improving the solution

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "pregel-rs"
-version = "0.0.11"
+version = "0.0.12"
 authors = [ "Ángel Iglesias Préstamo <[email protected]>" ]
 description = "A Graph library written in Rust for implementing your own algorithms in a Pregel fashion"
 documentation = "https://docs.rs/crate/pregel-rs/latest"

README.md

@@ -6,73 +6,73 @@
 [![documentation](https://img.shields.io/docsrs/pregel-rs/latest)](https://docs.rs/pregel-rs/latest/pregel_rs/)
 
 `pregel-rs` is a Graph processing library written in Rust that features
-a Pregel-based Framework for implementing your own algorithms in a 
-message-passing fashion. It is designed to be efficient and scalable, 
+a Pregel-based Framework for implementing your own algorithms in a
+message-passing fashion. It is designed to be efficient and scalable,
 making it suitable for processing large-scale graphs.
 
 ## Features
 
 - _Pregel-based framework_: `pregel-rs` is a powerful graph processing model
-that allows users to implement graph algorithms in a message-passing fashion,
-where computation is performed on vertices and messages are passed along edges.
-`pregel-rs` provides a framework that makes it easy to implement graph 
-algorithms using this model.
+  that allows users to implement graph algorithms in a message-passing fashion,
+  where computation is performed on vertices and messages are passed along edges.
+  `pregel-rs` provides a framework that makes it easy to implement graph
+  algorithms using this model.
 
-- _Rust-based implementation_: `pregel-rs` is implemented in Rust, a systems 
-programming language known for its safety, concurrency, and performance.
-Rust's strong type system and memory safety features help ensure that `pregel-rs`
-is robust and reliable.
+- _Rust-based implementation_: `pregel-rs` is implemented in Rust, a systems
+  programming language known for its safety, concurrency, and performance.
+  Rust's strong type system and memory safety features help ensure that `pregel-rs`
+  is robust and reliable.
 
 - _Efficient and scalable_: `pregel-rs` designed to be efficient and scalable,
-making it suitable for processing large-scale graphs. It uses parallelism and
-optimization techniques to minimize computation and communication overhead,
-allowing it to handle graphs with millions or even billions of vertices and edges.
-For us to achieve this, we have built it on top of [polars](https://github.com/pola-rs/polars)
-a blazingly fast DataFrames library implemented in Rust using Apache Arrow
-Columnar Format as the memory model.
-
-- _Graph abstraction_: `pregel-rs` provides a graph abstraction that makes 
-it easy to represent and manipulate graphs in Rust. It supports both directed and
-undirected graphs, and provides methods for adding, removing, and querying vertices
-and edges.
+  making it suitable for processing large-scale graphs. It uses parallelism and
+  optimization techniques to minimize computation and communication overhead,
+  allowing it to handle graphs with millions or even billions of vertices and edges.
+  For us to achieve this, we have built it on top of [polars](https://github.com/pola-rs/polars)
+  a blazingly fast DataFrames library implemented in Rust using Apache Arrow
+  Columnar Format as the memory model.
+
+- _Graph abstraction_: `pregel-rs` provides a graph abstraction that makes
+  it easy to represent and manipulate graphs in Rust. It supports both directed and
+  undirected graphs, and provides methods for adding, removing, and querying vertices
+  and edges.
 
 - _Customizable computation_: `pregel-rs` allows users to implement their own
-computation logic by defining vertex computation functions. This gives users the 
-flexibility to implement their own graph algorithms and customize the behavior
-of `pregel-rs` to suit their specific needs.
+  computation logic by defining vertex computation functions. This gives users the
+  flexibility to implement their own graph algorithms and customize the behavior
+  of `pregel-rs` to suit their specific needs.
 
 ## Getting started
 
 To get started with `pregel-rs`, you can follow these steps:
 
 1. _Install Rust_: `pregel-rs` requires Rust to be installed on your system.
-You can install Rust by following the instructions on the official Rust website:
-https://www.rust-lang.org/tools/install
+   You can install Rust by following the instructions on the official Rust website:
+   https://www.rust-lang.org/tools/install
 
 2. _Create a new Rust project_: Once Rust is installed, you can create a new Rust
-project using the Cargo package manager, which is included with Rust. You can
-create a new project by running the following command in your terminal:
+   project using the Cargo package manager, which is included with Rust. You can
+   create a new project by running the following command in your terminal:
 
 ```sh
 cargo new my_pregel_project
 ```
 
-3. _Add `pregel-rs` as a dependency_: Next, you need to add `pregel-rs` as a 
-dependency in your `Cargo.toml` file, which is located in the root directory
-of your project. You can add the following line to your `Cargo.toml` file:
+3. _Add `pregel-rs` as a dependency_: Next, you need to add `pregel-rs` as a
+   dependency in your `Cargo.toml` file, which is located in the root directory
+   of your project. You can add the following line to your `Cargo.toml` file:
 
 ```toml
 [dependencies]
-pregel-rs = "0.0.11"
+pregel-rs = "0.0.12"
 ```
 
 4. _Implement your graph algorithm_: Now you can start implementing your graph
-algorithm using the `pregel-rs` framework. You can define your vertex computation
-functions and use the graph abstraction provided by `pregel-rs` to manipulate the graph.
+   algorithm using the `pregel-rs` framework. You can define your vertex computation
+   functions and use the graph abstraction provided by `pregel-rs` to manipulate the graph.
 
 5. _Build and run your project_: Once you have implemented your graph algorithm, you
-can build and run your project using the Cargo package manager. You can build your
-project by running the following command in your terminal:
+   can build and run your project using the Cargo package manager. You can build your
+   project by running the following command in your terminal:
 
 ```sh
 cargo build
@@ -87,14 +87,14 @@ cargo run
 ## Acknowledgments
 
 Read [Pregel: A System for Large-Scale Graph Processing](https://15799.courses.cs.cmu.edu/fall2013/static/papers/p135-malewicz.pdf)
-for a reference on how to implement your own Graph processing algorithms in a Pregel fashion. If you want to take some 
+for a reference on how to implement your own Graph processing algorithms in a Pregel fashion. If you want to take some
 inspiration from some curated-sources, just explore the [/examples](https://github.com/angelip2303/graph-rs/tree/main/examples)
 folder of this repository.
 
 ## Related projects
 
-1. [GraphX](https://github.com/apache/spark/tree/master/graphx) is a library enabling Graph processing in the context of 
-Apache Spark.
+1. [GraphX](https://github.com/apache/spark/tree/master/graphx) is a library enabling Graph processing in the context of
+   Apache Spark.
 2. [GraphFrames](https://github.com/graphframes/graphframes) is the DataFrame-based equivalent to GraphX.
 
 ## License
@@ -108,11 +108,11 @@ the Free Software Foundation, either version 3 of the License, or
 
 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
-MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 GNU General Public License for more details.
 
 You should have received a copy of the GNU General Public License
-along with this program.  If not, see <https://www.gnu.org/licenses/>.
+along with this program. If not, see <https://www.gnu.org/licenses/>.
 
 **By contributing to this project, you agree to release your
 contributions under the same license.**

examples/pagerank.rs

@@ -26,6 +26,10 @@ fn main() -> Result<(), Box<dyn Error>> {
         .max_iterations(4)
         .with_vertex_column(Custom("rank"))
         .initial_message(lit(1.0 / num_vertices))
+        .send_messages(
+            MessageReceiver::Subject,
+            Column::subject(Column::Custom("rank")) / Column::subject(Column::Custom("out_degree")),
+        )
         .send_messages(
             MessageReceiver::Object,
             Column::subject(Custom("rank")) / Column::subject(Custom("out_degree")),

src/pregel.rs

@@ -233,17 +233,6 @@ impl<'a> SendMessage<'a> {
 /// each iteration of the algorithm. The vertex program can take as input the current
 /// state of the vertex, the messages received from its neighbors or and any other
 /// relevant information.
-///
-/// * `replace_nulls`: `replace_nulls` is an expression that defines how null values
-/// in the vertex DataFrame should be replaced. This is useful when the vertex
-/// DataFrame contains null values that need to be replaced during the execution of
-/// the Pregel algorithm. As an example, when not all vertices are connected to an
-/// edge, the edge DataFrame will contain null values in the `dst` column. These
-/// null values need to be replaced.
-///
-/// * `parquet_path` is a property of the `PregelBuilder` struct that represents
-/// the path to the Parquet file where the results of the Pregel computation
-/// will be stored.
 pub struct Pregel<'a> {
     /// The `graph` property is a `GraphFrame` struct that represents the
     /// graph data structure used in the Pregel algorithm. It contains information about
@@ -277,13 +266,6 @@ pub struct Pregel<'a> {
     /// current state of the vertex, the messages received from its neighbors or
     /// and any other relevant information.
     v_prog: FnBox<'a>,
-    /// `replace_nulls` is an expression that defines how null values in the vertex
-    /// DataFrame should be replaced. This is useful when the vertex DataFrame
-    /// contains null values that need to be replaced during the execution of the
-    /// Pregel algorithm. As an example, when not all vertices are connected to an
-    /// edge, the edge DataFrame will contain null values in the `dst` column. These
-    /// null values need to be replaced.
-    replace_nulls: Expr,
 }
 
 /// The `PregelBuilder` struct represents a builder for configuring the Pregel
@@ -325,13 +307,6 @@ pub struct Pregel<'a> {
 /// each iteration of the algorithm. The vertex program can take as input the current
 /// state of the vertex, the messages received from its neighbors or and any other
 /// relevant information.
-///
-/// /// * `replace_nulls`: `replace_nulls` is an expression that defines how null values
-/// in the vertex DataFrame should be replaced. This is useful when the vertex
-/// DataFrame contains null values that need to be replaced during the execution of
-/// the Pregel algorithm. As an example, when not all vertices are connected to an
-/// edge, the edge DataFrame will contain null values in the `dst` column. These
-/// null values need to be replaced.
 pub struct PregelBuilder<'a> {
     /// The `graph` property is a `GraphFrame` struct that represents the
     /// graph data structure used in the Pregel algorithm. It contains information about
@@ -365,13 +340,6 @@ pub struct PregelBuilder<'a> {
     /// current state of the vertex, the messages received from its neighbors or
     /// and any other relevant information.
     v_prog: FnBox<'a>,
-    /// `replace_nulls` is an expression that defines how null values in the vertex
-    /// DataFrame should be replaced. This is useful when the vertex DataFrame
-    /// contains null values that need to be replaced during the execution of the
-    /// Pregel algorithm. As an example, when not all vertices are connected to an
-    /// edge, the edge DataFrame will contain null values in the `dst` column. These
-    /// null values need to be replaced.
-    replace_nulls: Expr,
 }
 
 /// This code is defining an enumeration type `MessageReceiver` in Rust with
@@ -419,7 +387,6 @@ impl<'a> PregelBuilder<'a> {
             send_messages: Default::default(),
             aggregate_messages: Box::new(Default::default),
             v_prog: Box::new(Default::default),
-            replace_nulls: Default::default(),
         }
     }
 
@@ -665,27 +632,6 @@ impl<'a> PregelBuilder<'a> {
         self
     }
 
-    /// This function sets the value of a field called "replace_nulls" in a struct to a
-    /// given expression and returns the modified struct.
-    ///
-    /// Arguments:
-    ///
-    /// * `replace_nulls`: `replace_nulls` is a parameter of type `Expr` that is used in
-    /// a method of a struct. The method takes ownership of the struct (`self`) and the
-    /// `replace_nulls` parameter, and sets the `replace_nulls` field of the struct to the
-    /// value of the `replace_nulls` parameter.
-    ///
-    /// Returns:
-    ///
-    /// The `replace_nulls` method returns `Self`, which refers to the same struct
-    /// instance that the method was called on. This allows for method chaining, where
-    /// multiple methods can be called on the same struct instance in a single
-    /// expression.
-    pub fn replace_nulls(mut self, replace_nulls: Expr) -> Self {
-        self.replace_nulls = replace_nulls;
-        self
-    }
-
     /// The function returns a Pregel struct with the specified properties. This is,
     /// Pregel structs are to be created using the `Builder Pattern`, a creational
     /// design pattern that provides a way to construct complex structs in a
@@ -743,7 +689,6 @@ impl<'a> PregelBuilder<'a> {
             send_messages: self.send_messages,
             aggregate_messages: self.aggregate_messages,
             v_prog: self.v_prog,
-            replace_nulls: self.replace_nulls,
         }
     }
 }
@@ -898,7 +843,6 @@ impl<'a> Pregel<'a> {
                     col(Column::VertexId.as_ref()), // id column of the current_vertices DataFrame
                     Column::msg(Some(Column::VertexId)), // msg.id column of the message_df DataFrame
                 )
-                .with_column(Column::msg(None).fill_null(self.replace_nulls.to_owned()))
                 .select(&[
                     col(Column::VertexId.as_ref()),
                     v_prog().alias(self.vertex_column.as_ref()),
@@ -971,7 +915,11 @@ mod tests {
             .max_iterations(iterations)
             .with_vertex_column(Column::Custom("rank"))
             .initial_message(lit(1.0 / num_vertices))
-            .replace_nulls(lit(0.0))
+            .send_messages(
+                MessageReceiver::Subject,
+                Column::subject(Column::Custom("rank"))
+                    / Column::subject(Column::Custom("out_degree")),
+            )
             .send_messages(
                 MessageReceiver::Object,
                 Column::subject(Column::Custom("rank"))
@@ -1077,7 +1025,6 @@ mod tests {
             v_prog: Box::new(|| {
                 max_exprs([col(Column::Custom("max_value").as_ref()), Column::msg(None)])
             }),
-            replace_nulls: lit(0),
         })
     }