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  • MySql multiple selects batching in .net

    - by Amith George
    I have a situation in my application. For each x-axis point in my chart, I am plotting 5 y-axis values. To calculate each of these 5 values, I need to make 4 different queries. Ie, for each x-axis point I need to fire 20 sql queries. Now, I need to plot 40 such points in the my chart. Its resulting in a pathetic performance where it takes close to a minute to get all the data back from the database. Each of 4 different queries consists of a join between 2 tables. One has only 6 rows. The other close to 10,000. Each of the 4 queries has different WHERE clauses, so they are different queries. For each point in the x-axis, only the values for the where clauses change. I have tried combining each of the 4 queries into one big string. Basically batch the four selects. These are again batched for each y-axis value. So, for each x-axis point, I am now firing one big command that consists of 20 different select statements. Technically, I should be experiencing a big performance boost, right? Instead of hitting the db 40x5x4 = 800 times, I am now hitting it just 40 times. But instead of taking 60 seconds, it taking 50-55 seconds... not much of a help. I am using MySql 5.1, and the 6.1 version of its .Net connector. What can I do to improve the performance? Edit: One of the 4 queries is as follows: SELECT SUM(TIME_TO_SEC(TIMEDIFF(T1.col2, T1.col1))* T2.col1 / (3600 *1000)) AS TotalTime FROM Table T1 JOIN Table T2 ON T1.col3 = T2.col3 WHERE T1.col4 = 'i' AND T1.col1 >= '2009-12-25 00:00:00' AND T1.col2 <= '2009-12-26 00:00:00'; The other 3 queries are similar, only the where clause changes slightly. This set of 4 queries is fired 5 times. The first 3 times against the join of table T1 and T2, passing in different values for col4. And the next two times against the join of table T3 and T2 passing in different values for col4. These 5 values are the y-axis values for a particular x-axis point. The data returned by all these queries is the same format. so, we tried doing a UNION ALL on all these queries. No substantial difference. One strange thing, however, after indexing the foreign key on the table T1 [while it contained over a lakh records], the queries were using the index, but they had become slower. At times, the queries would take double the time to return the data.

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  • optimizing operating systems to provide maximum informix performance.

    - by Frank Developer
    Are there any Informix-specific guides for optimizing any operating system where an ifx engine is running? For example, in Linux, strip-down to a bare minimum all unecessary binaries, daemons, utilities, tune kernel parameters, optimize raw and cooked devices (hdparm). Someday, maybe, informix can create its own proprietary PICK-like O/S. The general idea is for the OS where ifx sits on have the smallest footprint, lowest overhead impact on ifx and provide optimized ifx performance.

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  • Drawing performance with CGImageCreateWithJPEGDataProvider?

    - by Rnegi
    I've actually curious about this for the iPhone. I am getting an MJPEG stream from a server and trying to render it natively on the iphone (without the use of safari class). Reasons for this is because the safari class while CAN render MJPEG natively, does not do so at the framerate I would like. So I tried drawing it natively, but I've come up with performance issues, namely a syncing issue between what I'm getting from the server and what I am able to draw onto the screen of the phone. (There should be a little lag, but the drift gets really bad, which is what I want to avoid). So I have a connection set up to my server and I do get the JPEGS. It's just data I insert into a NSMutableArray buffer CFMutableDataRef _t_data_ref = (CFMutableDataRef)[_buffer_array objectAtIndex:0]; //CGDataProviderRef imgDataProvider = CGDataProviderCreateWithCFData (_cf_buffer_data); CGDataProviderRef imgDataProvider = CGDataProviderCreateWithCFData(_t_data_ref); CGImageRef image = CGImageCreateWithJPEGDataProvider(imgDataProvider, NULL, true, kCGRenderingIntentDefault); CGImageRef imgRef = image; CGContextDrawImage(context, CGRectMake(0, 17, 380, 285), imgRef); CGImageRelease(image); CGDataProviderRelease(imgDataProvider); please note this is the gist of my code, but it should summarize what I am trying to accomplish with regards to drawing. Also in order to get the framerate in sync, I had to detach a separate thread that sleeps X seconds and calls [self setNeedsDisplay]. NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; // Top-level pool while(1) { //[NSThread sleepForTimeInterval:TIMER_REFRESH_VALUE]; //sleep(unsigned int ); usleep(MICRO_REFRESH_VALUE); if ([_buffer_array count] > 10) { //NSLog(@"stuff %d", [_buffer_array count]); //[self setNeedsDisplay]; [self performSelectorOnMainThread:@selector(setNeedsDisplay) withObject:nil waitUntilDone:NO]; } } [pool release]; // Release the objects in the pool. My buffer of jpeg data actually fills up quite quick, but I can't seem to actually consume what i'm getting at the same rate, actually much slower. Are there any documents that can describe what kind of performance tuning I can do to make it go faster when rendering the JPEG to the screen? Or am I kind of stuck here? Thanks!

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  • Does replace into have a where clause?

    - by Lajos Arpad
    I'm writing an application and I'm using MySQL as DBMS, we are downloading property offers and there were some performance issues. The old architecture looked like this: A property is updated. If the number of affected rows is not 1, then the update is not considered successful, elseway the update query solves our problem. If the update was not successful, and the number of affected rows is more than 1, we have duplicates and we delete all of them. After we deleted duplicates if needed if the update was not successful, an insert happens. This architecture was working well, but there were some speed issues, because properties are deleted if they were not updated for 15 days. Theoretically the main problem is deleting properties, because some properties are alive for months and the indexes are very far from each other (we are talking about 500, 000+ properties). Our host told me to use replace into instead of deleting properties and all deprecated properties should be considered as DEAD. I've done this, but problems started to occur because of syntax error and I couldn't find anywhere an example of replace into with a where clause (I'd like to replace a DEAD property with the new property instead of deleting the old property and insert a new to assure optimization). My query looked like this: replace into table_name(column1, ..., columnn) values(value1, ..., valuen) where ID = idValue Of course, I've calculated idValue and handled everything but I had a syntax error. I would like to know if I'm wrong and there is a where clause for replace into. I've found an alternative solution, which is even better than replace into (using simply an update query) because deletes are happening behind the curtains if I use replace into, but I would like to know if I'm wrong when I say that replace into doesn't have a where clause. For more reference, see this link: http://dev.mysql.com/doc/refman/5.0/en/replace.html Thank you for your answers in advance, Lajos Árpád

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  • XPATH query, HtmlAgilityPack and Extracting Text

    - by Soham
    I had been trying to extract links from a class called "tim_new" . I have been given a solution as well. Both the solution, snippet and necessary information is given here The said XPATH query was "//a[@class='tim_new'], my question is, how did this query differentiate between the first line of the snippet (given in the link above and the second line of the snippet). More specifically, what is the literal translation (in English) of this XPATH query. Furthermore, I want to write a few lines of code to extract the text written against NSE: <div class="FL gL_12 PL10 PT15">BSE: 523395 &nbsp;&nbsp;|&nbsp;&nbsp; NSE: 3MINDIA &nbsp;&nbsp;|&nbsp;&nbsp; ISIN: INE470A01017</div> Would appreciate help in forming the necessary selection query. My code is written as: IEnumerable<string> NSECODE = doc.DocumentNode.SelectSingleNode("//div[@NSE:]"); But this doesnt look right. Would appreciate some help.

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  • Question about SQL Server HierarchyID depth-first performance

    - by AndalusianCat
    I am trying to implement hierarchyID in a table (dbo.[Message]) containing roughly 50,000 rows (will grow substantially in the future). However it takes 30-40 seconds to retrieve about 25 results. The root node is a filler in order to provide uniqueness, therefor every subsequent row is a child of that dummy row. I need to be able to traverse the table depth-first and have made the hierarchyID column (dbo.[Message].MessageID) the clustering primary key, have also added a computed smallint (dbo.[Message].Hierarchy) which stores the level of the node. Usage: A .Net application passes through a hierarchyID value into the database and I want to be able to retrieve all (if any) children AND parents of that node (besides the root, as it is filler). A simplified version of the query I am using: @MessageID hierarchyID /* passed in from application */ SELECT m.MessageID, m.MessageComment FROM dbo.[Message] as m WHERE m.Messageid.IsDescendantOf(@MessageID.GetAncestor((@MessageID.GetLevel()-1))) = 1 ORDER BY m.MessageID From what I understand, the index should be detected automatically without a hint. From searching forums I have seen people utilizing index hints, at least in the case of breadth-first indexes, as apparently CLR calls may be opaque to the query optimizer. I have spent the past few days trying to find a solution for this issue, but to no avail. I would greatly appreciate any assistance, and as this is my first post, I apologize in advance if this would be considered a 'noobish' question, I have read the MS documentation and searched countless forums, but have not came across a succinct description of the specific issue.

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  • PHP MYSQLI query error?

    - by Chris Leah
    Hey This is my login script, using PHP5 and MYSQLi, I just had help spotting errors in my query, but still it will not let me login, even though the username and password are correct and in the database, it just keeps returning the error: your username and password do not match any in our db. But I know they do lol...could any body spot the problem? //Check if the form has been submitted if (isset($_POST['login'])) { //Check if username and password are empty if ($_POST['username']!='' && $_POST['password']!='') { //Create query to check username and password to database $validate_user = $mysqli->query('SELECT id, username, password, active FROM users WHERE = username = "'.$mysqli->real_escape_string($_POST['username']).'" AND password = "'.$mysqli->real_escape_string(md5($_POST['password'])).'"'); //We check if the query returns true if ($validate_user->num_rows == 1) { $row = $validate_user->fetch_assoc(); //Check if the user has activated there account if ($row['activated'] == 1) { $_SESSION['id'] = $row['id']; $_SESSION['logged_in'] = true; Header('Location: ../main/index.php'); } //Show this error if activation returns as 0 else { $error = '<p class="error">Please activate your account.</p>'; } } //Show this error if the details matched any in the db else { $error = '<p class="error">Your username and password are not in our database!</p>'; } } //Show this error if the username and password field have not been entered else { $error = '<p class="error">Please enter your username and password.</p>'; } }

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  • Retrieve 2 last posts for each category.

    - by Savageman
    Hello, Lets say I have 2 tables: blog_posts and categories. Each blog post belongs to only ONE category, so there is basically a foreign key between the 2 tables here. I would like to retrieve the 2 lasts posts from each category, is it possible to achieve this in a single request? GROUP BY would group everything and leave me with only one row in each category. But I want 2 of them. It would be easy to perform 1 + N query (N = number of category). First retrieve the categories. And then retrieve 2 posts from each category. I believe it would also be quite easy to perform M queries (M = number of posts I want from each category). First query selects the first post for each category (with a group by). Second query retrieves the second post for each category. etc. I'm just wondering if someone has a better solution for this. I don't really mind doing 1+N queries for that, but for curiosity and general SQL knowledge, it would be appreciated! Thanks in advance to whom can help me with this.

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  • Manipulate score/rank on query results from NHibernate.Search

    - by Fernando Figueiredo
    I've been working with NHibernate, NHibernate.Search and Lucene.Net to improve the search engine used on the website I develop. Basically, I use it to search contents of corporations specification documents. This is not to be confused with Lucene's notion of documents: in my case, a specification document (which I'll hereafter call a "specdoc") can contain many pages, and the content of these pages are the ones that are actually indexed (thus, the pages themselves are the ones that fall into Lucene's concept of documents). So, the pages belong to a specdoc, that in turn belong to a corporation (so, a corporation can have many specdocs). I'm using NHibernate.Search "IndexEmbedded" and "ContainedIn" attributes to associate the pages with their specdoc and the specdocs to their corporations, so I can query for terms in specdoc pages and have Lucene/NH.Search return either the pages themselves, the specdocs, or the corporations that match the query on the pages. I can query this way and get ranked results, thus presenting results (that is, corporations, specdocs or pages) by relevance, which is great. But now I need something more. Specifically in the case where I query terms and have NH.Search return the corporations that match, I need to manually/artificially tune the score of some of the results, because there are corporations that I want to show up on the top of the result set - think of "sponsored results". I'm thinking of doing it on my application, maybe creating an entity/database table that contain an association to the corporation entity, and a score boost value. But I don't know how to feed this to Lucene and have it boost the results accordingly at search time. Initially I thought about deriving a Similarity class to do this, but it doesn't look like Similarity can be used to modify result sets at search time. As per this page, it looks like what I need is to mess around with weight or scoring. But the docs are a little superficial in that there are no examples on how to implement a custom scoring, let alone integrate it with NH.Search. So, does anyone know how to do this, or point me to some documentation or working example on how to do something similar? Thanks!

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  • C# - Getting a RawFraction Performance Counter to show a persistant value

    - by jacko
    I've created a performance counter that shows a fraction of an incremeted value (RawFraction type) over a base value (RawBase). Unfortunately, when monitoring this value, it only shows the percentage when one of the counters is incremented. At all other times it it is sampled, it shows 0. Is there some way to tell the counter to hold onto the last value until the next time it needs to recalculate the fraction?

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  • mysql enum performance: is enum slower than INT

    - by JP19
    Hi, Is it better to have a field status enum('active', 'hidden', 'deleted') OR status tinyint(3) with a lookup table. Assume that status can take only one value at a time. In particular, I am interested in knowing, are operations on enum significantly slower than or as fast as operations on int ? There is a related question on SO Mysql: enum confusion but i) It does not discuss performance at all ii) There is very little explanation on WHY one approach is better than the other. regards, JP

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  • MySql: Problem when using a temporary table

    - by Alex
    Hi, I'm trying to use a temporary tables to store some values I need for a query. The reason of using a temporary table is that I don't want to store the data permanently so different users can modify it at the same time. That data is just stored for a second, so I think a temporary table is the best approach for this. The thing is that it seems that the way I'm trying to use it is not right (the query works if I use a permanent one). This is an example of query: CREATE TEMPORARY TABLE SearchMatches (PatternID int not null primary key, Matches int not null) INSERT INTO SearchMatches (PatternID, Matches) VALUES ('12605','1'),('12503','1'),('12587','2'),('12456','1'), ('12457','2'),('12486','2'),('12704','1'),(' 12686','1'), ('12531','2'),('12549','1'),('12604','1'),('12504','1'), ('12586','1'),('12548','1'),('12 530','1'),('12687','2'), ('12485','1'),('12705','1') SELECT pat.id, signatures.signature, products.product, versions.version, builds.build, pat.log_file, sig_types.sig_type, pat.notes, pat.kb FROM patterns AS pat INNER JOIN signatures ON pat.signature = signatures.id INNER JOIN products ON pat.product = products.id INNER JOIN versions ON pat.version = versions.id INNER JOIN builds ON pat.build = builds.id INNER JOIN sig_types ON pat.sig_type = sig_types.id, SearchMatches AS sm INNER JOIN patterns ON patterns.id = sm.PatternID WHERE sm.Matches <> 0 ORDER BY sm.Matches DESC, products.product, versions.version, builds.build LIMIT 0 , 50 Any suggestion? Thanks.

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  • SQL Server, how to join a table in a "rotated" format (returning columns instead of rows)?

    - by Joshua Carmody
    Sorry for the lame title, my descriptive skills are poor today. In a nutshell, I have a query similar to the following: SELECT P.LAST_NAME, P.FIRST_NAME, D.DEMO_GROUP FROM PERSON P JOIN PERSON_DEMOGRAPHIC PD ON PD.PERSON_ID = P.PERSON_ID JOIN DEMOGRAPHIC D ON D.DEMOGRAPHIC_ID = PD.DEMOGRAPHIC_ID This returns output like this: LAST_NAME FIRST_NAME DEMO_GROUP --------------------------------------------- Johnson Bob Male Smith Jane Female Smith Jane Teacher Beeblebrox Zaphod Male Beeblebrox Zaphod Alien Beeblebrox Zaphid Politician I would prefer the output be similar to the following: LAST_NAME FIRST_NAME Male Female Teacher Alien Politician --------------------------------------------------------------------------------------------------------- Johnson Bob 1 0 0 0 0 Smith Jane 0 1 1 0 0 Beeblebrox Zaphod 1 0 0 1 1 The number of rows in the DEMOGRAPHIC table varies, so I can't say with certainty how many columns I need. The query needs to be flexible. Yes, it would be trivial to do this in code. But this query is one piece of a complicated set of stored procedures, views, and reporting services, many of which are outside my sphere of influence. I need to produce this output inside the database to avoid breaking the system. Any ideas? This is MS SQL Server 2005, by the way. Thanks.

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  • WPF Application Typing in Custom TextBox CPU Jumping from 3 to 80 percent

    - by azamsharp
    I have created a RichTextBox called SharpTextBox which indicates and limits the number of characters that can be typed in it. The implementation is shown in the following link: http://www.highoncoding.com/Articles/673_Creating_SharpRichTextBox_for_Live_Character_Count_in_WPF.aspx Anyway when I start typing in the TextBox it goes from 3% to 78%. The TextBox updates the Label control which shows the number of characters remaining for the count. How can I increase the performance of the textbox? UPDATE: I read there seems to be some problem with the TextRange.Text property which kills performance.

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  • Active Directory - Query Group for all machines

    - by Ben Cawley
    Hi, I'm trying to obtain a list of all Machines that are members of a known group. I have the group GUID and am constructing a query using the "memberof=" format and filtering by ObjectClass. This works fine but doesn't return machines if the PrimaryGroup attribute of a machine is set to be the known group. In this case, that machine won't be returned. I've found the explanation of why this is in the following link (See Joe Kaplan's response) http://www.eggheadcafe.com/software/aspnet/29773581/active-directory-query-c.aspx Unfortunately the outlined answer is how to obtain the list of groups from a given user. I'd like to do the reverse and from a given group obtain the list of machines. It seems that the PrimaryGroup information is stored on the Machine/User side so I'm not sure if what I want to do is even possible. I had thought I would be able to query the TokenGroup attribute of the known group and then construct a query to return all machines that have the TokenGroup attribute set but it seems that not all groups have this attribute. Does anyone have any ideas or suggestions? If any clarification is needed let me know! Cheers, Ben

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  • Performance of CSS Transitions vs. JS animation packages

    - by desau
    I'm wondering - is there any difference in performance of using CSS Transitions vs. any of the various JS animation libraries? (scriptaculous, scripty2, jsAnim, MooTools, $fx, etc, etc). I've tried various tests in Safari / Google Chrome, and I don't actually see any difference -- I thought that CSS Transitions were supposed to be hardware accelerated.

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  • WPF Toolkit DataGrid Performance Issue

    - by Ankush
    Hi All, I am facing a performance issue with WPF Toolkit datagrid. In my application I have created a view containing multiple Data Grids (around 25) with about 5 rows in each grid. The grids are placed in an ListView, the problem I am facing is of rendering of my view. Can anyone guide me to resolve the issue. Thanks

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  • My linux server takes more than an hour to boot. Suggestions?

    - by jamieb
    I am building a CentOS 5.4 system that boots off a compact flash card using a card reader that emulates an IDE drive. It literally takes about an hour to boot. The ultra-slow part occurs when Grub is loading the kernel. Once that's done, the rest of the boot process only takes about a minute to get to a login prompt. Does anyone have any suggestions? I suspect that it may have to do with UDMA. Everything IDE-related in my BIOS seems to checkout. The read performance hdparm is telling me 1.77 MB/s. Ouch! (But even at that rate, it still shouldn't take an hour to decompress and load the kernel) [root@server ~]# hdparm -tT /dev/hdc /dev/hdc: Timing cached reads: 2444 MB in 2.00 seconds = 1222.04 MB/sec Timing buffered disk reads: 6 MB in 3.39 seconds = 1.77 MB/sec Trying to enable DMA is a no-go though: [root@server ~]# hdparm -d1 /dev/hdc /dev/hdc: setting using_dma to 1 (on) HDIO_SET_DMA failed: Operation not permitted using_dma = 0 (off) Here's some command outputs that might help: System [root@server ~]# uname -a Linux server.localdomain 2.6.18-164.el5xen #1 SMP Thu Sep 3 04:47:32 EDT 2009 i686 i686 i386 GNU/Linux PCI info: [root@server ~]# lspci -v 00:00.0 Host bridge: Intel Corporation 82945G/GZ/P/PL Memory Controller Hub (rev 02) Subsystem: Intel Corporation 82945G/GZ/P/PL Memory Controller Hub Flags: bus master, fast devsel, latency 0 Capabilities: [e0] Vendor Specific Information 00:02.0 VGA compatible controller: Intel Corporation 82945G/GZ Integrated Graphics Controller (rev 02) (prog-if 00 [VGA controller]) Subsystem: Intel Corporation 82945G/GZ Integrated Graphics Controller Flags: bus master, fast devsel, latency 0, IRQ 10 Memory at fdf00000 (32-bit, non-prefetchable) [size=512K] I/O ports at ff00 [size=8] Memory at d0000000 (32-bit, prefetchable) [size=256M] Memory at fdf80000 (32-bit, non-prefetchable) [size=256K] Capabilities: [90] Message Signalled Interrupts: 64bit- Queue=0/0 Enable- Capabilities: [d0] Power Management version 2 00:1d.0 USB Controller: Intel Corporation 82801G (ICH7 Family) USB UHCI Controller #1 (rev 01) (prog-if 00 [UHCI]) Subsystem: Intel Corporation 82801G (ICH7 Family) USB UHCI Controller #1 Flags: bus master, medium devsel, latency 0, IRQ 16 I/O ports at fe00 [size=32] 00:1d.1 USB Controller: Intel Corporation 82801G (ICH7 Family) USB UHCI Controller #2 (rev 01) (prog-if 00 [UHCI]) Subsystem: Intel Corporation 82801G (ICH7 Family) USB UHCI Controller #2 Flags: bus master, medium devsel, latency 0, IRQ 17 I/O ports at fd00 [size=32] 00:1d.2 USB Controller: Intel Corporation 82801G (ICH7 Family) USB UHCI Controller #3 (rev 01) (prog-if 00 [UHCI]) Subsystem: Intel Corporation 82801G (ICH7 Family) USB UHCI Controller #3 Flags: bus master, medium devsel, latency 0, IRQ 18 I/O ports at fc00 [size=32] 00:1d.3 USB Controller: Intel Corporation 82801G (ICH7 Family) USB UHCI Controller #4 (rev 01) (prog-if 00 [UHCI]) Subsystem: Intel Corporation 82801G (ICH7 Family) USB UHCI Controller #4 Flags: bus master, medium devsel, latency 0, IRQ 19 I/O ports at fb00 [size=32] 00:1d.7 USB Controller: Intel Corporation 82801G (ICH7 Family) USB2 EHCI Controller (rev 01) (prog-if 20 [EHCI]) Subsystem: Intel Corporation 82801G (ICH7 Family) USB2 EHCI Controller Flags: bus master, medium devsel, latency 0, IRQ 16 Memory at fdfff000 (32-bit, non-prefetchable) [size=1K] Capabilities: [50] Power Management version 2 Capabilities: [58] Debug port 00:1e.0 PCI bridge: Intel Corporation 82801 PCI Bridge (rev e1) (prog-if 01 [Subtractive decode]) Flags: bus master, fast devsel, latency 0 Bus: primary=00, secondary=01, subordinate=01, sec-latency=32 I/O behind bridge: 0000d000-0000dfff Memory behind bridge: fde00000-fdefffff Prefetchable memory behind bridge: 00000000fdd00000-00000000fdd00000 Capabilities: [50] #0d [0000] 00:1f.0 ISA bridge: Intel Corporation 82801GB/GR (ICH7 Family) LPC Interface Bridge (rev 01) Subsystem: Intel Corporation 82801GB/GR (ICH7 Family) LPC Interface Bridge Flags: bus master, medium devsel, latency 0 Capabilities: [e0] Vendor Specific Information 00:1f.2 IDE interface: Intel Corporation 82801GB/GR/GH (ICH7 Family) SATA IDE Controller (rev 01) (prog-if 80 [Master]) Subsystem: Intel Corporation 82801GB/GR/GH (ICH7 Family) SATA IDE Controller Flags: bus master, 66MHz, medium devsel, latency 0, IRQ 17 I/O ports at <unassigned> I/O ports at <unassigned> I/O ports at <unassigned> I/O ports at <unassigned> I/O ports at f800 [size=16] Capabilities: [70] Power Management version 2 00:1f.3 SMBus: Intel Corporation 82801G (ICH7 Family) SMBus Controller (rev 01) Subsystem: Intel Corporation 82801G (ICH7 Family) SMBus Controller Flags: medium devsel, IRQ 17 I/O ports at 0500 [size=32] 01:04.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL-8139/8139C/8139C+ (rev 10) Subsystem: Realtek Semiconductor Co., Ltd. RTL-8139/8139C/8139C+ Flags: bus master, medium devsel, latency 32, IRQ 18 I/O ports at de00 [size=256] Memory at fdeff000 (32-bit, non-prefetchable) [size=256] Capabilities: [50] Power Management version 2 01:06.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL-8139/8139C/8139C+ (rev 10) Subsystem: Realtek Semiconductor Co., Ltd. RTL-8139/8139C/8139C+ Flags: bus master, medium devsel, latency 32, IRQ 17 I/O ports at dc00 [size=256] Memory at fdefe000 (32-bit, non-prefetchable) [size=256] Capabilities: [50] Power Management version 2 01:07.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL-8139/8139C/8139C+ (rev 10) Subsystem: Realtek Semiconductor Co., Ltd. RTL-8139/8139C/8139C+ Flags: bus master, medium devsel, latency 32, IRQ 19 I/O ports at da00 [size=256] Memory at fdefd000 (32-bit, non-prefetchable) [size=256] Capabilities: [50] Power Management version 2 hdparm ouput: [root@server ~]# hdparm /dev/hdc /dev/hdc: multcount = 0 (off) IO_support = 0 (default 16-bit) unmaskirq = 0 (off) using_dma = 0 (off) keepsettings = 0 (off) readonly = 0 (off) readahead = 256 (on) geometry = 8146/16/63, sectors = 8211168, start = 0 [root@server ~]# hdparm -I /dev/hdc /dev/hdc: ATA device, with non-removable media Model Number: InnoDisk Corp. - iCF4000 4GB Serial Number: 20091023AACA70000753 Firmware Revision: 081107 Standards: Supported: 5 Likely used: 6 Configuration: Logical max current cylinders 8146 8146 heads 16 16 sectors/track 63 63 -- CHS current addressable sectors: 8211168 LBA user addressable sectors: 8211168 device size with M = 1024*1024: 4009 MBytes device size with M = 1000*1000: 4204 MBytes (4 GB) Capabilities: LBA, IORDY(can be disabled) Standby timer values: spec'd by Vendor R/W multiple sector transfer: Max = 2 Current = 2 DMA: mdma0 mdma1 mdma2 udma0 udma1 *udma2 udma3 udma4 Cycle time: min=120ns recommended=120ns PIO: pio0 pio1 pio2 pio3 pio4 Cycle time: no flow control=120ns IORDY flow control=120ns Commands/features: Enabled Supported: * Power Management feature set * WRITE_BUFFER command * READ_BUFFER command * NOP cmd * CFA feature set * Mandatory FLUSH_CACHE HW reset results: CBLID- above Vih Device num = 0 CFA power mode 1: enabled and required by some commands Maximum current = 100ma Checksum: correct

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  • Using boost unordered map

    - by Amrish
    Guys, I am using dynamic programming approach to solve a problem. Here is a brief overview of the approach Each value generated is identified using 25 unique keys. I use the boost::hash_combine to generate the seed for the hash table using these 25 keys. I store the values in a hash table declared as boost::unordered_map<Key_Object, Data_Object, HashFunction> hashState; I did a time profiling on my algorithm and found that nearly 95% of the run time is spent towards retrieving/inserting data into the hash table. These were the details of my hash table hashState.size() 1880 hashState.load_factor() 0.610588 hashState.bucket_count() 3079 hashState.max_size() 805306456 hashState.max_load_factor() 1 hashState.max_bucket_count() 805306457 I have the following two questions Is there anything which I can do to improve the performance of the Hash Table's insert/retrieve operations? C++ STL has hash_multimap which would also suit my requirement. How does boost libraries unordered_map compare with hash_multimap in terms of insert/retrieve performance.

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  • Should one use < or <= in a for loop

    - by Eugene Katz
    If you had to iterate through a loop 7 times, would you use: for (int i = 0; i < 7; i++) or: for (int i = 0; i <= 6; i++) There are two considerations: performance readability For performance I'm assuming Java or C#. Does it matter if "less than" or "less than or equal to" is used? If you have insight for a different language, please indicate which. For readability I'm assuming 0-based arrays. UPD: My mention of 0-based arrays may have confused things. I'm not talking about iterating through array elements. Just a general loop. There is a good point below about using a constant to which would explain what this magic number is. So if I had "int NUMBER_OF_THINGS = 7" then "i <= NUMBER_OF_THINGS - 1" would look weird, wouldn't it.

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  • [Android] For-Loop Performance Oddity

    - by Jack Holt
    I just noticed something concerning for-loop performance that seems to fly in the face of the recommendations given by the Google Android team. Look at the following code: package com.jackcholt; import android.app.Activity; import android.os.Bundle; import android.util.Log; public class Main extends Activity { @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); loopTest(); finish(); } private void loopTest() { final long loopCount = 1228800; final int[] image = new int[8 * 320 * 480]; long start = System.currentTimeMillis(); for (int i = 0; i < (8 * 320 * 480); i++) { image[i] = i; } for (int i = 0; i < (8 * 320 * 480); i++) { image[i] = i; } Log.i("loopTest", "Elapsed time (recompute loop limit): " + (System.currentTimeMillis() - start)); start = System.currentTimeMillis(); for (int i = 0; i < 1228800; i++) { image[i] = i; } for (int i = 0; i < 1228800; i++) { image[i] = i; } Log.i("loopTest", "Elapsed time (literal loop limit): " + (System.currentTimeMillis() - start)); start = System.currentTimeMillis(); for (int i = 0; i < loopCount; i++) { image[i] = i; } for (int i = 0; i < loopCount; i++) { image[i] = i; } Log.i("loopTest", "Elapsed time (precompute loop limit): " + (System.currentTimeMillis() - start)); } } When I run this code I get the following output in logcat: I/loopTest( 726): Elapsed time (recompute loop limit): 759 I/loopTest( 726): Elapsed time (literal loop limit): 755 I/loopTest( 726): Elapsed time (precompute loop limit): 1317 As you can see the code that seems to recompute the loop limit value on every iteration of the loop compares very well to the code that uses a literal value for the loop limit. However, the code that uses a variable which contains the precomputed value for the loop limit is significantly slower than either of the others. I'm not surprised that accessing a variable should be slower that using a literal but why does code that looks like it should be using two multiply instructions on every iteration of the loop so comparable in performance to a literal? Could it be that because literals are the only thing being multiplied, the Java compiler is optimizing out the multiplication and using a precomputed literal?

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