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Sqr() vs. Self made ASM Squareroot

Another snipper which I received from Alex Spurling. This code calculates the approximate squareroot of the given value (single) Simply call the function like:

intSQR = 3
Call fastSqr(intSQR)

Public Sub fastSqr(ByRef num As Single) '//By Alex Spurling - Thanks! '#ASM_START ' push ebp ' mov ebp, esp ' push edi ' ' mov edi, DWORD PTR [ebp+8] ' mov eax, [edi] ' add eax, 3F800000h ' shr eax, 1 ' mov [edi], eax ' ' pop edi ' mov esp, ebp ' pop ebp ' ret 4 End Sub

VBSQR % faster than ASMApprox	VBSQR (sec)	ASMApprox (sec)
78.7%	0.000584	0.000327
77%	0.000582	0.000329
77%	0.00058	0.000328
274.7%	0.001219	0.000325
80.9%	0.000588	0.000325

VBSQR % faster than ASMApprox	VBSQR (sec)	ASMApprox (sec)
85.7%	0.001204	0.000649
82%	0.001181	0.000649
85%	0.0012	0.000649
85%	0.0012	0.000649
86.1%	0.001201	0.000645

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User contributed notes:

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