Re: Casting of Floating Point Data Types to Ints

[N8TM at aol dot com]

>>casting a floating
point value to integers 
>>casting on x86 platforms
causes the processor to stall
>>if inline assembly is used to correct the problem, for a large 2D3V
electrostatic PIC simulation, the simulation performance increases
roughly 100%

The same can be said for the Livermore Fortran Kernel 13 and 14 benchmarks.  
Incidentally, the results in Kernel 14 don't vary with rounding mode, as I 
have verified both by editing the gcc/g77 .s code and by changing the Fortran 
source to use NINT() with the MipsPro compiler's -OPT:fast_nint=ON.  That 
option permits the slight variation from standard Fortran implied by the IEEE 
rounding nearest even.

As your later quotation shows, Intel has always been aware that their 
processor design did not allow efficient implementation of standard C and 
Fortran rounding.  C9X defines some intrinsics which deal with this problem 
and are already present in glibc.  Why not use those?  Unfortunately, with 
the x86, if you want efficiency, it seems you must assume that there will be 
no outside tinkering with the rounding mode.

Tim Prince
tprince@computer.org