annotate xthresh.c @ 402:58b88ab69424 api-inversion

Move the struct adb definition from the auidioDB_API.h into the
audioDB-internals.h header file, leaving only the typedef behind.

Thus a user of the API sees only an incomplete type, which cannot be
instantiated (but /pointers/ to it can); there's then less temptation to
break the abstraction barrier by using structure fields in client code.

Not only that, but we can now safely put C++ stuff in the structure.
Take advantage of this by putting a std::set<std::string> in there, to
hold all the keys currently in the database; populate this field on
audiodb_open() (and delete it on audiodb_close).  This will be useful
when we come to implement variants of audiodb_insert().

#include <gsl/gsl_sf.h>
#include <stdio.h>
#include <stdlib.h>
#include <math.h>

int main(int argc, char *argv[]) {
  if(argc != 4) {
    fprintf(stderr, "Wrong number of arguments: %d\n", argc);
    exit(1);
  }

  long int meanN = strtol(argv[1], NULL, 10);

  double d = strtod(argv[2], NULL);
  double sigma2 = strtod(argv[3], NULL);

  double logw = (2 / d) * gsl_sf_log(-gsl_sf_log(0.99));
  double logxthresh = gsl_sf_log(sigma2) + logw
    - (2 / d) * gsl_sf_log(meanN)
    - gsl_sf_log(d/2)
    - (2 / d) * gsl_sf_log(2 / d)
    + (2 / d) * gsl_sf_lngamma(d / 2);

  printf("w: %f\n", exp(logw));
  printf("x_thresh: %f\n", exp(logxthresh));
  exit(0);
}