I used `amount_msat_eq(x, AMOUNT_MSAT(0))` because I forgot this
function existed. I probably missed it because the name is surprising,
so add "is" in there to make it clear it's a boolean function.
You'll note almost all the places which did use it are Eduardo's and
Lisa's code, so maybe it's just me.
Fix up a few places which I could use it, too.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
- add more checks
- add more error messages
- compute probabilities without fees during MCF
- compute probabilities with fees during get_routes
Signed-off-by: Lagrang3 <lagrang3@protonmail.com>
The probability for a success forward of x amount on a channel is now
computed as:
P_success(x) = b * P_rene(x)
where P_rene(x) is the probability distribution proposed by Rene
Pickhardt with a uniform distribution on the known liquidity of the
channel and 'b' is a new parameter we add in this PR, by the name of
"base probability". The "base probability" represents the probability
for a channel in the network choosen at random to be able to forward at
least 1msat, ie. of being alive, non-depleted and with at least one HTLC
slot. We don't know the value of 'b', but for the moment we assume that
it is 0.98 and use that as default.
As a consequence the probability cost becomes non-linear and non-convex
because of the additional constant term:
Cost(x) = - log P_success(x)
= - log b - - log P_rene(x)
= - log b + Cost_rene(x)
We currently don't handle well base fees and neither this additional
"base probability" but we can as a first approximation linearize the
cost function in this way:
Cost_linear(x) = (- log b)*x + Cost_rene_linear(x)
Changelog-Added: renepay: Add a dev parameter to renepay that represents
a constant probability of availability for all channels in the network.
Signed-off-by: Lagrang3 <lagrang3@protonmail.com>
This has the benefit of being shorter, as well as more reliable (you
will get a link error if we can't print it, not a runtime one!).
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Min. Cost Flow does not take into account fees when computing a flow
with liquidity constraints.
This is a work-around solution that reduces the amount on every route to
respect the liquidity bound. The deficity in the delivered amount is
solved by running MCF once again.
Changes:
1. the function `flow_complete` allocates amounts to send over the set of routes
computed by the MCF algorithm, but it does not allocate more than liquidity
bound of the route. For this reason `minflow` returns a set of routes that
satisfy the liquidity bounds but it is not guaranteed that the total payment
reaches the destination therefore there could a deficit in the delivery:
`deficit = amount_to_deliver - delivering`.
2. in the function `add_payflows` after `minflow` returns a set of routes we
call `flows_fit_amount` that tries to a allocate the `deficit` in the routes
that the MCF have computed.
3. if the resulting flows pass all payment constraints then we update
`amount_to_deliver = amount_to_deliver - delivering`, and the loop
repeats as long as `amount_to_deliver` is not zero.
In other words, the excess amount, beyond the liquidity bound,
in the routes is removed and then we try to allocate it
into known routes, otherwise we do a whole MCF again just for the
remaining amount.
Fixes issue #6599
Eduardo is on holiday right now, but he pinged me asking for this. It
makes some sense, and using half the *failed value* covers the case where
it's less than half what we expected.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
It now looks like (for test_hardmpp):
```
# we have computed a set of 1 flows with probability 0.328, fees 0msat and delay 23
# Flow 1: amount=1800000000msat prob=0.328 fees=0msat delay=12 path=-103x2x0/1(min=max=4294967295msat)->-103x5x0/0->-103x3x0/1->
# Flow 1: Failed at node #1 (WIRE_TEMPORARY_CHANNEL_FAILURE): failed: WIRE_TEMPORARY_CHANNEL_FAILURE (reply from remote)
# Flow 1: Failure of 1800000000msat for 103x5x0/0 capacity [0msat,3000000000msat] -> [0msat,1799999999msat]
# we have computed a set of 2 flows with probability 0.115, fees 0msat and delay 23
# Flow 2: amount=500000000msat prob=0.475 fees=0msat delay=12 path=-103x6x0/0(min=max=4294967295msat)->-103x1x0/1->-103x4x0/1->
# Flow 3: amount=1300000000msat prob=0.242 fees=0msat delay=12 path=-103x2x0/1(min=max=4294967295msat)->-103x5x0/0(max=1799999999msat)->-103x3x0/1->
# Flow 3: Failed at node #1 (WIRE_TEMPORARY_CHANNEL_FAILURE): failed: WIRE_TEMPORARY_CHANNEL_FAILURE (reply from remote)
# Flow 3: Failure of 1300000000msat for 103x5x0/0 capacity [0msat,1799999999msat] -> [0msat,1299999999msat]
# we have computed a set of 2 flows with probability 0.084, fees 0msat and delay 23
# Flow 4: amount=260000000msat prob=0.467 fees=0msat delay=12 path=-103x6x0/0(500000000msat in 1 htlcs,min=max=4294967295msat)->-103x1x0/1(500000000msat in 1 htlcs)->-103x4x0/1(500000000msat in 1 htlcs)->
# Flow 5: amount=1040000000msat prob=0.179 fees=0msat delay=12 path=-103x2x0/1(min=max=4294967295msat)->-103x5x0/0(max=1299999999msat)->-103x3x0/1->
# Flow 5: Failed at node #1 (WIRE_TEMPORARY_CHANNEL_FAILURE): failed: WIRE_TEMPORARY_CHANNEL_FAILURE (reply from remote)
# Flow 5: Failure of 1040000000msat for 103x5x0/0 capacity [0msat,1299999999msat] -> [0msat,1039999999msat]
# we have computed a set of 2 flows with probability 0.052, fees 0msat and delay 23
# Flow 6: amount=120000000msat prob=0.494 fees=0msat delay=12 path=-103x6x0/0(760000000msat in 2 htlcs,min=max=4294967295msat)->-103x1x0/1(760000000msat in 2 htlcs)->-103x4x0/1(760000000msat in 2 htlcs)->
# Flow 7: amount=920000000msat prob=0.105 fees=0msat delay=12 path=-103x2x0/1(min=max=4294967295msat)->-103x5x0/0(max=1039999999msat)->-103x3x0/1->
# Flow 7: Success
```
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
I am doing to add more more debugging, but sent here is 0.
Document that clearly, and put a real value in sent.
Also: since we already sub 1 msat from x, amount_msat_less_eq should
be amount_msat_less (it may be equal to our min, in theory).
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
There's a fascinating bug report which suggests this happens on local channels,
implying spendable_msat is wrong?
See-also: #6567
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
- adopt "const <type> *"convention
- remove use_shadow option for some pyln tests
- show prob. information of flows into paynotes
- show prob. of success of entire payment flow in paynotes
- minflow: We were not releasing the memory of flow arrays when replacing
them with a new canditate.
- use memleak_scan_obj in memleak_check
- replace u64 with size_t
Signed-off-by: Lagrang3 <eduardo.quintana@pm.me>
