Custom parameters

The W-SLDA toolkit provides a framework for creating flexible parametrization of formulas. List of numbers (of double type) that can be passed from an input file to the code is called custom parameters. In the input file they start with tag:

# Custom parameters
params0            0.0 # value of the parameter 
params1            1.0 # value of the parameter
params2            2.0 # value of the parameter
# ... and so on ...

Maximal number of parameters is specified in predefines.h by macro-variable:

// Maximal number of parameters in params array
#define MAX_USER_PARAMS 32

When the program reads the input file custom parameters are uploaded into params array in a such way that paramsk is assigned to params[k]. Pointer to the array is passed to each user-defined function, for example:

double v_ext(int ix, int iy, int iz, int it, int spin, double *params, size_t extra_data_size, void *extra_data)
{
    // ADD HERE FORMULA FOR V_ext(r)
    double V_ext = 0.0;

    return V_ext; 
}

During the self-iteration process, before params array is passed to user-defined functions the array can be processed by function:

/** 
 * THIS FUNCTION IS CALLED DURING THE SELF-CONSISTENT PROCESS.
 * After loading params array from input file, the parameters are processed by this routine.
 * The routine is executed at beginning of each iteration.
 * @param params array of size MAX_USER_PARAMS with parameters from input file. 
 * @param kF typical Fermi momentum scale of the problem. 
 *           kF=referencekF if the referencekF tag is indicated in the input file, 
 *           otherwise to kF value is assigned according formula kF=(3*pi^2*n)^{1/3}, where n corresponds to maximal density.
 *           You can also set kF at request in this function using (*kF)=myvalue;
 * @param mu array with chemical potentials: mu[SPINA] and mu[SPINB]. 
 * @param extra_data_size size of extra_data in bytes, if extra_data size=0 the optional data is not uploaded
 * @param extra_data optional set of data uploaded by load_extra_data()
 * */
void process_params(double *params, double *kF, double *mu, size_t extra_data_size, void *extra_data)
{
    // PROCESS INPUT FILE PARAMETERS 

}

Usage of process_params( ) allows for parametrization of user-defined functions in terms of dimensionless values, which are typically more intuitive. For example:

params2            2.0 # barrier height, in units of chemical potential mu_a

and process_params( ) converts params2 into dimensional quantity

void process_params(double *params, double *kF, double *mu, size_t extra_data_size, void *extra_data)
{
    params[2]*=mu[SPINA]; // convert to dimensional form
}

Passing external data to user-defined functions

To each user-defined function, arbitrary external data can be passed called extra data. The extra data is uploading before the self-consistent starts. In order to activate this option user must provide content of functions:

/**
 * This function provides size of extra_data array, in bytes.
 * The extra_data of specified size will be allocated by the main process.
 * This function is thread-safe.
 * @param params with input file parameters. 
 *              NOTE: the array contains bare input file values, not processed by process_params()!
 * @return size of the extra_data array that needs to be allocated, if 0 then extra_data will not be allocated.
 * */
size_t get_extra_data_size(double *params)
{
    return 0;
}

and

/**
 * This function loads data into extra_data array.
 * This function is thread-safe.
 * @param size size of array computed using function get_extra_data_size()
 * @param extra_data pointer to array that should be filled with data
 * @param params with input file parameters. 
 *               NOTE: the array contains bare input file values, not processed by process_params()!
 * @return 0 if load is successful, otherwise return error code. If nonzero value is returned the main code will terminate.
 * */
int load_extra_data(size_t size, void *extra_data, double *params)
{
    return 0;
}

Predefined variables

Each variable defined in predefines.h is accessible over entire file problem-definition.h. User can defined new variable in predefines.h, like

#define MYVALUE 10.0;

which can be next used in user-defined functions:

double v_ext(int ix, int iy, int iz, int it, int spin, double *params, size_t extra_data_size, void *extra_data)
{
    // ADD HERE FORMULA FOR V_ext(r)
    double V_ext = MYVALUE;  // it will assign value as given in predefines.h

    return V_ext; 
}