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fix: Remove O(n²) list-building from compute_fov() (closes #146)

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compute_fov() was iterating through the entire grid to build a Python
list of visible cells, causing O(grid_size) performance instead of
O(radius²). On a 1000×1000 grid this was 15.76ms vs 0.48ms.

The fix returns None instead - users should use is_in_fov() to query
visibility, which is the pattern already used by existing code.

Performance: 33x speedup (15.76ms → 0.48ms on 1M cell grid)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>
This commit is contained in:
John McCardle 2025-11-28 21:26:32 -05:00
commit f769c6c5f5
3 changed files with 217 additions and 35 deletions
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39
src/UIGrid.cpp
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@ -1183,41 +1183,10 @@ PyObject* UIGrid::py_compute_fov(PyUIGridObject* self, PyObject* args, PyObject*
// Compute FOV
self->data->computeFOV(x, y, radius, light_walls, (TCOD_fov_algorithm_t)algorithm);
// Build list of visible cells as tuples (x, y, visible, discovered)
PyObject* result_list = PyList_New(0);
if (!result_list) return NULL;
// Iterate through grid and collect visible cells
for (int gy = 0; gy < self->data->grid_y; gy++) {
for (int gx = 0; gx < self->data->grid_x; gx++) {
if (self->data->isInFOV(gx, gy)) {
// Create tuple (x, y, visible, discovered)
PyObject* cell_tuple = PyTuple_New(4);
if (!cell_tuple) {
Py_DECREF(result_list);
return NULL;
}
PyTuple_SET_ITEM(cell_tuple, 0, PyLong_FromLong(gx));
PyTuple_SET_ITEM(cell_tuple, 1, PyLong_FromLong(gy));
PyTuple_SET_ITEM(cell_tuple, 2, Py_True); // visible
PyTuple_SET_ITEM(cell_tuple, 3, Py_True); // discovered
Py_INCREF(Py_True); // Need to increment ref count for True
Py_INCREF(Py_True);
// Append to list
if (PyList_Append(result_list, cell_tuple) < 0) {
Py_DECREF(cell_tuple);
Py_DECREF(result_list);
return NULL;
}
Py_DECREF(cell_tuple); // List now owns the reference
}
}
}
return result_list;
// Return None - use is_in_fov() to query visibility
// See issue #146: returning a list had O(grid_size) performance
Py_RETURN_NONE;
}
PyObject* UIGrid::py_is_in_fov(PyUIGridObject* self, PyObject* args)