Feature to use unbounded weights

CHANGELOG.md

@@ -10,6 +10,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
   DDlog, which will crash DDlog programs at runtime if they overflow the
   weights attached to data values.  This may be preferable to generating
   incorrect results.
+- Rust compilation option `unbounded_weights` for the code generated by
+  DDlog which will never crash DDlog programs at runtime but may be slower.
 
 ## [0.48.2] - Sep 13, 2021
 

doc/tutorial/tutorial.md

@@ -3797,12 +3797,19 @@ Weight overflow in turns leads to silent wrong results at runtime [bug
 878](https://github.com/vmware/differential-datalog/issues/878).
 
 To mitigate this problem, the generated Rust code can be compiled with
-the a feature named `checked_weights`.  This causes programs that
+a feature named `checked_weights`.  This causes programs that
 overflow the weights to crash with a Rust `panic` at runtime instead
 of producing incorrect results.  This can be done e.g., by compiling
 the result produced by the ddlog compiler with a command line like
 `cargo build --release --features=checked_weights`.
 
+Alternatively, the generated Rust code can be compiled with a feature
+named `unbounded_weights`.  This may cause the program to execute
+slower and use more memory, but the program will never produce
+incorrect results.  This can be done e.g., by compiling
+the result produced by the ddlog compiler with a command line like
+`cargo build --release --features=unbounded_weights`.
+
 ## Profiling
 
 DDlog's profiling features are designed to help the programmer identify

lib/ddlog_std.rs

@@ -1264,7 +1264,7 @@ impl<K: Clone, V: Clone> Clone for Group<K, V> {
                 key: key.clone(),
                 group: group
                     .iter()
-                    .map(|(v, w)| tuple2(project(v).clone(), i64::from(*w) as DDWeight))
+                    .map(|(v, w)| tuple2(project(v).clone(), i64::from(w) as DDWeight))
                     .collect(),
             },
             GroupEnum::ByVal { key, group } => GroupEnum::ByVal {
@@ -1435,7 +1435,7 @@ impl<'a, V: Clone> Iterator for GroupIter<'a, V> {
         match self {
             GroupIter::ByRef { iter, project } => match iter.next() {
                 None => None,
-                Some((x, w)) => Some(tuple2(project(x).clone(), i64::from(*w) as DDWeight)),
+                Some((x, w)) => Some(tuple2(project(x).clone(), i64::from(w) as DDWeight)),
             },
             GroupIter::ByVal { iter } => match iter.next() {
                 None => None,
@@ -1531,7 +1531,7 @@ impl<V: Clone> Iterator for GroupIntoIter<V> {
         match self {
             GroupIntoIter::ByRef { iter, project } => match iter.next() {
                 None => None,
-                Some((x, w)) => Some(tuple2(project(x).clone(), i64::from(*w) as DDWeight)),
+                Some((x, w)) => Some(tuple2(project(x).clone(), i64::from(w) as DDWeight)),
             },
             GroupIntoIter::ByVal { iter } => match iter.next() {
                 None => None,

rust/ddlog_benches/Cargo.toml

@@ -5,10 +5,14 @@ edition = "2018"
 license = "MIT"
 
 [features]
-# Use the following to run with checked_weights: 
+# Use the following to run with checked_weights:
 # panic on weight overflow.
 #default = ["benchmarks_ddlog/checked_weights"]
 default = []
+# Use the following to run with unbounded_weights:
+# always correct results, but perhaps slower
+#default = ["benchmarks_ddlog/unbounded_weights"]
+default = []
 
 [dependencies]
 criterion = "0.3.3"

rust/template/Cargo.toml

@@ -14,6 +14,7 @@ command-line = ["cmd_parser", "rustop"]
 nested_ts_32 = ["differential_datalog/nested_ts_32"]
 c_api = ["differential_datalog/c_api"]
 checked_weights = ["differential_datalog/checked_weights"]
+unbounded_weights = ["differential_datalog/unbounded_weights"]
 
 [dependencies]
 abomonation = "0.7"

rust/template/differential_datalog/Cargo.toml

@@ -11,6 +11,8 @@ nested_ts_32 = []
 c_api = []
 # panic on weight overflow
 checked_weights = []
+# use unbounded weights
+unbounded_weights = []
 
 [dependencies]
 #differential-dataflow = "0.11.0"
@@ -25,6 +27,7 @@ ordered-float = { version = "2.0.0", features = ["serde"] }
 fnv = "1.0.2"
 libc = "0.2"
 csv = "1.1"
+either = "1.6"
 num = { version = "0.3", features = ["serde"] }
 sequence_trie = "0.3"
 serde = { version = "1.0", features = ["derive"] }

rust/template/differential_datalog/src/api/update_handler.rs

@@ -440,8 +440,10 @@ impl MTUpdateHandler for MTChainedUpdateHandler {
             self.handlers.iter().map(|h| h.mt_update_cb()).collect();
 
         Arc::new(move |relid, v, w| {
+            // not all weight implementations support copy
+            #[allow(clippy::clone_on_copy)]
             for cb in cbs.iter() {
-                cb(relid, v, w);
+                cb(relid, v, w.clone());
             }
         })
     }