/*"Fixed point" means you use ints
that are scaled by a value.A common
example would be using number of pennies
instead of dollars with a float.
Fixed-point used to be much $TX,"faster",HTML="http://en.wikipedia.org/wiki/X87"$,
but modern processors do well with
floats.It also depends on the compiler
and my compiler is poor with floats.
I often use 64-bit ints with upper 32-bits
as int and lower 32-bits as fraction.
See /Demo/SubIntAccess.HC for how
to access upper or lower 32-bits.
*/
#define SAMPLE_SIZE 10000000
I32 coordinates[65536];
asm {
_ASM_FIXED_POINT::
PUSH RBP
MOV RBP,RSP
PUSH RSI
PUSH RDI
MOV RSI,coordinates
MOV RDI,ToI64(Sin(1.0)*0x100000000)
XOR RBX,RBX //SUM
MOV RCX,SAMPLE_SIZE-1
@@05: XOR RDX,RDX
MOV DX,CX
MOVSXD RAX,U32 [RSI+RDX*4]
IMUL RDI
SAR RAX,32
ADD RBX,RAX
DEC RCX
JGE @@05
MOV RAX,RBX
POP RDI
POP RSI
POP RBP
RET
SINE_VAL: DU64 Sin(1.0);
RET_VAL: DU64 0;
_ASM_FLOAT::
PUSH RBP
MOV RBP,RSP
PUSH RSI
MOV RSI,coordinates
FLD U64 [SINE_VAL]
FLDZ
MOV RCX,SAMPLE_SIZE-1
@@05: XOR RDX,RDX
MOV DX,CX
FILD U32 [RSI+RDX*4]
FMUL ST0,ST2
FADDP ST1,ST0
DEC RCX
JGE @@05
FISTP U64 [RET_VAL]
MOV RAX,U64 [RET_VAL]
FFREE ST0
FINCSTP
POP RSI
POP RBP
RET
}
_extern _ASM_FIXED_POINT I64 AsmFixedPt();
_extern _ASM_FLOAT I64 AsmFloat();
U0 Main()
{
I64 start,end,overhead_time,test_time;
F64 d1,fsum;
I64 reg i,tmp,reg d2,reg sum;
CPURep;
//Set-up some sample coordinates
for (i=0;i<65536;i++)
coordinates[i]=RandU32;
//Measure Loop Overhead
start=GetTSC;
for (i=SAMPLE_SIZE-1;i>=0;i--) {
}
end=GetTSC;
overhead_time=end-start;
"$RED$Overhead Cycles:%10.5f$FG$\n",
ToF64(overhead_time)/SAMPLE_SIZE;
//Measure F64 arithmetic
// (Some of this is due to crappy
// compiler code.)
d1=Sin(1.0);
fsum=0;
start=GetTSC;
for (i=SAMPLE_SIZE-1;i>=0;i--)
fsum+=d1*coordinates[i&65535];
end=GetTSC;
test_time=end-start;
"Float Sum:%X\n",ToI64(fsum);
"$RED$Float Cycles:%10.5f$FG$\n",
ToF64(test_time)/SAMPLE_SIZE;
//Measure fixed point arithmetic
d2=Sin(1.0)*0x100000000;
sum=0;
start=GetTSC;
for (i=SAMPLE_SIZE-1;i>=0;i--) {
tmp=d2*coordinates[i&65535];
sum+=tmp.i32[1];
}
end=GetTSC;
test_time=end-start;
"Fixed-Point Sum:%X\n",sum;
"$RED$Fixed-Point Cycles:%10.5f$FG$\n",
ToF64(test_time)/SAMPLE_SIZE;
//Measure fixed point arithmetic
start=GetTSC;
sum=AsmFixedPt;
end=GetTSC;
test_time=end-start;
"Asm Fixed-Point Sum:%X\n",sum;
"$RED$Asm Fixed-Point Cycles:%10.5f$FG$\n",
ToF64(test_time)/SAMPLE_SIZE;
//Measure float arithmetic
start=GetTSC;
sum=AsmFloat;
end=GetTSC;
test_time=end-start;
"Asm Float Sum:%X\n",sum;
"$RED$Asm Float Cycles:%10.5f$FG$\n",
ToF64(test_time)/SAMPLE_SIZE;
}
Main;
/* Program Output$HL,0$WW+H,1$FD,1$
Machine 1:
8 Cores 2.660GHz
Overhead Cycles:2.00814
Float Sum:FFFFE1D361BEED68
Float Cycles:10.16076
Fixed-Point Sum:FFFFE1D361729914
Fixed-Point Cycles:5.29392
Asm Fixed-Point Sum:FFFFE1D361729914
Asm Fixed-Point Cycles:4.20464
Asm Float Sum:FFFFE1D361BEED56
Asm Float Cycles:3.04635
Machine 2:
8 Cores 3.395GHz
Overhead Cycles:4.87040
Float Sum:D20A01DB177
Float Cycles:10.11558
Fixed-Point Sum:D209FD18CC7
Fixed-Point Cycles:4.50618
Asm Fixed-Point Sum:D209FD18CC7
Asm Fixed-Point Cycles:3.02426
Asm Float Sum:D20A01DB17B
Asm Float Cycles:3.21070
$HL,1$*/