1 files changed, 9 insertions, 1 deletions
diff --git a/mg2d.h b/mg2d.h
index 01698a8..8f48361 100644
--- a/mg2d.h
+++ b/mg2d.h
@@ -239,6 +239,13 @@ typedef struct MG2DContext {
      * Set by mg2d_solver_alloc[_mpi]().
      */
     size_t    local_size[2];
+
+    /**
+     * Maximum of the absolute value of the residual.
+     *
+     * Set by mg2d_solve() if it returns 0 or MG2D_ERR_MAXITER_REACHED.
+     */
+    double residual_max;
 } MG2DContext;
 
 /**
@@ -271,7 +278,8 @@ MG2DContext *mg2d_solver_alloc_mpi(MPI_Comm comm, const size_t local_start[2],
  *   - 0 on success
  *   - MG2D_ERR_MAXITER_REACHED if desired tolerance was not reached after
  *     maximum allowed number of iterations were performed. The final
- *     value of the solution is still exported in ctx->u.
+ *     value of the solution is still exported in ctx->u, ctx->residual_max is
+ *     set to the final residual norm.
  *   - MG2D_ERR_DIVERGE if the iteration process has diverged.
  *   - another negative error code on other types of failure
  */