Remove MPZ usage from fourier

src/common/fourier.c

@@ -28,11 +28,10 @@ void fft(size_t arr, mclBnFr domain[], mclBnFr *o)
     }
 }
 
-void ifft(size_t arr, mclBnFr domain[], mclBnFr *o, mpz_t *Ne)
+void ifft(size_t arr, mclBnFr domain[], mclBnFr *o)
 {
     fft(arr, domain, o);
 
-    mpz_t factor, factor2;
     mclBnFr out[arr];
     mclBnFr frFactor;
 
@@ -41,17 +40,10 @@ void ifft(size_t arr, mclBnFr domain[], mclBnFr *o, mpz_t *Ne)
         out[i] = o[i];
     }
 
-    mpz_init(factor2);
-    mpz_powm(factor2, shift, *Ne, pPrime);
-    mpz_sub_ui(factor2, factor2, 1);
-    mpz_invert(factor2, factor2, pPrime);
+    mclBnFr_setInt(&frFactor, arr);
+    mclBnFr_inv(&frFactor, &frFactor);
+    mclBnFr_mul(&frFactor, &frFactor, &shift_fft);
 
-    mpz_init_set_ui(factor, arr);
-    mpz_invert(factor, factor, pPrime);
-    mpz_mul(factor, factor, factor2);
-    mpz_mod(factor, factor, pPrime);
-
-    mpz_to_fr(&frFactor, &factor);
     mclBnFr_mul(&o[0], &out[0], &frFactor);
 
     for (int i = 1; i < arr; i++)
@@ -71,14 +63,11 @@ void ifft_t(size_t arr, mclBnFr domain[], mclBnFr *o)
         out[i] = o[i];
     }
 
-    mclBnFr frFactor;
-    mpz_to_fr(&frFactor, &rsigma[0]);
-    mclBnFr_mul(&o[0], &out[0], &frFactor);
+    mclBnFr_mul(&o[0], &out[0], &rsigmaFr[0]);
 
     for (int i = 1; i < arr; i++)
     {
-        mpz_to_fr(&frFactor, &rsigma[i]);
-        mclBnFr_mul(&o[i], &out[arr-i], &frFactor);
+        mclBnFr_mul(&o[i], &out[arr-i], &rsigmaFr[i]);
     }
 
     fft(arr, domain, o);

src/common/utils.c

@@ -73,20 +73,28 @@ void init_prover(void *circuit, proving_key pk)
     if (bench) printf("  |--- FFT domain size : %d\n", n);
 
     rsigma = (mpz_t*) malloc((n) * sizeof(mpz_t)); 
+    rsigmaFr = (mclBnFr*) malloc((n) * sizeof(mclBnFr)); 
     rsigmaInv = (mpz_t*) malloc((n) * sizeof(mpz_t)); 
 
     mpz_t randNum;
     mpz_init(randNum);
-    mpz_t factor;
+    mpz_t factor, shift_fft_mpz;
     mpz_init_set_ui(factor, n);
     mpz_invert(factor, factor, pPrime);
     mpz_init(shift);
+    mpz_init(shift_fft_mpz);
 
     mclBnFr rand;
     generate_random_scalar(&rand);
     fr_to_mpz(&randNum, &rand);
     mpz_set(shift, randNum);
 
+    mpz_powm(shift_fft_mpz, shift, pk.Ne, pPrime);
+    mpz_sub_ui(shift_fft_mpz, shift_fft_mpz, 1);
+    mpz_invert(shift_fft_mpz, shift_fft_mpz, pPrime);
+
+    mpz_to_fr(&shift_fft, &shift_fft_mpz);
+
     mpz_init2(rsigma[0], BITS);
     mpz_init2(rsigmaInv[0], BITS);
     mpz_set_ui(rsigma[0], 1);
@@ -97,6 +105,7 @@ void init_prover(void *circuit, proving_key pk)
     mclBnG1_mul(&pk.xt1_rand[0], &pk.xt1[0], &frFactor);
     mpz_mul(rsigma[0], rsigma[0], factor);
     mpz_mod(rsigma[0], rsigma[0], pPrime);
+    mpz_to_fr(&rsigmaFr[0], &rsigma[0]);
 
     for (int i = 1; i < n; i++)
     {
@@ -111,6 +120,7 @@ void init_prover(void *circuit, proving_key pk)
 
         mpz_mul(rsigma[i], rsigma[i], factor);
         mpz_mod(rsigma[i], rsigma[i], pPrime);
+        mpz_to_fr(&rsigmaFr[i], &rsigma[i]);
     }
 
     clock_gettime(CLOCK_MONOTONIC, &end);

src/gro16/gro16.h

@@ -46,8 +46,10 @@ static mclBnFr *BsFr;
 static mclBnFr *CsFr;
 
 static mpz_t *rsigma;
+static mclBnFr *rsigmaFr;
 static mpz_t *rsigmaInv;
 static mpz_t shift;
+static mclBnFr shift_fft;
 
 static mpz_t *wM;
 

src/gro16/prover.c

@@ -89,7 +89,7 @@ void h_coefficients(proving_key pk)
         mclBnFr_sub(&AsFr[i], &AsFr[i], &CsFr[i]);
     }
 
-    ifft(n, pk.wMFr, AsFr, &pk.Ne);
+    ifft(n, pk.wMFr, AsFr);
 }
 
 void mul_exp(struct mulExpResult *result, mpz_t *uwProof, proving_key pk)