From 8a139859d22012436be404388fd611fb6126bc7f Mon Sep 17 00:00:00 2001
From: Anton Khirnov <anton@khirnov.net>
Date: Mon, 11 Mar 2019 09:58:15 +0100
Subject: mg2d: make the refinement depth/exact solve size configurable

API bump
---
 libmg2d.v |  2 +-
 mg2d.c    | 27 +++++++++++++++++----------
 mg2d.h    | 12 ++++++++++++
 3 files changed, 30 insertions(+), 11 deletions(-)

diff --git a/libmg2d.v b/libmg2d.v
index c01a69f..3e4fb25 100644
--- a/libmg2d.v
+++ b/libmg2d.v
@@ -1,4 +1,4 @@
-LIBMG2D_10 {
+LIBMG2D_11 {
     global: mg2d_*;
     local: *;
 };
diff --git a/mg2d.c b/mg2d.c
index 8c9a15b..a6c6f5d 100644
--- a/mg2d.c
+++ b/mg2d.c
@@ -34,8 +34,6 @@
 #include "mg2d_boundary_internal.h"
 #include "mg2d_constants.h"
 
-#define LEVELS_MAX 16
-
 typedef struct MG2DLevel {
     unsigned int  depth;
 
@@ -523,21 +521,32 @@ static int threadpool_init(MG2DContext *ctx)
     return 0;
 }
 
+static int mg_levels_alloc(MG2DContext *ctx, size_t domain_size);
+
 int mg2d_solve(MG2DContext *ctx)
 {
     MG2DInternal *priv = ctx->priv;
-    MG2DLevel    *root = priv->root;
-    EGSContext *s_root = root->solver;
+    MG2DLevel    *root;
+    EGSContext *s_root;
     int64_t time_start;
     double res_orig, res_prev, res_cur;
     int ret;
 
+    if (!priv->root) {
+        ret = mg_levels_alloc(ctx, ctx->domain_size);
+        if (ret < 0)
+            return ret;
+    }
+
     if (!priv->tp) {
         ret = threadpool_init(ctx);
         if (ret < 0)
             return ret;
     }
 
+    root   = priv->root;
+    s_root = root->solver;
+
     time_start = gettime();
 
     ret = mg_levels_init(ctx);
@@ -648,7 +657,7 @@ static int mg_levels_alloc(MG2DContext *ctx, size_t domain_size)
     dst       = &priv->root;
     next_size = domain_size;
 
-    for (int depth = 0; depth < LEVELS_MAX; depth++) {
+    for (int depth = 0; depth < ctx->max_levels; depth++) {
         enum EGSType cur_type;
         size_t cur_size = next_size;
 
@@ -662,7 +671,7 @@ static int mg_levels_alloc(MG2DContext *ctx, size_t domain_size)
         } else
             next_size = (cur_size >> 1) + 1;
 
-        cur_type = (depth == LEVELS_MAX - 1 || cur_size < 9) ? EGS_SOLVER_EXACT : EGS_SOLVER_RELAXATION;
+        cur_type = (cur_size <= ctx->max_exact_size) ? EGS_SOLVER_EXACT : EGS_SOLVER_RELAXATION;
 
         *dst = mg_level_alloc(cur_type, cur_size);
         if (!*dst)
@@ -735,12 +744,10 @@ MG2DContext *mg2d_solver_alloc(size_t domain_size)
     }
     ctx->diff_coeffs_stride = domain_size;
 
-    ret = mg_levels_alloc(ctx, domain_size);
-    if (ret < 0)
-        goto fail;
-
     ctx->domain_size = domain_size;
 
+    ctx->max_levels    = 16;
+    ctx->max_exact_size = 5;
     ctx->maxiter       = 16;
     ctx->tol           = 1e-12;
     ctx->nb_cycles     = 1;
diff --git a/mg2d.h b/mg2d.h
index 234d8cf..6452526 100644
--- a/mg2d.h
+++ b/mg2d.h
@@ -148,6 +148,18 @@ typedef struct MG2DContext {
      * effect when log_callback is overridden.
      */
     enum MG2DLogLevel log_level;
+
+    /**
+     * Maximum number of refinement levels. May only be modified by the caller
+     * before the first call to mg2d_solve().
+     */
+    unsigned int max_levels;
+
+    /**
+     * Maximum size (along one dimensions) of a refinement level on which an
+     * exact solve is performed.
+     */
+    size_t max_exact_size;
 } MG2DContext;
 
 /**
-- 
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