If you invoke the IntelŪ Fortran Compiler without specifying any compiler options, the default state of each option takes effect. The following tables summarize the options whose default status is ON as they are required for Intel Fortran Compiler default operation. The tables group the options by their functionality.
For the default states and values of all options, see Compiler Options Quick Reference Alphabetical table in the IntelŪ Fortran Compiler Options Quick Reference. The table provides links to the sections describing the functionality of the options. If an option has a default value, such value is indicated.
Per your application requirement, you can disable one or more options. For general methods of disabling optimizations, see Volume I.
The following tables list all options that compiler uses for its default optimizations.
Default Option |
Description |
-align |
Analyzes and reorders memory layout for variables and arrays. |
-align rec8bytes |
Specifies 8-byte boundary for alignment constraint. |
-altparam |
Specifies if alterate form of parameter constant declarations is recognized or not. |
-ansi_alias |
Enables assumption of the program's ANSI conformance. |
-assume cc_omp |
Enables OpenMP conditional compilation directives. |
-ccdefault default |
Specifies default carriage control for units 6 and *. |
-double_size 64 |
Defines the default KIND for double-precision variables to be 64. -double_size 64 n is 64 (KIND=8) |
-dps |
Enables DEC* parameter statement recognition. |
-error_limit 30 |
Specifies the maximum number of error-level or fatal-level compiler errors permissible. |
-fpe 3 |
Specifies floating-point exception handling at run time for the main program. |
-iface nomixed_str_len_arg |
Specifies the type of argument-passing conventions used for general arguments and for hidden-length character arguments. |
-integer_size 32 |
Specifies the default size of integer and logical variables. |
-libdir all |
Controls the library names that should be emitted into the object file. |
-pad |
Enables changing variable and array memory layout. |
-pc80 |
-pc{32|64|80} enables floating-point significand precision control as follows: -pc32 to 24-bit significand, -pc64 to 53-bit significand, and -pc80 to 64-bit significand. |
-real_size 64 |
Specifies the size of REAL and COMPLEX declarations, constants, functions, and intrinsics. |
-save |
Saves all variables in static allocation. Disables |
-Zp8 |
-Zp{n} specifies alignment constraint for structures
on 1-, 2-, 4-, 8-, or 16-byte boundary. To disable, use |
Default Option |
Description |
-assume cc_omp |
Enables OpenMP conditional compilation directives. |
-fp |
Disables the use of the ebp register in optimizations. Directs to use the ebp-based stack frame for all functions. |
-fpe 3 |
Specifies floating-point exception handling at run time for the main program. -fpe 0 disables the option. |
-ip_no_inlining |
Disables full or partial inlining that would result from the -ip interprocedural optimizations. Requires -ip or -ipo. |
-IPF_fltacc- |
Enables the compiler to apply optimizations that affect floating-point accuracy. |
-IPF_fma |
Enables the contraction of floating-point multiply and add/subtract operations into a single operation. |
-IPF_fp_speculation |
Sets the compiler to speculate on floating-point operations. -IPF_fp_speculationoff disables this optimization. |
-ipo_obj |
Forces the generation of real object files. Requires -ipo. |
-O, -O1, -O2 |
Optimize for maximum speed. |
-Ob1 |
Disables inlining unless -ip or -Ob2 is specified. |
-openmp_report1 |
Indicates loops, regions, and sections parallelized. |
-opt_report_levelmin |
Specifies the minimal level of the optimizations report. |
-par_report1 |
Indicates loops successfully auto-parallelized. |
-tpp2 |
Optimizes code for the IntelŪ ItaniumŪ 2 processor for Itanium-based applications. Generated code is compatible with the Itanium processor. |
-tpp7 |
Optimizes code for the IntelŪ PentiumŪ 4 and IntelŪ Xeon(TM) processor for IA-32 applications. |
-unroll |
-unroll[n]: omit n
to let the compiler decide whether to perform unrolling or not (default). |
-vec_report1 |
Indicates loops successfully vectorized. |
To disable an option, use one of the following as applies:
Generally, to disable one or a group of optimization options, use -O0 option. For example:
ifort -O2 -O0 input_file(s)
Note
The -O0 option is part of a mutually-exclusive
group of options that includes -O0, -O,
-O1, -O2, and -O3.
The last of any of these options specified
on the command line will override the previous options from this group.
To disable options that include optional "-" shown as [-], use that version of the option in the command line, for example: -align-.
To disable options that have {n} parameter, use n=0 version, for example: -unroll0.
Note
If there are enabling and disabling
versions of switches on the line, the last one takes precedence.