def _step(i, pkm1, pkm2, qkm1, qkm2, k1, k2, k3, k4, k5, k6, k7, k8, r):
xk = -(x * k1 * k2) / (k3 * k4)
pk = pkm1 + pkm2 * xk
qk = qkm1 + qkm2 * xk
pkm2 = pkm1
pkm1 = pk
qkm2 = qkm1
qkm1 = qk
xk = (x * k5 * k6) / (k7 * k8)
pk = pkm1 + pkm2 * xk
qk = qkm1 + qkm2 * xk
pkm2 = pkm1
pkm1 = pk
qkm2 = qkm1
qkm1 = qk
old_r = r
r = aet.switch(aet.eq(qk, zero), r, pk / qk)
k1 += one
k2 += k26update
k3 += two
k4 += two
k5 += one
k6 -= k26update
k7 += two
k8 += two
big_cond = aet.gt(aet.abs_(qk) + aet.abs_(pk), BIG)
biginv_cond = aet.or_(aet.lt(aet.abs_(qk), BIGINV),
aet.lt(aet.abs_(pk), BIGINV))
pkm2 = aet.switch(big_cond, pkm2 * BIGINV, pkm2)
pkm1 = aet.switch(big_cond, pkm1 * BIGINV, pkm1)
qkm2 = aet.switch(big_cond, qkm2 * BIGINV, qkm2)
qkm1 = aet.switch(big_cond, qkm1 * BIGINV, qkm1)
pkm2 = aet.switch(biginv_cond, pkm2 * BIG, pkm2)
pkm1 = aet.switch(biginv_cond, pkm1 * BIG, pkm1)
qkm2 = aet.switch(biginv_cond, qkm2 * BIG, qkm2)
qkm1 = aet.switch(biginv_cond, qkm1 * BIG, qkm1)
return (
(pkm1, pkm2, qkm1, qkm2, k1, k2, k3, k4, k5, k6, k7, k8, r),
until(aet.abs_(old_r - r) < (THRESH * aet.abs_(r))),
)
def _step(i, t, s):
t *= (i - b) * value / i
step = t / (a + i)
s += step
return ((t, s), until(aet.abs_(step) < threshold))