Incrementally update flattend OHLC data

After much effort (and exhaustion) but failure to get a view into
our `numpy` OHLC struct-array, this instead allocates an in-thread-memory
array which is updated with flattened data every flow update cycle.

I need to report what I think is a bug to `numpy` core about the whole
view thing not working but, more or less this gets the same behaviour
and minimizes work to flatten the sampled data for line-graphics
drawing thus improving refresh latency when drawing large downsampled
curves.

TL;DR:
- add `ShmArray.ustruct()` to return a **copy of** (since a view doesn't
  work..) the (field filtered) shm array which is the same index-length
  as the source data.
- update the OHLC ds curve with view aware data sliced out from the
  pre-allocated and incrementally updated data (we had to add a last
  index var `._iflat` to track appends - this should be moved into
  a renderer eventually?).

piker/data/_sharedmem.py

@@ -22,7 +22,6 @@ from __future__ import annotations
 from sys import byteorder
 from typing import Optional
 from multiprocessing.shared_memory import SharedMemory, _USE_POSIX
-from multiprocessing import resource_tracker as mantracker
 
 if _USE_POSIX:
     from _posixshmem import shm_unlink
@@ -30,6 +29,7 @@ if _USE_POSIX:
 import tractor
 import numpy as np
 from pydantic import BaseModel
+from numpy.lib import recfunctions as rfn
 
 from ..log import get_logger
 from ._source import base_iohlc_dtype
@@ -46,6 +46,10 @@ _default_size = 10 * _secs_in_day
 _rt_buffer_start = int(9*_secs_in_day)
 
 
+def cuckoff_mantracker():
+
+    from multiprocessing import resource_tracker as mantracker
+
     # Tell the "resource tracker" thing to fuck off.
     class ManTracker(mantracker.ResourceTracker):
         def register(self, name, rtype):
@@ -68,6 +72,9 @@ mantracker.unregister = mantracker._resource_tracker.unregister
     mantracker.getfd = mantracker._resource_tracker.getfd
 
 
+cuckoff_mantracker()
+
+
 class SharedInt:
     """Wrapper around a single entry shared memory array which
     holds an ``int`` value used as an index counter.
@@ -191,7 +198,11 @@ class ShmArray:
         self._post_init: bool = False
 
         # pushing data does not write the index (aka primary key)
+        dtype = shmarr.dtype
+        if dtype.fields:
             self._write_fields = list(shmarr.dtype.fields.keys())[1:]
+        else:
+            self._write_fields = None
 
     # TODO: ringbuf api?
 
@@ -237,6 +248,48 @@ class ShmArray:
 
         return a
 
+    def ustruct(
+        self,
+        fields: Optional[list[str]] = None,
+
+        # type that all field values will be cast to
+        # in the returned view.
+        common_dtype: np.dtype = np.float,
+
+    ) -> np.ndarray:
+
+        array = self._array
+
+        if fields:
+            selection = array[fields]
+            fcount = len(fields)
+        else:
+            selection = array
+            fcount = len(array.dtype.fields)
+
+        # XXX: manual ``.view()`` attempt that also doesn't work.
+        # uview = selection.view(
+        #     dtype='<f16',
+        # ).reshape(-1, 4, order='A')
+
+        # assert len(selection) == len(uview)
+
+        u = rfn.structured_to_unstructured(
+            selection,
+            # dtype=float,
+            copy=True,
+        )
+
+        # unstruct = np.ndarray(u.shape, dtype=a.dtype, buffer=shm.buf)
+        # array[:] = a[:]
+        return u
+        # return ShmArray(
+        #     shmarr=u,
+        #     first=self._first,
+        #     last=self._last,
+        #     shm=self._shm
+        # )
+
     def last(
         self,
         length: int = 1,
@@ -386,7 +439,11 @@ def open_shm_array(
         create=True,
         size=a.nbytes
     )
-    array = np.ndarray(a.shape, dtype=a.dtype, buffer=shm.buf)
+    array = np.ndarray(
+        a.shape,
+        dtype=a.dtype,
+        buffer=shm.buf
+    )
     array[:] = a[:]
     array.setflags(write=int(not readonly))
 

piker/ui/_flows.py

@@ -24,7 +24,6 @@ incremental update.
 '''
 from __future__ import annotations
 from functools import partial
-import time
 from typing import (
     Optional,
     Callable,
@@ -38,7 +37,7 @@ from PyQt5.QtGui import QPainterPath
 
 from ..data._sharedmem import (
     ShmArray,
-    # attach_shm_array
+    open_shm_array,
 )
 from .._profile import pg_profile_enabled, ms_slower_then
 from ._ohlc import (
@@ -152,6 +151,7 @@ class Flow(msgspec.Struct):  # , frozen=True):
     render: bool = True  # toggle for display loop
     flat: Optional[ShmArray] = None
     x_basis: Optional[np.ndarray] = None
+    _iflat: int = 0
 
     _last_uppx: float = 0
     _in_ds: bool = False
@@ -344,6 +344,7 @@ class Flow(msgspec.Struct):  # , frozen=True):
         graphics = self.graphics
         if isinstance(graphics, BarItems):
 
+            fields = ['open', 'high', 'low', 'close']
             # if no source data renderer exists create one.
             r = self._src_r
             if not r:
@@ -357,17 +358,37 @@ class Flow(msgspec.Struct):  # , frozen=True):
 
                 # create a flattened view onto the OHLC array
                 # which can be read as a line-style format
-                # shm = self.shm
+                shm = self.shm
-                # self.flat = shm.unstruct_view(['open', 'high', 'low', 'close'])
+
+                # flat = self.flat = self.shm.unstruct_view(fields)
+                self.flat = self.shm.ustruct(fields)
+                self._iflat = self.shm._last.value
+
                 # import pdbpp
                 # pdbpp.set_trace()
-                # x = self.x_basis = (
+                # assert len(flat._array) == len(self.shm._array[fields])
-                #     np.broadcast_to(
+
-                #         shm._array['index'][:, None],
+                x = self.x_basis = (
-                #         # self.flat._array.shape,
+                    np.broadcast_to(
-                #         self.flat.shape,
+                        shm._array['index'][:, None],
-                #     ) + np.array([-0.5, 0, 0, 0.5])
+                        (
+                            shm._array.size,
+                            # 4,  # only ohlc
+                            self.flat.shape[1],
+                        ),
+                    ) + np.array([-0.5, 0, 0, 0.5])
+                )
+
+                # fshm = self.flat = open_shm_array(
+                #     f'{self.name}_flat',
+                #     dtype=flattened.dtype,
+                #     size=flattened.size,
                 # )
+                # fshm.push(flattened)
+
+                # print(f'unstruct diff: {time.time() - start}')
+                # profiler('read unstr view bars to line')
+                # start = self.flat._first.value
 
                 ds_curve_r = Renderer(
                     flow=self,
@@ -407,7 +428,7 @@ class Flow(msgspec.Struct):  # , frozen=True):
             # - if we're **not** downsampling then we simply want to
             #   render the bars graphics curve and update..
             # - if insteam we are in a downsamplig state then we to
-            x_gt = 8
+            x_gt = 6
             uppx = curve.x_uppx()
             in_line = should_line = curve.isVisible()
             if (
@@ -426,37 +447,43 @@ class Flow(msgspec.Struct):  # , frozen=True):
 
             # do graphics updates
             if should_line:
-                # start = time.time()
-                # y = self.shm.unstruct_view(
-                #     ['open', 'high', 'low', 'close'],
-                # )
-                # print(f'unstruct diff: {time.time() - start}')
-                # profiler('read unstr view bars to line')
-                # # start = self.flat._first.value
 
-                # x = self.x_basis[:y.size].flatten()
+                # update flatted ohlc copy
-                # y = y.flatten()
+                iflat, ishm = self._iflat, self.shm._last.value
-                # profiler('flattening bars to line')
+                to_update = rfn.structured_to_unstructured(
-                # path, last = dsc_r.render(read)
+                    self.shm._array[iflat:ishm][fields]
-                # x, flat = ohlc_flat_view(
+                )
-                #     ohlc_shm=self.shm,
-                #     x_basis=x_basis,
-                # )
-                # y = y.flatten()
-                # y_iv = y[ivl:ivr].flatten()
-                # x_iv = x[ivl:ivr].flatten()
-                # assert y.size == x.size
 
-                x, y = self.flat = ohlc_flatten(array)
+                # print(to_update)
-                x_iv, y_iv = ohlc_flatten(in_view)
+                self.flat[iflat:ishm][:] = to_update
-                profiler('flattened OHLC data')
+                profiler('updated ustruct OHLC data')
+
+                y_flat = self.flat[:ishm]
+                x_flat = self.x_basis[:ishm]
+
+                self._iflat = ishm
+
+                y = y_flat.reshape(-1)
+                x = x_flat.reshape(-1)
+                profiler('flattened ustruct OHLC data')
+
+                y_iv_flat = y_flat[ivl:ivr]
+                x_iv_flat = x_flat[ivl:ivr]
+
+                y_iv = y_iv_flat.reshape(-1)
+                x_iv = x_iv_flat.reshape(-1)
+                profiler('flattened ustruct in-view OHLC data')
+
+                # x, y = ohlc_flatten(array)
+                # x_iv, y_iv = ohlc_flatten(in_view)
+                # profiler('flattened OHLC data')
 
                 curve.update_from_array(
                     x,
                     y,
                     x_iv=x_iv,
                     y_iv=y_iv,
-                    view_range=None,  # hack
+                    view_range=(ivl, ivr),  # hack
                     profiler=profiler,
                 )
                 profiler('updated ds curve')
@@ -477,7 +504,7 @@ class Flow(msgspec.Struct):  # , frozen=True):
                 # graphics.setCacheMode(QtWidgets.QGraphicsItem.NoCache)
                 # graphics.setCacheMode(QtWidgets.QGraphicsItem.DeviceCoordinateCache)
 
-                graphics.prepareGeometryChange()
+                # graphics.prepareGeometryChange()
                 graphics.update()
 
             if (
@@ -632,7 +659,7 @@ class Renderer(msgspec.Struct):
 
         '''
         # do full source data render to path
-        last_read = (
+        (
             xfirst, xlast, array,
             ivl, ivr, in_view,
         ) = self.last_read