From f1d308e6c7a394256d8ede2979c80d57e3868efa Mon Sep 17 00:00:00 2001
From: Anton Khirnov <anton@khirnov.net>
Date: Fri, 8 Feb 2019 08:48:28 +0100
Subject: Rename fixdiff boundary condition to reflect.

This is what it actually does, we do not support setting arbitrary
derivative values.

API bump.
---
 ell_grid_solve.c | 22 ++++++++--------------
 libmg2d.v        |  2 +-
 mg2d.c           |  2 +-
 mg2d_boundary.h  |  7 ++-----
 mg2d_test.c      |  2 +-
 5 files changed, 13 insertions(+), 22 deletions(-)

diff --git a/ell_grid_solve.c b/ell_grid_solve.c
index 0cefdfd..f992186 100644
--- a/ell_grid_solve.c
+++ b/ell_grid_solve.c
@@ -128,7 +128,7 @@ static void boundaries_apply_fixval(double *dst, const ptrdiff_t dst_stride[2],
     }
 }
 
-static void boundaries_apply_fixdiff(double *dst, const ptrdiff_t dst_stride[2],
+static void boundaries_apply_reflect(double *dst, const ptrdiff_t dst_stride[2],
                                      const double *src, ptrdiff_t src_stride,
                                      size_t boundary_size)
 {
@@ -162,8 +162,8 @@ static void boundaries_apply(EGSContext *ctx)
             boundaries_apply_fixval(dst, dst_strides, ctx->boundaries[i]->val,
                                     ctx->boundaries[i]->val_stride, size_boundary);
             break;
-        case MG2D_BC_TYPE_FIXDIFF:
-            boundaries_apply_fixdiff(dst, dst_strides, ctx->boundaries[i]->val,
+        case MG2D_BC_TYPE_REFLECT:
+            boundaries_apply_reflect(dst, dst_strides, ctx->boundaries[i]->val,
                                      ctx->boundaries[i]->val_stride, size_boundary);
             break;
         }
@@ -185,9 +185,9 @@ static void boundaries_apply(EGSContext *ctx)
                           + mg2d_bnd_is_upper(loc_y) * ((ctx->domain_size[1] - 1) * priv->stride)
                           + mg2d_bnd_is_upper(loc_x) * (ctx->domain_size[0] - 1);
 
-            if (bnd_y->type == MG2D_BC_TYPE_FIXDIFF)
+            if (bnd_y->type == MG2D_BC_TYPE_REFLECT)
                 fact_y *= -1;
-            else if (bnd_x->type == MG2D_BC_TYPE_FIXDIFF)
+            else if (bnd_x->type == MG2D_BC_TYPE_REFLECT)
                 fact_x *= -1;
             else
                 continue;
@@ -380,7 +380,7 @@ static int solve_exact(EGSContext *ctx)
 
                 if (!bnd_fixval) {
                     /* apply the boundary conditions to eliminate the ghostpoint values */
-                    // fixdiff
+                    // reflect
                     for (int bnd_loc = 0; bnd_loc < ARRAY_ELEMS(ctx->boundaries); bnd_loc++) {
                         MG2DBoundary *bnd = ctx->boundaries[bnd_loc];
 
@@ -393,7 +393,7 @@ static int solve_exact(EGSContext *ctx)
 
                         double *dst = mat_row + mg2d_bnd_is_upper(bnd_loc) * ((bnd_len[1] - 1) * bnd_stride[1]);
 
-                        if (!is_bnd[bnd_loc] || bnd->type != MG2D_BC_TYPE_FIXDIFF)
+                        if (!is_bnd[bnd_loc] || bnd->type != MG2D_BC_TYPE_REFLECT)
                             continue;
 
                         for (ptrdiff_t bnd_layer = 1; bnd_layer <= ctx->fd_stencil; bnd_layer++)
@@ -545,13 +545,7 @@ int mg2di_egs_init(EGSContext *ctx)
     for (int i = 0; i < ARRAY_ELEMS(ctx->boundaries); i++) {
         MG2DBoundary *bnd = ctx->boundaries[i];
         const int ci  = mg2d_bnd_coord_idx(i);
-        if (bnd->type == MG2D_BC_TYPE_FIXDIFF) {
-           for (int k = 0; k < ctx->domain_size[!ci]; k++)
-               if (bnd->val[k] != 0.0) {
-                   mg2di_log(&ctx->logger, 0, "Only zero boundary derivative supported\n");
-                   return -ENOSYS;
-               }
-        } else if (bnd->type == MG2D_BC_TYPE_FIXVAL) {
+        if (bnd->type == MG2D_BC_TYPE_FIXVAL) {
             priv->residual_calc_size[ci]--;
         }
     }
diff --git a/libmg2d.v b/libmg2d.v
index 7fb72b7..f4dd528 100644
--- a/libmg2d.v
+++ b/libmg2d.v
@@ -1,4 +1,4 @@
-LIBMG2D_8 {
+LIBMG2D_9 {
     global: mg2d_*;
     local: *;
 };
diff --git a/mg2d.c b/mg2d.c
index 0cb9dd8..5522ed5 100644
--- a/mg2d.c
+++ b/mg2d.c
@@ -456,7 +456,7 @@ static int mg_levels_init(MG2DContext *ctx)
                 else
                     bnd_zero(bdst, ctx->fd_stencil, cur->solver->domain_size[0]);
                 break;
-            case MG2D_BC_TYPE_FIXDIFF:
+            case MG2D_BC_TYPE_REFLECT:
                 bnd_zero(bdst, ctx->fd_stencil, cur->solver->domain_size[0]);
                 break;
             default:
diff --git a/mg2d_boundary.h b/mg2d_boundary.h
index 12c897f..910249f 100644
--- a/mg2d_boundary.h
+++ b/mg2d_boundary.h
@@ -32,12 +32,9 @@ enum MG2DBCType {
      */
     MG2D_BC_TYPE_FIXVAL,
     /**
-     * The normal derivative of the unkown function is fixed on the boundary.
-     *
-     * TODO: the only supported value of the derivative is currently zero, i.e.
-     * periodic boundary conditions.
+     * The unknown function is mirrored across the boundary
      */
-    MG2D_BC_TYPE_FIXDIFF,
+    MG2D_BC_TYPE_REFLECT,
 };
 
 /**
diff --git a/mg2d_test.c b/mg2d_test.c
index a60c5b2..23e52bb 100644
--- a/mg2d_test.c
+++ b/mg2d_test.c
@@ -75,7 +75,7 @@ static double sol_11(double x, double y)
 {
     return M_PI * M_PI * sin(M_PI * x) * sin(M_PI * y);
 }
-#define BC_TYPE MG2D_BC_TYPE_FIXDIFF
+#define BC_TYPE MG2D_BC_TYPE_REFLECT
 #endif
 
 static double (*sol[MG2D_DIFF_COEFF_NB])(double x, double y) = {
-- 
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