Arithmetic circuit
An arithmetic circuit includes an LUT generation circuit ( 1 ) that, when coefficients c[n] (n=1, . . . , N) are paired two by two, outputs a value calculated for each of the pairs, and a distributed arithmetic circuit ( 2 - m ) that calculates values y[m] of product-sum arithmetic, by which data x[m, n] of a data set X[m] containing M pairs of data x[m, n] is multiplied by the coefficients c[n] and the products are summed up, in parallel for each of the M pairs. The distributed arithmetic circuit ( 2 - m ) includes a plurality of binomial distributed arithmetic circuits that calculate the value of binomial product-sum arithmetic in parallel for each of the pairs, based on a value obtained by pairing N data x[m, n] corresponding to the circuit two by two, a value obtained by pairing the coefficients c[n] two by two, and the value calculated by the LUT generation circuit ( 1 ), and a binomial distributed arithmetic result summing circuit that sums up the values calculated by the binomial distributed arithmetic circuits and outputs the sum as y[m].
1. An arithmetic circuit that receives a data set X[m] (m=M) containing M (M is an integer of not less than 2) pairs of N (N is an integer of not less than 2) data x[m, n] (n=1, . . . , N), and N coefficients c[n], and calculates and outputs M values y[m] of product-sum arithmetic, the arithmetic circuit comprising:
an LUT generation circuit configured to, when the N coefficients c[n] are paired two by two, output a value calculated for each of the pairs; and
M distributed arithmetic circuits configured to calculate and output, in parallel for each of the M pairs, the values y[m] of the product-sum arithmetics as a result of multiplying the N data x[m, n] of the data set X[m] by the N coefficients c[n] and summing up the products,
wherein each of the distributed arithmetic circuits includes:
a plurality of binomial distributed arithmetic circuits configured to calculate and output, based on a value obtained by pairing the N data x[m, n] corresponding to the circuit two by two, a value obtained by pairing the N coefficients c[n] two by two, and the value calculated by the LUT generation circuit, a value of binomial product-sum arithmetic that multiplies the two data x[m, n] by the two coefficients c[n] and sums up the products, in parallel for each of the pairs; and
a binomial distributed arithmetic result summing circuit configured to output a result of summing up the values calculated by the plurality of binomial distributed arithmetic circuits, as the values y[m] of the product-sum arithmetic.
2. The arithmetic circuit according to claim 1 , further comprising an LUT latch circuit formed between the LUT generation circuit and the M distributed arithmetic circuits, and configured to hold the N coefficients c[n] and the value calculated by the LUT generation circuit in synchronism with a clock, and output the held values to the M distributed arithmetic circuits.
3. The arithmetic circuit according to claim 1 , wherein
the LUT generation circuit calculates, as values d[n′], a sum c[2×n′−1]+c[2×n′] (n′=1, . . . , N′) of values c[2×n′−1] and c[2×n′] obtained by pairing the N coefficients c[n] two by two, for each of N′ (N′ is a maximum integer that is not more than N/2) pairs, and
each of the distributed arithmetic circuits receives the data set X[m], the coefficients c[n] output from the LUT generation circuit, and the values d[n′] calculated by the LUT generation circuit, and outputs the values y[m] of the product-sum arithmetic as a result of multiplying the N data x[m, n], which correspond to the circuit, of the data set X[m] by the N coefficients c[n] and summing up the products.
4. The arithmetic circuit according to claim 1 , wherein
each of the distributed arithmetic circuits further includes an auxiliary multiplication circuit configured to output a result of calculating c[N]×x[m, N] when N is an odd number, and
the binomial distributed arithmetic result summing circuit outputs, when N is an odd number, a result of summing up the values calculated by the plurality of binomial distributed arithmetic circuits and the value calculated by the auxiliary multiplication circuit, as the values y[m] of the product-sum arithmetic.
5. The arithmetic circuit according to claim 1 , wherein the binomial distributed arithmetic circuit includes:
a plurality of indexing circuits formed for each bit position of two values of the same pair of the N data x[m, n], and configured to obtain, for each bit position, one element value corresponding to two values in the same bit position, which form two values of the same pair of the N data x[m, n], from element values including 0, two values of the same pair of the N coefficients c[n], and a value calculated from the two values of the coefficients c[n] by the LUT generation circuit;
a plurality of multiple calculation circuits configured to multiply, for each bit position, the element values obtained by the plurality of indexing circuits by 2″) (1 is an ordinal number of a bit position); and
a summing circuit configured to output a result of summing up the values calculated by the plurality of multiple calculation circuits, as the value of the binomial product-sum arithmetic.