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ggml-cuda : reduce redundant expf calls in GDN KDA kernel #20295

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ggml-cuda : reduce redundant expf calls in GDN KDA kernel #20295

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f5ae10e
ggml-cuda: gdn use shared mem for HIP
am17an Mar 9, 2026
2d6b28d
const
am17an Mar 9, 2026
ef56a76
Merge pull request #20282 from am17an:hip-gdn-use-shared
simonxluo Mar 9, 2026
637947c
Revert "Merge pull request #20282 from am17an:hip-gdn-use-shared"
simonxluo Mar 9, 2026
1aad9f1
ggml-cuda : reduce redundant expf calls in GDN KDA kernel
simonxluo Mar 9, 2026
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12 changes: 10 additions & 2 deletions ggml/src/ggml-cuda/gated_delta_net.cu
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Original file line number Diff line number Diff line change
Expand Up @@ -82,11 +82,19 @@ __global__ void gated_delta_net_cuda(const float * q,

attn_data[col] = attn_col * scale;
} else {
// Optimization: pre-compute expf(g_t[i]) once and reuse
// This reduces expf calls from 2*S_v to S_v per token
float g_exp[S_v];
#pragma unroll
for (int i = 0; i < S_v; i++) {
g_exp[i] = expf(g_t[i]);
}

// kv[col] = sum_i g[i] * S[i][col] * k[i]
float kv_col = 0.0f;
#pragma unroll
for (int i = 0; i < S_v; i++) {
kv_col += expf(g_t[i]) * s[i] * k_t[i];
kv_col += g_exp[i] * s[i] * k_t[i];
}

// delta[col] = (v[col] - kv[col]) * beta
Expand All @@ -97,7 +105,7 @@ __global__ void gated_delta_net_cuda(const float * q,
float attn_col = 0.0f;
#pragma unroll
for (int i = 0; i < S_v; i++) {
s[i] = expf(g_t[i]) * s[i] + k_t[i] * delta_col;
s[i] = g_exp[i] * s[i] + k_t[i] * delta_col;
attn_col += s[i] * q_t[i];
}

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