using library

[roddur]

hello friends,
in my coding, i tend to use few utility program, which are common to
whatever i do(like calculating runtime, declare default precision etc)
as a fortran module. is it profitable to use them as a library? on
other word, is there any specific advantages of using library(my own)
over module? i am not very comfortable with library, and tend to use
even lapack routines as subroutine in my code!! does this approach ok
as long as performance is concerned?

Secondly, do anyone aware of libraries of general numerical tools
(like integration,differentiation)? is it possible to use matlab from
fortran?

[TimP]

In principle, putting your own compilation of lapack in a library wouldn't have any run-time performance advantage over USEing them from a module. It should save you some recompilation time. If you want a run-time performance advantage for lapack, you would use Intel MKL or some other optimized library, assuming you use lapack in the modes for which those libraries are optimized.
With libraries, you have the option of attempting to save disk space by dynamic linking, so that you don't make copies every time you build. That may affect performance adversely, and definitely makes it more difficult to profile performance.

[roddur]

One more question!
Is it (in principle) possible to convert any subprogram to a library?

[TimP]

In principle, it's possible to combine any group of files of any type into a library.