# Assigning the elements in a 3d array **URL:** \ **Category:** SystemVerilog\ **Tags:** logic-array-packed-unsigned, systemverilog-distribution-constraints, SystemVerilog, uvm-sv-constraints, constraint-foreach-loop, systemverilog-Arrays-logics\ **Created:** [May 16, 2022, 7:05am UTC](https://verificationacademy.com/forums/t/assigning-the-elements-in-a-3d-array/40403 "2022-05-16T07:05:57Z")\ **Posts on this page:** 4\ **Page:** 1

**Author:** ![ShashankGurijala](https://verificationacademy.com/forums/letter_avatar_proxy/v4/letter/s/e9c0ed/32.png) [@ShashankGurijala](https://verificationacademy.com/forums/u/ShashankGurijala)\ **Post date:** [May 16, 2022, 7:05am UTC](https://verificationacademy.com/forums/t/assigning-the-elements-in-a-3d-array/40403/1 "2022-05-16T07:05:57Z")

Hello! Look at the below code. Im trying to assign the elements as follows: ```verilog class packet; rand int array [] [] []; //diff b/w randc bit [3:0] [1:0] array [] [] [] and randc bit [7:0] array [] [] [] randc int size_i, size_j, size_k; static constraint c1 { array.size == size_i; foreach (array [size_i]) { array [size_i].size == size_j; foreach (array [size_i,size_j]) { array [size_i][size_j].size == size_k; } } } //c1 is the constraint to randomize rows, columns and height of a 3d array static constraint c2 {size_i > 0; size_j > 0; size_k > 0;} constraint c3 {size_i <= 5; size_j <= 5; size_k <= 5;} constraint c4 {size_i != size_j && size_j != size_k && size_i != size_k;} constraint c5 {unique {array};} static constraint c6 { foreach (array [size_i]) { foreach (array [size_j]) { foreach (array [size_k]) { if (size_i % 2 == 0) { if (size_j % 2 == 0) { if (size_k % 2 == 0) { array [size_i] [size_j] [size_k] == 222; } else if (size_k % 2 != 0) { array [size_i] [size_j] [size_k] == 221; } } if (size_j % 2 != 0) { if (size_k % 2 == 0) { array [size_i] [size_j] [size_k] == 212; } if (size_k % 2 != 0) { array [size_i] [size_j] [size_k] == 211; } } } if (size_i % 2 != 0) { if (size_j % 2 == 0) { if (size_k % 2 == 0) { array [size_i] [size_j] [size_k] == 122; } if (size_k % 2 != 0) { array [size_i] [size_j] [size_k] == 121; } } if (size_j % 2 != 0) { if (size_k % 2 == 0) { array [size_i] [size_j] [size_k] == 112; } if (size_k % 2 != 0) { array [size_i] [size_j] [size_k] == 111; } } } } } } } endclass module md_array_foreach_constraint; initial begin packet pkt = new; $display("\n----------------------------------------DISPLAYING ARRAY ELEMENTS-----------------------------------------------\n"); repeat (2) begin pkt.randomize(); $display ("\nThe dimensions of the randomized 3d array: Rows [i] = %0d , Columns [j] = %0d , Height [k] = %0d",pkt.size_i,pkt.size_j,pkt.size_k); for (int i = 0; i < pkt.size_i; i++) begin for (int j = 0; j < pkt.size_j; j++) begin $display ("\t"); //how is this tab space working in the program? for (int k = 0; k < pkt.size_k; k++) begin $display ("array [%0d]\t[%0d]\t[%0d] \t=\t %0d",i,j,k,pkt.array[i][j][k]); end end end $display ("\n-----------------------------------------------------------------------------------------------------------"); end end endmodule ``` Can you please tell me whats wrong with the code ---

**Author:** ![rag123](https://verificationacademy.com/forums/letter_avatar_proxy/v4/letter/r/eada6e/32.png) [@rag123](https://verificationacademy.com/forums/u/rag123)\ **Post date:** [May 17, 2022, 12:26am UTC](https://verificationacademy.com/forums/t/assigning-the-elements-in-a-3d-array/40403/2 "2022-05-17T00:26:03Z")

you have a contradicting constraint in C5 and C6. you are asking the array to be unique at the same time from constraint C6 you are trying to assign the solver fails. It would be helpful to show what you want to achieve with expected input and expected output. ```verilog (array[0][0][1] == 221); (array[2][0][1] == 221); ``` ---

**Author:** ![ShashankGurijala](https://verificationacademy.com/forums/letter_avatar_proxy/v4/letter/s/e9c0ed/32.png) [@ShashankGurijala](https://verificationacademy.com/forums/u/ShashankGurijala)\ **Post date:** [May 17, 2022, 2:08am UTC](https://verificationacademy.com/forums/t/assigning-the-elements-in-a-3d-array/40403/3 "2022-05-17T02:08:48Z")

_In reply to [rag123](https://verificationacademy.com/forums/t/assigning-the-elements-in-a-3d-array/40403/2):_ Say for array [1] [0] [1] where i is odd, j is even and k is odd, I want 121 to be printed in that index and hence the pattern follows. I understood the unique constraint and removed it. Then too i didn’t get the output as I wanted. ---

**Author:** ![ShashankGurijala](https://verificationacademy.com/forums/letter_avatar_proxy/v4/letter/s/e9c0ed/32.png) [@ShashankGurijala](https://verificationacademy.com/forums/u/ShashankGurijala)\ **Post date:** [May 17, 2022, 9:56am UTC](https://verificationacademy.com/forums/t/assigning-the-elements-in-a-3d-array/40403/4 "2022-05-17T09:56:16Z")

_In reply to [Shashank Gurijala](https://verificationacademy.com/forums/t/assigning-the-elements-in-a-3d-array/40403/3):_ Got the right answer after replacing the nested foreach loops with a single foreach(size\_i,size\_j,size\_k) { And also comment the constraint c5 (or remove/disable) Posting thee code here: ```verilog class packet; rand bit [25:0] array [] [] []; rand int size_i, size_j, size_k; static constraint c1 { array.size == size_i; foreach (array [size_i]) { array [size_i].size == size_j; foreach (array [size_i,size_j]) { array [size_i][size_j].size == size_k; } } } //c1 is the constraint to randomize rows, columns and height of a 3d array constraint c2 {size_i > 0; size_j > 0; size_k > 0;} constraint c3 {size_i <= 5; size_j <= 5; size_k <= 5;} constraint c4 {size_i != size_j && size_j != size_k && size_i != size_k;} constraint c5 { foreach (array [size_i,size_j,size_k]) { if (size_i % 2 == 0) { if (size_j % 2 == 0) { if (size_k % 2 == 0) { array [size_i] [size_j] [size_k] == 222; } if (size_k % 2 != 0) { array [size_i] [size_j] [size_k] == 221; } } if (size_j % 2 != 0) { if (size_k % 2 == 0) { array [size_i] [size_j] [size_k] == 212; } if (size_k % 2 != 0) { array [size_i] [size_j] [size_k] == 211; } } } if (size_i % 2 != 0) { if (size_j % 2 == 0) { if (size_k % 2 == 0) { array [size_i] [size_j] [size_k] == 122; } if (size_k % 2 != 0) { array [size_i] [size_j] [size_k] == 121; } } if (size_j % 2 != 0) { if (size_k % 2 == 0) { array [size_i] [size_j] [size_k] == 112; } if (size_k % 2 != 0) { array [size_i] [size_j] [size_k] == 111; } } } } } endclass module md_array_foreach_constraint; initial begin packet pkt = new; $display("\n----------------------------------------DISPLAYING ARRAY ELEMENTS-----------------------------------------------\n"); repeat (5) begin pkt.randomize(); $display ("\nThe dimensions of the randomized 3d array: Rows [i] = %0d , Columns [j] = %0d , Height [k] = %0d",pkt.size_i,pkt.size_j,pkt.size_k); for (int i = 0; i < pkt.size_i; i++) begin for (int j = 0; j < pkt.size_j; j++) begin $display ("\t"); //how is this tab space working in the program? for (int k = 0; k < pkt.size_k; k++) begin $display ("array [%0d]\t[%0d]\t[%0d] \t=\t %0d",i,j,k,pkt.array[i][j][k]); end end end $display ("\n-----------------------------------------------------------------------------------------------------------"); end end endmodule ``` What I want to now know is the difference b/w foreach(size\_i){foreach(size\_j){foreach(size\_k) …}}} and foreach(size\_i,size\_j,size\_k){…} in general and in this specific example as well. Thank you!