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perf: avoid redundant permute+cont in non-interleaved RoPE #2102

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Merged
leejet merged 3 commits into from
Oct 6, 2026
Merged

perf: avoid redundant permute+cont in non-interleaved RoPE #2102

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e56d4d4
perf: avoid redundant permute+cont in non-interleaved RoPE
daniandtheweb Oct 4, 2026
21f49df
format code
leejet Oct 6, 2026
bcdffe8
simplify RoPE control flow and unify variable naming
leejet Oct 6, 2026
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17 changes: 11 additions & 6 deletions src/model/common/rope.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1082,8 +1082,16 @@ namespace Rope {
x = ggml_reshape_4d(ctx, x, 2, d_head / 2, L, n_head * N); // [N * n_head, L, d_head/2, 2]
x = ggml_cont(ctx, ggml_permute(ctx, x, 3, 0, 1, 2)); // [2, N * n_head, L, d_head/2]
} else {
x = ggml_reshape_4d(ctx, x, d_head / 2, 2, L, n_head * N); // [N * n_head, L, 2, d_head/2]
x = ggml_cont(ctx, ggml_ext_torch_permute(ctx, x, 0, 2, 3, 1)); // [2, N * n_head, L, d_head/2]
auto x_0 = ggml_view_3d(ctx, x, d_head / 2, L, n_head * N, x->nb[1], x->nb[2], 0);
auto x_1 = ggml_view_3d(ctx, x, d_head / 2, L, n_head * N, x->nb[1], x->nb[2], (d_head / 2) * x->nb[0]);

auto pe_2 = ggml_cont(ctx, ggml_permute(ctx, pe, 2, 3, 0, 1));
auto cos = ggml_view_2d(ctx, pe_2, d_head / 2, L, pe_2->nb[1], 0);
auto sin = ggml_view_2d(ctx, pe_2, d_head / 2, L, pe_2->nb[1], pe_2->nb[3]);

auto part_0 = ggml_sub(ctx, ggml_mul(ctx, x_0, cos), ggml_mul(ctx, x_1, sin));
auto part_1 = ggml_add(ctx, ggml_mul(ctx, x_0, sin), ggml_mul(ctx, x_1, cos));
return ggml_concat(ctx, part_0, part_1, 0);
}

int64_t offset = x->nb[2] * x->ne[2];
Expand All @@ -1101,10 +1109,7 @@ namespace Rope {
auto pe_1 = ggml_view_3d(ctx, pe, pe->ne[0], pe->ne[1], pe->ne[2], pe->nb[1], pe->nb[2], offset * 1); // [L, d_head/2, 2]

auto x_out = ggml_add_inplace(ctx, ggml_mul(ctx, x_0, pe_0), ggml_mul(ctx, x_1, pe_1)); // [N * n_head, L, d_head/2, 2]
if (!rope_interleaved) {
x_out = ggml_cont(ctx, ggml_permute(ctx, x_out, 1, 0, 2, 3)); // [N * n_head, L, x, d_head/2]
}
x_out = ggml_reshape_3d(ctx, x_out, d_head, L, n_head * N); // [N*n_head, L, d_head]
x_out = ggml_reshape_3d(ctx, x_out, d_head, L, n_head * N); // [N*n_head, L, d_head]
return x_out;
}

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