Doh![color=blue]
> You will find that ArrayList is almost always more efficient.[/color]
I really should have said "performs faster", as the boxing of value types
may make it more inefficient...
Jay
"Jay B. Harlow [MVP - Outlook]" <Jay_Harlow_MVP@msn.com> wrote in message
news:uUf487etEHA.2876@TK2MSFTNGP14.phx.gbl...[color=blue]
> Peter,
> Profile (time) it and see.
>
> You will find that ArrayList is almost always more efficient. This is
> because the ArrayList over allocates its internal array.
> ArrayList.Capacity represents the number of elements the array list can
> hold (the size of its internal array), while ArrayList.Count represents
> the number of elements currently in the ArrayList (the number of times you
> called ArrayList.Add without a ArrayList.Remove).
>
> When the ArrayList.Count reaches its ArrayList.Capacity the ArrayList will
> reallocate its internal array, effectively it does a "Redim Preserve", it
> does this by allocating a new internal array, copying the contents of the
> old internal array to the new internal array. It doubles the size of its
> internal array each time it needs to reallocate it. The Capacity defaults
> to 16 if you do not change it via the Constructor when you create the
> ArrayList. NOTE: If I plan on adding 1000 elements to the ArrayList I
> would create the ArrayList with a Capacity of 1000 via the constructor.
>
> When you use "Redim Preserve" internally VB creates a new array, then
> copies all the elements from the old array to the new array. If you are
> Redim Preserve with a factor of 1, then you are doing a lot of coping,
> especially if you have 1000 elements!
>
> Remember that an ArrayList's internal array is an array of Object, so if
> you are storing Integers, they will be boxed going in & coming out. This
> may or may not be a performance issue. You need to profile it and see. If
> the boxing is causing a performance issue (proven via profiling), then
> what I do is create an IntegerBuffer. Which is like an ArrayList &
> StringBuilder, it maintains an over allocated internal array of integers,
> with Capacity & Count properties, when I add integers to the
> IntegerBuffer, I increment the Count, when the Count reaches Capacity I
> "Redim Preserve" the internal array, doubling its size.
>
> Just Remember the 80/20 rule. That is 80% of the execution time of your
> program is spent in 20% of your code. I will optimize (worry about
> performance, memory consumption) the 20% once that 20% has been identified
> &
> proven to be a performance problem via profiling (CLR Profiler is one
> profiling tool).
>
> For info on the 80/20 rule & optimizing only the 20% see Martin Fowler's
> article "Yet Another Optimization Article" at
>
http://martinfowler.com/ieeeSoftware...timization.pdf
>
> Info on the CLR Profiler:
>
http://msdn.microsoft.com/library/de...nethowto13.asp
>
>
http://msdn.microsoft.com/library/de...anagedapps.asp
>
>
> NOTE: In VS.NET 2005 (aka Whidbey, due out later in 2005)
>
http://lab.msdn.microsoft.com/vs2005/ we will have Generics, which will
> give us a generic "ArrayList" class called List(Of T) which can then use
> as our "IntegerBuffer" above.
>
http://msdn2.microsoft.com/library/6sh2ey19.aspx
>
>
> Rather then return a 2 dimensional array why not return a
> DataSet/DataTable? Or a collection of Domain objects?
>
> Hope this helps
> Jay
>
> "Peter" <peter@mclinn.com> wrote in message
> news:dcde2a5a.0410190645.f01bad2@posting.google.co m...[color=green]
>>I run into this situation all the time and I'm wondering what is the
>> most efficient way to handle this issue:
>>
>> I'll be pulling data out of a data source and want to load the data
>> into an array so that I can preform complicated operations against
>> this data. The returned record count in these operations is always
>> variable.
>>
>> 1. I have been using an arraylist.add function to handle
>> non-multidemional returns but was wondering if I'm better off diming
>> these returns as a strString() and then redimin with presearve as the
>> values come in?
>>
>> Example
>>
>> Dim StrString() as string
>>
>> dim i as integer = 0
>>
>> for data looping....
>> redim presearve StrString(i + 1)
>> i +=1
>> next
>>
>> the next question would be in the multidemin.
>>
>> 2. If you have a sql statement that returns multi demensional
>> information what is the best way to normally handle these situations.
>> When you do not know the record count.
>>
>> Example:
>>
>> sql = select Value1, Value2Subset, Value3Subset
>>
>>
>> Dim sqlHold(1, 3)
>>
>> If this was more than 1000 rows.... what type of variable scope should
>> I use.
>> sqlHold(0,0) = Value1
>> sqlHold(0,1) = Value2Subset
>> sqlHold(0,1) = Value3Subset[/color]
>
>[/color]
