Cmplx( 1.0_q, 0.0_q,kind=q)

1

See here for more details about the following code snippet used in vasp source code:

! Define Pauli-matrices
sig=zero
sig(1,2,1)=cmplx( 1.0_q, 0.0_q,kind=q)
sig(2,1,1)=cmplx( 1.0_q, 0.0_q,kind=q)
sig(1,2,2)=cmplx( 0.0_q,-1.0_q,kind=q)
sig(2,1,2)=cmplx( 0.0_q, 1.0_q,kind=q)
sig(1,1,3)=cmplx( 1.0_q, 0.0_q,kind=q)
sig(2,2,3)=cmplx(-1.0_q, 0.0_q,kind=q)

I’ve searched in the Intel® Fortran Compiler Classic and Intel® Fortran Compiler Developer Guide and Reference, but still can’t figure out the meaning of _q and kind=q used in the above data type definition:

cmplx( 0.0_q,-1.0_q,kind=q)

Any more hints will be highly appreciated.

Regards,
HZ

2

q must be a named integer constant defined somewhere in the code that is given a value of a valid real kind. I.e. look for a statement like integer, parameter :: q = selected_real_kind(15,300).

1 Like
3

I found the following results, which is not exactly the same as your guess:

werner@X10DAi-00:~/Public/hpc/vasp/release/vasp.6.3.0$ rg -IN ':: q =' | awk '!a[$0]++'
      INTEGER, PARAMETER :: q =SELECTED_REAL_KIND(10)
4 
selected_real_kind(p,r)

decimal precision of at least P digits
exponent range of at least R

5

Thank you for providing documentation. The GNU Fortran Compiler and Intel Fortran Compiler follow similar convention rules:

  1. GNU Fortran Compiler:

Before Fortran 2008, at least one of the arguments R or P shall be present; since Fortran 2008, they are assumed to be zero if absent.

  1. Intel Fortran Compiler

If p or r is absent, the result is as if the argument was present with the value zero. If
radix is absent, there is no requirement on the radix of the selected kind.