static GEN
bound_for_coeff(long m, GEN rr, GEN *maxroot)
{
long i,r1, lrr=lg(rr);
GEN p1,b1,b2,B,M, C = matpascal(m-1);
for (r1=1; r1 < lrr; r1++)
if (typ(rr[r1]) != t_REAL) break;
r1--;
rr = gabs(rr,0); *maxroot = vecmax(rr);
for (i=1; i<lrr; i++)
if (gcmp(gel(rr,i), gen_1) < 0) gel(rr,i) = gen_1;
for (b1=gen_1,i=1; i<=r1; i++) b1 = gmul(b1, gel(rr,i));
for (b2=gen_1 ; i<lrr; i++) b2 = gmul(b2, gel(rr,i));
B = gmul(b1, gsqr(b2)); /* Mahler measure */
M = cgetg(m+2, t_VEC); gel(M,1) = gel(M,2) = gen_0; /* unused */
for (i=1; i<m; i++)
{
p1 = gadd(gmul(gcoeff(C, m, i+1), B),/* binom(m-1, i) */
gcoeff(C, m, i)); /* binom(m-1, i-1) */
gel(M,i+2) = ceil_safe(p1);
}
return M;
}
/* fill M[xoff+i, yoff+j] with the contents of c ( c * Id_n if scalar ) */
static void
matfill(GEN M, GEN c, long xoff, long yoff, long n)
{
long i, j, h, l;
l = lg(c); if (l == 1) return;
switch(typ(c))
{
case t_VEC:
for (i = 1; i < l; i++)
gcoeff(M,xoff+1,yoff+i) = gel(c,i);
break;
case t_COL:
for (i = 1; i < l; i++)
gcoeff(M,xoff+i,yoff+1) = gel(c,i);
break;
case t_MAT:
h = lgcols(c);
for (j = 1; j < l; j++)
for (i = 1; i < h; i++) gcoeff(M,xoff+i,yoff+j) = gcoeff(c,i,j);
break;
default:
for (i = 1; i <= n; i++)
gcoeff(M, xoff+i, yoff+i) = c;
break;
}
}
static void
bestlift_init(long a, GEN nf, GEN pr, GEN C, nflift_t *L)
{
const long D = 100;
const double alpha = ((double)D-1) / D; /* LLL parameter */
const long d = degpol(nf[1]);
pari_sp av = avma;
GEN prk, PRK, B, GSmin, pk;
pari_timer ti;
TIMERstart(&ti);
if (!a) a = (long)bestlift_bound(C, d, alpha, pr_norm(pr));
for (;; avma = av, a<<=1)
{
if (DEBUGLEVEL>2) fprintferr("exponent: %ld\n",a);
PRK = prk = idealpows(nf, pr, a);
pk = gcoeff(prk,1,1);
/* reduce size first, "scramble" matrix */
PRK = lllintpartial_ip(PRK);
/* now floating point reduction is fast */
PRK = lllint_fp_ip(PRK, 4);
PRK = lllint_i(PRK, D, 0, NULL, NULL, &B);
if (!PRK) { PRK = prk; GSmin = pk; } /* nf = Q */
else
{
pari_sp av2 = avma;
GEN S = invmat( get_R(PRK) ), BB = GS_norms(B, DEFAULTPREC);
GEN smax = gen_0;
long i, j;
for (i=1; i<=d; i++)
{
GEN s = gen_0;
for (j=1; j<=d; j++)
s = gadd(s, gdiv( gsqr(gcoeff(S,i,j)), gel(BB,j)));
if (gcmp(s, smax) > 0) smax = s;
}
GSmin = gerepileupto(av2, ginv(gmul2n(smax, 2)));
}
if (gcmp(GSmin, C) >= 0) break;
}
if (DEBUGLEVEL>2)
fprintferr("for this exponent, GSmin = %Z\nTime reduction: %ld\n",
GSmin, TIMER(&ti));
L->k = a;
L->den = L->pk = pk;
L->prk = PRK;
L->iprk = ZM_inv(PRK, pk);
L->GSmin= GSmin;
L->prkHNF = prk;
init_proj(L, gel(nf,1), gel(pr,1));
}
GEN
bnflogdegree(GEN nf, GEN A, GEN ell)
{
pari_sp av = avma;
GEN AZ, A0Z, NA0;
long vAZ;
if (typ(ell) != t_INT) pari_err_TYPE("bnflogdegree", ell);
nf = checknf(nf);
A = idealhnf(nf, A);
AZ = gcoeff(A,1,1);
vAZ = Z_pvalrem(AZ, ell, &A0Z);
if (is_pm1(A0Z))
NA0 = gen_1;
else
(void)Z_pvalrem(idealnorm(nf,A), ell, &NA0);
if (vAZ)
{
GEN Aell = ZM_hnfmodid(A, powiu(ell,vAZ));
GEN S = idealprimedec(nf, ell), T;
long l, i, s = 0;
T = padicfact(nf, S, 100);
l = lg(S);
for (i = 1; i < l; i++)
{
GEN P = gel(S,i);
long v = idealval(nf, Aell, P);
if (v) s += v * ftilde(nf, P, gel(T,i));
}
if (s) NA0 = gmul(NA0, gpowgs(ell1(ell), s));
}
return gerepileupto(av, NA0);
}
/* K a bnf, compute Cl'(K) = ell-Sylow of Cl(K) / (places above ell).
* Return [D, u, R0, U0, ordS]
* - D: cyclic factors for Cl'(K)
* - u: generators of cyclic factors (all coprime to ell)
* - R0: subgroup isprincipal(<S>) (divides K.cyc)
* - U0: generators of R0 are of the form S . U0
* - ordS[i] = order of S[i] in CL(K) */
static GEN
CL_prime(GEN K, GEN ell, GEN Sell)
{
GEN g, ordS, R0, U0, U, D, u, cyc = bnf_get_cyc(K);
long i, l, lD, lS = lg(Sell);
g = leafcopy(bnf_get_gen(K));
l = lg(g);
for (i = 1; i < l; i++)
{
GEN A = gel(g,i), a = gcoeff(A,1,1);
long v = Z_pvalrem(a, ell, &a);
if (v) gel(g,i) = hnfmodid(A, a); /* make coprime to ell */
}
R0 = cgetg(lS, t_MAT);
ordS = cgetg(lS, t_VEC);
for (i = 1; i < lS; i++)
{
gel(R0,i) = isprincipal(K, gel(Sell,i));
gel(ordS,i) = charorder(cyc, gel(R0,i)); /* order of Sell[i] */
}
R0 = shallowconcat(R0, diagonal_shallow(cyc));
/* R0 = subgroup generated by S in Cl(K) [ divides diagonal(K.cyc) ]*/
R0 = ZM_hnfall(R0, &U0, 2); /* [S | cyc] * U0 = R0 in HNF */
D = ZM_snfall(R0, &U,NULL);
D = RgM_diagonal_shallow(D);
lD = lg(D);
u = ZM_inv(U, gen_1); settyp(u, t_VEC);
for (i = 1; i < lD; i++) gel(u,i) = idealfactorback(K,g,gel(u,i),1);
setlg(U0, l);
U0 = rowslice(U0,1,lS-1); /* restrict to 'S' part */
return mkvec5(D, u, R0, U0, ordS);
}
static GEN
init_traces(GEN ff, GEN T, GEN p)
{
long N = degpol(T),i,j,k, r = lg(ff);
GEN Frob = FpXQ_matrix_pow(FpXQ_pow(pol_x[varn(T)],p, T,p), N,N, T,p);
GEN y,p1,p2,Trk,pow,pow1;
k = degpol(ff[r-1]); /* largest degree in modular factorization */
pow = cgetg(k+1, t_VEC);
gel(pow,1) = gen_0; /* dummy */
gel(pow,2) = Frob;
pow1= cgetg(k+1, t_VEC); /* 1st line */
for (i=3; i<=k; i++)
gel(pow,i) = FpM_mul(gel(pow,i-1), Frob, p);
gel(pow1,1) = gen_0; /* dummy */
for (i=2; i<=k; i++)
{
p1 = cgetg(N+1, t_VEC);
gel(pow1,i) = p1; p2 = gel(pow,i);
for (j=1; j<=N; j++) gel(p1,j) = gcoeff(p2,1,j);
}
/* Trk[i] = line 1 of x -> x + x^p + ... + x^{p^(i-1)} */
Trk = pow; /* re-use (destroy) pow */
gel(Trk,1) = vec_ei(N,1);
for (i=2; i<=k; i++)
gel(Trk,i) = gadd(gel(Trk,i-1), gel(pow1,i));
y = cgetg(r, t_VEC);
for (i=1; i<r; i++) y[i] = Trk[degpol(ff[i])];
return y;
}
static GEN
row_transposecopy(GEN A, long x0)
{
long i, lB = lg(A);
GEN B = cgetg(lB, t_COL);
for (i=1; i<lB; i++) gel(B, i) = gcopy(gcoeff(A, x0, i));
return B;
}
static GEN
get_R(GEN M)
{
GEN R;
long i, l, prec = DEFAULTPREC + (gexpo(M) >> TWOPOTBITS_IN_LONG);
for(;;)
{
R = sqred1_from_QR(M, prec);
if (R) break;
prec = (prec-1)<<1;
}
l = lg(R);
for (i=1; i<l; i++) gcoeff(R,i,i) = gen_1;
return R;
}
GEN
shallowmatconcat(GEN v)
{
long i, j, h, l = lg(v), L = 0, H = 0;
GEN M, maxh, maxl;
if (l == 1) return cgetg(1,t_MAT);
switch(typ(v))
{
case t_VEC:
for (i = 1; i < l; i++)
{
GEN c = gel(v,i);
GEN s = _matsize(c);
H = maxss(H, s[1]);
L += s[2];
}
M = zeromatcopy(H, L);
L = 0;
for (i = 1; i < l; i++)
{
GEN c = gel(v,i);
GEN s = _matsize(c);
matfill(M, c, 0, L, 1);
L += s[2];
}
return M;
case t_COL:
for (i = 1; i < l; i++)
{
GEN c = gel(v,i);
GEN s = _matsize(c);
H += s[1];
L = maxss(L, s[2]);
}
M = zeromatcopy(H, L);
H = 0;
for (i = 1; i < l; i++)
{
GEN c = gel(v,i);
GEN s = _matsize(c);
matfill(M, c, H, 0, 1);
H += s[1];
}
return M;
case t_MAT:
h = lgcols(v);
maxh = zero_zv(h-1);
maxl = zero_zv(l-1);
for (j = 1; j < l; j++)
for (i = 1; i < h; i++)
{
GEN c = gcoeff(v,i,j);
GEN s = _matsize(c);
if (s[1] > maxh[i]) maxh[i] = s[1];
if (s[2] > maxl[j]) maxl[j] = s[2];
}
for (i = 1, H = 0; i < h; i++) H += maxh[i];
for (j = 1, L = 0; j < l; j++) L += maxl[j];
M = zeromatcopy(H, L);
for (j = 1, L = 0; j < l; j++)
{
for (i = 1, H = 0; i < h; i++)
{
GEN c = gcoeff(v,i,j);
matfill(M, c, H, L, minss(maxh[i], maxl[j]));
H += maxh[i];
}
L += maxl[j];
}
return M;
default:
pari_err_TYPE("shallowmatconcat", v);
return NULL;
}
}
static GEN
bnflog_i(GEN bnf, GEN ell)
{
long prec0, prec;
GEN nf, US, vdegS, S, T, M, CLp, CLt, Ftilde, vtG, ellk;
GEN D, Ap, cycAp, bnfS;
long i, j, lS, lvAp;
checkbnf(bnf);
nf = checknf(bnf);
S = idealprimedec(nf, ell);
bnfS = bnfsunit0(bnf, S, nf_GENMAT, LOWDEFAULTPREC); /* S-units */
US = leafcopy(gel(bnfS,1));
prec0 = maxss(30, vtilde_prec(nf, US, ell));
US = shallowconcat(bnf_get_fu(bnf), US);
settyp(US, t_COL);
T = padicfact(nf, S, prec0);
lS = lg(S); Ftilde = cgetg(lS, t_VECSMALL);
for (j = 1; j < lS; j++) Ftilde[j] = ftilde(nf, gel(S,j), gel(T,j));
CLp = CL_prime(bnf, ell, S);
cycAp = gel(CLp,1);
Ap = gel(CLp,2);
for(;;)
{
CLt = CL_tilde(nf, US, ell, T, Ftilde, &vtG, prec0);
if (CLt) break;
prec0 <<= 1;
T = padicfact(nf, S, prec0);
}
prec = ellexpo(cycAp, ell) + ellexpo(CLt,ell) + 1;
if (prec == 1) return mkvec3(cgetg(1,t_VEC), cgetg(1,t_VEC), cgetg(1,t_VEC));
vdegS = get_vdegS(Ftilde, ell, prec0);
ellk = powiu(ell, prec);
lvAp = lg(Ap);
if (lvAp > 1)
{
GEN Kcyc = bnf_get_cyc(bnf);
GEN C = zeromatcopy(lvAp-1, lS-1);
GEN Rell = gel(CLp,3), Uell = gel(CLp,4), ordS = gel(CLp,5);
for (i = 1; i < lvAp; i++)
{
GEN a, b, bi, A = gel(Ap,i), d = gel(cycAp,i);
bi = isprincipal(bnf, A);
a = vecmodii(ZC_Z_mul(bi,d), Kcyc);
/* a in subgroup generated by S = Rell; hence b integral */
b = hnf_invimage(Rell, a);
b = vecmodii(ZM_ZC_mul(Uell, ZC_neg(b)), ordS);
A = mkvec2(A, cgetg(1,t_MAT));
A = idealpowred(nf, A, d);
/* find a principal representative of A_i^cycA_i up to elements of S */
a = isprincipalfact(bnf,gel(A,1),S,b,nf_GENMAT|nf_FORCE);
if (!gequal0(gel(a,1))) pari_err_BUG("bnflog");
a = famat_mul_shallow(gel(A,2), gel(a,2)); /* principal part */
if (lg(a) == 1) continue;
for (j = 1; j < lS; j++)
gcoeff(C,i,j) = vtilde(nf, a, gel(T,j), gel(vdegS,j), ell, prec0);
}
C = gmod(gneg(C),ellk);
C = shallowtrans(C);
M = mkmat2(mkcol2(diagonal_shallow(cycAp), C), mkcol2(gen_0, vtG));
M = shallowmatconcat(M); /* relation matrix */
}
else
M = vtG;
M = ZM_hnfmodid(M, ellk);
D = matsnf0(M, 4);
if (lg(D) == 1 || !dvdii(gel(D,1), ellk))
pari_err_BUG("bnflog [missing Z_l component]");
D = vecslice(D,2,lg(D)-1);
return mkvec3(D, CLt, ellsylow(cycAp, ell));
}
