Re: MODULEand USE versus Argument Passing

Herman D. Knoble wrote:

Given a Subprogram that gets called millions of times,
we know that there is (CPU) overhead for subprogram linkage.

My question is, independent of compilers,
which is more efficient in practice:

passing a list of (say 3 to 10) arguments
to a subprogram's corresponding parameters,
OR using a Module and companion USE statement,
OR use named COMMON?


Global variables are *always* a bad idea.
Never pass function arguments through modules or common storage.

There is almost nothing
that modern computers do faster than [subprogram] calls.
You won't be able to measure the time that your function
spends on subprogram calls unless the subprogram does nothing.
A good optimizing compiler can "inline" lightweight
subprograms if the definition is visible at compile time --
if the subprogram is defined in the same source file
or in a module used by your program.

If your subprogram has more than a few arguments,
you probably have a design problem.
If some of the arguments can be grouped into larger objects,
create a derived type which contains them
and pass an object of that type to the function
instead of the separate arguments.
.

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