From: anton@mips.complang.tuwien.ac.at   
      
   anton@mips.complang.tuwien.ac.at (Anton Ertl) writes:   
   >But I decided to use a recursive approach (recursive-sum, REC) that   
   >uses the largest 2^kchild, and as base cases for the recursion use a straight-line   
   >balanced-tree evaluation for 2^k with k<=7 (and combine these for n   
   >that are not 2^k).  For systems with tiny FP stacks, I added the   
   >option to save intermediate results on a software stack in the   
   >recursive word.  Concerning the straight-line code, it turned out that   
   >the highest k I could use on sf64 and vfx64 is 5 (corresponding to 6   
   >FP stack items); it's not clear to me why; on lxf I can use k=7 (and   
   >it uses the 387 stack, too).   
      
   Actually, after writing that, I found out the reasons for the FP stack   
   overflows, and in the published versions and the results I use k=7 on   
   all systems.  It's really easy to leave an FP stack item on the FP   
   stack while calling another word, and that's not so good if you do it   
   while calling sum128:-).   
      
   - anton   
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   M. Anton Ertl  http://www.complang.tuwien.ac.at/anton/home.html   
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