Tuesday, September 6, 2022

Digest for comp.lang.c++@googlegroups.com - 3 updates in 2 topics

Bonita Montero <Bonita.Montero@gmail.com>: Sep 06 07:08PM +0200

I've written my own pow( double, int ) and it's about
10% slower than that of MSVCRT. Where's the mistake ?
 
double powPow( double d, int e )
{
unsigned eAbs = e >= 0 ? e : -e;
double v = 1.0, sq = d;
for( ; eAbs; eAbs >>= 1, sq *= sq )
if( eAbs & 1 )
v *= sq;
return e >= 0 ? v : 1.0 / v;
}
Lynn McGuire <lynnmcguire5@gmail.com>: Sep 06 01:49PM -0500

On 9/6/2022 12:08 PM, Bonita Montero wrote:
>             v *= sq;
>     return e >= 0 ? v : 1.0 / v;
> }
 
You need to unroll the loop for the common cases of e == 1, e == 2, e ==
3, etc.
 
Lynn
olcott <polcott2@gmail.com>: Sep 06 12:56PM -0500

void Px(ptr x)
{
int Halt_Status = Hx(x, x);
if (Halt_Status)
HERE: goto HERE;
return;
}
 
int main()
{
Output("Input_Halts = ", Hx(Px, Px));
}
 
*THIS HAS BEEN AGREED TO* // *understanding the above code proves this*
There are zero elements of infinite set of Hx/Px pairs such that the
correct *partial or complete* simulation of Px by Hx reaches the final
state of Px.
 
*THIS LOGICALLY FOLLOWS (as a subset) FROM ABOVE*
(A) Every element of the infinite set of Hx/Px pairs that does a correct
and complete simulation of its input never reaches the final state of
this input.
 
*THIS IS THE DEFINITION OF A UTM THUS KNOWN TO BE TRUE*
(B) A correct and complete simulation of this input derives the actual
behavior of this input.
 
*THIS LOGICALLY FOLLOWS FROM (A) AND (B) PREMISES*
(C) The actual behavior of this input never reaches the final state of
this input.
 
When the criteria for a simulating halt decider (SHD) is to correctly
predict that its complete and correct simulation of its input would
never reach the final state of this simulated input then:
 
void Infinite_Loop()
{
HERE: goto HERE;
}
 
*H0(Infinite_Loop)==0 // is correct*
 
 
void Infinite_Recursion(int N)
{
Infinite_Recursion(N);
}
 
*H(Infinite_Recursion, 0x777)==0 // is correct*
 
 
*Hx(Px,Px)==0 // is correct*
 
 
 
*Halting problem proofs refuted on the basis of software engineering* ?
https://www.researchgate.net/publication/361701808_Halting_problem_proofs_refuted_on_the_basis_of_software_engineering
 
 
--
Copyright 2022 Pete Olcott "Talent hits a target no one else can hit;
Genius hits a target no one else can see." Arthur Schopenhauer
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