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swarm/pot: pot.remove fixed #1098

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swarm/pot: pot.remove fixed #1098

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357d536
swarm/pot: refactored pot.remove(), updated comments
gluk256 Jan 8, 2019
dbfd8ec
swarm/pot: comments updated
gluk256 Jan 9, 2019
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4 changes: 3 additions & 1 deletion swarm/pot/address.go
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Original file line number Diff line number Diff line change
Expand Up @@ -162,7 +162,6 @@ func ToBytes(v Val) []byte {
}

// DefaultPof returns a proximity order comparison operator function
// where all
func DefaultPof(max int) func(one, other Val, pos int) (int, bool) {
return func(one, other Val, pos int) (int, bool) {
po, eq := proximityOrder(ToBytes(one), ToBytes(other), pos)
Expand All @@ -174,6 +173,9 @@ func DefaultPof(max int) func(one, other Val, pos int) (int, bool) {
}
}

// proximityOrder returns two parameters:
// 1. relative proximity order of the arguments one & other;
// 2. boolean indicating whether the full match occurred (one == other).
func proximityOrder(one, other []byte, pos int) (int, bool) {
for i := pos / 8; i < len(one); i++ {
if one[i] == other[i] {
Expand Down
18 changes: 6 additions & 12 deletions swarm/pot/pot.go
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Expand Up @@ -144,13 +144,10 @@ func add(t *Pot, val Val, pof Pof) (*Pot, int, bool) {
return r, po, found
}

// Remove called on (v) deletes v from the Pot and returns
// the proximity order of v and a boolean value indicating
// if the value was found
// Remove called on (t, v) returns a new Pot that contains all the elements of t
// minus the value v, using the applicative remove
// the second return value is the proximity order of the inserted element
// the third is boolean indicating if the item was found
// Remove deletes element v from the Pot t and returns three parameters:
// 1. new Pot that contains all the elements of t minus the element v;
// 2. proximity order of the removed element v;
// 3. boolean indicating whether the item was found.
func Remove(t *Pot, v Val, pof Pof) (*Pot, int, bool) {
return remove(t, v, pof)
}
Expand All @@ -161,10 +158,7 @@ func remove(t *Pot, val Val, pof Pof) (r *Pot, po int, found bool) {
if found {
size--
if size == 0 {
r = &Pot{
po: t.po,
}
return r, po, true
return &Pot{}, po, true
}
i := len(t.bins) - 1
last := t.bins[i]
Expand Down Expand Up @@ -201,7 +195,7 @@ func remove(t *Pot, val Val, pof Pof) (r *Pot, po int, found bool) {
}
bins = append(bins, t.bins[j:]...)
r = &Pot{
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why not return the same pot if not found?

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because the function is recursive, so if not found at the current level of pot tree, it might be be found deeper.

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But if not found the contents of the newly created Pot object is identical to the one passed, no? Is the intention that the Pot object that is passed to this (and similar) functions is discarded (only use the returned Pot)?

pin: val,
pin: t.pin,
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wow!

size: size,
po: t.po,
bins: bins,
Expand Down
84 changes: 77 additions & 7 deletions swarm/pot/pot_test.go
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Expand Up @@ -82,6 +82,72 @@ func testAdd(t *Pot, pof Pof, j int, values ...string) (_ *Pot, n int, f bool) {
return t, n, f
}

// removing non-existing element from pot
func TestPotRemoveNonExisting(t *testing.T) {
pof := DefaultPof(8)
n := NewPot(newTestAddr("00111100", 0), 0)
n, _, _ = Remove(n, newTestAddr("00000101", 0), pof)
exp := "00111100"
got := Label(n.Pin())
if got[:8] != exp {
t.Fatalf("incorrect pinned value. Expected %v, got %v", exp, got[:8])
}
}

// this test creates hierarchical pot tree, and therefore any child node will have
// child_po = parent_po + 1.
// then removes a node from the middle of the tree.
func TestPotRemoveSameBin(t *testing.T) {
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Please explain what the tests are doing in a comment

pof := DefaultPof(8)
n := NewPot(newTestAddr("11111111", 0), 0)
n, _, _ = testAdd(n, pof, 1, "00000000", "01000000", "01100000", "01110000", "01111000")
n, _, _ = Remove(n, newTestAddr("01110000", 0), pof)
inds, po := indexes(n)
goti := n.Size()
expi := 5
if goti != expi {
t.Fatalf("incorrect number of elements in Pot. Expected %v, got %v", expi, goti)
}
inds, po = indexes(n)
got := fmt.Sprintf("%v", inds)
exp := "[5 3 2 1 0]"
if got != exp {
t.Fatalf("incorrect indexes in iteration over Pot. Expected %v, got %v", exp, got)
}
got = fmt.Sprintf("%v", po)
exp = "[3 2 1 0 0]"
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I don't understand why these po's are correct.

If the pin has its highest-order bit set to 1, shouldn't any address with highest-order bit 0 mean po == 0?

Following the logic of this expectation, shouldn't it be rather [5 3 2 0]?

Why are there 5 elements after deleting one? Does that mean we count the pin aswell? If so, what does the po actually mean here? Is it po in relation to the pin? And if it is, why isn't there a po == 256 first, which would be the pin address compared to itself?

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po is calculated in relation to the parent node in the pot

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Your answer doesn't clear up my questions, I'm afraid.

What is "parent node." Is it the same as the pin?

if got != exp {
t.Fatalf("incorrect po-s in iteration over Pot. Expected %v, got %v", exp, got)
}
}

// this test creates a flat pot tree (all the elements are leafs of one root),
// and therefore they all have the same po.
// then removes an arbitrary element from the pot.
func TestPotRemoveDifferentBins(t *testing.T) {
pof := DefaultPof(8)
n := NewPot(newTestAddr("11111111", 0), 0)
n, _, _ = testAdd(n, pof, 1, "00000000", "10000000", "11000000", "11100000", "11110000")
n, _, _ = Remove(n, newTestAddr("11100000", 0), pof)
inds, po := indexes(n)
goti := n.Size()
expi := 5
if goti != expi {
t.Fatalf("incorrect number of elements in Pot. Expected %v, got %v", expi, goti)
}
inds, po = indexes(n)
got := fmt.Sprintf("%v", inds)
exp := "[1 2 3 5 0]"
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Why is the 0 last?

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this is how this test function indexes() works. otherwise it's irrelevant.

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Can you elaborate, please? Are you saying that the order doesn't matter? Why doesn't the order matter?

if got != exp {
t.Fatalf("incorrect indexes in iteration over Pot. Expected %v, got %v", exp, got)
}
got = fmt.Sprintf("%v", po)
exp = "[0 1 2 4 0]"
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What does the last 0 represent here?

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the root

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@nolash nolash Jan 10, 2019 •
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So we have "root," "parent node," and "pin." Are they the same thing? Please let's use one term.

Grep'ing the files doesn't really clear up the terms either:

$ grep -i "parent" swarm/pot/ -r
swarm/pot/pot_test.go:// child_po = parent_po + 1.
$ grep -i "root" swarm/pot/ -r
swarm/pot/pot_test.go:// 	log.Root().SetHandler(log.LvlFilterHandler(log.LvlTrace, log.StreamHandler(os.Stderr, log.TerminalFormat(false))))
swarm/pot/pot_test.go:// this test creates a flat pot tree (all the elements are leafs of one root),
swarm/pot/pot.go:// Pot is the node type (same for root, branching node and leaf)
swarm/pot/pot.go:// the function argument is passed the value and the proximity order wrt the root pin
swarm/pot/pot.go:// it does NOT include the pinned item of the root

"root pin" .. "pinned item of root" ...

if got != exp {
t.Fatalf("incorrect po-s in iteration over Pot. Expected %v, got %v", exp, got)
}
}

func TestPotAdd(t *testing.T) {
pof := DefaultPof(8)
n := NewPot(newTestAddr("00111100", 0), 0)
Expand Down Expand Up @@ -135,25 +201,29 @@ func TestPotRemove(t *testing.T) {
t.Fatalf("incorrect number of elements in Pot. Expected %v, got %v", expi, goti)
}
inds, po := indexes(n)
got = fmt.Sprintf("%v", po)
exp = "[1 3 0]"
if got != exp {
t.Fatalf("incorrect po-s in iteration over Pot. Expected %v, got %v", exp, got)
}
got = fmt.Sprintf("%v", inds)
exp = "[2 4 0]"
exp = "[2 4 1]"
if got != exp {
t.Fatalf("incorrect indexes in iteration over Pot. Expected %v, got %v", exp, got)
}
got = fmt.Sprintf("%v", po)
exp = "[1 3 0]"
n, _, _ = Remove(n, newTestAddr("00111100", 0), pof) // remove again same element
inds, _ = indexes(n)
got = fmt.Sprintf("%v", inds)
if got != exp {
t.Fatalf("incorrect po-s in iteration over Pot. Expected %v, got %v", exp, got)
t.Fatalf("incorrect indexes in iteration over Pot. Expected %v, got %v", exp, got)
}
// remove again
n, _, _ = Remove(n, newTestAddr("00111100", 0), pof)
n, _, _ = Remove(n, newTestAddr("00000000", 0), pof) // remove the first element
inds, _ = indexes(n)
got = fmt.Sprintf("%v", inds)
exp = "[2 4]"
if got != exp {
t.Fatalf("incorrect indexes in iteration over Pot. Expected %v, got %v", exp, got)
}

}

func TestPotSwap(t *testing.T) {
Expand Down