Search Results

Search found 1337 results on 54 pages for 'capacity estimation'.

facebook twitter digg google delicious technorati stumbleupon myspace wordpress linkedin gmail igoogle windows live tumblr viadeo yahoo buzz yahoo mail yahoo bookmarks favorites email print

Page 2/54 | < Previous Page | 1 2 3 4 5 6 7 8 9 10 11 12  | Next Page >

  • Noise Estimation / Noise Measurement in Image

    - by Drazick
    Hello. I want to estimate the noise in an image. Let's assume the model of an Image + White Noise. Now I want to estimate the Noise Variance. My method is to calculate the Local Variance (3*3 up to 21*21 Blocks) of the image and then find areas where the Local Variance is fairly constant (By calculating the Local Variance of the Local Variance Matrix). I assume those areas are "Flat" hence the Variance is almost "Pure" noise. Yet I don't get constant results. Is there a better way? Thanks.

    Read the article

  • Cardinality Estimation Bug with Lookups in SQL Server 2008 onward

    - by Paul White
    Cost-based optimization stands or falls on the quality of cardinality estimates (expected row counts).  If the optimizer has incorrect information to start with, it is quite unlikely to produce good quality execution plans except by chance.  There are many ways we can provide good starting information to the optimizer, and even more ways for cardinality estimation to go wrong.  Good database people know this, and work hard to write optimizer-friendly queries with a schema and metadata (e.g. statistics) that reduce the chances of poor cardinality estimation producing a sub-optimal plan.  Today, I am going to look at a case where poor cardinality estimation is Microsoft’s fault, and not yours. SQL Server 2005 SELECT th.ProductID, th.TransactionID, th.TransactionDate FROM Production.TransactionHistory AS th WHERE th.ProductID = 1 AND th.TransactionDate BETWEEN '20030901' AND '20031231'; The query plan on SQL Server 2005 is as follows (if you are using a more recent version of AdventureWorks, you will need to change the year on the date range from 2003 to 2007): There is an Index Seek on ProductID = 1, followed by a Key Lookup to find the Transaction Date for each row, and finally a Filter to restrict the results to only those rows where Transaction Date falls in the range specified.  The cardinality estimate of 45 rows at the Index Seek is exactly correct.  The table is not very large, there are up-to-date statistics associated with the index, so this is as expected. The estimate for the Key Lookup is also exactly right.  Each lookup into the Clustered Index to find the Transaction Date is guaranteed to return exactly one row.  The plan shows that the Key Lookup is expected to be executed 45 times.  The estimate for the Inner Join output is also correct – 45 rows from the seek joining to one row each time, gives 45 rows as output. The Filter estimate is also very good: the optimizer estimates 16.9951 rows will match the specified range of transaction dates.  Eleven rows are produced by this query, but that small difference is quite normal and certainly nothing to worry about here.  All good so far. SQL Server 2008 onward The same query executed against an identical copy of AdventureWorks on SQL Server 2008 produces a different execution plan: The optimizer has pushed the Filter conditions seen in the 2005 plan down to the Key Lookup.  This is a good optimization – it makes sense to filter rows out as early as possible.  Unfortunately, it has made a bit of a mess of the cardinality estimates. The post-Filter estimate of 16.9951 rows seen in the 2005 plan has moved with the predicate on Transaction Date.  Instead of estimating one row, the plan now suggests that 16.9951 rows will be produced by each clustered index lookup – clearly not right!  This misinformation also confuses SQL Sentry Plan Explorer: Plan Explorer shows 765 rows expected from the Key Lookup (it multiplies a rounded estimate of 17 rows by 45 expected executions to give 765 rows total). Workarounds One workaround is to provide a covering non-clustered index (avoiding the lookup avoids the problem of course): CREATE INDEX nc1 ON Production.TransactionHistory (ProductID) INCLUDE (TransactionDate); With the Transaction Date filter applied as a residual predicate in the same operator as the seek, the estimate is again as expected: We could also force the use of the ultimate covering index (the clustered one): SELECT th.ProductID, th.TransactionID, th.TransactionDate FROM Production.TransactionHistory AS th WITH (INDEX(1)) WHERE th.ProductID = 1 AND th.TransactionDate BETWEEN '20030901' AND '20031231'; Summary Providing a covering non-clustered index for all possible queries is not always practical, and scanning the clustered index will rarely be optimal.  Nevertheless, these are the best workarounds we have today. In the meantime, watch out for poor cardinality estimates when a predicate is applied as part of a lookup. The worst thing is that the estimate after the lookup join in the 2008+ plans is wrong.  It’s not hopelessly wrong in this particular case (45 versus 16.9951 is not the end of the world) but it easily can be much worse, and there’s not much you can do about it.  Any decisions made by the optimizer after such a lookup could be based on very wrong information – which can only be bad news. If you think this situation should be improved, please vote for this Connect item. © 2012 Paul White – All Rights Reserved twitter: @SQL_Kiwi email: [email protected]

    Read the article

  • Two Weeks As A Software Estimation Rule of Thumb?

    - by Todd Williamson
    I saw a blog posting that spoke to me: http://james-iry.blogspot.com/2010/10/how-to-estimate-software.html Oddly, this is the kind of estimate that I tend to do on smaller projects. Just about everything is "two weeks" as that is comfortably far enough out. I once had an instructor walk us through how to create a more detailed estimate, wherein we already had the requirements up front, etc. and even after all the careful tabulation and such the final instruction was "Now that you have all this documentation go ahead and double it." Agile practitioners seem to like two weeks also as a sprint length. Is there something magical about two weeks? Is it a hrair number for our psyches or some other kind of crutch? Do you have an immediate default fall-back schedule strategy when you are pressed for an initial delivery date?

    Read the article

  • Windows Azure Virtual Machine Readiness and Capacity Assessment for SQL Server

    - by SQLOS Team
    Windows Azure Virtual Machine Readiness and Capacity Assessment for Windows Server Machine Running SQL Server With the release of MAP Toolkit 8.0 Beta, we have added a new scenario to assess your Windows Azure Virtual Machine Readiness. The MAP 8.0 Beta performs a comprehensive assessment of Windows Servers running SQL Server to determine you level of readiness to migrate an on-premise physical or virtual machine to Windows Azure Virtual Machines. The MAP Toolkit then offers suggested changes to prepare the machines for migration, such as upgrading the operating system or SQL Server. MAP Toolkit 8.0 Beta is available for download here Your participation and feedback is very important to make the MAP Toolkit work better for you. We encourage you to participate in the beta program and provide your feedback at [email protected] or through one of our surveys. Now, let’s walk through the MAP Toolkit task for completing the Windows Azure Virtual Machine assessment and capacity planning. The tasks include the following: Perform an inventory View the Windows Azure VM Readiness results and report Collect performance data for determine VM sizing View the Windows Azure Capacity results and report Perform an inventory: 1. To perform an inventory against a single machine or across a complete environment, choose Perform an Inventory to launch the Inventory and Assessment Wizard as shown below: 2. After the Inventory and Assessment Wizard launches, select either the Windows computers or SQL Server scenario to inventory Windows machines. HINT: If you don’t care about completely inventorying a machine, just select the SQL Server scenario. Click Next to Continue. 3. On the Discovery Methods page, select how you want to discover computers and then click Next to continue. Description of Discovery Methods: Use Active Directory Domain Services -- This method allows you to query a domain controller via the Lightweight Directory Access Protocol (LDAP) and select computers in all or specific domains, containers, or OUs. Use this method if all computers and devices are in AD DS. Windows networking protocols --  This method uses the WIN32 LAN Manager application programming interfaces to query the Computer Browser service for computers in workgroups and Windows NT 4.0–based domains. If the computers on the network are not joined to an Active Directory domain, use only the Windows networking protocols option to find computers. System Center Configuration Manager (SCCM) -- This method enables you to inventory computers managed by System Center Configuration Manager (SCCM). You need to provide credentials to the System Center Configuration Manager server in order to inventory the managed computers. When you select this option, the MAP Toolkit will query SCCM for a list of computers and then MAP will connect to these computers. Scan an IP address range -- This method allows you to specify the starting address and ending address of an IP address range. The wizard will then scan all IP addresses in the range and inventory only those computers. Note: This option can perform poorly, if many IP addresses aren’t being used within the range. Manually enter computer names and credentials -- Use this method if you want to inventory a small number of specific computers. Import computer names from a files -- Using this method, you can create a text file with a list of computer names that will be inventoried. 4. On the All Computers Credentials page, enter the accounts that have administrator rights to connect to the discovered machines. This does not need to a domain account, but needs to be a local administrator. I have entered my domain account that is an administrator on my local machine. Click Next after one or more accounts have been added. NOTE: The MAP Toolkit primarily uses Windows Management Instrumentation (WMI) to collect hardware, device, and software information from the remote computers. In order for the MAP Toolkit to successfully connect and inventory computers in your environment, you have to configure your machines to inventory through WMI and also allow your firewall to enable remote access through WMI. The MAP Toolkit also requires remote registry access for certain assessments. In addition to enabling WMI, you need accounts with administrative privileges to access desktops and servers in your environment. 5. On the Credentials Order page, select the order in which want the MAP Toolkit to connect to the machine and SQL Server. Generally just accept the defaults and click Next. 6. On the Enter Computers Manually page, click Create to pull up at dialog to enter one or more computer names. 7. On the Summary page confirm your settings and then click Finish. After clicking Finish the inventory process will start, as shown below: Windows Azure Readiness results and report After the inventory progress has completed, you can review the results under the Database scenario. On the tile, you will see the number of Windows Server machine with SQL Server that were analyzed, the number of machines that are ready to move without changes and the number of machines that require further changes. If you click this Azure VM Readiness tile, you will see additional details and can generate the Windows Azure VM Readiness Report. After the report is generated, select View | Saved Reports and Proposals to view the location of the report. Open up WindowsAzureVMReadiness* report in Excel. On the Windows tab, you can see the results of the assessment. This report has a column for the Operating System and SQL Server assessment and provides a recommendation on how to resolve, if there a component is not supported. Collect Performance Data Launch the Performance Wizard to collect performance information for the Windows Server machines that you would like the MAP Toolkit to suggest a Windows Azure VM size for. Windows Azure Capacity results and report After the performance metrics are collected, the Azure VM Capacity title will display the number of Virtual Machine sizes that are suggested for the Windows Server and Linux machines that were analyzed. You can then click on the Azure VM Capacity tile to see the capacity details and generate the Windows Azure VM Capacity Report. Within this report, you can view the performance data that was collected and the Virtual Machine sizes.   MAP Toolkit 8.0 Beta is available for download here Your participation and feedback is very important to make the MAP Toolkit work better for you. We encourage you to participate in the beta program and provide your feedback at [email protected] or through one of our surveys. Useful References: Windows Azure Homepage How to guides for Windows Azure Virtual Machines Provisioning a SQL Server Virtual Machine on Windows Azure Windows Azure Pricing     Peter Saddow Senior Program Manager – MAP Toolkit Team

    Read the article

  • Windows Azure Virtual Machine Readiness and Capacity Assessment for SQL Server

    - by SQLOS Team
    Windows Azure Virtual Machine Readiness and Capacity Assessment for Windows Server Machine Running SQL Server With the release of MAP Toolkit 8.0 Beta, we have added a new scenario to assess your Windows Azure Virtual Machine Readiness. The MAP 8.0 Beta performs a comprehensive assessment of Windows Servers running SQL Server to determine you level of readiness to migrate an on-premise physical or virtual machine to Windows Azure Virtual Machines. The MAP Toolkit then offers suggested changes to prepare the machines for migration, such as upgrading the operating system or SQL Server. MAP Toolkit 8.0 Beta is available for download here Your participation and feedback is very important to make the MAP Toolkit work better for you. We encourage you to participate in the beta program and provide your feedback at [email protected] or through one of our surveys. Now, let’s walk through the MAP Toolkit task for completing the Windows Azure Virtual Machine assessment and capacity planning. The tasks include the following: Perform an inventory View the Windows Azure VM Readiness results and report Collect performance data for determine VM sizing View the Windows Azure Capacity results and report Perform an inventory: 1. To perform an inventory against a single machine or across a complete environment, choose Perform an Inventory to launch the Inventory and Assessment Wizard as shown below: 2. After the Inventory and Assessment Wizard launches, select either the Windows computers or SQL Server scenario to inventory Windows machines. HINT: If you don’t care about completely inventorying a machine, just select the SQL Server scenario. Click Next to Continue. 3. On the Discovery Methods page, select how you want to discover computers and then click Next to continue. Description of Discovery Methods: Use Active Directory Domain Services -- This method allows you to query a domain controller via the Lightweight Directory Access Protocol (LDAP) and select computers in all or specific domains, containers, or OUs. Use this method if all computers and devices are in AD DS. Windows networking protocols --  This method uses the WIN32 LAN Manager application programming interfaces to query the Computer Browser service for computers in workgroups and Windows NT 4.0–based domains. If the computers on the network are not joined to an Active Directory domain, use only the Windows networking protocols option to find computers. System Center Configuration Manager (SCCM) -- This method enables you to inventory computers managed by System Center Configuration Manager (SCCM). You need to provide credentials to the System Center Configuration Manager server in order to inventory the managed computers. When you select this option, the MAP Toolkit will query SCCM for a list of computers and then MAP will connect to these computers. Scan an IP address range -- This method allows you to specify the starting address and ending address of an IP address range. The wizard will then scan all IP addresses in the range and inventory only those computers. Note: This option can perform poorly, if many IP addresses aren’t being used within the range. Manually enter computer names and credentials -- Use this method if you want to inventory a small number of specific computers. Import computer names from a files -- Using this method, you can create a text file with a list of computer names that will be inventoried. 4. On the All Computers Credentials page, enter the accounts that have administrator rights to connect to the discovered machines. This does not need to a domain account, but needs to be a local administrator. I have entered my domain account that is an administrator on my local machine. Click Next after one or more accounts have been added. NOTE: The MAP Toolkit primarily uses Windows Management Instrumentation (WMI) to collect hardware, device, and software information from the remote computers. In order for the MAP Toolkit to successfully connect and inventory computers in your environment, you have to configure your machines to inventory through WMI and also allow your firewall to enable remote access through WMI. The MAP Toolkit also requires remote registry access for certain assessments. In addition to enabling WMI, you need accounts with administrative privileges to access desktops and servers in your environment. 5. On the Credentials Order page, select the order in which want the MAP Toolkit to connect to the machine and SQL Server. Generally just accept the defaults and click Next. 6. On the Enter Computers Manually page, click Create to pull up at dialog to enter one or more computer names. 7. On the Summary page confirm your settings and then click Finish. After clicking Finish the inventory process will start, as shown below: Windows Azure Readiness results and report After the inventory progress has completed, you can review the results under the Database scenario. On the tile, you will see the number of Windows Server machine with SQL Server that were analyzed, the number of machines that are ready to move without changes and the number of machines that require further changes. If you click this Azure VM Readiness tile, you will see additional details and can generate the Windows Azure VM Readiness Report. After the report is generated, select View | Saved Reports and Proposals to view the location of the report. Open up WindowsAzureVMReadiness* report in Excel. On the Windows tab, you can see the results of the assessment. This report has a column for the Operating System and SQL Server assessment and provides a recommendation on how to resolve, if there a component is not supported. Collect Performance Data Launch the Performance Wizard to collect performance information for the Windows Server machines that you would like the MAP Toolkit to suggest a Windows Azure VM size for. Windows Azure Capacity results and report After the performance metrics are collected, the Azure VM Capacity title will display the number of Virtual Machine sizes that are suggested for the Windows Server and Linux machines that were analyzed. You can then click on the Azure VM Capacity tile to see the capacity details and generate the Windows Azure VM Capacity Report. Within this report, you can view the performance data that was collected and the Virtual Machine sizes.   MAP Toolkit 8.0 Beta is available for download here Your participation and feedback is very important to make the MAP Toolkit work better for you. We encourage you to participate in the beta program and provide your feedback at [email protected] or through one of our surveys. Useful References: Windows Azure Homepage How to guides for Windows Azure Virtual Machines Provisioning a SQL Server Virtual Machine on Windows Azure Windows Azure Pricing     Peter Saddow Senior Program Manager – MAP Toolkit Team

    Read the article

  • Developer Capacity Planning

    - by Zaff
    What product or tool do you use to do Resource Capacity planning for your development team? Currently managing a large group and trying to provide visibility into my resource availability. I am creating this in MS project, but was curious if there was a better tool/solution based off your experience.

    Read the article

  • Uses for the capacity value of a string

    - by dreamlax
    In the C++ Standard Library, std::string has a public member function capacity() which returns the size of the internal allocated storage, a value greater than or equal to the number of characters in the string (according to here). What can this value be used for? Does it have something to do with custom allocators?

    Read the article

  • Is it possible to give a python dict an initial capacity (and is it usefull)

    - by Peter Smit
    I am filling a python dict with around 10,000,000 items. My understanding of dict (or hashtables) is that when too much elements get in them, the need to resize, an operation that cost quite some time. Is there a way to say to a python dict that you will be storing at least n items in it, so that it can allocate memory from the start? Or will this optimization not do any good to my running speed? (And no, I have not checked that the slowness of my small script is because of this, I actually wouldn't now how to do that. This is however something I would do in Java, set the initial capacity of the HashSet right)

    Read the article

  • ArrayBlockingQueue exceeds given capacity

    - by Wojciech Reszelewski
    I've written program solving bounded producer & consumer problem. While constructing ArrayBlockingQueue I defined capacity 100. I'm using methods take and put inside threads. And I've noticed that sometimes I see put 102 times with any take's between them. Why does it happen? Producer run method: public void run() { Object e = new Object(); while(true) { try { queue.put(e); } catch (InterruptedException w) { System.out.println("Oj, nie wyszlo, nie bij"); } System.out.println("Element added"); } } Consumer run method: public void run() { while(true) { try { queue.take(); } catch (InterruptedException e) { e.printStackTrace(); } System.out.println("Element removed"); } } Part of uniq -c on file with output: 102 Element removed 102 Element added 102 Element removed 102 Element added 102 Element removed 102 Element added 102 Element removed 102 Element added 102 Element removed 102 Element added 102 Element removed 102 Element added 2 Element removed 2 Element added 102 Element removed 102 Element added

    Read the article

  • Laptop battery charging capacity reduced to 52%

    - by omjaijagdish
    I have been using Ubuntu 11.04 on DELL Inspiron 14R (N5010) laptop for last three months. Before I switch to ubuntu my laptop battery used to give 2.5 hrs to 3 hrs back-up. But since I have been using ubuntu, it has been reduced to 1hr to 1.5 hrs at max. I tried following commands: $ cat /proc/acpi/battery/BAT0/state which gave result as present: yes capacity state: ok charging state: charged present rate: 1 mA remaining capacity: 4400 mAh present voltage: 12407 mV then I tried $ acpi -b the result was.. Battery 0: Unknown, 100% when I gave command as $ upower -i /org/freedesktop/UPower/devices/battery_BAT0 the result was.. native-path: /sys/devices/LNXSYSTM:00/device:00/PNP0C0A:00/power_supply/BAT0 model: DELL W7H3N08 serial: 7114 power supply: yes updated: Sat Nov 24 11:25:34 2012 (21 seconds ago) has history: yes has statistics: yes battery present: yes rechargeable: yes state: fully-charged energy: 48.4748 Wh energy-empty: 0 Wh energy-full: 48.4748 Wh energy-full-design: 48.9595 Wh energy-rate: 0.011017 W voltage: 12.408 V percentage: 100% **capacity: 52.9253%** technology: lithium-ion Someone please let me know, what is going wrong with my laptop? How can I get charging with full capacity?

    Read the article

  • Ubuntu reports low battery capacity on my Dell Vostro

    - by Jeff
    I have a Dell Vostro 1500. Before I wiped Windows XP off my hard drive in 2009, I had a full ~7 hrs battery capacity. I installed Ubuntu 9, and the capacity immediately dropped to about 27% (and has since decreased to about 11%). I couldn't figure out what to do, so I've just lived with the 20-30 minute battery life ever since. I upgraded to Ubuntu 10, and the issue remained. I wiped my hard drive clean again and installed Ubuntu 11, and the issue still remains. I tried what they told me in the forum here, but it didn't do anything. Is it possible for a battery to suddenly lose most of its capacity?? Or is there a bug in the power management software?

    Read the article

  • Traffic estimation for a multiplayer flash game

    - by Steve Addington
    hey, i want to know if my rough traffic estimations are right, it would be for a pretty simple realtime flashgame in the style of haxball (but not as a soccer game) heres a video of it http://www.youtube.com/watch?v=z_xBdFg1RcI So here comes my estimation, i dont know if they are realistic! i hope someone can help me. consider the packet attached as a typical one sent every 200ms, its 148bytes + 64 bytes of header will make around a 200bytes packet. The server will receive 200bytes x 6 players x 5 times a sec=6000bytes/s=5.85Kbytes/s=46.9kbit/s plus he has to send all back to the players, so at this point are 94Kbit/s.The server received all the information, perform the definitive calculation and send the new position to all players, in a bigger packet of around 900bytes that have to be delivered to the others 6, which makes 900bytes x 6 players x 5 times a sec=27000bytes/s=26Kbytes/s=210kbit/s. overall that would be 26kbyte per second. thats like 130mb traffic per hour for a 6player room. but somehow i think the numbers are too high? that would be really much traffic for such a simple game. did i calculate something wrong?

    Read the article

  • SQL Server Capacity Planner

    Apart from the capacity planner tool for System Center and SharePoint Server, I was looking for a tool which can help me to estimate the capacity of SQL Server. I found an article on Microsoft.com for SQL Server 2000 sizing but unfortunately the links are obseleted and dead: Dell PowerMatch Server Sizing Software Compaq Active Answer Resources Finally I found an article that is "close" to my interest: Hardware and Software Requirements for Installing SQL Server 2008 If any of you...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

    Read the article

  • SQLAuthority News Storage and SQL Server Capacity Planning and configuration SharePoint Server 201

    Just a day ago, I was asked how do you plan SQL Server Storage Capacity. Here is the excellent article published by Microsoft regarding SQL Server capacity planning for SharePoint 2010. This article touches all the vital areas of this subject. Here are the bullet points for the same. Gather storage and SQL Server space [...]...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

    Read the article

  • Google Adsense threshold estimation

    - by Wladimir Ivanov
    I've an electronic music blog with traffic mainly from the North American continent, Western Europe and Russia. Daily I get about 100 unique visitors with 150-200 pageviews. Should I start Adsense or I need to work to increase the traffic stats. Can you suggest another appropriate monetizing option for the given case? How much time It would take me to hit the 100$ Adsense barrier with the given traffic statistics? Thanks in advance.

    Read the article

  • PTLQueue : a scalable bounded-capacity MPMC queue

    - by Dave
    Title: Fast concurrent MPMC queue -- I've used the following concurrent queue algorithm enough that it warrants a blog entry. I'll sketch out the design of a fast and scalable multiple-producer multiple-consumer (MPSC) concurrent queue called PTLQueue. The queue has bounded capacity and is implemented via a circular array. Bounded capacity can be a useful property if there's a mismatch between producer rates and consumer rates where an unbounded queue might otherwise result in excessive memory consumption by virtue of the container nodes that -- in some queue implementations -- are used to hold values. A bounded-capacity queue can provide flow control between components. Beware, however, that bounded collections can also result in resource deadlock if abused. The put() and take() operators are partial and wait for the collection to become non-full or non-empty, respectively. Put() and take() do not allocate memory, and are not vulnerable to the ABA pathologies. The PTLQueue algorithm can be implemented equally well in C/C++ and Java. Partial operators are often more convenient than total methods. In many use cases if the preconditions aren't met, there's nothing else useful the thread can do, so it may as well wait via a partial method. An exception is in the case of work-stealing queues where a thief might scan a set of queues from which it could potentially steal. Total methods return ASAP with a success-failure indication. (It's tempting to describe a queue or API as blocking or non-blocking instead of partial or total, but non-blocking is already an overloaded concurrency term. Perhaps waiting/non-waiting or patient/impatient might be better terms). It's also trivial to construct partial operators by busy-waiting via total operators, but such constructs may be less efficient than an operator explicitly and intentionally designed to wait. A PTLQueue instance contains an array of slots, where each slot has volatile Turn and MailBox fields. The array has power-of-two length allowing mod/div operations to be replaced by masking. We assume sensible padding and alignment to reduce the impact of false sharing. (On x86 I recommend 128-byte alignment and padding because of the adjacent-sector prefetch facility). Each queue also has PutCursor and TakeCursor cursor variables, each of which should be sequestered as the sole occupant of a cache line or sector. You can opt to use 64-bit integers if concerned about wrap-around aliasing in the cursor variables. Put(null) is considered illegal, but the caller or implementation can easily check for and convert null to a distinguished non-null proxy value if null happens to be a value you'd like to pass. Take() will accordingly convert the proxy value back to null. An advantage of PTLQueue is that you can use atomic fetch-and-increment for the partial methods. We initialize each slot at index I with (Turn=I, MailBox=null). Both cursors are initially 0. All shared variables are considered "volatile" and atomics such as CAS and AtomicFetchAndIncrement are presumed to have bidirectional fence semantics. Finally T is the templated type. I've sketched out a total tryTake() method below that allows the caller to poll the queue. tryPut() has an analogous construction. Zebra stripping : alternating row colors for nice-looking code listings. See also google code "prettify" : https://code.google.com/p/google-code-prettify/ Prettify is a javascript module that yields the HTML/CSS/JS equivalent of pretty-print. -- pre:nth-child(odd) { background-color:#ff0000; } pre:nth-child(even) { background-color:#0000ff; } border-left: 11px solid #ccc; margin: 1.7em 0 1.7em 0.3em; background-color:#BFB; font-size:12px; line-height:65%; " // PTLQueue : Put(v) : // producer : partial method - waits as necessary assert v != null assert Mask = 1 && (Mask & (Mask+1)) == 0 // Document invariants // doorway step // Obtain a sequence number -- ticket // As a practical concern the ticket value is temporally unique // The ticket also identifies and selects a slot auto tkt = AtomicFetchIncrement (&PutCursor, 1) slot * s = &Slots[tkt & Mask] // waiting phase : // wait for slot's generation to match the tkt value assigned to this put() invocation. // The "generation" is implicitly encoded as the upper bits in the cursor // above those used to specify the index : tkt div (Mask+1) // The generation serves as an epoch number to identify a cohort of threads // accessing disjoint slots while s-Turn != tkt : Pause assert s-MailBox == null s-MailBox = v // deposit and pass message Take() : // consumer : partial method - waits as necessary auto tkt = AtomicFetchIncrement (&TakeCursor,1) slot * s = &Slots[tkt & Mask] // 2-stage waiting : // First wait for turn for our generation // Acquire exclusive "take" access to slot's MailBox field // Then wait for the slot to become occupied while s-Turn != tkt : Pause // Concurrency in this section of code is now reduced to just 1 producer thread // vs 1 consumer thread. // For a given queue and slot, there will be most one Take() operation running // in this section. // Consumer waits for producer to arrive and make slot non-empty // Extract message; clear mailbox; advance Turn indicator // We have an obvious happens-before relation : // Put(m) happens-before corresponding Take() that returns that same "m" for T v = s-MailBox if v != null : s-MailBox = null ST-ST barrier s-Turn = tkt + Mask + 1 // unlock slot to admit next producer and consumer return v Pause tryTake() : // total method - returns ASAP with failure indication for auto tkt = TakeCursor slot * s = &Slots[tkt & Mask] if s-Turn != tkt : return null T v = s-MailBox // presumptive return value if v == null : return null // ratify tkt and v values and commit by advancing cursor if CAS (&TakeCursor, tkt, tkt+1) != tkt : continue s-MailBox = null ST-ST barrier s-Turn = tkt + Mask + 1 return v The basic idea derives from the Partitioned Ticket Lock "PTL" (US20120240126-A1) and the MultiLane Concurrent Bag (US8689237). The latter is essentially a circular ring-buffer where the elements themselves are queues or concurrent collections. You can think of the PTLQueue as a partitioned ticket lock "PTL" augmented to pass values from lock to unlock via the slots. Alternatively, you could conceptualize of PTLQueue as a degenerate MultiLane bag where each slot or "lane" consists of a simple single-word MailBox instead of a general queue. Each lane in PTLQueue also has a private Turn field which acts like the Turn (Grant) variables found in PTL. Turn enforces strict FIFO ordering and restricts concurrency on the slot mailbox field to at most one simultaneous put() and take() operation. PTL uses a single "ticket" variable and per-slot Turn (grant) fields while MultiLane has distinct PutCursor and TakeCursor cursors and abstract per-slot sub-queues. Both PTL and MultiLane advance their cursor and ticket variables with atomic fetch-and-increment. PTLQueue borrows from both PTL and MultiLane and has distinct put and take cursors and per-slot Turn fields. Instead of a per-slot queues, PTLQueue uses a simple single-word MailBox field. PutCursor and TakeCursor act like a pair of ticket locks, conferring "put" and "take" access to a given slot. PutCursor, for instance, assigns an incoming put() request to a slot and serves as a PTL "Ticket" to acquire "put" permission to that slot's MailBox field. To better explain the operation of PTLQueue we deconstruct the operation of put() and take() as follows. Put() first increments PutCursor obtaining a new unique ticket. That ticket value also identifies a slot. Put() next waits for that slot's Turn field to match that ticket value. This is tantamount to using a PTL to acquire "put" permission on the slot's MailBox field. Finally, having obtained exclusive "put" permission on the slot, put() stores the message value into the slot's MailBox. Take() similarly advances TakeCursor, identifying a slot, and then acquires and secures "take" permission on a slot by waiting for Turn. Take() then waits for the slot's MailBox to become non-empty, extracts the message, and clears MailBox. Finally, take() advances the slot's Turn field, which releases both "put" and "take" access to the slot's MailBox. Note the asymmetry : put() acquires "put" access to the slot, but take() releases that lock. At any given time, for a given slot in a PTLQueue, at most one thread has "put" access and at most one thread has "take" access. This restricts concurrency from general MPMC to 1-vs-1. We have 2 ticket locks -- one for put() and one for take() -- each with its own "ticket" variable in the form of the corresponding cursor, but they share a single "Grant" egress variable in the form of the slot's Turn variable. Advancing the PutCursor, for instance, serves two purposes. First, we obtain a unique ticket which identifies a slot. Second, incrementing the cursor is the doorway protocol step to acquire the per-slot mutual exclusion "put" lock. The cursors and operations to increment those cursors serve double-duty : slot-selection and ticket assignment for locking the slot's MailBox field. At any given time a slot MailBox field can be in one of the following states: empty with no pending operations -- neutral state; empty with one or more waiting take() operations pending -- deficit; occupied with no pending operations; occupied with one or more waiting put() operations -- surplus; empty with a pending put() or pending put() and take() operations -- transitional; or occupied with a pending take() or pending put() and take() operations -- transitional. The partial put() and take() operators can be implemented with an atomic fetch-and-increment operation, which may confer a performance advantage over a CAS-based loop. In addition we have independent PutCursor and TakeCursor cursors. Critically, a put() operation modifies PutCursor but does not access the TakeCursor and a take() operation modifies the TakeCursor cursor but does not access the PutCursor. This acts to reduce coherence traffic relative to some other queue designs. It's worth noting that slow threads or obstruction in one slot (or "lane") does not impede or obstruct operations in other slots -- this gives us some degree of obstruction isolation. PTLQueue is not lock-free, however. The implementation above is expressed with polite busy-waiting (Pause) but it's trivial to implement per-slot parking and unparking to deschedule waiting threads. It's also easy to convert the queue to a more general deque by replacing the PutCursor and TakeCursor cursors with Left/Front and Right/Back cursors that can move either direction. Specifically, to push and pop from the "left" side of the deque we would decrement and increment the Left cursor, respectively, and to push and pop from the "right" side of the deque we would increment and decrement the Right cursor, respectively. We used a variation of PTLQueue for message passing in our recent OPODIS 2013 paper. ul { list-style:none; padding-left:0; padding:0; margin:0; margin-left:0; } ul#myTagID { padding: 0px; margin: 0px; list-style:none; margin-left:0;} -- -- There's quite a bit of related literature in this area. I'll call out a few relevant references: Wilson's NYU Courant Institute UltraComputer dissertation from 1988 is classic and the canonical starting point : Operating System Data Structures for Shared-Memory MIMD Machines with Fetch-and-Add. Regarding provenance and priority, I think PTLQueue or queues effectively equivalent to PTLQueue have been independently rediscovered a number of times. See CB-Queue and BNPBV, below, for instance. But Wilson's dissertation anticipates the basic idea and seems to predate all the others. Gottlieb et al : Basic Techniques for the Efficient Coordination of Very Large Numbers of Cooperating Sequential Processors Orozco et al : CB-Queue in Toward high-throughput algorithms on many-core architectures which appeared in TACO 2012. Meneghin et al : BNPVB family in Performance evaluation of inter-thread communication mechanisms on multicore/multithreaded architecture Dmitry Vyukov : bounded MPMC queue (highly recommended) Alex Otenko : US8607249 (highly related). John Mellor-Crummey : Concurrent queues: Practical fetch-and-phi algorithms. Technical Report 229, Department of Computer Science, University of Rochester Thomasson : FIFO Distributed Bakery Algorithm (very similar to PTLQueue). Scott and Scherer : Dual Data Structures I'll propose an optimization left as an exercise for the reader. Say we wanted to reduce memory usage by eliminating inter-slot padding. Such padding is usually "dark" memory and otherwise unused and wasted. But eliminating the padding leaves us at risk of increased false sharing. Furthermore lets say it was usually the case that the PutCursor and TakeCursor were numerically close to each other. (That's true in some use cases). We might still reduce false sharing by incrementing the cursors by some value other than 1 that is not trivially small and is coprime with the number of slots. Alternatively, we might increment the cursor by one and mask as usual, resulting in a logical index. We then use that logical index value to index into a permutation table, yielding an effective index for use in the slot array. The permutation table would be constructed so that nearby logical indices would map to more distant effective indices. (Open question: what should that permutation look like? Possibly some perversion of a Gray code or De Bruijn sequence might be suitable). As an aside, say we need to busy-wait for some condition as follows : "while C == 0 : Pause". Lets say that C is usually non-zero, so we typically don't wait. But when C happens to be 0 we'll have to spin for some period, possibly brief. We can arrange for the code to be more machine-friendly with respect to the branch predictors by transforming the loop into : "if C == 0 : for { Pause; if C != 0 : break; }". Critically, we want to restructure the loop so there's one branch that controls entry and another that controls loop exit. A concern is that your compiler or JIT might be clever enough to transform this back to "while C == 0 : Pause". You can sometimes avoid this by inserting a call to a some type of very cheap "opaque" method that the compiler can't elide or reorder. On Solaris, for instance, you could use :"if C == 0 : { gethrtime(); for { Pause; if C != 0 : break; }}". It's worth noting the obvious duality between locks and queues. If you have strict FIFO lock implementation with local spinning and succession by direct handoff such as MCS or CLH,then you can usually transform that lock into a queue. Hidden commentary and annotations - invisible : * And of course there's a well-known duality between queues and locks, but I'll leave that topic for another blog post. * Compare and contrast : PTLQ vs PTL and MultiLane * Equivalent : Turn; seq; sequence; pos; position; ticket * Put = Lock; Deposit Take = identify and reserve slot; wait; extract & clear; unlock * conceptualize : Distinct PutLock and TakeLock implemented as ticket lock or PTL Distinct arrival cursors but share per-slot "Turn" variable provides exclusive role-based access to slot's mailbox field put() acquires exclusive access to a slot for purposes of "deposit" assigns slot round-robin and then acquires deposit access rights/perms to that slot take() acquires exclusive access to slot for purposes of "withdrawal" assigns slot round-robin and then acquires withdrawal access rights/perms to that slot At any given time, only one thread can have withdrawal access to a slot at any given time, only one thread can have deposit access to a slot Permissible for T1 to have deposit access and T2 to simultaneously have withdrawal access * round-robin for the purposes of; role-based; access mode; access role mailslot; mailbox; allocate/assign/identify slot rights; permission; license; access permission; * PTL/Ticket hybrid Asymmetric usage ; owner oblivious lock-unlock pairing K-exclusion add Grant cursor pass message m from lock to unlock via Slots[] array Cursor performs 2 functions : + PTL ticket + Assigns request to slot in round-robin fashion Deconstruct protocol : explication put() : allocate slot in round-robin fashion acquire PTL for "put" access store message into slot associated with PTL index take() : Acquire PTL for "take" access // doorway step seq = fetchAdd (&Grant, 1) s = &Slots[seq & Mask] // waiting phase while s-Turn != seq : pause Extract : wait for s-mailbox to be full v = s-mailbox s-mailbox = null Release PTL for both "put" and "take" access s-Turn = seq + Mask + 1 * Slot round-robin assignment and lock "doorway" protocol leverage the same cursor and FetchAdd operation on that cursor FetchAdd (&Cursor,1) + round-robin slot assignment and dispersal + PTL/ticket lock "doorway" step waiting phase is via "Turn" field in slot * PTLQueue uses 2 cursors -- put and take. Acquire "put" access to slot via PTL-like lock Acquire "take" access to slot via PTL-like lock 2 locks : put and take -- at most one thread can access slot's mailbox Both locks use same "turn" field Like multilane : 2 cursors : put and take slot is simple 1-capacity mailbox instead of queue Borrow per-slot turn/grant from PTL Provides strict FIFO Lock slot : put-vs-put take-vs-take at most one put accesses slot at any one time at most one put accesses take at any one time reduction to 1-vs-1 instead of N-vs-M concurrency Per slot locks for put/take Release put/take by advancing turn * is instrumental in ... * P-V Semaphore vs lock vs K-exclusion * See also : FastQueues-excerpt.java dice-etc/queue-mpmc-bounded-blocking-circular-xadd/ * PTLQueue is the same as PTLQB - identical * Expedient return; ASAP; prompt; immediately * Lamport's Bakery algorithm : doorway step then waiting phase Threads arriving at doorway obtain a unique ticket number Threads enter in ticket order * In the terminology of Reed and Kanodia a ticket lock corresponds to the busy-wait implementation of a semaphore using an eventcount and a sequencer It can also be thought of as an optimization of Lamport's bakery lock was designed for fault-tolerance rather than performance Instead of spinning on the release counter, processors using a bakery lock repeatedly examine the tickets of their peers --

    Read the article

  • System Center Capacity Planner 2007

    - by Colt
    With a recent case that I need to design the system infrastructure as well as the hardware specification of a SharePoint farm for a client, so I go and find the SharePoint Capacity Planner (CP) 2007 to stimulate a user model.Before installting the SharePoint CP 2007, System Center CP is a prerequisite but unfortunity the Microsoft download page is _blank_:  Alternatively, I get the installer from a colleague. However, I face another problem while installing it: The installer has encountered an unexpected error installing this package. This may indicate a problem with the package. The error code is 2738.This issue is happened only in Vista, and the details and solution had been posted on TechNet: C:\Windows\System32\regsvr32 vbscript.dll I can download the SharePoint CP and continue my work now. :)

    Read the article

  • System Center Capacity Planner 2007

    With a recent case that I need to design the system infrastructure as well as the hardware specification of a SharePoint farm for a client, so I go and find the SharePoint Capacity Planner (CP) 2007 to stimulate a user model.Before installting the SharePoint CP 2007, System Center CP is a prerequisite but unfortunity the Microsoft download page is _blank_:  Alternatively, I get the installer from a colleague. However, I face another problem while installing it: The installer...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

    Read the article

  • New version: Sun Rack II capacity calculator

    - by uwes
    A new release of the Sun Rack II capacity calculator is available on eSTEP portal. The tool calculates all the data necessary (power requirements, BTU, number of rack units, needed power outlets etc.) while inserting the many different kind of HW equipment in aSun Rack II cabinet (version 1000 and 1200). It takes into consideration most of the available servers, storage devices, tapes, and Netra products. There are also a couple of third party products which are taken into account. The spreadsheet can be downloaded from eSTEP portal. URL: http://launch.oracle.com/ PIN: eSTEP_2011 The material can be found under tab eSTEP Download.

    Read the article

  • Release 51 of Sun Rack II capacity calculator available

    - by uwes
    A new release of the Sun Rack II capacity calculator is available on eSTEP portal. Just uploaded release 51 of the calculator. The following changes have been integrated: Added LOD date of 30 NOV 2014 for ST25xx M2 (NEP LOD – other customers LOD is 31 MAY 2014) Moved 7420 to EOL HW due to met LOD Bug correction : X4-2 and X4-2L weren’t working. Bug correction : ES1-24 RU are now correctly shown (2 ES1-24 only takes 1 RU) The tool calculates all the data necessary (power requirements, BTU, number of rack units, needed power outlets etc.) while inserting the many different kind of HW equipment in aSun Rack II cabinet (version 1000 and 1200). It takes into consideration most of the available servers, storage devices, tapes, and Netra products. There are also a couple of third party products which are taken into account. The spreadsheet can be downloaded from eSTEP portal. URL: http://launch.oracle.com/ PIN: eSTEP_2011

    Read the article

  • Is bigger capacity ram faster then smaller capacity ram for same clock and CL?

    - by didibus
    I know that bigger capacity hard-drives with the same RPM are faster then smaller capacity hard-drives. I was wondering if the same is true for ram. Given two ram clocked at 1600mhz and with identical CLs: 9-9-9-24. Is a 2x8 going to perform better then a 2x4 ? Note that I am not asking if having more ram will improve the performance of my PC, I'm asking if the bigger capacity ram performs better. Thank You.

    Read the article

  • Is bigger capacity ram faster then smaller capacity ram for same clock and CL? [migrated]

    - by didibus
    I know that bigger capacity hard-drives with the same RPM are faster then smaller capacity hard-drives. I was wondering if the same is true for ram. Given two ram clocked at 1600mhz and with identical CLs: 9-9-9-24. Is a 2x8 going to perform better then a 2x4 ? Note that I am not asking if having more ram will improve the performance of my PC, I'm asking if the bigger capacity ram performs better. Thank You.

    Read the article

facebook twitter digg google delicious technorati stumbleupon myspace wordpress linkedin gmail igoogle windows live tumblr viadeo yahoo buzz yahoo mail yahoo bookmarks favorites email print

< Previous Page | 1 2 3 4 5 6 7 8 9 10 11 12  | Next Page >