Lahey/GNU Fortran

Recommended Option Settings

If an LGF.FIG file exists in the current directory, examine its contents to insure that it contains the desired options.

Debugging and diagnostics

For debugging, the following option settings will provide an increased level of diagnostic ability, both at compile time, and during execution:

-chk -g -trace -w

For further analysis during development, consider specifying any of the following options:

-ap -co -cover -f[95|2003|2008|]

Optimizations

It is difficult to recommend one set of options that will satisfy every need.

For code that will run on many different machines, the LGF options -ofast -unroll -wpo -t generic will allow fast execution on a wide number of machine architectures while -ofast -unroll -wpo -t native will optimize for the compiling machine.

We have found on occasion that significant speed increases might be found by using the LGF -parallel option setting.

Parallelization can be most effective on code that is written to take advantage of these optimizations, and in such cases, dramatic improvements in execution times can occur.