This book provides a superb introduction to and overview of the MIT PI
System for custom VLSI placement and routing. Alan Sher- man has done an
excellent job of collecting and clearly presenting material that was
previously available only in various theses, confer- ence papers, and
memoranda. He has provided here a balanced and comprehensive
presentation of the key ideas and techniques used in PI, discussing part
of his own Ph. D. work (primarily on the place- ment problem) in the
context of the overall design of PI and the contributions of the many
other PI team members. I began the PI Project in 1981 after learning
first-hand how dif- ficult it is to manually place modules and route
interconnections in a custom VLSI chip. In 1980 Adi Shamir, Leonard
Adleman, and I designed a custom VLSI chip for performing RSA encryp-
tion/decryption [226]. I became fascinated with the combinatorial and
algorithmic questions arising in placement and routing, and be- gan
active research in these areas. The PI Project was started in the belief
that many of the most interesting research issues would arise during an
actual implementation effort, and secondarily in the hope that a
practically useful tool might result. The belief was well-founded, but I
had underestimated the difficulty of building a large easily-used
software tool for a complex domain; the PI soft- ware should be
considered as a prototype implementation validating the design choices
made.