efficiency of scalar-field multiplication about mcl HOT 6 OPEN

The cost of the constructor Fr(int) is almost the same as that of Fr::mul because it uses Montgomery conversion.
i*Fr(100) is equal to Fr(i)*Fr(100).

If you need many small integer multiplication, then, for example, how about making a table of Fr and using it?

const int N = 256;
static Fr FrTbl[N];
for (int i = 0; i < N; i++) {
  FrTbl[i] = i;
}

Or you can use Fr::mulSmall(Fr& z, const Fr& x, uint32_t y) for y in [0, 9].

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The cost of the constructor Fr(int) is almost the same as that of Fr::mul because it uses Montgomery conversion. i*Fr(100) is equal to Fr(i)*Fr(100).

If you need many small integer multiplication, then, for example, how about making a table of Fr and using it?

const int N = 256;
static Fr FrTbl[N];
for (int i = 0; i < N; i++) {
  FrTbl[i] = i;
}

Or you can use Fr::mulSmall(Fr& z, const Fr& x, uint32_t y) for y in [0, 9].

Thanks for your reply. Actually I want is a dot product between a vector of many field elements, and a vector of many small integers(0-255). I am wondering whether there is a better way to implement it instead of directly using Fr(int) then multiply with the field elements.

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Fr::mul is one of the fastest implementations in the world.
How much faster do you expect it to be if I implement the multiplication of Fr and an integer?
If implemented, it would not be many times faster.
Fr::mulSmall contains mulUnit 256bit x 64bit -> 320bit, table lookup (or 2-time mulUnit), and 2-time sub or some bit operations.
The benchmark of Fr::mulSmall (Fr is a 256-bit integer) and Fp::mul is the following:

If you still want it, I will consider implementing it, but it is not a high priority.

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Thanks, I found out that modifying the constant 9 to 255 in gmp_utils.hpp seems to work. Is this the correct way?

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I'm sorry I missed your question. I think it's probably okay. I'll check back later when I get more time.

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