clip : fix pixtral on some GPU backends

examples/llava/clip.cpp

@@ -556,15 +556,14 @@ static ggml_cgraph * clip_image_build_graph_siglip(clip_ctx * ctx, const clip_im
 }
 
 // implementation of the 2D RoPE without adding a new op in ggml
+// this is not efficient (use double the memory), but works on all backends
 static ggml_tensor * build_rope_2d(
-    ggml_cgraph * gf,
     ggml_context * ctx0,
     ggml_tensor * cur,
     ggml_tensor * pos_h,
     ggml_tensor * pos_w,
     const float freq_base
 ) {
-    ggml_tensor * tmp;
     const int64_t n_dim  = cur->ne[0];
     const int64_t n_head = cur->ne[1];
     const int64_t n_pos  = cur->ne[2];
@@ -573,18 +572,24 @@ static ggml_tensor * build_rope_2d(
     // we will have a list of 4 inv_freq: 1e-0, 1e-1, 1e-2, 1e-3
     // first half of cur will use 1e-0, 1e-2 (even)
     // second half of cur will use 1e-1, 1e-3 (odd)
-    //
-    // for the first half, the trick here is to rotate n_dim/2, so inv_freq will be even
+    // the trick here is to rotate just half of n_dim, so inv_freq will automatically be even
     //  ^ don't ask me why, it's math! -2(2i) / n_dim == -2i / (n_dim/2)
     // then for the second half, we use freq_scale to shift the inv_freq
     //  ^ why? replace (2i) with (2i+1) in the above equation
     const float freq_scale_odd = std::pow(freq_base, (float)-2/n_dim);
 
     // first half
+    ggml_tensor * first;
     {
-        cur = ggml_rope_ext_inplace(
+        first = ggml_view_3d(ctx0, cur,
+            n_dim/2, n_head, n_pos,
+            ggml_row_size(cur->type, n_dim),
+            ggml_row_size(cur->type, n_dim*n_head),
+            0);
+        // first = ggml_cont(ctx0, first);
+        first = ggml_rope_ext(
             ctx0,
-            cur,
+            first,
             pos_h,      // positions
             nullptr,    // freq factors
             n_dim/2,    // n_dims
@@ -593,27 +598,28 @@ static ggml_tensor * build_rope_2d(
         );
     }
 
-    // second half
+    // second half (write to tmp)
+    ggml_tensor * second = cur;
     {
-        tmp = ggml_view_3d(ctx0, cur,
+        second = ggml_view_3d(ctx0, cur,
             n_dim/2, n_head, n_pos,
             ggml_row_size(cur->type, n_dim),
             ggml_row_size(cur->type, n_dim*n_head),
             n_dim/2 * ggml_element_size(cur));
-        tmp = ggml_rope_ext_inplace(
+        second = ggml_cont(ctx0, second); // copy, because ggml_rope don't play well with non-contiguous tensors
+        second = ggml_rope_ext(
             ctx0,
-            tmp,
+            second,
             pos_w,      // positions
             nullptr,    // freq factors
             n_dim/2,    // n_dims
             0, 0, freq_base,
             freq_scale_odd,
             0.0f, 1.0f, 0.0f, 0.0f
         );
-        // calculate inplace (modify cur directly)
-        ggml_build_forward_expand(gf, tmp);
     }
 
+    cur = ggml_concat(ctx0, first, second, 0);
     return cur;
 }
 
@@ -682,13 +688,13 @@ static ggml_cgraph * clip_image_build_graph_pixtral(clip_ctx * ctx, const clip_i
             struct ggml_tensor * Q = ggml_mul_mat(ctx0, model.layers[il].q_w, cur);
 
             Q = ggml_reshape_3d(ctx0, Q, d_head, n_head, num_patches);
-            Q = build_rope_2d(gf, ctx0, Q, pos_h, pos_w, hparams.rope_theta);
+            Q = build_rope_2d(ctx0, Q, pos_h, pos_w, hparams.rope_theta);
             Q = ggml_cont(ctx0, ggml_permute(ctx0, Q, 0, 2, 1, 3));
 
             struct ggml_tensor * K = ggml_mul_mat(ctx0, model.layers[il].k_w, cur);
 
             K = ggml_reshape_3d(ctx0, K, d_head, n_head, num_patches);
-            K = build_rope_2d(gf, ctx0, K, pos_h, pos_w, hparams.rope_theta);
+            K = build_rope_2d(ctx0, K, pos_h, pos_w, hparams.rope_theta);
             K = ggml_cont(ctx0, ggml_permute(ctx0, K, 0, 2, 1, 3));
 
             struct ggml_tensor * V = ggml_mul_mat(ctx0, model.layers[il].v_w, cur);