[GRASS-dev] [GRASS GIS] #1421: scalability of r.terraflow

[GRASS GIS]

#1421: scalability of r.terraflow
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 Reporter:  dnewcomb                  |       Owner:  grass-dev@…              
     Type:  enhancement               |      Status:  new                      
 Priority:  normal                    |   Milestone:  7.0.0                    
Component:  Raster                    |     Version:  svn-develbranch6         
 Keywords:  r.terraflow, large grids  |    Platform:  Linux                    
      Cpu:  x86-64                    |  
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Comment(by glynn):

 Replying to [comment:4 dnewcomb]:

 > The thing that confuses me at the moment is the FILL line below in the
 temp file  listing below. Why are there a large negative number of
 elements?

 r.terraflow/main.cpp:410:
 {{{
   G_message( "\t\t FILL: %s [%d elements, %dB each]",
                   formatNumber(buf, fillmaxsize),
                   nrows * ncols, sizeof(waterWindowType));
   G_message( "\t\t FLOW: %s [%ld elements, %dB each]",
                   formatNumber(buf, flowmaxsize),
                   (long)(nrows * ncols - nodata_count),
 sizeof(sweepItem));
 }}}

 Even if dimension_type is changed to "long", the value is still being
 formatted as an "int" ("%d" conversion specifier).

 Also, the cast to "long" in the second call is wrong. If nrows and ncols
 are of type "int" (or any smaller type, e.g. "short"), the multiplication
 will be performed as "int", which may overflow; casting the (possibly
 overflowed) result to "long" won't change that.

 It should be:

 {{{
   G_message( "\t\t FLOW: %s [%ld elements, %dB each]",
                   formatNumber(buf, flowmaxsize),
                   (long)nrows * ncols - nodata_count, sizeof(sweepItem));
 }}}

 Casting either of the operands to "long" will force the multiplication to
 be performed as "long" and yield a "long" result (however, note that
 "long" is still only 32 bits on 64-bit versions of Windows).

-- 
Ticket URL: <https://trac.osgeo.org/grass/ticket/1421#comment:5>
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