#include <stdio.h>

bool is_clear_bit(const float koef,unsigned idx)
{
  bool result = false;
  if( koef <= 1 )
    {
      float map_to_node = koef * float(idx);
      unsigned source = (unsigned)map_to_node;
      float map_to_node_next = map_to_node + koef;
      result = source >= map_to_node && map_to_node+1 < source+1
            || source <= map_to_node && map_to_node_next <= source+1;
    }
  return result;
}

bool is_clear_bit2( const float koef, unsigned idx )
{
  if( koef <= 1 )
    {
      return unsigned( koef * float(idx) ) >= float( koef * float(idx) ) && float( koef * float(idx) ) + 1 <  unsigned( koef * float(idx) ) + 1
          || unsigned( koef * float(idx) ) <= float( koef * float(idx) ) && float( koef * float(idx + 1) ) <= unsigned( koef * float(idx) ) + 1
      ;
    }
  else
    return false;
}

int main(int a_argc, char** a_argv)
{
  for(unsigned i=0;i<100;++i)
    {
      printf( "%d = %d, %d\n", i, is_clear_bit(0.1f,i)?1:0, is_clear_bit2( 0.1f, i )?1:0 );
    }
  return 0;
}

ziv@mule:~/tmp$ g++ -o float float.cpp && ./float 
0 = 1, 1
1 = 1, 1
...
87 = 1, 1
88 = 1, 1
89 = 0, 1
90 = 1, 1
91 = 1, 1
92 = 1, 1
93 = 1, 1
94 = 1, 1
95 = 1, 1
96 = 1, 1
97 = 1, 1
98 = 1, 1
99 = 0, 1

        result = source >= map_to_node && map_to_node+1 < source+1
              || source <= map_to_node && map_to_node_next <= source+1;