[dba-VB] Merge rows

Sorry, 

I was under the impression that we were talking about selecting rows from JC's "Database 
>From Hell", not just manipulating bit arrays which we have somehow magically populated 
without pulling data from SQL Server.


-- 
Stuart  



On 23 Sep 2009 at 10:06, Shamil Salakhetdinov wrote:

> Hi Stuart,
> 
> We're talking C#/VB.NET here? - try test code in P.S - 
> 
> ===========
> one billion
> =========== 
> 
> of bitwise AND operations for 
> 
> ============================
> two 400 bits long bit arrays
> ============================ 
> 
> takes about
> 
> ====================================
> 1 minute 4 seconds 260 milliseconds
> ====================================
> 
> on my "mere mortals PC" - two years old Dual Core Pentium.
> 
> Please correct me if you or anybody else here will find mistakes in my
> coding/testing results.
> 
> Thank you.
> 
> --
> Shamil
> 
> P.S.
> 
> 
> static void test1()
> {
>     const long CYCLES_QTY = 1000000000; // 1 billion
>     bool[] values1 = (bool[])Array.CreateInstance(typeof(bool), 400);
>     bool[] values2 = (bool[])Array.CreateInstance(typeof(bool), 400);
>     values1[0] = true;
>     values1[225] = true;
>     values1[399] = true;
>     values2[225] = true;
>     values2[399] = true;
> 
>     System.Collections.BitArray bitTest1 =
>         new System.Collections.BitArray(values1);
>     System.Collections.BitArray bitTest2 =
>         new System.Collections.BitArray(values2);
> 
>     Console.WriteLine("{0:HH:mm:ss.fff}", DateTime.Now);
>     for (long l = 1; l < CYCLES_QTY; l++)
>         bitTest1.And(bitTest2);
>     Console.WriteLine("{0:HH:mm:ss.fff}", DateTime.Now);
> 
>     foreach (bool bit in bitTest1)
>         Console.Write("{0}", bit ? "1" : "0");
> 
>     Console.WriteLine();
> 
> //09:54:40.993
> //09:55:44.733
> //00000000000000000000000000000000000000000000000000000000000000000000000000
> 000000
> //00000000000000000000000000000000000000000000000000000000000000000000000000
> 000000
> //00000000000000000000000000000000000000000000000000000000000000000100000000
> 000000
> //00000000000000000000000000000000000000000000000000000000000000000000000000
> 000000
> //00000000000000000000000000000000000000000000000000000000000000000000000000
> 000001
> 
> }
> 
> static void test2()
> {
>     const long CYCLES_QTY = 1000000000; // 1 billion
>     bool[] values1 = { true, false, false, true };
>     bool[] values2 = { false, true, false, true };
> 
>     System.Collections.BitArray bitTest1 =
>         new System.Collections.BitArray(values1);
>     System.Collections.BitArray bitTest2 =
>         new System.Collections.BitArray(values2);
> 
>     Console.WriteLine("{0:HH:mm:ss.fff}", DateTime.Now);
>     for (long l = 1; l < CYCLES_QTY; l++)
>         bitTest1.And(bitTest2);
>     Console.WriteLine("{0:HH:mm:ss.fff}", DateTime.Now);
> 
>     foreach (bool bit in bitTest1)
>         Console.Write("{0}", bit ? "1" : "0");
> 
>     Console.WriteLine();
>     //09:52:32.604
>     //09:52:46.785
>     //0001
> }
> 
> 
> -----Original Message-----
> From: dba-vb-bounces at databaseadvisors.com
> [mailto:dba-vb-bounces at databaseadvisors.com] On Behalf Of Stuart McLachlan
> Sent: Wednesday, September 23, 2009 1:48 AM
> To: Discussion concerning Visual Basic and related programming issues.
> Subject: Re: [dba-VB] Merge rows
> 
> The data storage requirements may be smaller, but the time required to
> perform multiple 
> bitwise operation functions on every one of those 50 milllion rows is going
> to be a lot slower 
> than using simple selection criteria on fields.
> 
> -- 
> Stuart
> 
> 
> On 23 Sep 2009 at 0:15, Shamil Salakhetdinov wrote:
> 
> > OK, so you can "pack" 400 boolean fields into 50 bytes long binary field -
> > that will be BINARY(50) in T-SQL.
> > Although I'm not currently sure you can implement bitwise logical
> operations
> > solely using T-SQL: but I suppose you can get subset of data using
> > non-Boolean where clause, and then scan it in C#/VB.NET and filter using
> > bitwise C# operations/functions over bit arrays.
> > 
> > Something like that should work I suppose.
> > 
> > Please correct me if I'm wrong.
> > 
> > --
> > Shamil  
> <<< snip>>>
>  
> 
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