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  • What is the optimal number of threads for performing IO operations in java?

    - by marc
    In Goetz's "Java Concurrency in Practice", in a footnote on page 101, he writes "For computational problems like this that do not I/O and access no shared data, Ncpu or Ncpu+1 threads yield optimal throughput; more threads do not help, and may in fact degrade performance..." My question is, when performing I/O operations such as file writing, file reading, file deleting, etc, are there guidelines for the number of threads to use to achieve maximum performance? I understand this will be just a guide number, since disk speeds and a host of other factors play into this. Still, I'm wondering: can 20 threads write 1000 separate files to disk faster than 4 threads can on a 4-cpu machine?

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  • Problem with number/type of arguments passed to an overloaded c++ constructor wrapped with swig.

    - by MiKo
    I am trying to wrap a c++ class (let's call it "Spam") written by someone else with swig to expose it to Python. After solving several problems, I am able to import the module in python, but when I try to create an object of such class I obtain the following error: foo = Spam.Spam('abc',3) Traceback (most recent call last): File "<stdin>", line 1, in <module> File "Spam.py", line 96, in __init__ this = _Spam.new_Spam(*args) NotImplementedError: Wrong number of arguments for overloaded function 'new_Spam'. Possible C/C++ prototypes are: Spam(unsigned char *,unsigned long,bool,unsigned int,SSTree::io_action,char const *) Spam(unsigned char *,unsigned long,bool,unsigned int,SSTree::io_action) Spam(unsigned char *,unsigned long,bool,unsigned int) Spam(unsigned char *,unsigned long,bool) Spam(unsigned char *,unsigned long) Googling around, I realized that the error is probably caused by the type of the arguments and not by the number (which is quite confusing), but I still cannot identify. I suspect the problem lies in passing a string as the first argument, but have no idea on how to fix it (keep in mind that I know almost no c/c++).

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  • How to get the line number an xml element is on via the Java w3c dom api

    - by Benju
    Is there a way to lookup the line number that a given element is at in an xml file via the w3c dom api? My use case for this is that we have 30,000+ maps in kml/xml format. I wrote a unit test that iterates over each file found on the hard drive (about 17GB worth) and tests that it is parseable by our application. When it fails I throw an exception that contains the element instance that was considered "invalid". In order for our mapping department (nobody here knows how to program) to easily track down the typo we would like to log the line number of the element that caused the exception. Can anybody suggest a way to do this? Please note we are using the W3C dom api included in the Android 1.6 SDK.

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  • Regex - how to extract number which falls on specified ID?

    - by cbros2008
    I'm trying to extract the number '1' that appears on the line with the ID I'm feeding (i.e. 12072). I've been trying for the past 2 hours to get this regex to work but I'm at a loss. So far I've got 12072.*?(\d+)(?!.*\d) but this extracts me everything from 12072 to the 1. Here's the text: <td id="12072" scope="#999999" bgcolor="#999999" style="width: 65; color:#999999" align="center" onclick="DaySelect(this)" title="">1</td> <td id="12073" scope="#999999" bgcolor="#999999" style="width: 65; color:#999999" align="center" onclick="DaySelect(this)" title="">1</td> How can I match just the number 1 from the end of the line of the specified ID, surely there's a way to do this? Help would be highly appreciated.

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  • Reducing number of include files to reduce server load/speed up site?

    - by rein
    You can reduce the number of HTTP requests to speed up your site, such as css sprite images. I'm wondering does reducing the number of php includes/requires also speed up your site or reduce server load? For example, I have a index.php with <?php include './file.php'; ?> If instead I copy and paste the code from file.php and just put it into index.php, thus removing the include code, would it reduce the server load? This might make things less organized, but if it does reduce server load I might need to do that. For a small to medium sized site, I assume there might not be a difference, but how about for high traffic sites? Thanks in advance.

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  • How do i pass a number from a list as a parameter in scheme?

    - by wyatt
    I need to take a number from a list and convert it to a number so that i can pass it as a parameter. im trying to make a 1-bit adder in scheme. i've written the code for the or gate and the xor gate and also the half adder and now im trying to combine them all to make a full adder. im not sure if im going about it the right way. any input will be appreciated thank you. (define or-gate (lambda (a b) (if (= a 1) 1 (if (= b 1) 1 0)))) (define xor-gate (lambda (a b) (if (= a b) 0 1))) (define ha (lambda (a b) (list (xor-gate a b)(and-gate a b)))) (define fa (lambda (a b cin) (or-gate (cdr(ha cin (car (ha a b))))(cdr(ha a b))))) the issue i get when i run the program is that the half adder (ha) function outputs a list as a value and that makes the values incompatible with my other procedures because they require numbers and not lists. i feel like there is a simple solution but i dont know it.

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  • Using generics in dotnet for functions with any number of arguments?

    - by Zarigani
    I would like to have a function that can "wrap" any other function call. In this particular case, it would allow me to write some more generic transaction handling around some specific operations. I can write this for any particular number of arguments, e.g. for one argument: Public Shared Sub WrapFunc(Of T)(ByVal f As Action(Of T), ByVal arg As T) ' Test some stuff, start transaction f(arg) ' Test some stuff, end transaction End Sub ... but I was hoping to have this handle any number of arguments without having to have duplicate code for 0 args, 1 arg, 2 args, etc. Is there a way of doing this?

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  • how to cast an array of char into a single integer number?

    - by SepiDev
    Hi guys, i'm trying to read contents of PNG file. As you may know, all data is written in a 4-byte manner in png files, both text and numbers. so if we have number 35234 it is save in this way: [1000][1001][1010][0010]. but sometimes numbers are shorter, so the first bytes are zero, and when I read the array and cast it from char* to integer I get wrong number. for example [0000] [0000] [0001] [1011] sometimes numbers are misinterpreted as negative numbers and simetimes as zero! let me give you an intuitive example: char s_num[4] = {120, 80, 40, 1}; int t_num = 0; t_num = int(s_num); => 3215279148 ?????? the result should be 241 but the output is 3215279148? I wish I could explain my problem well! how can i cast such arrays into a single integer value?

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  • What to use to wait on a indeterminate number of tasks?

    - by Scott Chamberlain
    I am still fairly new to parallel computing so I am not too sure which tool to use for the job. I have a System.Threading.Tasks.Task that needs to wait for n number number of tasks to finish before starting. The tricky part is some of its dependencies may start after this task starts (You are guaranteed to never hit 0 dependent tasks until they are all done). Here is kind of what is happening Parent thread creates somewhere between 1 and (NUMBER_OF_CPU_CORES - 1) tasks. Parent thread creates task to be run when all of the worker tasks are finished. Parent thread creates a monitoring thread Monitoring thread may kill a worker task or spawn a new task depending on load. I can figure out everything up to step 4. How do I get the task from step 2 to wait to run until any new worker threads created in step 4 finish?

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  • How to turn this simple 10 digit hex number back into 8 digits?

    - by Babil
    The algorithm to convert input 8 digit hex number into 10 digit are following: Given that the 8 digit number is: '12 34 56 78' x1 = 1 * 16^8 * 2^3 x2 = 2 * 16^7 * 2^2 x3 = 3 * 16^6 * 2^1 x4 = 4 * 16^4 * 2^4 x5 = 5 * 16^3 * 2^3 x6 = 6 * 16^2 * 2^2 x7 = 7 * 16^1 * 2^1 x8 = 8 * 16^0 * 2^0 Final 10 digit hex is: = x1 + x2 + x3 + x4 + x5 + x6 + x7 + x8 = '08 86 42 98 E8' The problem is - how to go back to 8 digit hex from a given 10 digit hex (for example: 08 86 42 98 E8 to 12 34 56 78) Some sample input and output are following: input output 11 11 11 11 08 42 10 84 21 22 22 33 33 10 84 21 8C 63 AB CD 12 34 52 D8 D0 88 64 45 78 96 32 21 4E 84 98 62 FF FF FF FF 7B DE F7 BD EF

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  • When iterating over values, why does typeof(value) return "string" when value is a number? Javascrip

    - by Mark
    I'm using Google Chrome for this test: Contrary to intuition, the first loop alerts "string" 3 times, while the second loop alerts "number" 3 times. numarray = [1, 2, 3]; //for-each loop for(num in numarray) alert(typeof(num)); //standard loop for(i=0; i<numarray.length; i++) alert(typeof(numarray[i])); I was expecting both loops to alert "number" 3 times. How is the first loop implemented in Javascript? In other words, if the for-each is syntactic sugar, what is its equivalent using a standard loop? Also, is there some way to iterate over an object's namespace using a standard loop? I'm looking to touch every one of some object's methods and attributes using a loop of the second kind. I'm new to Javascript and any help is highly appreciated, thanks.

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  • Hudson's FindBugs plugin reports line number "-1" for bugs. Ideas?

    - by John B.
    Greetings, I have a simple test project set up in Hudson and the project's build process (a batch file) generates a findbugs.xml file. This is processed by Hudson's FindBugs plugin but it shows the line number of the bugs as "-1" instead of their actual line number. A coworker suggested I enable debug info for the compiler. I used the -g "Generate all debugging info" option for javac but nothing seemed to change. My build command is: javac -g -classpath C:\testWebApp1\src -d C:\testWebApp1\build C:\testWebApp1\src\*.java The only other thing in the build.bat file is a call to the FindBug tool (text UI). Here is what the FindBugs Plugin says about the first bug: File: GenerateHellos.java, Line: -1, Type: UUF_UNUSED_FIELD, Priority: Normal, Category: PERFORMANCE Any ideas? Thanks a ton!

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  • Python code to do csv file row entries comparison operations and count the number of times row value

    - by Venomancer
    have an excel based CSV file with two columns (or rows, Pythonically) that I am working on. What I need to do is to perform some operations so that I can compare the two data entries in each 'row'. To be more precise, one column has constant numbers all the way down, whereas the other column has varying values. So I need to count the number of times the varying column data entry values crosses the constant value on the other column. For example, fro the csv file i have two columns: Varying Column; Constant Column 24 25 26 25 crossed 27 25 26 25 25.5 25 23 25 crossed 26 25 crossed Thus, the varying column data entries have crossed 25 three times. I need to generate a code that can count the number of the crosses. Please do help out, Thanks.

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  • Count the number of emails each day in Outlook 2003?

    - by Mat Nadrofsky
    This is for a little pet project of mine. I want to write a program that does some email analytics and tells you the number of emails coming in and out each day, as well as your percentages. Really, all I need to do to kick this off is write a .Net app that can talk with Outlook and count the number of messages received and sent for give dates. Before I got too deep into this, I figured I'd poll the group and see if there is a particular approach I should follow when starting something like this. Any thoughts?

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  • how to select specific number of child entities instead of all in entity framework 3.5?

    - by Sasha
    Hi all, i am wondering how can i select specific number of child objects instead of taking them all with include? lets say i have object 'Group' and i need to select last ten students that joined the group. When i use '.Include("Students"), EF includes all students. I was trying to use Take(10), but i am pretty new to EF and programming as well, so i couldn't figure it out. Any suggestions? UPDATED: ok, i have Group object already retrieved from db like this: Group group = db.Groups.FirstOrDefault(x=>x.GroupId == id) I know that i can add Include("Students") statement, but that would bring ALL students, and their number could be quite big whether i need only freshest 10 students. Can i do something like this: var groupWithStudents = group.Students.OrderByDescending(//...).Take(10);? The problem with this is that Take< no longer appears in intellisense. Is this clear enough? Thanks for responses

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  • Find first cell in a row that contains a number?

    - by Dexter
    I'm working in Excel with an exported table such as this: |-------------------------------------------------------------------------------| | | A | B | C | D | E | F | G | H | I | |---|-------------------|-----|-----|-----|-----|-----|-------|-----|-----------| | 1 | Domain | JAN | FEB | MAR | APR | MAY | Start | End | Change | |---|-------------------|-----|-----|-----|-----|-----|-------|-----|-----------| | 2 | www.mydomain1.com | | 1 | 4 | 3 | 1 | 1 | 1 | 0 | |---|-------------------|-----|-----|-----|-----|-----|-------|-----|-----------| | 3 | www.mydomain2.com | 2 | 4 | 12 | 18 | 23 | 2 | 23 | 21 | |---|-------------------|-----|-----|-----|-----|-----|-------|-----|-----------| | 4 | www.mydomain3.com | | | 14 | 12 | | 14 | xxx | NOT FOUND | |-------------------------------------------------------------------------------| I'm trying to compare the current state (last cell) to the original cell (first cell with a value). In column I, I have the formula =IF(G2 = "xxx", "NOT FOUND", IF(H2 = "xxx", "NOT FOUND", H2 - G2)) In column H, I have the formula =IF(F2 = "", "xxx", F2) In column G, I need to find the first cell with a number. If there isn't one in that range, I need G to be "xxx". I suppose I only need to check for the first cell in the range (B2 to F2) that contains a value, not just a number. I tried using an Index and Match combo, but I couldn't quite understand it.

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  • Number 0 is not saving to database as a prefix in SQL Server of CHAR data type column

    - by gmhk
    I am trying to insert an value as '019393' into a table with a CHAR(10) column. It is inserting only '19393' into the database I am implementing this feature in a stored procedure, doing some manipulation like incrementing that number by 15 and saving it back with '0' as the prefix I am using SQL Server database Note: I tried CASTING that value as VARCHAR before saving to the database, but even that did not get the solution Code SELECT @fromBSB = fromBSB, @toBSB = toBSB, @type = Type FROM [dbo].[tbl_REF_SpecialBSBRanges] WHERE CAST(@inputFromBSB AS INT) BETWEEN fromBSB AND toBSB SET @RETURNVALUE = @fromBSB IF(@fromBSB = @inputFromBSB) BEGIN PRINT 'Starting Number is Equal'; DELETE FROM tbl_REF_SpecialBSBRanges WHERE Type = @type AND fromBSB = @fromBSB AND toBSB = @toBSB INSERT INTO [tbl_REF_SpecialBSBRanges] ([Type], [fromBSB], [toBSB]) VALUES(@type, CAST('0' + @fromBSB + 1 AS CHAR), @toBSB) INSERT INTO [tbl_REF_SpecialBSBRanges] ([Type], [fromBSB], [toBSB]) VALUES(@inputBSBName, @inputFromBSB, @inputToBSB) END

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  • SPARC T4-4 Beats 8-CPU IBM POWER7 on TPC-H @3000GB Benchmark

    - by Brian
    Oracle's SPARC T4-4 server delivered a world record TPC-H @3000GB benchmark result for systems with four processors. This result beats eight processor results from IBM (POWER7) and HP (x86). The SPARC T4-4 server also delivered better performance per core than these eight processor systems from IBM and HP. Comparisons below are based upon system to system comparisons, highlighting Oracle's complete software and hardware solution. This database world record result used Oracle's Sun Storage 2540-M2 arrays (rotating disk) connected to a SPARC T4-4 server running Oracle Solaris 11 and Oracle Database 11g Release 2 demonstrating the power of Oracle's integrated hardware and software solution. The SPARC T4-4 server based configuration achieved a TPC-H scale factor 3000 world record for four processor systems of 205,792 QphH@3000GB with price/performance of $4.10/QphH@3000GB. The SPARC T4-4 server with four SPARC T4 processors (total of 32 cores) is 7% faster than the IBM Power 780 server with eight POWER7 processors (total of 32 cores) on the TPC-H @3000GB benchmark. The SPARC T4-4 server is 36% better in price performance compared to the IBM Power 780 server on the TPC-H @3000GB Benchmark. The SPARC T4-4 server is 29% faster than the IBM Power 780 for data loading. The SPARC T4-4 server is up to 3.4 times faster than the IBM Power 780 server for the Refresh Function. The SPARC T4-4 server with four SPARC T4 processors is 27% faster than the HP ProLiant DL980 G7 server with eight x86 processors on the TPC-H @3000GB benchmark. The SPARC T4-4 server is 52% faster than the HP ProLiant DL980 G7 server for data loading. The SPARC T4-4 server is up to 3.2 times faster than the HP ProLiant DL980 G7 for the Refresh Function. The SPARC T4-4 server achieved a peak IO rate from the Oracle database of 17 GB/sec. This rate was independent of the storage used, as demonstrated by the TPC-H @3000TB benchmark which used twelve Sun Storage 2540-M2 arrays (rotating disk) and the TPC-H @1000TB benchmark which used four Sun Storage F5100 Flash Array devices (flash storage). [*] The SPARC T4-4 server showed linear scaling from TPC-H @1000GB to TPC-H @3000GB. This demonstrates that the SPARC T4-4 server can handle the increasingly larger databases required of DSS systems. [*] The SPARC T4-4 server benchmark results demonstrate a complete solution of building Decision Support Systems including data loading, business questions and refreshing data. Each phase usually has a time constraint and the SPARC T4-4 server shows superior performance during each phase. [*] The TPC believes that comparisons of results published with different scale factors are misleading and discourages such comparisons. Performance Landscape The table lists the leading TPC-H @3000GB results for non-clustered systems. TPC-H @3000GB, Non-Clustered Systems System Processor P/C/T – Memory Composite(QphH) $/perf($/QphH) Power(QppH) Throughput(QthH) Database Available SPARC Enterprise M9000 3.0 GHz SPARC64 VII+ 64/256/256 – 1024 GB 386,478.3 $18.19 316,835.8 471,428.6 Oracle 11g R2 09/22/11 SPARC T4-4 3.0 GHz SPARC T4 4/32/256 – 1024 GB 205,792.0 $4.10 190,325.1 222,515.9 Oracle 11g R2 05/31/12 SPARC Enterprise M9000 2.88 GHz SPARC64 VII 32/128/256 – 512 GB 198,907.5 $15.27 182,350.7 216,967.7 Oracle 11g R2 12/09/10 IBM Power 780 4.1 GHz POWER7 8/32/128 – 1024 GB 192,001.1 $6.37 210,368.4 175,237.4 Sybase 15.4 11/30/11 HP ProLiant DL980 G7 2.27 GHz Intel Xeon X7560 8/64/128 – 512 GB 162,601.7 $2.68 185,297.7 142,685.6 SQL Server 2008 10/13/10 P/C/T = Processors, Cores, Threads QphH = the Composite Metric (bigger is better) $/QphH = the Price/Performance metric in USD (smaller is better) QppH = the Power Numerical Quantity QthH = the Throughput Numerical Quantity The following table lists data load times and refresh function times during the power run. TPC-H @3000GB, Non-Clustered Systems Database Load & Database Refresh System Processor Data Loading(h:m:s) T4Advan RF1(sec) T4Advan RF2(sec) T4Advan SPARC T4-4 3.0 GHz SPARC T4 04:08:29 1.0x 67.1 1.0x 39.5 1.0x IBM Power 780 4.1 GHz POWER7 05:51:50 1.5x 147.3 2.2x 133.2 3.4x HP ProLiant DL980 G7 2.27 GHz Intel Xeon X7560 08:35:17 2.1x 173.0 2.6x 126.3 3.2x Data Loading = database load time RF1 = power test first refresh transaction RF2 = power test second refresh transaction T4 Advan = the ratio of time to T4 time Complete benchmark results found at the TPC benchmark website http://www.tpc.org. Configuration Summary and Results Hardware Configuration: SPARC T4-4 server 4 x SPARC T4 3.0 GHz processors (total of 32 cores, 128 threads) 1024 GB memory 8 x internal SAS (8 x 300 GB) disk drives External Storage: 12 x Sun Storage 2540-M2 array storage, each with 12 x 15K RPM 300 GB drives, 2 controllers, 2 GB cache Software Configuration: Oracle Solaris 11 11/11 Oracle Database 11g Release 2 Enterprise Edition Audited Results: Database Size: 3000 GB (Scale Factor 3000) TPC-H Composite: 205,792.0 QphH@3000GB Price/performance: $4.10/QphH@3000GB Available: 05/31/2012 Total 3 year Cost: $843,656 TPC-H Power: 190,325.1 TPC-H Throughput: 222,515.9 Database Load Time: 4:08:29 Benchmark Description The TPC-H benchmark is a performance benchmark established by the Transaction Processing Council (TPC) to demonstrate Data Warehousing/Decision Support Systems (DSS). TPC-H measurements are produced for customers to evaluate the performance of various DSS systems. These queries and updates are executed against a standard database under controlled conditions. Performance projections and comparisons between different TPC-H Database sizes (100GB, 300GB, 1000GB, 3000GB, 10000GB, 30000GB and 100000GB) are not allowed by the TPC. TPC-H is a data warehousing-oriented, non-industry-specific benchmark that consists of a large number of complex queries typical of decision support applications. It also includes some insert and delete activity that is intended to simulate loading and purging data from a warehouse. TPC-H measures the combined performance of a particular database manager on a specific computer system. The main performance metric reported by TPC-H is called the TPC-H Composite Query-per-Hour Performance Metric (QphH@SF, where SF is the number of GB of raw data, referred to as the scale factor). QphH@SF is intended to summarize the ability of the system to process queries in both single and multiple user modes. The benchmark requires reporting of price/performance, which is the ratio of the total HW/SW cost plus 3 years maintenance to the QphH. A secondary metric is the storage efficiency, which is the ratio of total configured disk space in GB to the scale factor. Key Points and Best Practices Twelve Sun Storage 2540-M2 arrays were used for the benchmark. Each Sun Storage 2540-M2 array contains 12 15K RPM drives and is connected to a single dual port 8Gb FC HBA using 2 ports. Each Sun Storage 2540-M2 array showed 1.5 GB/sec for sequential read operations and showed linear scaling, achieving 18 GB/sec with twelve Sun Storage 2540-M2 arrays. These were stand alone IO tests. The peak IO rate measured from the Oracle database was 17 GB/sec. Oracle Solaris 11 11/11 required very little system tuning. Some vendors try to make the point that storage ratios are of customer concern. However, storage ratio size has more to do with disk layout and the increasing capacities of disks – so this is not an important metric in which to compare systems. The SPARC T4-4 server and Oracle Solaris efficiently managed the system load of over one thousand Oracle Database parallel processes. Six Sun Storage 2540-M2 arrays were mirrored to another six Sun Storage 2540-M2 arrays on which all of the Oracle database files were placed. IO performance was high and balanced across all the arrays. The TPC-H Refresh Function (RF) simulates periodical refresh portion of Data Warehouse by adding new sales and deleting old sales data. Parallel DML (parallel insert and delete in this case) and database log performance are a key for this function and the SPARC T4-4 server outperformed both the IBM POWER7 server and HP ProLiant DL980 G7 server. (See the RF columns above.) See Also Transaction Processing Performance Council (TPC) Home Page Ideas International Benchmark Page SPARC T4-4 Server oracle.com OTN Oracle Solaris oracle.com OTN Oracle Database 11g Release 2 Enterprise Edition oracle.com OTN Sun Storage 2540-M2 Array oracle.com OTN Disclosure Statement TPC-H, QphH, $/QphH are trademarks of Transaction Processing Performance Council (TPC). For more information, see www.tpc.org. SPARC T4-4 205,792.0 QphH@3000GB, $4.10/QphH@3000GB, available 5/31/12, 4 processors, 32 cores, 256 threads; IBM Power 780 QphH@3000GB, 192,001.1 QphH@3000GB, $6.37/QphH@3000GB, available 11/30/11, 8 processors, 32 cores, 128 threads; HP ProLiant DL980 G7 162,601.7 QphH@3000GB, $2.68/QphH@3000GB available 10/13/10, 8 processors, 64 cores, 128 threads.

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