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Temporary fix for rms norm backward on CPU. #1197

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Temporary fix for rms norm backward on CPU. #1197

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13 changes: 9 additions & 4 deletions src/ggml-cpu/ops.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3292,6 +3292,7 @@ static void ggml_compute_forward_rms_norm_back_f32(
//const float rms = sqrtf(mean_eps);
const float rrms = 1.0f / sqrtf(mean_eps);
//const float scale = -rrms/(ne00 * mean_eps); // -1/(n*rms**3)
const float scale_x = rrms * (-sum_xdz)/sum_eps;

{
// z = rms_norm(x)
Expand Down Expand Up @@ -3390,11 +3391,15 @@ static void ggml_compute_forward_rms_norm_back_f32(
float * dx = (float *) ((char *) dst->data + i01*nb1 + i02*nb2 + i03*nb3);

// dx[i00] = (x*(-sum_xdz/sum_eps) + dz) / sqrtf(mean_eps)
ggml_vec_cpy_f32 (ne00, dx, x);
// ggml_vec_cpy_f32 (ne00, dx, x);
// ggml_vec_scale_f32(ne00, dx, -mean_xdz/mean_eps);
ggml_vec_scale_f32(ne00, dx, (float)(-sum_xdz)/sum_eps);
ggml_vec_acc_f32 (ne00, dx, dz);
ggml_vec_scale_f32(ne00, dx, rrms);
// ggml_vec_scale_f32(ne00, dx, (float)(-sum_xdz)/sum_eps);
// ggml_vec_acc_f32 (ne00, dx, dz);
// ggml_vec_scale_f32(ne00, dx, rrms);

for (int64_t i00 = 0; i00 < ne00; i00++) {
dx[i00] = rrms * dz[i00] + scale_x * x[i00];
}
}
}
}
Expand Down