Assume network file is in little-endian byte order

This patch fixes the byte order when reading 16- and 32-bit values from the network file on a big-endian machine.

Bytes are ordered in read_le() using unsigned arithmetic, which doesn't need tricks to determine the endianness of the machine. Unfortunately the compiler doesn't seem to be able to optimise the ordering operation, but reading in the weights is not a time-critical operation and the extra time it takes should not be noticeable.

Big endian systems are still untested with NNUE.

fixes #3007

closes https://github.com/official-stockfish/Stockfish/pull/3009

No functional change.

diff --git a/src/nnue/evaluate_nnue.cpp b/src/nnue/evaluate_nnue.cpp
index a6ece8e2427b1fe731e68667dbac1e99720d4e2c..3aa85943944c41b25ed33a918d547dddec6eaad8 100644 (file)
--- a/src/nnue/evaluate_nnue.cpp
+++ b/src/nnue/evaluate_nnue.cpp
@@ -77,7 +77,7 @@ namespace Eval::NNUE {
   bool ReadParameters(std::istream& stream, const AlignedPtr<T>& pointer) {
 
     std::uint32_t header;
-    stream.read(reinterpret_cast<char*>(&header), sizeof(header));
+    header = read_le<std::uint32_t>(stream);
     if (!stream || header != T::GetHashValue()) return false;
     return pointer->ReadParameters(stream);
   }
@@ -96,9 +96,9 @@ namespace Eval::NNUE {
     std::uint32_t* hash_value, std::string* architecture) {
 
     std::uint32_t version, size;
-    stream.read(reinterpret_cast<char*>(&version), sizeof(version));
-    stream.read(reinterpret_cast<char*>(hash_value), sizeof(*hash_value));
-    stream.read(reinterpret_cast<char*>(&size), sizeof(size));
+    version = read_le<std::uint32_t>(stream);
+    *hash_value = read_le<std::uint32_t>(stream);
+    size = read_le<std::uint32_t>(stream);
     if (!stream || version != kVersion) return false;
     architecture->resize(size);
     stream.read(&(*architecture)[0], size);

diff --git a/src/nnue/layers/affine_transform.h b/src/nnue/layers/affine_transform.h
index 322e32402500029033caa5ddbb7123965adc45d7..bac258e8acffe3a277c7030a76c86d14a08ee7b8 100644 (file)
--- a/src/nnue/layers/affine_transform.h
+++ b/src/nnue/layers/affine_transform.h
@@ -62,11 +62,10 @@ namespace Eval::NNUE::Layers {
    // Read network parameters
     bool ReadParameters(std::istream& stream) {
       if (!previous_layer_.ReadParameters(stream)) return false;
-      stream.read(reinterpret_cast<char*>(biases_),
-                  kOutputDimensions * sizeof(BiasType));
-      stream.read(reinterpret_cast<char*>(weights_),
-                  kOutputDimensions * kPaddedInputDimensions *
-                  sizeof(WeightType));
+      for (std::size_t i = 0; i < kOutputDimensions; ++i)
+        biases_[i] = read_le<BiasType>(stream);
+      for (std::size_t i = 0; i < kOutputDimensions * kPaddedInputDimensions; ++i)
+        weights_[i] = read_le<WeightType>(stream);
       return !stream.fail();
     }
 

diff --git a/src/nnue/nnue_common.h b/src/nnue/nnue_common.h
index eab7d258816cfe4dc2489a43d5c27b098b676d76..61f18aeec848be9b25edde2b68733e97c8cf254b 100644 (file)
--- a/src/nnue/nnue_common.h
+++ b/src/nnue/nnue_common.h
@@ -21,6 +21,9 @@
 #ifndef NNUE_COMMON_H_INCLUDED
 #define NNUE_COMMON_H_INCLUDED
 
+#include <cstring>
+#include <iostream>
+
 #if defined(USE_AVX2)
 #include <immintrin.h>
 
@@ -101,6 +104,22 @@ namespace Eval::NNUE {
     return (n + base - 1) / base * base;
   }
 
+  // Read a signed or unsigned integer from  a stream in little-endian order
+  template <typename IntType>
+  inline IntType read_le(std::istream& stream) {
+    // Read the relevant bytes from the stream in little-endian order
+    std::uint8_t u[sizeof(IntType)];
+    stream.read(reinterpret_cast<char*>(u), sizeof(IntType));
+    // Use unsigned arithmetic to convert to machine order
+    typename std::make_unsigned<IntType>::type v = 0;
+    for (std::size_t i = 0; i < sizeof(IntType); ++i)
+      v = (v << 8) | u[sizeof(IntType) - i - 1];
+    // Copy the machine-ordered bytes into a potentially signed value
+    IntType w;
+    std::memcpy(&w, &v, sizeof(IntType));
+    return w;
+  }
+
 }  // namespace Eval::NNUE
 
 #endif // #ifndef NNUE_COMMON_H_INCLUDED

diff --git a/src/nnue/nnue_feature_transformer.h b/src/nnue/nnue_feature_transformer.h
index 40f2603d9d5c8a8fe212a1a40b465876f822cf6e..4db9be9f0f0dea7c3403409bc2992e8402eb1519 100644 (file)
--- a/src/nnue/nnue_feature_transformer.h
+++ b/src/nnue/nnue_feature_transformer.h
@@ -55,10 +55,10 @@ namespace Eval::NNUE {
 
     // Read network parameters
     bool ReadParameters(std::istream& stream) {
-      stream.read(reinterpret_cast<char*>(biases_),
-                  kHalfDimensions * sizeof(BiasType));
-      stream.read(reinterpret_cast<char*>(weights_),
-                  kHalfDimensions * kInputDimensions * sizeof(WeightType));
+      for (std::size_t i = 0; i < kHalfDimensions; ++i)
+        biases_[i] = read_le<BiasType>(stream);
+      for (std::size_t i = 0; i < kHalfDimensions * kInputDimensions; ++i)
+        weights_[i] = read_le<WeightType>(stream);
       return !stream.fail();
     }