Re: CGI vs JSP... -- WEB400

CGIDEV2 "kind of" compiles the template and does not have to search the template itselfat substitution time.

When used properly (more below), CGIDEV2 variable substitution performance just isn't anissue.

When CGIDEV2 reads a template record, it stores it in a memory-resident stream and placesits offset into a memory resident array of offsets.

If the record contains any substitution variables, it makes an entry for each into a setof memory resident arrays that contain the substitution variable's RRN, starting positionin its record, the substitution string, the length of the substitution string, and thesection name.

When a section is written, CGIDEV2 uses the HTML records' offsets to extract each HTMLrecord from the memory resident stream and %lookup with the record's RRN (%lookup usesbinary search, so it's fast) to ascertain whether it has any substitution variables. Ifso, the entries in the arrays are used to perform variable substitution. It was designedto be and is very efficient.

The part that involves a lot of work is processing the template into the stream and thearrays.

However, that processing does not have to be performed every time the CGI program runsbecause the 2nd and subsequent runs in the same activation group reuse the data previouslystored in the stream and the arrays.

I always recommend that frequently used CGIDEV2 programs be created with named activationgroups. In such programs, once template processing has been done, it is not done againuntil the list of template files changes or any of them is modified (date/timestampchanges). Usually, this is not during the activation group's lifetime.

If multiple programs use the same activation group, each of them should use the same listof template files to ensure that the templates are not processed again and again.Alternatively, each program could have its own activation group name.

The things that most slow down CGIDEV2 are not using named activation groups and leavingdebugging on after it is no longer needed.



Mel Rothman
CGIDEV2 Author




Seth Newton wrote:

Brad,

In a CGIDEV2 application, there is an HTML template that uses replacement
variables where your dynamic content will go. At runtime, APIs are used to
search/replace the replacement variables with their appropriate values.  The
difference in performance is quite noticeable, especially with a subfile

application that loads many records.

RPGsp’s compile process pre-determines which variables and expressions will
be need to be output to the browser at compile-time. When the application
runs, sections of HTML are output as needed, and the value of variables or
expressions are also output directly, with no search/replace taking place.

As an example, let's say this is our template:

Item Number: <%ITEM%> <br>
Item Description: <%DESC%>

With CGIDEV2 and other similar tools, the logic flows like this:

1. Read Template.
2. Search my template for <%ITEM%> and replace it with RPG variable ITEM.
3. Search my template for <%DESC%> and replace it with RPG variable DESC.
4. Output template.

Steps 2 and 3 are CPU-intensive.  In a subfile application, these Search
steps may be repeated thousands of times.

RPGsp, on the other hand, reads the template at compile time, and

restructures it to execute like this.

1. Output "Item Number:"

2. Output the value of RPG variable ITEM3. Output "<br> Item Description:"

4. Output the value of RPG variable DESC

Here, we have no CPU-intensive search/replace logic, which results in much

faster code.

Seth Newton
snewton@xxxxxxxxxxxxxxxxx
Profound Logic Software, Inc.
Toll-Free: (877) 224-7768 x115
Fax: (603) 849-7757

RPGsp - iSeries Web Development has never been this easy!
Watch video demos: http://www.profoundlogic.com/video_demos/



-----Original Message-----

I am used to working with CGI from RPGsp (www.RPGsp.com), which allowsyou to embed RPG variables into HTML templates. However, thetemplates are not searched at runtime. The pages are compiled in asimilar way JSP's are created, and that's why it's fast ... mostlikely faster than equivalent JSP's.


Explain how this works.  how can data from a DB be replaced anywhere except

for runtime.

Any time you're building dynamic applications data HAS to be
inserted/replaced/built at runtime.

Brad