Type-Level Location Set

Cargo.toml

@@ -3,7 +3,7 @@
 members = ["chorus_lib", "chorus_derive"]
 
 [workspace.package]
-version = "0.1.3"
+version = "0.2.0"
 edition = "2021"
 authors = ["Shun Kashiwa <[email protected]>"]
 homepage = "https://lsd-ucsc.github.io/ChoRus/"

chorus_book/src/guide-choreography.md

@@ -9,7 +9,8 @@ struct HelloWorldChoreography;
 
 // 2. Implement the `Choreography` trait
 impl Choreography for HelloWorldChoreography {
-    fn run(self, op: &impl ChoreoOp) {
+    type L = LocationSet!(Alice);
+    fn run(self, op: &impl ChoreoOp<Self::L>) {
         // 3. Use the `op` parameter to access operators
         op.locally(Alice, |_| {
             println!("Hello, World!");
@@ -20,6 +21,8 @@ impl Choreography for HelloWorldChoreography {
 
 `Choreography` must implement the `run` method which defines the behavior of the system. The `run` method takes a reference to an object that implements the `ChoreoOp` trait. The `ChoreoOp` trait provides choreographic operators such as `locally` and `comm`.
 
+Also, each `Choreography` has an associated `LocationSet` type, `L`; this is the `LocationSet` that the `Choreography` can operate on.
+
 ## Choreographic Operators
 
 Inside the `run` method, you can use the `op` parameter to access choreographic operators.
@@ -33,7 +36,8 @@ The `locally` operator is used to perform a computation at a single location. It
 #
 # struct HelloWorldChoreography;
 # impl Choreography for HelloWorldChoreography {
-#     fn run(self, op: &impl ChoreoOp) {
+#     type L = LocationSet!(Alice);
+#     fn run(self, op: &impl ChoreoOp<Self::L>) {
 op.locally(Alice, |_| {
     println!("Hello, World!");
 });
@@ -48,7 +52,8 @@ The closure can return a value to create a located value. Located values are val
 #
 # struct HelloWorldChoreography;
 # impl Choreography for HelloWorldChoreography {
-#     fn run(self, op: &impl ChoreoOp) {
+#     type L = LocationSet!(Alice);
+#     fn run(self, op: &impl ChoreoOp<Self::L>) {
 // This value is only available at Alice
 let num_at_alice: Located<i32, Alice> = op.locally(Alice, |_| {
     42
@@ -64,7 +69,8 @@ The computation closure takes `Unwrapper`. Using the `Unwrapper`, you can get a
 #
 # struct HelloWorldChoreography;
 # impl Choreography for HelloWorldChoreography {
-#     fn run(self, op: &impl ChoreoOp) {
+#     type L = LocationSet!(Alice);
+#     fn run(self, op: &impl ChoreoOp<Self::L>) {
 let num_at_alice: Located<i32, Alice> = op.locally(Alice, |_| {
     42
 });
@@ -79,12 +85,13 @@ op.locally(Alice, |un| {
 
 Note that you can unwrap a located value only at the location where the located value is available. If you try to unwrap a located value at a different location, the program will fail to compile.
 
-```rust,compile_fail
+```rust, compile_fail
 {{#include ./header.txt}}
 #
 # struct HelloWorldChoreography;
 # impl Choreography for HelloWorldChoreography {
-#     fn run(self, op: &impl ChoreoOp) {
+#     type L = LocationSet!(Alice, Bob);
+#     fn run(self, op: &impl ChoreoOp<Self::L>) {
 // This code will fail to compile
 let num_at_alice = op.locally(Alice, |_| { 42 });
 op.locally(Bob, |un| {
@@ -106,7 +113,8 @@ The `comm` operator is used to perform a communication between two locations. It
 #
 # struct HelloWorldChoreography;
 # impl Choreography for HelloWorldChoreography {
-#     fn run(self, op: &impl ChoreoOp) {
+#     type L = LocationSet!(Alice, Bob);
+#     fn run(self, op: &impl ChoreoOp<Self::L>) {
 // This value is only available at Alice
 let num_at_alice: Located<i32, Alice> = op.locally(Alice, |_| {
     42
@@ -131,7 +139,8 @@ The `broadcast` operator is used to perform a broadcast from a single location t
 #
 # struct HelloWorldChoreography;
 # impl Choreography for HelloWorldChoreography {
-#     fn run(self, op: &impl ChoreoOp) {
+#     type L = LocationSet!(Alice);
+#     fn run(self, op: &impl ChoreoOp<Self::L>) {
 // This value is only available at Alice
 let num_at_alice: Located<i32, Alice> = op.locally(Alice, |_| {
     42
@@ -144,10 +153,33 @@ let num: i32 = op.broadcast(Alice, num_at_alice);
 
 Because all locations receive the value, the return type of the `broadcast` operator is a normal value, not a located value. This means that the value can be used for control flow.
 
-```rust,ignore
+```rust, ignore
 if num == 42 {
     println!("The number is 42!");
 } else {
     println!("The number is not 42!");
 }
 ```
+
+### Note on invalid values for Choreography::L
+
+You'll get a compile error if you try to work with a `ChoreographyLocation` that is not a member of `L`.
+
+```rust, compile_fail
+# {{#include ./header.txt}}
+# // 1. Define a struct
+# struct HelloWorldChoreography;
+
+# // 2. Implement the `Choreography` trait
+// ...
+impl Choreography for HelloWorldChoreography {
+    type L = LocationSet!(Alice);
+    fn run(self, op: &impl ChoreoOp<Self::L>) {
+        // this will fail
+        op.locally(Bob, |_| {
+            println!("Hello, World!");
+        });
+    }
+}
+```
+

chorus_book/src/guide-colocally.md

@@ -20,7 +20,8 @@ This protocol can be implemented as follows:
 struct DemoChoreography;
 
 impl Choreography for DemoChoreography {
-    fn run(self, op: &impl ChoreoOp) {
+    type L = LocationSet!(Alice, Bob, Carol);
+    fn run(self, op: &impl ChoreoOp<Self::L>) {
         let x_at_alice = op.locally(Alice, |_| {
             get_random_number()
         });
@@ -51,7 +52,8 @@ struct BobCarolChoreography {
     x_at_bob: Located<u32, Bob>,
 };
 impl Choreography for BobCarolChoreography {
-    fn run(self, op: &impl ChoreoOp) {
+    type L = LocationSet!(Bob, Carol);
+    fn run(self, op: &impl ChoreoOp<Self::L>) {
         let is_even_at_bob: Located<bool, Bob> = op.locally(Bob, |un| {
             let x = un.unwrap(&self.x_at_bob);
             x % 2 == 0
@@ -68,7 +70,7 @@ impl Choreography for BobCarolChoreography {
 }
 ```
 
-Notice that the `BobCarolChoreography` only describes the behavior of Bob and Carol. Since Alice does not appear in this choreography, we can use the `colocally` operator in the main choreography to execute the sub-choreography only on Bob and Carol.
+Notice that `BobCarolChoreography` only describes the behavior of Bob and Carol (see its location set `L`). `colocally` is an operator to execute a choreography only at locations that is included in the location set. In this case, if we invoke `BobCarolChoreography` with `colocally` in the main choreography, it will only be executed at Bob and Carol and not at Alice.
 
 ```rust
 {{#include ./header.txt}}
@@ -79,7 +81,8 @@ Notice that the `BobCarolChoreography` only describes the behavior of Bob and Ca
 #     x_at_bob: Located<u32, Bob>,
 # };
 # impl Choreography for BobCarolChoreography {
-#     fn run(self, op: &impl ChoreoOp) {
+#     type L = LocationSet!(Bob, Carol);
+#     fn run(self, op: &impl ChoreoOp<Self::L>) {
 #         let is_even_at_bob: Located<bool, Bob> = op.locally(Bob, |un| {
 #             let x = un.unwrap(&self.x_at_bob);
 #             x % 2 == 0
@@ -96,12 +99,13 @@ Notice that the `BobCarolChoreography` only describes the behavior of Bob and Ca
 # }
 struct MainChoreography;
 impl Choreography for MainChoreography {
-    fn run(self, op: &impl ChoreoOp) {
+    type L = LocationSet!(Alice, Bob, Carol);
+    fn run(self, op: &impl ChoreoOp<Self::L>) {
         let x_at_alice = op.locally(Alice, |_| {
             get_random_number()
         });
         let x_at_bob = op.comm(Alice, Bob, &x_at_alice);
-        op.colocally(&[Bob.name(), Carol.name()], BobCarolChoreography {
+        op.colocally(BobCarolChoreography {
             x_at_bob,
         });
     }
@@ -131,7 +135,8 @@ struct BobCarolChoreography {
 };
 
 impl Choreography<BobCarolResult> for BobCarolChoreography {
-    fn run(self, op: &impl ChoreoOp) -> BobCarolResult {
+    type L = LocationSet!(Bob, Carol);
+    fn run(self, op: &impl ChoreoOp<Self::L>) -> BobCarolResult {
         let is_even_at_bob: Located<bool, Bob> = op.locally(Bob, |un| {
             let x = un.unwrap(&self.x_at_bob);
             x % 2 == 0
@@ -154,15 +159,16 @@ impl Choreography<BobCarolResult> for BobCarolChoreography {
 struct MainChoreography;
 
 impl Choreography for MainChoreography {
-    fn run(self, op: &impl ChoreoOp) {
+    type L = LocationSet!(Alice, Bob, Carol);
+    fn run(self, op: &impl ChoreoOp<Self::L>) {
         let x_at_alice = op.locally(Alice, |_| {
             get_random_number()
         });
         let x_at_bob = op.comm(Alice, Bob, &x_at_alice);
         let BobCarolResult {
             is_even_at_bob,
             is_even_at_carol,
-        } = op.colocally(&[Bob.name(), Carol.name()], BobCarolChoreography {
+        } = op.colocally(BobCarolChoreography {
             x_at_bob,
         });
         // can access is_even_at_bob and is_even_at_carol using `locally` on Bob and Carol

chorus_book/src/guide-higher-order-choreography.md

@@ -22,8 +22,9 @@ When you implement the `Choreography` trait, you have access to the `sub_choreo`
 # struct HigherOrderChoreography<C: Choreography> {
 #     sub_choreo: C,
 # };
-impl<C: Choreography> Choreography for HigherOrderChoreography<C> {
-    fn run(self, op: &impl ChoreoOp) {
+impl<C: Choreography<(), L = LocationSet!(Alice, Bob)>> Choreography for HigherOrderChoreography<C> {
+    type L = LocationSet!(Alice, Bob);
+    fn run(self, op: &impl ChoreoOp<Self::L>) {
         op.call(self.sub_choreo);
     }
 }
@@ -45,8 +46,9 @@ struct HigherOrderChoreography<C: Choreography<Located<bool, Alice>> + SubChoreo
     _marker: PhantomData<C>,
 };
 
-impl<C: Choreography<Located<bool, Alice>> + SubChoreography> Choreography for HigherOrderChoreography<C> {
-    fn run(self, op: &impl ChoreoOp) {
+impl<C: Choreography<Located<bool, Alice>, L = LocationSet!(Alice)> + SubChoreography> Choreography for HigherOrderChoreography<C> {
+    type L = LocationSet!(Alice);
+    fn run(self, op: &impl ChoreoOp<Self::L>) {
         let num_at_alice = op.locally(Alice, |_| {
             42
         });

chorus_book/src/guide-input-and-output.md

@@ -18,7 +18,8 @@ struct DemoChoreography {
 }
 
 impl Choreography for DemoChoreography {
-    fn run(self, op: &impl ChoreoOp) {
+    type L = LocationSet!();
+    fn run(self, op: &impl ChoreoOp<Self::L>) {
         println!("Input: {}", self.input);
     }
 }
@@ -32,15 +33,17 @@ You can construct an instance of the choreography with the input and pass it to
 #     input: String,
 # }
 # impl Choreography for DemoChoreography {
-#     fn run(self, op: &impl ChoreoOp) {
+#     type L = LocationSet!(Alice);
+#     fn run(self, op: &impl ChoreoOp<Self::L>) {
 #         println!("Input: {}", self.input);
 #     }
 # }
 #
 let choreo = DemoChoreography {
     input: "World".to_string(),
 };
-let projector = Projector::new(Alice, transport);
+
+let projector = Projector::new(Alice, alice_transport);
 projector.epp_and_run(choreo);
 ```
 
@@ -55,7 +58,8 @@ struct DemoChoreography {
 }
 
 impl Choreography for DemoChoreography {
-    fn run(self, op: &impl ChoreoOp) {
+    type L = LocationSet!(Alice);
+    fn run(self, op: &impl ChoreoOp<Self::L>) {
         op.locally(Alice, |un| {
             let input = un.unwrap(&self.input);
             println!("Input at Alice: {}", input);
@@ -81,14 +85,15 @@ To run the sample choreography above at Alice, we use the `local` method to cons
 # }
 #
 # impl Choreography for DemoChoreography {
-#     fn run(self, op: &impl ChoreoOp) {
+#     type L = LocationSet!(Alice);
+#     fn run(self, op: &impl ChoreoOp<Self::L>) {
 #         op.locally(Alice, |un| {
 #             let input = un.unwrap(&self.input);
 #             println!("Input at Alice: {}", input);
 #         });
 #     }
 # }
-let projector_for_alice = Projector::new(Alice, transport);
+let projector_for_alice = Projector::new(Alice, alice_transport);
 // Because the target of the projector is Alice, the located value is available at Alice.
 let string_at_alice: Located<String, Alice> = projector_for_alice.local("Hello, World!".to_string());
 // Instantiate the choreography with the located value
@@ -107,14 +112,15 @@ For Bob, we use the `remote` method to construct the located value.
 # }
 #
 # impl Choreography for DemoChoreography {
-#     fn run(self, op: &impl ChoreoOp) {
+#     type L = LocationSet!(Alice, Bob);
+#     fn run(self, op: &impl ChoreoOp<Self::L>) {
 #         op.locally(Alice, |un| {
 #             let input = un.unwrap(&self.input);
 #             println!("Input at Alice: {}", input);
 #         });
 #     }
 # }
-let projector_for_bob = Projector::new(Bob, transport);
+let projector_for_bob = Projector::new(Bob, bob_transport);
 // Construct a remote located value at Alice. The actual value is not required.
 let string_at_alice = projector_for_bob.remote(Alice);
 // Instantiate the choreography with the located value
@@ -135,7 +141,8 @@ To do so, we specify the output type to the `Choreography` trait and return the
 struct DemoChoreography;
 
 impl Choreography<String> for DemoChoreography {
-    fn run(self, op: &impl ChoreoOp) -> String {
+    type L = LocationSet!();
+    fn run(self, op: &impl ChoreoOp<Self::L>) -> String {
         "Hello, World!".to_string()
     }
 }
@@ -148,12 +155,13 @@ impl Choreography<String> for DemoChoreography {
 # struct DemoChoreography;
 #
 # impl Choreography<String> for DemoChoreography {
-#     fn run(self, op: &impl ChoreoOp) -> String {
+#     type L = LocationSet!(Alice);
+#     fn run(self, op: &impl ChoreoOp<Self::L>) -> String {
 #         "Hello, World!".to_string()
 #     }
 # }
 let choreo = DemoChoreography;
-let projector = Projector::new(Alice, transport);
+let projector = Projector::new(Alice, alice_transport);
 let output = projector.epp_and_run(choreo);
 assert_eq!(output, "Hello, World!".to_string());
 ```
@@ -167,14 +175,15 @@ You can use the `Located<V, L1>` as a return type of the `run` method to return
 struct DemoChoreography;
 
 impl Choreography<Located<String, Alice>> for DemoChoreography {
-    fn run(self, op: &impl ChoreoOp) -> Located<String, Alice> {
+    type L = LocationSet!(Alice);
+    fn run(self, op: &impl ChoreoOp<Self::L>) -> Located<String, Alice> {
         op.locally(Alice, |_| {
             "Hello, World!".to_string()
         })
     }
 }
 
-let projector = Projector::new(Alice, transport);
+let projector = Projector::new(Alice, alice_transport);
 let output = projector.epp_and_run(DemoChoreography);
 let string_at_alice = projector.unwrap(output);
 assert_eq!(string_at_alice, "Hello, World!".to_string());

chorus_book/src/guide-location-polymorphism.md

@@ -11,7 +11,8 @@ struct LocationPolymorphicChoreography<L1: ChoreographyLocation> {
 }
 
 impl<L1: ChoreographyLocation> Choreography for LocationPolymorphicChoreography<L1> {
-    fn run(self, op: &impl ChoreoOp) {
+    type L = LocationSet!(L1);
+    fn run(self, op: &impl ChoreoOp<Self::L>) {
         op.locally(self.location, |_| {
             println!("Hello, World!");
         });

chorus_book/src/guide-locations.md

@@ -26,6 +26,23 @@ The `ChoreographyLocation` trait provides the `name` method, which returns the n
 # #[derive(ChoreographyLocation)]
 # struct Bob;
 #
-let name = Alice.name();
+let name = Alice::name();
 assert_eq!(name, "Alice");
 ```
+
+## Location Set
+
+A `LocationSet` is a special type representing a set of `ChoreographyLocation` types. It's used to ensure type safety within the system, and you'll see its application in future sections. To build a `LocationSet` type, you can use the `LocationSet` macro from the `chorus_lib` crate.
+
+```rust
+# extern crate chorus_lib;
+# use chorus_lib::core::ChoreographyLocation;
+# #[derive(ChoreographyLocation)]
+# struct Alice;
+#
+# #[derive(ChoreographyLocation)]
+# struct Bob;
+use chorus_lib::core::LocationSet;
+
+type L = LocationSet!(Alice, Bob);
+```