Electrons

Context

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:

`date`	uint64_t	Last modification date of the coordinates
`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

Data structure

typedef struct qmckl_electron_struct {
int64_t   date;
int64_t   num;
int64_t   up_num;
int64_t   down_num;
int64_t   walk_num;
double*   coord_new;
double*   coord_old;
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

Access to scalars copies the values at the passed address, and for array values a pointer to the array is returned.

int64_t   qmckl_get_electron_num        (const qmckl_context context);
int64_t   qmckl_get_electron_up_num     (const qmckl_context context);
int64_t   qmckl_get_electron_down_num   (const qmckl_context context);
int64_t   qmckl_get_electron_walk_num   (const qmckl_context context);
double*   qmckl_get_electron_coord_new  (const qmckl_context context);
double*   qmckl_get_electron_coord_old  (const qmckl_context context);

bool      qmckl_electron_provided       (const qmckl_context context);

#+NAME:post

if ( (ctx->electron.uninitialized & mask) != 0) {
return NULL;
}

int64_t qmckl_get_electron_num (const qmckl_context context) {

if (qmckl_context_check(context) == QMCKL_NULL_CONTEXT) {
 return (char) 0;
}

qmckl_context_struct* const ctx = (qmckl_context_struct* const) context;
assert (ctx != NULL);

int32_t mask = 1;

if ( (ctx->electron.uninitialized & mask) != 0) {
 return (int64_t) 0;
}

assert (ctx->electron.num > (int64_t) 0);
return ctx->electron.num;
}


int64_t qmckl_get_electron_up_num (const qmckl_context context) {
if (qmckl_context_check(context) == QMCKL_NULL_CONTEXT) {
 return (int64_t) 0;
}

qmckl_context_struct* const ctx = (qmckl_context_struct* const) context;
assert (ctx != NULL);

int32_t mask = 1 << 1;

if ( (ctx->electron.uninitialized & mask) != 0) {
 return (int64_t) 0;
}

assert (ctx->electron.up_num > (int64_t) 0);
return ctx->electron.up_num;
}


int64_t qmckl_get_electron_down_num (const qmckl_context context) {
if (qmckl_context_check(context) == QMCKL_NULL_CONTEXT) {
 return (int64_t) 0;
}

qmckl_context_struct* const ctx = (qmckl_context_struct* const) context;
assert (ctx != NULL);

int32_t mask = 1 << 2;

if ( (ctx->electron.uninitialized & mask) != 0) {
 return (int64_t) 0;
}

assert (ctx->electron.down_num >= (int64_t) 0);
return ctx->electron.down_num;
}


int64_t qmckl_get_electron_walk_num (const qmckl_context context) {
if (qmckl_context_check(context) == QMCKL_NULL_CONTEXT) {
 return (int64_t) 0;
}

qmckl_context_struct* const ctx = (qmckl_context_struct* const) context;
assert (ctx != NULL);

int32_t mask = 1 << 3;

if ( (ctx->electron.uninitialized & mask) != 0) {
 return (int64_t) 0;
}

assert (ctx->electron.walk_num > (int64_t) 0);
return ctx->electron.walk_num;
}



bool qmckl_electron_provided(const qmckl_context context) {

if (qmckl_context_check(context) == QMCKL_NULL_CONTEXT) {
 return false;
}

qmckl_context_struct* const ctx = (qmckl_context_struct* const) context;
assert (ctx != NULL);

return ctx->electron.provided;
}

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

if (qmckl_context_check(context) == QMCKL_NULL_CONTEXT) {
return QMCKL_NULL_CONTEXT;
}

qmckl_context_struct* const ctx = (qmckl_context_struct* const) context;

#+NAME:post2

ctx->electron.uninitialized &= ~mask; 
ctx->electron.provided = (ctx->electron.uninitialized == 0);

if (ctx->electron.provided) {
if (ctx->electron.coord_new != NULL) {
 qmckl_free(context, ctx->electron.coord_new);
 ctx->electron.coord_new = NULL;
}
if (ctx->electron.coord_old != NULL) {
 qmckl_free(context, ctx->electron.coord_old);
 ctx->electron.coord_old = NULL;
}

qmckl_memory_info_struct mem_info = qmckl_memory_info_struct_zero;
mem_info.size = ctx->electron.num * ctx->electron.walk_num * 3 * sizeof(double);

double* coord_new = (double*) qmckl_malloc(context, mem_info);
if (coord_new == NULL) {
 return qmckl_failwith( context,
                        QMCKL_ALLOCATION_FAILED,
                        "qmckl_set_electron_num",
                        NULL);
}
ctx->electron.coord_new = coord_new;

double* coord_old = (double*) qmckl_malloc(context, mem_info);
if (coord_old == NULL) {
 return qmckl_failwith( context,
                        QMCKL_ALLOCATION_FAILED,
                        "qmckl_set_electron_num",
                        NULL);
}
ctx->electron.coord_old = coord_old;
}

return QMCKL_SUCCESS;

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

qmckl_exit_code qmckl_set_electron_num(qmckl_context context,
                                    const int64_t up_num,
                                    const int64_t down_num) {
<<pre2>>

if (up_num <= 0) {
 return qmckl_failwith( context,
                        QMCKL_INVALID_ARG_2,
                        "qmckl_set_electron_num",
                        "up_num <= 0");
}

if (down_num <= 0) {
 return qmckl_failwith( context,
                        QMCKL_INVALID_ARG_3,
                        "qmckl_set_electron_num",
                        "down_num <= 0");
}

int32_t mask = (1 << 3) -1;

ctx->electron.up_num = up_num;
ctx->electron.down_num = down_num;
ctx->electron.num = up_num + down_num;

<<post2>>
}

Then, we set the number of walkers:

qmckl_exit_code qmckl_set_electron_walk_num(qmckl_context context, const int64_t walk_num) {
<<pre2>>

if (walk_num <= 0) {
 return qmckl_failwith( context,
                        QMCKL_INVALID_ARG_2,
                        "qmckl_set_electron_walk_num",
                        "walk_num <= 0");
}

int32_t mask = 1 << 3;
ctx->electron.walk_num = walk_num;

<<post2>>
}

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.

qmckl_exit_code  qmckl_set_electron_coord(qmckl_context context, const double* coord) {
<<pre2>>

const int64_t num = qmckl_get_electron_num(context);
if (num == 0L) {
 return qmckl_failwith( context,
                        QMCKL_FAILURE,
                        "qmckl_set_electron_coord",
                        "num is not set");
}
 
const int64_t walk_num = qmckl_get_electron_walk_num(context);
if (walk_num == 0L) {
 return qmckl_failwith( context,
                        QMCKL_FAILURE,
                        "qmckl_set_electron_coord",
                        "walk_num is not set");
}
 
/* If num and walk_num are set, the arrays should be allocated */
assert (ctx->electron.coord_old != NULL);
assert (ctx->electron.coord_new != NULL);

/* Increment the date of the context */
ctx->date += 1UL;

/* Swap pointers */
double * swap;
swap = ctx->electron.coord_old;
ctx->electron.coord_old = ctx->electron.coord_new;
ctx->electron.coord_new = swap;

memcpy(ctx->electron.coord_new, coord, walk_num * num * 3 * sizeof(double));
ctx->electron.date = ctx->date;

return QMCKL_SUCCESS;
 
}

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);

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