Fuji Xerox Co., Ltd.

Shinjiro Inabata

Nobuaki Miyakawa

So Yamada

Shinjiro Toyoda

To obtain the sufficiently precise result of floating-point accumulation even if the quantity of computation is enormous, a floating-point accumulator according to the present invention is constituted as follows: When two floating-point data are stored in any of shift registers, the two data are respectively output to BUS0 and BUS1 via one connected to the shift register of buffers. The two output data are input to an adder via BUS0 and BUS1 and output as added result data after adding the floating-point numbers. The above added result data is returned to each input of the shift registers via BUSW and a multiplexer and written into the shift register corresponding to the addition of the higher level by one of the shift register holding floating-point data before addition. The floating-point numbers are accumulated by repeating the above operation.

Floating-point accumulator

Electron repulsion integrals are classified according to atomic nucleus coordinates, etc., coefficients are generated and are stored in a data memory, multiplication with addition operation is executed according to a product sum procedure of auxiliary integrals of recursive order 1 or less, and the result is stored in the data memory. Next, density matrix element is stored in the data memory, a multiplication with addition operation procedure of an electron repulsion integral of recursive order 2 not containing any procedure of recursive order 1 or less is generated, and an instruction memory is updated. Multiplication with addition operation is executed while data is read from the data memory, and the result is stored in the data memory. At the termination of the product sum procedure, calculation of electron repulsion integral gRstu is complete and the Fock matrix element value is updated. The Fock matrix element containing electron repulsion integral when a linear combination constant to minimize the expected value of molecule energy required for molecular orbital calculation is found is thus found by performing recursive multiplication with addition operation.

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Ebina, Japan

Shinjiro Inabata