TREX
/
qmckl
mirror of https://github.com/TREX-CoE/qmckl.git
1
0
Fork 0
Code Issues Projects Releases Wiki Activity
qmckl/org/qmckl_electron.org

20 KiB
Raw Blame History

Electrons

In conventional QMC simulations, up-spin and down-spin electrons are different. The electron data structure contains the number of up-spin and down-spin electrons, and the electron coordinates.

Context

The following data stored in the context:

uninitialized int32_t Keeps bit set for uninitialized data
num int64_t Total number of electrons
up_num int64_t Number of up-spin electrons
down_num int64_t Number of down-spin electrons
walk_num int64_t Number of walkers
provided bool If true, electron is valid
coord_new double[walk_num][3][num] New set of electron coordinates
coord_old double[walk_num][3][num] Old set of electron coordinates
coord_new_date uint64_t Last modification date of the coordinates
ee_distance double[walk_num][num][num] Electron-electron distances
ee_distance_date uint64_t Last modification date of the electron-electron distances

Data structure 

typedef struct qmckl_electron_struct {
int64_t   num;
int64_t   up_num;
int64_t   down_num;
int64_t   walk_num;
int64_t   coord_new_date;
int64_t   ee_distance_date;
double*   coord_new;
double*   coord_old;
double*   ee_distance;
int32_t   uninitialized;
bool      provided;
} qmckl_electron_struct;

The uninitialized integer contains one bit set to one for each initialization function which has not bee called. It becomes equal to zero after all initialization functions have been called. The struct is then initialized and provided == true.

Access functions

When all the data relative to electrons have been set, the following function returns true.

bool      qmckl_electron_provided       (const qmckl_context context);

#+NAME:post

Initialization functions

To set the data relative to the electrons in the context, the following functions need to be called. When the data structure is initialized, the coord_new and coord_old arrays are both allocated.

qmckl_exit_code  qmckl_set_electron_num        (qmckl_context context, const int64_t up_num, const int64_t down_num);
qmckl_exit_code  qmckl_set_electron_walk_num   (qmckl_context context, const int64_t walk_num);
qmckl_exit_code  qmckl_set_electron_coord      (qmckl_context context, const double* coord);

#+NAME:pre2

#+NAME:post2

To set the number of electrons, we give the number of up-spin and down-spin electrons to the context and we set the number of walkers.

The following function sets the electron coordinates of all the walkers. When this is done, the pointers to the old and new sets of coordinates are swapped, and the new coordinates are overwritten. This can be done only when the data relative to electrons have been set.

Test 

/* Reference input data */

#define up_num      ((int64_t) 3)
#define down_num    ((int64_t) 2)
#define walk_num    ((int64_t) 2)
#define num         (up_num+down_num)

double coord[walk_num*3*num] =
{ 7.303633091022677881e+00, 1.375868694453235719e+01, 1.167371490471771217e-01,
4.547755371567960836e+00, 3.245907105524011182e+00, 2.410764357550297110e-01,
5.932816068137344523e+00, 1.491671465549257469e+01, 3.825374039119375236e-01,
7.347336142660052083e+00, 1.341946976062362129e+00, 1.648917914228352322e+00,
5.735221530102248444e+00, 1.064667491680036271e+01, 4.227201772236627297e-01,
8.099550978782254163e+00, 6.861498941099086757e+00, 4.015884841159429036e-02,
1.014757367558326173e+01, 5.219335322173662917e+00, 5.037004126899931322e-02,
1.484094322159507051e+01, 9.777903829455864226e+00, 5.243007994024882767e-02,
9.081723054990456845e+00, 5.499568496038920173e+00, 2.910446438899221347e-02,
2.583154239492383653e+00, 1.442282811294904432e+00, 6.387191629878670451e-02 };

/* --- */

qmckl_exit_code rc;

munit_assert(!qmckl_electron_provided(context));

rc = qmckl_set_electron_num (context, up_num, down_num);
munit_assert_int64(rc, ==, QMCKL_SUCCESS);
munit_assert(!qmckl_electron_provided(context));

rc = qmckl_set_electron_walk_num (context, walk_num);
munit_assert_int64(rc, ==, QMCKL_SUCCESS);
munit_assert(qmckl_electron_provided(context));

rc = qmckl_set_electron_coord (context, coord);
munit_assert_int64(rc, ==, QMCKL_SUCCESS);

Computation

The computed data is stored in the context so that it can be reused by different kernels. To ensure that the data is valid, for each computed data the date of the context is stored when it is computed. To know if some data needs to be recomputed, we check if the date of the dependencies are more recent than the date of the data to compute. If it is the case, then the data is recomputed and the current date is stored.

Electron-electron distances

Get 

qmckl_exit_code qmckl_get_electron_ee_distance(qmckl_context context, double* distance);

Compute

qmckl_context context in Global state
int64_t elec_num in Number of electrons
int64_t walk_num in Number of walkers
double coord[walk_num][3][elec_num] in Electron coordinates
double ee_distance[walk_num][elec_num][elec_num] out Electron-electron distances 
integer function qmckl_compute_ee_distance_f(context, elec_num, walk_num, coord, ee_distance) &
 result(info)
use qmckl
implicit none
integer(qmckl_context), intent(in)  :: context
integer*8             , intent(in)  :: elec_num
integer*8             , intent(in)  :: walk_num
double precision      , intent(in)  :: coord(elec_num,3,walk_num)
double precision      , intent(out) :: ee_distance(elec_num,elec_num,walk_num)

integer*8 :: k

info = QMCKL_SUCCESS

if (context == QMCKL_NULL_CONTEXT) then
 info = QMCKL_INVALID_CONTEXT
 return
endif

if (elec_num <= 0) then
 info = QMCKL_INVALID_ARG_2
 return
endif

if (walk_num <= 0) then
 info = QMCKL_INVALID_ARG_3
 return
endif

!$OMP PARALLEL DO DEFAULT(NONE) &
!$OMP SHARED(elec_num, walk_num, coord, ee_distance)
!$OMP PRIVATE(k)
do k=1,walk_num
 info = qmckl_distance(context, 'T', 'T', elec_num, elec_num, &
      coord(1,1,k), elec_num, &
      coord(1,1,k), elec_num, &
      ee_distance(1,1,k), elec_num)
end do
!$OMP END PARALLEL DO

end function qmckl_compute_ee_distance_f

Test 

/* Reference input data */

munit_assert(qmckl_electron_provided(context));

double distance[walk_num*num*num];
rc = qmckl_get_electron_ee_distance(context, distance);
rc = qmckl_get_electron_ee_distance(context, distance);
munit_assert_double(distance[0], ==, 0.);
munit_assert_double(distance[1], ==, distance[num]);
munit_assert_double_equal(distance[1], 8.6114953086801, 12);