Intel Fortran Compiler For Mac
.O1 b. Enables optimizations for speed and disables some optimizations that increase code size and affect speed. To limit code size, this option:.
Intel Fortran Compiler For Windows
Enables global optimization; this includes data-flow analysis, code motion, strength reduction and test replacement, split-lifetime analysis, and instruction scheduling. Disables intrinsic recognition and intrinsics inlining. Disables loop unrolling. The O1 option may improve performance for applications with very large code size, many branches, and execution time not dominated by code within loops. On IA-32 Mac OSX platforms, -O1 sets the following:.unroll0,.fno-builtin,.mno-ieee-fp,.fomit-frame-pointer (same as -fp),.ffunction-sections. Includes:.O2 b.
Enables optimizations for speed. This is the generally recommended optimization level.O3 b. Enables O2 optimizations plus more aggressive optimizations, such as prefetching, scalar replacement, and loop and memory access transformations.
Enables optimizations for maximum speed, such as:. Loop unrolling, including instruction scheduling. Code replication to eliminate branches.
Padding the size of certain power-of-two arrays to allow more efficient cache use On IA-32 and Intel EM64T processors, when O3 is used with options -ax or -x (Linux/Mac OSX), the compiler performs more aggressive data dependency analysis than for O2, which may result in longer compilation times. The O3 optimizations may not cause higher performance unless loop and memory access transformations take place. The optimizations may slow down code in some cases compared to O2 optimizations. The O3 option is recommended for applications that have loops that heavily use floating-point calculations and process large data sets.fast b. The -fast option enhances execution speed across the entire program by including the following options that can improve run-time performance:.O3 (maximum speed and high-level optimizations).ipo (enables interprocedural optimizations across files).no-prec-div (disable -prec-div), where -prec-div improves precision of FP divides (some speed impact).mdynamic-no-pic, where -mydynamic-no-pic indicates that code is not relocatable To override one of the options set by -fast, specify that option after the -fast option on the command line.
The options set by -fast may change from release to release. Includes:.no-prec-div. This option improves precision of floating-point divides. It has a slight impact on speed. With some optimizations, such as -xN and -xB (Linux) or /QxN and /QxB (Windows), the compiler may change floating-point division computations into multiplication by the reciprocal of the denominator. For example, A/B is computed as A. (1/B) to improve the speed of the computation.
However, sometimes the value produced by this transformation is not as accurate as full IEEE division. When it is important to have fully precise IEEE division, use this option to disable the floating-point division-to-multiplication optimization. The result is more accurate, with some loss of performance. If you specify -no-prec-div (Linux and Mac OSX), it enables optimizations that give slightly less precise results than full IEEE division. The default is -prec-div.Wl,-stackaddr,(0x)?(A-Za-z0-9+) b. Specifies the initial address of the stack pointer value, where value is a hexadecimal number rounded to the segment alignment.
The default segment alignment is the target pagesize (currently, 1000 hexadecimal for the PowerPC and for i386). If -stacksize is specified and -stackaddr is not, a default stack address specific for the architecture being linked will be used and its value printed as a warning message. This creates a segment named UNIXSTACK. Note that the initial stack address will be either at the high address of the segment or the low address of the segment depending on which direction the stack grows for the architecture being linked.Wl,-stacksize,(0x)?(A-Za-z0-9+) b. Specifies the size of the stack segment value, where value is a hexadecimal number rounded to the segment alignment. The default segment alignment is the target pagesize (currently, 1000 hexadecimal for the PowerPC and for i386).
If -stackaddr is specified and -stacksize is not, a default stack size specific for the architecture being linked will be used and its value printed as a warning message. This creates a segment named UNIXSTACK. The system under test is deemed reasonably quiet by turning off the following from the System Preferences panel:. Automatic Software Updates (turned ON by default). Screen Savers (turned ON by default). Unused wireless and bluetooth connectivity (turned ON by default). Network time syncrhonization (turned ON by default).