System verilog constraint

[ajay_garg]

Hi Guyz,

I need help in writing constraint for a 3x3 matrix which is of bit type and i need to constraint it in such a manner, that sum of all elements of 3x3 matrix is 6.
Note. I am not able to do sum on this two dimensional matrix within constraints as .sum is applicable to single dimension.
Share your codes please.

[dave_59]

Problem array

In reply to peter: You have two problems. The array reduction methods like sum() all work on one dimension of an array. You need to sum() the sum() of each dimension. The other problem is the result of a relational operator is a single bit, true or false. You need to cast the result to a larger width. m.sum(d1) with (d1.sum(d2) with (int'(d2>4))

[achyuthag21]

I am still a student so don’t know if this is a good solution. I tried a lot of things like matrix.sum with (item.sum) but that didn’t work. In the end the good old brute force method worked. The code is given below:

constraint c1{(matrix[0][0]+matrix[0][1]+matrix[0][2]
                      +matrix[1][0]+matrix[1][1]+matrix[1][2]
                      +matrix[2][0]+matrix[2][1]+matrix[2][2]
) == 6;}

[dave_59]

When using the brute force method, there is one equation where the operands are expanded to the widest operand’s width.m In your case, the operand 6 is a decimal signed integer whose width is 32-bits.

As mentioned in the link I provided earlier, the sum() reduction method evaluates the sum as a function call that returns a result with the same width as each array element. It doesn’t consider the width of the rest of the operands outside the method when determining the width of the result.