From 88032f46b1cf496670fb029dfcfa071ea2e31e02 Mon Sep 17 00:00:00 2001
From: Saba Fallah <10401143+sfallah@users.noreply.github.com>
Date: Thu, 20 Nov 2025 10:07:54 +0100
Subject: [PATCH] window partitioning using standard ggml ops

---
 tools/mtmd/clip.cpp | 50 +++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 46 insertions(+), 4 deletions(-)

diff --git a/tools/mtmd/clip.cpp b/tools/mtmd/clip.cpp
index 797f921f50..40b60cbfd5 100644
--- a/tools/mtmd/clip.cpp
+++ b/tools/mtmd/clip.cpp
@@ -690,7 +690,8 @@ struct clip_graph {
             if (hparams.is_global_attn(il) == false) {
                 // local attention layer - apply window partition
                 // ref: https://github.com/facebookresearch/segment-anything/blob/main/segment_anything/modeling/image_encoder.py#L169-L172
-                cur = ggml_win_part(ctx0, cur, 14);
+                //cur = ggml_win_part(ctx0, cur, 14);
+                cur = window_partition(ctx0, cur, 14);
             }
 
             const int64_t W = cur->ne[1];
@@ -762,7 +763,7 @@ struct clip_graph {
 
             if (hparams.is_global_attn(il) == false) {
                 // local attention layer - reverse window partition
-                cur = ggml_win_unpart(ctx0, cur, w0, h0, 14);
+                cur = window_unpartition(ctx0, cur, w0, h0, 14);
             }
 
             // re-add the layer input, e.g., residual
@@ -865,9 +866,10 @@ struct clip_graph {
 
         // 1) global_features: [n_dim, h*w] -> [n_dim, w, h] -> [h, w, n_dim]
         ggml_tensor * t = ggml_reshape_4d(ctx0, global_features, 1280, 64, 64, 1);  // (n_dim, w, h)
-        t               = ggml_permute(ctx0, t, 2, 1, 0, 3); // (h, w, n_dim)
-        ggml_tensor * nl = ggml_permute(ctx0, model.image_newline, 2, 1, 0, 3);
+        t               = ggml_cont(ctx0, ggml_permute(ctx0, t, 2, 1, 0, 3)); // (h, w, n_dim)
+        ggml_tensor * nl = ggml_cont(ctx0,ggml_permute(ctx0, model.image_newline, 2, 1, 0, 3));
         nl = ggml_repeat_4d(ctx0, nl, 64, 1, 1280, 1); // n_pos rows
+        nl = ggml_cont(ctx0, nl);
 
 
         // 2) image_newline: [n_dim] -> [1, 1, n_dim] -> repeat to [h, 1, n_dim]
@@ -2464,6 +2466,46 @@ private:
         return inpL;
     }
 
+    static ggml_tensor* window_partition(ggml_context* ctx, ggml_tensor* x, int window) {
+        auto [c, w, h, b] = x->ne;
+        // same as
+        // x = ggml_win_part(m, x, window);
+        // x = ggml_reshape_3d(m, x, c, window * window, x->ne[3]);
+
+        int64_t px = (window - w % window) % window;
+        int64_t py = (window - h % window) % window;
+        int64_t npw = (w + px) / window;
+        int64_t nph = (h + py) / window;
+
+        if (px > 0 || py > 0) {
+            x = ggml_pad(ctx, x, 0, int(px), int(py), 0);
+        }
+        x = ggml_reshape_4d(ctx, x, c * window, npw, window, nph * b);
+        x = ggml_cont(ctx, ggml_permute(ctx, x, 0, 2, 1, 3));
+        x = ggml_reshape_4d(ctx, x, c, window ,window, npw * nph * b);
+        return x;
+    }
+
+    static ggml_tensor* window_unpartition(ggml_context* m, ggml_tensor* x, int w, int h, int window) {
+        int64_t c = x->ne[0];
+        // same as
+        // x = ggml_reshape_4d(m, x, c, window, window, x->ne[2]);
+        // x = ggml_win_unpart(m, x, w, h, window);
+
+        int64_t px = (window - w % window) % window;
+        int64_t py = (window - h % window) % window;
+        int64_t npw = (w + px) / window;
+        int64_t nph = (h + py) / window;
+
+        int64_t b = x->ne[3] / (npw * nph);
+        x = ggml_reshape_4d(m, x, c * window, window, npw, nph * b);
+        x = ggml_cont(m, ggml_permute(m, x, 0, 2, 1, 3));
+        x = ggml_reshape_4d(m, x, c, w + px, h + py, b);
+        x = ggml_view_4d(m, x, x->ne[0], w, h, x->ne[3], x->nb[1], x->nb[2], x->nb[3], 0);
+        x = ggml_cont(m, x);
+        return x;
+    }
+
     // build the input after conv2d (inp_raw --> patches)
     // returns tensor with shape [n_embd, n_patches]
     ggml_tensor * build_enc_inp(ggml_tensor * inp_raw,