Intel® Fortran Compiler 17.0 Developer Guide and Reference
In cases where more than one data type can be used for a variable, consider selecting the data types based on the following hierarchy, listed from most to least efficient:
Integer
Single-precision real, expressed explicitly as REAL, REAL (KIND=4), or REAL*4
Double-precision real, expressed explicitly as DOUBLE PRECISION, REAL (KIND=8), or REAL*8
Extended-precision real, expressed explicitly as REAL (KIND=16) or REAL*16
In an arithmetic expression, you should avoid mixing integer and floating-point data.