All Comp150CPA News

Comp150CPA Message 0024.txt from Alva L. Couch(couch)

You can use *my* instance of rebl in the following way: 
a) ssh to (you have access). 
b) run /usr/couch/bin/rebl (my local copy). 
It was a bit of a pain to get this running so feel free
to use mine! 

P.S. I'm an idiot!  The following rebl works fine: 

rebl> table :something, [:foo, :bar] => [:cat]
rebl> something <= [['alva', 'max', 1]]
rebl> something <= [['alva', 'george', 1]]
rebl> stdio <~ something.inspected
rebl> /tick
["alva", "max", 1]
["alva", "george", 1]

One can't just run stuff through stdio uninspected, 
because that will assert an artificial key relationship
on the first term of each tuple! 


Last changed Tue May 10 17:38:06 2011

Comp150CPA Message 0023.txt from Alva L. Couch(couch)

OOPS! I made an error on this page: 
Q: How can I get the bud simulator to work? It doesn't seem to... 
A: I played with it a bit just now and made sure that I installed
   it correctly. 

FLASH: I made an error in the following example: 

rebl> table :friends, [:f1,:f2]=>[:f3]
rebl> friends <= [['alva', 'george', 1]]
rebl> friends <= [['alva', 'fred', 1]]
rebl> stdio <~ friends
rebl> /tick
exception: Exception during Bud evaluation.
Exception: #<Bud::KeyConstraintError: Key conflict inserting ["alva", ["fred", 1]] into "stdio": existing tuple ["alva", ["george", 1]], key_cols = ["alva"]>.
Rule: stdio < (friends.~)

The reason that this didn't work is that I should have written 
 	stdio <~ friends.inspected
rather than 
	stdio <~ friends

Note: I took my lecture examples from the "bud cheat sheet" on the website. 
I was expecting you to do the exam *without* invoking the simulator. 
It is possible to do just from the "meanings" of the operators. 

Last changed Tue May 10 17:40:04 2011

Comp150CPA Message 0022.txt from Alva L. Couch(couch)

Q: How should I submit my final exam? 
A: I am not picky. You can: 
a) submit it to me on paper, in my mailbox in the 
   office or under my door. 
b) email it to me. 
c) use provide: 
   provide comp150cpa finalsubmit final.pdf 
No matter what you do, it is going to end up finally on paper, 
and be graded on paper, and then be scanned back in. 

Last changed Mon May 9 17:43:38 2011

Comp150CPA Message 0021.txt from Alva L. Couch(couch)

See for details on how to install bud. 

Last changed Thu May 5 10:15:42 2011

Comp150CPA Message 0020.txt from Alva L. Couch(couch)

A take-home final exam has been posted. 

After some careful thought -- and considering all of the stresses upon 
each of you this week -- I have decided upon a take-home final exam. 
I have posted this final in the timeline. I will be here all week and 
you may ask any and all questions of me (only).  

I would appreciate your answers to these questions by the time of the 
real final exam on May 10, 2011. I *must* have them by Fri May 13. 

- Prof. Couch

Last changed Mon May 2 12:49:44 2011

Comp150CPA Message 0019.txt from Alva L. Couch(couch)

Two notes: Quiz 2 this Wed (review posted); Assignment 7 posted and due next Monday. 

Last changed Mon Apr 25 14:01:35 2011

Comp150CPA Message 0018.txt from Alva L. Couch(couch)

Note: Pegasystems is coming to Tufts tonight after class in Halligan 111A. 
This is a premier provider of cloud solutions. And they're hiring. 

Last changed Wed Apr 20 14:41:33 2011

Comp150CPA Message 0017.txt from Alva L. Couch(couch)

Due to the hectic schedule for everyone this week, A6 is now due on Monday. 

Last changed Tue Apr 19 14:38:12 2011

Comp150CPA Message 0016.txt from Alva L. Couch(couch)

To get the BPMN modeler to work you have to install the whole STP, from
as appropriate.  Just installing the modeler isn't enough. Apologies! 
I have corrected the assignment writeup. 

Last changed Mon Apr 18 14:46:26 2011

Comp150CPA Message 0015.txt from Alva L. Couch(couch)

As part of my general plan of covering everything hot about cloud computing, 
I am thinking about covering the strangest cloud computing language of all: 
"bloom". It is a result of thinking from the opposite side of the fence; 
computer scientists experimenting with what the cloud can do. Your thoughts? 

Last changed Wed Apr 13 13:46:28 2011

Comp150CPA Message 0014.txt from Alva L. Couch(couch)

The image for the midterm review didn't show up... fixed....

Last changed Tue Apr 5 13:26:24 2011

Comp150CPA Message 0013.txt from Alva L. Couch(couch)

Could each of you *please* fill out a midterm course 
survey for this course *today*? Thanks! 

Last changed Mon Mar 28 14:53:24 2011

Comp150CPA Message 0012.txt from Alva L. Couch(couch)

An amusing puzzle for you: the way I started assignment 4 was with the lines:
input1 = LOAD 'file.dat' USING PigStorage() AS (f1:chararray, f2:chararray); 
input2 = FOREACH input1 GENERATE f2 AS f1, f1 AS f2; 
input3 = UNION input1, input2; 
input4 = FILTER input3 by f1<f2;
Using input1-4 saves some computation time later, if one is clever. 

Last changed Wed Mar 16 17:59:34 2011

Comp150CPA Message 0011.txt from Alva L. Couch(couch)

Q: I'm having trouble getting started with assignment 4. What do I do? 
A: Here is a simple hint for you. 

a) Start with input={A,B} where A knows B. 
b) Consider that CROSS input,input gives you {A,B,C,D} where
   (A,B) is in input and (C,D) is in input. 
c) If we filter, group, and count this properly, we have 
   one solution. 
This, however, is a really inefficient solution, and it is possible 
to do much better. 

Last changed Sun Mar 13 20:54:53 2011

Comp150CPA Message 0010.txt from Alva L. Couch(couch)

I neglected to tell you and emphasize that the datastores I mentioned 
are not map/reduce based.  They are all distributed hash tables (DHTs).  
The main hadoop use case is a hadoop job whose results are served via 
a DHT.  DHTs excel at fast return of single objects by key, but do very 
poorly at satisfying regular SQL queries. 

Last changed Thu Mar 10 15:50:32 2011

Comp150CPA Message 0009.txt from Alva L. Couch(couch)

I updated assignment 4 for the extra credit problem I mentioned today. 

Last changed Wed Mar 9 18:33:52 2011

Comp150CPA Message 0008.txt from Alva L. Couch(couch)

WARNING: I am revising today's lecture substantively to better reflect 
current practice. I won't be posting all revisions until near classtime.

Last changed Wed Mar 9 13:45:29 2011

Comp150CPA Message 0007.txt from Alva L. Couch(couch)

I have posted an in-class exercise for part 2 of today's lecture, with answers.
I am not going to assign it in class, due to schedule; there is plenty
more to do. But it does contain some problems that might appear, e.g., on a 
midterm. So I have posted it on the timeline for your edification. 

Last changed Mon Mar 7 19:48:08 2011

Comp150CPA Message 0006.txt from Alva L. Couch(couch)

I changed *one* slide of "Scalability and Demand". The change is on Slide 21, 
titled "A time/space diagram for service". I find, generally, that it is better 
to think of t_network as the time outside the cloud, and to think of t_cloud
as *including* networking inside the cloud. I updated the diagram appropriately. 
I made this change mostly because I seem to have assumed that definition 
for the rest of the course, e.g., for this week's lectures...

Last changed Mon Feb 14 14:32:24 2011

Comp150CPA Message 0005.txt from Alva L. Couch(couch)

There seems to be a bit of a misunderstanding about Assignment 1. 

The intent is that you store something on the server and then 
generate the table from that. You can modify the table 
in advance, safely, because you are just putting into it 
what would come back from the server. But what I thought everyone
would do is to modify the server, and schedule a reload from
that modification, which is strongly consistent, so we know it'll
update the table properly. 

But you can't get away with *not* putting data on the server. 
We will test this in the simplest possible way, by visiting your 
page via a full reload.  If you didn't store data on the server, 
it will disappear!

Last changed Mon Feb 14 12:07:57 2011

Comp150CPA Message 0004.txt from Alva L. Couch(couch)

For more info on Serializable, see a link to a tutorial on the hint page. 
In most cases, all you have to do is to declare your class as serializable. 

Last changed Wed Feb 9 19:28:20 2011

Comp150CPA Message 0003.txt from Alva L. Couch(couch)

Due to the snow day, the deadline for Assignment 1 is now Monday, Feb 14. 

Last changed Mon Feb 7 18:07:53 2011

Comp150CPA Message 0002.txt from Alva L. Couch(couch)

There is a possibility of an off-campus study group: 
A couple of students have expressed interest in forming an 
"off campus study group" for Comp150CPA. You can mail me
for more details, or we can discuss it in class tomorrow. 
- Prof. Couch

Last changed Sun Feb 6 20:35:43 2011

Comp150CPA Message 0001.txt from Alva L. Couch(couch)

Welcome to Comp150CPA. Look here for important information 
about the course, including comments on lectures, answers
to questions, etc. 

Last changed Mon Jan 24 14:26:13 2011