Search Results

Search found 11153 results on 447 pages for 'count zero'.

Page 1/447 | 1 2 3 4 5 6 7 8 9 10 11 12  | Next Page >

  • why i7-860 is two times slower than E3-1220?

    - by javapowered
    I have financical trading software. It decodes fast/fix messages. I'm running same binaries on two different machines on very similar set of data. Software receive "messages" and decodes them. The general rule - longer message takes more time to decode: i7-860, Windows 7: Debug 18:23:48.8047325 count=51 decoding take microseconds = 300 Debug 18:23:49.7287854 count=53 decoding take microseconds = 349 Debug 18:23:49.7397860 count=110 decoding take microseconds = 516 Debug 18:23:49.7497866 count=92 decoding take microseconds = 512 Debug 18:23:49.7597872 count=49 decoding take microseconds = 267 Debug 18:23:49.7717878 count=194 decoding take microseconds = 823 Debug 18:23:49.7797883 count=49 decoding take microseconds = 296 Debug 18:23:49.7997894 count=50 decoding take microseconds = 299 Debug 18:23:50.7328428 count=101 decoding take microseconds = 583 Debug 18:23:50.7418433 count=42 decoding take microseconds = 281 Debug 18:23:50.7538440 count=151 decoding take microseconds = 764 Debug 18:23:50.7618445 count=57 decoding take microseconds = 279 Debug 18:23:50.7738452 count=122 decoding take microseconds = 712 Debug 18:23:50.8028468 count=52 decoding take microseconds = 281 Debug 18:23:51.7389004 count=137 decoding take microseconds = 696 Debug 18:23:51.7499010 count=100 decoding take microseconds = 485 Debug 18:23:51.7689021 count=185 decoding take microseconds = 872 Debug 18:23:51.8079043 count=49 decoding take microseconds = 315 Debug 18:23:52.7349573 count=90 decoding take microseconds = 532 Debug 18:23:52.7439578 count=53 decoding take microseconds = 277 Debug 18:23:52.7539584 count=134 decoding take microseconds = 623 Debug 18:23:52.7629589 count=47 decoding take microseconds = 294 Debug 18:23:52.7749596 count=198 decoding take microseconds = 868 Debug 18:23:52.8039613 count=52 decoding take microseconds = 291 Debug 18:23:53.7400148 count=132 decoding take microseconds = 666 Debug 18:23:53.7480153 count=81 decoding take microseconds = 430 Debug 18:23:53.7570158 count=49 decoding take microseconds = 301 Debug 18:23:53.7710166 count=156 decoding take microseconds = 752 Debug 18:23:53.7770169 count=45 decoding take microseconds = 270 Debug 18:23:54.7350717 count=108 decoding take microseconds = 578 Debug 18:23:54.7430722 count=52 decoding take microseconds = 286 Debug 18:23:54.7540728 count=138 decoding take microseconds = 567 Debug 18:23:54.7760741 count=160 decoding take microseconds = 753 Debug 18:23:54.8030756 count=53 decoding take microseconds = 292 Debug 18:23:55.7411293 count=110 decoding take microseconds = 629 Debug 18:23:55.7481297 count=48 decoding take microseconds = 294 Debug 18:23:55.7591303 count=84 decoding take microseconds = 386 Debug 18:23:55.7701309 count=90 decoding take microseconds = 484 Debug 18:23:55.7801315 count=120 decoding take microseconds = 527 Debug 18:23:55.8101332 count=53 decoding take microseconds = 290 Debug 18:23:56.7341861 count=121 decoding take microseconds = 667 Debug 18:23:56.7421865 count=53 decoding take microseconds = 293 Debug 18:23:56.7531872 count=127 decoding take microseconds = 586 Debug 18:23:56.7621877 count=58 decoding take microseconds = 306 Debug 18:23:56.7751884 count=138 decoding take microseconds = 649 Debug 18:23:56.8021900 count=53 decoding take microseconds = 288 Debug 18:23:57.7392436 count=139 decoding take microseconds = 699 Debug 18:23:57.7502442 count=121 decoding take microseconds = 548 Debug 18:23:57.7582446 count=61 decoding take microseconds = 301 Debug 18:23:57.7692453 count=98 decoding take microseconds = 500 Debug 18:23:57.7792458 count=94 decoding take microseconds = 460 Debug 18:23:57.8092476 count=41 decoding take microseconds = 274 Xeon E3-1220, Windows Server 2008 R2 foundation: Debug 18:28:57.5087967 count=117 decoding take microseconds = 255 Debug 18:28:57.5087967 count=85 decoding take microseconds = 187 Debug 18:28:57.5087967 count=55 decoding take microseconds = 155 Debug 18:28:57.5243967 count=86 decoding take microseconds = 189 Debug 18:28:57.5243967 count=53 decoding take microseconds = 139 Debug 18:28:57.5243967 count=52 decoding take microseconds = 153 Debug 18:28:57.5243967 count=55 decoding take microseconds = 146 Debug 18:28:57.5243967 count=103 decoding take microseconds = 239 Debug 18:28:57.5243967 count=83 decoding take microseconds = 182 Debug 18:28:57.5243967 count=85 decoding take microseconds = 180 Debug 18:28:57.5243967 count=80 decoding take microseconds = 202 Debug 18:28:57.5243967 count=58 decoding take microseconds = 135 Debug 18:28:57.5243967 count=55 decoding take microseconds = 140 Debug 18:28:57.5243967 count=81 decoding take microseconds = 183 Debug 18:28:57.5243967 count=74 decoding take microseconds = 172 Debug 18:28:57.5243967 count=80 decoding take microseconds = 174 Debug 18:28:57.5243967 count=88 decoding take microseconds = 175 Debug 18:28:57.5243967 count=55 decoding take microseconds = 131 Debug 18:28:57.5243967 count=80 decoding take microseconds = 182 Debug 18:28:57.5243967 count=80 decoding take microseconds = 183 Debug 18:28:57.5243967 count=101 decoding take microseconds = 231 Debug 18:28:57.5243967 count=58 decoding take microseconds = 134 Debug 18:28:57.5243967 count=57 decoding take microseconds = 126 Debug 18:28:57.5243967 count=57 decoding take microseconds = 134 Debug 18:28:57.5399967 count=115 decoding take microseconds = 234 Debug 18:28:57.5399967 count=106 decoding take microseconds = 225 Debug 18:28:57.5399967 count=108 decoding take microseconds = 241 Debug 18:28:57.5399967 count=84 decoding take microseconds = 177 Debug 18:28:57.5399967 count=54 decoding take microseconds = 141 Debug 18:28:57.5399967 count=84 decoding take microseconds = 186 Debug 18:28:57.5399967 count=82 decoding take microseconds = 184 Debug 18:28:57.5399967 count=82 decoding take microseconds = 179 Debug 18:28:57.5399967 count=56 decoding take microseconds = 133 Debug 18:28:57.5399967 count=57 decoding take microseconds = 127 Debug 18:28:57.5399967 count=82 decoding take microseconds = 185 Debug 18:28:57.5399967 count=76 decoding take microseconds = 178 Debug 18:28:57.5399967 count=82 decoding take microseconds = 184 Debug 18:28:57.5399967 count=54 decoding take microseconds = 139 Debug 18:28:57.5399967 count=54 decoding take microseconds = 137 Debug 18:28:57.5399967 count=81 decoding take microseconds = 184 Debug 18:28:57.5399967 count=136 decoding take microseconds = 275 Debug 18:28:57.5399967 count=55 decoding take microseconds = 138 Debug 18:28:57.5555968 count=52 decoding take microseconds = 140 Debug 18:28:57.5555968 count=53 decoding take microseconds = 136 Debug 18:28:57.5555968 count=54 decoding take microseconds = 139 Debug 18:28:57.5555968 count=55 decoding take microseconds = 138 Debug 18:28:57.5555968 count=57 decoding take microseconds = 134 Debug 18:28:57.5555968 count=53 decoding take microseconds = 136 Debug 18:28:57.5555968 count=80 decoding take microseconds = 174 Debug 18:28:57.5555968 count=74 decoding take microseconds = 175 Debug 18:28:57.5555968 count=57 decoding take microseconds = 133 Debug 18:28:57.5555968 count=57 decoding take microseconds = 149 Debug 18:28:57.5555968 count=100 decoding take microseconds = 262 Debug 18:28:57.5555968 count=56 decoding take microseconds = 156 Debug 18:28:57.5555968 count=55 decoding take microseconds = 165 From this test I see that E3-1220 is almost two times faster than i7-860. Is that possible? Because in the processors ratings these processors are about the same. Is it possible that this is because of cache or something? And if so which processor I better to buy to decode messages two more times faster?

    Read the article

  • SQL for total count and count within that where condition is true

    - by twmulloy
    Hello, I have a single user table and I'm trying to come up with a query that returns the total count of all users grouped by date along with the total count of users grouped by date who are of a specific client. Here is what I have thus far, where there's the total count of users grouped by date, but can't seem to figure out how to get the count of those users where user.client_id = x SELECT user.created, COUNT(user.id) AS overall_count FROM user GROUP BY DATE(user.created) trying for a row result like this: [created] => 2010-05-15 19:59:30 [overall_count] => 10 [client_count] => (some fraction of overall count, the number of users where user.client_id = x grouped by date)

    Read the article

  • A Review of From Zero To SSIS Training

    - by andyleonard
    I recently (5-9 Mar 2012) delivered my five-day SSIS training course – From Zero To SSIS! – in London. The class was delivered in collaboration with TechniTrain . I must commend Chris Webb ( blog | @Technitrain ) and Helen Lau on their leadership, professionalism, and attention to detail. They made the course a breeze for the students and the instructor! It was a pleasure and privilege to work with them. In addition to people just learning data integration, this class contained several experienced...(read more)

    Read the article

  • SQL SERVER – Difference between COUNT(DISTINCT) vs COUNT(ALL)

    - by pinaldave
    This blog post is written in response to the T-SQL Tuesday hosted by Jes Schultz Borland. Earlier today, I was presenting a 45-minute session at the Community College about “The Beginning SQL Server Database”. One of the students asked me the following question. What is the difference between COUNT(DISTINCT) vs COUNT(ALL)? I found this question from the student very interesting. He seems to have read the documentation (Book Online) and was then asking me this question. I always carry laptop which has SQL Server installed. I quickly opened it and ran the following script. After looking at the result, I think it was clear to everybody. Here is the script: SELECT COUNT([Title]) Value FROM [AdventureWorks].[Person].[Contact] GO SELECT COUNT(ALL [Title]) ALLValue FROM [AdventureWorks].[Person].[Contact] GO SELECT COUNT(DISTINCT [Title]) DistinctValue FROM [AdventureWorks].[Person].[Contact] GO The above script will give me the following results. You can clearly notice from the result set that COUNT (ALL ColumnName) is the same as COUNT(ColumnName). The reality is that the “ALL” is actually  the default option and it needs not to be specified. The ALL keyword includes all the non-NULL values. I know this is very simple and may be it does not change how we work; however looking at the whole angle, I really enjoyed the question. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, SQLAuthority News, T SQL, Technology

    Read the article

  • How to JOIN a COUNT from a table, and then effect that COUNT with another JOIN

    - by jakenoble
    Hi I have three tables Post ID Name 1 'Something' 2 'Something else' 3 'One more' Comment ID PostId ProfileID Comment 1 1 1 'Hi my name is' 2 2 2 'I like cakes' 3 3 3 'I hate cakes' Profile ID Approved 1 1 2 0 3 1 I want to count the comments for a post where the profile for the comment is approved I can select the data from Post and then join a count from Comment fine. But this count should be dependent on if the Profile is approved or not. The results I am expecting is CommentCount PostId Count 1 1 2 0 3 1 Thanks for any help.

    Read the article

  • SQL COUNT of COUNT

    - by cryptic-star
    I have some data I am querying. The table is composed of two columns - a unique ID, and a value. I would like to count the number of times each unique value appears (which can easily be done with a COUNT and GROUP BY), but I then want to be able to count that. So, I would like to see how many items appear twice, three times, etc. So for the following data (ID, val)... 1, 2 2, 2 3, 1 4, 2 5, 1 6, 7 7, 1 The intermediate step would be (val, count)... 1, 3 2, 3 7, 1 And I would like to have(count_from_above, new_count)... 3, 2 -- since three appears twice in the previous table 1, 1 -- since one appears once in the previous table Is there any query which can do that? If it helps, I'm working with Postgres. Thanks!

    Read the article

  • DBMS agnostic - What to name the COUNT column from a SQL Query

    - by cyberkiwi
    I have trouble naming the COUNT() column from SQL queries and will swap between various variants _Count [Count] (sql, or "count" or backticks for MySQL etc) C Cnt CountSomething (where "something" is the field being counted, or "CountAll") NoOfRows RowCount etc Has anyone come up with any name that you are happy with and always use without hesitation? This is bothering me because after joining SO just recently, my answers have shown this tendency of flip-flopping with no consistency. I need to get this sorted. Please help. (While we're at it, what do you use for SUM etc?) Note: Before you close this question, consider that this one was not: What's the best name for a non-mutating “add” method on an immutable collection?

    Read the article

  • How to perform COUNT() or COUNT(*)

    - by ninumedia
    I have a list of tags in a database. Ex: villan hero spiderman superman superman I wanted to obtain a sorted list of the tag names in ascending order and the number of times the unique tag appeared in the database. I wrote this code: Ex: SELECT hashtag.tag_name, COUNT( * ) AS number FROM hashtag GROUP BY hashtag.tag_name ORDER BY hashtag.tag_name ASC This yields the correct result: hero - 1 spiderman - 1 superman - 2 villan - 1 How can I obtain the full COUNT of this entire list. The answer should be 4 in this case because there are naturally 4 rows. I can't seem to get a correct COUNT() without the statement failing. Thanks so much for the help! :)

    Read the article

  • Count(*) vs Count(1)

    - by Nai
    Hi, just wondering if any of you guys use Count(1) over Count(*) and if there is a noticeable difference for SQL Server 2005 in performance? Or is this just a legacy habit that has been brought forward from days gone past?

    Read the article

  • Count a row VS Save the Row count after each update

    - by SAFAD
    I want to know whether saving row count in a table is better than counting it each time of the proccess. Quick Example : A visitor goes to Group Clan, the page displays clan information and Members who have joined the group,Should the page look for all the users who joined the clan and count them, or just display the number of members already saved in table ? I think the first one is not possible to get manipulated with but IT MIGHT cost performance Your Ideas ?

    Read the article

  • How to subtract 1 from a orginal count in an ASP.NET gridview

    - by SAMIR BHOGAYTA
    I have a gridview that contains a count (whic is Quantity) were i have a button that adds a row under the orginal row and i need the sub row's count (Quantity) to subtract one from the orgianl row Quantity. EX: Before button click Orgianl row = 3 After click Orginal row = 2 Subrow = 1 Code: ASP.NET // FUNCTION : Adds a new subrow protected void gvParent_RowCommand(object sender, GridViewCommandEventArgs e) { if (e.CommandName.Equals("btn_AddRow", StringComparison.OrdinalIgnoreCase)) { // Get the row that was clicked (index 0. Meaning that 0 is 1, 1 is 2 and so on) // Objects can be null, Int32s cannot not. // Int16 = 2 bytes long (short) // Int32 = 4 bytes long (int) // Int64 = 8 bytes long (long) int i = Convert.ToInt32(e.CommandArgument); // create a DataTable based off the view state DataTable dataTable = (DataTable)ViewState["gvParent"]; for (int part = 0; part 1) { dataTable.Rows[part]["Quantity"] = oldQuantitySubtract - 1; // Instert a new row at a specific index DataRow dtAdd = dataTable.NewRow(); for (int k = 0; k dtAdd[k] = dataTable.Rows[part][k]; dataTable.Rows.InsertAt(dtAdd, i + 1); break; //dataTable.Rows.Add(dtAdd); } } // Rebind the data gvParent.DataSource = dataTable; gvParent.DataBind(); } }

    Read the article

  • Design by Contract with Microsoft .Net Code Contract

    - by Fredrik N
    I have done some talks on different events and summits about Defensive Programming and Design by Contract, last time was at Cornerstone’s Developer Summit 2010. Next time will be at SweNug (Sweden .Net User Group). I decided to write a blog post about of some stuffs I was talking about. Users are a terrible thing! Protect your self from them ”Human users have a gift for doing the worst possible thing at the worst possible time.” – Michael T. Nygard, Release It! The kind of users Michael T. Nygard are talking about is the users of a system. We also have users that uses our code, the users I’m going to focus on is the users of our code. Me and you and another developers. “Any fool can write code that a computer can understand. Good programmers write code that humans can understand.” – Martin Fowler Good programmers also writes code that humans know how to use, good programmers also make sure software behave in a predictable manner despise inputs or user actions. Design by Contract   Design by Contract (DbC) is a way for us to make a contract between us (the code writer) and the users of our code. It’s about “If you give me this, I promise to give you this”. It’s not about business validations, that is something completely different that should be part of the domain model. DbC is to make sure the users of our code uses it in a correct way, and that we can rely on the contract and write code in a way where we know that the users will follow the contract. It will make it much easier for us to write code with a contract specified. Something like the following code is something we may see often: public void DoSomething(Object value) { value.DoIKnowThatICanDoThis(); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Where “value” can be uses directly or passed to other methods and later be used. What some of us can easily forget here is that the “value” can be “null”. We will probably not passing a null value, but someone else that uses our code maybe will do it. I think most of you (including me) have passed “null” into a method because you don’t know if the argument need to be specified to a valid value etc. I bet most of you also have got the “Null reference exception”. Sometimes this “Null reference exception” can be hard and take time to fix, because we need to search among our code to see where the “null” value was passed in etc. Wouldn’t it be much better if we can as early as possible specify that the value can’t not be null, so the users of our code also know it when the users starts to use our code, and before run time execution of the code? This is where DbC comes into the picture. We can use DbC to specify what we need, and by doing so we can rely on the contract when we write our code. So the code above can actually use the DoIKnowThatICanDoThis() method on the value object without being worried that the “value” can be null. The contract between the users of the code and us writing the code, says that the “value” can’t be null.   Pre- and Postconditions   When working with DbC we are specifying pre- and postconditions.  Precondition is a condition that should be met before a query or command is executed. An example of a precondition is: “The Value argument of the method can’t be null”, and we make sure the “value” isn’t null before the method is called. Postcondition is a condition that should be met when a command or query is completed, a postcondition will make sure the result is correct. An example of a postconditon is “The method will return a list with at least 1 item”. Commands an Quires When using DbC, we need to know what a Command and a Query is, because some principles that can be good to follow are based on commands and queries. A Command is something that will not return anything, like the SQL’s CREATE, UPDATE and DELETE. There are two kinds of Commands when using DbC, the Creation commands (for example a Constructor), and Others. Others can for example be a Command to add a value to a list, remove or update a value etc. //Creation commands public Stack(int size) //Other commands public void Push(object value); public void Remove(); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   A Query, is something that will return something, for example an Attribute, Property or a Function, like the SQL’s SELECT.   There are two kinds of Queries, the Basic Queries  (Quires that aren’t based on another queries), and the Derived Queries, queries that is based on another queries. Here is an example of queries of a Stack: //Basic Queries public int Count; public object this[int index] { get; } //Derived Queries //Is related to Count Query public bool IsEmpty() { return Count == 0; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } To understand about some principles that are good to follow when using DbC, we need to know about the Commands and different Queries. The 6 Principles When working with DbC, it’s advisable to follow some principles to make it easier to define and use contracts. The following DbC principles are: Separate commands and queries. Separate basic queries from derived queries. For each derived query, write a postcondition that specifies what result will be returned, in terms of one or more basic queries. For each command, write a postcondition that specifies the value of every basic query. For every query and command, decide on a suitable precondition. Write invariants to define unchanging properties of objects. Before I will write about each of them I want you to now that I’m going to use .Net 4.0 Code Contract. I will in the rest of the post uses a simple Stack (Yes I know, .Net already have a Stack class) to give you the basic understanding about using DbC. A Stack is a data structure where the first item in, will be the first item out. Here is a basic implementation of a Stack where not contract is specified yet: public class Stack { private object[] _array; //Basic Queries public uint Count; public object this[uint index] { get { return _array[index]; } set { _array[index] = value; } } //Derived Queries //Is related to Count Query public bool IsEmpty() { return Count == 0; } //Is related to Count and this[] Query public object Top() { return this[Count]; } //Creation commands public Stack(uint size) { Count = 0; _array = new object[size]; } //Other commands public void Push(object value) { this[++Count] = value; } public void Remove() { this[Count] = null; Count--; } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   Note: The Stack is implemented in a way to demonstrate the use of Code Contract in a simple way, the implementation may not look like how you would implement it, so don’t think this is the perfect Stack implementation, only used for demonstration.   Before I will go deeper into the principles I will simply mention how we can use the .Net Code Contract. I mention before about pre- and postcondition, is about “Require” something and to “Ensure” something. When using Code Contract, we will use a static class called “Contract” and is located in he “System.Diagnostics.Contracts” namespace. The contract must be specified at the top or our member statement block. To specify a precondition with Code Contract we uses the Contract.Requires method, and to specify a postcondition, we uses the Contract.Ensure method. Here is an example where both a pre- and postcondition are used: public object Top() { Contract.Requires(Count > 0, "Stack is empty"); Contract.Ensures(Contract.Result<object>() == this[Count]); return this[Count]; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   The contract above requires that the Count is greater than 0, if not we can’t get the item at the Top of a Stack. We also Ensures that the results (By using the Contract.Result method, we can specify a postcondition that will check if the value returned from a method is correct) of the Top query is equal to this[Count].   1. Separate Commands and Queries   When working with DbC, it’s important to separate Command and Quires. A method should either be a command that performs an Action, or returning information to the caller, not both. By asking a question the answer shouldn’t be changed. The following is an example of a Command and a Query of a Stack: public void Push(object value) public object Top() .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   The Push is a command and will not return anything, just add a value to the Stack, the Top is a query to get the item at the top of the stack.   2. Separate basic queries from derived queries There are two different kinds of queries,  the basic queries that doesn’t rely on another queries, and derived queries that uses a basic query. The “Separate basic queries from derived queries” principle is about about that derived queries can be specified in terms of basic queries. So this principles is more about recognizing that a query is a derived query or a basic query. It will then make is much easier to follow the other principles. The following code shows a basic query and a derived query: //Basic Queries public uint Count; //Derived Queries //Is related to Count Query public bool IsEmpty() { return Count == 0; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   We can see that IsEmpty will use the Count query, and that makes the IsEmpty a Derived query.   3. For each derived query, write a postcondition that specifies what result will be returned, in terms of one or more basic queries.   When the derived query is recognize we can follow the 3ed principle. For each derived query, we can create a postcondition that specifies what result our derived query will return in terms of one or more basic queries. Remember that DbC is about contracts between the users of the code and us writing the code. So we can’t use demand that the users will pass in a valid value, we must also ensure that we will give the users what the users wants, when the user is following our contract. The IsEmpty query of the Stack will use a Count query and that will make the IsEmpty a Derived query, so we should now write a postcondition that specified what results will be returned, in terms of using a basic query and in this case the Count query, //Basic Queries public uint Count; //Derived Queries public bool IsEmpty() { Contract.Ensures(Contract.Result<bool>() == (Count == 0)); return Count == 0; } The Contract.Ensures is used to create a postcondition. The above code will make sure that the results of the IsEmpty (by using the Contract.Result to get the result of the IsEmpty method) is correct, that will say that the IsEmpty will be either true or false based on Count is equal to 0 or not. The postcondition are using a basic query, so the IsEmpty is now following the 3ed principle. We also have another Derived Query, the Top query, it will also need a postcondition and it uses all basic queries. The Result of the Top method must be the same value as the this[] query returns. //Basic Queries public uint Count; public object this[uint index] { get { return _array[index]; } set { _array[index] = value; } } //Derived Queries //Is related to Count and this[] Query public object Top() { Contract.Ensures(Contract.Result<object>() == this[Count]); return this[Count]; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   4. For each command, write a postcondition that specifies the value of every basic query.   For each command we will create a postconditon that specifies the value of basic queries. If we look at the Stack implementation we will have three Commands, one Creation command, the Constructor, and two others commands, Push and Remove. Those commands need a postcondition and they should include basic query to follow the 4th principle. //Creation commands public Stack(uint size) { Contract.Ensures(Count == 0); Count = 0; _array = new object[size]; } //Other commands public void Push(object value) { Contract.Ensures(Count == Contract.OldValue<uint>(Count) + 1); Contract.Ensures(this[Count] == value); this[++Count] = value; } public void Remove() { Contract.Ensures(Count == Contract.OldValue<uint>(Count) - 1); this[Count] = null; Count--; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   As you can see the Create command will Ensures that Count will be 0 when the Stack is created, when a Stack is created there shouldn’t be any items in the stack. The Push command will take a value and put it into the Stack, when an item is pushed into the Stack, the Count need to be increased to know the number of items added to the Stack, and we must also make sure the item is really added to the Stack. The postconditon of the Push method will make sure the that old value of the Count (by using the Contract.OldValue we can get the value a Query has before the method is called)  plus 1 will be equal to the Count query, this is the way we can ensure that the Push will increase the Count with one. We also make sure the this[] query will now contain the item we pushed into the Stack. The Remove method must make sure the Count is decreased by one when the top item is removed from the Stack. The Commands is now following the 4th principle, where each command now have a postcondition that used the value of basic queries. Note: The principle says every basic Query, the Remove only used one Query the Count, it’s because this command can’t use the this[] query because an item is removed, so the only way to make sure an item is removed is to just use the Count query, so the Remove will still follow the principle.   5. For every query and command, decide on a suitable precondition.   We have now focused only on postcondition, now time for some preconditons. The 5th principle is about deciding a suitable preconditon for every query and command. If we starts to look at one of our basic queries (will not go through all Queries and commands here, just some of them) the this[] query, we can’t pass an index that is lower then 1 (.Net arrays and list are zero based, but not the stack in this blog post ;)) and the index can’t be lesser than the number of items in the stack. So here we will need a preconditon. public object this[uint index] { get { Contract.Requires(index >= 1); Contract.Requires(index <= Count); return _array[index]; } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Think about the Contract as an documentation about how to use the code in a correct way, so if the contract could be specified elsewhere (not part of the method body), we could simply write “return _array[index]” and there is no need to check if index is greater or lesser than Count, because that is specified in a “contract”. The implementation of Code Contract, requires that the contract is specified in the code. As a developer I would rather have this contract elsewhere (Like Spec#) or implemented in a way Eiffel uses it as part of the language. Now when we have looked at one Query, we can also look at one command, the Remove command (You can see the whole implementation of the Stack at the end of this blog post, where precondition is added to more queries and commands then what I’m going to show in this section). We can only Remove an item if the Count is greater than 0. So we can write a precondition that will require that Count must be greater than 0. public void Remove() { Contract.Requires(Count > 0); Contract.Ensures(Count == Contract.OldValue<uint>(Count) - 1); this[Count] = null; Count--; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   6. Write invariants to define unchanging properties of objects.   The last principle is about making sure the object are feeling great! This is done by using invariants. When using Code Contract we can specify invariants by adding a method with the attribute ContractInvariantMethod, the method must be private or public and can only contains calls to Contract.Invariant. To make sure the Stack feels great, the Stack must have 0 or more items, the Count can’t never be a negative value to make sure each command and queries can be used of the Stack. Here is our invariant for the Stack object: [ContractInvariantMethod] private void ObjectInvariant() { Contract.Invariant(Count >= 0); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   Note: The ObjectInvariant method will be called every time after a Query or Commands is called. Here is the full example using Code Contract:   public class Stack { private object[] _array; //Basic Queries public uint Count; public object this[uint index] { get { Contract.Requires(index >= 1); Contract.Requires(index <= Count); return _array[index]; } set { Contract.Requires(index >= 1); Contract.Requires(index <= Count); _array[index] = value; } } //Derived Queries //Is related to Count Query public bool IsEmpty() { Contract.Ensures(Contract.Result<bool>() == (Count == 0)); return Count == 0; } //Is related to Count and this[] Query public object Top() { Contract.Requires(Count > 0, "Stack is empty"); Contract.Ensures(Contract.Result<object>() == this[Count]); return this[Count]; } //Creation commands public Stack(uint size) { Contract.Requires(size > 0); Contract.Ensures(Count == 0); Count = 0; _array = new object[size]; } //Other commands public void Push(object value) { Contract.Requires(value != null); Contract.Ensures(Count == Contract.OldValue<uint>(Count) + 1); Contract.Ensures(this[Count] == value); this[++Count] = value; } public void Remove() { Contract.Requires(Count > 0); Contract.Ensures(Count == Contract.OldValue<uint>(Count) - 1); this[Count] = null; Count--; } [ContractInvariantMethod] private void ObjectInvariant() { Contract.Invariant(Count >= 0); } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Summary By using Design By Contract we can make sure the users are using our code in a correct way, and we must also make sure the users will get the expected results when they uses our code. This can be done by specifying contracts. To make it easy to use Design By Contract, some principles may be good to follow like the separation of commands an queries. With .Net 4.0 we can use the Code Contract feature to specify contracts.

    Read the article

  • zero-config CGI enabled web server

    - by halp
    To serve static content of a directory over http, one can simply navigate to that directory and type: python -m SimpleHTTPServer 11111 which will start a http server on port 11111. This hack is nice because it requires zero-config: no stand-alone web server, no config files at all. Is it possible to extend this example, or have an alternate way to achieve this goal, but also have CGI support? The final goal is to have a quick and lazy way of serving a web site from a certain directory. The site has static content (HTML pages, images), but also a CGI script. The CGI script must work properly when accessed via browser. Of course I could setup a virtual host in apache, allow CGI inside it etc. But that's not a zero-config approach.

    Read the article

  • Count unique visitors by group of visited places

    - by Mathieu
    I'm facing the problem of counting the unique visitors of groups of places. Here is the situation: I have visitors that can visit places. For example, that can be internet users visiting web pages, or customers going to restaurants. A visitor can visit as much places as he wishes, and a place can be visited by several visitors. A visitor can come to the same place several times. The places belong to groups. A group can obviously contain several places, and places can belong to several groups. Given that, for each visitor, we can have a list of visited places, how can I have the number of unique visitors per group of places? Example: I have visitors A, B, C and D; and I have places x, y and z. I have these visiting lists: [ A -> [x,x,y,x], B -> [], C -> [z,z], D -> [y,x,x,z] ] Having these number of unique visitors per place is quite easy: [ x -> 2, // A and D visited x y -> 2, // A and D visited y z -> 2 // C and D visited z ] But if I have these groups: [ G1 -> [x,y,z], G2 -> [x,z], G3 -> [x,y] ] How can I have this information? [ G1 -> 3, // A, C and D visited x or y or z G2 -> 3, // A, C and D visited x or z G3 -> 2 // A and D visited x or y ] Additional notes : There are so many places that it is not possible to store information about every possible group; It's not a problem if approximation are made. I don't need 100% precision. Having a fast algorithm that tells me that there were 12345 visits in a group instead of 12543 is better than a slow algorithm telling the exact number. Let's say there can be ~5% deviation. Is there an algorithm or class of algorithms that addresses this type of problem?

    Read the article

  • script to count the occurence of the particular string in the given time interval

    - by pruthvi
    We are trying to write a script "sendemail.sh" to count the number of occurrence of a particular string in a log file "SendEmail.log" within the given interval. We have a log file. In that we are searching for a pattern "ReqInputMsgLog" and need to count the number of times it occurred in the given period for eg: from "2014-08-19 11:30" to "2014-08-19 11:34". And our script look like this: #!/bin/sh enterdate=$1 echo $enterdate enddate=$2 enterdate1=`date +%s -d $enterdate +"%Y-%m-%d %H:%M"` echo $enterdate1 enddate1=`date +%s -d $enddate +"%Y-%m-%d %H:%M"` echo $enddate count=0 cat SendEmail.log | grep "ReqInputMsgLog" | awk -F "[" '{print $3}' | awk -F "," '{print $1}' > /con/scripts_server/file.txt for line in `cat /con/scripts_server/file.txt` do logdate=`echo $line | awk -F : '{print $1":"$2}'` if [[ $logdate < $enddate1 ]]; then count=`expr $count + 1` fi done echo $count But when we are trying to execute the script by the below command its not showing the proper count. ./sendemail.sh "2014-08-19 11:30" "2014-08-19 11:34" Log file is very big one. Small chunk has been posted here. INFO [SIBJMSRAThreadPool : 5] [2014-08-19 11:18:24,471] SendEmail - 8/19/14 11:18 AM,ECCF25B0-0147-4000-E000-1B830A3C05A9,ReqInputMsgLog,SendEmail,<?xml version="1.0" encoding="UTF-8"?> <in:sendEmailRequestMsg xmlns:in="http://EmailMed/EmailMedInterface" xmlns:ns0="wsdl.http://EmailMed/EmailMedInterface" xmlns:ns1="http://EmailMed/EmailMedInterface" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:me="wsdl.http://EmailMed/EmailMedInterface" xsi:type="me:sendEmailRequestMsg"> <in:sendEmail xmlns:xci0="http://EmailMed/EmailMedInterface"> INFO [SIBJMSRAThreadPool : 7] [2014-08-19 11:18:14,235] SendEmail - 8/19/14 11:18 AM,ECCEFDB2-0147-4000-E000-1B830A3C05A9,ReqInputMsgLog,SendEmail,<?xml version="1.0" encoding="UTF-8"?> <in:sendEmailRequestMsg xmlns:in="http://EmailMed/EmailMedInterface" xmlns:ns0="wsdl.http://EmailMed/EmailMedInterface" xmlns:ns1="http://EmailMed/EmailMedInterface" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:me="wsdl.http://EmailMed/EmailMedInterface" xsi:type="me:sendEmailRequestMsg"> <in:sendEmail xmlns:xci0="http://EmailMed/EmailMedInterface"> INFO [SIBJMSRAThreadPool : 7] [2014-08-19 11:18:14,241] SendEmail - xmlText: <?xml version="1.0" encoding="UTF-8"?> after awk command we will get a file "/con/scripts_server/file.txt" which looks similar like below: 2014-08-19 11:28:03 2014-08-19 11:28:06 2014-08-19 11:28:17 2014-08-19 11:28:53 2014-08-19 11:29:02 2014-08-19 11:29:47 2014-08-19 11:29:57 2014-08-19 11:30:07 2014-08-19 11:30:17 2014-08-19 11:30:19 2014-08-19 11:30:19 2014-08-19 11:30:22 2014-08-19 11:30:25 2014-08-19 11:30:25 2014-08-19 11:30:36 2014-08-19 11:30:51 2014-08-19 11:30:56 2014-08-19 11:30:59 2014-08-19 11:30:59 2014-08-19 11:31:08 2014-08-19 11:31:25 2014-08-19 11:32:19 2014-08-19 11:32:22 2014-08-19 11:32:27 2014-08-19 11:32:28 2014-08-19 11:32:41 2014-08-19 11:32:49 2014-08-19 11:32:59 2014-08-19 11:33:27 2014-08-19 11:33:41 2014-08-19 11:34:07 2014-08-19 11:34:14 2014-08-19 11:34:21 2014-08-19 11:34:25 2014-08-19 11:34:38 2014-08-19 11:34:50 2014-08-19 11:34:58

    Read the article

  • SQL SERVER – Solution – Puzzle – SELECT * vs SELECT COUNT(*)

    - by pinaldave
    Earlier I have published Puzzle Why SELECT * throws an error but SELECT COUNT(*) does not. This question have received many interesting comments. Let us go over few of the answers, which are valid. Before I start the same, let me acknowledge Rob Farley who has not only answered correctly very first but also started interesting conversation in the same thread. The usual question will be what is the right answer. I would like to point to official Microsoft Connect Items which discusses the same. RGarvao https://connect.microsoft.com/SQLServer/feedback/details/671475/select-test-where-exists-select tiberiu utan http://connect.microsoft.com/SQLServer/feedback/details/338532/count-returns-a-value-1 Rob Farley count(*) is about counting rows, not a particular column. It doesn’t even look to see what columns are available, it’ll just count the rows, which in the case of a missing FROM clause, is 1. “select *” is designed to return columns, and therefore barfs if there are none available. Even more odd is this one: select ‘blah’ where exists (select *) You might be surprised at the results… Koushik The engine performs a “Constant scan” for Count(*) where as in the case of “SELECT *” the engine is trying to perform either Index/Cluster/Table scans. amikolaj When you query ‘select * from sometable’, SQL replaces * with the current schema of that table. With out a source for the schema, SQL throws an error. so when you query ‘select count(*)’, you are counting the one row. * is just a constant to SQL here. Check out the execution plan. Like the description states – ‘Scan an internal table of constants.’ You could do ‘select COUNT(‘my name is adam and this is my answer’)’ and get the same answer. Netra Acharya SELECT * Here, * represents all columns from a table. So it always looks for a table (As we know, there should be FROM clause before specifying table name). So, it throws an error whenever this condition is not satisfied. SELECT COUNT(*) Here, COUNT is a Function. So it is not mandetory to provide a table. Check it out this: DECLARE @cnt INT SET @cnt = COUNT(*) SELECT @cnt SET @cnt = COUNT(‘x’) SELECT @cnt Naveen Select 1 / Select ‘*’ will return 1/* as expected. Select Count(1)/Count(*) will return the count of result set of select statement. Count(1)/Count(*) will have one 1/* for each row in the result set of select statement. Select 1 or Select ‘*’ result set will contain only 1 result. so count is 1. Where as “Select *” is a sysntax which expects the table or equauivalent to table (table functions, etc..). It is like compilation error for that query. Ramesh Hi Friends, Count is an aggregate function and it expects the rows (list of records) for a specified single column or whole rows for *. So, when we use ‘select *’ it definitely give and error because ‘*’ is meant to have all the fields but there is not any table and without table it can only raise an error. So, in the case of ‘Select Count(*)’, there will be an error as a record in the count function so you will get the result as ’1'. Try using : Select COUNT(‘RAMESH’) and think there is an error ‘Must specify table to select from.’ in place of ‘RAMESH’ Pinal : If i am wrong then please clarify this. Sachin Nandanwar Any aggregate function expects a constant or a column name as an expression. DO NOT be confused with * in an aggregate function.The aggregate function does not treat it as a column name or a set of column names but a constant value, as * is a key word in SQL. You can replace any value instead of * for the COUNT function.Ex Select COUNT(5) will result as 1. The error resulting from select * is obvious it expects an object where it can extract the result set. I sincerely thank you all for wonderful conversation, I personally enjoyed it and I am sure all of you have the same feeling. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: CodeProject, Pinal Dave, PostADay, Readers Contribution, Readers Question, SQL, SQL Authority, SQL Puzzle, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, SQLServer, T SQL, Technology

    Read the article

  • trying to divide complex numbers, division by zero

    - by user553619
    I'm trying the program below to divide complex numbers, it works for complex numbers but not when the denominator is real (i.e, the complex part is zero). Division by zero occurs in this line ratio = b->r / b->i ;, when the complex part b->i is zero (in the case of a real denominator). How do I get around this? and why did the programmer do this, instead of the more straightforward rule for complex division The wikipedia rule seems to be better, and no division by zero error would occur here. Did I miss something? Why did the programmer not use the wikipedia formula?? Thanks /*! @file dcomplex.c * \brief Common arithmetic for complex type * * <pre> * -- SuperLU routine (version 2.0) -- * Univ. of California Berkeley, Xerox Palo Alto Research Center, * and Lawrence Berkeley National Lab. * November 15, 1997 * * This file defines common arithmetic operations for complex type. * </pre> */ #include <math.h> #include <stdlib.h> #include <stdio.h> #include "slu_dcomplex.h" /*! \brief Complex Division c = a/b */ void z_div(doublecomplex *c, doublecomplex *a, doublecomplex *b) { double ratio, den; double abr, abi, cr, ci; if( (abr = b->r) < 0.) abr = - abr; if( (abi = b->i) < 0.) abi = - abi; if( abr <= abi ) { if (abi == 0) { fprintf(stderr, "z_div.c: division by zero\n"); exit(-1); } ratio = b->r / b->i ; den = b->i * (1 + ratio*ratio); cr = (a->r*ratio + a->i) / den; ci = (a->i*ratio - a->r) / den; } else { ratio = b->i / b->r ; den = b->r * (1 + ratio*ratio); cr = (a->r + a->i*ratio) / den; ci = (a->i - a->r*ratio) / den; } c->r = cr; c->i = ci; }

    Read the article

  • Count Distinct With IF in MySQL?

    - by user1600801
    I need to do a query with count distinct and IF, but the results always are 0. What I need to do, is count the different users from a table in different months, using IF. My individual query, for one month is this: SELECT COUNT(DISTINCT(idUsers)) AS num_usuarios FROM table01 WHERE date1='201207' But I need to get the results by different months in the same query. What I'm trying to do is this: SELECT IF(date1=(201207), count(distinct(idUsers)), 0) as user30, IF(fecha1=(201206), count(distinct(idUsers)), 0) as user60, IF(fecha1=(201205), count(distinct(idUsers)), 0) as user90, IF(fecha1=(201204), count(distinct(idUsers)), 0) as user120, IF(fecha1=(201203), count(distinct(idUsers)), 0) as user150 FROM table01 But the all the results are always 0.

    Read the article

  • NSMutableArray: count is a method or a property?

    - by Rafael Oliveira
    I want to verify if I'm in the last cell of the UITable. Should I use a NSInteger property in my controller and store the value of the count of the data (it's an NSMutableArray) that populates the table? I'm asking because I don't know if count iterates over all objects of the array to count or if it only gets me a value of a count property. What would be better ? store the value: myCount = [myArray count] use directly: [myArray count] store numberOfRows: myCount = numberOfRowsInSection:[indexPath 0] use numberOfRows directly: numberOfRowsInSection:[indexPath 0]

    Read the article

  • Linq, double left join and double count

    - by Fabian Vilers
    Hi! I'm looking to translate this SQL statement to a well working & performant LINQ command. I've managed to have the first count working using the grouping count and key members, but don't know how to get the second count. select main.title, count(details.id) as details, count(messages.id) as messages from main left outer join details on main.id = details.mainid left outer join messages on details.id = messages.detailid group by main.title Any advice is welcome! Fabian

    Read the article

  • how do I deconstruct COUNT()?

    - by user151841
    I have a view with some joins in it. I'm doing a select from that view with COUNT(*) as one of the columns of the select. I'm surprised by the number it's returning. Note that there is no GROUP BY nor aggregate column statement in the source view that the query is drawing from. How can I take it apart to see how it arrives at this number? I have three columns in the GROUP BY clause. SELECT column1, column2, column3, COUNT(*) FROM View GROUP BY column1, column2, column3 I get a result like +---------+---------+---------+----------+ | column1 | column2 | column3 | COUNT(*) | +---------+---------+---------+----------+ | value1 | valueA | value_a | 103 | +---------+---------+---------+----------+ | value2 | valueB | value_b | 56 | +---------+---------+---------+----------+ etc. I'd like to see how it arrives at that 103, 26, etc. In other words, I want to run a query that returns 103 rows of something, so that I know that I've expressed the query properly. I'm double-checking my work. I'm not saying that I think COUNT(*) doesn't work ( I know that "SELECT is not broken" ), what I want to double-check is exactly what I'm expressing in my query, because I think I've expressed the wrong thing, which would be why I'm getting unexpected values. I need to see more what I'm actually directing MySQL to count. So should I take them one by one, and try out each value in a WHERE clause? In other words, should I do SELECT column1 FROM View WHERE column1 = 'first_grouped_value' SELECT column1 FROM View WHERE column1 = 'second_grouped_value' SELECT column2 FROM View WHERE column1 = 'first_grouped_value' SELECT column2 FROM View WHERE column1 = 'second_grouped_value' and see the row count returned matches the COUNT(*) value in the grouped results? Because of confidentiality, I won't be able to post any of the query or database structure. All I'm asking for is a general technique to see what COUNT(*) is actually counting.

    Read the article

  • getting count(*) using createSQLQuery in hibernate?

    - by JohnSmith
    I have several sql queries that I simply want to fire at the database. I am using hibernate throughout the whole application, so i would prefer to use hibernate to call this sql queries. In the example below i want to get count + name, but cant figure out how to get that info when i use createSQLQuery(). I have seen workarounds where people only need to get out a single "count()" from the result, but in this case I am using count() + a column as ouput SELECT count(*), a.name as count FROM user a WHERE a.user_id IN (SELECT b.user_id FROM user b) GROUP BY a.name HAVING COUNT(*) BETWEEN 2 AND 5; fyi, the above query would deliver a result like this if i call it directly on the database: 1, John 2, Donald 1, Ralph ...

    Read the article

  • How to catch a division by zero?

    - by Cristian Castiblanco
    I have a large mathematical expression that has to be created dinamically. So, for example, once I have parsed "something" the result will be a string like: "$foo+$bar/$baz";. So, for calculating the result of that expression I'm using the eval function... something like this: eval("\$result = $expresion;"); echo "The result is: $result"; The problem here is that sometimes I get errors that says there was a division by zero, and I don't know how to catch that Exception. I have tried things like: eval("try{\$result = $expresion;}catch(Exception \$e){\$result = 0;}"); echo "The result is: $result"; Or: try{ eval("\$result = $expresion;"); } catch(Exception $e){ $result = 0; } echo "The result is: $result"; But it does not work. So, how can I avoid that my application crashes when there is a division by zero?

    Read the article

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