Fix #500: [Model] SequencingToMinimizeMaximumCumulativeCost

docs/paper/reductions.typ

@@ -131,6 +131,7 @@
   "MultiprocessorScheduling": [Multiprocessor Scheduling],
   "PrecedenceConstrainedScheduling": [Precedence Constrained Scheduling],
   "MinimumTardinessSequencing": [Minimum Tardiness Sequencing],
+  "SequencingToMinimizeMaximumCumulativeCost": [Sequencing to Minimize Maximum Cumulative Cost],
   "ConsecutiveOnesSubmatrix": [Consecutive Ones Submatrix],
   "SumOfSquaresPartition": [Sum of Squares Partition],
   "SequencingWithinIntervals": [Sequencing Within Intervals],
@@ -3498,6 +3499,80 @@ A classical NP-complete problem from Garey and Johnson @garey1979[Ch.~3, p.~76],
   ]
 }
 
+#{
+  let x = load-model-example("SequencingToMinimizeMaximumCumulativeCost")
+  let costs = x.instance.costs
+  let precs = x.instance.precedences
+  let bound = x.instance.bound
+  let ntasks = costs.len()
+  let lehmer = x.optimal_config
+  let schedule = {
+    let avail = range(ntasks)
+    let result = ()
+    for c in lehmer {
+      result.push(avail.at(c))
+      avail = avail.enumerate().filter(((i, v)) => i != c).map(((i, v)) => v)
+    }
+    result
+  }
+  let prefix-sums = {
+    let running = 0
+    let result = ()
+    for task in schedule {
+      running += costs.at(task)
+      result.push(running)
+    }
+    result
+  }
+  [
+    #problem-def("SequencingToMinimizeMaximumCumulativeCost")[
+      Given a set $T$ of $n$ tasks, a precedence relation $prec.eq$ on $T$, an integer cost function $c: T -> ZZ$ (negative values represent profits), and a bound $K in ZZ$, determine whether there exists a one-machine schedule $sigma: T -> {1, 2, dots, n}$ that respects the precedence constraints and satisfies
+      $sum_(sigma(t') lt.eq sigma(t)) c(t') lt.eq K$
+      for every task $t in T$.
+    ][
+      Sequencing to Minimize Maximum Cumulative Cost is the scheduling problem SS7 in Garey & Johnson @garey1979. It is NP-complete by transformation from Register Sufficiency, even when every task cost is in ${-1, 0, 1}$ @garey1979. The problem models precedence-constrained task systems with resource consumption and release, where a negative cost corresponds to a profit or resource refund accumulated as the schedule proceeds.
+
+      When the precedence constraints form a series-parallel digraph, #cite(<abdelWahabKameda1978>, form: "prose") gave a polynomial-time algorithm running in $O(n^2)$ time. #cite(<monmaSidney1979>, form: "prose") placed the problem in a broader family of sequencing objectives solvable efficiently on series-parallel precedence structures. The implementation here uses Lehmer-code enumeration of task orders, so the direct exact search induced by the model runs in $O(n!)$ time.
+
+      *Example.* Consider $n = #ntasks$ tasks with costs $(#costs.map(c => str(c)).join(", "))$, precedence constraints #{precs.map(p => [$t_#(p.at(0) + 1) prec.eq t_#(p.at(1) + 1)$]).join(", ")}, and bound $K = #bound$. The sample schedule $(#schedule.map(t => $t_#(t + 1)$).join(", "))$ has cumulative sums $(#prefix-sums.map(v => str(v)).join(", "))$, so every prefix stays at or below $K = #bound$.
+
+      #figure(
+        {
+          let pos = rgb("#f28e2b")
+          let neg = rgb("#76b7b2")
+          let zero = rgb("#bab0ab")
+          align(center, stack(dir: ttb, spacing: 0.35cm,
+            stack(dir: ltr, spacing: 0.08cm,
+              ..schedule.enumerate().map(((i, task)) => {
+                let cost = costs.at(task)
+                let fill = if cost > 0 {
+                  pos.transparentize(70%)
+                } else if cost < 0 {
+                  neg.transparentize(65%)
+                } else {
+                  zero.transparentize(65%)
+                }
+                stack(dir: ttb, spacing: 0.05cm,
+                  box(width: 1.0cm, height: 0.6cm, fill: fill, stroke: 0.4pt + luma(120),
+                    align(center + horizon, text(8pt, weight: "bold")[$t_#(task + 1)$])),
+                  text(6pt, if cost >= 0 { $+ #cost$ } else { $#cost$ }),
+                )
+              }),
+            ),
+            stack(dir: ltr, spacing: 0.08cm,
+              ..prefix-sums.map(v => {
+                box(width: 1.0cm, align(center + horizon, text(7pt)[$#v$]))
+              }),
+            ),
+            text(7pt, [prefix sums after each scheduled task]),
+          ))
+        },
+        caption: [A satisfying schedule for Sequencing to Minimize Maximum Cumulative Cost. Orange boxes add cost, teal boxes release cost, and the displayed prefix sums $(#prefix-sums.map(v => str(v)).join(", "))$ never exceed $K = #bound$.],
+      ) <fig:seq-max-cumulative>
+    ]
+  ]
+}
+
 #problem-def("DirectedTwoCommodityIntegralFlow")[
   Given a directed graph $G = (V, A)$ with arc capacities $c: A -> ZZ^+$, two source-sink pairs $(s_1, t_1)$ and $(s_2, t_2)$, and requirements $R_1, R_2 in ZZ^+$, determine whether there exist two integral flow functions $f_1, f_2: A -> ZZ_(>= 0)$ such that (1) $f_1(a) + f_2(a) <= c(a)$ for all $a in A$, (2) flow $f_i$ is conserved at every vertex except $s_1, s_2, t_1, t_2$, and (3) the net flow into $t_i$ under $f_i$ is at least $R_i$ for $i in {1, 2}$.
 ][

docs/paper/references.bib

@@ -137,6 +137,28 @@ @article{evenItaiShamir1976
   doi     = {10.1137/0205048}
 }
 
+@article{abdelWahabKameda1978,
+  author  = {H. M. Abdel-Wahab and T. Kameda},
+  title   = {Scheduling to Minimize Maximum Cumulative Cost Subject to Series-Parallel Precedence Constraints},
+  journal = {Operations Research},
+  volume  = {26},
+  number  = {1},
+  pages   = {141--158},
+  year    = {1978},
+  doi     = {10.1287/opre.26.1.141}
+}
+
+@article{monmaSidney1979,
+  author  = {Clyde L. Monma and Jeffrey B. Sidney},
+  title   = {Sequencing with Series-Parallel Precedence Constraints},
+  journal = {Mathematics of Operations Research},
+  volume  = {4},
+  number  = {3},
+  pages   = {215--224},
+  year    = {1979},
+  doi     = {10.1287/moor.4.3.215}
+}
+
 @article{evenTarjan1976,
   author  = {Shimon Even and Robert Endre Tarjan},
   title   = {A Combinatorial Problem Which Is Complete in Polynomial Space},

problemreductions-cli/src/cli.rs

@@ -269,6 +269,7 @@ Flags by problem type:
   FlowShopScheduling              --task-lengths, --deadline [--num-processors]
   StaffScheduling                 --schedules, --requirements, --num-workers, --k
   MinimumTardinessSequencing      --n, --deadlines [--precedence-pairs]
+  SequencingToMinimizeMaximumCumulativeCost --costs, --bound [--precedence-pairs]
   RectilinearPictureCompression   --matrix (0/1), --k
   SCS                             --strings, --bound [--alphabet-size]
   StringToStringCorrection         --source-string, --target-string, --bound [--alphabet-size]
@@ -476,6 +477,9 @@ pub struct CreateArgs {
     /// Input strings for LCS (e.g., "ABAC;BACA" or "0,1,0;1,0,1") or SCS (e.g., "0,1,2;1,2,0")
     #[arg(long)]
     pub strings: Option<String>,
+    /// Task costs for SequencingToMinimizeMaximumCumulativeCost (comma-separated, e.g., "2,-1,3,-2,1,-3")
+    #[arg(long, allow_hyphen_values = true)]
+    pub costs: Option<String>,
     /// Directed arcs for directed graph problems (e.g., 0>1,1>2,2>0)
     #[arg(long)]
     pub arcs: Option<String>,

problemreductions-cli/src/commands/create.rs

@@ -17,8 +17,9 @@ use problemreductions::models::misc::{
     BinPacking, CbqRelation, ConjunctiveBooleanQuery, FlowShopScheduling, LongestCommonSubsequence,
     MinimumTardinessSequencing, MultiprocessorScheduling, PaintShop, PartiallyOrderedKnapsack,
     QueryArg, RectilinearPictureCompression, ResourceConstrainedScheduling,
-    SequencingWithReleaseTimesAndDeadlines, SequencingWithinIntervals, ShortestCommonSupersequence,
-    StringToStringCorrection, SubsetSum, SumOfSquaresPartition,
+    SequencingToMinimizeMaximumCumulativeCost, SequencingWithReleaseTimesAndDeadlines,
+    SequencingWithinIntervals, ShortestCommonSupersequence, StringToStringCorrection, SubsetSum,
+    SumOfSquaresPartition,
 };
 use problemreductions::models::BiconnectivityAugmentation;
 use problemreductions::prelude::*;
@@ -85,6 +86,7 @@ fn all_data_flags_empty(args: &CreateArgs) -> bool {
         && args.bound.is_none()
         && args.pattern.is_none()
         && args.strings.is_none()
+        && args.costs.is_none()
         && args.arcs.is_none()
         && args.source.is_none()
         && args.sink.is_none()
@@ -218,6 +220,50 @@ fn resolve_rule_example(
         })
 }
 
+fn parse_precedence_pairs(raw: Option<&str>) -> Result<Vec<(usize, usize)>> {
+    raw.filter(|s| !s.is_empty())
+        .map(|s| {
+            s.split(',')
+                .map(|pair| {
+                    let pair = pair.trim();
+                    let (pred, succ) = pair.split_once('>').ok_or_else(|| {
+                        anyhow::anyhow!(
+                            "Invalid --precedence-pairs value '{}': expected 'u>v'",
+                            pair
+                        )
+                    })?;
+                    let pred = pred.trim().parse::<usize>().map_err(|_| {
+                        anyhow::anyhow!(
+                            "Invalid --precedence-pairs value '{}': expected 'u>v' with nonnegative integer indices",
+                            pair
+                        )
+                    })?;
+                    let succ = succ.trim().parse::<usize>().map_err(|_| {
+                        anyhow::anyhow!(
+                            "Invalid --precedence-pairs value '{}': expected 'u>v' with nonnegative integer indices",
+                            pair
+                        )
+                    })?;
+                    Ok((pred, succ))
+                })
+                .collect()
+        })
+        .unwrap_or_else(|| Ok(vec![]))
+}
+
+fn validate_precedence_pairs(precedences: &[(usize, usize)], num_tasks: usize) -> Result<()> {
+    for &(pred, succ) in precedences {
+        anyhow::ensure!(
+            pred < num_tasks && succ < num_tasks,
+            "precedence index out of range: ({}, {}) but num_tasks = {}",
+            pred,
+            succ,
+            num_tasks
+        );
+    }
+    Ok(())
+}
+
 fn create_from_example(args: &CreateArgs, out: &OutputConfig) -> Result<()> {
     let example_spec = args
         .example
@@ -371,6 +417,9 @@ fn example_for(canonical: &str, graph_type: Option<&str>) -> &'static str {
             "--num-attributes 6 --dependencies \"0,1>2;0,2>3;1,3>4;2,4>5\" --k 2"
         }
         "ShortestCommonSupersequence" => "--strings \"0,1,2;1,2,0\" --bound 4",
+        "SequencingToMinimizeMaximumCumulativeCost" => {
+            "--costs 2,-1,3,-2,1,-3 --precedence-pairs \"0>2,1>2,1>3,2>4,3>5,4>5\" --bound 4"
+        }
         "ConjunctiveQueryFoldability" => "(use --example ConjunctiveQueryFoldability)",
         "ConjunctiveBooleanQuery" => {
             "--domain-size 6 --relations \"2:0,3|1,3|2,4;3:0,1,5|1,2,5\" --conjuncts-spec \"0:v0,c3;0:v1,c3;1:v0,v1,c5\""
@@ -470,6 +519,41 @@ fn parse_nonnegative_usize_bound(bound: i64, problem_name: &str, usage: &str) ->
         .map_err(|_| anyhow::anyhow!("{problem_name} requires nonnegative --bound\n\n{usage}"))
 }
 
+fn validate_sequencing_within_intervals_inputs(
+    release_times: &[u64],
+    deadlines: &[u64],
+    lengths: &[u64],
+    usage: &str,
+) -> Result<()> {
+    if release_times.len() != deadlines.len() {
+        bail!("release_times and deadlines must have the same length\n\n{usage}");
+    }
+    if release_times.len() != lengths.len() {
+        bail!("release_times and lengths must have the same length\n\n{usage}");
+    }
+
+    for (i, ((&release_time, &deadline), &length)) in release_times
+        .iter()
+        .zip(deadlines.iter())
+        .zip(lengths.iter())
+        .enumerate()
+    {
+        let end = release_time.checked_add(length).ok_or_else(|| {
+            anyhow::anyhow!("Task {i}: overflow computing r(i) + l(i)\n\n{usage}")
+        })?;
+        if end > deadline {
+            bail!(
+                "Task {i}: r({}) + l({}) > d({}), time window is empty\n\n{usage}",
+                release_time,
+                length,
+                deadline
+            );
+        }
+    }
+
+    Ok(())
+}
+
 fn print_problem_help(canonical: &str, graph_type: Option<&str>) -> Result<()> {
     let is_geometry = matches!(
         graph_type,
@@ -1800,39 +1884,14 @@ pub fn create(args: &CreateArgs, out: &OutputConfig) -> Result<()> {
                 )
             })?;
             let deadlines: Vec<usize> = util::parse_comma_list(deadlines_str)?;
-            let precedences: Vec<(usize, usize)> = match args.precedence_pairs.as_deref() {
-                Some(s) if !s.is_empty() => s
-                    .split(',')
-                    .map(|pair| {
-                        let parts: Vec<&str> = pair.trim().split('>').collect();
-                        anyhow::ensure!(
-                            parts.len() == 2,
-                            "Invalid precedence format '{}', expected 'u>v'",
-                            pair.trim()
-                        );
-                        Ok((
-                            parts[0].trim().parse::<usize>()?,
-                            parts[1].trim().parse::<usize>()?,
-                        ))
-                    })
-                    .collect::<Result<Vec<_>>>()?,
-                _ => vec![],
-            };
+            let precedences = parse_precedence_pairs(args.precedence_pairs.as_deref())?;
             anyhow::ensure!(
                 deadlines.len() == num_tasks,
                 "deadlines length ({}) must equal num_tasks ({})",
                 deadlines.len(),
                 num_tasks
             );
-            for &(pred, succ) in &precedences {
-                anyhow::ensure!(
-                    pred < num_tasks && succ < num_tasks,
-                    "precedence index out of range: ({}, {}) but num_tasks = {}",
-                    pred,
-                    succ,
-                    num_tasks
-                );
-            }
+            validate_precedence_pairs(&precedences, num_tasks)?;
             (
                 ser(MinimumTardinessSequencing::new(
                     num_tasks,
@@ -1843,6 +1902,33 @@ pub fn create(args: &CreateArgs, out: &OutputConfig) -> Result<()> {
             )
         }
 
+        // SequencingToMinimizeMaximumCumulativeCost
+        "SequencingToMinimizeMaximumCumulativeCost" => {
+            let costs_str = args.costs.as_deref().ok_or_else(|| {
+                anyhow::anyhow!(
+                    "SequencingToMinimizeMaximumCumulativeCost requires --costs\n\n\
+                     Usage: pred create SequencingToMinimizeMaximumCumulativeCost --costs 2,-1,3,-2,1,-3 --precedence-pairs \"0>2,1>2,1>3,2>4,3>5,4>5\" --bound 4"
+                )
+            })?;
+            let bound = args.bound.ok_or_else(|| {
+                anyhow::anyhow!(
+                    "SequencingToMinimizeMaximumCumulativeCost requires --bound\n\n\
+                     Usage: pred create SequencingToMinimizeMaximumCumulativeCost --costs 2,-1,3,-2,1,-3 --precedence-pairs \"0>2,1>2,1>3,2>4,3>5,4>5\" --bound 4"
+                )
+            })?;
+            let costs: Vec<i64> = util::parse_comma_list(costs_str)?;
+            let precedences = parse_precedence_pairs(args.precedence_pairs.as_deref())?;
+            validate_precedence_pairs(&precedences, costs.len())?;
+            (
+                ser(SequencingToMinimizeMaximumCumulativeCost::new(
+                    costs,
+                    precedences,
+                    bound,
+                ))?,
+                resolved_variant.clone(),
+            )
+        }
+
         // SequencingWithinIntervals
         "SequencingWithinIntervals" => {
             let usage = "Usage: pred create SequencingWithinIntervals --release-times 0,0,5 --deadlines 11,11,6 --lengths 3,1,1";
@@ -1858,6 +1944,12 @@ pub fn create(args: &CreateArgs, out: &OutputConfig) -> Result<()> {
             let release_times: Vec<u64> = util::parse_comma_list(rt_str)?;
             let deadlines: Vec<u64> = util::parse_comma_list(dl_str)?;
             let lengths: Vec<u64> = util::parse_comma_list(len_str)?;
+            validate_sequencing_within_intervals_inputs(
+                &release_times,
+                &deadlines,
+                &lengths,
+                usage,
+            )?;
             (
                 ser(SequencingWithinIntervals::new(
                     release_times,
@@ -4266,6 +4358,9 @@ mod tests {
             domain_size: None,
             relations: None,
             conjuncts_spec: None,
+            costs: None,
+            cut_bound: None,
+            size_bound: None,
         }
     }