view etc/MOTIVATION @ 665:fdefd0186b75

[xemacs-hg @ 2001-09-20 06:28:42 by ben] The great integral types renaming. The purpose of this is to rationalize the names used for various integral types, so that they match their intended uses and follow consist conventions, and eliminate types that were not semantically different from each other. The conventions are: -- All integral types that measure quantities of anything are signed. Some people disagree vociferously with this, but their arguments are mostly theoretical, and are vastly outweighed by the practical headaches of mixing signed and unsigned values, and more importantly by the far increased likelihood of inadvertent bugs: Because of the broken "viral" nature of unsigned quantities in C (operations involving mixed signed/unsigned are done unsigned, when exactly the opposite is nearly always wanted), even a single error in declaring a quantity unsigned that should be signed, or even the even more subtle error of comparing signed and unsigned values and forgetting the necessary cast, can be catastrophic, as comparisons will yield wrong results. -Wsign-compare is turned on specifically to catch this, but this tends to result in a great number of warnings when mixing signed and unsigned, and the casts are annoying. More has been written on this elsewhere. -- All such quantity types just mentioned boil down to EMACS_INT, which is 32 bits on 32-bit machines and 64 bits on 64-bit machines. This is guaranteed to be the same size as Lisp objects of type `int', and (as far as I can tell) of size_t (unsigned!) and ssize_t. The only type below that is not an EMACS_INT is Hashcode, which is an unsigned value of the same size as EMACS_INT. -- Type names should be relatively short (no more than 10 characters or so), with the first letter capitalized and no underscores if they can at all be avoided. -- "count" == a zero-based measurement of some quantity. Includes sizes, offsets, and indexes. -- "bpos" == a one-based measurement of a position in a buffer. "Charbpos" and "Bytebpos" count text in the buffer, rather than bytes in memory; thus Bytebpos does not directly correspond to the memory representation. Use "Membpos" for this. -- "Char" refers to internal-format characters, not to the C type "char", which is really a byte. -- For the actual name changes, see the script below. I ran the following script to do the conversion. (NOTE: This script is idempotent. You can safely run it multiple times and it will not screw up previous results -- in fact, it will do nothing if nothing has changed. Thus, it can be run repeatedly as necessary to handle patches coming in from old workspaces, or old branches.) There are two tags, just before and just after the change: `pre-integral-type-rename' and `post-integral-type-rename'. When merging code from the main trunk into a branch, the best thing to do is first merge up to `pre-integral-type-rename', then apply the script and associated changes, then merge from `post-integral-type-change' to the present. (Alternatively, just do the merging in one operation; but you may then have a lot of conflicts needing to be resolved by hand.) Script `fixtypes.sh' follows: ----------------------------------- cut ------------------------------------ files="*.[ch] s/*.h m/*.h config.h.in ../configure.in Makefile.in.in ../lib-src/*.[ch] ../lwlib/*.[ch]" gr Memory_Count Bytecount $files gr Lstream_Data_Count Bytecount $files gr Element_Count Elemcount $files gr Hash_Code Hashcode $files gr extcount bytecount $files gr bufpos charbpos $files gr bytind bytebpos $files gr memind membpos $files gr bufbyte intbyte $files gr Extcount Bytecount $files gr Bufpos Charbpos $files gr Bytind Bytebpos $files gr Memind Membpos $files gr Bufbyte Intbyte $files gr EXTCOUNT BYTECOUNT $files gr BUFPOS CHARBPOS $files gr BYTIND BYTEBPOS $files gr MEMIND MEMBPOS $files gr BUFBYTE INTBYTE $files gr MEMORY_COUNT BYTECOUNT $files gr LSTREAM_DATA_COUNT BYTECOUNT $files gr ELEMENT_COUNT ELEMCOUNT $files gr HASH_CODE HASHCODE $files ----------------------------------- cut ------------------------------------ `fixtypes.sh' is a Bourne-shell script; it uses 'gr': ----------------------------------- cut ------------------------------------ #!/bin/sh # Usage is like this: # gr FROM TO FILES ... # globally replace FROM with TO in FILES. FROM and TO are regular expressions. # backup files are stored in the `backup' directory. from="$1" to="$2" shift 2 echo ${1+"$@"} | xargs global-replace "s/$from/$to/g" ----------------------------------- cut ------------------------------------ `gr' in turn uses a Perl script to do its real work, `global-replace', which follows: ----------------------------------- cut ------------------------------------ : #-*- Perl -*- ### global-modify --- modify the contents of a file by a Perl expression ## Copyright (C) 1999 Martin Buchholz. ## Copyright (C) 2001 Ben Wing. ## Authors: Martin Buchholz <martin@xemacs.org>, Ben Wing <ben@xemacs.org> ## Maintainer: Ben Wing <ben@xemacs.org> ## Current Version: 1.0, May 5, 2001 # This program is free software; you can redistribute it and/or modify # it under the terms of the GNU General Public License as published by # the Free Software Foundation; either version 2, or (at your option) # any later version. # # This program is distributed in the hope that it will be useful, but # WITHOUT ANY WARRANTY; without even the implied warranty of # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU # General Public License for more details. # # You should have received a copy of the GNU General Public License # along with XEmacs; see the file COPYING. If not, write to the Free # Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA # 02111-1307, USA. eval 'exec perl -w -S $0 ${1+"$@"}' if 0; use strict; use FileHandle; use Carp; use Getopt::Long; use File::Basename; (my $myName = $0) =~ s@.*/@@; my $usage=" Usage: $myName [--help] [--backup-dir=DIR] [--line-mode] [--hunk-mode] PERLEXPR FILE ... Globally modify a file, either line by line or in one big hunk. Typical usage is like this: [with GNU print, GNU xargs: guaranteed to handle spaces, quotes, etc. in file names] find . -name '*.[ch]' -print0 | xargs -0 $0 's/\bCONST\b/const/g'\n [with non-GNU print, xargs] find . -name '*.[ch]' -print | xargs $0 's/\bCONST\b/const/g'\n The file is read in, either line by line (with --line-mode specified) or in one big hunk (with --hunk-mode specified; it's the default), and the Perl expression is then evalled with \$_ set to the line or hunk of text, including the terminating newline if there is one. It should destructively modify the value there, storing the changed result in \$_. Files in which any modifications are made are backed up to the directory specified using --backup-dir, or to `backup' by default. To disable this, use --backup-dir= with no argument. Hunk mode is the default because it is MUCH MUCH faster than line-by-line. Use line-by-line only when it matters, e.g. you want to do a replacement only once per line (the default without the `g' argument). Conversely, when using hunk mode, *ALWAYS* use `g'; otherwise, you will only make one replacement in the entire file! "; my %options = (); $Getopt::Long::ignorecase = 0; &GetOptions ( \%options, 'help', 'backup-dir=s', 'line-mode', 'hunk-mode', ); die $usage if $options{"help"} or @ARGV <= 1; my $code = shift; die $usage if grep (-d || ! -w, @ARGV); sub SafeOpen { open ((my $fh = new FileHandle), $_[0]); confess "Can't open $_[0]: $!" if ! defined $fh; return $fh; } sub SafeClose { close $_[0] or confess "Can't close $_[0]: $!"; } sub FileContents { my $fh = SafeOpen ("< $_[0]"); my $olddollarslash = $/; local $/ = undef; my $contents = <$fh>; $/ = $olddollarslash; return $contents; } sub WriteStringToFile { my $fh = SafeOpen ("> $_[0]"); binmode $fh; print $fh $_[1] or confess "$_[0]: $!\n"; SafeClose $fh; } foreach my $file (@ARGV) { my $changed_p = 0; my $new_contents = ""; if ($options{"line-mode"}) { my $fh = SafeOpen $file; while (<$fh>) { my $save_line = $_; eval $code; $changed_p = 1 if $save_line ne $_; $new_contents .= $_; } } else { my $orig_contents = $_ = FileContents $file; eval $code; if ($_ ne $orig_contents) { $changed_p = 1; $new_contents = $_; } } if ($changed_p) { my $backdir = $options{"backup-dir"}; $backdir = "backup" if !defined ($backdir); if ($backdir) { my ($name, $path, $suffix) = fileparse ($file, ""); my $backfulldir = $path . $backdir; my $backfile = "$backfulldir/$name"; mkdir $backfulldir, 0755 unless -d $backfulldir; print "modifying $file (original saved in $backfile)\n"; rename $file, $backfile; } WriteStringToFile ($file, $new_contents); } } ----------------------------------- cut ------------------------------------ In addition to those programs, I needed to fix up a few other things, particularly relating to the duplicate definitions of types, now that some types merged with others. Specifically: 1. in lisp.h, removed duplicate declarations of Bytecount. The changed code should now look like this: (In each code snippet below, the first and last lines are the same as the original, as are all lines outside of those lines. That allows you to locate the section to be replaced, and replace the stuff in that section, verifying that there isn't anything new added that would need to be kept.) --------------------------------- snip ------------------------------------- /* Counts of bytes or chars */ typedef EMACS_INT Bytecount; typedef EMACS_INT Charcount; /* Counts of elements */ typedef EMACS_INT Elemcount; /* Hash codes */ typedef unsigned long Hashcode; /* ------------------------ dynamic arrays ------------------- */ --------------------------------- snip ------------------------------------- 2. in lstream.h, removed duplicate declaration of Bytecount. Rewrote the comment about this type. The changed code should now look like this: --------------------------------- snip ------------------------------------- #endif /* The have been some arguments over the what the type should be that specifies a count of bytes in a data block to be written out or read in, using Lstream_read(), Lstream_write(), and related functions. Originally it was long, which worked fine; Martin "corrected" these to size_t and ssize_t on the grounds that this is theoretically cleaner and is in keeping with the C standards. Unfortunately, this practice is horribly error-prone due to design flaws in the way that mixed signed/unsigned arithmetic happens. In fact, by doing this change, Martin introduced a subtle but fatal error that caused the operation of sending large mail messages to the SMTP server under Windows to fail. By putting all values back to be signed, avoiding any signed/unsigned mixing, the bug immediately went away. The type then in use was Lstream_Data_Count, so that it be reverted cleanly if a vote came to that. Now it is Bytecount. Some earlier comments about why the type must be signed: This MUST BE SIGNED, since it also is used in functions that return the number of bytes actually read to or written from in an operation, and these functions can return -1 to signal error. Note that the standard Unix read() and write() functions define the count going in as a size_t, which is UNSIGNED, and the count going out as an ssize_t, which is SIGNED. This is a horrible design flaw. Not only is it highly likely to lead to logic errors when a -1 gets interpreted as a large positive number, but operations are bound to fail in all sorts of horrible ways when a number in the upper-half of the size_t range is passed in -- this number is unrepresentable as an ssize_t, so code that checks to see how many bytes are actually written (which is mandatory if you are dealing with certain types of devices) will get completely screwed up. --ben */ typedef enum lstream_buffering --------------------------------- snip ------------------------------------- 3. in dumper.c, there are four places, all inside of switch() statements, where XD_BYTECOUNT appears twice as a case tag. In each case, the two case blocks contain identical code, and you should *REMOVE THE SECOND* and leave the first.
author ben
date Thu, 20 Sep 2001 06:31:11 +0000
parents 3ecd8885ac67
children
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STUDIES FIND REWARD OFTEN NO MOTIVATOR

Creativity and intrinsic interest diminish if task is done for gain

By Alfie Kohn
Special to the Boston Globe
[reprinted with permission of the author
 from the Monday 19 January 1987 Boston Globe]

In the laboratory, rats get Rice Krispies.  In the classroom the top
students get A's, and in the factory or office the best workers get
raises.  It's an article of faith for most of us that rewards promote
better performance.

But a growing body of research suggests that this law is not nearly as
ironclad as was once thought.  Psychologists have been finding that
rewards can lower performance levels, especially when the performance
involves creativity.

A related series of studies shows that intrinsic interest in a task -
the sense that something is worth doing for its own sake - typically
declines when someone is rewarded for doing it.

If a reward - money, awards, praise, or winning a contest - comes to
be seen as the reason one is engaging in an activity, that activity
will be viewed as less enjoyable in its own right.

With the exception of some behaviorists who doubt the very existence
of intrinsic motivation, these conclusions are now widely accepted
among psychologists.  Taken together, they suggest we may unwittingly
be squelching interest and discouraging innovation among workers,
students and artists.

The recognition that rewards can have counter-productive effects is
based on a variety of studies, which have come up with such findings
as these: Young children who are rewarded for drawing are less likely
to draw on their own that are children who draw just for the fun of
it.  Teenagers offered rewards for playing word games enjoy the games
less and do not do as well as those who play with no rewards.
Employees who are praised for meeting a manager's expectations suffer
a drop in motivation.

Much of the research on creativity and motivation has been performed
by Theresa Amabile, associate professor of psychology at Brandeis
University.  In a paper published early last year on her most recent
study, she reported on experiments involving elementary school and
college students.  Both groups were asked to make "silly" collages.
The young children were also asked to invent stories.

The least-creative projects, as rated by several teachers, were done
by those students who had contracted for rewards.  "It may be that
commissioned work will, in general, be less creative than work that is
done out of pure interest," Amabile said.

In 1985, Amabile asked 72 creative writers at Brandeis and at Boston
University to write poetry.  Some students then were given a list of
extrinsic (external) reasons for writing, such as impressing teachers,
making money and getting into graduate school, and were asked to think
about their own writing with respect to these reasons.  Others were
given a list of intrinsic reasons:  the enjoyment of playing with
words, satisfaction from self-expression, and so forth.  A third group
was not given any list.  All were then asked to do more writing.

The results were clear.  Students given the extrinsic reasons not only
wrote less creatively than the others, as judged by 12 independent
poets, but the quality of their work dropped significantly.  Rewards,
Amabile says, have this destructive effect primarily with creative
tasks, including higher-level problem-solving.  "The more complex the
activity, the more it's hurt by extrinsic reward," she said.

But other research shows that artists are by no means the only ones
affected.

In one study, girls in the fifth and sixth grades tutored younger
children much less effectively if they were promised free movie
tickets for teaching well.  The study, by James Gabarino, now
president of Chicago's Erikson Institute for Advanced Studies in Child
Development, showed that tutors working for the reward took longer to
communicate ideas, got frustrated more easily, and did a poorer job in
the end than those who were not rewarded.

Such findings call into question the widespread belief that money is
an effective and even necessary way to motivate people.  They also
challenge the behaviorist assumption that any activity is more likely
to occur if it is rewarded.  Amabile says her research "definitely
refutes the notion that creativity can be operantly conditioned."

But Kenneth McGraw, associate professor of psychology at the
University of Mississippi, cautions that this does not mean
behaviorism itself has been invalidated.  "The basic principles of
reinforcement and rewards certainly work, but in a restricted context"
- restricted, that is, to tasks that are not especially interesting.

Researchers offer several explanations for their surprising findings
about rewards and performance.

First, rewards encourage people to focus narrowly on a task, to do it
as quickly as possible and to take few risks.  "If they feel that
'this is something I have to get through to get the prize,' they're
going to be less creative," Amabile said.

Second, people come to see themselves as being controlled by the
reward.  They feel less autonomous, and this may interfere with
performance.  "To the extent one's experience of being
self-determined is limited," said Richard Ryan, associate psychology
professor at the University of Rochester, "one's creativity will be
reduced as well."

Finally, extrinsic rewards can erode intrinsic interest.  People who
see themselves as working for money, approval or competitive success
find their tasks less pleasurable, and therefore do not do them as
well.

The last explanation reflects 15 years of work by Ryan's mentor at the
University of Rochester, Edward Deci.  In 1971, Deci showed that
"money may work to buy off one's intrinsic motivation for an activity"
on a long-term basis.  Ten years later, Deci and his colleagues
demonstrated that trying to best others has the same effect.  Students
who competed to solve a puzzle quickly were less likely than those who
were not competing to keep working at it once the experiment was over.

Control plays role

There is general agreement, however, that not all rewards have the
same effect.  Offering a flat fee for participating in an experiment -
similar to an hourly wage in the workplace - usually does not reduce
intrinsic motivation.  It is only when the rewards are based on
performing a given task or doing a good job at it - analogous to
piece-rate payment and bonuses, respectively - that the problem
develops.

The key, then, lies in how a reward is experienced.  If we come to
view ourselves as working to get something, we will no longer find
that activity worth doing in its own right.

There is an old joke that nicely illustrates the principle.  An
elderly man, harassed by the taunts of neighborhood children, finally
devises a scheme.  He offered to pay each child a dollar if they would
all return Tuesday and yell their insults again.  They did so eagerly
and received the money, but he told them he could only pay 25 cents on
Wednesday.  When they returned, insulted him again and collected their
quarters, he informed them that Thursday's rate would be just a penny.
"Forget it," they said - and never taunted him again.

Means to and end

In a 1982 study, Stanford psychologist Mark L. Lepper showed that any
task, no matter how enjoyable it once seemed, would be devalued if it
were presented as a means rather than an end.  He told a group of
preschoolers they could not engage in one activity they liked until
they first took part in another.  Although they had enjoyed both
activities equally, the children came to dislike the task that was a
prerequisite for the other.

It should not be surprising that when verbal feedback is experienced
as controlling, the effect on motivation can be similar to that of
payment.  In a study of corporate employees, Ryan found that those who
were told, "Good, you're doing as you /should/" were "significantly
less intrinsically motivated than those who received feedback
informationally."

There's a difference, Ryan says, between saying, "I'm giving you this
reward because I recognize the value of your work" and "You're getting
this reward because you've lived up to my standards."

A different but related set of problems exists in the case of
creativity.  Artists must make a living, of course, but Amabile
emphasizes that "the negative impact on creativity of working for
rewards can be minimized" by playing down the significance of these
rewards and trying not to use them in a controlling way.  Creative
work, the research suggests, cannot be forced, but only allowed to
happen.

/Alfie Kohn, a Cambridge, MA writer, is the author of "No Contest: The
Case Against Competition," recently published by Houghton Mifflin Co.,
Boston, MA.  ISBN 0-395-39387-6. /