Programming Efficient Code Version 0.9

Programming
Efficient Code Version 0.9

Focusing
Loops

Article by style='font-size:10.0pt;font-family:Arial'>Sachin Mehra (href="mailto:sachinweb@hotmail.com">sachinweb@hotmail.com)

One of the
worst things that a programmer can assume is that the compiler and middleware
will do the optimizations for you!  Most applications are being targeted
for 50-200 concurrent users, which is why we need to constantly be worrying
about the performance of our code.

Say you
have a search component (which will be on everybody's desktop) which takes 3-5
seconds to load; and consequently ties down the database.  Imagine what
will happen when 200 people try to load this at the same time.  Simple
math would suggest (say using an average of 4 seconds): (4 x 200) / 60 = 13 –
THAT'S 13 MINUTES!  And actually, when dealing with situations of high
contention, you cannot assume 100% efficiency and could be realistically
dealing with something in the range of 20-25 minutes of processing time
required. 

There is no
‘silver bullet' to making fast and efficient code.  Middleware will not
solve the problem for you, databases will not solve the problem for you, it is
up to you as a computational process engineer (how's that for a title?) to
understand and deal with the underlying inefficiencies in the software you design. 
There are many things which you need to consider, and you need to think your
logic out carefully.  One thing you should always be asking yourself is
“could this be done better?”.

 In
programming, we find ourselves in loops a lot.  In VB, ASP and COM, we
especially find ourselves looping through Collection objects an awful lot.  This is one of the particular
areas where many of us need some improvement. 

Our
programs spend a lot of time in loops, and unfortunately loose a lot of their
performance in them as well.  I will try to cover a few pointers which may
help you in certain situations save some unnecessary computational cycles off
you're code.

People tend
to think from beginning to end, and they tend to program in this forward
lineage as well.  But this can often be inefficient.  Sometimes the
computer can find its way from the end to the beginning much faster. 

Consider
the code in Example 1.

Example
1:

 i =0

style='font-size:9.0pt;font-family:Arial'>While style='mso-spacerun:yes'> istyle='font-size:9.0pt;font-family:Arial'> <> ubound(class=SpellE>arrayName)

               
doSomething

                style='mso-spacerun:yes'>  i = class=SpellE>i + 1

Wend

This is a
fairly straight-forward while-loop to iterate that iterates through an entire array
collection to do something.  But consider Example 2:

Example
2:

 i = class=GramE>ubound(arrayName)

style='font-size:9.0pt;font-family:Arial'>While 
i <> 0

               
doSomething

                style='mso-spacerun:yes'>  i = class=SpellE>i - 1

Wend

This example
is many times more efficient than Example 1.  In example one, we are
making a call to style='mso-bidi-font-style:normal'>ubound(class=SpellE>arrayName)style='font-size:10.0pt;font-family:Arial'> for every iteration through the
loop which is unnecessary, and also we are doing a direct X AND comparison to
determine if the loop should continue which is also more efficient.  By
looping backwards through the Array we
manage to increase processing efficiency but 50% or more!  

Final Words

Programming
is all about problem solving.  And as with other kinds of problem solving,
there are always many different ways to solve the problem.  However, some
ways are more certainly better than others.  You should take the time to
understand how the underlying components you are using actually work, and why
they work they way they do.

Version 1.0 of this article shall be comming soon, I need my friend Romi's help to work out and try a few application tests before comming up with the final version. You may also send in your inputs to me.

Article class=GramE>By Sachin Mehra (sachinweb@hotmail.com)