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      1 /* Copyright 2015 The TensorFlow Authors. All Rights Reserved.
      2 
      3 Licensed under the Apache License, Version 2.0 (the "License");
      4 you may not use this file except in compliance with the License.
      5 You may obtain a copy of the License at
      6 
      7     http://www.apache.org/licenses/LICENSE-2.0
      8 
      9 Unless required by applicable law or agreed to in writing, software
     10 distributed under the License is distributed on an "AS IS" BASIS,
     11 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     12 See the License for the specific language governing permissions and
     13 limitations under the License.
     14 ==============================================================================*/
     15 
     16 #ifndef TENSORFLOW_CORE_FRAMEWORK_TYPES_H_
     17 #define TENSORFLOW_CORE_FRAMEWORK_TYPES_H_
     18 
     19 #include <map>
     20 #include <set>
     21 #include <string>
     22 
     23 #include "third_party/eigen3/unsupported/Eigen/CXX11/Tensor"
     24 // Disable clang-format to prevent 'FixedPoint' header from being included
     25 // before 'Tensor' header on which it depends.
     26 // clang-format off
     27 #include "third_party/eigen3/unsupported/Eigen/CXX11/FixedPoint"
     28 // clang-format on
     29 #include "tensorflow/core/framework/bfloat16.h"
     30 #include "tensorflow/core/framework/numeric_types.h"
     31 #include "tensorflow/core/framework/resource_handle.h"
     32 #include "tensorflow/core/framework/types.pb.h"
     33 #include "tensorflow/core/lib/core/stringpiece.h"
     34 #include "tensorflow/core/lib/gtl/array_slice.h"
     35 #include "tensorflow/core/lib/gtl/inlined_vector.h"
     36 #include "tensorflow/core/platform/logging.h"
     37 #include "tensorflow/core/platform/types.h"
     38 
     39 namespace tensorflow {
     40 
     41 class Variant;
     42 
     43 // MemoryType is used to describe whether input or output Tensors of
     44 // an OpKernel should reside in "Host memory" (e.g., CPU memory) or
     45 // "Device" Memory (CPU memory for CPU devices, GPU memory for GPU
     46 // devices).
     47 enum MemoryType {
     48   DEVICE_MEMORY = 0,
     49   HOST_MEMORY = 1,
     50 };
     51 
     52 // A DeviceType is just a string, but we wrap it up in a class to give
     53 // some type checking as we're passing these around
     54 class DeviceType {
     55  public:
     56   DeviceType(const char* type)  // NOLINT(runtime/explicit)
     57       : type_(type) {}
     58 
     59   explicit DeviceType(StringPiece type) : type_(type.data(), type.size()) {}
     60 
     61   const char* type() const { return type_.c_str(); }
     62   const string& type_string() const { return type_; }
     63 
     64   bool operator<(const DeviceType& other) const;
     65   bool operator==(const DeviceType& other) const;
     66   bool operator!=(const DeviceType& other) const { return !(*this == other); }
     67 
     68  private:
     69   string type_;
     70 };
     71 std::ostream& operator<<(std::ostream& os, const DeviceType& d);
     72 
     73 // Convenient constants that can be passed to a DeviceType constructor
     74 TF_EXPORT extern const char* const DEVICE_CPU;   // "CPU"
     75 TF_EXPORT extern const char* const DEVICE_GPU;   // "GPU"
     76 TF_EXPORT extern const char* const DEVICE_SYCL;  // "SYCL"
     77 
     78 template <typename Device>
     79 struct DeviceName {};
     80 
     81 template <>
     82 struct DeviceName<Eigen::ThreadPoolDevice> {
     83   static const std::string value;
     84 };
     85 
     86 #if GOOGLE_CUDA
     87 template <>
     88 struct DeviceName<Eigen::GpuDevice> {
     89   static const std::string value;
     90 };
     91 #endif  // GOOGLE_CUDA
     92 
     93 #ifdef TENSORFLOW_USE_SYCL
     94 template <>
     95 struct DeviceName<Eigen::SyclDevice> {
     96   static const std::string value;
     97 };
     98 #endif  // TENSORFLOW_USE_SYCL
     99 
    100 typedef gtl::InlinedVector<MemoryType, 4> MemoryTypeVector;
    101 typedef gtl::ArraySlice<MemoryType> MemoryTypeSlice;
    102 
    103 typedef gtl::InlinedVector<DataType, 4> DataTypeVector;
    104 typedef gtl::ArraySlice<DataType> DataTypeSlice;
    105 
    106 typedef gtl::InlinedVector<DeviceType, 4> DeviceTypeVector;
    107 typedef gtl::InlinedVector<std::pair<DeviceType, int32>, 4>
    108     PrioritizedDeviceTypeVector;
    109 
    110 // Convert the enums to strings for errors:
    111 string DataTypeString(DataType dtype);
    112 string DeviceTypeString(const DeviceType& device_type);
    113 string DataTypeSliceString(const DataTypeSlice dtypes);
    114 inline string DataTypeVectorString(const DataTypeVector& dtypes) {
    115   return DataTypeSliceString(dtypes);
    116 }
    117 
    118 // DataTypeSet represents a set of DataType values as a simple and efficient
    119 // bit mask.  Note that DataTypeSet cannot represent all DataType values; it
    120 // cannot represent any of the DT_*_REF values.
    121 class DataTypeSet {
    122  private:
    123   const uint32 mask_;
    124 
    125   static constexpr uint32 kNumBits = 32;
    126 
    127  public:
    128   constexpr DataTypeSet(const DataTypeSet& other) : mask_(other.mask_) {}
    129   explicit constexpr DataTypeSet(uint32 mask) : mask_(mask) {}
    130 
    131   constexpr bool Contains(DataType dt) const {
    132     return (static_cast<uint32>(dt) < kNumBits) &&
    133            ((mask_ >> static_cast<uint32>(dt)) & 1u) != 0u;
    134   }
    135 
    136   class Iterator {
    137     const DataTypeSet& set_;
    138     uint32 pos_;
    139 
    140    public:
    141     Iterator(const DataTypeSet& set, uint32 pos) : set_(set), pos_(pos) {
    142       DCHECK_LE(pos, kNumBits);
    143     }
    144     DataType operator*() const { return static_cast<DataType>(pos_); }
    145     Iterator& operator++() {
    146       ++pos_;
    147       DCHECK_LE(pos_, kNumBits);
    148       if (pos_ < kNumBits) {
    149         uint32 remaining_mask = set_.mask_ >> pos_;
    150         if (remaining_mask != 0u) {
    151           pos_ += ctz_uint32(remaining_mask);
    152         }
    153       }
    154       DCHECK_LE(pos_, kNumBits);
    155       return *this;
    156     }
    157     bool operator==(const Iterator& other) const { return pos_ == other.pos_; }
    158     bool operator!=(const Iterator& other) const { return !(*this == other); }
    159     size_t operator-(const Iterator& other) const {
    160       return this->pos_ - other.pos_;
    161     }
    162   };
    163 
    164   static uint32 ctz_uint32(uint32 x) {
    165     DCHECK_NE(x, 0u);
    166 #ifdef __GNUC__
    167     return __builtin_ctz(x);
    168 #else
    169     uint32 n = 0u;
    170     while ((x & 1u) == 0u) {
    171       x >>= 1;
    172       ++n;
    173     }
    174     return n;
    175 #endif
    176   }
    177 
    178   static uint32 clz_uint32(uint32 x) {
    179     DCHECK_NE(x, 0u);
    180 #ifdef __GNUC__
    181     return __builtin_clz(x);
    182 #else
    183     uint32 n = 0u;
    184     while ((x >> (kNumBits - 1u)) == 0u) {
    185       x <<= 1;
    186       ++n;
    187     }
    188     return n;
    189 #endif
    190   }
    191 
    192   Iterator begin() const {
    193     // The begin position is the index of the first bit set to 1 in the entire
    194     // bit mask. If there are no bits set to 1, then the index is 0.
    195     if (mask_ != 0) {
    196       return Iterator(*this, ctz_uint32(mask_));
    197     }
    198     // The set is empty.
    199     return Iterator(*this, 0);
    200   }
    201 
    202   Iterator end() const {
    203     // The end position is the index of the highest bit that is set, plus 1.
    204     // If there are no bits set to 1, then the index is 0.
    205     if (mask_ != 0) {
    206       return Iterator(*this, kNumBits - clz_uint32(mask_));
    207     }
    208     // The set is empty.
    209     return Iterator(*this, 0);
    210   }
    211 
    212   size_t size() const {
    213 #if defined(__GNUC__)
    214     return __builtin_popcount(mask_);
    215 #else
    216     size_t n = 0;
    217     uint32 x = mask_;
    218     while (x > 0) {
    219       n += x & 1u;
    220       x >>= 1;
    221     }
    222     return n;
    223 #endif
    224   }
    225 
    226   constexpr DataTypeSet operator|(const DataTypeSet& other) const {
    227     return DataTypeSet(mask_ | other.mask_);
    228   }
    229 };
    230 
    231 // If "sp" names a valid type, store it in "*dt" and return true.  Otherwise,
    232 // return false.
    233 bool DataTypeFromString(StringPiece sp, DataType* dt);
    234 
    235 constexpr inline DataTypeSet ToSet(DataType dt) {
    236   return DataTypeSet(1u << static_cast<uint32>(dt));
    237 }
    238 
    239 // DT_FLOAT + kDataTypeRefOffset == DT_FLOAT_REF, etc.
    240 enum { kDataTypeRefOffset = 100 };
    241 inline bool IsRefType(DataType dtype) {
    242   return dtype > static_cast<DataType>(kDataTypeRefOffset);
    243 }
    244 inline DataType MakeRefType(DataType dtype) {
    245   DCHECK(!IsRefType(dtype));
    246   return static_cast<DataType>(dtype + kDataTypeRefOffset);
    247 }
    248 inline DataType RemoveRefType(DataType dtype) {
    249   DCHECK(IsRefType(dtype));
    250   return static_cast<DataType>(dtype - kDataTypeRefOffset);
    251 }
    252 inline DataType BaseType(DataType dtype) {
    253   return IsRefType(dtype) ? RemoveRefType(dtype) : dtype;
    254 }
    255 
    256 // Returns true if the actual type is the same as or ref of the expected type.
    257 inline bool TypesCompatible(DataType expected, DataType actual) {
    258   return expected == actual || expected == BaseType(actual);
    259 }
    260 
    261 // Does not include _ref types.
    262 constexpr DataTypeSet kAllTypes =
    263     ToSet(DT_FLOAT) | ToSet(DT_DOUBLE) | ToSet(DT_INT32) | ToSet(DT_UINT8) |
    264     ToSet(DT_INT16) | ToSet(DT_UINT16) | ToSet(DT_INT8) | ToSet(DT_STRING) |
    265     ToSet(DT_COMPLEX64) | ToSet(DT_COMPLEX128) | ToSet(DT_INT64) |
    266     ToSet(DT_BOOL) | ToSet(DT_QINT8) | ToSet(DT_QUINT8) | ToSet(DT_QINT16) |
    267     ToSet(DT_QUINT16) | ToSet(DT_QINT32) | ToSet(DT_HALF) | ToSet(DT_RESOURCE) |
    268     ToSet(DT_VARIANT) | ToSet(DT_UINT32) | ToSet(DT_UINT64) |
    269     ToSet(DT_BFLOAT16);
    270 inline const DataTypeSet& AllTypes() { return kAllTypes; }
    271 
    272 #if !defined(IS_MOBILE_PLATFORM) || defined(SUPPORT_SELECTIVE_REGISTRATION)
    273 
    274 // Types that support '<' and '>'.
    275 constexpr DataTypeSet kRealNumberTypes =
    276     ToSet(DT_FLOAT) | ToSet(DT_DOUBLE) | ToSet(DT_INT32) | ToSet(DT_INT64) |
    277     ToSet(DT_UINT8) | ToSet(DT_INT16) | ToSet(DT_INT8) | ToSet(DT_UINT16) |
    278     ToSet(DT_HALF) | ToSet(DT_UINT32) | ToSet(DT_UINT64) | ToSet(DT_BFLOAT16);
    279 inline const DataTypeSet RealNumberTypes() { return kRealNumberTypes; }
    280 
    281 // Return the list of all numeric types.
    282 // Includes complex and quantized types.
    283 // NOTE: On Android, we only include the float and int32 types for now.
    284 const DataTypeSet kNumberTypes =
    285     ToSet(DT_FLOAT) | ToSet(DT_DOUBLE) | ToSet(DT_INT64) | ToSet(DT_INT32) |
    286     ToSet(DT_UINT8) | ToSet(DT_UINT16) | ToSet(DT_INT16) | ToSet(DT_INT8) |
    287     ToSet(DT_COMPLEX64) | ToSet(DT_COMPLEX128) | ToSet(DT_QINT8) |
    288     ToSet(DT_QUINT8) | ToSet(DT_QINT32) | ToSet(DT_HALF) | ToSet(DT_UINT32) |
    289     ToSet(DT_UINT64) | ToSet(DT_BFLOAT16);
    290 inline const DataTypeSet& NumberTypes() { return kNumberTypes; }
    291 
    292 constexpr DataTypeSet kQuantizedTypes = ToSet(DT_QINT8) | ToSet(DT_QUINT8) |
    293                                         ToSet(DT_QINT16) | ToSet(DT_QUINT16) |
    294                                         ToSet(DT_QINT32);
    295 inline const DataTypeSet& QuantizedTypes() { return kQuantizedTypes; }
    296 
    297 // Types that support '<' and '>', including quantized types.
    298 const DataTypeSet kRealAndQuantizedTypes =
    299     ToSet(DT_FLOAT) | ToSet(DT_DOUBLE) | ToSet(DT_INT32) | ToSet(DT_INT64) |
    300     ToSet(DT_UINT8) | ToSet(DT_UINT16) | ToSet(DT_INT16) | ToSet(DT_INT8) |
    301     ToSet(DT_QINT8) | ToSet(DT_QUINT8) | ToSet(DT_QINT16) | ToSet(DT_QUINT16) |
    302     ToSet(DT_QINT32) | ToSet(DT_HALF) | ToSet(DT_BFLOAT16);
    303 inline const DataTypeSet& RealAndQuantizedTypes() {
    304   return kRealAndQuantizedTypes;
    305 }
    306 
    307 #elif defined(__ANDROID_TYPES_FULL__)
    308 
    309 constexpr DataTypeSet kRealNumberTypes =
    310     ToSet(DT_FLOAT) | ToSet(DT_INT32) | ToSet(DT_INT64) | ToSet(DT_HALF);
    311 inline DataTypeSet RealNumberTypes() { return kRealNumberTypes; }
    312 
    313 constexpr DataTypeSet kNumberTypes =
    314     ToSet(DT_FLOAT) | ToSet(DT_INT32) | ToSet(DT_INT64) | ToSet(DT_QINT8) |
    315     ToSet(DT_QUINT8) | ToSet(DT_QINT32) | ToSet(DT_HALF);
    316 inline DataTypeSet NumberTypes() { return kNumberTypes; }
    317 
    318 constexpr DataTypeSet kQuantizedTypes = ToSet(DT_QINT8) | ToSet(DT_QUINT8) |
    319                                         ToSet(DT_QINT16) | ToSet(DT_QUINT16) |
    320                                         ToSet(DT_QINT32);
    321 inline DataTypeSet QuantizedTypes() { return kQuantizedTypes; }
    322 
    323 constexpr DataTypeSet kRealAndQuantizedTypes =
    324     ToSet(DT_FLOAT) | ToSet(DT_INT32) | ToSet(DT_INT64) | ToSet(DT_QINT8) |
    325     ToSet(DT_QUINT8) | ToSet(DT_QINT16) | ToSet(DT_QUINT16) | ToSet(DT_QINT32) |
    326     ToSet(DT_HALF);
    327 inline DataTypeSet RealAndQuantizedTypes() { return kRealAndQuantizedTypes; }
    328 
    329 #else  // defined(IS_MOBILE_PLATFORM) && !defined(__ANDROID_TYPES_FULL__)
    330 
    331 constexpr DataTypeSet kRealNumberTypes = ToSet(DT_FLOAT) | ToSet(DT_INT32);
    332 inline DataTypeSet RealNumberTypes() { return kRealNumberTypes; }
    333 
    334 constexpr DataTypeSet kNumberTypes = ToSet(DT_FLOAT) | ToSet(DT_INT32) |
    335                                      ToSet(DT_QINT8) | ToSet(DT_QUINT8) |
    336                                      ToSet(DT_QINT32);
    337 inline DataTypeSet NumberTypes() { return kNumberTypes; }
    338 
    339 constexpr DataTypeSet kQuantizedTypes = ToSet(DT_QINT8) | ToSet(DT_QUINT8) |
    340                                         ToSet(DT_QINT16) | ToSet(DT_QUINT16) |
    341                                         ToSet(DT_QINT32);
    342 inline DataTypeSet QuantizedTypes() { return kQuantizedTypes; }
    343 
    344 constexpr DataTypeSet kRealAndQuantizedTypes =
    345     ToSet(DT_FLOAT) | ToSet(DT_INT32) | ToSet(DT_QINT8) | ToSet(DT_QUINT8) |
    346     ToSet(DT_QINT16) | ToSet(DT_QUINT16) | ToSet(DT_QINT32);
    347 inline DataTypeSet RealAndQuantizedTypes() { return kRealAndQuantizedTypes; }
    348 
    349 #endif  // defined(IS_MOBILE_PLATFORM)
    350 
    351 // Validates type T for whether it is a supported DataType.
    352 template <class T>
    353 struct IsValidDataType;
    354 
    355 // DataTypeToEnum<T>::v() and DataTypeToEnum<T>::value are the DataType
    356 // constants for T, e.g. DataTypeToEnum<float>::v() is DT_FLOAT.
    357 template <class T>
    358 struct DataTypeToEnum {
    359   static_assert(IsValidDataType<T>::value, "Specified Data Type not supported");
    360 };  // Specializations below
    361 
    362 // EnumToDataType<VALUE>::Type is the type for DataType constant VALUE, e.g.
    363 // EnumToDataType<DT_FLOAT>::Type is float.
    364 template <DataType VALUE>
    365 struct EnumToDataType {};  // Specializations below
    366 
    367 // Template specialization for both DataTypeToEnum and EnumToDataType.
    368 #define MATCH_TYPE_AND_ENUM(TYPE, ENUM)                 \
    369   template <>                                           \
    370   struct DataTypeToEnum<TYPE> {                         \
    371     static DataType v() { return ENUM; }                \
    372     static DataType ref() { return MakeRefType(ENUM); } \
    373     static constexpr DataType value = ENUM;             \
    374   };                                                    \
    375   template <>                                           \
    376   struct IsValidDataType<TYPE> {                        \
    377     static constexpr bool value = true;                 \
    378   };                                                    \
    379   template <>                                           \
    380   struct EnumToDataType<ENUM> {                         \
    381     typedef TYPE Type;                                  \
    382   }
    383 
    384 MATCH_TYPE_AND_ENUM(float, DT_FLOAT);
    385 MATCH_TYPE_AND_ENUM(double, DT_DOUBLE);
    386 MATCH_TYPE_AND_ENUM(int32, DT_INT32);
    387 MATCH_TYPE_AND_ENUM(uint32, DT_UINT32);
    388 MATCH_TYPE_AND_ENUM(uint16, DT_UINT16);
    389 MATCH_TYPE_AND_ENUM(uint8, DT_UINT8);
    390 MATCH_TYPE_AND_ENUM(int16, DT_INT16);
    391 MATCH_TYPE_AND_ENUM(int8, DT_INT8);
    392 MATCH_TYPE_AND_ENUM(string, DT_STRING);
    393 MATCH_TYPE_AND_ENUM(complex64, DT_COMPLEX64);
    394 MATCH_TYPE_AND_ENUM(complex128, DT_COMPLEX128);
    395 MATCH_TYPE_AND_ENUM(int64, DT_INT64);
    396 MATCH_TYPE_AND_ENUM(uint64, DT_UINT64);
    397 MATCH_TYPE_AND_ENUM(bool, DT_BOOL);
    398 MATCH_TYPE_AND_ENUM(qint8, DT_QINT8);
    399 MATCH_TYPE_AND_ENUM(quint8, DT_QUINT8);
    400 MATCH_TYPE_AND_ENUM(qint16, DT_QINT16);
    401 MATCH_TYPE_AND_ENUM(quint16, DT_QUINT16);
    402 MATCH_TYPE_AND_ENUM(qint32, DT_QINT32);
    403 MATCH_TYPE_AND_ENUM(bfloat16, DT_BFLOAT16);
    404 MATCH_TYPE_AND_ENUM(Eigen::half, DT_HALF);
    405 MATCH_TYPE_AND_ENUM(ResourceHandle, DT_RESOURCE);
    406 MATCH_TYPE_AND_ENUM(Variant, DT_VARIANT);
    407 
    408 #undef MATCH_TYPE_AND_ENUM
    409 
    410 // All types not specialized are marked invalid.
    411 template <class T>
    412 struct IsValidDataType {
    413   static constexpr bool value = false;
    414 };
    415 
    416 // Extra validity checking; not part of public API.
    417 static_assert(IsValidDataType<int64>::value, "Incorrect impl for int64");
    418 static_assert(IsValidDataType<int32>::value, "Incorrect impl for int32");
    419 
    420 // TODO(jeff): Maybe unify this with Tensor::CanUseDMA, or the underlying
    421 // is_simple<T> in tensor.cc (and possible choose a more general name?)
    422 constexpr DataTypeSet kDataTypesCanUseMemcpy =
    423     ToSet(DT_FLOAT) | ToSet(DT_DOUBLE) | ToSet(DT_INT32) | ToSet(DT_UINT32) |
    424     ToSet(DT_UINT8) | ToSet(DT_UINT16) | ToSet(DT_INT16) | ToSet(DT_INT8) |
    425     ToSet(DT_COMPLEX64) | ToSet(DT_COMPLEX128) | ToSet(DT_INT64) |
    426     ToSet(DT_UINT64) | ToSet(DT_BOOL) | ToSet(DT_QINT8) | ToSet(DT_QUINT8) |
    427     ToSet(DT_QINT16) | ToSet(DT_QUINT16) | ToSet(DT_QINT32) |
    428     ToSet(DT_BFLOAT16) | ToSet(DT_HALF);
    429 inline bool DataTypeCanUseMemcpy(DataType dt) {
    430   return kDataTypesCanUseMemcpy.Contains(dt);
    431 }
    432 
    433 // Returns true iff 'dt' is a real, non-quantized floating point type.
    434 constexpr DataTypeSet kDataTypeIsFloating =
    435     ToSet(DT_HALF) | ToSet(DT_BFLOAT16) | ToSet(DT_FLOAT) | ToSet(DT_DOUBLE);
    436 inline bool DataTypeIsFloating(DataType dt) {
    437   return kDataTypeIsFloating.Contains(dt);
    438 }
    439 
    440 // Returns true iff 'dt' is a complex type.
    441 constexpr DataTypeSet kDataTypeIsComplex =
    442     ToSet(DT_COMPLEX64) | ToSet(DT_COMPLEX128);
    443 inline bool DataTypeIsComplex(DataType dt) {
    444   return kDataTypeIsComplex.Contains(dt);
    445 }
    446 
    447 inline bool DataTypeIsQuantized(DataType dt) {
    448   return kQuantizedTypes.Contains(dt);
    449 }
    450 
    451 // Is the dtype nonquantized integral?
    452 constexpr DataTypeSet kDataTypeIsInteger =
    453     ToSet(DT_INT8) | ToSet(DT_UINT8) | ToSet(DT_INT16) | ToSet(DT_UINT16) |
    454     ToSet(DT_INT32) | ToSet(DT_UINT32) | ToSet(DT_INT64) | ToSet(DT_UINT64);
    455 inline bool DataTypeIsInteger(DataType dt) {
    456   return kDataTypeIsInteger.Contains(dt);
    457 }
    458 
    459 // Is the dtype a signed integral type?
    460 constexpr DataTypeSet kDataTypeIsSigned =
    461     ToSet(DT_INT8) | ToSet(DT_INT16) | ToSet(DT_INT32) | ToSet(DT_INT64);
    462 inline bool DataTypeIsSigned(DataType dt) {
    463   return kDataTypeIsSigned.Contains(dt);
    464 }
    465 
    466 // Is the dtype an unsigned integral type?
    467 constexpr DataTypeSet kDataTypeIsUnsigned =
    468     ToSet(DT_UINT8) | ToSet(DT_UINT16) | ToSet(DT_UINT32) | ToSet(DT_UINT64);
    469 inline bool DataTypeIsUnsigned(DataType dt) {
    470   return kDataTypeIsUnsigned.Contains(dt);
    471 }
    472 
    473 // Returns a 0 on failure
    474 int DataTypeSize(DataType dt);
    475 
    476 // Returns HOST_MEMORY if `dtype` is always on host or is a DT_INT32,
    477 // DEVICE_MEMORY otherwise.
    478 MemoryType MTypeFromDType(const DataType dtype);
    479 
    480 // Types that always sit on host: DT_STRING, DT_STRING_REF, DT_RESOURCE.
    481 // For DT_RESOURCE, the handle always sits on host (even if the underlying
    482 // object has device-allocated resources).
    483 bool DataTypeAlwaysOnHost(DataType dt);
    484 
    485 }  // namespace tensorflow
    486 
    487 #endif  // TENSORFLOW_CORE_FRAMEWORK_TYPES_H_
    488