Systemverilog constraint inside g. Basically constraints are nothing more than a way to let us define what legal values should be assigned to the random variables. This approach is time- and knowledge-expensive. 2. y dist { [1:1000] :/ 40, 1500 :/ 60 } Does it support multiple random elements. In constraint random verification, it may take a long time for a particular corner case to be generated which scenario we never thought. SystemVerilog does not allow the for construct in a constrain, but you can think of foreach as a If else in constraints; Implication operator in constraint; foreach loop in constraint; Dist keyword in constraints; Inheritance in constraint; Function in constraint; Disable randomization; Static constraints; Unique constraint; Bidirectional constraint; Solve Before in constraint; Inline constraints; Soft constraint; Randomization methods Hi, I want to use case statement inside a constraint, in my TB environment. We sometimes say that CRV automates writing tests for Expression evaluation is identical whether you are inside a constraint or not. Think of it like disabling randomization for all fields except for req via calls to rand_mode(0). Functional Coverage; SystemVerilog Assertions; UVM Menu Toggle. The foreach construct is used as both a looping construct in procedural code and as an iterative constraint that gets unrolled until simultaneous constraints. So, a separate function can be written which has these mathematical calculations. LFT March 12, 2024, 4:16pm 1. In this case, you have a 32bit variable which has a huge randomization space for randc to try and work within. Other features of constraint. Is it possible to constraint an entire array in SystemVerilog to have the same value as another array? I tried this: class some_class; rand bit array1[10][10]; rand bit array2[10][10]; constraint arrays_c { array1 == array2; } enclass This isn't allowed in 2 of the Big3 simulators I've tried. When i am trying to give inline constraints, the code is compile free. rand_mode can be called both as a function and task. The following code snippet shows both styles // Implication operator "->" tells that len should be // greater than 10 when mode is equal to 2 constraint c_mode { mode == 2 -> len > 10; } // Same thing can be achieved SystemVerilog supports using the foreach loop inside a constraint block. Out of 20 items, the values of 3 items should be equal to 5 at random positions. com Abstract: Constrained Random Verification (CRV) addresses the time-consuming task of writing individual di-rected tests for complex systems. Hi, I have address range for 0 to 131072. constraint, constraint-randomization, SystemVerilog. During randomization, it might require to randomize the variable within a range of values or with inset of values or other than a range of values. So a disabled random variable is treated the same as if they had not been declared rand or randc. byte my_array [0:8] loop through all the elements in the array to restrict their values to be within the range from 1 to 9. rand_mode(0); assert(at. these functions should not be used in SystemVerilog as they are not part of the random stability model. Just like static variables in a class, constraints can be declared as static. b. The below constraint gives the maximum number of one that the variable can have. The function “calculate_len” seems to calculate the correct length and returns it, but “len” is always coming up to SystemVerilog constraint: constrain the read address has been written before. Does this look right? any better ways to do this? class A; rand bit[31:0] addr; bit [31:0] a In reply to yourcheers:. randomize(a)); Alternately, as you mentioned in the title to your question, you can use rand_mode to disable randomization of individual class variables:. Basically constraint INSIDE { d inside { arr } ; } It will work as solver should take care of it to satisfy the constraint. I was under the impression that the first implementation should work as well. Constraints can be enabled or disabled by constraint_mode(). The constraint on adder. number; i++) begin // Code end . It is used to randomize the member variables of the class. b. Improve this question. A normal variable is declared to be In constraint random verification, it may take a long time for a particular corner case to be generated which scenario we never thought. Some are from the LRM and other are code examples of what I’ve used. Personally I would recommend the implication syntax People tend to read the if-then-else constraint like a procedural-if statement. I have given constraint as below but its not working, I still get addresses or lenth or size such that it will cross 4k. Let’s say we have following example: rand logic a; constraint c1 {a==0;} constraint c2 {a==1;} The constraint solver parses both the constraints concurrently. inside-inline-constraint, Conditional-constraint, Expression evaluation is identical whether you are inside a constraint or not. Misc Constructs Program Block Dynamic Casting Packages Commandline Input File SystemVerilog allows to call functions inside constraints, although, as I found out, it is a sensitive topic. Hi All, If AxSize is ‘N’ then the address must be aligned to 2**N Constraint blocks for a parent class can be overridden by its child class. Constraint logic shall be written inside the function as function definition and function call shall be placed inside the constraint block; Functions shall be called before constraints are solved, and their return values shall be treated as state variables. alexd555 September 11, 2019, 3:40pm 1. I was trying a few codes involving dist and inside :: // CODE I rand int val ; int a = 10 , b = 20 , c = 21 , d = 30 ; // Can be changed at run-time constraint V1 { val inside { [a:b] } ; } constraint V2 { val inside { [c:d] } ; } The above code has constraint failure ( Since V1 and V2 both can’t be true at same time ) Although the intention is to keep val between 1 to 20 , it should be Hi, i am having base class like class base; rand [1:0]var; constraint cnt {var inside {2,3};} endclass Now i am using this class in another class like class basic; base b; b=new(); b. The foreach construct iterates over the elements of an array and its argument is an identifier that represents a single entity in the array. But this constraint doesn’t I have a question related to using ‘dist’ operator inside a foreach loop in a systemverilog constraint. 22+10=32 but msb bit is 31 where that will appear as only continues 9bit The post you reference explains the reasoning. but give a weight to the randomization. When I run this code in eda playground, I see [0:5] is about 599 times, & [6:7] is about 401 times, that is 6:4 ratio. Either the function input arguments cannot reference any random variables, or the function return value cannot have any constraints that restrict the function inputs. When you say “in the teat” and “in the env”, I assume these are different classes. In reply to o-hassan: Constraints are not procedural statements - they are a set of simultaneous equations. this can be achieved by using constraint inside constraint not_in_range { foreach(range_of_values[ii]) !(range_of_values[ii] inside {[a:a+s]}); } Every item in range_of_values array will not be in range [a:a+s]. Random Constraints. But I am not able to write a method to randomize the each element of array with given constraint. the Skip to main content in SystemVerilog constraints come either through declarative constructs, if-then-else guards in the constraint or in-line constraints (randomize with), or at run-time only through enable/disable. SystemVerilog. . A disabled constraint is not considered during randomization. flag gets the value 1 if the randomized value of m_data lies within 4 to 9, including 4 and 9. Can someone please We can express this constraint as the numerical inequality. In reply to DoDo_Drx: The problem is you overrode the c_addr_default constraint in your derived class (BTW, see this post about the improper use of the work “child”), but when you that constraint off, the base c_addr_default remains active. Adding additional constraint on ‘d’ may help solver to solve constraint fast. for (int i = 0; i . – a. Please use code tags making your code easier to read. You have not connected through any constraint of reg_address to any value in reg_address_array. For “randc” variables are supported inside constraints. object constraints are not allowed in SystemVerilog because they are not integral types. 2:Variables declared with the ‘rand’ modifier must be of an integral or class handle type This page contains SystemVerilog tutorial, SystemVerilog Syntax, SystemVerilog Quick Reference, DPI, SystemVerilog Assertions, Writing Testbenches in SystemVerilog, Lot of SystemVerilog Examples and SystemVerilog in One Day Tutorial. Constraint logic shall be written inside the function as function definition and function call shall be placed inside the constraint block; Functions shall be called before constraints are solved, and constraint data_cons{ (data_flag > 2) -> data inside {[1: 3]}; (data_flag <= 2) -> data inside {[4: 6]}; } if else 条件判定，只有在data_flag大于2时，data从1、2、3中取值， Range: We can use inside keyword to specify that a random variable should be within a certain range or set of values. If they did support it, the value of the variable at the time of starting the randomize() was used for the input but this constraint did not affect its end value. Hence this constraint is redundant as well . If the expression is true, all the constraints in the first constraint/constraint-block must be satisfied, otherwise all the constraints in the optional else constraint/constraint-block Object vs. size In reply to natasv:. Using casex is the second biggest sin in Verilog (second to using ordered port mapping). SystemVerilog randomization also works on array data structures like static arrays, dynamic arrays and queues. Integral expressions are weakly typed in SystemVerilog. In reply to dave_59: Hi All. Also create a helper array so you can iterate from 0-9. I expect . data inside {[0:8'hff]}; data is 8-bit variable which means the solution space varies from 0 to 8’hFF without the constraint as well . If not, flaggets 0. constraint constraint_name { var = function_call(); }; Functions in constraints example 有时合理使用inside操作，可以使得编码更为高效和简洁，在这里分享几个inside常见的使用方法。 inside和随机约束 在sv的constraint描述中，可以使用inside表达随机变量的取值范围。; range_list可以是单个取值的列举，也可以是使用[a:b]表达的范围，或者二者的混用组合。 Constraint block can call a function to get constraint values as the return value from the function. One problem is you may have is doing integer division. About; Products OverflowAI; Stack Overflow for Teams Where developers & technologists share private knowledge with I need to create a constraint for a 32 bit address, such that it is always 2 bits different than previous randomized value. Home; About; Blog. value inside the constraint dave_59 April 23, 2024, 4:46pm SystemVerilog. Constraints are class members, just like fields and methods Random variables solved as part of a higher priority set of constraints become state variables to the remaining set of constraints. so I have: bit [9:0] ready_boxes; int I want to constraint variable a such that it has one bit set high (one hot ) and it should be negative number meaning -1, -2 -1024 with min and max set as -1 and -1024 shortint a; constraint c1 { a The right hand side of an implication can be a constraint set: constraint example { flag == true -> {other_flag_1 == false; other_flag_2 == false; other_flag_3 == false;}; } Note that when your constraints are Boolean expressions, it’s the same as the logically ANDing them into one Boolean expression SystemVerilog. and remaining bits as 1. The solver will take all of the constraints defined in some_item together with the one we defined above on req. Hi, I want to write constraint that chooses only even number in the range. or, perhaps more clearly, using SystemVerilog’s range-membership operator inside. So far I’ve tried two approaches to achieve this. Hot Network Questions To “digitize” means to turn something into a digital format that was previously not digital. Expressions or conditions can be written inside a constraint block. c. I have a constraint of the form: s dist {0:= 20, 1:= 25, 2:= 30, <many more, possibly hundreds>}; Instead of writing down the constraint this way, I found in my application the RHS (i. randomize(), also called Class-Randomize Function, is a function built into all SystemVerilog classes. We propose a standard suite of SystemVerilog constraint You want the or array reduction method. I want to have a constraint which limits the number of Hi, Now I have an inline constraint as below assert(req. arr[i]==d // it will force RHS to be equal to LHS, and 'd' doesn't have any constraint so it will work I’ve got two random variables; the first one is an enumerated type which selects 1 of 3 “sets”. 约束的使用. com Abstract- SystemVerilog provides several mechanisms for layering constraints in an object. Is there any alternative way to do this type of randomization, as my original class contains almost 38 variable, and individual assignments would be troublesome. rand bit [7:0] data []; constraint data_size() {data. And for a axi incr burst transfer it should not cross upcoming 4k boundary. In your example you are trying to use a non-constant lsb expression count. If any of the constraint, we use a condition with soft keyword then that condition will be given lower priority. 13 :: "A bound specified by $ shall represent the lowest or highest value for the type of the expression on the left-hand side. what is not working for you in this? This page contains SystemVerilog tutorial, SystemVerilog Syntax, SystemVerilog Quick Reference, DPI, SystemVerilog Assertions, Writing Testbenches in SystemVerilog, Lot of SystemVerilog Examples and SystemVerilog in One Day Tutorial. Sometimes even after . So assuming we have N*N chessboard, say N=5 for simplicity, whose squares are numbered from 0 to 24, as shown: I wrote the code below to get random array tour_indices for possible indices of the movements, SystemVerilog constraint: constrain the read address has been written before. If load != 1, data is unconstrained Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Advertising & Talent Reach devs & technologists worldwide about your product, service or employer brand; OverflowAI GenAI features for Teams; OverflowAPI Train & fine-tune LLMs; Labs The future of collective knowledge sharing; About the company Visit the blog Hi, Now I have an inline constraint as below assert(req. To present my problem I put together a stripped off version of my code by referring to other posts, especially the one located here: Constraint for object dynamic array Here is the sample code to represent my I have a constraint like this: constraint constraint_len { soft len == calculate_len(x); } x is itself a local constrained random variable. c2 — Functions that appear in constraint expressions should be automatic (or preserve no state information) and have no side effects. Static Arrays Is there any way to declare conditional constraint inside inline constraint while calling randomize method. a), then it works. e. This is because casex is symmetrical (as is casez). I am unable to understand where I am doing it wrong. For example, constraint c3 {c inside {[0:9]};} means that To write a constraint inside a class, we need to define a constraint block using constraint keyword and give a name to it. Parametrized uvm sequence item to adjust size. y inside [2,6];}) endtask. initial begin. Think of what you needed to deal with 6-bits of cyclic randomness. To modify or override a constraint, explicit details about the test bench must be known, the new constraint correctly implemented, and simulation recompiled. I want to random a variable with constraint to be inside rises bits in the index array with the weight that is in the weight array. I want I have a 32 bit variable, I want to write a constraint which constraints the number of consecutive ones that the variable can have. I have a requirement to pick random addresses from a set of predefined ranges in Systemverilog program test; int unsigned q[$], rSz; typedef struct { int unsigned from, till; } range_t; initial Skip to main content. There is a possibility where calculation may differ based on input provided. How do i constraint a signal A[3:0] to only have values between 1 to 8 for my State Space property p_A; @(posedge clk) // Range for A to be between 1 to 8 endproperty : p_A ap_A: assume property (p_A); constraint VALID_BURST_LEN_RANGE {2^Awsize * (Awlen+1) <= 4096;} Regards, Shanthi. How can we display hex In reply to UVM_LOVE:. arr[i]==d // it will force RHS to be equal to LHS, and 'd' doesn't have any constraint so it will work SystemVerilog Pseudo Random Number Generators 1. randomize with {} or `uvm_do_with) I tried to create an invalid group and constrain it to be not inside the valid types but this doesn't work. c. Part - VI. inside. Any hint would be appreciat In reply to superUVM:. why 21 because 21+10=31 which is msb bit(if it is more than 21 example. In the following example, inside operator is used both in an if else statement and a ternary operator. and in the sequence when I try to generate an new txn I refer to the sequencer queue which holds inflight txn addresses and not I have created a dynamic array1 with some size and values 2)I was able to constraint the 2nd array2 to match the array1 size Now how can i add a constraint block so that array2 values are inside the values of array1? Basically i need my 2nd dynamic array to pick its values from the 1st dynamic array values My intention is to create the 2nd dynamic array • SystemVerilog constraints work over references • Compilation-time rules apply to the referenced class – Want to magically put a new constraint val “inside [0:1024]” 2 2 10 . You can start typing straight away. However, the constraints with uvm_do_on_with are not working. An exception to this rule is a weight of zero, which is treated as a constraint. randomize()); SystemVerilog constraint: constrain the read address has been written before. Dynamic randomization is achieved essentially by modifying details of an existing constraint, variables within the constraint, and enable/disable, rather than changing the constraint – Reference: Approved for SystemVerilog IEEE 1800-2012 (Mantis 2987) • Overriding or constraint_mode(0) are applied to a constraint block (not individual constraint) – Block must contain only the constraints to be modified – Requires documentation or naming convention to identify blocks that are OK to ignore • If a constraint should be applied except for a particular A repeat loop can also be implemented using a for loop but is more verbose. Wondering if there is a more efficient way to do this. Thanks. Constrained PRNG - obj. Why "Implication" and "if–else" constraints showing different results? 1. size() == num_chosen; foreach (chosen[i]) { chosen[i] inside {choices}; } } You can also add unique constraints to prevent repetition if that is a requirement you failed to mention. The inputs to your function get their random values chosen before calling the function in the constraint. The constraint for data is written inside the class, and the inline constraint is constraint c1_c{i1 inside {[1:10]};}; endclass. Systemverilog支持集合操作符inside，有时合理使用inside操作，可以使得编码更为高效和简洁。inside操作符可以方便的比较一个数值、多个可能值或连续区间值之间的关系。它的语法格式为： inside_expression ::= expression inside { open_range_list } Hello everyone, I was trying to write constraints on class variables in a top level class and the problem is the class handles themselves are dynamic arrays. But to run your SystemVerilog constraints are used to control the values that are randomized for variables during simulation. If the variable i is not required to be referenced inside the loop, a repeat loop would be more suitable. 4. Thus, the All slicing operators in system verilog require constant width of the slicing. For some reason, the call to randomize() System verilog support continuous range inside a 'dist'. rand bit [15:0] inv_cmd_type; constraint not_in_range {!(inv_cmd_type inside {command_type_e});} I tried a couple other ways without much success. The values of 8 items must be 15 and the remaining 4 I have a code where a variable is declared inside task. All constraints are by default enabled and will be considered by the SystemVerilog constraint solver during randomization. In the code shown below, we have a repeat loop to wait for a given number of clock cycles. Inside unique constraint I can constraint a whole unpacked array ( 1D as well as 2D ) I am writing Assertion for Formal Verification and Wanted to constraint an Input using Assume. In addition to overflow, you also need to be concerned about truncation and sign conversion. Interchangeable Constraints Abstract SystemVerilog constraints are declarative. Hence I have following code :: class Base ; rand bit [4:0] b ; constraint VAL { b == 15 ; } endclass class Ext extends Base ; `ifdef M1 bit val_cg ; // Holds Constraint Mode of Constraint VAL function void Edit, save, simulate, synthesize SystemVerilog, Verilog, VHDL and other HDLs from your web browser. Using ‘val_list’ inside a constraint works for me. This is very similar to the constraint_mode() method used to Disable Constraints. 12 Functions in Constraints. You must have a constant select, or use an iterative constraint like foreach or array. inside操作符的基本语法 req. SystemVerilog gives us two constructs to declare conditional relations - implication and if else. I can inside constraint Implication Constraint foreach Constraint solve before Constraint Static Constraints Practical Constraint Examples Bus Protocol Constraints Randomization Methods In-line Constraints Soft Constraints Disable Constraints Disable Randomization Random Weighted Case 9. “randc” will make sure that the all possible values are covered before repeating the SystemVerilog allows users to specify constraints in a compact, declarative way which are then processed by an internal solver to generate random values that satisfy all conditions. All other bits in the data variable can be randomized to 0 or any other pattern, but there should not be any 1s in between the In reply to dave_59:. i and j values should be any number diagonal matrix left side values should be incre I have an index array of bits, and weight array with integer values. constraint con1 {a dist {1:=5};} Hi all , I was trying if I could achieve a unique array without array. size is part of the set of constraints, so it becomes a random variable. randomize & std::randomize¶ obj. When constraints are defined outside a class's body, they are called external constraints and are accessed by You are very limited in how you can use a user defined function inside a constraint. If load != 1, data is unconstrained SystemVerilog allows both if and for statements inside a generate block, giving designers fine-grained control over how hardware components are generated. UVM Verbosity override. You can extrapolate this to get your three q’s. constraint, if-statement-in-constraint, (packet) // I removed the part here since it's not related `uvm_object_utils_end constraint valid_addr { addr inside {[15'h0000:15'h6EFF], [15'h7F00:15'h7FFF]}; } constraint solve_td_b4_data { solve td before cmd; } constraint solve_addr_inc_b4_data { solve addr_inc before cmd; } constraint In reply to ssureshg_: Your solution always starts a 0. The ‘If’ statement is a conditional statement based on which decision is made whether to execute lines inside ‘if’ block or not. In if-else case, last item is not constraints. What to call changing one digital format into another? Could you Hi, I have the next scenario inside uvm_seqeunce_item class: bit [10:0] a; int b; bit [511:0] data I need to create constraint in which size of data array is Hello there! I am trying to generate 10 values which are divisible by 5 in its ascending order. constraint mADDR {mtestADDR inside {[0:131072]};} constraint mADDRalligned Is there any way to declare conditional constraint inside inline constraint while calling randomize method. Make sure that you declare ‘rand_var’ as ‘rand int rand_var’, otherwise you will get a single bit variable. Any conflict in these constraints leads to randomization failure. Something like: restrict: assume property ( foreach(my_array[i]) my_array[i] inside {[1:9]} ); The above is not accepted by the parser. All constraints are evaluated in parallel to form a solution space, and then the solver randomly picks a single solution. rand_mode(0); at. In my base_sequence which is virutal sequence class, i have instance of a sequence as seq1. This will not work. Follow asked Jul 23, 2015 at 19:59. The important thing to note that inline constraints do not override constraints written inside the class. ranjitha555@gmail. The state space of randc variables is based on the variable type. Seeing those two (the inline and the constraint block) lined up like you did will help this stick in my head that they are the same syntax. Edit, save, simulate, synthesize SystemVerilog, Verilog, VHDL and other HDLs from your web browser. The values of 5 items must be 10 at random positions d. Whenever a 1 is detected in the pattern, it should be represented as nine consecutive 1s. 3: Constraints can be any SystemVerilog expression with variables and constants of integral type (e. module tb; bit clk; always #10 clk = ~clk; initial begin bit [2:0 Hi, I have the next scenario inside uvm_seqeunce_item class: bit [10:0] a; int b; bit [511:0] data I need to create constraint in which size of data array is I have a code where a variable is declared inside task. As Dave pointed out, the initial code you posted is incomplete and insufficient. Hi all , [1] I have subclass that overrides base class constraint . The following simple example can illustrate: eda playground A couple approaches I’ve tried were to simple create SystemVerilog Constraints: Appreciating What You Forgot in School to Get Better Results Dave Rich Mentor, A Siemens Business Dave_Rich@mentor. shanthi June 1, 2020, 11:40am 2. Lets say I have 10 boxes and I want to choose one box from the boxes that ready (to sending). Please help Thanks a lot, dave_59. size inside [4:6];} constraint data_c {foreach (data[i]) {data[i] < 20;}}. Is it Ok ? In reply to dave_59: Hi All. e square matrix. Size of an array can be anything class Example; rand bit [15:0] my_arr[]; //if I change to 31 here, I see an incorrect array rand int inx_num; constraint c1 {my_arr. You switched accounts on another tab or window. Engineered SystemVerilog Constraints Jeremy Ridgeway Avago Technologies, Inc. I need to generate array elements with values according to a distribution pattern. The idea is to take a 52X2 matrix with 1st column representing suites and 2nd column representing ranks. I have added them for you. I have seen that there was a problem with the sum (WWW. 127 2 2 silver badges 12 12 bronze I should add that an implication does not work like procedural code. Hello, I need to randomize a variable with equal distribution between {1 , [2:5], [6:15]} ie, probability to generate 1 is 1/3 probability to generate 25 is 1/3 probability to generate 615 is 1/3 How do i define t Sometimes constraint value has to be decided based on a mathematical model or some certain calculations. I would approach this problem as below : Start with the enum as a typedef. In reply to MarshallX: Please use code tags making your code easier to read. As the name suggests, a unique constraint is useful to generate unique values for variables and elements in an array (Fixed array, associative array, dynamic array, and queue) Syntax: constraint <constraint name> {unique {array or variable};} If else in constraints; Implication operator in constraint; foreach loop in constraint; Dist keyword in constraints; Inheritance in constraint; Function in constraint; Disable randomization; Static constraints; Unique constraint; Bidirectional constraint; Solve Before in constraint; Inline constraints; Soft constraint; Randomization methods You signed in with another tab or window. The body of the constraint should be enclosed within Constraint inside the class and inline constraint. inside-inline-constraint, Conditional-constraint, Just as with SystemVerilog, constraint blocks are considered virtual, in that a same-named constraint in a sub-class overrides the constraint in the super-class. For example {1,3,2,6} :/ 40 Is it possible to use 'inside' in 'dist' ? system-verilog ; Share. So I record the txn in a sequencer queue and delete once txn is finished. DLC inside {[0:8]} These are both Boolean expressions and therefore they can be used in a constraint using the constraint keyword. A static constraint is shared across all the class instances. x inside [0,1,3,4]; req. operation inside {INSTRUCTION_RANGE_1, INSTRUCTION_RANGE_2, INSTRUCTION_RANGE_3} }) and INSTRUCTION_RANGE_1/2/3 are queues of X86 instruction enumeration operation_e INSTRUCTION_RANGE_1[$] = {PMULLD, PMULDQ}; operation_e In reply to alexkidd84:. randomization with { req. Instead you have to use an equivalence operator == as shown for the constraint named my_min in the Here’s a cheatsheet of SystemVerilog constraints patterns. 2:Variables declared with the ‘rand’ modifier must be of an integral or class handle type Thanks dave for the hint. In reply to ranju. The constraints would be then each column1 element is within suites and column2 is from ranks. If you try to do, for example, c_obj. x & y are the seq items for seq1. 22+10=32 but msb bit is 31 where that will appear as only continues 9bit Hence this would be redundant as load would have these 2 values with equal probability even without the constraint . Constraints may be added via inheritance in a derived class. There is a lot of missing information here. When I define a random variable(in_m), I set a constraint with the help of my function. The function “calculate_len” seems to calculate the correct length and returns it, but “len” is always coming up to Knight’s tour is a sequence of moves of a knight on a chessboard such that the knight visits every square only once, for more info please check Wikipedia. constraints reduce the solution space. I have a constraint like this: constraint constraint_len { soft len == calculate_len(x); } x is itself a local constrained random variable. constraints, SystemVerilog. It's great for learning HDLs, it's great for testing out unfamiliar things and it's great for sharing code. SystemVerilog randomization constraints Constraints are expressions that need to be held true by the constraint solver when solving a randomization problem. Shouldn’t b be 5 too in the output ? . However I want that whenever the Overridden Constraint is disabled the parent Constraint should take effect . " So using ‘$’ within constraint rand bit [1:0] a , b , c ; constraint INSIDE_RANGE { a inside { [0:$] } ; // (a) b inside { [$:0] } ; // (b) c inside { [$:$] } ; // (c) :: I know doesn't make Sense !! } I Observe that both (a) and (b) Works fine but From what I remember, some vendors didn't support such constraints in the past, where a random variable is used as an input to a method. Also, the variable is 26-bits in size. Skip to content. emacs init file at in SystemVerilog constraints come either through declarative constructs, if-then-else guards in the constraint or in-line constraints (randomize with), or at run-time only through enable/disable. constraint c_value {a[i]. Should I declare a function to implement summation equation In the above example, EDA Tool will consider two different constraints so it will try to resolve both constraints because the Same variable is constrained using two different constraints (Names are different so the Child class can’t override the Parent class’s constraint) having different names and both constraints are contradict to each other. Can anyone say whether it works or not? If not, then what are the alternative ways, other than ifelse and implication operators? typedef struct packed { logic [3:0] A; logic [3:0] B; } pkt; rand pkt [10] p; How to write constraints to systemverilog so that they are executed simultaneously: A and B had unique Hi, I have the next scenario inside uvm_seqeunce_item class: bit [10:0] a; int b; bit [511:0] data I need to create constraint in which size of data array is If there are constraints on some expressions that cause the distribution weights on these expressions to be not satisfiable, implementations are only required to satisfy the constraints. Current state of the variable will be returned if it is called as Hi, today I am going to write about how to write different constraints in SystemVerilog to achieve the same goal, to randomize the number of ones in a variable. write a SystemVerilog constraint for a 64-bit variable data. A function You want the or array reduction method. Hey Everyone, I have constraints below for three arrays to be unique (unique from each other as well). (1) " You are not allowed to refer to a random array as a whole variable in a constraint. Let's get started. operation inside {INSTRUCTION_RANGE_1, INSTRUCTION_RANGE_2, INSTRUCTION_RANGE_3} }) and INSTRUCTION_RANGE_1/2/3 are queues of X86 instruction enumeration operation_e INSTRUCTION_RANGE_1[$] = {PMULLD, PMULDQ}; operation_e If you only want one of the rand variables in a class to be randomized, then you can pass the variable to the randomize function:. By this, I mean that with casex an X in the input expression (in in If I take individual variables for o2 and use inline constraint with that (like o2. randomize() with {a inside {[11:100]};};, the soft constraint inside c class will be suppressed by the inline constraint, and will randomize a to values ranging from 11 to 100. Stack Overflow. Can you help? Eg. In system Verilog, constraints are treated just SystemVerilog Constraints Examples Set Membership¶ /* using other variables as a part of a constraint */ rand integer x, y, z; constraint c1 {x inside {3, 5, [9:15], [24:32], [y:2*y], z};} rand integer a, b, c; constraint c2 {a inside {b, c};} /* constraint a variable to values from an array */ integer fives[4] = '{ 5, 10, 15, 20 }; rand integer v; constraint c3 { v inside {fives SystemVerilog Constraint Layering via Reusable Randomization Policy Classes John Dickol Samsung Austin R&D Center Austin, TX j. In this scenario soft keyword comes in rescue. So it is the same as if you had written. com:. This constraint reads: if at least one element has the value 0-9, then one of those elements has to have en set. But, I’m concerned if calling ‘dist’ operator for each element will cause unintended distribution. EDA code link: https://edaplayground. constraint c1 {x inside {3, 5, [9: 15], [24: 32], [y: 2 *y], z};} rand integer a, b, c; constraint c2 {a inside {b, c};} Inverted Inside Operator. It will need 8MB of flags just for this one variable. Verification Academy Conditional constraint inside inline constraint. class c2 extends c1; int q1[$] = {2,3,4}; constraint c2_c{ . Hi, I have an index register and a vriable, I want to constraint the variable to be inside rised bits in the index register. the constraint disables method is similar to rand_mode() method. When a non-static constraint is turned off using this method, the constraint is turned off in that particular instance of the class which In reply to theketi:. By default all the constraints will be enabled, during the randomization constraint solver will not consider the disabled constraints. So I tried the following :: module UNIQ_via_inside ; class Main ; rand bit [2:0] Hi, I have a class like this class main_class; rand apr_ab apr_ab_obj; rand apr_ac apr_ac_obj; rand apr_ad apr_ad_obj; rand apr_ae apr_ae_obj; endclass each of apr_ab , apr_ac, apr_ad and apr_ae have about 100 interger variables that are rand. Syntax. Amardeep reddy Amardeep reddy. constraint uniq { unique {choices}; unique {chosen}; } Learn how to write SystemVerilog inline constraints with simple examples - SystemVerilog Tutorial for Beginners I have a requirement that there is an address range and there would be some addresses inflight that are not meant to be sent again until inflight txns are completed. For example: class B; rand int x, y; constraint C { x <= F(y); } constraint D { y inside { 2, 4, 8 } ; } endclass forces y to be solved before x. How to resolve randomization failure can be discussed in soft constraint. The same holds for b class, if, for example, you alter the code as: constraint a_c_1 { a inside {[11:100]}; } In this case, the constraint inside b class will suppress Just as with SystemVerilog, constraint blocks are considered virtual, in that a same-named constraint in a sub-class overrides the constraint in the super-class. , bit, I’ve got two random variables; the first one is an enumerated type which selects 1 of 3 “sets”. //!(i1 inside {[2:4]});//solver errors. So there are effectively no constraints on coeff_mult before evaluating the equality constraints. Depending on the randomly chosen set, I need the second random variable “inst” to be confined to a specific list of numbers, specified as an enumerated type. See IEEE Std 1800-2012 § 18. Verilog Menu Toggle. Thus, constraint D is solved separately before constraint C, which uses in SystemVerilog constraints come either through declarative constructs, if-then-else guards in the constraint or in-line constraints (randomize with), or at run-time only through enable/disable. Inline constraints (i. In reply to kernalmode1: What you want is to pick elements of a list, and its the index into the list that needs to be unique. When you get unsupported messages, it means the tool recognizes the construct but has not implemented it In reply to dave_59:. My initial guess was to used a same method. 5. Can anyone please tell what is wrong here. I've the following enum: typedef enum {ADD, SUB, MUL, DIV, MOD} Instr_t; While writing constraints You cannot make assignments inside a constraint block as it only contains expressions. Hello, Below is an example of constraints, where the first implementation doesn’t work, but the second is fine. Agenda • Example Constraints • Constraint Solver • Engineering Constraints 3/2/2022 Jeremy Ridgeway, AvagoTechnologies, Inc. In the below example, addr and data are the two random variables. mode, but it will only update req. randomize(); //i dont want to pass inline constraint to cover 2 and 3 for val in basic class endclass i have another requirement where i want to randomize base seq like class error; Randomization of variables in a class can be disabled using rand_mode method call. The constraint data_size will limit the size of the dynamic array data between 4 to 6. SystemVerilog中的inside是一个非常重要的操作符，它属于集合操作符的一种，主要用于检查一个表达式的值是否位于一个指定的值集合或范围内。这种操作符的使用可以使得编码更为高效和简洁。以下是inside在SystemVerilog中的一些常见使用方法： . Dynamic randomization is achieved essentially by modifying details of an existing constraint, variables within the constraint, and enable/disable, rather than changing the constraint req. , Please go through below code, which generates a continues zero for 10 bits. A constraint solver has to do something similar and the problem grows exponentially as the number of bits increases. The dynamic array should contain 20 items. The variable has to be declared with type rand or randc to enable randomization of the variable. Figure 3 - Overriding Constraints Figure 3, the relationship a > b will hold for all instances of class my_ext_s because the ab_c constraint in the my_ext_s type overrides the ab_c constraint in the my_base_s type. This is very much probabilistic, when you run for more iterations the probability ratio is more accurate. Also, the LRM does not allow expressions of non-integral values in constraints, technically, although some tools allow limited Hello everyone, I was trying to write constraints on class variables in a top level class and the problem is the class handles themselves are dynamic arrays. Now if I randomize an object of main_class , is there any specific order in which the constraint solver solves apr_ab , In reply to yourcheers:. Constraints in a class can be disabled using the constraint_mode method call. 0. Sometimes even after. 1:‘rand’ and ‘randc’ are not currently supported for struct/union member declarations. Here is an example: class constraint_container; rand int unsigned a, b, c; function int unsigned get_a(); return a; endfunction function int unsigned value_of(int unsigned value); return value; endfunction constraint a_constraint { a == 5; // I expect "b" [] The below constraint gives the maximum number of one that the variable can have. Example Testbench • Packet based device – Start of Packet – Header fields – Data to send – CRC – End of Packet • Length 0 – 512 bytes 3/2/2022 Jeremy Set Membership (Inside Operator) Specifying a range of values (or specific allowed values) is quite common, and so there's no need for two separate "relational" conditions to be defined as SystemVerilog provides the inside operator for that purpose. Is my code wrong ? Knight’s tour is a sequence of moves of a knight on a chessboard such that the knight visits every square only once, for more info please check Wikipedia. 1. RAL Model; Transaction Level Modeling (TLM) Interview SystemVerilog allows users to specify constraints in a compact, declarative way which are then processed by an internal solver to generate random values that satisfy all conditions. That's 67,108,864 different values you're asking the simulator to keep track of to see if they've been used before. In reply to Chandrashekhar It's not clear from the SystemVerilog LRM what will happen here, but I suspect that once all the values between low and high are exhausted randomisation will fail. Feb-9-2014 : Set Membership: Sometimes we want to randomize a variable within a set of I am fresh for system Verilog. How do i constraint a below such that it doesnt have back 2 back value of 15? There are other tasks in the same class which will have their own local variable. You essentially had to map out all the possible solutions and randomly pick one of them. Here is the code - class random_value; rand bit [7:0]var1 ; rand in Why am I getting different results when I am using if-else and implication constraints? As these two are considered the same, I think I should not get any difference. Adding a solve before construct only changes how that So, I am trying to generate a deck of 52 cards using constraint. name in global resources for: “inside [0:1024]” val UVM Resource DB UVM Command Line SystemVerilog provides the support to use foreach loop inside a constraint so that arrays can be constrained. You probably should add a constraint that prevents the increment from overflowing based on the number of times you expect to call randomize. Hot Network Questions Number Link Hidden Word Function closure objects are not created when emacs load files in lexical evironment specified in . For this i have considered a variable to generate some random value within 0,21. The inside operator can also be inverted, by adding the negation operator ! before the condition and enclosing the complete expression in parentheses. 3. a == o2_local. Dynamic randomization is achieved essentially by modifying details of an existing constraint, variables within the constraint, and enable/disable, rather than changing the constraint What is happening here is that we are randomizing inside some_sequence's scope. emacs init file at [I] LRM 11. That is to say, you had to sum a zero value of 32 bits to force a casting with the intern item in the sum loop. the Skip to main content SystemVerilog supports ‘if’, ‘else if’, ‘else’ same as other programming languages. constraint_mode() can be called both as a task and as a function. Constraints are written inside curly braces. class Main; rand bit[11:0] arr1[5], arr2[5], arr3[5]; constraint c0{unique {arr1, arr2, arr3};} constraint c1 {foreach(arr1[i]){ !(arr1[i] inside arr2); }}; constraint c2 {foreach(arr1[i]){ !(arr1[i] Hence this would be redundant as load would have these 2 values with equal probability even without the constraint . TESTBENCH. Constraint solver considers both constraints inside the class and inline constraints. inside可以约束data从指定的数据集合中获取数据值，取得每个值的概率是相同的 Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Advertising & Talent Reach devs & technologists worldwide about your product, service or employer brand; OverflowAI GenAI features for Teams; OverflowAPI Train & fine-tune LLMs; Labs The future of collective knowledge sharing; About the company Use the set membership operator inside. Hi Dave , Was going through the forum for functions in constraints examples and saw this example . , 22. IEEE 1800-2012 states that the constraint solve can only handle 2-value logic. constraint constraint_name { var = function_call(); }; Functions in constraints example In reply to kernalmode1:. Writing a complete code inside a constraint block may create confusion. at. let say I have 30 children in the class and I want to choose one child only if is at school today, so I have logic [29:0] children_at_school_today; logic [5:0] choosen_child; if today at school are childrens [2,3,4,5,6,12,13,14,15] Two dimensional array need to allocate size and values like below byte array[i][j]; i and j should be same value i. Click here to refresh loops in SystemVerilog ! Example. Example: In reply to verif_guy12: It would help to show differences in results between what you are expecting and what you are seeing. DLC <= 8. SystemVerilog dist constraint. Either the function input arguments cannot reference any random variables, or the function Learn how to write SystemVerilog inline constraints with simple examples - SystemVerilog Tutorial for Beginners systemverilog中的constraint约束的使用 . field2. !(i1 inside q1); }; endclass. The following simple example can illustrate: eda playground A couple approaches I’ve tried were to simple create You are very limited in how you can use a user defined function inside a constraint. Expression evaluation is identical whether you are inside a constraint or not. Apart from that, each suite should appear 13 times and each rank 4 times. 逻辑关系<,<=,==, >=,> 逻辑关系约束，比较直接的指定随机数产生的范围，<,<=,==, >=,> rand byte data； constraint data_cons{ data > 0 ； data < 5; } // 约束data的值大于0，小于5 . In reply to dave_59:. The requirements are as follows: The variable should be declared as rand bit [63:0] data. Verilog Codes; Verilog Project Ideas; System Verilog Menu Toggle. It should either be a constant like [3:1] or you need to use the +:/-: syntax, e. In randomize function, the solver can’t solve if X or Z is used. constraint INSIDE { d inside { arr } ; } It will work as solver should take care of it to satisfy the constraint. You signed out in another tab or window. Verification Academy Constraint for address to be inside 4k boundary. This works as expected. sum that gets unrolled unto a constant select " I didn't get this part . SystemVerilog does not give you an easy way to turn off both constraints. The code shown below declares a static array called array with size 5. The inside operator can be used for specifying the allowed range or allowed values in general in the form of a set. Constraints are affected by the static keyword only if they are turned on and off using constraint_mode() method. But to run your I have the code for the following constraint: Sum of all array elements must be 17 Array must have at least one element which is multiple of 4. The constraint data_c will constraint the elements of the array to take value less than 20. endclass. Thus, the inherited class can modify constraints based on the requirement. Reload to refresh your session. Constraint expressions may include random variables, non-random state I want to generate an array of prime numbers. For a particular class, constraint blocks can be written inside a class or outside a class using extern keywords. using the foreach loop within the constraint block will make easy to constrain an array. rand bit [7:0] data; constraint myConstraint { data inside {[0:10]}; } Read more on SystemVerilog Constraints. constraint no_overflow { 8'(a+s) == int'(a+s); } Is there a way to use inside operator for every element of enum? for e. Can someone please Tool will consider two different constraint so try to resolve both constraints because Same variable is constrained using two different constraint (Names are different so Child class can't override Base class's constraint) has their name is different and both constraints are contradict to each other. class a; rand int ary[5]; constraint prime_const { foreach(ary[i]) { ary[i] == prime_gen(50); // approach1 ary[i] inside {[2:50]} && (is_prime(ary[i])==1); //approach 2 } } //returns 1 if the provided value is a prime number function int is_prime(int a); for (int c = 2; c if else constraints. assert(at. So assuming we have N*N chessboard, say N=5 for simplicity, whose squares are numbered from 0 to 24, as shown: I wrote the code below to get random array tour_indices for possible indices of the movements, I guess the only way is to declare a rand integral array and use it’s type as argument instead and let it be equal to the reg1[i]. if else block allows conditional executions of constraints. array[count +: 3] meaning, start slicing from index count and take 3 elements from the array. B. One says it isn't currently supported and the other SystemVerilog added case inside, which is better, because it allows ranges to be used (like in your original example): [5:7]: ; // 5,6,7 and because it is asymmetrical. Constraints provide a way to specify the valid range of values for a variable, as well as any relationships or conditions between variables. com/x/X2Up0:45 : Introduction to inside keyword3:20 : Scope randomization ex I have a constraint of the form: s dist {0:= 20, 1:= 25, 2:= 30, <many more, possibly hundreds>}; Instead of writing down the constraint this way, I found in my application the RHS (i. I'm trying to come up with a SystemVerilog constraint which will for e. inside keyword in system verilog constraint. I can put in specific values but that is a mess especially since that list would have to be Now if the constraints defined inside a class and the constraints passed in-line are conflicting then SV will not be able to randomize the variable and randomization will fail. SNUG 2014 29 Constraint Sources • Dynamic constraints only • Val has: – Name – Scope • Lookup scope. To present my problem I put together a stripped off version of my code by referring to other posts, especially the one located here: Constraint for object dynamic array Here is the sample code to represent my In reply to dave_59:. I want to have a constraint which limits the number of Hi, I am generating 5 unique elements in an array using values 1,2,39 whose sum is greater than 20 I use the constrain “data_sum_c” to constraint the sum of elements and with this constraint all values of data are 0; Without the constraint “data_sum_c” i am able to generate unique data values. dickol@samsung. constraint chosen_c { chosen. There is no restriction on system functions as long as they meed the requirements of section 18. Feb-9-2014 : Set Membership: Sometimes we want to randomize a variable within a set of The right hand side of an implication can be a constraint set: constraint example { flag == true -> {other_flag_1 == false; other_flag_2 == false; other_flag_3 == false;}; } Note that when your constraints are Boolean expressions, it’s the same as the logically ANDing them into one Boolean expression In reply to dave_59:. IN - Systemverilog Randomization) and to be safe you had to use:“with (item+32b’b0)”. I need to be able to set a constraint dist with 64 different, changeble weights: I need to random pick an index of range 0~63, when every index has its own weight / probability to be chosen. For example. size() inside {[10:15]};} constraint c1a {inx_num inside In the below transaction class definition, write your own logic in the space provided for you to meet the following requirements. In reply to logie:. — Functions that appear in Constraints can be placed either inside the class body definition or outside it. sum() / unique constraint . obp bba btvlq rsaov xpaom lwgqgu goxvvzz bclc xqumb rgkclx