Floating-point Arithmetic Precision for Itanium-based Systems

The following Intel® Fortran Compiler options enable you to control the compiler optimizations for floating-point computations on Itanium(TM)-based systems.

Contraction of FP Multiply and Add/Subtract Operations

-IPF_fma[-] enables or disables the contraction of floating-point multiply and add/subtract operations into a single operations. Unless -mp is specified, the compiler tries to contract these operations whenever possible. The -mp option disables the contractions.

-IPF_fma and -IPF_fma- can be used to override the default compiler behavior. For example, a combination of -mp and -IPF_fma enables the compiler to contract operations:

prompt>efc -mp -IPF_fma myprog.f

FP Speculation

-IPF_fp_speculationmode sets the compiler to speculate on floating-point operations in one of the following modes:

fast: sets the compiler to speculate on floating-point operations;

safe: enables the compiler to speculate on floating-point operations only when it is safe;

strict: enables the compiler's speculation on floating-point operations preserving floating-point status in all situations. In the current version, this mode disables the speculation of floating-point operations (same as off).

off: disables the speculation on floating-point operations.

FP Operations Evaluation

-IPF_flt_eval_method{0|2} option directs the compiler to evaluate the expressions involving floating-point operands in the following way:

-IPF_flt_eval_method0 directs the compiler to evaluate the expressions involving floating-point operands in the precision indicated by the variable types declared in the program.

-IPF_flt_eval_method2 is not supported in the current version.

Controlling Accuracy of the FP Results

-IPF_fltacc[-] enables/disables the compiler to apply optimizations that affect floating-point accuracy. By default, the compiler applies optimizations that affect floating-point accuracy.
-IPF_fltacc- disables such optimizations. -IPF_fltacc- is effective when -mp is on.

The Itanium compiler may reassociate floating-point expressions to improve application performance. Use -IPF_fltacc- or -mp to disable this behavior.