I want to randomize a variable “a” such that even if I randomize this 2 times or more, I should get atleast 1 “maxval” and 1 “minval”.
For ex.
define aint 4 define bint 10
I want to randomize variable a only on the basis of aint (i.e only 4 times) and I am required that I should get atleast one "0" and one "10" (depending on the value of bint) and the rest two values of a can be between 0 and 10.
Please help.
In reply to Prat_0693:
The issue I see is that there is a sequence flow in your requirements.
Below is a solution based on my understanding of your requirements. Perhaps this can guide you into the approach you need.
import uvm_pkg::*; `include "uvm_macros.svh"
class C;
/* I want to randomize a variable "a" such that even if I randomize this 2 times or more,
* I should get atleast 1 "maxval" and 1 "minval".
For ex. `define aint 4 `define 10 10
I want to randomize variable a only on the basis of `aint (i.e only 4 times)
and I am required that I should get atleast one "0" and one "10"
(depending on the value of `10) and the rest two values of a can be between 0 and 10.
[Ben] Not clear requirements. Let me assume th following requirements:
1) within aint (e.g., 4) randomize calls, and within those 4 times,
2) there should be at least one 0 and one 10 */
// `define aint 4
// `define 10 10
int count;
bit found_min;
bit found_max;
rand int unsigned a;
function void do_randomize();
case (count)
0, 1 : begin :a01
count += 1'b1;
if (!randomize(a) with {a >=0; a<11;}) `uvm_error("MYERR", "This is a randomize error")
if(a==0) found_min=1'b1;
if(a==10) found_max=1'b1;
end :a01
2,3 : begin :a23
if(!found_min && !found_max) begin
if (!randomize(a) with
{a dist {0:=1, 10:=1};
}) `uvm_error("MYERR", "This is a randomize error")
if(a==0) found_min=1'b1;
if(a==10) found_max=1'b1;
end
else if(found_min && !found_max) begin
if (!randomize(a) with
{a dist {0:=0, 10:=1};
}) `uvm_error("MYERR", "This is a randomize error")
//if(a==0) found_min=1'b1;
if(a==10) found_max=1'b1;
end
else if(found_min && !found_max) begin
if (!randomize(a) with
{a dist {0:=1, 10:=0};
}) `uvm_error("MYERR", "This is a randomize error")
if(a==0) found_min=1'b1;
//if(a==10) found_max=1'b1;
end
else begin :a23e
if (!randomize(a) with
{ a dist {1'b1:=1, 1'b0:=3};
}) `uvm_error("MYERR", "This is a randomize error")
if(count !=3) begin
if(a==0) found_min=1'b1;
if(a==10) found_max=1'b1;
count += 1'b1;
end
else begin
count=0;
found_min=1'b0;
found_max=1'b0;
end
end :a23e
end :a23
default : $display("error in case");
endcase
endfunction :do_randomize
endclass
module top;
timeunit 1ns; timeprecision 100ps;
bit clk;
int a;
C c;
initial forever #10 clk=!clk;
initial begin
c=new();
repeat(200) begin
@(posedge clk);
c.do_randomize();
a=c.a;
$display("a %d, count %d, found_min %b, found_max %b", c.a, c.count, c.found_min, c.found_max);
end
$stop;
end
endmodule
# a 3, count 1, found_min 0, found_max 0
# a 6, count 2, found_min 0, found_max 0
# a 10, count 2, found_min 0, found_max 1
# a 0, count 3, found_min 1, found_max 1
# a 0, count 0, found_min 0, found_max 0
# a 6, count 1, found_min 0, found_max 0
# a 3, count 2, found_min 0, found_max 0
# a 0, count 2, found_min 1, found_max 0
# a 10, count 2, found_min 1, found_max 1
# a 1, count 3, found_min 1, found_max 1
# a 0, count 0, found_min 0, found_max 0
# a 6, count 1, found_min 0, found_max 0
# a 2, count 2, found_min 0, found_max 0
# a 0, count 2, found_min 1, found_max 0
# a 10, count 2, found_min 1, found_max 1
# a 0, count 3, found_min 1, found_max 1
# a 1, count 0, found_min 0, found_max 0
# a 8, count 1, found_min 0, found_max 0
# a 10, count 2, found_min 0, found_max 1
# a 1, count 3, found_min 0, found_max 1
# a 0, count 0, found_min 0, found_max 0
# a 6, count 1, found_min 0, found_max 0
# a 4, count 2, found_min 0, found_max 0
# a 0, count 2, found_min 1, found_max 0
# a 10, count 2, found_min 1, found_max 1
Ben Cohen
http://www.systemverilog.us/ ben@systemverilog.us
For training, consulting, services: contact Home - My cvcblr
In reply to ben@SystemVerilog.us:
Ben’s solution doesn’t not take int account that the min and max values need to be seen by aint number of attempts (Prat_0693, it would help to use more descriptive variable names, like count for aint, and max_value for bint).
The easiest thing to do would be to generate the numbers in advance by putting them into a list.
class numbers;
int count=4;
int max_value=10;
rand int list[];
constraint c_range {foreach(list[ii]) list[ii] inside {[0:max_value]};}
function void pre_randomize(); list = new[count]; endfunction
function void post_randomize();
list.sort();
if (list[0] != 0) list[0] = 0;
if (list[count-1] != max_value) list[count-1] = max_value;
list.shuffle();
endfunction
endclass
In reply to Prat_0693:
Here is a version to use randc cyclic random constraint.
import uvm_pkg::*;
`include "uvm_macros.svh"
`define aint 4
`define amax 10
class my_class extends uvm_object;
randc int a;
constraint a_range {a inside {0,`amax, `amax+1, `amax+2};}
rand int unsigned c, d;
constraint c_d_range { c inside {[1:`amax-1]};
d inside {[1:`amax-1]};
}
function void post_randomize();
case(a)
`amax+1: a = c;
`amax+2: a = d;
default: begin end //Do nothting
endcase
endfunction
endclass
module tb ();
my_class my_obj;
initial begin
my_obj = new();
for(int i=0; i< `aint*4; i++) begin
void'(my_obj.randomize());
$display("a%0d = %-0d", i%`aint, my_obj.a);
end
end
endmodule
simulation result as below:
a0 = 10
a1 = 0
a2 = 8
a3 = 6
a0 = 10
a1 = 9
a2 = 5
a3 = 0
a0 = 6
a1 = 10
a2 = 0
a3 = 5
a0 = 4
a1 = 10
a2 = 0
a3 = 7
In reply to Lina.Lin:
That is a clever solution using the randc. I like it!
Ben