[Mlir-commits] [mlir] [MLIR][Presburger] Definitions for basic functions related to cones (PR #76650)

[Arjun P]

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+//===- Barvinok.h - Barvinok's Algorithm ------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// Functions relating to Barvinok's algorithm.
+// These include functions to manipulate cones (define a cone object, get its
+// dual, and find its index).
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef MLIR_ANALYSIS_PRESBURGER_BARVINOK_H
+#define MLIR_ANALYSIS_PRESBURGER_BARVINOK_H
+
+#include "mlir/Analysis/Presburger/IntegerRelation.h"
+#include "mlir/Analysis/Presburger/Matrix.h"
+#include <optional>
+
+namespace mlir {
+namespace presburger {
+
+// A polyhedron in H-representation is a set of inequalities
+// in d variables with integer coefficients.
+using PolyhedronH = IntegerRelation;
+
+// A polyhedron in V-representation is a set of rays and points, i.e.,
+// vectors, stored as rows of a matrix.
+using PolyhedronV = IntMatrix;
+
+// A cone in either representation is a special case of
+// a polyhedron in that representation.
+using ConeH = PolyhedronH;
+using ConeV = PolyhedronV;
+
+inline ConeH defineHRep(int num_vars) {
+  // We don't distinguish between domain and range variables, so
+  // we set the number of domain variables as 0 and the number of
+  // range variables as the number of actual variables.
+  // There are no symbols (we don't work with parametric cones) and no local
+  // (existentially quantified) variables.
+  // Once the cone is defined, we use `addInequality()` to set inequalities.
+  return ConeH(PresburgerSpace::getSetSpace(/*numDims=*/num_vars,
+                                            /*numSymbols=*/0,
+                                            /*numLocals=*/0));
+}
+
+// Get the index of a cone, i.e., the volume of the parallelepiped
+// spanned by its generators, which is equal to the number of integer
+// points in its fundamental parallelepiped.
+// If the index is 1, the cone is unimodular.
+// Barvinok, A., and J. E. Pommersheim. "An algorithmic theory of lattice points
+// in polyhedra." p. 107 If it has more rays than the dimension, return 0.
+MPInt getIndex(ConeV);
+
+// Get the dual of a cone in H-representation, returning its V-representation.
+// This assumes that the input is pointed at the origin; it fails otherwise.
----------------
Superty wrote:

"fails" is vague. If an assert will fail, state that it "assert-fails".

https://github.com/llvm/llvm-project/pull/76650