Compiler flags are used to provide to the compiler with information about library file locations, the level of optimization desired, and similar things. While a wide array of compiler share some flags in common it is not generally the case that you can pass flags intended for one compiler to another without problems. The flags used in the default BESTPRED makefile are described in Table 3.3.1 to assist users in porting from one platform to another.
Description of compiler flags in default makefile
Absoft Flag & Description & gfortran Flag
Consult your compiler documentation for additional details about compiler flags.
A Manual for Use of BESTPRED: A Program for Estimation of Lactation Yield and Persistency Using Best Prediction