Fixed-Point Arithmetic: Precision and Performance

Miscellaneous
1

Nowadays, a native fixed-point arithmetic is supported by Solidity, eliminating the need for external libraries and streamlining calculations involving fractional numbers. What about smartpy and michelson?

2

Hi @Araven_Poubelle

We have implemented a standard library for SmartPy, with some support for fixed-point arithmetic. A few test cases are available here:

import smartpy as sp


@sp.module
def M():
    class C(sp.Contract):
        def __init__(self):
            pass

        @sp.private
        def test_fixed_point(self):
            assert fp.mk((123, 2)) == sp.record(value=sp.int(123), exponent=2)

        @sp.private
        def test_add(self):
            v1 = fp.mk((123, 2))
            v2 = fp.mk((245, 2))
            assert fp.add((v1, v2)) == sp.record(value=sp.int(368), exponent=2)

        @sp.private
        def test_sub(self):
            v1 = fp.mk((245, 2))
            v2 = fp.mk((123, 2))
            assert fp.sub((v1, v2)) == sp.record(value=sp.int(122), exponent=2)

        @sp.private
        def test_mul(self):
            v1 = fp.mk((123, 3))
            v2 = fp.mk((25, 1))
            assert fp.mul((v1, v2)) == sp.record(value=sp.int(3075), exponent=4)

        @sp.private
        def test_eq(self):
            v1 = fp.mk((123, 3))
            v2 = fp.mk((25, 3))
            v3 = fp.mk((25, 3))
            assert not fp.eq((v1, v2))
            assert fp.eq((v2, v3))

        @sp.private
        def test_lt(self):
            v1 = fp.mk((123, 3))
            v2 = fp.mk((25, 3))
            v3 = fp.mk((25, 3))
            assert not fp.lt((v1, v2))
            assert not fp.lt((v2, v3))
            assert fp.lt((v2, v1))
            assert fp.lt((v3, v1))

        @sp.private
        def test_gt(self):
            v1 = fp.mk((123, 3))
            v2 = fp.mk((25, 3))
            v3 = fp.mk((25, 3))
            assert fp.gt((v1, v2))
            assert not fp.gt((v2, v3))
            assert not fp.gt((v2, v1))
            assert not fp.gt((v3, v1))

        @sp.entrypoint
        def ep(self):
            self.test_fixed_point()
            self.test_add()
            self.test_sub()
            self.test_mul()
            self.test_eq()
            self.test_lt()
            self.test_gt()


@sp.add_test()
def test():
    s = sp.test_scenario("Test", [sp.fp, M])
    c = M.C()
    s += c
    c.ep()

Please, let us know if you have further questions or possible improvements to this library.

1 Like
3

Thank @Rodrigo_Bonifacio !
Do you also have implemented more math functions, such as trigonometric, exponential, logarithmic and so on?

4

Hi @Araven_Poubelle. Our current math library implements just a few functions, including exponential, greatest common divisor, and least common multiple.