Re: Just for fun - how slow are exceptions? - C# Discussion Boards

Re: Just for fun - how slow are exceptions?

Rob Philpott22-Apr-09 6:38

22-Apr-09 6:38

That's a good guess! But as Luc points out below, I haven't really done this correctly. Within Visual Studio in debug, I can throw 370 a second before the process dries out so about 2-3ms per exception.

Outside the VS debugger, its much, much faster. 1000 exceptions take 17ms to run, so all in all, its nowhere near as bad as I thought.

Regards,
Rob Philpott.

Re: Just for fun - how slow are exceptions?

Eddy Vluggen22-Apr-09 6:45

Eddy Vluggen

22-Apr-09 6:45

Rob Philpott wrote:
its much, much faster. 1000 exceptions take 17ms to run

I didn't imagine them being that fast! I thought that the average time would be near the 10 ms for a single exception.

with 1000's in <20 one can use them in a loop OMG | :OMG:

--edit--
Shocked enough to be having trouble with typing

I are troll Smile | :)

Re: Just for fun - how slow are exceptions?

Luc Pattyn22-Apr-09 6:46

Luc Pattyn

22-Apr-09 6:46

Sorry to bother you again, but I am always suspicious when someone has measured a time span of 16 or 17 msec, since that is pretty much what a system tick takes on most popular hardware/software combinations. Have you been using StopWatch or PerformanceCounters, or did you just look at DateTime.Now?

I suggest you use StopWatch, or run a loop 100 times as long; and you may want and learn more about timing issues by reading my timers article...

Smile | :)

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Re: Just for fun - how slow are exceptions?

Rob Philpott22-Apr-09 6:50

Rob Philpott

22-Apr-09 6:50

Fair point - I've been using my new friend Stopwatch, which on this hardware at least is a great deal more accurate than DateTime.Now.

Just did 10,000 - took 178ms.

Regards,
Rob Philpott.

Re: Just for fun - how slow are exceptions?

Luc Pattyn22-Apr-09 6:54

Luc Pattyn

22-Apr-09 6:54

That's OK then.
Now to see how slow that really is, you should replace the exception by a somewhat equivalent return or goto statement and see the difference. Laugh | :laugh:

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Re: Just for fun - how slow are exceptions?

Luc Pattyn22-Apr-09 6:31

Luc Pattyn

22-Apr-09 6:31

is that a debug build running inside Visual Studio? (which VS?)
is the first exception included in the measurement?

Visual used to be very slow at dealing with the first exception; and for throughput measurements one should not include the beginning (unless it gets averaged out by observing a large time, say > 1 minute).

could be less than 1.

Smile | :)

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Re: Just for fun - how slow are exceptions?

Rob Philpott22-Apr-09 6:33

Rob Philpott

22-Apr-09 6:33

Good points - I'll check the results outside VS.

Regards,
Rob Philpott.

Re: Just for fun - how slow are exceptions?

Rob Philpott22-Apr-09 6:41

Rob Philpott

22-Apr-09 6:41

Yes, my whole experiment was flawed by forgetting about running things outside Visual studio. Results are in the above post.

All-in-all, its nowhere near as bad as I thought. 17 microseconds per exception. 50,000 odd a second. Perhaps they're not as evil as all that.

Regards,
Rob Philpott.

Re: Just for fun - how slow are exceptions?

Skymir23-Apr-09 2:58

Skymir

23-Apr-09 2:58

They're just as evil as ever when no one comments that they're expecting an exception for some innocuous looking piece of code.

The true man wants two things: danger and play. For that reason he wants woman, as the most dangerous plaything.

Re: Just for fun - how slow are exceptions?

Colin Angus Mackay22-Apr-09 6:36

Colin Angus Mackay

22-Apr-09 6:36

Rob Philpott wrote:
Using them to control execution flow is criminal.

So the chap that wrote the ASP.NET page redirection mechanism should be locked up for all those ThreadAbortExceptions Smile | :)

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Re: Just for fun - how slow are exceptions?

Rob Philpott22-Apr-09 6:38

Rob Philpott

22-Apr-09 6:38

Not familiar with him, but it sounds like you should throw away the key....

Regards,
Rob Philpott.

Re: Just for fun - how slow are exceptions?

Luc Pattyn22-Apr-09 6:42

Luc Pattyn

22-Apr-09 6:42

Wait a minute, exceptions are supposed to alter execution flow,
how else would they be any better than on error resume next?

Smile | :)

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Re: Just for fun - how slow are exceptions?

Rob Philpott22-Apr-09 6:51

Rob Philpott

22-Apr-09 6:51

Luc Pattyn wrote:
Wait a minute, exceptions are supposed to alter execution flow

Agreed, but only in exceptional circumstances!

Regards,
Rob Philpott.

SQL SCRIPT

kibromg22-Apr-09 4:43

kibromg

22-Apr-09 4:43

Hi Guys,

I am having problem when running the Following SQL script.It takes Pretty long time to return result.
I am having about 500,000 records in my database.

select count(distinct(CR_Cli)),SO_name from Callrecords inner join dbo.StudioOperators
On CR_StudioOperatorID=SO_ID
where datename(month,cr_callstart)='April'
and Cr_cli not in (select Cr_cli from Callrecords where cr_callstart<'2009-03-31')
group by SO_name desc

Is there any way i can write this script?

Thanks you very much.

Re: SQL SCRIPT

Henry Minute22-Apr-09 5:13

Henry Minute

22-Apr-09 5:13

You do realise that there are several Database related fora on CP?

This is a C# forum.

Henry Minute

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Re: SQL SCRIPT

kibromg22-Apr-09 5:23

kibromg

22-Apr-09 5:23

Sorry I couldnt get SQL forum From the Message Board List.
I will Try MYSQL.

Thank you

Re: SQL SCRIPT

Dave Kreskowiak22-Apr-09 6:49

Dave Kreskowiak

22-Apr-09 6:49

How about the "General Database" forum??

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Dave Kreskowiak
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Visual Developer - Visual Basic
2006, 2007, 2008

Re: SQL SCRIPT

Henry Minute22-Apr-09 7:49

Henry Minute

22-Apr-09 7:49

General Database might be better, if it is MS SQLServer.

Re: SQL SCRIPT

PauloCastilho22-Apr-09 8:20

PauloCastilho

22-Apr-09 8:20

It´s very hard to rewrite a SQL query that I didn´t know the schema and relationships. Anyway, I made some changes.

kibromg wrote:
select count(distinct(CR_Cli))

Verify if the column has an index.

kibromg wrote:
datename(month,cr_callstart)='April'

Do not use much functions on where clause. Simplify... use "month(CR.callstart) = 4".

kibromg wrote:
and Cr_cli not in (select Cr_cli from Callrecords where cr_callstart<'2009-03-31')

If Cr_Cli "not in" where cr_callstart < '2009-03-31 then Cr_Cli "is in" where cr_callstart > '2009-03-30'. More than that, you are already referencing Callrecords in inner join, so you don´t need to create a subselect. On where clause, use this condition: "CR.callstart > '2009-03-30'".

kibromg wrote:
group by SO_name desc

On group by you have the column SO_name. Does this column have an index?! If not, you must consider creating one.

Try the code below, maybe it helps.

<br />
select count(distinct(CR.Cli))<br />
     , SO.name<br />
  from Callrecords CR<br />
 inner<br />
  join StudioOperators SO<br />
    on CR.StudioOperatorID = SO.ID<br />
 where month(CR.callstart) = 4<br />
   and CR.callstart > '2009-03-30'<br />
 group by SO.name desc<br />

Parsing incoming DateTime in C# WebService myself?

Thomas ST22-Apr-09 4:39

Thomas ST

22-Apr-09 4:39

I have a method in my Webservice:

[WebMethod]
public ReturnList GetList(string id, System.DateTime fromDate)

If I enter a invalid date when testing the service, I get a custom html-page with the errormessage and a stacktrace.

How can I get rid of this?

I want to handle the parsing of the incoming date myself, and send back a ReturnList object with a custom errormessage.. But I don't want to use string instead of dateTime, since I want it to be specified as dateTime in the wsdl..

Re: Parsing incoming DateTime in C# WebService myself?

student_rhr22-Apr-09 7:57

student_rhr

22-Apr-09 7:57

What about using an overload that way if it is passed in as something other then a valid DateTime object it will get treated by the overlaoded method and there you can try parsing it manually:

<code>
[WebMethod]
public ReturnList GetList(string id, string fromDate)
{
    // overlaod
    // your parsing logic
}
[WebMethod]
public ReturnList GetList(string id, System.DateTime fromDate)
{
    // Original function
}
</code>

Worth a try ... hth

How to make a column of listview control invisible

NarVish22-Apr-09 4:30

NarVish

22-Apr-09 4:30

Hi,

I would like to make a column of listview, invisible. by setting width property to zero, I can achieve this.
But, when I am trying to increase or decrease the width of previous or next column with mouse drag then the hiden column automatically get displayed.
Any solution for that ?
Like
making that column invisible. OR
making mannual resizing of any column as false
Please help me in this regard.
Thanks in advance

Re: How to make a column of listview control invisible

Eddy Vluggen22-Apr-09 4:55

Eddy Vluggen

22-Apr-09 4:55

You can override the painthandler; you got some extra control when owner-drawing. It may be more suitable to put the contents of the hidden column somewhere else. Like a Dictionary, linking each value to a ListViewItem Smile | :)

I are troll Smile | :)

help

benson.misi22-Apr-09 4:28

benson.misi

22-Apr-09 4:28

Object cannot be cast from DBNull to other types.
what does this mean

Re: help

musefan22-Apr-09 4:35

musefan

22-Apr-09 4:35

benson.misi wrote:
Object cannot be cast from DBNull to other types

this means... Object cannot be cast from DBNull to other types

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