Lumpiasty/llama.cpp
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mtmd: use ggml_rope_set_offset (#27521)

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* mtmd: use ggml_rope_set_offset

* add comment
This commit is contained in:
Xuan-Son Nguyen
2026-08-22 16:33:47 +02:00
committed by GitHub
parent d9f918d2d0
commit b21e4de745
4 changed files with 62 additions and 104 deletions
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tools/mtmd/clip.cpp
+23 -43
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@@ -819,8 +819,6 @@ ggml_tensor * clip_graph::build_attn(
}
// 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
// TODO: there was a more efficient which relies on ggml_view and ggml_rope_ext_inplace, but the rope inplace does not work well with non-contiguous tensors ; we should fix that and revert back to the original implementation in https://github.com/ggml-org/llama.cpp/pull/13065
ggml_tensor * clip_graph::build_rope_2d(
ggml_context * ctx0,
ggml_tensor * cur,
@@ -829,9 +827,7 @@ ggml_tensor * clip_graph::build_rope_2d(
const float freq_base,
const bool interleave_freq
) {
const int64_t n_dim = cur->ne[0];
const int64_t n_head = cur->ne[1];
const int64_t n_pos = cur->ne[2];
const int64_t n_dim = cur->ne[0];
// for example, if we have cur tensor of shape (n_dim=8, n_head, n_pos)
// we will have a list of 4 inv_freq: 1e-0, 1e-1, 1e-2, 1e-3
@@ -845,46 +841,30 @@ ggml_tensor * clip_graph::build_rope_2d(
? std::pow(freq_base, (float)-2/n_dim)
: 1.0;
// first half
ggml_tensor * first;
{
first = ggml_view_3d(ctx0, cur,
n_dim/2, n_head, n_pos,
cur->nb[1],
cur->nb[2],
0);
first = ggml_rope_ext(
ctx0,
first,
pos_a, // positions
nullptr, // freq factors
n_dim/2, // n_dims
0, 0, freq_base,
1.0f, 0.0f, 1.0f, 0.0f, 0.0f
);
}
// first half, dims [0, n_dim/2)
cur = ggml_rope_ext(
ctx0,
cur,
pos_a, // positions
nullptr, // freq factors
n_dim/2, // n_dims
0, 0, freq_base,
1.0f, 0.0f, 1.0f, 0.0f, 0.0f
);
// second half
ggml_tensor * second;
{
second = ggml_view_3d(ctx0, cur,
n_dim/2, n_head, n_pos,
cur->nb[1],
cur->nb[2],
n_dim/2 * ggml_element_size(cur));
second = ggml_rope_ext(
ctx0,
second,
pos_b, // positions
nullptr, // freq factors
n_dim/2, // n_dims
0, 0, freq_base,
freq_scale_odd,
0.0f, 1.0f, 0.0f, 0.0f
);
}
// second half, dims [n_dim/2, n_dim)
cur = ggml_rope_ext(
ctx0,
cur,
pos_b, // positions
nullptr, // freq factors
n_dim/2, // n_dims
0, 0, freq_base,
freq_scale_odd,
0.0f, 1.0f, 0.0f, 0.0f
);
cur = ggml_rope_set_offset(cur, n_dim/2);
cur = ggml_concat(ctx0, first, second, 0);
return cur;
}