I am getting an odd issue in ModelSim where I set an input variable to a random value in a range, but for some reason, I get a value outside of the range. All my code is included below but the essential line is:
write_addrs[i] = $urandom_range(1,NUM_ARCH_REGS);
In ModelSim, it is being assigned to 0 when it shouldn't (as shown in the waveform; the highlighted signal)...
The thing that is confounding me is that I don't ever set the write_adresses to zero except for when I set the initial signals in the INITIAL_VECTOR_VALUES block. I only modify the variable by using the $urandom_range function with the range explicitly excluding the number zero.
The main blocks of code in which I write to this variable are here:
initial begin : INITIAL_VECTOR_VALUES
advance = 0;
checkpoint = 0;
recover = 0;
write_before_checkpoint = 0;
for (int i = 0; i < NUM_READ_PORTS; i++)
read_addrs[i] = 0;
for (int i = 0; i < NUM_WRITE_PORTS; i++) begin
write_addrs[i] = 0; //<--------------------- HERE!!!
wr_en[i] = 0;
write_data[i] = 0;
commit_en[i] = 0;
commit_data[i] = 0;
commit_addrs[i]= 0;
end
end
... and here:
task random_operations(int repeat_num);
//local vars
int operation_select, num_write, num_commit;
int current_checkpoints;
int loop_idx;
##5;
current_checkpoints = 0; //initialize
$display("Begin Random Operations # %0t", $time());
while (loop_idx < repeat_num) begin
... other stuff ...
//operand select (sets the stimulus inputs)
for (int k = 0; k < num_write; k++) begin
write_addrs[k] = $urandom_range(1,NUM_ARCH_REGS); //<--------------------- HERE!!!
$display("%0t: num_write = %0d",$time(), num_write);
$display("%0t: write_addrs[%0d] = %0d", $time(), k, write_addrs[k]);
write_data[k] = $urandom_range(1,128);
wr_en[k] = 1;
end
...
loop_idx++;
##1;
//reset signals (reset stimulus inputs)
...
end : end_while
endtask : random_operations
Does anyone know why this would be happening?
REFERENCE CODE
`timescale 1ns/1ns
module testbench;
localparam int NUM_CHECKPOINTS = 8;
localparam int NUM_ARCH_REGS = 32;
localparam int NUM_READ_PORTS = 4;
localparam int NUM_WRITE_PORTS = 2;
logic clk;
logic rst;
initial begin : CLOCK_INIT
clk = 1'b0;
forever #5 clk = ~clk;
end
default clocking tb_clk #(posedge clk); endclocking
logic [$clog2(32)-1:0] read_addrs [4];
logic [$clog2(32)-1:0] write_addrs [2];
logic wr_en [2];
logic advance; //moves tail pointer forward
logic checkpoint; //moves head pointer forward
logic recover; //moves head pointer backward (to tail)
logic write_before_checkpoint;
logic [$clog2(32)-1:0] commit_addrs [2];
logic [$clog2(128)-1:0] commit_data [2];
logic commit_en [2];
logic [$clog2(128)-1:0] write_data [2];
logic [$clog2(128)-1:0] read_data [4];
logic [$clog2(128)-1:0] write_evict_data [2];
logic enable_assertions;
cfc_rat dut(.*);
shadow_rat rat_monitor(.*);
initial begin : INITIAL_VECTOR_VALUES
advance = 0;
checkpoint = 0;
recover = 0;
write_before_checkpoint = 0;
for (int i = 0; i < NUM_READ_PORTS; i++)
read_addrs[i] = 0;
for (int i = 0; i < NUM_WRITE_PORTS; i++) begin
write_addrs[i] = 0;
wr_en[i] = 0;
write_data[i] = 0;
commit_en[i] = 0;
commit_data[i] = 0;
commit_addrs[i]= 0;
end
end
task reset();
rst = 1;
##2;
rst = 0;
##1;
endtask : reset
task random_operations(int repeat_num);
//local vars
int operation_select, num_write, num_commit;
int current_checkpoints;
int loop_idx;
##5;
current_checkpoints = 0; //initialize
$display("Begin Random Operations # %0t", $time());
while (loop_idx < repeat_num) begin
operation_select = (loop_idx < 5) ? 1 : ((dut.dfa.chkpt_empty) ? $urandom_range(0,1) : ((dut.dfa.chkpt_full) ? 1 : $urandom_range(0,2)));
num_write = $urandom_range(0,NUM_WRITE_PORTS);
num_commit = $urandom_range(0,NUM_WRITE_PORTS);
case (operation_select)
0: begin //checkpoint
if (current_checkpoints+1 < NUM_CHECKPOINTS) begin
$display("Checkpoint # %0t", $time());
write_before_checkpoint = $urandom_range(0,1);
checkpoint = 1;
current_checkpoints++;
end
else begin
loop_idx--;
continue;
end
end
1: $display("Normal RW # %0t",$time()); //no operation, only read and write
2: begin //advance
if (current_checkpoints > 0) begin
advance = 1;
$display("Advance # %0t", $time());
current_checkpoints--;
end
else begin
loop_idx--;
continue;
end
end
3: begin //recover
$display("Recover # %0t", $time());
recover = 1;
current_checkpoints = 0;
end
default:;
endcase // operation_select
//operand select (sets the stimulus inputs)
for (int k = 0; k < NUM_READ_PORTS; k++)
read_addrs[k] = $urandom_range(0,NUM_ARCH_REGS);
for (int k = 0; k < num_write; k++) begin
write_addrs[k] = $urandom_range(1,NUM_ARCH_REGS);
$display("%0t: num_write = %0d",$time(), num_write);
$display("%0t: write_addrs[%0d] = %0d", $time(), k, write_addrs[k]);
write_data[k] = $urandom_range(1,128);
wr_en[k] = 1;
end
for (int k = 0; k < num_commit; k++) begin
commit_addrs[k] = $urandom_range(1,NUM_ARCH_REGS);
commit_data[k] = $urandom_range(1,128);
commit_en[k] = 1;
end
loop_idx++;
##1;
//reset signals (reset stimulus inputs)
checkpoint = 0;
recover = 0;
advance = 0;
write_before_checkpoint = 0;
for (int i = 0; i < NUM_WRITE_PORTS; i++) begin
write_data[i] = 0;
wr_en[i] = 0;
end
for (int i = 0; i < NUM_READ_PORTS; i++)
read_addrs[i] = 0;
for (int i = 0; i < NUM_WRITE_PORTS; i++) begin
commit_en[i] = 0;
commit_data[i] = 0;
end
end : end_repeat
endtask : random_operations
initial begin : TEST_VECTORS
enable_assertions = 1; //for testing the monitor
reset();
random_operations(5000);
##10;
$display("Finished Successfuly! # %0t",$time());
$finish;
end
endmodule
The problem is that $urandom_range(1, NUM_ARCH_REGS) returns values from 1 to 32. But, write_addrs is declared as logic [4:0], which means it can only take on values from 0 to 31. When $urandom_range returns 32 (which is the same as 6'b10_000), the assignment in your code truncates it to 5 bits, dropping the MSB, and 5'b0_0000 is stored in write_addrs.
To fix this, only allow random values up to 31.
Change:
write_addrs[k] = $urandom_range(1, NUM_ARCH_REGS);
to:
write_addrs[k] = $urandom_range(1, NUM_ARCH_REGS-1);
Here is a complete example to demonstrate the problem:
module tb;
localparam int NUM_ARCH_REGS = 32;
logic [$clog2(32)-1:0] write_addrs [2];
initial begin
repeat (100) begin
for (int k=0; k<2; k++) begin
write_addrs[k] = $urandom_range(1, NUM_ARCH_REGS);
$write("write_addrs[%0d]=%02d ", k, write_addrs[k]);
end
$display;
end
end
endmodule
The problem you see is not specific to ModelSim; I am able to see it on 2 other simulators.
Related
I am trying to pass a reference array of variables. It works fine with a reference to variable, but not with an array of variables. The goal with the task is to be able to take an array of variables, and read them on every clock edge.
So this code does not work
module tb;
logic clock = 0;
logic a = 0;
logic b = 0;
task automatic read_vars(ref logic clock, input int clock_edges = 10,
const ref logic signal_array[]);
repeat (clock_edges) begin
#(posedge clock) $display("#TIME: %t Clock edge", $time);
for (int i = 0; i < signal_array.size(); i++) begin
$display("Variable %0d: %0b", i, signal_array[i]);
end
end
endtask
always begin
#1 clock = 1;
#1 clock = 0;
end
always begin
#3 b = 1;
#3 b = 0;
end
always begin
#7 a = 1;
#7 a = 0;
end
initial begin
fork
read_vars(.clock(clock), .signal_array({a, b}));
join_none
#1000;
$finish();
end
endmodule
I get the following error
read_vars(.clock(clock), .signal_array({a, b}));
|
xmvlog: *E,BADRFA (tb.sv,25|45): invalid ref argument usage because actual argument is not a variable. [SystemVerilog].
module worklib.tb:sv
But this code works.
module tb;
logic clock = 0;
logic a = 0;
logic b = 0;
task automatic read_vars(ref logic clock, ref logic a, ref logic b, input int clock_edges = 10);
repeat (clock_edges) begin
#(posedge clock) begin
$display("#TIME: %t Clock edge", $time);
$display("a = %b ", a);
$display("b = %b ", b);
end
end
endtask
always begin
#1 clock = 1;
#1 clock = 0;
end
always begin
#3 b = 1;
#3 b = 0;
end
always begin
#7 a = 1;
#7 a = 0;
end
initial begin
fork
read_vars(.clock(clock), .a(a), .b(b));
join_none
#1000;
$finish();
end
endmodule
What you are trying to do is impossible in verilog.
First of all, having a reference to an array will not help in solving the issue. Arrays contain values of something. So creation of an array with {a,b} will just copy values of the variables into the array and updating variables will not be reflected in any case.
What you are after is an array of references to variables, which is impossible in a verilog.
However, class variables are always reference. So, you can wrap your vars in a class in test bench. Here is a modified example of yours:
class V;
logic val;
endclass:V
module tb;
V a = new;
V b = new;
V arr[] = '{a, b};
logic clock = 0;
//logic a = 0;
//logic b = 0;
task automatic read_vars(ref logic clock, input int clock_edges = 10,
V signal_array[]);
repeat (clock_edges) begin
#(posedge clock) $display("#TIME: %t Clock edge", $time);
for (int i = 0; i < signal_array.size(); i++) begin
$display("Variable %0d: %0b", i, signal_array[i].val);
end
end
endtask
always begin
#1 clock = 1;
#1 clock = 0;
end
always begin
#3 b.val = 1;
#3 b.val = 0;
end
always begin
#7 a.val = 1;
#7 a.val = 0;
end
initial begin
fork
read_vars(.clock(clock), .signal_array(arr));
join_none
#1000;
$finish();
end
endmodule
`timescale 1ns / 1ps
module param_right_shifter
# (parameter N = 3)
(
input logic [$clog2(N)-1:0] a, // input
input logic [N-1:0] amt, // shift bits
output logic [$clog2(N)-1:0] y // output
);
logic [$clog2(N)-1:0][N:0] s;
logic [$clog2(N)-1:0] placeholder = a;
localparam bit_num = $clog2(N)-1;
always_comb
begin
for(int i = 0; i < N; i++)
begin
if (i == 0)
begin
s[i] = amt[i] ? {placeholder[i], placeholder[bit_num:2**i]} : placeholder;
placeholder = s[i];
end
else
begin
s[i] = amt[i] ? {placeholder[$clog2(N)-1:0], placeholder[bit_num:2**i]} : placeholder;
placeholder = s[i];
end
end
end
endmodule
I am having an issue with referencing the 'i' variable. It says that 'range must be bounded by constant expressions'. I am unsure of how to resolve.
Try below. I am assuming N is will have a constant value throughout the simulation.
Please note that placeholder is driven by all bits of s so here placeholder will settle to s[N-1].
genvar i;
generate
for(i = 0; i < N; i++)
begin
if (i == 0)
begin
always_comb
begin
s[i] = amt[i] ? {placeholder[i], placeholder[bit_num:2**i]} : placeholder;
placeholder = s[i];
end
end
else
begin
always_comb
begin
s[i] = amt[i] ? {placeholder[$clog2(N)-1:0], placeholder[bit_num:2**i]} : placeholder;
placeholder = s[i];
end
end
end
endgenerate
I am working on a problem that Given a string s, partitions s such that every substring of the partition is a palindrome.
Return the minimum cuts needed for a palindrome partitioning of s. The problem can also be found in here. https://oj.leetcode.com/problems/palindrome-partitioning-ii/
Version 1 is one version of solution I found online.
Version 2 is my code.
They both seem to work in very similar ways. However, with a reasonably large input, version 2 takes more than 6000 milliseconds whereas version 1 takes around 71 milliseconds.
Can anyone provide any idea where the time difference is from?
Version 1:
int minSol(string s) {
int len = s.size();
vector<int> D(len + 1);
vector<vector<int>> P;
for (int i = 0; i < len; i++){
vector<int> t(len);
P.push_back(t);
}
for (int i = 0; i <= len; i++)
D[i] = len - i;
for (int i = 0; i < len; i++)
for (int j = 0; j < len; j++)
P[i][j] = false;
for (int i = len - 1; i >= 0; i--){
for (int j = i; j < len; j++){
if (s[i] == s[j] && (j - i < 2 || P[i + 1][j - 1])){
P[i][j] = true;
D[i] = min(D[i], D[j + 1] + 1);
}
}
}
return D[0] - 1;
}
Version 2:
int minCut(string s) {
int size = s.size();
vector<vector<bool>> map;
for (int i = 0; i < size; i++){
vector<bool> t;
for (int j = 0; j < size; j++){
t.push_back(false);
}
map.push_back(t);
}
vector<int> minCuts;
for (int i = 0; i < size; i++){
map[i][i] = true;
minCuts.push_back(size - i - 1);
}
for (int i = size - 1; i >= 0; i--){
for (int j = size - 1; j >= i; j--){
if (s[i] == s[j] && (j - i <= 1 || map[i + 1][j - 1])){
map[i][j] = true;
if (j == size - 1){
minCuts[i] = 0;
}else if (minCuts[i] > minCuts[j + 1] + 1){
minCuts[i] = minCuts[j + 1] + 1;
}
}
}
}
return minCuts[0];
}
I would guess it's because in the second version you're doing size^2 push_back's, whereas in the first version you're just doing size push_back's.
I want to generate the random numbers using this loop. When i runs the apps at everytime, i want to generate the random numbers without duplicates.
Eg:
for(int i = 0; i < 5; i++)
{
// int d = random() % i;
NSLog(#"The Value %d",i);
NSLog(#"The random Number %d",i);
}
Actual Number Random Number
1 4
2 5
3 2
4 1
5 3
It's Random Permutation Generation problem. Read this: http://www.techuser.net/randpermgen.html
The main idea is (in pseudo code):
for (i=1 to n) ar[i] = i;
for (i=1 to n) swap(ar[i], ar[Random(i,n)]);
In your case:
int ar[5],i,d,tmp;
for(i = 0; i < 5; i++) ar[i] = i+1;
for(i = 0; i < 5; i++) {
d = i + (random()%(5-i));
tmp = ar[i];
ar[i] = ar[d];
ar[d] = tmp;
NSLog(#"%d",ar[i]);
}
Can be something like this,
int rand[5] = {0};
int max = 5;
for(int i = 0; i < max; i++){
int r = random() % max + 1;
while([self foundNumber:r inArray:rand limit:i){
r = random() % max + 1;
}
rand[i] = r;
}
- (BOOL) foundNumber:r inArray:rand limit:l {
for(int i = 0; i < l; i++){
if(rand[i] == r) return YES;
}
return NO;
}
main.m
counter = 1;
n = 8;
board = zeros(1,n);
back(0, board);
disp(counter);
sol.m
function value = sol(board)
for ( i = 1:(length(board)))
for ( j = (i+1): (length(board)-1))
if (board(i) == board(j))
value = 0;
return;
end
if ((board(i) - board(j)) == (i-j))
value = 0;
return;
end
if ((board(i) - board(j)) == (j-i))
value = 0;
return;
end
end
end
value = 1;
return;
back.m
function back(depth, board)
disp(board);
if ( (depth == length(board)) && (sol2(board) == 1))
counter = counter + 1;
end
if ( depth < length(board))
for ( i = 0:length(board))
board(1,depth+1) = i;
depth = depth + 1;
solv2(depth, board);
end
end
I'm attempting to find the maximum number of ways n-queen can be placed on an n-by-n board such that those queens aren't attacking eachother. I cannot figure out the problem with the above matlab code, i doubt it's a problem with my logic since i've tested out this logic in java and it seems to work perfectly well there. The code compiles but the issue is that the results it produces are erroneous.
Java Code which works:
public static int counter=0;
public static boolean isSolution(final int[] board){
for (int i = 0; i < board.length; i++) {
for (int j = i + 1; j < board.length; j++) {
if (board[i] == board[j]) return false;
if (board[i]-board[j] == i-j) return false;
if (board[i]-board[j] == j-i) return false;
}
}
return true;
}
public static void solve(int depth, int[] board){
if (depth == board.length && isSolution(board)) {
counter++;
}
if (depth < board.length) { // try all positions of the next row
for (int i = 0; i < board.length; i++) {
board[depth] = i;
solve(depth + 1, board);
}
}
}
public static void main(String[] args){
int n = 8;
solve(0, new int[n]);
System.out.println(counter);
}
Worked code:
function queen
clc;
counter = 0;
n = 8;
board = zeros(1,n);
[board,counter] = back(1, board,counter);
fprintf('Solution count: %d\n',counter);
%%
function value = isSolution(board)
for i = 1:length(board)
for j = (i+1): length(board)
if abs(board(i) - board(j)) == abs(i-j)
value = false;
return;
end
end
end
value = true;
%%
function [board,counter] = back(depth, board,counter)
if (depth == length(board)+1) && isSolution(board)
counter = counter + 1;
disp(board);
end
if ( depth <= length(board))
for i = 1:length(board)
if ~any(board==i)
board(1,depth) = i;
[~,counter] = back(depth+1, board,counter);
end
end
end
I add line if ~any(board==i), without this check, I think your java solution slower than this Matlab code. For fastest solution google "Dancing links".
There are many problems with your code.
Here are just a few:
you initialize board as 1-by-8 array
you call functions sol2 and solv2 that are undefined
no output is captured for solv2, or back (remember, Matlab passes variables by value, not by reference)
there are no comments in the code that would explain what you think you're doing and why you'd want to do that.
Also: While Matlab has a JIT compiler that, among others, helps speed up loops, Matlab code can't be said to "compile" (unless you're doing something dramatically wrong).