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Diffstat (limited to 'modexp_fpga_systolic.cpp')
| -rw-r--r-- | modexp_fpga_systolic.cpp | 118 |
1 files changed, 118 insertions, 0 deletions
diff --git a/modexp_fpga_systolic.cpp b/modexp_fpga_systolic.cpp new file mode 100644 index 0000000..9dce130 --- /dev/null +++ b/modexp_fpga_systolic.cpp @@ -0,0 +1,118 @@ +// +// modexp_fpga_systolic.cpp +// ------------------------ +// Systolic Multiplier +// +// Authors: Pavel Shatov +// Copyright (c) 2017, NORDUnet A/S +// All rights reserved. +// +// Redistribution and use in source and binary forms, with or without +// modification, are permitted provided that the following conditions are +// met: +// - Redistributions of source code must retain the above copyright notice, +// this list of conditions and the following disclaimer. +// +// - Redistributions in binary form must reproduce the above copyright +// notice, this list of conditions and the following disclaimer in the +// documentation and/or other materials provided with the distribution. +// +// - Neither the name of the NORDUnet nor the names of its contributors may +// be used to endorse or promote products derived from this software +// without specific prior written permission. +// +// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS +// IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED +// TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A +// PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT +// HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, +// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED +// TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR +// PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF +// LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING +// NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS +// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. +// + + +//---------------------------------------------------------------- +// Headers +//---------------------------------------------------------------- +#include "modexp_fpga_model.h" +#include "modexp_fpga_model_pe.h" + + +//---------------------------------------------------------------- +void multiply_systolic(const FPGA_WORD *A, const FPGA_WORD *B, FPGA_WORD *P, size_t len_ab, size_t len_p) +//---------------------------------------------------------------- +{ + // counters + size_t i, j, k; + + // index + size_t j_index; + + // current words of A and B + FPGA_WORD Aj, Bj; + + // number of full systolic cycles needed to multiply entire B by one word of A + size_t num_systolic_cycles = len_ab / SYSTOLIC_NUM_WORDS; + if ((num_systolic_cycles * SYSTOLIC_NUM_WORDS) < len_ab) num_systolic_cycles++; + + // buffers + FPGA_WORD t[MAX_SYSTOLIC_CYCLES][SYSTOLIC_NUM_WORDS]; // accumulator + FPGA_WORD s[MAX_SYSTOLIC_CYCLES][SYSTOLIC_NUM_WORDS]; // intermediate product + FPGA_WORD c_in[MAX_SYSTOLIC_CYCLES][SYSTOLIC_NUM_WORDS]; // input carries + FPGA_WORD c_out[MAX_SYSTOLIC_CYCLES][SYSTOLIC_NUM_WORDS]; // output carries + + // initialize arrays of accumulators and carries to zeroes + for (i=0; i<num_systolic_cycles; i++) + for (j=0; j<SYSTOLIC_NUM_WORDS; j++) + c_in[i][j] = 0, t[i][j] = 0; + + // do the math + for (i=0; i<len_p; i++) + { + // reset word index + j_index = 0; + + // scan chunks of A + for (k=0; k<num_systolic_cycles; k++) + { + // simulate how systolic array would work + for (j=0; j<SYSTOLIC_NUM_WORDS; j++) + { + // current words of B and A + Bj = (j_index < len_ab) ? B[j_index] : 0; + Aj = (i < len_ab) ? A[i] : 0; + + // Pj = Aj * Bj + pe_mul(Aj, Bj, t[k][j], c_in[k][j], &s[k][j], &c_out[k][j]); + + // store current word of P + if ((k == 0) && (j == 0)) P[i] = s[0][0]; + + // update index + j_index++; + } + + // propagate carries + for (j=0; j<SYSTOLIC_NUM_WORDS; j++) + c_in[k][j] = c_out[k][j]; + + // update accumulator + for (j=1; j<SYSTOLIC_NUM_WORDS; j++) + t[k][j-1] = s[k][j]; + + // update accumulator + if (k > 0) + t[k-1][SYSTOLIC_NUM_WORDS-1] = s[k][0]; + + } + } +} + + +//---------------------------------------------------------------- +// End of file +//---------------------------------------------------------------- |