Write instances (#7)

* Split-up Instance; implement write

* Update docstring Instance.py

* Correct calculation of metadata

* Update README

README.md

@@ -13,12 +13,12 @@ FJSPLIB is a Python package for reading and writing flexible job shop problem (F
 The FJSPLIB format is as follows:
 
 ``` sh
-<num jobs> <num machines> <average operations per job>
+<num jobs> <num machines> <avg num machines per operation>
 <num operations> * (<num machines> * (<machine idx> <duration>))
 ...
 ```
 
-The first line contains data about the number of jobs, number machines and average number of operations per job.
+The first line contains data about the number of jobs, number machines and average number of machines that can process an operation.
 The following lines each represent the job data, one line for each job.
 These lines are each parsed as follows:
 - The first number denotes the number of operations for this job.

fjsplib/Instance.py

@@ -0,0 +1,30 @@
+from dataclasses import dataclass
+
+
+@dataclass
+class Instance:
+    """
+    The FJSPLIB instance data.
+
+    Parameters
+    ----------
+    num_jobs
+        The number of jobs.
+    num_machines
+        The number of machines.
+    num_operations
+        The number of operations.
+    jobs
+        A list of job data, each job consisting of a list of operations.
+        Operations are list of tuples, where each tuple consists of a machine
+        index and a processing time.
+    precedences
+        A list of tuples consisting of two operation indices, representing the
+        precedence relationship of two operations.
+    """
+
+    num_jobs: int
+    num_machines: int
+    num_operations: int
+    jobs: list[list[list[tuple[int, int]]]]
+    precedences: list[tuple[int, int]]

fjsplib/__init__.py

@@ -1 +1,3 @@
+from .Instance import Instance as Instance
 from .read import read as read
+from .write import write as write

fjsplib/read.py

@@ -1,38 +1,12 @@
-from dataclasses import dataclass
 from pathlib import Path
 from typing import Union
 
+from fjsplib.Instance import Instance
+
 ProcessingData = list[tuple[int, int]]
 Arc = tuple[int, int]
 
 
-@dataclass
-class Instance:
-    """
-    The FJSPLIB instance data.
-
-    Parameters
-    ----------
-    num_jobs
-        The number of jobs.
-    num_machines
-        The number of machines.
-    num_operations
-        The number of operations.
-    jobs
-        A list of job data, each job consisting of a list of operation indices.
-    precedences
-        A list of tuples consisting of two operation indices, representing the
-        precedence relationship of two operations.
-    """
-
-    num_jobs: int
-    num_machines: int
-    num_operations: int
-    jobs: list[list[ProcessingData]]
-    precedences: list[tuple[int, int]]
-
-
 def parse_job_line(line: list[int]) -> list[ProcessingData]:
     """
     Parses a FJSPLIB job data line of the following form:

fjsplib/write.py

@@ -0,0 +1,44 @@
+from pathlib import Path
+from typing import Union
+
+from .Instance import Instance
+
+
+def write(where: Union[Path, str], instance: Instance):
+    """
+    Writes a problem instance to file in FJSPLIB format.
+
+    Parameters
+    ----------
+    where
+        Location to write the instance to.
+    instance
+        The problem instance.
+    """
+    lines = []
+
+    # The flexibility is the average number of eligible machines per operation.
+    num_eligible = sum([len(task) for ops in instance.jobs for task in ops])
+    flexibility = round(num_eligible / instance.num_operations, 1)
+
+    metadata = f"{instance.num_jobs} {instance.num_machines} {flexibility}"
+    lines.append(metadata)
+
+    for operations in instance.jobs:
+        job = [len(operations)]
+
+        for processing_data in operations:
+            num_eligible = len(processing_data)
+            job.append(num_eligible)
+
+            for machine, duration in processing_data:
+                # Machine indices are 1-indexed in FJSPLIB.
+                job.extend([machine + 1, duration])
+
+        line = " ".join(str(num) for num in job)
+        lines.append(line)
+
+    formatted = "\n".join(lines)
+
+    with open(where, "w") as fh:
+        fh.write(formatted)

tests/data/classic.fjs

@@ -1,3 +1,3 @@
-2 3 2.2
+2 3 1.7
 1 2 1 1 2 2
 2 1 1 1 2 3 1 2 1

tests/test_write.py

@@ -0,0 +1,22 @@
+from pathlib import Path
+
+from numpy.testing import assert_equal
+
+from fjsplib.write import write
+from tests.utils import read
+
+
+def test_write(tmp_path: Path):
+    """
+    Tests that ``write`` correctly writes an FJSPLIB instance to a file.
+    """
+    instance = read("data/classic.fjs")
+    write(tmp_path / "classic.fjs", instance)
+
+    expected = [
+        "2 3 1.7",
+        "1 2 1 1 2 2",
+        "2 1 1 1 2 3 1 2 1",
+    ]
+    with open(tmp_path / "classic.fjs", "r") as fh:
+        assert_equal(fh.read(), "\n".join(expected))