Each element O in the feature map is computed by a filter denoted by f j (1 ≤ j ≤ M ) from the N -gram word sequences in t for a fixed integer N , as , where • denotes element-wise multiplication followed by the summation of the resulting elements (i.e., a Frobenious inner product of W f j and x i:i+N −1 ) and ReLU(x) = max(0, x).
we construct a feature map by convolving a text fragment with a filter, which is parameterized by weight W f j ∈ R d×N and bias b f j ∈ R. Note that there can be several sets of feature maps where each set covers N -grams for different N .