Commit 019bcfc for stable-diffusion.cpp

commit 019bcfc0ae3bc1a5bf37b93c65727dee149a9c31
Author: mcxu <192633541+shawn-mengchen-xu@users.noreply.github.com>
Date:   Tue Oct 6 03:23:41 2026 -0700

    fix: correct non-circular tile placement and blending (#2088)

diff --git a/src/runtime/tiling.cpp b/src/runtime/tiling.cpp
index 38ea4c2..e64e152 100644
--- a/src/runtime/tiling.cpp
+++ b/src/runtime/tiling.cpp
@@ -8,6 +8,32 @@
 #include "core/util.h"
 #include "ggml.h"

+static int sd_tiling_calc_num_tiles(int dimension, int tile_size, float target_overlap_factor) {
+    if (dimension <= tile_size) {
+        return 1;
+    } else if (dimension < 2 * tile_size) {
+        return 2;
+    } else if (dimension == 2 * tile_size) {
+        return 3;
+    } else {
+        float target_num_tiles = 1.0f + (dimension - tile_size) / ((1.0f - target_overlap_factor) * tile_size);
+        int num_tiles_lower    = static_cast<int>(std::floor(target_num_tiles));
+        int num_tiles_upper    = static_cast<int>(std::ceil(target_num_tiles));
+        int num_tiles_min      = 1 + (dimension - 2) / (tile_size - 1);  // positive adjacent overlap
+        int num_tiles_max      = 2 * dimension / tile_size - 1;          // no triple overlap under Bresenham placement
+        num_tiles_lower        = std::clamp(num_tiles_lower, num_tiles_min, num_tiles_max);
+        num_tiles_upper        = std::clamp(num_tiles_upper, num_tiles_min, num_tiles_max);
+        auto overlap_error     = [target_num_tiles](int num_tiles) -> float {
+            return std::abs(1.0f / (num_tiles - 1.0f) - 1.0f / (target_num_tiles - 1.0f));
+        };  // (dimension - tile_size) / tile_size factors out
+        return (overlap_error(num_tiles_upper) < overlap_error(num_tiles_lower)) ? num_tiles_upper : num_tiles_lower;  // use lower if tie
+    }
+}
+
+static float sd_tiling_calc_average_stride_factor(int dimension, int tile_size, int num_tiles) {
+    return static_cast<float>(dimension - tile_size) / static_cast<float>(tile_size * (num_tiles - 1));
+}
+
 static void sd_tiling_calc_tiles(int& num_tiles_dim,
                                  float& tile_overlap_factor_dim,
                                  int small_dim,
@@ -32,29 +58,9 @@ static void sd_tiling_calc_tiles(int& num_tiles_dim,
             num_tiles_dim++;
             tile_overlap_factor_dim = 0.5;
         }
-
-        return;
-    }
-    // else, non-circular means the last and first tile are not overlapping
-
-    num_tiles_dim     = (small_dim - tile_overlap) / non_tile_overlap;
-    int overshoot_dim = ((num_tiles_dim + 1) * non_tile_overlap + tile_overlap) % small_dim;
-
-    if ((overshoot_dim != non_tile_overlap) && (overshoot_dim <= num_tiles_dim * (tile_size / 2 - tile_overlap))) {
-        // if tiles don't fit perfectly using the desired overlap
-        // and there is enough room to squeeze an extra tile without overlap becoming >0.5
-        num_tiles_dim++;
-    }
-
-    tile_overlap_factor_dim = (float)(tile_size * num_tiles_dim - small_dim) / (float)(tile_size * (num_tiles_dim - 1));
-    if (num_tiles_dim <= 2) {
-        if (small_dim <= tile_size) {
-            num_tiles_dim           = 1;
-            tile_overlap_factor_dim = 0;
-        } else {
-            num_tiles_dim           = 2;
-            tile_overlap_factor_dim = (2 * tile_size - small_dim) / (float)tile_size;
-        }
+    } else {
+        num_tiles_dim           = sd_tiling_calc_num_tiles(small_dim, tile_size, tile_overlap_factor);
+        tile_overlap_factor_dim = (num_tiles_dim == 1) ? 0 : (1.0f - sd_tiling_calc_average_stride_factor(small_dim, tile_size, num_tiles_dim));
     }
 }

@@ -138,6 +144,59 @@ static void sd_tensor_merge_2d(const sd::Tensor<float>& input,
     }
 }

+static void sd_tensor_merge_2d_non_circular(const sd::Tensor<float>& input,
+                                            sd::Tensor<float>* output,
+                                            int x,
+                                            int y,
+                                            int overlap_left,
+                                            int overlap_right,
+                                            int overlap_top,
+                                            int overlap_bottom) {
+    GGML_ASSERT(output != nullptr);
+
+    int64_t in_width    = input.shape()[0];
+    int64_t in_height   = input.shape()[1];
+    int64_t out_width   = output->shape()[0];
+    int64_t out_height  = output->shape()[1];
+    int64_t in_size     = sd_tensor_plane_size(input);
+    int64_t out_size    = sd_tensor_plane_size(*output);
+    int64_t plane_count = input.numel() / in_size;
+
+    GGML_ASSERT(output->numel() == plane_count * out_size);
+    GGML_ASSERT(x >= 0 && y >= 0);
+    GGML_ASSERT(x + in_width <= out_width);
+    GGML_ASSERT(y + in_height <= out_height);
+    GGML_ASSERT(overlap_left >= 0 && overlap_right >= 0);
+    GGML_ASSERT(overlap_top >= 0 && overlap_bottom >= 0);
+
+    auto smootherstep_f32 = [](const float x) -> float {
+        return x * x * x * (x * (6.0f * x - 15.0f) + 10.0f);
+    };
+    for (int64_t plane = 0; plane < plane_count; ++plane) {
+        for (int iy = 0; iy < in_height; ++iy) {
+            float y_f = 1.0f;
+            if (iy < overlap_top) {
+                y_f = static_cast<float>(iy) / overlap_top;
+            }
+            if (iy >= in_height - overlap_bottom) {
+                y_f = static_cast<float>(in_height - iy) / overlap_bottom;
+            }
+            const float y_weight = smootherstep_f32(std::clamp(y_f, 0.0f, 1.0f));
+            for (int ix = 0; ix < in_width; ++ix) {
+                float x_f = 1.0f;
+                if (ix < overlap_left) {
+                    x_f = static_cast<float>(ix) / overlap_left;
+                }
+                if (ix >= in_width - overlap_right) {
+                    x_f = static_cast<float>(in_width - ix) / overlap_right;
+                }
+                float x_weight = smootherstep_f32(std::clamp(x_f, 0.0f, 1.0f));
+                (*output)[plane * out_size + out_width * (y + iy) + (x + ix)] += x_weight * y_weight * input[plane * in_size + in_width * iy + ix];
+            }
+        }
+    }
+}
+
 sd::Tensor<float> process_tiles_2d(const sd::Tensor<float>& input,
                                    int output_width,
                                    int output_height,
@@ -158,13 +217,11 @@ sd::Tensor<float> process_tiles_2d(const sd::Tensor<float>& input,
     GGML_ASSERT(((input_width / output_width) == scale) ||
                 ((output_width / input_width) == scale));

-    int small_width  = output_width;
-    int small_height = output_height;
-    bool decode      = output_width > input_width;
-    if (decode) {
-        small_width  = input_width;
-        small_height = input_height;
-    }
+    bool decode      = output_width > input_width;  // scale up
+    int small_width  = decode ? input_width : output_width;
+    int small_height = decode ? input_height : output_height;
+    int scale_in     = decode ? 1 : scale;
+    int scale_out    = decode ? scale : 1;

     int num_tiles_x;
     float tile_overlap_factor_x;
@@ -174,28 +231,15 @@ sd::Tensor<float> process_tiles_2d(const sd::Tensor<float>& input,
     float tile_overlap_factor_y;
     sd_tiling_calc_tiles(num_tiles_y, tile_overlap_factor_y, small_height, p_tile_size_h, tile_overlap_factor, circular_y);

-    int tile_overlap_x     = static_cast<int32_t>(p_tile_size_w * tile_overlap_factor_x);
-    int non_tile_overlap_x = p_tile_size_w - tile_overlap_x;
-    int tile_overlap_y     = static_cast<int32_t>(p_tile_size_h * tile_overlap_factor_y);
-    int non_tile_overlap_y = p_tile_size_h - tile_overlap_y;
-    int tile_size_w        = p_tile_size_w < small_width ? p_tile_size_w : small_width;
-    int tile_size_h        = p_tile_size_h < small_height ? p_tile_size_h : small_height;
-    int input_tile_size_w  = tile_size_w;
-    int input_tile_size_h  = tile_size_h;
-    int output_tile_size_w = tile_size_w;
-    int output_tile_size_h = tile_size_h;
-    if (decode) {
-        output_tile_size_w *= scale;
-        output_tile_size_h *= scale;
-    } else {
-        input_tile_size_w *= scale;
-        input_tile_size_h *= scale;
-    }
+    int tile_width         = std::min(p_tile_size_w, small_width);
+    int tile_height        = std::min(p_tile_size_h, small_height);
+    int input_tile_width   = tile_width * scale_in;
+    int input_tile_height  = tile_height * scale_in;
+    int output_tile_width  = tile_width * scale_out;
+    int output_tile_height = tile_height * scale_out;

     int num_tiles   = num_tiles_x * num_tiles_y;
     int tile_count  = 1;
-    bool last_y     = false;
-    bool last_x     = false;
     float last_time = 0.0f;
     if (!silent) {
         LOG_VERBOSE("num tiles : %d, %d ", num_tiles_x, num_tiles_y);
@@ -203,60 +247,129 @@ sd::Tensor<float> process_tiles_2d(const sd::Tensor<float>& input,
         LOG_VERBOSE("processing %i tiles", num_tiles);
         pretty_progress(0, num_tiles, 0.0f);
     }
-    for (int y = 0; y < small_height && !last_y; y += non_tile_overlap_y) {
-        int dy = 0;
-        if (!circular_y && y + tile_size_h >= small_height) {
-            int original_y = y;
-            y              = small_height - tile_size_h;
-            dy             = original_y - y;
-            if (decode) {
-                dy *= scale;
-            }
-            last_y = true;
-        }
-        for (int x = 0; x < small_width && !last_x; x += non_tile_overlap_x) {
-            int dx = 0;
-            if (!circular_x && x + tile_size_w >= small_width) {
-                int original_x = x;
-                x              = small_width - tile_size_w;
-                dx             = original_x - x;
+    if (circular_x || circular_y) {
+        int tile_overlap_x     = static_cast<int32_t>(p_tile_size_w * tile_overlap_factor_x);
+        int non_tile_overlap_x = p_tile_size_w - tile_overlap_x;
+        int tile_overlap_y     = static_cast<int32_t>(p_tile_size_h * tile_overlap_factor_y);
+        int non_tile_overlap_y = p_tile_size_h - tile_overlap_y;
+
+        bool last_y = false;
+        bool last_x = false;
+
+        for (int y = 0; y < small_height && !last_y; y += non_tile_overlap_y) {
+            int dy = 0;
+            if (!circular_y && y + tile_height >= small_height) {
+                int original_y = y;
+                y              = small_height - tile_height;
+                dy             = original_y - y;
                 if (decode) {
-                    dx *= scale;
+                    dy *= scale;
                 }
-                last_x = true;
+                last_y = true;
             }
+            for (int x = 0; x < small_width && !last_x; x += non_tile_overlap_x) {
+                int dx = 0;
+                if (!circular_x && x + tile_width >= small_width) {
+                    int original_x = x;
+                    x              = small_width - tile_width;
+                    dx             = original_x - x;
+                    if (decode) {
+                        dx *= scale;
+                    }
+                    last_x = true;
+                }

-            int x_in  = decode ? x : scale * x;
-            int y_in  = decode ? y : scale * y;
-            int x_out = decode ? x * scale : x;
-            int y_out = decode ? y * scale : y;
+                int x_in  = decode ? x : scale * x;
+                int y_in  = decode ? y : scale * y;
+                int x_out = decode ? x * scale : x;
+                int y_out = decode ? y * scale : y;

-            int overlap_x_out = decode ? tile_overlap_x * scale : tile_overlap_x;
-            int overlap_y_out = decode ? tile_overlap_y * scale : tile_overlap_y;
+                int overlap_x_out = decode ? tile_overlap_x * scale : tile_overlap_x;
+                int overlap_y_out = decode ? tile_overlap_y * scale : tile_overlap_y;

-            int64_t t1       = ggml_time_ms();
-            auto input_tile  = sd_tensor_split_2d(input, input_tile_size_w, input_tile_size_h, x_in, y_in);
-            auto output_tile = on_processing(input_tile);
-            if (output_tile.empty()) {
-                return {};
+                int64_t t1       = ggml_time_ms();
+                auto input_tile  = sd_tensor_split_2d(input, input_tile_width, input_tile_height, x_in, y_in);
+                auto output_tile = on_processing(input_tile);
+                if (output_tile.empty()) {
+                    return {};
+                }
+                GGML_ASSERT(output_tile.shape()[0] == output_tile_width && output_tile.shape()[1] == output_tile_height);
+                if (output.empty()) {
+                    std::vector<int64_t> output_shape = output_tile.shape();
+                    output_shape[0]                   = output_width;
+                    output_shape[1]                   = output_height;
+                    output                            = sd::Tensor<float>::zeros(std::move(output_shape));
+                }
+                sd_tensor_merge_2d(output_tile, &output, x_out, y_out, overlap_x_out, overlap_y_out, circular_x, circular_y, dx, dy);
+
+                if (!silent) {
+                    int64_t t2 = ggml_time_ms();
+                    last_time  = (t2 - t1) / 1000.0f;
+                    pretty_progress(tile_count, num_tiles, last_time);
+                }
+                tile_count++;
             }
-            GGML_ASSERT(output_tile.shape()[0] == output_tile_size_w && output_tile.shape()[1] == output_tile_size_h);
-            if (output.empty()) {
-                std::vector<int64_t> output_shape = output_tile.shape();
-                output_shape[0]                   = output_width;
-                output_shape[1]                   = output_height;
-                output                            = sd::Tensor<float>::zeros(std::move(output_shape));
+            last_x = false;
+        }
+    } else {
+        for (int j = 0; j < num_tiles_y; ++j) {
+            int y              = 0;
+            int overlap_top    = 0;
+            int overlap_bottom = 0;
+            if (num_tiles_y > 1) {
+                y = j * (small_height - tile_height) / (num_tiles_y - 1);
+                if (j > 0) {
+                    int y_prev  = (j - 1) * (small_height - tile_height) / (num_tiles_y - 1);
+                    overlap_top = y_prev + tile_height - y;
+                }
+                if (j < num_tiles_y - 1) {
+                    int y_next     = (j + 1) * (small_height - tile_height) / (num_tiles_y - 1);
+                    overlap_bottom = y + tile_height - y_next;
+                }
             }
-            sd_tensor_merge_2d(output_tile, &output, x_out, y_out, overlap_x_out, overlap_y_out, circular_x, circular_y, dx, dy);
+            for (int i = 0; i < num_tiles_x; ++i) {
+                int x             = 0;
+                int overlap_left  = 0;
+                int overlap_right = 0;
+                if (num_tiles_x > 1) {
+                    x = i * (small_width - tile_width) / (num_tiles_x - 1);
+                    if (i > 0) {
+                        int x_prev   = (i - 1) * (small_width - tile_width) / (num_tiles_x - 1);
+                        overlap_left = x_prev + tile_width - x;
+                    }
+                    if (i < num_tiles_x - 1) {
+                        int x_next    = (i + 1) * (small_width - tile_width) / (num_tiles_x - 1);
+                        overlap_right = x + tile_width - x_next;
+                    }
+                }

-            if (!silent) {
-                int64_t t2 = ggml_time_ms();
-                last_time  = (t2 - t1) / 1000.0f;
-                pretty_progress(tile_count, num_tiles, last_time);
+                int64_t t1       = ggml_time_ms();
+                auto input_tile  = sd_tensor_split_2d(input, input_tile_width, input_tile_height, x * scale_in, y * scale_in);
+                auto output_tile = on_processing(input_tile);
+                if (output_tile.empty()) {
+                    return {};
+                }
+                GGML_ASSERT(output_tile.shape()[0] == output_tile_width && output_tile.shape()[1] == output_tile_height);
+                if (output.empty()) {
+                    std::vector<int64_t> output_shape = output_tile.shape();
+                    output_shape[0]                   = output_width;
+                    output_shape[1]                   = output_height;
+                    output                            = sd::Tensor<float>::zeros(std::move(output_shape));
+                }
+                sd_tensor_merge_2d_non_circular(
+                    output_tile, &output,
+                    x * scale_out, y * scale_out,
+                    overlap_left * scale_out,
+                    overlap_right * scale_out,
+                    overlap_top * scale_out,
+                    overlap_bottom * scale_out);
+                if (!silent) {
+                    last_time = (ggml_time_ms() - t1) / 1000.0f;
+                    pretty_progress(tile_count, num_tiles, last_time);
+                }
+                tile_count++;
             }
-            tile_count++;
         }
-        last_x = false;
     }
     if (!silent && tile_count < num_tiles) {
         pretty_progress(num_tiles, num_tiles, last_time);