Introduced phase change

src/templates_front/templator_front.org

@@ -171,7 +171,7 @@ __trexio_path__ = None
 
       #+NAME: table-exit-codes
    | Macro                            | Code | Description                                    |
-   |----------------------------------+------+----------------------------------------|
+   |----------------------------------+------+------------------------------------------------|
    | ~TREXIO_FAILURE~                 |   -1 | 'Unknown failure'                              |
    | ~TREXIO_SUCCESS~                 |    0 | 'Success'                                      |
    | ~TREXIO_INVALID_ARG_1~           |    1 | 'Invalid argument 1'                           |
@@ -210,6 +210,7 @@ __trexio_path__ = None
    | ~TREXIO_INVALID_DETERMINANT_NUM~ |   34 | 'Inconsistent number of determinants'          |
    | ~TREXIO_INVALID_STATE~           |   35 | 'Inconsistent state of the file'               |
    | ~TREXIO_VERSION_PARSING_ISSUE~   |   36 | 'Failed to parse package_version'              |
+   | ~TREXIO_PHASE_CHANGE~            |   37 | 'The function succeeded with a change of sign' |
 
    # We need to force Emacs not to indent the Python code:
    # -*- org-src-preserve-indentation: t
@@ -253,7 +254,7 @@ return '\n'.join(result)
 
 
    #+RESULTS:
-   :RESULTS:
+   :results:
    #+begin_src c :tangle prefix_front.h :exports none
    #define TREXIO_FAILURE                 ((trexio_exit_code) -1)
    #define TREXIO_SUCCESS                 ((trexio_exit_code) 0)
@@ -293,6 +294,7 @@ return '\n'.join(result)
    #define TREXIO_INVALID_DETERMINANT_NUM ((trexio_exit_code) 34)
    #define TREXIO_INVALID_STATE           ((trexio_exit_code) 35)
    #define TREXIO_VERSION_PARSING_ISSUE   ((trexio_exit_code) 36)
+   #define TREXIO_PHASE_CHANGE            ((trexio_exit_code) 37)
    #+end_src
 
    #+begin_src f90 :tangle prefix_fortran.f90 :exports none
@@ -334,6 +336,7 @@ return '\n'.join(result)
       integer(trexio_exit_code), parameter :: TREXIO_INVALID_DETERMINANT_NUM = 34
       integer(trexio_exit_code), parameter :: TREXIO_INVALID_STATE           = 35
       integer(trexio_exit_code), parameter :: TREXIO_VERSION_PARSING_ISSUE   = 36
+      integer(trexio_exit_code), parameter :: TREXIO_PHASE_CHANGE            = 37
    #+end_src
 
    #+begin_src python :tangle prefix_python.py :exports none
@@ -376,8 +379,9 @@ return '\n'.join(result)
    TREXIO_INVALID_DETERMINANT_NUM = 34
    TREXIO_INVALID_STATE           = 35
    TREXIO_VERSION_PARSING_ISSUE   = 36
+   TREXIO_PHASE_CHANGE            = 37
    #+end_src
-   :END:
+   :end:
 
 *** Decoding errors
 
@@ -5571,8 +5575,9 @@ def has_determinant_list(trexio_file) -> bool:
  ~trexio_to_orbital_list_up_dn~ function does the same but for both up- and down-spin components
   of the determinant and returns two list of orbitals each corresponding to a different component.
 
- ~trexio_to_bitfield_list~ function converts the list of occupied orbitals (up- or down-spin)
+ ~trexio_to_bitfield_list~ function converts the list of occupied orbitals (up- or down-spin) into the corresponding ~int64_t~
-  into the corresponding ~int64_t~ bitfield representation of the determinant.
+  bitfield representation of the determinant. If the creation of the bitfield requires a change of sign, the return code is
+ ~TREXIO_PHASE_CHANGE~.
 
 ** C
 
@@ -5606,22 +5611,38 @@ trexio_exit_code trexio_to_bitfield_list (const int32_t* orb_list,
   if (bit_list == NULL)  return TREXIO_INVALID_ARG_3;
   if (N_int <= 0)        return TREXIO_INVALID_ARG_4;
 
-  uint32_t i;
-  uint32_t k;
-  uint32_t iorb;
-
   for (int32_t j = 0 ; j < N_int ; j++) {
       bit_list[j] = (bitfield_t) 0;
   }
 
+  uint32_t i;
+  uint32_t k;
+  uint32_t iorb;
+  bitfield_t mask;
+  uint32_t nswaps = 0;
+
   for (int32_t pos = 0 ; pos < occupied_num ; pos++) {
     iorb = ((uint32_t) (orb_list[pos] + 1)) - TREXIO_ORBITAL_SHIFT;
+
+    // Set the bit of to one
     i = (uint32_t) (iorb >> TREXIO_NORB_PER_INT_SHIFT);
     k = (uint32_t) (iorb & (TREXIO_NORB_PER_INT - 1) );
-    bit_list[i] |= ((bitfield_t) 1) << k;
+    mask = ((bitfield_t) 1) << k;
+    bit_list[i] |= mask;
+
+    // Check for phase changes
+    mask = ~(mask - (bitfield_t) 1);
+    nswaps += popcnt(mask & bit_list[i]) - 1;
+    for (int j=i+1 ; j < N_int ; ++j) {
+      if (bit_list[j] != (bitfield_t) 0)
+        nswaps += popcnt(bit_list[j]);
+    }
   }
 
+  if ( (nswaps & 1) == 0)
     return TREXIO_SUCCESS;
+  else
+    return TREXIO_PHASE_CHANGE;
 }
     #+end_src
 

tests/test_f.f90

@@ -508,6 +508,24 @@ subroutine test_read(file_name, back_end)
     call exit(-1)
   endif
 
+  occ_num_dn = occ_num_up
+  orb_list_dn(:) = orb_list_up(:)
+  orb_list_dn(2) = orb_list_up(1)
+  orb_list_dn(1) = orb_list_up(2)
+  rc = trexio_to_bitfield_list(orb_list_dn, occ_num_dn, det_list_check, 3)
+  call trexio_assert(rc, TREXIO_PHASE_CHANGE)
+
+  do i=1,occ_num_dn
+    orb_list_dn(occ_num_up-i+1) = orb_list_up(i)
+  enddo
+
+  rc = trexio_to_bitfield_list(orb_list_dn, occ_num_dn, det_list_check, 3)
+  call trexio_assert(rc, TREXIO_SUCCESS)
+
+  rc = trexio_to_bitfield_list(orb_list_dn, occ_num_dn-1, det_list_check, 3)
+  call trexio_assert(rc, TREXIO_PHASE_CHANGE)
+
+
   rc = trexio_read_mo_num(trex_file, mo_num)
   call trexio_assert(rc, TREXIO_SUCCESS)