Re: [Gnuplot-bugs] gnuplot locks up plotting log(x**0.5)/log(x)

[Thomas S. <t.s...@fz...>]

it doesn't happen for a fixed yrange.

so it must have something to do with autoscaling.

oh, 'gen_tics' in 'axis.c' tries to step from 0.499999999 to 0.500000000
in steps of 5.0e-17, this shouldn't happen...

'axis_checked_extend_empty_range' in 'axis.c' should catch this, but
it doesn't because it tests for "dmax-dmin == 0.0", but with
dmin=4.99999999999999888978e-01 and dmax=5.00000000000000111022e-01
the difference is
dmax-dmin=2.22044604925031308085e-16
which is obviously not zero but looks pretty much like DBL_EPSILON.

this patch should fix it:

--- axis.c.orig 2008-07-19 15:25:54.000000000 +0200
+++ axis.c      2008-12-31 01:12:38.000000000 +0100
@@ -308,7 +308,7 @@
            || axis_array[axis].max == -VERYLARGE))
        int_error(c_token, mesg);
 
-    if (dmax - dmin == 0.0) {
+    if (dmax - dmin <= DBL_EPSILON) {
        /* empty range */
        if (axis_array[axis].autoscale) {
            /* range came from autoscaling ==> widen it */



Nick Ellery-2 wrote:
> 
> Hi,
> 
> This was originally reported at
> https://bugs.edge.launchpad.net/ubuntu/+source/gnuplot/+bug/311236
> 
> Steps to recreate:
> $ gnuplot
> gnuplot> plot [2:4] log(x**0.5)/log(x)
> 
> gnuplot goes into an infinite loop (can be control-C'd out).
> 
> This is in version 4.2.4
> 
> ------------------------------------------------------------------------------
> _______________________________________________
> gnuplot-bugs mailing list
> gnu...@li...
> https://lists.sourceforge.net/lists/listinfo/gnuplot-bugs
> 
> 

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