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Simplify group generic algorithm #40537

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Merged
merged 2 commits into from
Aug 16, 2025
Merged

Simplify group generic algorithm #40537

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75ec6cc
Simplify group generic algorithm
user202729 Aug 3, 2025
07873ba
Address reviewer comments
user202729 Aug 4, 2025
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15 changes: 12 additions & 3 deletions src/sage/groups/generic.py
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Original file line number Diff line number Diff line change
Expand Up @@ -951,7 +951,14 @@ def discrete_log(a, base, ord=None, bounds=None, operation='*', identity=None, i
ord = integer_ring.ZZ(ord)
try:
if ord == Infinity:
return bsgs(base, a, bounds, identity=identity, inverse=inverse, op=op, operation=operation)
if algorithm == 'bsgs':
return bsgs(base, a, bounds, identity=identity, inverse=inverse, op=op, operation=operation)
elif algorithm == 'lambda':
return discrete_log_lambda(base, a, bounds, inverse=inverse, identity=identity, op=op, operation=operation)
elif algorithm == 'rho':
raise ValueError('pollard rho algorithm does not work with infinite order elements')
else:
raise ValueError(f"unknown algorithm {algorithm}")
if base == power(base, 0) and a != base:
raise ValueError
f = ord.factor()
Expand Down Expand Up @@ -984,6 +991,8 @@ def discrete_log(a, base, ord=None, bounds=None, operation='*', identity=None, i
c = discrete_log_rho(h, gamma, ord=pi, inverse=inverse, identity=identity, op=op, operation=operation)
elif algorithm == 'lambda':
c = discrete_log_lambda(h, gamma, (0, temp_bound), inverse=inverse, identity=identity, op=op, operation=operation)
else:
raise ValueError(f"unknown algorithm {algorithm}")
l[i] += c * (pi**j)
running_bound //= pi
running_mod *= pi
Expand Down Expand Up @@ -1100,14 +1109,14 @@ def discrete_log_lambda(a, base, bounds, operation='*', identity=None, inverse=N
c += r
if mut:
H.set_immutable()
mem = {H}
mem = H
# second random walk
H = a
d = 0
while c - d >= lb:
if mut:
H.set_immutable()
if ub >= c - d and H in mem:
if ub >= c - d and H == mem:
return c - d
r, e = M[hash_function(H) % k]
H = mult(H, e)
Expand Down
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