HP Fortran Programmer's Guide (B3908-90031; September 2011)

Compiling and linking
Compiling with the f90 command
Chapter 230
Items promoted include constants, scalar variables, arrays, components of derived
types, and record fields. This option also promotes intrinsics as well as the results and
arguments of user-defined functions to the proper precision. Types specified in ON
statements are also promoted.
The entire program should be compiled with this option, not just selected files.
This option is useful when porting programs that depend on the increased precision of 8
and 16 bytes. If you want to promote only single-precision items, use the +autodbl4
option. (REAL(KIND=16) arithmetic is slow.)
The default is +noautodbl.
+[no]autodbl4
Like +autodbl, +auotdbl4 increases the default size of integer, logical, and real
items to 8 bytes, and the default size of complex items to 16 bytes; see Table 2-3.
Unlike +autodbl, it does not increase the default size of double precision.
This option does not increase the size of the following:
INTEGER(KIND=4)
INTEGER(4) J
REAL*8 D
3.1416_4, 113_4
Note, however, that constants specified with an exponent—for example, 4.0E0 and
2.3D0—are doubled.
Items promoted include constants, scalar variables, arrays, components of derived
types, and record fields. This option also promotes intrinsics as well as the results and
arguments of user-defined functions to the proper precision. Types specified in ON
statements are also promoted.
Table 2-3 Data type sizes and +autodbl[4]
Sizes in bytes of intrinsic types
Integer,
logical, and
real
Double
precision
Complex
Default sizes 4 8 8
+autodbl 81616
+autodbl4 8816