tests/test.sh exit code (0 → resolved); the classification below is post-hoc and cannot change it.module TopModule (
input clk,
input rst,
input a_req_i,
input [7:0] a_addr_i,
output reg a_ack_o,
output reg [15:0] a_data_o,
input b_req_i,
input [7:0] b_addr_i,
output reg b_ack_o,
output reg [15:0] b_data_o,
output reg m_req_o,
output reg [7:0] m_addr_o,
input [15:0] m_data_i
);
// Two-stage registration of incoming requests.
// A fresh request is registered (rq1) one idle cycle before it is
// sampled as E (rq2). While a requester keeps req high its rq2 stays
// primed, so a back-to-back sample at E+5 fires immediately.
reg a_rq1, a_rq2;
reg b_rq1, b_rq2;
// Operation timeline counter: 0 = idle (this is the sample cycle E),
// 1 = E+1, 2 = E+2, 3 = E+3, 4 = E+4. Returns to 0 at E+5.
reg [2:0] cnt;
reg winner; // requester currently being served (0=A,1=B)
reg last_winner; // who won the operation just completed
reg warm; // next idle sample follows an operation (round-robin)
reg win; // temp: chosen winner for a sample
always @(posedge clk) begin
if (rst) begin
a_rq1 <= 1'b0;
a_rq2 <= 1'b0;
b_rq1 <= 1'b0;
b_rq2 <= 1'b0;
cnt <= 3'd0;
winner <= 1'b0;
last_winner <= 1'b0;
warm <= 1'b0;
m_req_o <= 1'b0;
m_addr_o <= 8'd0;
a_ack_o <= 1'b0;
a_data_o <= 16'd0;
b_ack_o <= 1'b0;
b_data_o <= 16'd0;
end else begin
// Request registration pipeline.
a_rq1 <= a_req_i;
a_rq2 <= a_rq1;
b_rq1 <= b_req_i;
b_rq2 <= b_rq1;
// Single-cycle outputs deassert by default.
m_req_o <= 1'b0;
m_addr_o <= 8'd0;
a_ack_o <= 1'b0;
b_ack_o <= 1'b0;
case (cnt)
3'd0: begin
if (a_rq2 | b_rq2) begin
// Arbitration.
if (warm) begin
// Directly after an operation: favour the
// requester that did NOT just win, if it asks;
// otherwise the one that did.
if (last_winner == 1'b0)
win = b_rq2 ? 1'b1 : 1'b0; // A just won -> prefer B
else
win = a_rq2 ? 1'b0 : 1'b1; // B just won -> prefer A
end else begin
// Cold sample after a fully idle stretch: favour A.
win = a_rq2 ? 1'b0 : 1'b1;
end
winner <= win;
last_winner <= win;
m_req_o <= 1'b1; // command at E+1
m_addr_o <= win ? b_addr_i : a_addr_i;
cnt <= 3'd1;
end else begin
// Fully idle stretch resets the fairness state.
warm <= 1'b0;
cnt <= 3'd0;
end
end
3'd1: cnt <= 3'd2; // E+1 -> E+2
3'd2: cnt <= 3'd3; // E+2 -> E+3
3'd3: begin
// m_data_i is valid this cycle (E+3); drive the winner's
// ack and word during E+4.
if (winner == 1'b0) begin
a_ack_o <= 1'b1;
a_data_o <= m_data_i;
end else begin
b_ack_o <= 1'b1;
b_data_o <= m_data_i;
end
cnt <= 3'd4;
end
3'd4: begin
// E+4 -> E+5: idle again, arm round-robin for next sample.
warm <= 1'b1;
cnt <= 3'd0;
end
default: cnt <= 3'd0;
endcase
end
end
endmodule
Syntax check the SystemVerilog module
(iverilog -g2012 -o /tmp/dut.out dut.sv 2>&1 && echo "IVERILOG OK") || (which verilator >/dev/null 2>&1 && verilator --lint-only -Wall dut.sv 2>&1 && echo "VERILATOR OK") || echo "no simulator available"
IVERILOG OK [stdout] IVERILOG OK
Compile and run testbench
cat > /tmp/tb.sv <<'EOF'
module tb;
reg clk=0, rst=1;
reg a_req=0; reg [7:0] a_addr=0;
reg b_req=0; reg [7:0] b_addr=0;
wire a_ack, b_ack, m_req;
wire [15:0] a_data, b_data, m_data;
wire [7:0] m_addr;
TopModule dut(.clk(clk),.rst(rst),
.a_req_i(a_req),.a_addr_i(a_addr),.a_ack_o(a_ack),.a_data_o(a_data),
.b_req_i(b_req),.b_addr_i(b_addr),.b_ack_o(b_ack),.b_data_o(b_data),
.m_req_o(m_req),.m_addr_o(m_addr),.m_data_i(m_data));
// memory: 2-cycle latency. capture addr when m_req, present data 2 cycles later.
reg [7:0] pa1, pa2; reg v1, v2;
reg [15:0] mem_data;
assign m_data = mem_data;
always @(posedge clk) begin
// pipeline: m_req at E+1 -> data at E+3 (2 cycle later)
v1 <= m_req; pa1 <= m_addr;
v2 <= v1; pa2 <= pa1;
end
always @(*) mem_data = pa2 ^ 16'hA500; // deterministic function of addr
always #5 clk = ~clk;
integer cyc=0;
always @(posedge clk) cyc <= cyc+1;
task step; begin @(posedge clk); #1; end endtask
initial begin
// reset
@(posedge clk); #1; rst=0;
// --- Test 1: cold A alone ---
a_addr=8'h11; a_req=1;
// wait for a_ack
begin : w1 integer i;
for(i=0;i<20;i=i+1) begin
@(posedge clk); #1;
if(a_ack) begin
$display("T1 A ack at cyc=%0d data=%h (exp %h)", cyc, a_data, (8'h11 ^ 16'hA500));
disable w1;
end
end
end
a_req=0;
repeat(8) step;
// --- Test 2: both request, expect A then B ---
a_addr=8'h22; b_addr=8'h33; a_req=1; b_req=1;
begin : w2 integer i; integer sawA; integer sawB;
sawA=0; sawB=0;
for(i=0;i<40;i=i+1) begin
@(posedge clk); #1;
if(a_ack) begin $display("T2 A ack cyc=%0d data=%h (exp %h)", cyc, a_data, (8'h22^16'hA500)); sawA=1; end
if(b_ack) begin $display("T2 B ack cyc=%0d data=%h (exp %h)", cyc, b_data, (8'h33^16'hA500)); sawB=1; end
if(sawA && sawB) disable w2;
end
end
a_req=0; b_req=0;
repeat(10) step;
// --- Test 3: cold B alone (A idle) ---
b_addr=8'h44; b_req=1;
begin : w3 integer i;
for(i=0;i<20;i=i+1) begin
@(posedge clk); #1;
if(b_ack) begin $display("T3 B ack cyc=%0d data=%h (exp %h)", cyc, b_data, (8'h44^16'hA500)); disable w3; end
if(a_ack) $display("T3 UNEXPECTED A ack cyc=%0d", cyc);
end
end
b_req=0;
repeat(5) step;
$display("DONE");
$finish;
end
endmodule
EOF
iverilog -g2012 -o /tmp/tb.out /tmp/dut.out.nonexist 2>/dev/null; iverilog -g2012 -o /tmp/tb.out /app/dut.sv /tmp/tb.sv && vvp /tmp/tb.outT1 A ack at cyc=7 data=a511 (exp a511) T2 A ack cyc=21 data=a522 (exp a522) T2 B ack cyc=26 data=a533 (exp a533) T3 B ack cyc=42 data=a544 (exp a544) DONE /tmp/tb.sv:76: $finish called at 466 (1s) [stdout] T1 A ack at cyc=7 data=a511 (exp a511) T2 A ack cyc=21 data=a522 (exp a522) T2 B ack cyc=26 data=a533 (exp a533) T3 B ack cyc=42 data=a544 (exp a544) DONE /tmp/tb.sv:76: $finish called at 466 (1s)
Test sustained alternation under continuous demand
cat > /tmp/tb2.sv <<'EOF'
module tb;
reg clk=0, rst=1;
reg a_req=0; reg [7:0] a_addr=8'h22;
reg b_req=0; reg [7:0] b_addr=8'h33;
wire a_ack,b_ack,m_req; wire [15:0] a_data,b_data,m_data; wire [7:0] m_addr;
TopModule dut(.clk(clk),.rst(rst),.a_req_i(a_req),.a_addr_i(a_addr),.a_ack_o(a_ack),.a_data_o(a_data),
.b_req_i(b_req),.b_addr_i(b_addr),.b_ack_o(b_ack),.b_data_o(b_data),.m_req_o(m_req),.m_addr_o(m_addr),.m_data_i(m_data));
reg [7:0] pa1,pa2; reg v1,v2; reg [15:0] mem_data; assign m_data=mem_data;
always @(posedge clk) begin v1<=m_req; pa1<=m_addr; v2<=v1; pa2<=pa1; end
always @(*) mem_data = pa2 ^ 16'hA500;
always #5 clk=~clk;
integer cyc=0; always @(posedge clk) cyc<=cyc+1;
integer i;
initial begin
@(posedge clk);#1;rst=0;
a_req=1;b_req=1; // both hold forever
for(i=0;i<60;i=i+1) begin
@(posedge clk);#1;
if(a_ack) $display("A ack cyc=%0d",cyc);
if(b_ack) $display("B ack cyc=%0d",cyc);
if(a_ack&&b_ack) $display("ERROR both ack same cycle");
end
$finish;
end
endmodule
EOF
iverilog -g2012 -o /tmp/tb2.out /app/dut.sv /tmp/tb2.sv && vvp /tmp/tb2.outA ack cyc=7 B ack cyc=12 A ack cyc=17 B ack cyc=22 A ack cyc=27 B ack cyc=32 A ack cyc=37 B ack cyc=42 A ack cyc=47 B ack cyc=52 A ack cyc=57 /tmp/tb2.sv:23: $finish called at 606 (1s) [stdout] A ack cyc=7 B ack cyc=12 A ack cyc=17 B ack cyc=22 A ack cyc=27 B ack cyc=32 A ack cyc=37 B ack cyc=42 A ack cyc=47 B ack cyc=52 A ack cyc=57 /tmp/tb2.sv:23: $finish called at 606 (1s)
No file changes, the agent left the workspace untouched.
TEST dut_present: PASS (/app/dut.sv exists)
TEST dut_forbidden: PASS (no forbidden constructs)
TEST dut_compiles: PASS (compiled with held-back reference/testbench)
TEST simulation_completed: PASS (Mismatches: 2533 in 3839 samples)
TEST reference_equivalence: FAIL (2533 mismatches in 3839 samples)
{"score": 0.000000, "results_file": "/tmp/h2t-grader-home.sBtyRj/runtime/cb_verifier_324-25617-11443-27653_324/results.jsonl"}Reproduce this trial: git checkout 2f94510 && PYTHONPATH=src python3 scripts/build_site.py , then open trial/trial_bb09ba9e14694a00. Re-running the agent live requires EVAL_PLATFORM_ENABLE_OAUTH_SMOKE=1 and is non-deterministic.
Trial trial_bb09ba9e14694a00 · verifier authoritative; classifier explanatory.