QuarterFloat.hpp

// Copyright (c) 2021 Graphcore Ltd. All rights reserved.
 
#ifndef poplar_QuarterFloat_hpp_
#define poplar_QuarterFloat_hpp_
 
#if defined(__IPU__) && defined(__IPU_ARCH_VERSION__) &&                       \
    __IPU_ARCH_VERSION__ >= 21
 
#include <ipudef.h>
 
namespace poplar {
 
#ifndef __SUPERVISOR__
inline half toHalf(quarter q, quarter_metadata md) {
  return quarterToHalf(&q, md);
}
 
inline quarter toQuarter(half h, quarter_metadata md) {
  return halfToQuarter(&h, md);
}
#endif // __SUPERVISOR__
 
} // namespace poplar
 
#else
 
// This type does not support any arithmetic operations
struct quarter {
  unsigned char value;
 
  quarter(unsigned x) { value = x; };
};
 
typedef struct quarter_metadata {
  enum format { f143, f152 } fmt;
  signed char scale;
} quarter_metadata;
 
// Some cpp files (example:CastFloatToGf8.cpp) always include ipudef.h
// To prevent conflict, before including HalfFloat first check if
// _IPUDEF_H is not defined.
// __QUARTER_FOR_IPU__ should be defined externally where these declarations
// are required on Ipu as well as IpuModel
#if (!defined(__IPU__) && !defined(_IPUDEF_H)) || defined(__QUARTER_FOR_IPU__)
 
#include <poplar/HalfFloat.hpp>
 
namespace poplar {
 
half quarterToHalf(quarter q, quarter_metadata md);
 
float quarterToFloat(quarter q, quarter_metadata md);
 
quarter halfToQuarter(half h, quarter_metadata md);
 
quarter floatToQuarter(float h, quarter_metadata md);
 
inline half toFloat(quarter q, quarter_metadata md) {
  return quarterToFloat(q, md);
}
 
inline half toHalf(quarter q, quarter_metadata md) {
  return quarterToHalf(q, md);
}
 
template <typename T> inline quarter toQuarter(T val, quarter_metadata md) {
  return floatToQuarter(val, md);
}
 
template <> inline quarter toQuarter<half>(half val, quarter_metadata md) {
  return floatToQuarter(val, md);
}
 
} // namespace poplar
 
#endif // !defined(_IPUDEF_H)
 
#endif
 
typedef unsigned char MetadataType;
 
namespace poplar {
 
inline quarter_metadata unpackMetadata(const MetadataType *in) {
  quarter_metadata out;
  constexpr auto formatBit = 7;
  constexpr auto formatBitMask = (1 << formatBit);
  constexpr auto scaleSignBit = 5;
  constexpr auto scaleSignBitMask = (1 << scaleSignBit);
  constexpr auto scaleMask = (1 << (scaleSignBit + 1)) - 1;
  constexpr auto scaleSignExtendMask = 0xff ^ scaleMask;
 
  out.fmt =
      *in & formatBitMask ? quarter_metadata::f143 : quarter_metadata::f152;
  out.scale = static_cast<char>(*in & scaleMask);
  if (out.scale & scaleSignBitMask) {
    out.scale |= scaleSignExtendMask;
  }
  return out;
}
 
} // namespace poplar
 
#endif // poplar_QuarterFloat_hpp_