The default FPU precision on Linux* and Mac OS* is a 64-bit significant. This equates to the compiler switch -pc80. The corresponding setting on Windows* is a 53-bit significant, equivalent compiler switch -Qpc64. This difference may account for a variation in results when comparing execution of identical programs/algorithms on Linux/Mac OS* and Windows.

Note: These refer to internal or intermediate, register to register calculations, which may be of greater precision than the declared precision for the variables used. When results are stored back to memory, they are rounded to the declared precision for the variables as necessary.

These defaults are at the operating system level and outside the control of the compiler.