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Transcript
An active processing virtual filesystem for
manipulating massive electron microscopy
datasets required for connectomics research
Art Wetzel - Pittsburgh Supercomputing Center
National Resource for Biomedical Supercomputing
awetzel@psc.edu 412-268-3912
www.psc.edu and www.nrbsc.org
Source data from …
R. Clay Reid, Jeff Lichtman, Wei-Chung Allen Lee
Harvard Medical School, Allen Institute for Brain Science
Center for Brain Science, Harvard University
Davi Bock
HMMI Janelia Farm
David Hall and Scott Emmons
Albert Einstein College of Medicine
Aug 30, 2012 Comp Sci Connectomics Data Project Overview
1
What is Connectomics?
“an emerging field defined by high-throughput
generation of data about neural connectivity, and
subsequent mining of that data for knowledge about the
brain. A connectome is a summary of the structure of a
neural network, an annotated list of all synaptic
connections between the neurons inside a brain or brain
region.”
DTI “tractography” Human
Connectome Project at
MRI 2 mm resolution
~10 MB/volume
1.3x106 mm3
“Brainbow” stained
neuropil at 300 nm optical
resolution
~10 GB/mm3
Serial section electron
microscopy reconstruction
at 3-4 nm resolution
~1 PB/mm3
2
An infant human brain contains
~80 billion neurons. A typical
human cortical neuron makes
more than 10,000 connections
Smaller brains with
~500,000 neurons
3
How big (small) is a nanometer?
Below ~10 nm its not anatomy but lots of rapidly moving molecular detail
4
Reconstructing brain circuits requires
high resolution electron microscopy
over “long” distances == BIGDATA
Vesicles ~30 nm diam.
A synaptic junction
>500 nm wide with
cleft gap ~20 nm
Dendritic spine
Dendrite
www.coolschool.ca/lor/BI12/unit12/U12L04.htm
Recent ICs have 32nm features
22nm chips are being delivered.
Gate oxide 1.2nm thick
5
A10 Tvoxel dataset
aligned by our group
was an essential part of
the March 2011 Nature
paper with Davi Bock,
Clay Reid and Harvard
colleagues
Now we are working on
two datasets of 100TB
each and expect to
reach PBs in 2-3 years.
6
Current data from a 400 micron
cube is greater than 100 TBs (.1 PB)
A full mouse brain would be an exabyte == 1000 PB
7
The CS project is to test a virtual filesystem
concept to address common problems with
connectomics and other massive datasets.




The most important aim is reducing unwanted data
duplication as raw data are preprocessed for final
analysis. The virtual filesystem addresses this by
replacing redundant storage by on-the-fly computing.
The second aim is to provide a convenient framework for
efficient on-the-fly computation on multidimensional
datasets within high performance parallel computing
environments using both CPU and GPGPU processing.
We are also interested in the image warping and other
processes required for neural circuit reconstruction.
The Filesystem in User Space mechanism (FUSE)
provides a convenient implementation basis that can work
on a variety of systems. There are many existing FUSE
codes that serve as useful examples. (i.e. scriptfs) 8
One very useful transform is
on-the-fly image warping…
This example from http://davis.wpi.edu/~matt/courses/morph/2d.htm
9
Conventional: process input to make
intermediate files for later processes
Active VVFS approach: processing is done
on demand as required to present virtual
file contents to later processes… Unix pipes
provide a restricted subset of this capability
10
We would eventually like to have a flexible
software framework to allow a combination of
common prewritten and user written application
codes to operate together and take advantage of
parallel CPU and GPGPU technologies.
11
Multidimensional data structures to provide efficient random
and sequential access analogous to the 1D representations
provided by standard filesystems will be part of this work.
Students will have access to PSC linux machines which access our datasets
along with the compilers and other tools required. Basic end-to-end
functionality with simple transforms can likely be achieved and may be
extended as time permits. Ideally students would have good C/C++, data
structures, graphics and OS skills. (biology not required but could be useful)
12