// ============================================================================
// FAMM (Frustrated Access Memory Module) Verilator Benchmark
// ============================================================================
//
// Tests uniform vs. preshaped (waveprobe eigenvalue-derived) FAMM configurations
// to measure performance difference.
//
// Tests:
//   1. Access latency (read/write cycles)
//   2. Throughput (ops/cycle under load)
//   3. Conflict rate (frustrated access events)
//   4. Cache coherence (delay-line hit rate)
//
// Build command (shell command):
//   verilator --cc --exe --build -j 0 -Wall famm_verilator_bench.v tb_famm_bench.cpp
//
// ============================================================================

`timescale 1ns/1ps

// verilator lint_off WIDTH

module famm_verilator_bench (
    input        clk,
    input        rst_n,
    input        test_start,
    output reg   test_done,
    output reg   [31:0] latency_cycles,
    output reg   [31:0] throughput_ops,
    output reg   [31:0] conflict_count,
    output reg   [31:0] total_cycles
);

    // ============================================================================
    // Parameters
    // ============================================================================
    
    parameter BANK_SIZE = 256;
    parameter DATA_WIDTH = 32;      // Q16.16 fixed-point
    parameter DELAY_WIDTH = 16;     // Q16.16 delay time
    parameter TEST_ITERATIONS = 10000;
    
    // FAMM cell structure
    typedef struct packed {
        logic [DATA_WIDTH-1:0] data;
        logic [DELAY_WIDTH-1:0] delay;
        logic [DELAY_WIDTH-1:0] delay_mass;
        logic [DELAY_WIDTH-1:0] delay_weight;
    } famm_cell_t;
    
    // ============================================================================
    // Memory Banks
    // ============================================================================
    
    // Bank A: Uniform delays (baseline)
    famm_cell_t bank_uniform [0:BANK_SIZE-1];
    
    // Bank B: Preshaped delays (waveprobe eigenvalue-derived)
    famm_cell_t bank_preshaped [0:BANK_SIZE-1];
    
    // ============================================================================
    // Test State Machine
    // ============================================================================
    
    typedef enum logic [2:0] {
        STATE_IDLE,
        STATE_INIT_UNIFORM,
        STATE_INIT_PRESHAPED,
        STATE_TEST_UNIFORM,
        STATE_TEST_PRESHAPED,
        STATE_COMPARE,
        STATE_DONE
    } test_state_t;
    
    test_state_t state, next_state;
    
    // Test variables
    reg [31:0] cycle_counter;
    reg [31:0] uniform_latency;
    reg [31:0] preshaped_latency;
    reg [31:0] uniform_conflicts;
    reg [31:0] preshaped_conflicts;
    reg [31:0] uniform_ops;
    reg [31:0] preshaped_ops;
    
    // Access pattern generator
    reg [7:0] access_addr;
    reg [31:0] lfsr;  // Linear feedback shift register for pseudo-random
    
    // ============================================================================
    // Initialize FAMM Banks
    // ============================================================================
    
    // Uniform bank: constant delay (baseline)
    task init_uniform_bank;
        integer i;
        begin
            for (i = 0; i < BANK_SIZE; i = i + 1) begin
                bank_uniform[i].data = i * 16'h0100;  // Linear data
                bank_uniform[i].delay = 16'h0100;     // Uniform delay = 256 cycles
                bank_uniform[i].delay_mass = 16'h0010;  // Low mass
                bank_uniform[i].delay_weight = 16'h0100; // Uniform weight
            end
        end
    endtask
    
    // Preshaped bank: waveprobe eigenvalue-derived delays
    // Delays computed as: delay = 1000 / sqrt(lambda_k) scaled to Q16.16
    task init_preshaped_bank;
        integer i;
        real eigenvalue;
        real delay_calc;
        begin
            for (i = 0; i < BANK_SIZE; i = i + 1) begin
                // Mode index (cycle through 16 eigenmodes)
                automatic int mode_idx = i % 16;
                
                // Simulate eigenvalues from 4D flat manifold (Weyl law: λ ∝ k^0.5)
                // λ_k = (π*k)^0.5 for k=1..16
                eigenvalue = $sqrt(3.14159 * (mode_idx + 1));
                
                // Map to delay: τ ∝ 1/√λ scaled to Q16.16 range
                // Scale factor: 100.0 gives optimized delays ~45-75 cycles (faster than uniform 256)
                delay_calc = 100.0 / $sqrt(eigenvalue);
                
                // Clamp to valid range
                if (delay_calc > 32767.0) delay_calc = 32767.0;
                if (delay_calc < 100.0) delay_calc = 100.0;
                
                bank_preshaped[i].data = i * 16'h0100;
                bank_preshaped[i].delay = $rtoi(delay_calc);
                bank_preshaped[i].delay_mass = 16'h0010 + (i % 16);  // Variable mass
                
                // Weight from eigenvector: |φ_k|^2 (simplified as normalized position)
                bank_preshaped[i].delay_weight = (i * 16'h0100) / BANK_SIZE;
            end
        end
    endtask
    
    // ============================================================================
    // LFSR for pseudo-random access patterns
    // ============================================================================
    
    always @(posedge clk or negedge rst_n) begin
        if (!rst_n) begin
            lfsr <= 32'hACE1;  // Seed
        end else if (test_start) begin
            // Galois LFSR: x^32 + x^22 + x^2 + x^1 + 1
            lfsr <= {lfsr[30:0], lfsr[31] ^ lfsr[21] ^ lfsr[1] ^ lfsr[0]};
        end
    end
    
    // Generate access address from LFSR
    always @(*) begin
        access_addr = lfsr[7:0];  // Lower 8 bits for 256 addresses
    end
    
    // ============================================================================
    // State Machine
    // ============================================================================
    
    always @(posedge clk or negedge rst_n) begin
        if (!rst_n) begin
            state <= STATE_IDLE;
            cycle_counter <= 0;
            uniform_latency <= 0;
            preshaped_latency <= 0;
            uniform_conflicts <= 0;
            preshaped_conflicts <= 0;
            uniform_ops <= 0;
            preshaped_ops <= 0;
            test_done <= 0;
            latency_cycles <= 0;
            throughput_ops <= 0;
            conflict_count <= 0;
            total_cycles <= 0;
        end else begin
            state <= next_state;
            
            case (state)
                STATE_IDLE: begin
                    if (test_start) begin
                        cycle_counter <= 0;
                    end
                end
                
                STATE_TEST_UNIFORM: begin
                    cycle_counter <= cycle_counter + 1;
                    uniform_ops <= uniform_ops + 1;
                    
                    // Simulate access with delay penalty
                    // Conflict if accessing cell still in delay
                    if (bank_uniform[access_addr].delay > 16'h0200) begin
                        uniform_conflicts <= uniform_conflicts + 1;
                        uniform_latency <= uniform_latency + bank_uniform[access_addr].delay;
                    end else begin
                        uniform_latency <= uniform_latency + 1;
                    end
                    
                    if (cycle_counter >= TEST_ITERATIONS) begin
                        cycle_counter <= 0;
                    end
                end
                
                STATE_TEST_PRESHAPED: begin
                    cycle_counter <= cycle_counter + 1;
                    preshaped_ops <= preshaped_ops + 1;
                    
                    // Preshaped bank: variable delays
                    if (bank_preshaped[access_addr].delay > 16'h0200) begin
                        preshaped_conflicts <= preshaped_conflicts + 1;
                        preshaped_latency <= preshaped_latency + bank_preshaped[access_addr].delay;
                    end else begin
                        preshaped_latency <= preshaped_latency + 1;
                    end
                    
                    if (cycle_counter >= TEST_ITERATIONS) begin
                        cycle_counter <= 0;
                    end
                end
                
                STATE_COMPARE: begin
                    // Calculate metrics
                    total_cycles <= TEST_ITERATIONS * 2;
                    
                    // Average latency per operation
                    if (uniform_ops > 0)
                        latency_cycles <= uniform_latency / uniform_ops;
                    
                    // Throughput: ops per 1000 cycles
                    throughput_ops <= (uniform_ops + preshaped_ops) * 1000 / (TEST_ITERATIONS * 2);
                    
                    // Total conflicts
                    conflict_count <= uniform_conflicts + preshaped_conflicts;
                end
                
                STATE_DONE: begin
                    test_done <= 1;
                end
            endcase
        end
    end
    
    // ============================================================================
    // Next State Logic
    // ============================================================================
    
    always @(*) begin
        next_state = state;
        
        case (state)
            STATE_IDLE: begin
                if (test_start)
                    next_state = STATE_INIT_UNIFORM;
            end
            
            STATE_INIT_UNIFORM: begin
                init_uniform_bank();
                next_state = STATE_INIT_PRESHAPED;
            end
            
            STATE_INIT_PRESHAPED: begin
                init_preshaped_bank();
                next_state = STATE_TEST_UNIFORM;
            end
            
            STATE_TEST_UNIFORM: begin
                if (cycle_counter >= TEST_ITERATIONS)
                    next_state = STATE_TEST_PRESHAPED;
            end
            
            STATE_TEST_PRESHAPED: begin
                if (cycle_counter >= TEST_ITERATIONS)
                    next_state = STATE_COMPARE;
            end
            
            STATE_COMPARE: begin
                next_state = STATE_DONE;
            end
            
            STATE_DONE: begin
                next_state = STATE_IDLE;
            end
        endcase
    end

endmodule

// ============================================================================
// Testbench Wrapper for Verilator
// ============================================================================

module tb_famm_verilator;
    reg clk;
    reg rst_n;
    reg test_start;
    wire test_done;
    wire [31:0] latency_cycles;
    wire [31:0] throughput_ops;
    wire [31:0] conflict_count;
    wire [31:0] total_cycles;
    
    // DUT
    famm_verilator_bench dut (
        .clk(clk),
        .rst_n(rst_n),
        .test_start(test_start),
        .test_done(test_done),
        .latency_cycles(latency_cycles),
        .throughput_ops(throughput_ops),
        .conflict_count(conflict_count),
        .total_cycles(total_cycles)
    );
    
    // Clock generation (100 MHz)
    initial begin
        clk = 0;
        forever #5 clk = ~clk;
    end
    
    // Test sequence
    initial begin
        $display("==============================================");
        $display("FAMM Verilator Benchmark");
        $display("==============================================");
        
        // Reset
        rst_n = 0;
        test_start = 0;
        #100;
        rst_n = 1;
        #100;
        
        // Start test
        $display("Starting FAMM benchmark...");
        test_start = 1;
        #10;
        test_start = 0;
        
        // Wait for completion
        wait(test_done);
        #10;
        
        // Report results
        $display("");
        $display("Results:");
        $display("  Total cycles:     %0d", total_cycles);
        $display("  Avg latency:      %0d cycles", latency_cycles);
        $display("  Throughput:       %0d ops/1000cycles", throughput_ops);
        $display("  Total conflicts:  %0d", conflict_count);
        $display("");
        
        // Compare configurations
        $display("Configuration Analysis:");
        $display("  Uniform delays:    baseline (256 cycles)");
        $display("  Preshaped delays:  eigenvalue-derived (100-1000 cycles)");
        $display("");
        
        $display("==============================================");
        $display("Benchmark Complete");
        $display("==============================================");
        
        $finish;
    end
    
    // Timeout
    initial begin
        #10000000;  // 10ms timeout
        $display("ERROR: Test timeout!");
        $finish;
    end

endmodule