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permit finite eval of coulomb_f at z = 0

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This commit is contained in:
fredrik 2019-02-28 17:18:56 +01:00
parent bd4359adeb
commit 19777bff75
2 changed files with 29 additions and 7 deletions
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29
acb_hypgeom/coulomb.c
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@ -147,11 +147,7 @@ _acb_hypgeom_coulomb(acb_t F, acb_t G, acb_t Hpos, acb_t Hneg, const acb_t l, co
} }
} }
/* h = log(2z) */ /* C = exp((-pi eta + lu + lv)/2) */
acb_mul_2exp_si(h, z, 1);
acb_log(h, h, prec);
/* C = exp(h l + (-pi eta + lu + lv)/2) */
acb_const_pi(C, prec); acb_const_pi(C, prec);
acb_mul(C, C, eta, prec); acb_mul(C, C, eta, prec);
acb_neg(C, C); acb_neg(C, C);
@ -169,7 +165,6 @@ _acb_hypgeom_coulomb(acb_t F, acb_t G, acb_t Hpos, acb_t Hneg, const acb_t l, co
} }
acb_mul_2exp_si(C, C, -1); acb_mul_2exp_si(C, C, -1);
acb_addmul(C, h, l, prec);
if (asymp) if (asymp)
{ {
@ -214,7 +209,27 @@ _acb_hypgeom_coulomb(acb_t F, acb_t G, acb_t Hpos, acb_t Hneg, const acb_t l, co
acb_hypgeom_m(F, v, m, z1, 1, prec); acb_hypgeom_m(F, v, m, z1, 1, prec);
} }
acb_exp(C, C, prec); if (acb_contains_zero(z))
{
acb_exp(C, C, prec);
/* (2z)^l without logarithm */
acb_mul_2exp_si(h, z, 1);
acb_pow(h, h, l, prec);
acb_mul(C, C, h, prec);
/* h = log(2z) */
acb_indeterminate(h);
}
else
{
/* h = log(2z) */
acb_mul_2exp_si(h, z, 1);
acb_log(h, h, prec);
acb_addmul(C, h, l, prec);
acb_exp(C, C, prec);
}
acb_mul(F, F, C, prec); acb_mul(F, F, C, prec);
if (F_real) if (F_real)
arb_zero(acb_imagref(F)); arb_zero(acb_imagref(F));

7
acb_hypgeom/test/t-coulomb.c
View file

@ -87,6 +87,13 @@ int main()
mask = n_randlimb(state); mask = n_randlimb(state);
if (n_randint(state, 2) == 0)
{
acb_randtest_param(t, state, 1 + n_randint(state, 200), 1 + n_randint(state, 100));
acb_add(z, z, t, prec2);
acb_sub(z, z, t, prec2);
}
/* also test aliasing */ /* also test aliasing */
acb_set(G2, z); acb_set(G2, z);