The following table lists options that enable you to control the compiler optimizations for floating-point computations on ItaniumŪ-based systems. The options listed here are not valid for IA-32 and IntelŪ EM64T systems.
Windows* |
Linux* |
Effect |
|---|---|---|
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/QIPF-fma |
-IPF-fma |
Enables or disables the contraction of floating-point multiply and add/subtract operations into a single operation. Unless -mp (Linux*) or /Op (Windows*) is specified, the compiler contracts these operations whenever possible. The -mp (Linux) or /Op (Windows) option disables the contractions. Use these options to override the default compiler behavior. For example, a combination of -mp (Linux) or /Op (Windows) and -IPF-fma (Linux) or /QIPF-fma (Windows) enables the compiler to contract operations: ifort -mp -IPF-fma myprog.f (Linux) ifort /Op /QIPF-fma myprog.f (Windows) For more information about compiler option interaction, see the following topic:
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/QIPF-fp-speculation |
-IPF-fp-speculation |
Sets the compiler to speculate on floating-point operations. This option is the default when -O0 (Linux) or /Od (Windows) is specified. For more information, see the following topic:
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|
/QIPF-fp-relaxed |
-IPF-fp-relaxed |
Enables use of faster but slightly less accurate code sequences for math functions, such as the sqrt() function and the divide operation. As compared to strict IEEE* precision, using this option slightly reduces the accuracy of floating-point calculations performed by these functions, usually limited to the least significant digit. For more information, see the following topic:
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/QIPF-flt-eval-method0 |
-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. For more information, see the following topic:
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/QIPF-fltacc |
-IPF-fltacc |
Disables the compiler to apply optimizations that affect floating-point accuracy. The ItaniumŪ compiler may re-associate floating-point expressions to improve application performance. Some options disable or restrict these floating-point optimizations. You can use this option or the -mp (Linux) or /Op (Windows) option to improve floating-point accuracy, but doing so will disable other optimizations. For more information, see the following topic:
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