPA or Hibernate of course)?

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  • How to choose light version of database system

    - by adopilot
    I am starting one POS (Point of sale) project. Targeting system is going to be written in C# .NET 2 WinForms and as main database server We are going to use MS-SQL Server. As we have a lot of POS devices in chain for one store I will love to have backend local data base system on each POS device. Scenario are following: When main server goes down!! POS application should continue working "off-line" with local database, until connection to main server come up again. Now I am in dilemma which local database is going to be most adoptable for me. Here is some notes for helping me point me in right direction: To be Light "My POS devices art usually old and suffering with performances" To be Free "I have a lot of devices and I do not wont additional cost beside main SQL serer" One day Ill love to try all that port on Mono and Linux OS. Here is what I've researched so far: Simple XML "Light but I am afraid of performance, My main table of items is average of 10K records" SQL-Express "I am afraid that my POS devices is poor with hardware for SQLExpress, and also hard to install on each device and configure" Less known Advantage Database Server have free distribution of offline ADT system. DBF with extended Library,"Respect for good old DBFs but that era is behind Me with clipper and DBFs" MS Access Sqlite "Mostly like for now, but I am afraid how it is going to pair with MS SQL do they have same Data types". I know that in this SO is a lot of subjective data, but at least can someone recommended some others lite database system, or things that I shod most take attention before I choice database.

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  • MSSQL Timing out, a couple of questions...

    - by user29000
    Hi, About once a week, my MSSQL server is timing out, or rather the machine runs out of RAM. This morning it reached 3.9GB of the available 4, with MSSQL taking up 2.5GB. I'm concerned that i've not configured SQL to release memory as it should, so I ran sp_who2 while the timeouts were occuring to see what process were running. If i could post the CSV datafile i would, however, there were 85 processes in total, mostly related to the Full Text service: FT Gatherer - About 35 of these running under the 'sa' account against the master database with status of either sleeping or background, many were dependant on other processes. Is that normal? MySite database - There were only 5 processes for the one active site/database and all were either sleeping or suspended - but their lastBatch dates were set to 1/12/2020. Is that normal? The datbase is only about 20mb in size the traffic levels are very low, so i'm thinking of maybe limiting the amount of RAM SQL has access to (from unlimted to maybe 2GB). Any thoughts / advise would be appreciated. Mny thanks Ben

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  • How to improve performance

    - by Ram
    Hi, In one of mine applications I am dealing with graphics objects. I am using open source GPC library to clip/merge two shapes. To improve accuracy I am sampling (adding multiple points between two edges) existing shapes. But before displaying back the merged shape I need to remove all the points between two edges. But I am not able to find an efficient algorithm that will remove all points between two edges which has same slope with minimum CPU utilization. Currently all points are of type PointF Any pointer on this will be a great help.

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  • Browser performance when combining image resizing with animated movement

    - by Steve Reichgut
    I have been tasked with the job of converting a Flash animation into HTML. The animation is rather complex and requires the need to move multiple images (9) from location (x,y) to location (x2,y2) while simultaneously increasing the image size from 215px wide to 930px wide. While doing some initial testing of this animation with just 1-2 images, I noticed a lot of choppiness in FF handling of this animation. To try and isolate the problem, I removed the dynamic resizing of the animation and just moved it from point A to point B. What was interesting was that I saw the same behavior when simply moving a 930px image that was resized down to 215px (via the CSS width or inline width properties). When I try the same animation with a different image that is actually 215px wide, it performed smoothly. I then tried the same animation with the original 930px wide image (with no resizing) and it performed well also. This makes me wonder if the browser is having to "resize" the image down to 215px each time it is moved which is causing the choppiness. Is this a correct assumption? If so, is there any other way to optimize the animation to allow for simultaneous image resizing and image movement? Notes: 1) One optimization I have done is to position the images absolutely in order to minimize the reflow process. 2) I have tested the animation using both jQuery and the fX animation framework.

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  • High performance querying - Suggestions please

    - by Alex Takitani
    Supposing that I have millions of user profiles, with hundreds of fields (name, gender, preferred pet and so on...). You want to make searches on profiles. Ex.:All profiles that has age between x and y, loves butterflies, hates chocolate.... With database would you choose? Suppose that You have a Facebook like load. Speed is a must. Open Source preferred. I've read a lot about Cassandra, HBase, Mongo, Mysql... I just can't decide.....

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  • Performance issues with testing on an ADP2

    - by Stuart
    I have an Android Developer Phone with Android 1.6 installed, sometimes it will take 30 seconds for the home screen to appear after a call or exiting from an application. Why is my phone so slow? Should I replace the memory card? Also, when is the 2.0 coming out for the ADP2? How do I install it?

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  • SQL get data out of BEGIN; ...; END; block in python

    - by Claudiu
    I want to run many select queries at once by putting them between BEGIN; END;. I tried the following: cur = connection.cursor() cur.execute(""" BEGIN; SELECT ...; END;""") res = cur.fetchall() However, I get the error: psycopg2.ProgrammingError: no results to fetch How can I actually get data this way? Likewise, if I just have many selects in a row, I only get data back from the latest one. Is there a way to get data out of all of them?

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  • Are Dynamic Prepared Statements Bad? (with php + mysqli)

    - by John
    I like the flexibility of Dynamic SQL and I like the security + improved performance of Prepared Statements. So what I really want is Dynamic Prepared Statements, which is troublesome to make because bind_param and bind_result accept "fixed" number of arguments. So I made use of an eval() statement to get around this problem. But I get the feeling this is a bad idea. Here's example code of what I mean // array of WHERE conditions $param = array('customer_id'=>1, 'qty'=>'2'); $stmt = $mysqli->stmt_init(); $types = ''; $bindParam = array(); $where = ''; $count = 0; // build the dynamic sql and param bind conditions foreach($param as $key=>$val) { $types .= 'i'; $bindParam[] = '$p'.$count.'=$param["'.$key.'"]'; $where .= "$key = ? AND "; $count++; } // prepare the query -- SELECT * FROM t1 WHERE customer_id = ? AND qty = ? $sql = "SELECT * FROM t1 WHERE ".substr($where, 0, strlen($where)-4); $stmt->prepare($sql); // assemble the bind_param command $command = '$stmt->bind_param($types, '.implode(', ', $bindParam).');'; // evaluate the command -- $stmt->bind_param($types,$p0=$param["customer_id"],$p1=$param["qty"]); eval($command); Is that last eval() statement a bad idea? I tried to avoid code injection by encapsulating values behind the variable name $param. Does anyone have an opinion or other suggestions? Are there issues I need to be aware of?

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  • High performance querying - Sugestions please

    - by Alex Takitani
    Supposing that I have millions of user profiles, with hundreds of fields (name, gender, preferred pet and so on...). With database would You choose? Suppose that You have a Facebook like load. Speed is a must. Open Source preferred. I've read a lot about Cassandra, HBase, Mongo, Mysql... I just can't decide.....

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  • Use Javascript RegEx to extract column names from SQLite Create Table SQL

    - by NimbusSoftware
    I'm trying to extract column names from a SQLite result set from sqlite_master's sql column. I get hosed up in the regular expressions in the match() and split() functions. t1.executeSql('SELECT name, sql FROM sqlite_master WHERE type="table" and name!="__WebKitDatabaseInfoTable__";', [], function(t1, result) { for(i = 0;i < result.rows.length; i++){ var tbl = result.rows.item(i).name; var dbSchema = result.rows.item(i).sql; // errors out on next line var columns = dbSchema.match(/.*CREATE\s+TABLE\s+(\S+)\s+\((.*)\).*/)[2].split(/\s+[^,]+,?\s*/); } }, function(){console.log('err1');} ); I want to parse SQL statements like these... CREATE TABLE sqlite_sequence(name,seq); CREATE TABLE tblConfig (Key TEXT NOT NULL,Value TEXT NOT NULL); CREATE TABLE tblIcon (IconID INTEGER NOT NULL PRIMARY KEY,png TEXT NOT NULL,img32 TEXT NOT NULL,img64 TEXT NOT NULL,Version TEXT NOT NULL) into a strings like theses... name,seq Key,Value IconID,png,img32,img64,Version Any help with a RegEx would be greatly appreciated.

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  • MonoTouch - foreach vs for loops (performance)

    - by ifwdev
    Normally I'm well aware that a consideration like this is premature optimization. Right now I have some event handlers being attached inside a foreach loop. I am wondering if this style might be prone to leaks or inefficient memory use due to closures being created. Is there any validity to this thinking?

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  • Which are the RDBMS that minimize the server roundtrips? Which RDBMS are better (in this area) than

    - by user193655
    When the latency is high ("when pinging the server takes time") the server roundtrips make the difference. Now I don't want to focus on the roundtrips created in programming, but the roundtrips that occur "under the hood" in the DB engine, so the roundtrips that are 100% dependant on how the RDBMS is written itself. I have been told that FireBird has more roundtrips than MySQL. But this is the only information I know. I am currently supporting MS SQL but I'd like to change RDBMS (because I use Express Editions and in my scenario they are quite limiting from the performance point of view), so to make a wise choice I would like to include also this point into "my RDBMS comparison feature matrix" to understand which is the best RDBMS to choose as an alternative to MS SQL. So the bold sentence above would make me prefer MySQL to Firebird (for the roundtrips concept, not in general), but can anyone add informations? And MS SQL where is it located? Is someone able to "rank" the roundtrip performance of the main RDBMS, or at least: MS SQL, MySql, Postegresql, Firebird (I am not interested in Oracle since it is not free, and if I have to change I would change to a free RDBMS). Anyway MySql (as mentioned several times on stackoverflow) has a not clear future and a not 100% free license. So my final choice will probably dall on PostgreSQL or Firebird. Additional info: somehow you can answer my question by making a simple list like: MSSQL:3; MySQL:1; Firebird:2; Postgresql:2 (where 1 is good, 2 average, 3 bad). Of course if you can post some links where the roundtrips per RDBMSs are compared it would be great

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  • Horrible eclipse performance on macbook pro running 10.5.8

    - by user246114
    Hi I am using eclipse galileo on my macbook pro. After a few minutes it starts dragging really badly, like it takes 8 seconds to open a file. I don't have many files open at all. I already modified the config file to increase ram and all that stuff. Is there something wrong with this version of eclipse, never had it run so poorly on here, Thanks

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