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

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

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60 changes: 36 additions & 24 deletions src/model/common/rope.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1073,39 +1073,51 @@ namespace Rope {
bool rope_interleaved = true) {
// x: [N, L, n_head, d_head]
// pe: [L, d_head/2, 2, 2], [[cos, -sin], [sin, cos]]
//
// Returns [N * n_head, L, d_head].
int64_t d_head = x->ne[0];
int64_t n_head = x->ne[1];
int64_t L = x->ne[2];
int64_t N = x->ne[3];
x = ggml_cont(ctx, ggml_permute(ctx, x, 0, 2, 1, 3)); // [N, n_head, L, d_head]

x = ggml_cont(ctx, ggml_permute(ctx, x, 0, 2, 1, 3)); // [N, n_head, L, d_head]

if (rope_interleaved) {
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]
}

int64_t offset = x->nb[2] * x->ne[2];
auto x_0 = ggml_view_3d(ctx, x, x->ne[0], x->ne[1], x->ne[2], x->nb[1], x->nb[2], offset * 0); // [N * n_head, L, d_head/2]
auto x_1 = ggml_view_3d(ctx, x, x->ne[0], x->ne[1], x->ne[2], x->nb[1], x->nb[2], offset * 1); // [N * n_head, L, d_head/2]
x_0 = ggml_reshape_4d(ctx, x_0, 1, x_0->ne[0], x_0->ne[1], x_0->ne[2]); // [N * n_head, L, d_head/2, 1]
x_1 = ggml_reshape_4d(ctx, x_1, 1, x_1->ne[0], x_1->ne[1], x_1->ne[2]); // [N * n_head, L, d_head/2, 1]
auto temp_x = ggml_new_tensor_4d(ctx, x_0->type, 2, x_0->ne[1], x_0->ne[2], x_0->ne[3]);
x_0 = ggml_repeat(ctx, x_0, temp_x); // [N * n_head, L, d_head/2, 2]
x_1 = ggml_repeat(ctx, x_1, temp_x); // [N * n_head, L, d_head/2, 2]

pe = ggml_cont(ctx, ggml_permute(ctx, pe, 3, 0, 1, 2)); // [2, L, d_head/2, 2]
offset = pe->nb[2] * pe->ne[2];
auto pe_0 = ggml_view_3d(ctx, pe, pe->ne[0], pe->ne[1], pe->ne[2], pe->nb[1], pe->nb[2], offset * 0); // [L, d_head/2, 2]
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]
int64_t offset = x->nb[2] * x->ne[2];
auto x_0 = ggml_view_3d(ctx, x, x->ne[0], x->ne[1], x->ne[2], x->nb[1], x->nb[2], offset * 0); // [N * n_head, L, d_head/2]
auto x_1 = ggml_view_3d(ctx, x, x->ne[0], x->ne[1], x->ne[2], x->nb[1], x->nb[2], offset * 1); // [N * n_head, L, d_head/2]
x_0 = ggml_reshape_4d(ctx, x_0, 1, x_0->ne[0], x_0->ne[1], x_0->ne[2]); // [N * n_head, L, d_head/2, 1]
x_1 = ggml_reshape_4d(ctx, x_1, 1, x_1->ne[0], x_1->ne[1], x_1->ne[2]); // [N * n_head, L, d_head/2, 1]
auto temp_x = ggml_new_tensor_4d(ctx, x_0->type, 2, x_0->ne[1], x_0->ne[2], x_0->ne[3]);
x_0 = ggml_repeat(ctx, x_0, temp_x); // [N * n_head, L, d_head/2, 2]
x_1 = ggml_repeat(ctx, x_1, temp_x); // [N * n_head, L, d_head/2, 2]

pe = ggml_cont(ctx, ggml_permute(ctx, pe, 3, 0, 1, 2)); // [2, L, d_head/2, 2]
offset = pe->nb[2] * pe->ne[2];
auto pe_0 = ggml_view_3d(ctx, pe, pe->ne[0], pe->ne[1], pe->ne[2], pe->nb[1], pe->nb[2], offset * 0); // [L, d_head/2, 2]
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]
x_out = ggml_reshape_3d(ctx, x_out, d_head, L, n_head * N); // [N*n_head, L, d_head]
return x_out;
}
x_out = ggml_reshape_3d(ctx, x_out, d_head, L, n_head * N); // [N*n_head, L, d_head]
return x_out;

// Non-interleaved: pairs (i, i + d_head/2) are contiguous halves of the head dim, so the
// rotation is computed on views of the permuted x and assembled with one concat, avoiding
// the extra permute+cont round trips the interleaved layout requires.
auto x_lo = ggml_view_3d(ctx, x, d_head / 2, L, n_head * N, x->nb[1], x->nb[2], 0); // [d_head/2, L, n_head*N]
auto x_hi = ggml_view_3d(ctx, x, d_head / 2, L, n_head * N, x->nb[1], x->nb[2], (d_head / 2) * x->nb[0]); // [d_head/2, L, n_head*N]

auto pe2 = ggml_cont(ctx, ggml_permute(ctx, pe, 2, 3, 0, 1)); // [d_head/2, L, 2, 2]
auto cos = ggml_view_2d(ctx, pe2, d_head / 2, L, pe2->nb[1], 0); // [d_head/2, L] = pe[0,0,i,l]
auto sin = ggml_view_2d(ctx, pe2, d_head / 2, L, pe2->nb[1], pe2->nb[3]); // [d_head/2, L] = pe[0,1,i,l]

auto part0 = ggml_sub(ctx, ggml_mul(ctx, x_lo, cos), ggml_mul(ctx, x_hi, sin)); // [d_head/2, L, n_head*N]
auto part1 = ggml_add(ctx, ggml_mul(ctx, x_lo, sin), ggml_mul(ctx, x_hi, cos)); // [d_head/2, L, n_head*N]
return ggml_concat(ctx, part0, part1, 0); // [d_head, L, n_head*N]
}

__STATIC_INLINE__ ggml_tensor* attention(GGMLRunnerContext* ctx,
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