Which one is fater, COMP or COMP3 and why

mf_kumar · New User Joined: 10 Jan 2006 Posts: 1

Hi ,
Please any one give the answer this question.

Which one is fater, COMP or COMP3 and why ?

regards,
kumar.

mmwife · Super Moderator Joined: 30 May 2003 Posts: 1592

Generally, if COMP is kept under 8 bytes it's faster than COMP-3. Why? Because COMP uses register to register (RR) Assembler instructions; COMP-3 uses storeage to storage (SS).

That's basically one reason why an INDEX is preferable to a SUBSCRIPT and COMP is recommended for SSs.

There are exceptions involving the number of calcs and the size of tables having to do with overhead is not "recovered" when small execution volumes are processed.

DavidatK · Posted: Mon May 01, 2006 10:29 pm

Hello kumar,

Jack is absolutely correct, individual instructions using COMP values are faster than instructions using COMP-3 values.

But, I?m going to throw a wrench into the works. Even through COMP instructions are faster, you sometimes use more of them to perform the same task.

Here are a few examples of the COBOL code and the generated Assembler code, and as you can see, it makes a big difference in the mix of COMP COMP-3 and the calculations you do.

mmwife · Super Moderator Joined: 30 May 2003 Posts: 1592

Afew other points:

As David has illustrated in some of his examples, mixing data formats is usually not a good idea, but sometimes it can avoid confusion without adding too much overhead. You'll have to make that determination.

I've never taken the time to check, but I remember hearing that non-integer math adds significant overhead when using COMP data types.