implement parallel execute in scheme

Question

In SICP section 3.4 (serializers in scheme) on Currency there is a procedure called parallel-execute that is described but not implemented in MIT scheme. I wonder if anyone has actually implemented it; if not how would one get started in implementing such procedure?

http://mitpress.mit.edu/sicp/full-text/book/book-Z-H-23.html#%_sec_3.4.1

To implement that one would build it at the meta-circular interpreter level. — Dan D., Nov 20 '12 at 06:54

Óscar López · Answer 1 · 2012-11-20T18:23:53.450

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This is how I implemented parallel-execute for solving the exercises in section 3.4 of SICP, using Racket:

(define (parallel-execute . procs)
  (map thread-wait
       (map (lambda (proc) (thread proc))
            procs)))

I can't guarantee that it has the same semantics as the parallel-execute procedure defined in the book, but it allowed me to solve the exercises.

edited Nov 20 '12 at 18:23

answered Nov 20 '12 at 13:47

Óscar López

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@Mark waiting 'till all threads have finished their jobs before continuing with execution – Óscar López Nov 21 '12 at 13:19
In order to see changes to the accounts in sicp 3.4 section, you must run the balance procedure after using parallel-execute. Procedures that run in background threads won't display return values like when they're run on the main thread. – Joe Williamson Aug 19 '19 at 12:06
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This works perfectly in Racket. – Patrick Bucher Feb 26 '23 at 08:33

tiga · Answer 2 · 2014-11-06T08:02:12.680

7

This book's official site offers a implement parallel.scm. Open MIT Scheme like this:

mit-scheme -load PATH/parallel.scm

or put this

(load "PATH/parallel.scm")

at the head of your scheme source file.

edited Nov 06 '14 at 08:02

answered Nov 06 '14 at 07:38

tiga

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link broken as of april 2018. working link to parallel.scm [can be found here](https://mitpress.mit.edu/sites/default/files/sicp/psets/ps7/readme.html) – xdavidliu Apr 18 '18 at 19:59

score 3 · Answer 3 · answered May 29 '16 at 17:21

Actually you can load all the necessary implementations in racket with the following package. Just type this in either the definitions or the interactions window and the necessary package will be installed and when you need it, include the same comment in the definitions window:

(require (planet dyoo/sicp-concurrency:1:2/sicp-concurrency))

score 2 · Answer 4 · answered Nov 20 '12 at 19:54

In GNU Guile the procedure is implemented as parallel. It is there defined as a special form and available from (use-modules (ice-9 threads)). If you want to implement it yourself, you may have a look at the source code of this module.

implement parallel execute in scheme

4 Answers4