CODEWITHSUNDEEP
makefilegfortranintel-fortran
witrus
witrus

Reputation: 297

compilation option FFLAGS in MAKEFILE

what does the compilation options mean? export FFLAGS = -O3 -r8 -i4 -I${PWD}/headers -nofor_main. -r8 means what?i4 means what?where could I find the help file.can anybody explain compilation option FFLAGS?I really appreciate it

Upvotes: 1

Views: 5245

Answers (1)

Beta
Beta

Reputation: 99144

You apparently already know that FFLAGS is a list of options for a FORTRAN compiler.

-r8 sets the size of certain data types to 8 bytes, depending on architecture. It is approximately the same as setting double precision.

-i4 sets the default integer size to 4 bytes.

Do you need more?

EDIT:

There are a lot of different compilers, and versions of compilers. The default for GNUMake is f77, and from the UNIX man page:

-r8
 Double the size of default REAL, DOUBLE, INTEGER, and COMPLEX data.

 NOTE: This option is now considered obsolete and may be
 removed in future releases. Use the more flexible -xtypemap
 option instead.

 This option sets the default size for REAL, INTEGER, and
 LOGICAL to 8, and for COMPLEX to 16.  For INTEGER and LOGI-
 CAL the compiler allocates 8 bytes, but does 4-byte arith-
 metic.  For actual 8-byte arithmetic,
 see -dbl.

Upvotes: 1

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