add README, license to hello_world

examples/hello_world/CMakeLists.txt

@@ -24,6 +24,7 @@ FetchContent_Declare(sentencepiece GIT_REPOSITORY https://github.com/google/sent
 FetchContent_MakeAvailable(sentencepiece)
 
 
+
 # Allow for both local and remote building)
 option(BUILD_MODE "'local' or 'remote' git fetch for builds")
 if (NOT BUILD_MODE)

examples/hello_world/README.md

@@ -0,0 +1,41 @@
+# Hello World Example
+
+This is a minimal/template project for using `gemma.cpp` as a library. Instead of an interactive interface, it sets up the model state and generates text for a single hard coded prompt.
+
+Build steps are similar to the main `gemma` executable. From inside the top-level directory. For now only `cmake`/`make` is available for builds (PRs welcome for other build options).
+
+First use `cmake` to configure the project, assuming you are in the `hello_world` example directory (`gemma.cpp/examples/hello_world`):
+
+```sh
+cmake -B build
+```
+
+This sets up a build configuration in `gemma.cpp/examples/hello_world/build`. Note that this fetches `libgemma` from a git commit hash on github. Alternatively if you want to build using the local version of `gemma.cpp` use:
+
+
+```sh
+cmake -B build -DBUILD_MODE=local
+```
+
+Make sure you delete the contents of the build directory before changing configurations.
+
+Then use `make` to build the project:
+
+```sh
+cd build
+make hello_world
+```
+
+As with the top-level `gemma.cpp` project you can use the `make` commands `-j` flag to use parallel threads for faster builds.
+
+From inside the `gemma.cpp/examples/hello_world/build` directory, there should be a `hello_world` executable. You can run it with the same 3 model arguments as gemma.cpp specifying the tokenizer, compressed weights file, and model type, for example:
+
+```sh
+./hello_world --tokenizer tokenizer.spm --compressed_weights 2b-it-sfp.sbs --model 2b-it
+```
+
+Should  print a greeting to the terminal:
+
+```
+"Hello, world! It's a pleasure to greet you all. May your day be filled with joy, peace, and all the things that make your heart soar.
+```

examples/hello_world/run.cc

@@ -1,3 +1,18 @@
+// Copyright 2024 Google LLC
+// SPDX-License-Identifier: Apache-2.0
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 #include <iostream>
 
 // copybara:import_next_line:gemma_cpp
@@ -43,7 +58,7 @@ int main(int argc, char** argv) {
       tokenize("Write a greeting to the world.", model.Tokenizer());
   size_t ntokens = tokens.size();
 
-  // Callback
+  // This callback function gets invoked everytime a token is generated
   auto stream_token = [&pos, &gen, &ntokens, tokenizer = model.Tokenizer()](
                           int token, float) {
     ++pos;