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FPGA-Neural/hardware/v3/sim/tb_np_packed_layer_reuse.v
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micheleandClaude Sonnet 5 9ca180a787 test: first real end-to-end weight-reuse -> packed-core integration, bug found+fixed (EXP-0062) 
New hardware/v3/sim/tb_np_packed_layer_reuse.v: real SDR SDRAM ->
layer_prefetch_ctrl.v -> layer_weight_buffer.v -> weight_tile_gather.v
-> neural_processor_packed.v, ALL real synthesizable RTL (unlike
EXP-0058, which still had a testbench-only gather step).

First run: 15/16 PASS, 1 FAIL. Root-caused (not re-run away): a
testbench handshake bug, not a DUT bug -- operand_valid was held one
extra clock edge after each accepted tile, double-consuming stale
data every tile on every pair. 15 of 16 "passed" only because this
test's saturating outputs happened to clamp to the same value whether
or not the accumulator was inflated -- disclosed as a real methodology
risk, not swept under the rug. Fixed by dropping operand_valid the
same delta the handshake is observed.

Re-verified after the fix: 16/16 PASS, 0 errors, bit-exact against an
independent golden model, through the complete real RTL path.

Full writeup in hardware/v2/logs/experiments.log EXP-0062.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MUG92aM9m68TRc4rG55BcC
2026-09-16 23:41:35 +02:00

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`timescale 1ns/1ps
// ============================================================
// V3 follow-up to EXP-0058/EXP-0061 -- first real end-to-end
// integration of the weight-reuse memory path with the DSP48-packed
// compute core, ALL real synthesizable RTL (unlike EXP-0058, which
// still had a testbench-only byte-gather step):
//
// sdram_controller.v + sdram_model.v (real SDR SDRAM path, v2, unmodified)
// -> layer_prefetch_ctrl.v (real RTL, v2, unmodified)
// -> layer_weight_buffer.v (real RTL, v2, unmodified)
// -> weight_tile_gather.v (real RTL, v3, EXP-0061)
// -> neural_processor_packed.v (real RTL, v3, EXP-0059)
//
// One "layer" = one resident filter (128 taps, 16 tiles), fetched
// ONCE, reused across M=8 positions PAIRED UP (pos_a, pos_b) two at a
// time into neural_processor_packed.v's own A/B job structure -- each
// pair shares ONE weight_tile_gather fetch per tile (gathered once,
// consumed by both A and B), matching the whole point of the DSP48
// packing (one weight, two independent activations).
//
// Golden model: SAME weight_byte/input_byte formulas as EXP-0058's
// own tb_neural_processor_layer_reuse.v (independently reproduced
// here, not shared code, per this project's own "third oracle"
// convention), evaluated independently for pos_a and pos_b.
// ============================================================
module tb;
localparam BURST_LEN = 8;
localparam ROW_BITS = 13;
localparam COL_BITS = 10;
localparam BANK_BITS = 2;
localparam ADDR_WIDTH = BANK_BITS + ROW_BITS + COL_BITS;
localparam CLK_FREQ_MHZ = 64;
localparam CLK_PERIOD_NS = 1000.0/CLK_FREQ_MHZ;
localparam DATA_WIDTH = 8;
localparam P_IN = 8;
localparam ACC_WIDTH = 32;
localparam N_INPUTS = 128;
localparam N_TILES = N_INPUTS/P_IN; // 16
localparam LAYER_BYTES = N_INPUTS;
localparam BUFADDRW = $clog2(LAYER_BYTES);
localparam L = 4; // layers
localparam M = 8; // reuse positions per layer (paired 2 at a time)
localparam WORDS_PER_LAYER = LAYER_BYTES/2;
localparam ACT_RELU = 2'd1;
reg clk = 0;
always #(CLK_PERIOD_NS/2.0) clk = ~clk;
reg rst;
integer cyc;
always @(posedge clk) if (!rst) cyc <= cyc + 1;
// ---- real SDRAM controller + model (v2, unmodified) ----
wire ctrl_req, ctrl_wr;
wire [ADDR_WIDTH-1:0] ctrl_addr;
wire [16*BURST_LEN-1:0] ctrl_wdata;
wire [2*BURST_LEN-1:0] ctrl_wmask;
wire [16*BURST_LEN-1:0] ctrl_rdata;
wire ctrl_ready, ctrl_busy;
wire cke, cs_n, ras_n, cas_n, we_n;
wire [BANK_BITS-1:0] ba;
wire [ROW_BITS-1:0] a;
wire [15:0] dq;
wire [1:0] dqm;
sdram_controller #(
.CLK_FREQ_MHZ(CLK_FREQ_MHZ), .BURST_LEN(BURST_LEN),
.ROW_BITS(ROW_BITS), .COL_BITS(COL_BITS), .BANK_BITS(BANK_BITS)
) u_ctrl (
.clk(clk), .rst(rst),
.req(ctrl_req), .wr(ctrl_wr), .addr(ctrl_addr), .wdata(ctrl_wdata), .wmask(ctrl_wmask),
.rdata(ctrl_rdata), .ready(ctrl_ready), .busy(ctrl_busy),
.sdram_cke(cke), .sdram_cs_n(cs_n), .sdram_ras_n(ras_n), .sdram_cas_n(cas_n), .sdram_we_n(we_n),
.sdram_ba(ba), .sdram_a(a), .sdram_dq(dq), .sdram_dqm(dqm)
);
sdram_model #(
.CLK_FREQ_MHZ(CLK_FREQ_MHZ), .ROW_BITS(ROW_BITS), .COL_BITS(COL_BITS), .BANK_BITS(BANK_BITS)
) u_mem (
.clk(clk), .cke(cke), .cs_n(cs_n), .ras_n(ras_n), .cas_n(cas_n), .we_n(we_n),
.ba(ba), .a(a), .dq(dq), .dqm(dqm)
);
reg wpre_req, wpre_wr;
reg [ADDR_WIDTH-1:0] wpre_addr;
reg [16*BURST_LEN-1:0] wpre_wdata;
reg pre_active;
wire pf_ctrl_req, pf_ctrl_wr;
wire [ADDR_WIDTH-1:0] pf_ctrl_addr;
wire [16*BURST_LEN-1:0] pf_ctrl_wdata;
wire [2*BURST_LEN-1:0] pf_ctrl_wmask;
assign ctrl_req = pre_active ? wpre_req : pf_ctrl_req;
assign ctrl_wr = pre_active ? wpre_wr : pf_ctrl_wr;
assign ctrl_addr = pre_active ? wpre_addr : pf_ctrl_addr;
assign ctrl_wdata = pre_active ? wpre_wdata : pf_ctrl_wdata;
assign ctrl_wmask = pre_active ? {(2*BURST_LEN){1'b0}} : pf_ctrl_wmask;
function automatic signed [7:0] weight_byte(input integer li, input integer t);
weight_byte = $signed(8'((li*17 + t*29 + 13) & 8'hFF));
endfunction
function automatic signed [7:0] input_byte(input integer li, input integer pos, input integer t);
input_byte = $signed(8'((li*11 + pos*41 + t*7 + 3) & 8'hFF));
endfunction
task automatic sdram_write_burst(input [ADDR_WIDTH-1:0] word_addr, input [16*BURST_LEN-1:0] data);
begin
@(posedge clk); while (ctrl_busy) @(posedge clk);
wpre_req = 1'b1; wpre_wr = 1'b1; wpre_addr = word_addr; wpre_wdata = data;
@(posedge clk); wpre_req = 1'b0;
while (!ctrl_ready) @(posedge clk);
end
endtask
task automatic preload_sdram_layers;
integer li, bi, wb, tt;
reg [16*BURST_LEN-1:0] burst_data;
begin
for (li = 0; li < L; li = li + 1) begin
for (bi = 0; bi < (LAYER_BYTES/(2*BURST_LEN)); bi = bi + 1) begin
for (wb = 0; wb < BURST_LEN; wb = wb + 1) begin
tt = bi*(2*BURST_LEN) + wb*2;
burst_data[wb*16 +: 16] = {weight_byte(li, tt+1), weight_byte(li, tt)};
end
sdram_write_burst((li*WORDS_PER_LAYER + bi*BURST_LEN), burst_data);
end
end
end
endtask
// ---- layer_prefetch_ctrl.v (v2, real, unmodified) ----
reg pf_start;
reg [ADDR_WIDTH-1:0] pf_layer_base;
wire pf_busy, pf_done;
wire pf_fill_we;
wire [BUFADDRW-1:0] pf_fill_addr;
wire [7:0] pf_fill_data;
layer_prefetch_ctrl #(
.DATA_WIDTH(8), .LAYER_BYTES(LAYER_BYTES), .BURST_LEN(BURST_LEN), .ADDR_WIDTH(ADDR_WIDTH)
) u_pf (
.clk(clk), .rst(rst),
.start(pf_start), .layer_base(pf_layer_base), .busy(pf_busy), .done(pf_done),
.fill_we(pf_fill_we), .fill_addr(pf_fill_addr), .fill_data(pf_fill_data),
.ctrl_req(pf_ctrl_req), .ctrl_wr(pf_ctrl_wr), .ctrl_addr(pf_ctrl_addr),
.ctrl_wdata(pf_ctrl_wdata), .ctrl_wmask(pf_ctrl_wmask),
.ctrl_rdata(ctrl_rdata), .ctrl_ready(ctrl_ready), .ctrl_busy(ctrl_busy)
);
// ---- layer_weight_buffer.v (v2, real, unmodified) ----
wire [BUFADDRW-1:0] lwb_rd_addr;
wire [7:0] lwb_rd_data;
reg consume_done;
wire active_sel, swapped;
layer_weight_buffer #(.DATA_WIDTH(8), .LAYER_DEPTH(LAYER_BYTES)) u_lwb (
.clk(clk), .rst(rst),
.fill_we(pf_fill_we), .fill_addr(pf_fill_addr), .fill_data(pf_fill_data), .fill_done(pf_done),
.rd_addr(lwb_rd_addr), .rd_data(lwb_rd_data), .consume_done(consume_done),
.active_sel(active_sel), .swapped(swapped)
);
// ---- weight_tile_gather.v (v3, real, EXP-0061) ----
reg tile_req;
reg [BUFADDRW-1:0] tile_base;
wire tile_valid;
wire [DATA_WIDTH*P_IN-1:0] tile_data;
weight_tile_gather #(
.DATA_WIDTH(DATA_WIDTH), .P_IN(P_IN), .BUFADDRW(BUFADDRW)
) u_gather (
.clk(clk), .rst(rst),
.tile_req(tile_req), .tile_base(tile_base),
.tile_valid(tile_valid), .tile_data(tile_data),
.rd_addr(lwb_rd_addr), .rd_data(lwb_rd_data)
);
// ---- neural_processor_packed.v (v3, real, EXP-0059) ----
reg job_valid;
wire job_ready;
reg [15:0] job_node_id_a, job_node_id_b;
reg signed [DATA_WIDTH-1:0] job_bias;
reg [1:0] job_activation;
reg operand_valid;
wire operand_ready;
reg signed [DATA_WIDTH*P_IN-1:0] input_data_a, input_data_b;
reg [DATA_WIDTH*P_IN-1:0] weight_data;
reg tile_last;
wire result_valid;
reg result_ready;
wire signed [DATA_WIDTH-1:0] result_data_a, result_data_b;
wire [15:0] result_node_id_a, result_node_id_b;
wire [3:0] np_state;
wire np_error;
neural_processor_packed #(
.DATA_WIDTH(DATA_WIDTH), .P_IN(P_IN), .ACC_WIDTH(ACC_WIDTH)
) u_np (
.clk(clk), .rst(rst),
.job_valid(job_valid), .job_ready(job_ready),
.job_node_id_a(job_node_id_a), .job_node_id_b(job_node_id_b),
.job_bias(job_bias), .job_activation(job_activation),
.operand_valid(operand_valid), .operand_ready(operand_ready),
.input_data_a(input_data_a), .input_data_b(input_data_b),
.weight_data(weight_data), .tile_last(tile_last),
.result_valid(result_valid), .result_ready(result_ready),
.result_data_a(result_data_a), .result_data_b(result_data_b),
.result_node_id_a(result_node_id_a), .result_node_id_b(result_node_id_b),
.np_state(np_state), .np_error(np_error)
);
integer errors, tests;
integer li_i, pp_i, t, k;
integer acc_a, acc_b, s_a, s_b;
reg signed [DATA_WIDTH-1:0] expected_a, expected_b;
integer t0, total_cycles;
task automatic run_one_pair(input integer li, input integer pos_a, input integer pos_b);
begin
@(posedge clk);
tests = tests + 1;
job_node_id_a = li[15:8]*8'(M) + pos_a[15:0];
job_node_id_b = li[15:8]*8'(M) + pos_b[15:0];
job_bias = {DATA_WIDTH{1'b0}};
job_activation = ACT_RELU;
job_valid = 1;
while (!job_ready) @(posedge clk);
@(posedge clk); #1;
job_valid = 0;
acc_a = 0; acc_b = 0;
for (t = 0; t < N_TILES; t = t + 1) begin
tile_req = 1'b1;
tile_base = (t*P_IN);
@(posedge clk); #1;
tile_req = 1'b0;
while (!tile_valid) @(posedge clk);
#1;
weight_data = tile_data;
for (k = 0; k < P_IN; k = k + 1) begin
input_data_a[k*DATA_WIDTH +: DATA_WIDTH] = input_byte(li, pos_a, t*P_IN+k);
input_data_b[k*DATA_WIDTH +: DATA_WIDTH] = input_byte(li, pos_b, t*P_IN+k);
acc_a = acc_a + (input_byte(li, pos_a, t*P_IN+k) * weight_byte(li, t*P_IN+k));
acc_b = acc_b + (input_byte(li, pos_b, t*P_IN+k) * weight_byte(li, t*P_IN+k));
end
tile_last = (t == N_TILES - 1);
operand_valid = 1;
@(posedge clk);
while (!operand_ready) @(posedge clk);
#1;
// operand_ready stays high continuously across the whole
// tile stream (unlike a one-shot req/ready pulse) -- must
// drop operand_valid THE SAME delta this handshake is
// observed, before any further time passes, or the next
// posedge re-samples operand_valid=1 with STILL-STALE
// weight_data/input_data and double-consumes this tile
// (found empirically: acc_reg_a/b came out ~9x too large,
// root-caused via hierarchical acc_reg_a/b + valid0 trace).
operand_valid = 1'b0;
end
operand_valid = 0;
tile_last = 0;
result_ready = 1;
while (!result_valid) @(posedge clk);
s_a = acc_a; s_b = acc_b;
if (s_a <= 0) expected_a = 0; else if (s_a > 127) expected_a = 8'sd127; else expected_a = s_a[DATA_WIDTH-1:0];
if (s_b <= 0) expected_b = 0; else if (s_b > 127) expected_b = 8'sd127; else expected_b = s_b[DATA_WIDTH-1:0];
if (result_data_a !== expected_a || result_data_b !== expected_b) begin
$display("FAIL li=%0d pos_a=%0d pos_b=%0d: got_a=%0d got_b=%0d expected_a=%0d expected_b=%0d",
li, pos_a, pos_b, $signed(result_data_a), $signed(result_data_b), $signed(expected_a), $signed(expected_b));
errors = errors + 1;
end else begin
$display("PASS li=%0d pos_a=%0d pos_b=%0d: a=%0d b=%0d (packed weight-reuse path, real RTL)",
li, pos_a, pos_b, $signed(result_data_a), $signed(result_data_b));
end
@(posedge clk);
while (!job_ready || np_state !== 4'd0) @(posedge clk);
end
endtask
initial begin
errors = 0; tests = 0; cyc = 0;
rst = 1; pre_active = 1'b1;
wpre_req = 0; wpre_wr = 0; wpre_addr = 0; wpre_wdata = 0;
pf_start = 0; pf_layer_base = 0; consume_done = 0;
tile_req = 0; tile_base = 0;
job_valid = 0; job_node_id_a = 0; job_node_id_b = 0; job_bias = 0; job_activation = ACT_RELU;
operand_valid = 0; input_data_a = 0; input_data_b = 0; weight_data = 0; tile_last = 0;
result_ready = 0;
repeat(5) @(posedge clk);
rst = 0;
@(posedge clk); while (ctrl_busy) @(posedge clk);
$display("=== preload SDRAM with %0d resident-filter weight sets (%0d taps each) ===", L, N_INPUTS);
preload_sdram_layers;
@(posedge clk);
pre_active = 1'b0;
$display("=== real RTL weight-reuse path -> neural_processor_packed.v, %0d layers x %0d positions (paired) ===", L, M);
t0 = cyc;
for (li_i = 0; li_i < L; li_i = li_i + 1) begin
pf_layer_base = li_i * WORDS_PER_LAYER;
pf_start = 1'b1; @(posedge clk); #1; pf_start = 1'b0;
while (!pf_done) @(posedge clk);
#1;
consume_done = 1'b1; @(posedge clk); #1; consume_done = 1'b0;
@(posedge clk); #1;
for (pp_i = 0; pp_i < M; pp_i = pp_i + 2) begin
run_one_pair(li_i, pp_i, pp_i+1);
end
end
total_cycles = cyc - t0;
$display("=== RESULT: %0d/%0d PASS, %0d errors, %0d total cycles for %0d layers x %0d positions (%0d pairs) ===",
tests-errors, tests, errors, total_cycles, L, M, L*(M/2));
if (errors == 0) $display("ALL TESTS PASSED (tb_np_packed_layer_reuse)");
$finish;
end
endmodule
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