Shachar Itzhaky - CS-Lecture -
Thursday, 24.11.2016, 10:30
Everyone wants to program with "high-level concepts", rather than meddle
with the fine details of the implementation, such as pointers, network
packets, and asynchronous callbacks. This is usually achieved by introducing
layers of abstraction - but every layer incurs some overhead, and when
they accumulate, this overhand becomes significant and sometimes prohibitive.
Optimizing the program often requires to break abstractions, which leads
to suboptimal design, higher maintenance costs, and subtle hard-to-trace
I will present two recent projects that attempt to address this
difficulty. STNG is an automated lifting compiler that can synthesize
high-level graphics code for computing stencils over matrices, from
low-level legacy code written in Fortran. Its output is expressed in
Halide, a domain-specific language for image processing that can take
advantage of modern GPUs. The result is therefore code that is both
easier to understand and more efficient than the original code.
Bellmania is a specialized tool for accelerating dynamic-programming
algorithms by generating recursive divide-and-conquer implementations of
them. Recursive divide-and-conquer is an algorithmic technique that was
developed to obtain better memory locality properties. Bellmania
includes a high-level language for specifying dynamic programming
algorithms and a calculus that facilitates gradual transformation of
these specifications into efficient implementations. These
transformations formalize the divide-and-conquer technique; a
visualization interface helps users to interactively guide the process,
while an SMT-based back-end verifies each step and takes care of
low-level reasoning required for parallelism.
The lesson is that synthesis techniques are becoming mature enough to
play a role in the design and implementation of realistic software
systems, by combining the elegance of abstractions with the performance
gained by optimizing and tuning the fine details.
I am a post-doc at MIT's Computer Science lab, working in the
Computer-Aided Programming group headed by Prof. Armando Solar-Lezama.
I have an M.Sc. and a Ph.D. from Tel Aviv University, done under the
supervision of Prof. Mooly Sagiv. Prior to that I was a proud
alum of the Open University.