The Persistence of Vision Raytracer (POV-Ray).
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Opened by Christoph Lipka - 2013-08-20
Last edited by William F Pokorny - 2016-12-10
FS#304 - #for-loop may fail to perform last iteration
Using an end value of 1048576 or larger in a #for loop will cause the last iteration to be skipped, as can be demonstrated by the following code:
#declare N = 2000000;
#debug concat(”N = “,str(N, 0,50),”\n”)
#debug concat(”N-5 = “,str(N-5,0,50),”\n\n”)
#for (I, N-5, N, 1)
#debug concat("I = ",str(I,0,50),"\n")
#end
(The limit was observed with a Win64 build; other builds may exhibit other limits or might even work fine, depending on the floating point engine used.)
As this limit is still far below the numeric precision limit, and a corresponding #while loop works fine with much higher values, this must be considered a bug rather than an inevitable limitation.
The bug can be tracked down to a faulty condition in tokenize.cpp, Parser::Parse_Directive(), CASE(END_TOKEN), case FOR_COND:
if ( ((Step > 0) && (*CurrentPtr >= End + EPSILON)) ||
((Step < 0) && (*CurrentPtr <= End - EPSILON)) )
which should instead be:
if ( ((Step > 0) && (*CurrentPtr > End + EPSILON)) ||
((Step < 0) && (*CurrentPtr < End - EPSILON)) )
Saturday, 10 December 2016, 15:14 GMT
Reason for closing: Fixed
Additional comments about closing:
Tests of 3.7 RC7, 3.7.0 and 3.7.1 show
the fix in 3.7.0 onward.
fixed with change #6008