Beispiel #1
0
T float_advance(T val, int distance, const Policy& pol)
{
   //
   // Error handling:
   //
   static const char* function = "float_advance<%1%>(%1%, int)";
   if(!(boost::math::isfinite)(val))
      return policies::raise_domain_error<T>(
         function,
         "Argument val must be finite, but got %1%", val, pol);

   if(val < 0)
      return -float_advance(-val, -distance, pol);
   if(distance == 0)
      return val;
   if(distance == 1)
      return float_next(val, pol);
   if(distance == -1)
      return float_prior(val, pol);
   BOOST_MATH_STD_USING
   int expon;
   frexp(val, &expon);
   T limit = ldexp((distance < 0 ? T(0.5f) : T(1)), expon);
   if(val <= tools::min_value<T>())
   {
      limit = sign(T(distance)) * tools::min_value<T>();
   }
   T limit_distance = float_distance(val, limit);
   while(fabs(limit_distance) < abs(distance))
   {
      distance -= itrunc(limit_distance);
      val = limit;
      if(distance < 0) 
      {
         limit /= 2;
         expon--;
      }
      else
      {
         limit *= 2;
         expon++;
      }
      limit_distance = float_distance(val, limit);
   }
   if((0.5f == frexp(val, &expon)) && (distance < 0))
      --expon;
   T diff = 0;
   if(val != 0)
      diff = distance * ldexp(T(1), expon - tools::digits<T>());
   if(diff == 0)
      diff = distance * detail::get_smallest_value<T>();
   return val += diff;
}
Beispiel #2
0
T float_prior(const T& val, const Policy& pol)
{
   BOOST_MATH_STD_USING
   int expon;
   static const char* function = "float_prior<%1%>(%1%)";

   int fpclass = (pdalboost::math::fpclassify)(val);

   if((fpclass == FP_NAN) || (fpclass == FP_INFINITE))
   {
      if(val > 0)
         return tools::max_value<T>();
      return policies::raise_domain_error<T>(
         function,
         "Argument must be finite, but got %1%", val, pol);
   }

   if(val <= -tools::max_value<T>())
      return -policies::raise_overflow_error<T>(function, 0, pol);

   if(val == 0)
      return -detail::get_smallest_value<T>();

   if((fpclass != FP_SUBNORMAL) && (fpclass != FP_ZERO) && (fabs(val) < detail::get_min_shift_value<T>()) && (val != tools::min_value<T>()))
   {
      //
      // Special case: if the value of the least significant bit is a denorm, and the result 
      // would not be a denorm, then shift the input, increment, and shift back.
      // This avoids issues with the Intel SSE2 registers when the FTZ or DAZ flags are set.
      //
      return ldexp(float_prior(T(ldexp(val, 2 * tools::digits<T>())), pol), -2 * tools::digits<T>());
   }

   T remain = frexp(val, &expon);
   if(remain == 0.5)
      --expon; // when val is a power of two we must reduce the exponent
   T diff = ldexp(T(1), expon - tools::digits<T>());
   if(diff == 0)
      diff = detail::get_smallest_value<T>();
   return val - diff;
}
Beispiel #3
0
inline T float_prior(const T& val)
{
   return float_prior(val, policies::policy<>());
}
Beispiel #4
0
T float_advance(T val, int distance, const Policy& pol)
{
   BOOST_MATH_STD_USING
   //
   // Error handling:
   //
   static const char* function = "float_advance<%1%>(%1%, int)";

   int fpclass = (pdalboost::math::fpclassify)(val);

   if((fpclass == FP_NAN) || (fpclass == FP_INFINITE))
      return policies::raise_domain_error<T>(
         function,
         "Argument val must be finite, but got %1%", val, pol);

   if(val < 0)
      return -float_advance(-val, -distance, pol);
   if(distance == 0)
      return val;
   if(distance == 1)
      return float_next(val, pol);
   if(distance == -1)
      return float_prior(val, pol);

   if(fabs(val) < detail::get_min_shift_value<T>())
   {
      //
      // Special case: if the value of the least significant bit is a denorm, 
      // implement in terms of float_next/float_prior.
      // This avoids issues with the Intel SSE2 registers when the FTZ or DAZ flags are set.
      //
      if(distance > 0)
      {
         do{ val = float_next(val, pol); } while(--distance);
      }
      else
      {
         do{ val = float_prior(val, pol); } while(++distance);
      }
      return val;
   }

   int expon;
   frexp(val, &expon);
   T limit = ldexp((distance < 0 ? T(0.5f) : T(1)), expon);
   if(val <= tools::min_value<T>())
   {
      limit = sign(T(distance)) * tools::min_value<T>();
   }
   T limit_distance = float_distance(val, limit);
   while(fabs(limit_distance) < abs(distance))
   {
      distance -= itrunc(limit_distance);
      val = limit;
      if(distance < 0) 
      {
         limit /= 2;
         expon--;
      }
      else
      {
         limit *= 2;
         expon++;
      }
      limit_distance = float_distance(val, limit);
      if(distance && (limit_distance == 0))
      {
         policies::raise_evaluation_error<T>(function, "Internal logic failed while trying to increment floating point value %1%: most likely your FPU is in non-IEEE conforming mode.", val, pol);
      }
   }
   if((0.5f == frexp(val, &expon)) && (distance < 0))
      --expon;
   T diff = 0;
   if(val != 0)
      diff = distance * ldexp(T(1), expon - tools::digits<T>());
   if(diff == 0)
      diff = distance * detail::get_smallest_value<T>();
   return val += diff;
}