# System Verilog : Array Reduction & Array Ordering Methods

Array reduction methods can be applied to any unpacked array. The “with” clause can be used to specify the item to be used in the reduction.

sum() :
returns the sum of all the array elements.

product() :
returns the product of all the array elements

and() :
returns the bit-wise AND(&) of all the array elements.

or() :
returns the bit-wise OR(|) of all the array elements.

xor() :
returns the logical XOR (^) of all the array elements.

```module array_reduction;

int myarr [8:0];
logic larr [7:0];
int rsum,rprod,rxor,rnd,ror;

initial
begin
myarr = {6,3,1,2,4,8,5,7,9};
larr = {1,0,1,0,1,1,1,0};

rsum = myarr.sum();
\$display("sum = %0d", rsum);

rprod = myarr.product();
\$display("product = %0d", rprod);

rxor = myarr.xor();
\$display("Xor = %0b", rxor);

rxor = larr.xor with ( item + 1); //  11 ^  01 ^  11 ^  01 ^  11 ^  11 ^  11 ^ 01
\$display("Xor for larr - with clause = %0d", rxor);

rnd = larr.and();
\$display("And = %0b", rnd);

ror = larr.or();
\$display("Or = %0b", ror);

end
endmodule
/*
ncsim> run
sum = 45
product = 362880
Xor = 1
Xor for larr - with clause = 3
And = 0
Or = 1
*/
```

In the above code, sum is the sum of all elements in the array. The execution of xor method has been done on myarr and larr. With larr with clause is used which will add 1 to each element and then do xor.

Array Ordering Methods:
Array ordering methods reorder the elements of any unpacked array (fixed or dynamically sized) except for associative arrays.

reverse() :
It reverses the order of the elements in the array. The `with` clause cannot be specified with this.

sort() :
It sorts the array in ascending order.

rsort() :
It sorts the array in descending order.For both `sort` and `rsort`, the `with` clause (and its expression) is optional when the relational operators (<, >, ==) are defined for the array element type. If a `with` clause is specified, the relational operators(<, >, ==) shall be defined for the type of the expression.

shuffle() :
It randomizes the order of the elements in the array. The `with` clause cannot be specified with this.

```module array_order;
int myarr [9:0];

initial
begin
myarr = {60,0,30,10,20,40,80,50,70,90};
display(myarr,"Array myarr");

myarr.reverse;
display(myarr,"myarr.reverse() function");

myarr.sort();
display(myarr,"myarr.sort() function");

myarr.rsort;
display(myarr,"myarr.rsort() function");

myarr.shuffle;
display(myarr,"myarr.shuffle() function");

myarr.shuffle;
display(myarr,"myarr.shuffle() function Again!!");
end

\$display(str);
for (int i=0; i<10;i++) \$write(" %0d ",myarr[i]);
\$display("\n");
return;
endmodule
/*
ncsim> run
Array myarr
90  70  50  80  40  20  10  30  0  60

myarr.reverse() function
60  0  30  10  20  40  80  50  70  90

myarr.sort() function
0  10  20  30  40  50  60  70  80  90

myarr.rsort() function
90  80  70  60  50  40  30  20  10  0

myarr.shuffle() function
0  10  30  40  20  90  60  70  80  50

myarr.shuffle() function Again!!
30  10  40  60  20  80  70  50  0  90
*/
```

Sini has spent more than a dozen years in the semiconductor industry, focusing mostly on verification. She is an expert on Formal Verification and has written international papers and articles on related topics.

## 5 comments on “System Verilog : Array Reduction & Array Ordering Methods”

1. sharan

Could add differences between like task and function, program and module block?
What can we use inside module and program block and same way, what not to use ?(for example, can we use always block inside program block ,similar to that ).
Please email me if you want further any.
I am fresher so I will encounter these questions. Just sharing

1. Vijaykanth Ch

Hi sir/mam,