mg2d: fail when a full multigrid iteration does not reduce the residual

1 files changed, 5 insertions, 0 deletions

diff --git a/mg2d.c b/mg2d.c
index 902c3cc..a65af6c 100644
--- a/mg2d.c
+++ b/mg2d.c
@@ -527,6 +527,11 @@ int mg2d_solve(MG2DContext *ctx)
         mg2di_log(&priv->logger, MG2D_LOG_VERBOSE,
                   "finished toplevel iteration %d, residual %g -> %g (%g)\n",
                   i, res_prev, res_cur, res_prev / res_cur);
+        if (res_cur / res_prev > 1.0) {
+            mg2di_log(&priv->logger, MG2D_LOG_ERROR, "A multigrid iteration diverged\n");
+            ret = MG2D_ERR_DIVERGE;
+            goto fail;
+        }
         res_prev = res_cur;
     }