[Mlir-commits] [mlir] [MLIR][Presburger] Implement computation of generating function for unimodular cones (PR #77235)

[llvmlistbot at llvm.org]

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@@ -63,3 +63,78 @@ MPInt mlir::presburger::detail::getIndex(ConeV cone) {
 
   return cone.determinant();
 }
+
+/// Compute the generating function for a unimodular cone.
+/// This consists of a single term of the form
+/// x^num / prod_j (1 - x^den_j)
+///
+/// den_j is defined as the set of generators of the cone.
+/// num is computed by expressing the vertex as a weighted
+/// sum of the generators, and then taking the floor of the
+/// coefficients.
+GeneratingFunction mlir::presburger::detail::unimodularConeGeneratingFunction(
+    ParamPoint vertex, int sign, ConeH cone) {
+  // `cone` is assumed to be unimodular.
+  assert(getIndex(getDual(cone)) == 1 && "input cone is not unimodular!");
+
+  unsigned numVar = cone.getNumVars();
+  unsigned numIneq = cone.getNumInequalities();
+
+  // Thus its ray matrix, U, is the inverse of the
+  // transpose of its inequality matrix, `cone`.
+  FracMatrix transp(numVar, numIneq);
+  for (unsigned i = 0; i < numVar; ++i)
+    for (unsigned j = 0; j < numIneq; ++j)
+      transp(j, i) = Fraction(cone.atIneq(i, j), 1);
----------------
Abhinav271828 wrote:

We're not transposing a matrix object directly though; this is the inequalities matrix of the IntegerRelation object `cone`, which is not accessible as a matrix.


https://github.com/llvm/llvm-project/pull/77235