Merge pull request #69 from jcavat/lovasoa-better_lp_sum

Lovasoa better lp sum
rust-or · Feb 10, 2021 · c622847 · c622847
2 parents 4ed69c6 5f59fef
commit c622847
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Showing 2 changed files with 21 additions and 14 deletions.
diff --git a/src/dsl/variables.rs b/src/dsl/variables.rs
@@ -319,6  319,10 @@ impl LpExpression {
        }
     }
 
     pub fn literal(value: f32) -> Self {
         value.into()
     }
 
     #[cfg(test)]
     fn build(root: LpExprArenaIndex, arena: Vec<LpExprNode>) -> Self {
         LpExpression {
@@ -1344,19  1348,21 @@ impl ToTokens for LpConstraint {
 /// problem  = lp_sum(v).equal(10.0);
 /// ```
 ///
-pub fn lp_sum<T>(not_yet_lp_expr_arenas: &Vec<T>) -> LpExpression where T: Into<LpExpression>   Clone {
-    match not_yet_lp_expr_arenas.first() {
-        Some(first) => {
-            let mut arena: LpExpression = first.clone().into();
-            for a in not_yet_lp_expr_arenas[1..].iter() {
-                arena = arena.merge_cloned_arenas(&a.clone().into(), Addition);
-            }
-            arena
-        },
-        None => {
-            panic!("vector should have at least one element")
 pub fn lp_sum<T>(expr: &Vec<T>) -> LpExpression
     where T: Into<LpExpression>   Clone {
     let mut results: Vec<LpExpression> = expr.iter().map(|e| e.clone().into()).collect();
     let mut next = Vec::with_capacity(results.len() / 2);
     while results.len() > 1 {
         while results.len() >= 2 {
             let right = results.pop().expect("impossible because len>2");
             let left = results.pop().expect("impossible because len>2");
             next.push(left   right)
         }
         next.append(&mut results);
         next.reverse(); // Required only if we want to maintain the order of operations
         std::mem::swap(&mut results, &mut next)
     }
     results.into_iter().next().unwrap_or( LpExpression::literal(0.0) )
 }
 
 pub fn sum<'a, T: 'a,U: 'a>(expr: &'a Vec<T>, f: impl Fn(&'a T) -> U) -> LpExpression where U: Into<LpExpression>   Clone {

diff --git a/tests/expression.rs b/tests/expression.rs
@@ -175,9  175,10 @@ fn expression_with_lp_sum() {
         lp_sum(expr3).le(5.5).to_lp_file_format(),
         "a <= 5.5"
     );
-    assert!(
-        std::panic::catch_unwind( || lp_sum(empty)).is_err(),
-        "should panic if empty vec"
     assert_eq!(
         lp_sum(empty).to_lp_file_format(),
         "0",
         "should not panic if empty vec"
     );
 }