/*
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/*
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* Simple parameterized hash function
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* Simple parameterized hash function
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*
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*
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* Takes an input item and folds it back upon itself using xor
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* Takes an input item and folds it back upon itself using xor
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* as a reduction function. Works only for hash tables with
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* as a reduction function. Works only for hash tables with
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* a natural power of 2.
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* a natural power of 2.
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*/
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*/
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module basic_hashfunc
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module basic_hashfunc
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#(parameter input_sz=48,
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#(parameter input_sz=48,
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parameter table_sz=1024,
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parameter table_sz=1024,
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parameter fsz=clogb2(table_sz))
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parameter fsz=$clog2(table_sz))
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(
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(
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input [input_sz-1:0] hf_in,
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input [input_sz-1:0] hf_in,
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output reg [fsz-1:0] hf_out);
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output reg [fsz-1:0] hf_out);
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//localparam folds = (input_sz/fsz) + ( (input_sz%fsz) == 0) ? 0 : 1;
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// const function not supported by Icarus Verilog
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localparam folds = num_folds(input_sz, fsz);
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//localparam folds = num_folds(input_sz, fsz);
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localparam folds = 5;
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wire [folds*fsz-1:0] tmp_array;
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wire [folds*fsz-1:0] tmp_array;
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assign tmp_array = hf_in;
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assign tmp_array = hf_in;
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integer f, b;
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integer f, b;
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always @*
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always @*
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begin
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begin
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for (b=0; b<fsz; b=b+1)
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for (b=0; b<fsz; b=b+1)
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begin
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begin
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hf_out[b] = 0;
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hf_out[b] = 0;
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for (f=0; f<folds; f=f+1)
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for (f=0; f<folds; f=f+1)
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hf_out[b] = hf_out[b]^tmp_array[f*fsz+b];
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hf_out[b] = hf_out[b]^tmp_array[f*fsz+b];
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end
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end
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end
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end
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function integer num_folds;
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function integer num_folds;
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input [31:0] in_sz;
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input [31:0] in_sz;
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input [31:0] func_sz;
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input [31:0] func_sz;
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integer tmp_in_sz;
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integer tmp_in_sz;
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begin
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begin
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num_folds = 0;
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num_folds = 0;
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tmp_in_sz = in_sz;
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tmp_in_sz = in_sz;
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while (tmp_in_sz > 0)
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while (tmp_in_sz > 0)
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begin
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begin
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tmp_in_sz = tmp_in_sz - func_sz;
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tmp_in_sz = tmp_in_sz - func_sz;
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num_folds = num_folds + 1;
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num_folds = num_folds + 1;
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end
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end
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end
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end
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endfunction
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endfunction
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function integer clogb2;
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/* -----\/----- EXCLUDED -----\/-----
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input [31:0] depth;
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function integer clogb2;
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integer i;
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input [31:0] depth;
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begin
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integer i;
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i = depth;
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begin
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for (clogb2=0; i>0; clogb2=clogb2+1)
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i = depth;
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i = i >> 1;
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for (clogb2=0; i>0; clogb2=clogb2+1)
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end
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i = i >> 1;
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endfunction // for
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end
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endfunction // for
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-----/\----- EXCLUDED -----/\----- */
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endmodule // hashfunc
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endmodule // hashfunc
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