automatic chunk size

anomaly-chunksize.ipynb

anomaly-chunksizesimplifyed.ipynb

auto_chunkstest.ipynb

automatic_chunksize.ipynb

{
 "cells": [
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [],
   "source": [
    "import dask.array as da\n",
    "import dask"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "dask.array<standard_normal, shape=(20834, 384, 320), dtype=float64, chunksize=(380, 192, 320)>"
      ]
     },
     "execution_count": 2,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "dask.config.set({\"array.chunk-size\": '370MB'})\n",
    "da.random.RandomState(0).standard_normal((20834, 384, 320), chunks='auto')  "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "186777600"
      ]
     },
     "execution_count": 3,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "380*192*320*8"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "When specifying chunk size as 370MB in dask, dask array creates chunksize 187MB."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "dask.array<standard_normal, shape=(20834, 384, 320), dtype=float64, chunksize=(386, 384, 320)>"
      ]
     },
     "execution_count": 4,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "dask.config.set({\"array.chunk-size\": '380MB'})\n",
    "da.random.RandomState(0).standard_normal((20834, 384, 320), chunks='auto')  "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "379453440"
      ]
     },
     "execution_count": 5,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "386*384*320*8"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "When specifying chunk size as 380MB in dask, dask array creates chunksize 380MB."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Is this a bug? or due to this specific array shape?  What can we do to have chunk_size as we desired with automatic chunking scheme?"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "dask.array<standard_normal, shape=(20834, 384, 320), dtype=float64, chunksize=(155, 128, 80)>"
      ]
     },
     "execution_count": 6,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "dask.config.set({\"array.chunk-size\": '30MB'})\n",
    "da.random.RandomState(0).standard_normal((20834, 384, 320), chunks='auto')  "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "12697600"
      ]
     },
     "execution_count": 7,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "155*128* 80*8"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "When specifying chunk size as 30MB, same problem as specifying 370MB, dask create only 13MB of chunk."
   ]
  }
 ],
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