From 07d3ce14e796e15e66dd40c8d8f12bf99738eec4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Th=C3=A9ophile=20Bastian?= <contact@tobast.fr>
Date: Wed, 8 Mar 2023 11:15:11 +0100
Subject: [PATCH] Partition: avoid tasks too close in time

---
 repartir_taches/entrypoint.py |  1 +
 repartir_taches/partition.py  | 43 ++++++++++++++++++++++++++---------
 2 files changed, 33 insertions(+), 11 deletions(-)

diff --git a/repartir_taches/entrypoint.py b/repartir_taches/entrypoint.py
index 040f778..9028a65 100644
--- a/repartir_taches/entrypoint.py
+++ b/repartir_taches/entrypoint.py
@@ -75,6 +75,7 @@ def assigner_taches(root_task: Category | Task, group_count: int):
         multiplicity[t_id] = task.nb_groups
     repart: list[list[TaskId]] = partition(
         bin_count=group_count,
+        tasks=all_tasks,
         costs=costs,
         multiplicity=multiplicity,
     )
diff --git a/repartir_taches/partition.py b/repartir_taches/partition.py
index 86c3249..da44a48 100644
--- a/repartir_taches/partition.py
+++ b/repartir_taches/partition.py
@@ -1,12 +1,16 @@
 """ Implements Multiway number partitioning greedy algorithm """
 
 import typing as t
+import logging
 from sortedcontainers import SortedList
+from .config import Task
 
 __all__ = ["TaskId", "partition"]
 
 TaskId = t.NewType("TaskId", int)
 
+logger = logging.getLogger(__name__)
+
 
 class PartitionException(Exception):
     """An exception occurring during partitioning"""
@@ -36,7 +40,10 @@ class Bin:
 
 
 def partition(
-    bin_count: int, costs: dict[TaskId, int], multiplicity: dict[TaskId, int]
+    bin_count: int,
+    tasks: list[Task],
+    costs: dict[TaskId, int],
+    multiplicity: dict[TaskId, int],
 ) -> list[list[TaskId]]:
     """Partitions the tasks, each with cost `costs[i]`, into `bin_count` bins. Each
     task has multiplicity `multiplicity[i]`, copies of the same task being mutually
@@ -50,22 +57,36 @@ def partition(
     ordered_tasks.sort(key=lambda x: costs[x], reverse=True)
 
     for task in ordered_tasks:
-        least_full: Bin
-        least_full_pos: int
+        possible_bins: list[int] = []
+        min_possible: t.Optional[int] = None
         for pos, cur_bin in enumerate(bins):
-            if task not in cur_bin:
-                least_full = cur_bin
-                least_full_pos = pos
+            if min_possible is not None and cur_bin.cost > min_possible:
                 break
-        else:
+            if task not in cur_bin:
+                if min_possible is None:
+                    min_possible = cur_bin.cost
+                possible_bins.append(pos)
+        if not possible_bins:
             raise UnsolvableConflict(
                 "Pas assez de groupes pour affecter la tâche "
-                + f"{task} {multiplicity[task]} fois."
+                + f"{tasks[task].qualified_name} {multiplicity[task]} fois."
             )
 
-        del bins[least_full_pos]
-        least_full.add(task, costs[task])
-        bins.add(least_full)
+        # Pick one of the groups -- maximize distance to other tasks
+        closest_assigned = []
+        for cur_bin_id in possible_bins:
+            cur_bin = bins[cur_bin_id]
+            if cur_bin.elts:
+                closest_assigned.append(min((abs(elt - task) for elt in cur_bin.elts)))
+            else:
+                closest_assigned.append(len(costs) + 1)
+
+        assign_to_bin_id, _ = max(enumerate(closest_assigned), key=lambda x: x[1])
+        assign_to_bin = bins[possible_bins[assign_to_bin_id]]
+
+        del bins[assign_to_bin_id]
+        assign_to_bin.add(task, costs[task])
+        bins.add(assign_to_bin)
 
     out: list[list[TaskId]] = []
     for cur_bin in bins: