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[SM100] Add Kimi-K3 SiTU activation #67

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Merged
Fridge003 merged 1 commit into from
Jul 29, 2026
Merged

[SM100] Add Kimi-K3 SiTU activation #67

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33 changes: 26 additions & 7 deletions deep_gemm/include/deep_gemm/impls/sm100_fp8_fp4_mega_moe.cuh
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Original file line number Diff line number Diff line change
Expand Up @@ -1328,33 +1328,52 @@ sm100_fp8_fp4_mega_moe_impl(void* y,
tmem_empty_barriers[accum_stage_idx]->arrive(0u);
}

// Apply SwiGLU: silu(gate) * up
// Apply activation: SwiGLU, or Kimi-K3 SiTU via sentinel
// Gate/up pairs: (0, 2), (1, 3), (4, 6), (5, 7)
// K3-SITU-PATCH: kActivationClamp == 0.03125f (2^-5 magic;
// host asserts clamp >= 0 so negatives can't sentinel) selects SiTU:
// act = kSituBeta * tanh(gate/kSituBeta) * sigmoid(gate)
// up' = kSituLinearBeta * tanh(up/kSituLinearBeta)
// K3 config constants baked in (activation_situ_{beta,linear_beta}).
constexpr bool kUseSitu = (kActivationClamp == 0.03125f);
constexpr float kSituBeta = 4.0f;
constexpr float kSituLinearBeta = 25.0f;
auto fp32_values = reinterpret_cast<float*>(values);
#pragma unroll
for (uint32_t k = 0; k < 2; ++ k) {
auto bf16_gate = __float22bfloat162_rn(make_float2(fp32_values[k * 4], fp32_values[k * 4 + 1]));
auto bf16_up = __float22bfloat162_rn(make_float2(fp32_values[k * 4 + 2], fp32_values[k * 4 + 3]));

// Clamp
if constexpr (kActivationClamp != cute::numeric_limits<float>::infinity()) {
// Clamp (SwiGLU-with-limit only; SiTU soft-clips below)
if constexpr (!kUseSitu && kActivationClamp != cute::numeric_limits<float>::infinity()) {
bf16_gate = __hmin2(bf16_gate, {kActivationClamp, kActivationClamp});
bf16_up = __hmax2(bf16_up, {-kActivationClamp, -kActivationClamp});
bf16_up = __hmin2(bf16_up, {kActivationClamp, kActivationClamp});
}

// SwiGLU
// sigmoid(gate)
auto gate = __bfloat1622float2(bf16_gate);
auto neg_gate_exp = make_float2(
kFastMath ? __expf(-gate.x) : expf(-gate.x),
kFastMath ? __expf(-gate.y) : expf(-gate.y));
const auto denom = __fadd2_rn({1.0f, 1.0f}, neg_gate_exp);
float2 sig;
if constexpr (kFastMath) {
gate = __fmul2_rn(gate, {math::fast_rcp(denom.x), math::fast_rcp(denom.y)});
sig = {math::fast_rcp(denom.x), math::fast_rcp(denom.y)};
} else {
gate = {gate.x / denom.x, gate.y / denom.y};
sig = {1.0f / denom.x, 1.0f / denom.y};
}
auto up = __bfloat1622float2(bf16_up);
if constexpr (kUseSitu) {
// K3-SITU-PATCH: tanh-bounded gate, soft-clipped up
gate = {kSituBeta * tanhf(gate.x / kSituBeta) * sig.x,
kSituBeta * tanhf(gate.y / kSituBeta) * sig.y};
up = {kSituLinearBeta * tanhf(up.x / kSituLinearBeta),
kSituLinearBeta * tanhf(up.y / kSituLinearBeta)};
} else {
// SwiGLU: silu(gate) * up
gate = __fmul2_rn(gate, sig);
}
const auto up = __bfloat1622float2(bf16_up);
activation_values[i][k] = __fmul2_rn(__fmul2_rn(gate, up), weights);
}

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