Fix gemma_cpp/examples/hello_world build.

Include Bazel build rules, too.

PiperOrigin-RevId: 652469406

examples/hello_world/BUILD

@@ -0,0 +1,22 @@
+# Hello World example frontend to gemma.cpp.
+package(
+    default_applicable_licenses = [
+        "//:license",  # Placeholder comment, do not modify
+    ],
+    default_visibility = ["//visibility:public"],
+)
+
+cc_binary(
+    name = "hello_world",
+    srcs = ["run.cc"],
+    deps = [
+        # Placeholder for internal dep, do not remove.,
+        "//:app",
+        "//:args",
+        "//:common",
+        "//:gemma_lib",
+        "//:tokenizer",
+        "@hwy//:hwy",
+        "@hwy//:thread_pool",
+    ],
+)

examples/hello_world/run.cc

@@ -15,33 +15,40 @@
 
 #include <stddef.h>
 
+#include <iostream>
 #include <random>
 #include <string>
 #include <vector>
 
-#include "third_party/gemma_cpp/gemma.h"
+// Placeholder for internal header, do not modify.
+#include "gemma/common.h"
+#include "gemma/gemma.h"
+#include "gemma/tokenizer.h"
 #include "util/app.h"  // LoaderArgs
+#include "util/args.h"
 #include "hwy/base.h"
 #include "hwy/contrib/thread_pool/thread_pool.h"
 
-std::vector<int> tokenize(const std::string& prompt_string,
-                          const gcpp::GemmaTokenizer* tokenizer) {
-  std::string formatted = "<start_of_turn>user\n" + prompt_string +
-                          "<end_of_turn>\n<start_of_turn>model\n";
-  std::vector<int> tokens;
-  HWY_ASSERT(tokenizer->Encode(formatted, &tokens));
-  tokens.insert(tokens.begin(), BOS_ID);
-  return tokens;
-}
-
 int main(int argc, char** argv) {
+  int argc_dummy = 1;
+  // Required because sentencepiece uses Google I/O which requires InitGoogle.
+  // argc_dummy = 1 avoids sentencepiece absl flags attempting to parse
+  // arguments
+  InitGoogle("usage", &argc_dummy, &argv, false);
+
   gcpp::LoaderArgs loader(argc, argv);
-  gcpp::AppArgs app(argc, argv);
+  if (gcpp::HasHelp(argc, argv)) {
+    loader.Help();
+    return 0;
+  } else if (const char* error = loader.Validate()) {
+    loader.Help();
+    HWY_ABORT("\nInvalid args: %s", error);
+  }
 
   // Instantiate model and KV Cache
-  hwy::ThreadPool pool(app.num_threads);
+  hwy::ThreadPool pool(gcpp::AppArgs::GetSupportedThreadCount());
   gcpp::Gemma model = gcpp::CreateGemma(loader, pool);
-  gcpp::KVCache kv_cache = gcpp::KVCache::Create(loader.ModelType());
+  gcpp::KVCache kv_cache = gcpp::KVCache::Create(loader.Info().model);
   size_t pos = 0;  // KV Cache position
 
   // Initialize random number generator
@@ -49,30 +56,33 @@ int main(int argc, char** argv) {
   std::random_device rd;
   gen.seed(rd());
 
-  // Tokenize instruction
-  std::vector<int> tokens =
-      tokenize("Write a greeting to the world.", model.Tokenizer());
+  // Tokenize instructions.
+  std::string prompt = "Write a greeting to the world.";
+  const std::vector<int> tokens =
+      gcpp::WrapAndTokenize(model.Tokenizer(), loader.Info(), pos, prompt);
   size_t ntokens = tokens.size();
 
   // This callback function gets invoked every time a token is generated
-  auto stream_token = [&pos, &ntokens, tokenizer = model.Tokenizer()](int token,
-                                                                      float) {
+  auto stream_token = [&pos, &ntokens, &model](int token, float) {
     ++pos;
     if (pos < ntokens) {
       // print feedback
     } else if (token != gcpp::EOS_ID) {
       std::string token_text;
-      HWY_ASSERT(tokenizer->Decode(std::vector<int>{token}, &token_text));
+      HWY_ASSERT(model.Tokenizer().Decode({token}, &token_text));
       std::cout << token_text << std::flush;
     }
     return true;
   };
 
-  GenerateGemma(model,
-                {.max_tokens = 2048,
-                 .max_generated_tokens = 1024,
-                 .temperature = 1.0,
-                 .verbosity = 0},
-                tokens, /*KV cache position = */ 0, kv_cache, pool,
-                stream_token, gen);
+  gcpp::TimingInfo timing_info;
+  gcpp::RuntimeConfig runtime_config = {
+      .max_tokens = 1536,
+      .max_generated_tokens = 1024,
+      .temperature = 1.0,
+      .verbosity = 0,
+      .gen = &gen,
+      .stream_token = stream_token,
+  };
+  model.Generate(runtime_config, tokens, 0, kv_cache, timing_info);
 }