Common Pitfalls

A result never updates

The structure is recreated every bar

Without var, a Memo, Watch or any other structure is created again on every bar, empty, and forgets everything it saw. A Memo created that way misses on every bar; a structure that needs history never builds one.

// Wrong: a new, empty Memo on every bar.
op.FloatMemo model = op.floatMemo()

// Right: one Memo for the whole run.
var op.FloatMemo model = op.floatMemo()

A dependency is missing

A Memo reruns only when something it watches changes. If the calculation reads a value that is not passed to staleOn() or the explicit pass, a change in that value never invalidates the cache. Pass every input the result depends on, including settings.

DirtySet marks are ignored

op.dirtySet() without a size has an empty universe, and marks outside the universe are silently ignored. Create it with the largest index you will mark plus one, such as op.dirtySet(maxZones), or pass a size to begin().

A CadenceGate never opens

The tick must keep growing. bar_index works; a value that repeats or resets does not. With dueWhenChanged(), the revision must also change, so check that the producer bumps it.

The cache never hits

• Raw inputs. Prices and indicator values change on nearly every bar. Round them to the precision the result responds to before passing them in. See regimes.
• One Watch, several sources. changed() keeps one baseline. Calling it with two different sources on the same Watch makes each call compare against the other source, so it always reports a change. Give each source its own Watch, or use an explicit begin() and finish() pass.
• An array with na under alwaysChanged. With NaCollectionPolicy.alwaysChanged, any na element reports a change on every pass. That is its purpose; switch to exact if na is an ordinary value.
• The dependency order varies. An explicit pass compares dependencies by position. Add them in the same order on every pass.

Indicator values are wrong

ta.* functions keep their own history. Inside a Memo or Watch guard, a CadenceGate block, or any condition that is false on some bars, they skip those bars and return different values. Pine Script v6 also evaluates and and or lazily, so a call on the right of and can be skipped as well.

// Wrong: ta.atr() only runs on the bars where the cache misses.
if model.staleOn(trendRegime)
    model.store(fit(trendRegime, ta.atr(14)))

// Right: ta.atr() runs on every bar, and its rounded value is a dependency.
float atr14 = ta.atr(14)
float atrRegime = math.round(atr14 / close * 400.0) / 4.0

if model.staleOn(trendRegime, atrRegime)
    model.store(fit(trendRegime, atrRegime))

A slot shows old data

Releasing a StablePool key, or retiring a SlotCache key, frees the slot without erasing your payload arrays. When acquire() returns created as true, the slot may hold the previous occupant's values. Write every field before reading any, or reset the payloads of the slots finish() returns. See StablePool & SlotCache.

The same applies to a released slot's key: keyAt() keeps reporting the last key until the slot is reused, so use contains(key) to test whether an object is still live.

An array changed by itself

Calls such as values(), slots(), valuesView(), keysView(), rowView() and rawView() return the structure's own storage, not a copy. It changes with the structure, and it is only valid until the next call that modifies it.

• Read a view right away; do not keep it in a var across bars.
• Never sort, push to or clear a view. A StablePool or DirtySet keeps positions that describe its list, and changing the list breaks both.
• When you need to keep or reorder the data, use the *Copy() call or a call that fills an output array.
• Passing a view back into the same structure, such as a store's valuesView() into its own build(), raises an aliasing error. Copy it first.

Core Concepts lists what every accessor returns.

Runtime errors

Every OptiPine error starts with the structure that raised it. N stands for a number in the message.