Question for Hash of multiple number

[felinae98]

I want to prove a given hash is generated from two numbers, but I failed.

I tried:

type TestCircuit struct {
	X1 frontend.Variable
    Hash frontend.Variable `gnark:",public"`
}

func (circuit *TestCircuit) Define(api frontend.API) error {
    hFun, _ := mimc.NewMiMC("seed", api)
    hFun.Write(circuit.X1)
    api.AssertIsEqual(hFun.Sum(), circuit.Hash) 
	return nil
}

func main() {
	var testCircuit TestCircuit
	r1cs, _ := frontend.Compile(ecc.BN254, backend.GROTH16, &testCircuit)
	pk, vk, _ := groth16.Setup(r1cs)
	var witness TestCircuit
    var x1, x2 big.Int
    x1.SetString("12333", 10)
    x2.SetString("456", 10)
	witness.X1 = x1
    hFun := hash.Hash(hash.MIMC_BN254).New("seed")
    hFun.Write(x1.Bytes())
    witness.Hash = hFun.Sum(nil)
	proof, err := groth16.Prove(r1cs, pk, &witness)
    if err != nil {
        fmt.Println(err)
    } else {
        // fmt.Println(proof)
        fmt.Println(groth16.Verify(proof, vk, &witness))
    }
}

and that works fine. But I also tried:

type TestCircuit struct {
	X1 frontend.Variable
	X2 frontend.Variable
    Hash frontend.Variable `gnark:",public"`
}

func (circuit *TestCircuit) Define(api frontend.API) error {
    hFun, _ := mimc.NewMiMC("seed", api)
    hFun.Write(circuit.X1, circuit.X2)
    api.AssertIsEqual(hFun.Sum(), circuit.Hash) 
	return nil
}

func main() {
	var testCircuit TestCircuit
	r1cs, _ := frontend.Compile(ecc.BN254, backend.GROTH16, &testCircuit)
	pk, vk, _ := groth16.Setup(r1cs)
	var witness TestCircuit
    var x1, x2 big.Int
    x1.SetString("12333", 10)
    x2.SetString("456", 10)
	witness.X1 = x1
	witness.X2 = x2
    hFun := hash.Hash(hash.MIMC_BN254).New("seed")
    hFun.Write(x1.Bytes())
    hFun.Write(x2.Bytes())
    witness.Hash = hFun.Sum(nil)
	proof, err := groth16.Prove(r1cs, pk, &witness)
    if err != nil {
        fmt.Println(err)
    } else {
        // fmt.Println(proof)
        fmt.Println(groth16.Verify(proof, vk, &witness))
    }
}

but this gave me:

constraint is not satisfied: [assertIsEqual] (0 + 12333 + 456 + 10778428360887491543069470341620729056566098386560344136342894035537057373845 + 9463329092544481559505915838510141988305123544831892312301996822100883691616) == 14432044478723972601372188371084787884890931508824727405645241992234761304228
r1cs.(*r1CS).AssertIsEqual
	assertions.go:34
main.(*TestCircuit).Define
	main.go:24

I wonder how can I get the hash of two numbers.

[gbotrel]

@ThomasPiellard