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Controlling sequence library distibution

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Hi All, 


I have a question about controlling sequence library distibution. I would like to give the test writer the ability to control sequences distribution. For that i am  using the uvm_sequence_library class. I saw that the index of a sequence in the library is determined by the order of sequence registration to the library (using `uvm_add_to_seq_lib macro). but this raises problem when removing sequences for example:


Project1 :


Sequence lib code:

constratint select_sequence_c { select_rand dist {   0:=20, // sequence_A

1:=100, // sequence_B

2:=20  // sequence_C



The test owner would like to override the default distribution so in the test there is the following constraint layering:

constratint select_diff_dist { select_rand dist {  /*0:=20, // sequence_A*/

1:=30, // sequence_B

2:=30  // sequence_C



Next project . Project2 does not include sequence A anymore so it was removed from the sequence library . Sequence index is now shifted.


constratint select_sequence_c { select_rand dist {  

0:=100, // sequence_B

1:=20  // sequence_C



Now the test should be changed since index 1 does not point to sequence B anymore ( and so on…):

constratint select_diff_dist { select_rand dist {

1:=30, // sequence_B

2:=30  // sequence_C



In OVM we used string based hash which is now deprecated:

constraint select_seq seq_kind dist {seq_kind dist Get_seq_kind(“sequence_A”) :=20,

seq_kind dist Get_seq_kind(“sequence_B”) :=20,

seq_kind dist Get_seq_kind(“sequence_C”) :=20};




Any idea how to solve this?




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1.  set the      “selection_mode = UVM_SEQ_LIB_USER;  “ of the sequence library

2.  implement “virtual function int unsigned select_sequence(int unsigned max);” and return the index of the chosen sequence inside “sequences”



without having kind you could do something
int item;
uvm_object_wrapper w[$] = {AS::get_type(),BS::get_type(),CS::get_type()};
void'(std::randomize(item) with {item dist {0:=20,1:=20,2:=20};});
// now just find the index of w[item] in sequences[$] and return it, or ...
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