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SystemVerilog
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  • For loop and a random variable

For loop and a random variable

SystemVerilog 3450
constraint for loop 3
syed taahir ahmed
syed taahir ahmed
Full Access
68 posts
May 22, 2018 at 7:38 am

HI ,

I have a scenario where i have to randomize the loop count and randomize the variable such the loop count should not be wasted due to duplication of randomization of variable.

for Eg:: 

sa_entry_row        = $urandom_range(1,5);//Randomizing  The number of times add entries
                      for(int j=0; j<sa_entry_row; j++) begin
                      entry_add_index = $urandom_range(0,($size(test_entries_add)-1));//Randomizing the SA_entry index
                      //this condition will check existing added list in queue and avoid duplication
                      if (!(entry_add_index inside test_entries_added)) begin

if we see the code, sa_entry_row count gets unused if the entry_add_index is already existing, how should i make sure that entry_add_index is unique for each sa_entry_row?

Thanks

Replies

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dave_59
dave_59
Forum Moderator
6372 posts
May 22, 2018 at 10:32 am

In reply to syed taahir ahmed:

It would really help to show the declarations of all variables involved and what they represent.

From what I can figure out, you should be using constraints. 

randomize (entry_add_index) with {
    entry_add_index <$size(test_entries_add);
    unique {entry_add_index,test_entries_added};
}
syed taahir ahmed
syed taahir ahmed
Full Access
68 posts
May 22, 2018 at 10:42 am

In reply to dave_59:

This is my full code. The issue is for eg:: when i randomize sa_entry_row ,if it is 5 and when entry_add_index is randomized and if the value already in test_entries_indices_added for all 5 times then the loop of 5 goes unused .

I have to make sure that , the variable entry_add_index is unique always when sa_entry_row is looped.

if (sa_op_type == ADD) begin
                    sa_entry_row        = $urandom_range(1,5);//Randomizing  The number of times add entries
                    for(int j=0; j<sa_entry_row; j++) begin
                        entry_add_index = $urandom_range(0,($size(test_entries_add)-1));//Randomizing the SA_entry index
                        //this condition will check existing added list in queue and avoid duplication
                        if (!(entry_add_index inside test_entries_indices_added)) begin
                            add_entries_random(test_entries,test_entries_add,entry_add_index);
                            test_entries_indices_added.push_back(entry_add_index);//Queue created to avoid the duplication of the entry
                            added_entry_indices.push_back(entry_add_index); //This is added entries which used as grep in delete entry
                        end
                    end
                end

Thanks

Solution

Solution

dave_59
dave_59
Forum Moderator
6372 posts
May 22, 2018 at 5:49 pm

In reply to syed taahir ahmed:

You still didn't show the declarations of all variables in the code. But I think replacing
entry_add_index = $urandom_range(0,($size(test_entries_add)-1));with

void'(randomize (entry_add_index) with {
    entry_add_index <$size(test_entries_add);
    unique {entry_add_index,test_entries_added};
});
should work.
syed taahir ahmed
syed taahir ahmed
Full Access
68 posts
May 22, 2018 at 6:16 pm

In reply to dave_59:

I'll post the result once trying.

I appreciate your reply Dave, thanks

syed taahir ahmed
syed taahir ahmed
Full Access
68 posts
May 22, 2018 at 9:39 pm

In reply to dave_59:

Quote:
In reply to syed taahir ahmed:

You still didn't show the declarations of all variables in the code. But I think replacing
entry_add_index = $urandom_range(0,($size(test_entries_add)-1));with

void'(randomize (entry_add_index) with {
    entry_add_index <$size(test_entries_add);
    unique {entry_add_index,test_entries_added};
});
should work.

HI Dave ,

One doubt i have with the implementation, since there is condition the number of entry_add_index to be added will be count of $size(test_entries_add).

The query was if the sa_entry_row get a value 5 and we have only 3 entries to be added then the randomization will fail for unique? if i understand correctly.

Thanks

dave_59
dave_59
Forum Moderator
6372 posts
May 23, 2018 at 8:54 am

In reply to syed taahir ahmed:

For the third time, I'll ask for the declarations of the variables involved. How does one determine how many remaining entries are left?

syed taahir ahmed
syed taahir ahmed
Full Access
68 posts
May 24, 2018 at 7:10 am

In reply to dave_59:

Quote:
In reply to syed taahir ahmed:

For the third time, I'll ask for the declarations of the variables involved. How does one determine how many remaining entries are left?

Sorry my bad .. But your solution worked ☺️

Thanks Dave.

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