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Topic: Converting a 40-bit to a 64-bit float? (Read 186 times) |
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David Williams
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meh
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Re: Converting a 40-bit to a 64-bit float?
« Reply #5 on: Aug 14th, 2014, 2:16pm » |
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on Aug 14th, 2014, 11:55am, Richard Russell wrote:| -masm=intel compiler switch. |
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I had used that switch in conjunction with the -S switch (for outputting an assembly language listing), but I hadn't realised that it affected the inline assembler. Maybe it was obvious, but I'm learning. :)
Quote:| I still haven't quite grasped why you have to. |
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Mostly personal preference, admittedly. It's for a routine called gPlotPoints (familiar from GFXLIB), where one supplies pointers to a list of X coordinates and to a list of Y coordinates (haven't fully figured out structure array handling and pointers in C yet -- it's early days).
This demo linked-to below shows what gPlotPoints does (it's nothing that you and most others here haven't seen before):
http://www.bb4wgames.com/temp/gplotpointsdemo.zip
Includes two versions - fixed-point (fxp) and 64-bit double (dbl). The source listing (for inspection by the curious) is included below. You can see why your wrapper idea (for converting 40- to 64-bit floats) isn't really suitable in this case as it would be far too slow. As it happens, I'm getting 60 fps for 3000 points on my slow-ish laptop, both for fixed-point and 64-bit double 'mode'. Not bad considering it's BB4W that's updating the coordinates.
David.
--
Code:
REM Example of using gPlotPoints to plot multiple points.
REM This uses fixed-point coordinates format.
REM 3000 points at 60 fps on my 1.66GHz 64-bit Intel Celeron
*ESC OFF
MODE 8 : OFF
ON ERROR REPORT : PRINT " at line "; ERL : END
INSTALL @lib$ + "GLIB2"
PROCInitGLIB( @lib$ + "glib2.dll", g{} )
ON ERROR PROCCleanup : PROCerror
ON CLOSE PROCCleanup : QUIT
GetTickCount% = FN`s("GetTickCount")
REM FN`s() is one of GLIB's internal functions,
REM but nevertheless comes in handy for our purposes!
clr% = FNImport("gLerpClr")
plot% = FNImport("gPlotPoints")
nPts% = 3000
DIM x%( nPts%-1 ), y%( nPts%-1 )
DIM dx%( nPts%-1 ), dy%( nPts%-1 )
DIM col%( nPts%-1 )
FOR I% = 0 TO nPts%-1
x%( I% ) = 640*RND(1) * 2^16
y%( I% ) = 512*RND(1) * 2^16
dx%( I% ) = 4*(RND(1)-0.5) * 2^16
dy%( I% ) = 4*(RND(1)-0.5) * 2^16
col%( I% ) = RND(&FFFFFF)
NEXT I%
maxX% = 640 * 2^16
maxY% = 512 * 2^16
fmt% = 2 : REM coordinates format (fixed-point)
REM 0 = integer
REM 1 = <reserved>
REM 2 = 16:16 fixed-point
REM 3 = 40-bit float (not yet supported)
REM 4 = 64-bit float
frames% = 0
*REFRESH OFF
SYS GetTickCount% TO time0%
REPEAT
SYS clr%, g{}, &803020, &203040
SYS plot%, g{}, fmt%, ^x%(0), ^y%(0), ^col%(0), nPts%
FOR I%=0 TO nPts%-1
x%(I%)+=dx%(I%)
y%(I%)+=dy%(I%)
IF x%(I%)<0 OR x%(I%)>=maxX% dx%(I%)*=-1
IF y%(I%)<0 OR y%(I%)>=maxY% dy%(I%)*=-1
NEXT
PROCDisplay(TRUE)
frames% += 1
SYS GetTickCount% TO time1%
IF time1%-time0%>=1000 THEN
SYS GetTickCount% TO time0%
SYS "SetWindowText", @hwnd%, STR$nPts%+" points | " + STR$frames% + " fps"
frames% = 0
ENDIF
UNTIL FALSE
PROCCleanup
END
DEF PROCerror
*REFRESH ON
CLS : ON : REPORT : PRINT " at line "; ERL;
REPEAT UNTIL INKEY(1)=0
ENDPROC
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rtr
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Re: Converting a 40-bit to a 64-bit float?
« Reply #6 on: Aug 14th, 2014, 3:49pm » |
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on Aug 14th, 2014, 2:16pm, David Williams wrote:| It's for a routine called gPlotPoints (familiar from GFXLIB), where one supplies pointers to a list of X coordinates and to a list of Y coordinates |
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So, just specify that the user of the library must declare those arrays/lists either with a % suffix (for the integer version) or a # suffix (for the float version). There is no need to support 40-bit or 80-bit variants, it just adds complication and slows things down (even if the conversion is done in machine code).
I implore you not to release a library which supports only BB4W v5.
Richard.
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