Reader plugin (#566)

* add reader plugin

* fix bug

* add assert for write method

* delete comment

* Update CHANGELOG.md

Author: jurgen-lentz

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## Unreleased
 ### Added
+- Interface to include custom reader plugins
+- New test for reader plugin
 ### Fixed
 - revert change from #543 to fix #570 (closing file descriptors)
 - use correct offset value when updating the objective function

src/pyscipopt/__init__.py

@@ -19,6 +19,7 @@
 from pyscipopt.scip      import Presol
 from pyscipopt.scip      import Pricer
 from pyscipopt.scip      import Prop
+from pyscipopt.scip      import Reader
 from pyscipopt.scip      import Sepa
 from pyscipopt.scip      import LP
 from pyscipopt.scip      import Expr

src/pyscipopt/reader.pxi

@@ -0,0 +1,64 @@
+##@file reader.pxi
+#@brief Base class of the Reader Plugin
+cdef class Reader:
+    cdef public Model model
+    cdef public str name
+
+    def readerfree(self):
+        '''calls destructor and frees memory of reader'''
+        pass
+
+    def readerread(self, filename):
+        '''calls read method of reader'''
+        return {}
+
+    def readerwrite(self, file, name, transformed, objsense, objscale, objoffset, binvars, intvars,
+                    implvars, contvars, fixedvars, startnvars, conss, maxnconss, startnconss, genericnames):
+        '''calls write method of reader'''
+        return {}
+
+
+cdef SCIP_RETCODE PyReaderCopy (SCIP* scip, SCIP_READER* reader) with gil:
+    return SCIP_OKAY
+
+cdef SCIP_RETCODE PyReaderFree (SCIP* scip, SCIP_READER* reader) with gil:
+    cdef SCIP_READERDATA* readerdata
+    readerdata = SCIPreaderGetData(reader)
+    PyReader = <Reader>readerdata
+    PyReader.readerfree()
+    Py_DECREF(PyReader)
+    return SCIP_OKAY
+
+cdef SCIP_RETCODE PyReaderRead (SCIP* scip, SCIP_READER* reader, const char* filename, SCIP_RESULT* result) with gil:
+    cdef SCIP_READERDATA* readerdata
+    readerdata = SCIPreaderGetData(reader)
+    PyReader = <Reader>readerdata
+    PyFilename = filename.decode('utf-8')
+    result_dict = PyReader.readerread(PyFilename)
+    result[0] = result_dict.get("result", <SCIP_RESULT>result[0])
+    return SCIP_OKAY
+
+cdef SCIP_RETCODE PyReaderWrite (SCIP* scip, SCIP_READER* reader, FILE* file,
+                                 const char* name, SCIP_PROBDATA* probdata, SCIP_Bool transformed,
+                                 SCIP_OBJSENSE objsense, SCIP_Real objscale, SCIP_Real objoffset, 
+                                 SCIP_VAR** vars, int nvars, int nbinvars, int nintvars, int nimplvars, int ncontvars,
+                                 SCIP_VAR** fixedvars, int nfixedvars, int startnvars,
+                                 SCIP_CONS** conss, int nconss, int maxnconss, int startnconss,
+                                 SCIP_Bool genericnames, SCIP_RESULT* result) with gil:
+    cdef SCIP_READERDATA* readerdata
+    readerdata = SCIPreaderGetData(reader)
+    cdef int fd = fileno(file)
+    PyFile = os.fdopen(fd, "w", closefd=False)
+    PyName = name.decode('utf-8')
+    PyBinVars = [Variable.create(vars[i]) for i in range(nbinvars)]
+    PyIntVars = [Variable.create(vars[i]) for i in range(nbinvars, nintvars)]
+    PyImplVars = [Variable.create(vars[i]) for i in range(nintvars, nimplvars)]
+    PyContVars = [Variable.create(vars[i]) for i in range(nimplvars, ncontvars)]
+    PyFixedVars = [Variable.create(fixedvars[i]) for i in range(nfixedvars)]
+    PyConss = [Constraint.create(conss[i]) for i in range(nconss)]
+    PyReader = <Reader>readerdata
+    result_dict = PyReader.readerwrite(PyFile, PyName, transformed, objsense, objscale, objoffset,
+                                       PyBinVars, PyIntVars, PyImplVars, PyContVars, PyFixedVars, startnvars,
+                                       PyConss, maxnconss, startnconss, genericnames)
+    result[0] = result_dict.get("result", <SCIP_RESULT>result[0])
+    return SCIP_OKAY

src/pyscipopt/scip.pyx

@@ -3,14 +3,16 @@
 import weakref
 from os.path import abspath
 from os.path import splitext
+import os
 import sys
 import warnings
 
 cimport cython
 from cpython cimport Py_INCREF, Py_DECREF
 from cpython.pycapsule cimport PyCapsule_New, PyCapsule_IsValid, PyCapsule_GetPointer
 from libc.stdlib cimport malloc, free
-from libc.stdio cimport fdopen
+from libc.stdio cimport fdopen, fclose
+from posix.stdio cimport fileno
 
 from collections.abc import Iterable
 from itertools import repeat
@@ -28,6 +30,7 @@ include "presol.pxi"
 include "pricer.pxi"
 include "propagator.pxi"
 include "sepa.pxi"
+include "reader.pxi"
 include "relax.pxi"
 include "nodesel.pxi"
 
@@ -3671,6 +3674,24 @@ cdef class Model:
         sepa.name = name
         Py_INCREF(sepa)
 
+    def includeReader(self, Reader reader, name, desc, ext):
+        """Include a reader
+
+        :param Reader reader: reader
+        :param name: name of reader
+        :param desc: description of reader
+        :param ext: file extension of reader
+
+        """
+        n = str_conversion(name)
+        d = str_conversion(desc)
+        e = str_conversion(ext)
+        PY_SCIP_CALL(SCIPincludeReader(self._scip, n, d, e, PyReaderCopy, PyReaderFree,
+                                          PyReaderRead, PyReaderWrite, <SCIP_READERDATA*>reader))
+        reader.model = <Model>weakref.proxy(self)
+        reader.name = name
+        Py_INCREF(reader)
+
     def includeProp(self, Prop prop, name, desc, presolpriority, presolmaxrounds,
                     proptiming, presoltiming=SCIP_PRESOLTIMING_FAST, priority=1, freq=1, delay=True):
         """Include a propagator.

tests/test_reader.py

@@ -0,0 +1,85 @@
+import pytest
+import os
+
+from pyscipopt import Model, quicksum, Reader, SCIP_RESULT
+
+class SudokuReader(Reader):
+
+    def readerread(self, filename):
+        with open(filename, "r") as f:
+            input = f.readline().split()
+
+            for i in range(len(input)):
+                input[i] = int(input[i])
+
+            x = {}
+            for i in range(9):
+                for j in range(9):
+                    for k in range(9):
+                        name = str(i)+','+str(j)+','+str(k)
+                        x[i,j,k] = self.model.addVar(name, vtype='B')
+            
+            # fill in initial values
+            for i in range(9):
+                for j in range(9):
+                    if input[j + 9*i] != 0:
+                        self.model.addCons(x[i,j,input[j + 9*i]-1] == 1)
+
+            # only one digit in every field
+            for i in range(9):
+                for j in range(9):
+                    self.model.addCons(quicksum(x[i,j,k] for k in range(9)) == 1)
+
+            # set up row and column constraints
+            for ind in range(9):
+                for k in range(9):
+                    self.model.addCons(quicksum(x[ind,j,k] for j in range(9)) == 1)
+                    self.model.addCons(quicksum(x[i,ind,k] for i in range(9)) == 1)
+
+            # set up square constraints
+            for row in range(3):
+                for col in range(3):
+                    for k in range(9):
+                        self.model.addCons(quicksum(x[i+3*row, j+3*col, k] for i in range(3) for j in range(3)) == 1)
+
+        return {"result": SCIP_RESULT.SUCCESS}
+
+    def readerwrite(self, file, name, transformed, objsense, objscale, objoffset, binvars, intvars,
+                    implvars, contvars, fixedvars, startnvars, conss, maxnconss, startnconss, genericnames):
+        with file as f:
+            f.write(name)
+
+        return {"result": SCIP_RESULT.SUCCESS}
+
+
+def createFile(filename):
+    with open(filename, "w") as f:
+        f.write("5 3 0 0 7 0 0 0 0 6 0 0 1 9 5 0 0 0 0 9 8 0 0 0 0 6 0 8 0 0 0 6 0 0 0 3 4 0 0 8 0 3 0 0 1 7 0 0 0 2 0 0 0 6 0 6 0 0 0 0 2 8 0 0 0 0 4 1 9 0 0 5 0 0 0 0 8 0 0 7 9")
+
+def deleteFile(filename):
+    os.remove(filename)
+
+def test():
+    createFile("tmp.sod")
+
+    m = Model("soduko")
+    reader = SudokuReader()
+
+    m.includeReader(reader, "sodreader", "PyReader for soduko problem", "sod")
+
+    m.readProblem("tmp.sod")
+
+    m.optimize()
+
+    deleteFile("tmp.sod")
+
+    m.writeProblem("model.sod")
+    with open("model.sod", "r") as f:
+        input = f.readline()
+    assert input == "soduko"
+
+    deleteFile("model.sod")
+
+
+if __name__ == "__main__":
+    test()