Hi,
I wanted to generate 8 4 bit random numbers cyclic in nature.
I wrote following code.
module rand1;
class expt;
randc bit [3:0] a[0:7];
endclass
initial begin
expt e1 = new();
foreach(e1.a[i]) begin
e1.randomize();
$display("a[%d]=%d\n",i,e1.a[i]);
end
end
endmodule
What I am getting is this.6 is repeated. Looks like cyclic random numbers are not getting generated. Please help.
a[ 0]= 6
a[ 1]= 3
a[ 2]=11
a[ 3]= 0
a[ 4]=15
a[ 5]=12
a[ 6]= 6
a[ 7]=11
In reply to suyog_asic:
Randc can’t be used in that way for array to get unique elements.
LRM said:
Arrays can be declared rand or randc, in which case all of their member elements are treated as rand or randc.
You should use rand with unique constraint (move the randomize statement outside of the loop):
module rand1;
class expt;
rand bit [3:0] a[0:7];
constraint c_unique{
unique{a};
}
endclass
initial begin
expt e1 = new();
e1.randomize();
foreach(e1.a[i]) begin
$display("a[%0d] = %0d",i ,e1.a[i]);
end
end
endmodule
Noted: unique constraint is very expensive, it is difficult to be solved. SV will take very long time to solve unique constraint for big array size.
In reply to chris_le:
Thats a great input Chris. Thanks a lot.
Yes thats right, every element is randc itself but not with each other.
I modified my code and saw the behavior you mentioned.
module rand1;
class expt;
randc bit [3:0] a[0:7];
endclass
initial begin
expt e1 = new();
foreach(e1.a[m] ) begin
for(int i = 0;i<16;i++) begin
e1.randomize();
$display(“a[%d]=%d”,m,e1.a[m]);
end
end
end
endmodule
I am getting output like this. Every element of array is random cyclic.
a[ 0]= 6
a[ 0]=14
a[ 0]= 7
a[ 0]= 8
a[ 0]= 1
a[ 0]= 0
a[ 0]= 3
a[ 0]=11
a[ 0]= 2
a[ 0]=15
a[ 0]=12
a[ 0]= 4
a[ 0]= 9
a[ 0]= 5
a[ 0]=10
a[ 0]=13
a[ 1]=13
a[ 1]= 3
a[ 1]=14
a[ 1]=10
a[ 1]=11
a[ 1]= 8
a[ 1]= 0
a[ 1]=12
a[ 1]= 4
a[ 1]= 5
a[ 1]= 9
a[ 1]= 1
a[ 1]= 2
a[ 1]= 6
a[ 1]= 7
a[ 1]=15
a[ 2]=14
a[ 2]= 9
a[ 2]= 4
a[ 2]=13
a[ 2]= 2
a[ 2]= 8
a[ 2]=11
a[ 2]= 1
a[ 2]= 0
a[ 2]=12
a[ 2]= 7
a[ 2]= 5
a[ 2]=15
a[ 2]= 3
a[ 2]= 6
a[ 2]=10
a[ 3]= 7
a[ 3]= 6
a[ 3]= 1
a[ 3]=15
a[ 3]=14
a[ 3]= 5
a[ 3]= 2
a[ 3]= 4
a[ 3]= 8
a[ 3]=12
a[ 3]= 9
a[ 3]=10
a[ 3]= 0
a[ 3]=13
a[ 3]=11
a[ 3]= 3
a[ 4]=11
a[ 4]=10
a[ 4]=13
a[ 4]= 3
a[ 4]= 5
a[ 4]=12
a[ 4]= 7
a[ 4]=14
a[ 4]= 9
a[ 4]= 8
a[ 4]= 1
a[ 4]= 6
a[ 4]=15
a[ 4]= 4
a[ 4]= 2
a[ 4]= 0
a[ 5]=10
a[ 5]= 7
a[ 5]= 5
a[ 5]= 3
a[ 5]= 4
a[ 5]= 0
a[ 5]= 2
a[ 5]= 8
a[ 5]=11
a[ 5]= 6
a[ 5]= 9
a[ 5]= 1
a[ 5]=15
a[ 5]=13
a[ 5]=12
a[ 5]=14
a[ 6]= 9
a[ 6]=11
a[ 6]=14
a[ 6]=15
a[ 6]= 7
a[ 6]= 2
a[ 6]= 0
a[ 6]= 8
a[ 6]= 3
a[ 6]=10
a[ 6]=13
a[ 6]= 5
a[ 6]=12
a[ 6]= 6
a[ 6]= 4
a[ 6]= 1
a[ 7]= 4
a[ 7]= 7
a[ 7]= 2
a[ 7]=14
a[ 7]= 3
a[ 7]=10
a[ 7]=15
a[ 7]= 9
a[ 7]=11
a[ 7]= 0
a[ 7]=13
a[ 7]= 6
a[ 7]= 1
a[ 7]= 5
a[ 7]=12
a[ 7]= 8
Thanks a lot Chris.
In reply to suyog_asic:
Chris, I havent tried with unique option. But what I tried also suffices me for now.
Thanks again.