Make torch.Generator serializable

Generator.c

@@ -1,9 +1,5 @@
 #include <general.h>
 
-static const struct luaL_Reg torch_Generator_table_ [] = {
-  {NULL, NULL}
-};
-
 int torch_Generator_new(lua_State *L)
 {
   THGenerator *gen = THGenerator_new();
@@ -18,6 +14,31 @@ int torch_Generator_free(lua_State *L)
   return 0;
 }
 
+static int torch_Generator_write(lua_State *L)
+{
+  THGenerator *gen = luaT_checkudata(L, 1, torch_Generator);
+  THFile *file = luaT_checkudata(L, 2, "torch.File");
+
+  THFile_writeByteRaw(file, (unsigned char *)gen, sizeof(THGenerator));
+  return 0;
+}
+
+static int torch_Generator_read(lua_State *L)
+{
+  THGenerator *gen = luaT_checkudata(L, 1, torch_Generator);
+  THFile *file = luaT_checkudata(L, 2, "torch.File");
+
+  THFile_readByteRaw(file, (unsigned char *)gen, sizeof(THGenerator));
+  return 0;
+}
+
+
+static const struct luaL_Reg torch_Generator_table_ [] = {
+  {"write", torch_Generator_write},
+  {"read", torch_Generator_read},
+  {NULL, NULL}
+};
+
 #define torch_Generator_factory torch_Generator_new
 
 void torch_Generator_init(lua_State *L)

test/test.lua

@@ -2483,6 +2483,20 @@ function torchtest.RNGStateAliasing()
     mytester:assertTensorEq(target_value, forked_value, 1e-16, "RNG has not forked correctly.")
 end
 
+function torchtest.serializeGenerator()
+   local generator = torch.Generator()
+   torch.manualSeed(generator, 123)
+   local differentGenerator = torch.Generator()
+   torch.manualSeed(differentGenerator, 124)
+   local serializedGenerator = torch.serialize(generator)
+   local deserializedGenerator = torch.deserialize(serializedGenerator)
+   local generated = torch.random(generator)
+   local differentGenerated = torch.random(differentGenerator)
+   local deserializedGenerated = torch.random(deserializedGenerator)
+   mytester:asserteq(generated, deserializedGenerated, 'torch.Generator changed internal state after being serialized')
+   mytester:assertne(generated, differentGenerated, 'Generators with different random seed should not produce the same output')
+end
+
 function torchtest.testBoxMullerState()
     torch.manualSeed(123)
     local odd_number = 101