NSF-1909099 Project Page

Prescriptive Software Caching Using Leases

The cost and performance of a modern system depend on its memory hierarchy. Manual management of the memory hierarchy is complex and not portable. Automatic management is sub-optimal — it reacts to program behavior but does not directly utilize program knowledge. This research seeks a middle ground with a new type of cache called Lease Cache. It enables prescriptive caching by utilizing proogram knowledge, variable cache sizes, and multi-policy caching.

Prescriptive caching takes a principled approach building on theory and optimization. It connects programming and caching directly with programming abstractions and program analysis. The research solves four problems. (1) Lease cache theory, ensuring performance no worse than LRU cache when there is no program knowledge and optimal when there is program knowledge. (2) Lease cache optimization, incuding statistical caching as well as optimization for multi-policy and multi-granularity caching. (3) Locality analysis, combining static analysis and run-time sampling to analyze program locality. (4) Lease cache system, with efficient lease management including the use of approximation to reduce the overhead.

 

Funding Sources

Acknowledgement. The on-going research is supported by the National Science Foundation (Contract No. CNS-1909099, CCF-1717877, CCF-1629376) and an IBM CAS Faculty Fellowship. The past support came from the National Science Foundation (Contract No. CNS-1319617, CCF-1116104, CCF-0963759, CNS-0834566, CNS-0720796, CNS-0509270, CCR-0238176, CCR-0219848 and EIA-0080124)the Department of Energy (Contract No. DE-FG02-02ER25525), the National Science Foundation of China (Contract No. 61328201), two grants from Microsoft Research, a grant from Huawei, and equipment support from Intel. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the funding organizations.

Rahman Presenting at Compiler Construction Conference

Rahman was distilling the concept of spatial locality.  Prior to optimizing spatial locality in large scale code, Firefox, Chrome, LLVM, Rahman also developed the newest theory on optimal spatial locality in his paper in POPL 2016.

Rahman Lavaee, John Criswell, Chen Ding:
Codestitcher: Inter-Procedural Basic Block Layout Optimization.  in 28th International Conference on Compiler Construction, February 2019, Washington DC, USA.

How to make our ideas clear

This text is sent to my advisees at the start of the spring 2019 semester.

In modern day with vast information at our fingertips and suggestions of content displaced every time we click or touch, it’s important to keep in mind that our mind can be overwhelmed and lose clarity. Yet the earliest lesson that students should demand a school to teach is, how to make our ideas clear.

For this, I here borrow the title of Charles Peirce’s 1878 article and some of his ideas about ideas, in his exact words.

“To know what we think, to be masters of our own meaning, will make a solid foundation for great and weighty thought. It is most easily learned by those whose ideas are meager and restricted; and far happier they than such a wallow helplessly in a rich mud of conceptions.”

“A few clear ideas are worth more than many confused ones. A young [person] would hardly be persuaded to sacrifice the greater part of [one’s] thoughts to save the rest; and the muddled head is the least apt to see the necessity of such a sacrifice. [It is] a person with a congenital defect. Time will help, but intellectual maturity with regard to clearness comes rather late, an unfortunate arrangement of Nature, inasmuch as clearness is of less use to a [person] settled in life … than it would be to one whose path lies [in front].”

“It is terrible to see how a single unclear idea, a single formula without meaning, lurking in a young man’s head, will sometimes act like an obstruction of inert matter in an artery, hindering the nutrition of the brain, and condemning its victim to pine away in the fullness of his intellectual vigor and in the midst of intellectual plenty.”

“Many a man has cherished for years as his hobby some vague shadow of an idea, too meaningless to be positively false; he has, nevertheless, passionately loved it, has made it his companion by day and by night, and has given to it his strength and his life, leaving all other occupations for its sake, and in short has lived with it and for it, until it has become, as it were, flesh of his flesh and bone of his bone; and then he has waked up some bright morning to find it gone, clean vanished away … and the essence of his life gone with it.”

Full text of the article is at http://www.peirce.org/writings/p119.html

CSC 253/453 Fall 2018

CSC 253/453 Fall 2018

Dynamic Language & Software Development

Prerequisites: CSC 252 and CSC 254 are required for CSC 453 and recommended for CSC 253. Familiarity with a dynamic programming language such as Python is required for CSC 253.
Crosslisted: TCS 453 (same requirement as CSC 253)

This course studies dynamically-typed programming languages and modular software development. Topics include principles and practice of modular design, functional and object-oriented programming techniques, software engineering concepts, software correctness and reliability, programming tools, and design examples. Ruby is used as the main instruction language. The lessons complement those in traditional compilers and programming languages courses, which focus mainly on statically-typed languages and individual algorithms rather than system design. A significant portion of the assignment is a group project.

Teaching Staff and office hours:  Prof. Chen Ding, Fridays 11am to 12pm in Wegmans Hall 3407, x51373.  Yu Feng, 5pm to 6pm, Mondays and Wednesdays, Wegmans Hall 3407.   Patrick Ferner, 2:30pm to 3:30pm, Tuesdays, Wegmans 2215 (updated 9/11).

Policies for grading, attendance, and academic honesty (updated 8/27)

Grading:

  • mid-term and final exams, 15% each
  • two written homeworks, 5% each
  • assignments and projects, 60%

Assignments are typically handed out on Wednesday and due the following Tuesday midnight.

Preparation (before first class):

“No Silver Bullet — Essence and Accidents of Software Engineering” is a classic paper on software engineering written by Turing Award winner Fred Brooks in 1986.  Read the paper (available here if accessed inside the UR network) pages 3 to 5 on the “essential difficulties” of software development and skim the rest of the paper.

“A former member of the SD10 Panel on Computing in Support of Battle Management explains why he believes the ‘star wars’ effort will not achieve its stated goals.”  Read the paper (available here if accessed inside the UR network) pages 2 to 4 the section titled “Why software is unreliable.”  Which of the “essential difficulties” was Parnas discussing?

More background of this debate, detailed rationales and an illuminating discussion of the ethical issues can be found in another article of Parnas: “SDI: A Violation of Professional Responsibility”.  The article does not seem to have a free version online, but you can read it by borrowing the book “Software Fundamentals” (included as Chapter 27) from the textbook reserve for CSC 253/453 at the Carlson Library.  The lease is two hours.

Further material will be distributed through the Blackboard web site  for students who have registered.  Contact the instructor if you have problem accessing the site.

Textbooks (online access at learn.rochester.edu > CSC 253 > Reserves > Materials on Reserve in the Library):

Software fundamentals : collected papers by David L. Parnas
Author: Parnas, David Lorge.
Imprint: Boston : Addison-Wesley, 2001.
On Reserve at: Carlson Library Reserve Desk 2nd Floor
Call Number: QA76.754 .P365 2001

Object-oriented Software Engineering
Author: Schach, Stephen R.
Imprint: New York : McGraw-Hill, c2008.
Available at school book store. On Reserve at: Carlson Library Reserve Desk 2nd Floor

Design patterns in Ruby [electronic resource]
Author: Olsen, Russ.
Imprint: Upper Saddle River, NJ : Addison-Wesley, c2008.
Available through Carlson Library at: Internet

Programming Languages: Application and Interpretation (http://cs.brown.edu/~sk/Publications/Books/ProgLangs/2007-04-26/)
Copyright © 2003-07, Shriram Krishnamurthi
(Also see Prof. Findler’s course EECS 321 at https://www.eecs.northwestern.edu/~robby/courses/)

Learn You a Haskell for Great Good!
A Beginner’s Guide
by Miran Lipovača (http://learnyouahaskell.com)
No Starch Press, April 2011.

Programming Language Pragmatics, 4th Edition
Author: Scott, Michael L.
On Reserve at: Carlson Library Reserve Desk 2nd Floor
Call Number: CRL PersCpy

Other Materials

Ruby under a microscope [electronic resource] : an illustrated guide to Ruby internals
Author: Shaughnessy, Pat.
Imprint: San Francisco : No Starch Press, [2014]
Available at school book store.  Also on Reserve at: Internet
Fundamentals of software engineering
Author: Ghezzi, Carlo.
Imprint: Upper Saddle River, N.J. : Prentice Hall, c2003.
On Reserve at: Carlson Library Reserve Desk 2nd Floor
Call Number: QA76.758 .G47 2003

Topics:

See schedule

 

Policies for CSC 2/453

The workload will be heavy.   Be sure to read instructions for each assignment and exam carefully, start the assignment early, know where/when to seek help, and work with peers.

Grades will be released periodically to Blackboard, the University’s on-line course management system.  

Attendance and Class Participation

Class attendance is mandatory.  Please arrive on time.  I expect to start at 3:25 sharp, and late arrivals disturb the folks who are already there.    You are encourage to ask or answer questions in class.  I may call on you just to know what you think.  As a general rule, if there’s something you don’t understand, make me stop and explain it.  There are probably a dozen people sitting around you who didn’t understand it either, but don’t have the nerve to say so.  Likewise, if I’m belaboring something that everyone understands, prod me to move on.

I will assign reading before and after lectures.   Reading is mandatory  It includes all lecture slides released to Blackboard, and textbook chapters/sections listed on the first slide of each lecture.   Keep in mind that the exams include topics covered in class and in the required reading. 

Late Submission Policy

A student may have a total of two extra days in all assignments.  They can be used as either a one-day extension for two assignments, or a two-day extension for one assignment.  A student must inform the TA about the extension before the due time.  No other late submission is permitted.

Academic Honesty

Student conduct in CSC 2/453 is governed by the College Academic Honesty Policy, the Undergraduate Laboratory Policies of the Computer Science Department, and the University’s Acceptable Use Policy for Information Technology.  I helped to draft some of the descriptions.  I believe in them strongly, and will enforce them aggressively.

The following are details specific to CSC 2/453.

Exams in CSC 2/453 must be strictly individual work.

Collaboration on programming assignments among team members is of course expected.  Collaboration on assignments acrossteams is encouraged at the level of ideas.  Feel free to ask each other questions, brainstorm on algorithms, or work together at a whiteboard.  You may not claim work as your own, however, unless you transform the ideas into substance by yourself.  Among other things, this means that you must leave any brainstorming sessions with no written or electronic notes—only what you carry in your head.

If you use the work of others (e.g., you download a function from the web at the last minute so that you can get the rest of your project working), then (1) either you must have the author’s explicit permission or the material must be publicly available, and (2) you must label what you copied, clearly and prominently, when you hand it in.  You will of course get points only for the parts of your assignment that you wrote yourself.

To minimize the temptation to steal code, all students are expected to protect any directories or on-line repositories in which they do their work.

For purposes of this class, academic dishonesty is defined as

  • Any attempt to pass off work on an exam or quiz that didn’t come straight out of your own head.
  • Any collaboration on assignments beyond the sharing of ideas, unless the collaborating parties clearly and prominently explain exactly who did what, at turn-in time.
  • Any activity that has the effect of significantly impairing the ability of another student to learn.  Examples here might include destroying the work of others, interfering with their access to resources, or deliberately providing them with misleading information.

Note that grades in CSC 2/453 are assigned on the basis of individual merit rather than relative standing, so there is no benefit—even a dishonest one—to be gained by sabotaging the work of others.

I work under the assumption that students are honest.  I will not go looking for exceptions.  If I discover one, however, I will come down on it very hard.  Over the past few years, I have submitted about a dozen cases to the College Board on Academic Honesty.  All resulted in major penalties for the students involved.

Character Co-Occurrence in Shakespeare’s Sonnets and the Bible

Co-Occurrence Blog Cover

This past summer, I’ve had the pleasure of working with Professor Chen Ding, Lucinda Liu, and Professor Daniel Gildea on an all-timescale co-occurrence analysis algorithm for optimizing microprocessor storage usage. This analysis can efficiently provide co-occurrence ratios for multiple timescales, which are time allowed for or taken by a process or sequence of events. The timescale is used to determine the likelihood of two events occurring together within that time window, giving a co-occurrence ratio. The developed algorithm is unique in its ability to calculate co-occurrence ratios for multiple timescales more efficiently than a brute-force method.

An initial pass of a trace of objects stores the distance between different elements of the trace. These distances can be used to see where gaps between trace objects are to wide to fall in the same time window, giving us a count of absence windows. The beauty of this algorithm is that the expensive operation, the initial pass of the trace, only needs to be done once to calculate timescale analysis of all pairs in a trace. By counting absence windows, joint and single frequencies can be determined.

We define the co-occurrence ratio to be the joint frequency of the pair divided by the single frequency of a given element. The given element is known to be present in a time window, meaning that the co-occurrence ratio represents the probability of finding the other element in the same time window. This makes the co-occurrence ratio a conditional probability.

This analysis was initially intended for use in optimizing processor cache utilization, by placing frequently co-occurring memory objects together in memory. The precise explanation can be found this paper. However, this concept can be extrapolated to any trace, whether it be a trace of words, or music notes, or pixels in a photo.

We applied our algorithm to Shakespeare’s Sonnets and the King James Bible, treating each character as a memory access taking one unit of time, skipping symbols and spaces. The letters, ignoring capitalization, are treated as memory accesses. We used timescales of 2, 5, and 10 to look at adjacent pairs, what one hand can type, and what two hands can type. Below are links to the data files and analysis of Shakespeare’s Sonnets and the King James Bible for multiple timescales using our algorithm:

Shakespeare’s Sonnets Timescale 2 Timescale 5 Timescale 10
King James Bible Timescale 2 Timescale 5 Timescale 10

The data can be interpreted as the conditional probability of seeing the second character given the first character is present in a given time window. Each individual character appears the same number of windows as the timescale size. So, if a second character is always adjacent to the first character on the same side the maximum co-occurrence ratio should be (timescale – 1)timescale. The reason for this is that there will be one window that includes the first character but not the second.

For example, the character ‘q’ should always precede the character ‘u’. So, given a time window with ‘q’ the probability seeing ‘u’ in the same window should be at least (timescale – 1)timescale. This means that all pairs with a co-occurrence ratio above that value have the second character on both sides of the first character like in the case of all word containing the substring “eve”. This is why for a timescale of 2 in Shakespeare’s Sonnets the pair (q, u) can be beaten by pairs like (x, e), but with larger timescales u’s from other words boost the (q, u) co-occurrence to put it in the lead.

Co-Occurrence Diagram

An example from Shakespeare’s Fourth Sonnet. Note how with the pair (q, u) the first window contains ‘q’ but not ‘u’ while the other nine windows have both characters. Also, the ‘q’ present in this trace appears in the same number of windows as the timescale size.

It is important to note that this method of co-occurrence analysis is not tallying frequencies. So when the pair (q, u) has the highest co-occurrence ratio, it does not mean that is the most common pair. Since the character ‘q’ is rarely used in the English language, its single occurrences are low, while its joint occurrences with the character ‘u’ are high. This is why for all the tests above many of the pairs with the highest affinities are uncommon consonants paired with a much more common vowel, like ‘e’. In both texts where the timescale 10 analyses were used, the top 10 pairs, excluding (q, u), have the character ‘e’ as a second character.

The data collected through this analysis has numerous uses outside of literature. The co-occurrence information can be used to evaluate the querty keyboard layout, or be used in speech therapy. Both the texts used here are from the same era, the turn of the sixteenth century into the seventeenth. It is possible that the character co-occurrence ratios could change with modern text or transcribed speech. Other than analyzing text, this analysis can be applied to images or videos for facial or object recognition.

I hope that this interesting re-application of memory layout analysis was entertaining to read about and I’d like to thank Professor Chen Ding, Lucinda Liu, and Professor Daniel Gildea for working with me on this project.

Image Sources: https://upload.wikimedia.org/wikipedia/commons/f/f6/Sonnets1609titlepage.jpg
https://upload.wikimedia.org/wikipedia/commons/e/e8/King-James-Version-Bible-first-edition-title-page-1611.png

CSC 254/454 Fall 2018

CSC 254/454 Fall 2018

Programming Language Design and Implementation

Course description and prerequisites

Policies for grading, attendance, and academic honesty (updated 8/27)

Teaching Staff and Office Hours: 

  • Prof. Chen Ding, Fridays 11am to 12pm in Wegmans Hall 3407, x51373.
  • Alan, 12pm-1pm Friday, Wegmans 2215
  • Alex, 11am-12 Thursday, Wegmans 3201
  • Jason, 12:30pm-1:30pm Tuesday, Hylan 301 (CS Minor’s Lab)
  • Jie, 2pm-4pm Tuesday, Wegmans 2311
  • Michael, 9am-10am Wednesday, Hylan 301 (CS Minor’s Lab)
  • Princeton, 12:45pm-1:45pm Wednesday, Hylan 301 (CS Minor’s Lab)
  • Wei, 4pm-6pm Tuesday, Wegmans 2602
  • Wentao, 3pm-5pm Wednesday, Wegmans 2207

Help Sessions

  • 5pm to 6pm Wednesday, Gavett 301
  • 3:30pm to 4:30pm Thursday, Wegmans 1009

Course Schedule and Handouts (online access at learn.rochester.edu > CSC 254 > Handouts)

The initial schedule can be accessed here.  See learn.rochester.edu for the most recent version.  Contact the instructor if you have problem accessing the site.

Grading (tentative):

  • attendance and pop quizzes, 10%
  • mid-term and final exam, 15% and 20% of the remaining 90%
  • assignments and projects, 65% of the remaining 90%

Textbooks

 Scott, M: Programming Language Pragmatics, 4th Edition

Other Materials

No Starch Press
April 2011, 400 pp.
ISBN-13: 978-1-59327-283-8

Web page for 2017 course taught by Prof. Scott.

Policies for CSC 2/454

The workload will be heavy.   Be sure to read instructions carefully, start the assignment early, know where/when to seek help, and work with peers.

For group projects, in most cases all students receive the same grade for the group.   Team membership may be self-selected or assigned.  If you prefer, there is a possibility to work alone.  Contact the TA in charge.

Grades will be released periodically to Blackboard, the University’s on-line course management system.  

Attendance and Class Participation

Class attendance is mandatory.  Please arrive on time.  I expect to start at 10:25 sharp, and late arrivals disturb the folks who are already there.   I also plan to start many classes with a quiz.

My goal is to spend class time answering questions and explaining material in ways that complement the text.  In other words, lecture should complement the text, not rehash it.  This means, of course, that  reading is mandatory, and must be completed before the corresponding lecture.  If no one has questions or suggested discussion topics, I will call on you—so be prepared!

As a general rule, if there’s something you don’t understand, make me stop and explain it.  There are probably a dozen people sitting around you who didn’t understand it either, but don’t have the nerve to say so.  Likewise, if I’m belaboring something that everyone understands, prod me to move on.

 Prof. Scott has made his lecture notes available on-line, but keep in mind that the exams may include topics covered in class, even if they are not in the text book or lecture notes. 

Project Help Sessions

 The time and location are fixed each week.  Attendance is voluntary.   There are two sessions each week covering the same topics, which will be given in announcements at the beginning of the week.

No Late Assignments

It is my strict policy not to accept late assignments.  Exceptions will be made only by the instructor.  Note, however, that I am extremely generous with partial credit, so turn in what you have.

Every semester I have students who let a due date pass.  When I ask them what happened they say “Oh, I didn’t finish, so I didn’t turn anything in.”  Then I have to give them a zero.  If they had turned in even some reasonable preliminary thoughts on how they might have done the assignment—without a single line of code—they often could have received as much as 30% of the total points.  This can easily make the difference between letter grades at the end of the semester.

So if it looks like you aren’t going to make a due date, don’t keep debugging down to the wire.  Stop an hour early and take the time to organize what you have and put together a write-up that presents it in the best possible light.  Your transcript will love you for it. 

Academic Honesty

Student conduct in CSC 2/454 is governed by the College Academic Honesty Policy, the Undergraduate Laboratory Policies of the Computer Science Department, and the University’s Acceptable Use Policy for Information Technology.  I helped to draft some of the descriptions.  I believe in them strongly, and will enforce them aggressively.

The following are details specific to CSC 2/454.

Exams and quizes in CSC 2/454 must be strictly individual work.

Collaboration on programming assignments among team members is of course expected.  Collaboration on assignments acrossteams is encouraged at the level of ideas.  Feel free to ask each other questions, brainstorm on algorithms, or work together at a whiteboard.  You may not claim work as your own, however, unless you transform the ideas into substance by yourself.  Among other things, this means that you must leave any brainstorming sessions with no written or electronic notes—only what you carry in your head.

If you use the work of others (e.g., you download a function from the web at the last minute so that you can get the rest of your project working), then (1) either you must have the author’s explicit permission or the material must be publicly available, and (2) you must label what you copied, clearly and prominently, when you hand it in.  You will of course get points only for the parts of your assignment that you wrote yourself.

To minimize the temptation to steal code, all students are expected to protect any directories or on-line repositories in which they do their work.

For purposes of this class, academic dishonesty is defined as

  • Any attempt to pass off work on an exam or quiz that didn’t come straight out of your own head.
  • Any collaboration on assignments beyond the sharing of ideas, unless the collaborating parties clearly and prominently explain exactly who did what, at turn-in time.
  • Any activity that has the effect of significantly impairing the ability of another student to learn.  Examples here might include destroying the work of others, interfering with their access to resources, or deliberately providing them with misleading information.

Note that grades in CSC 2/454 are assigned on the basis of individual merit rather than relative standing, so there is no benefit—even a dishonest one—to be gained by sabotaging the work of others.

I work under the assumption that students are honest.  I will not go looking for exceptions.  If I discover one, however, I will come down on it very hard.  Over the past few years, I have submitted about a dozen cases to the College Board on Academic Honesty.  All resulted in major penalties for the students involved.