How to do dot product between matrices in caffe?

In inner product layer, I need to multiply (top_diff * bottom_data) .* (2*weight). First we calculate (result = top_diff * bottom_data) as matrix multiplication in caffe_cpu_gemm and then do a dot product between weight and result.

More explanation is defined as follow:

const Dtype* weight = this->blobs_[0]->cpu_data();
     if (this->param_propagate_down_[0]) {
            const Dtype* top_diff = top[0]->cpu_diff();
            const Dtype* bottom_data = bottom[0]->cpu_data();
caffe_cpu_gemm<Dtype>(CblasTrans, CblasNoTrans, N_, K_, M_, (Dtype)1.,
        top_diff, bottom_data, (Dtype)1., this->blobs_[0]->mutable_cpu_diff());
}

For more understanding, I checked math_function.c. It is implemented as follows:

template<>
void caffe_cpu_gemm<float>(const CBLAS_TRANSPOSE TransA,
    const CBLAS_TRANSPOSE TransB, const int M, const int N, const int K,
    const float alpha, const float* A, const float* B, const float beta,
    float* C) {
  int lda = (TransA == CblasNoTrans) ? K : M;
  int ldb = (TransB == CblasNoTrans) ? N : K;
  cblas_sgemm(CblasRowMajor, TransA, TransB, M, N, K, alpha, A, lda, B,
      ldb, beta, C, N);
}

I think I should perform multiplication (result = top_diff * bottom_data) in caffe_cpu_gemm() and after that do dot product with weight. how should I do?!

Many thanks!!!! Any advice would be appreciated!

If you just want to perform dot product between two matrices, you can use the following function to multiply matrices on CPU,

void caffe_mul<float>(const int n, const float* a, const float* b, float* y)

If you want to do the same operation on a GPU, use this template

void caffe_gpu_mul<float>(const int N, const float* a, const float* b, float* y)

a and b are you matrices and c will contain the final result. N is the total number of elements in your matrix.

You can also use the 'Eltwise' layer, which already does this.