[Plplot-devel] java install changes

[Alan W. Irwin <irwin@be...>]

I received no response on the java source install question so I made some
executive decisions: the class files will be retained for
...lib/java/plplot/core. My understanding is these binary files are analogous
to a library in the sense they are required to run any application that uses
the java front end to plplot.  Thus, like a library I install only the
binary *.class files and not the source *.java files.

The situation is different for all the other examples where we install the
source but no binaries.  To follow this idea for the java examples, the
*.java files (but not the *.class files) are now installed in
.../lib/java/plplot/examples.  Furthermore, the new README I created (see
plplot/examples/java/README) that explains how to build the java examples
either from the tmp location or the install location is also installed in
.../lib/java/plplot/examples.

Joao, I wrote those instructions at your suggestion.  By all means please
give the instructions a try, and let me know if they need any additions.

Alan

email: irwin@...
phone: 250-727-2902	FAX: 250-721-7715
snail-mail:
Dr. Alan W. Irwin
Department of Physics and Astronomy,
University of Victoria, P.O. Box 3055,
Victoria, British Columbia, Canada, V8W 3P6
__________________________

Linux-powered astrophysics
__________________________

Re: [Plplot-devel] Re: Embedded single precision in the matrix library

[Maurice LeBrun <mjl@ga...>]

Alan W. Irwin writes:
 > Point well taken, but I have investigated further, and there is more to this
 > story that I didn't understand before.  From the above example $ y -
 > 3.123456 has access to the full ~17 digit precision of y before subtracting the
 > constant from it so there are actually still 10 significant digits left in
 > the result (note the last two "81" digits are incorrect because the internal
 > precision of y is roughly 17 digits.)
 > 
 > But look how the corresponding matrix result does not act this way.
 > 
 > pltcl> set tcl_precision 12
 > 12
 > pltcl> matrix a f 1 = {3.1234567890123456789}
 > a
 > pltcl> puts [expr [a 0] - 3.123456]
 > 7.89010000002e-07
 > 
 > There are 5 fewer significant digits in this result than for the y - const
 > result.
 > 
 > My mental model of what is going on here is as follows: unlike $y - const,
 > [a 0] - const only has access to tcl_precision digits of precision for
 > matrix values. In other words set tcl_precision effectively sets the
 > internal precision of matrix calculations rather than simply limiting the
 > number of digits emitted for results.

The story becomes more interesting.  I believe the two representations
(variable or tclMatrix) would've given the same result in pre-Tcl8.0.  The
reason being that in the old Tcl, "everything's a string".  But no longer --
the variable that you create with "set" is "dual-ported", meaning it has both
a binary and string representation.  The binary one is used in expression
evaluations and so is more accurate.

I've been poring over the documentation, and I think it's feasible to change
tclMatrix to emit objects instead of strings, which seems to be the right way
to really fix this.  Also will help a lot with performance.  The object is
equipped with procedure calls to convert it to strings when necessary.
Unfortunately this is a pretty major undertaking, and not one I care to get
into right now.

So as for a stopgap measure, I'll change it to carry 12 digits of precision,
both internally and externally.  I tried 17 but didn't like the result.  E.g.

pltcl> matrix c f 3 = {3.2 4.5 5.7}
c
pltcl> puts [c *]
3.2000000000000002 4.5 5.7000000000000002

which the tclvars man page warns about.

-- 
Maurice LeBrun    mjl@...

Re: [Plplot-devel] Re: Embedded single precision in the matrix library

[Maurice LeBrun <mjl@ga...>]

Alan W. Irwin writes:
 > Point well taken, but I have investigated further, and there is more to this
 > story that I didn't understand before.  From the above example $ y -
 > 3.123456 has access to the full ~17 digit precision of y before subtracting the
 > constant from it so there are actually still 10 significant digits left in
 > the result (note the last two "81" digits are incorrect because the internal
 > precision of y is roughly 17 digits.)
 > 
 > But look how the corresponding matrix result does not act this way.
 > 
 > pltcl> set tcl_precision 12
 > 12
 > pltcl> matrix a f 1 = {3.1234567890123456789}
 > a
 > pltcl> puts [expr [a 0] - 3.123456]
 > 7.89010000002e-07
 > 
 > There are 5 fewer significant digits in this result than for the y - const
 > result.
 > 
 > My mental model of what is going on here is as follows: unlike $y - const,
 > [a 0] - const only has access to tcl_precision digits of precision for
 > matrix values. In other words set tcl_precision effectively sets the
 > internal precision of matrix calculations rather than simply limiting the
 > number of digits emitted for results.

You're right, it's still not really right.  Will look into it some more.

-- 
Maurice LeBrun    mjl@...

Re: [Plplot-devel] Re: Embedded single precision in the matrix library

[Alan W. Irwin <irwin@be...>]

On Tue, 15 Jan 2002, Maurice LeBrun wrote:

> Alan W. Irwin writes:
>  > Thanks for your fix.  At first I thought there was a 12-digit limit to the
>  > matrix precision, but that is just the default value of tcl_precision.  If I
>  > set it to 17 I get full double-precision results.
>  >
>  > BTW, tcl_precision doesn't seem to have universal application.  My tests
>  > indicated the internal precision of ordinary variables in pltcl was 17
>  > digits regardless of what tcl_precision value was set.  For example with
>  > the default (12) value of tcl_precision I get the following results:
>  >
>  > pltcl> set y 3.12345678901234567890
>  > 3.12345678901234567890
>  > pltcl> puts [expr $y - 3.123456]
>  > 7.89012345681e-07
>    1 234567890ab
>
> ..i.e. 12 digits of precision.

Point well taken, but I have investigated further, and there is more to this
story that I didn't understand before.  From the above example $ y -
3.123456 has access to the full ~17 digit precision of y before subtracting the
constant from it so there are actually still 10 significant digits left in
the result (note the last two "81" digits are incorrect because the internal
precision of y is roughly 17 digits.)

But look how the corresponding matrix result does not act this way.

pltcl> set tcl_precision 12
12
pltcl> matrix a f 1 = {3.1234567890123456789}
a
pltcl> puts [expr [a 0] - 3.123456]
7.89010000002e-07

There are 5 fewer significant digits in this result than for the y - const
result.

My mental model of what is going on here is as follows: unlike $y - const,
[a 0] - const only has access to tcl_precision digits of precision for
matrix values. In other words set tcl_precision effectively sets the
internal precision of matrix calculations rather than simply limiting the
number of digits emitted for results.

>  > I would prefer matrix to act the same way regardless ot tcl_precision.
>  > Therefore, could you just set the matrix precision to 17 digits when PLFLT
>  > is double and 7 digits otherwise?  The other alternative I am considering is
>  > to set tcl_precision to 17 in each of the examples, but I prefer not to do
>  > that if there is an automatic PLFLT-style solution you can use for
>  > libmatrix.
>
> I really think tying it to tcl_precision is the right thing to do.
> It doesn't have any effect on internal representation, just the number
> of digits emitted when converting the PLFLT to a string.

That would be okay with me, but as you can see from the above example it
is affecting the (effective) internal precision, and not just the digits
being emitted.

Hope you can get this matrix problem sorted out.

Alan

RE: [Plplot-devel] Java install questions

[Alan W. Irwin <irwin@be...>]

On Tue, 15 Jan 2002, Geoffrey Furnish wrote:

> [...] However, your
> proposal doesn't seem right to me either, since it seems kludgy to have
> to have two additions to classpath to use the java stuff.  Maybe you
> could take the position that you only need the first one for normal
> client codes, and the second one is just to reach the PLplot Java
> demos,

yes.  Also, I was quite happy to see that your java package structure still
worked fine if you assembled the bits and pieces from separate directory
trees with the appropriate colon-separated list of directories in CLASSPATH.
Of course, just because something is possible doesn't mean you have to do it
so see below.

> but to me it makes more sense to have one classpath component
> which reaches all things plplot/java.

OK.  I will go along with this decision.

> Personally, I'd just leave it alone for now, figuring that it wil
> lhave to change later once we learn the ways of upscale Java packagers
> well enough to follow suit fashionably.

OK, to be revisited later when one of us knows more about jar files, etc.

You didn't answer my question about the sources.  Currently there are no
java sources anywhere in the install directory tree.  I believe at least the
java example sources should be there (by analogy with the source code that
is installed for the other examples). Assuming you agree on the examples, do
you also want the core sources installed?

Alan