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From: ConradL on 18 Jan 2008 00:25
Hi all,

I have written a function that scales a 1-D array of data with a given
double precision value:

a^[i] = a^[i]*dblScaleValue

I have written the code in Delphi assembler as follows:

asm
mov ecx, intNumberOfElements;
mov esi, pArray
finit
fld dblValue // load scalevalue st(1)
@next:
fld qword ptr [esi] // load pArray st(0)
fmul st(0), st(1) // multiply by scale value
fstp qword ptr [esi]
add esi,8
loop @next
fwait
end;

where intNumberOfElements is an even number of elements
pArray is a pointer to the data

When the code is executed the first time, it works correctly but if i
execute the code two consecutive times the data is filled with NANs.
Could some1 explain what i am doing wrong?

Regards
Conrad
From: Dirk Wolfgang Glomp on 18 Jan 2008 04:55
Am Thu, 17 Jan 2008 21:25:03 -0800 (PST) schrieb ConradL:

> Hi all,
>
> I have written a function that scales a 1-D array of data with a given
> double precision value:
>
> a^[i] = a^[i]*dblScaleValue
>
> I have written the code in Delphi assembler as follows:
>
> asm
> mov ecx, intNumberOfElements;
> mov esi, pArray
> finit
> fld dblValue // load scalevalue st(1)
> @next:
> fld qword ptr [esi] // load pArray st(0)
> fmul st(0), st(1) // multiply by scale value
> fstp qword ptr [esi]
> add esi,8
> loop @next
> fwait
> end;
>
> where intNumberOfElements is an even number of elements
> pArray is a pointer to the data
>
> When the code is executed the first time, it works correctly but if i
> execute the code two consecutive times the data is filled with NANs.
> Could some1 explain what i am doing wrong?

The last pop is missing to clear the stack?

Dirk
From: Wolfgang Kern on 19 Jan 2008 06:49

Conrad asked:

> Hi all,
>
> I have written a function that scales a 1-D array of data with a given
> double precision value:
>
> a^[i] = a^[i]*dblScaleValue
>
> I have written the code in Delphi assembler as follows:
>
> asm
> mov ecx, intNumberOfElements;
> mov esi, pArray
> finit
> fld dblValue // load scalevalue st(1)
> @next:
> fld qword ptr [esi] // load pArray st(0)
> fmul st(0), st(1) // multiply by scale value
> fstp qword ptr [esi]
> add esi,8
> loop @next
> fwait
> end;
>
> where intNumberOfElements is an even number of elements
> pArray is a pointer to the data
>
> When the code is executed the first time, it works correctly but if i
> execute the code two consecutive times the data is filled with NANs.
> Could some1 explain what i am doing wrong?

perhaps because source and destination are identical, so the FMUL's
(always a 'tword' action) exponent result can't fit the DBL in fstp ?
I'd check on possible ranges and limits.
__
wolfgang



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