

Arithmetic precision

To ensure the processor-independent precision, the working precision (wp) is defined in the precision_comm_module.f90 module file.

The default precision is 64-bit real, the users can opt for 128-bit real by modifying wp.

The default size used for an integer is KIND = 4, meaning that any integer may have a signed value ranging from -2,147,483,648 to 2,147,483,647. In PyCAC, the maximum integer is usually the number of atoms (both the real atoms in the atomistic domain and the interpolated atoms in the coarse-grained domain). In the case that each element contains 2197 atoms, this limit suggests that there cannot be more than 977,461 elements in a fully coarse-grained simulation cell. If the user wants to study larger simulation cells, he/she needs to modify the source code.