From: ara.t.howard@...
Date: 2007-03-23T23:03:16+09:00
Subject: Re: Help with Excel (win32ole) and threads!?

On Fri, 23 Mar 2007, Alex Ciarlillo wrote:

> I have an application which is supposed to create a set of excel
> documents to display sales information for dining areas. The core of it
> is a class called SaleReport which is initialized with a sqlite database
> connection. The main function takes an excel worksheet object, a row
> number and some info about the location and queries the database to
> populate the excel sheet. Since none of the locations rely on each
> others data, I thought it would be pretty useful to thread that part, so
> that each location report is run in its own thread. The problem is, even
> though this seems to work, it has not improved performance at all and I
> am not sure where the bottleneck is. Here are my theories and the
> example code is at the bottom:
>
> 1) My first theory was that using a single excel application instance
> was blocking the threads so that only one could have access at a time,
> but now I rewrote it to use multiple excel instances and still no dice.
>
> 2) The connection to the database is limiting access to a single thread
> at a time. This shouldnt be the case since each instance of the
> SaleReport class gets it own connection, and SQLite is threadsafe.

sqlite is threadsafe, but supports access by only one thread at a time.  eg
it's not concurrent at the c level.  the only level of concurancy sqlite
provides is at the process level.

> 3) I'm flat out using the threads incorrectly.

it's easy to do on windows - anything which blocks one thread as the os level
will block all threads.  this is suprisingly easy to do.  your code looks
fine.  i'm not on windows, but if i were you i'd write some code that proves
to myself that concurent access to an excel doc by threads does not end up
blocking the whole process as i suspect it does.  same goes for your
SaleReport object.

cheers.

-a
-- 
be kind whenever possible... it is always possible.
- the dalai lama