TAking the minimum of three values

[Sona]

I need to find a minimum of three float values.. what would be the most
efficient way of doing this? Can someone please share a #define macro or
something with me for doing this? Thanks

Sona

[Howard]

Re: TAking the minimum of three values


"Sona" <sona.gardner@n ospam.com> wrote in message
news:3f5e1b20$1 @clarion.carno. net.au...[color=blue]
> I need to find a minimum of three float values.. what would be the most
> efficient way of doing this? Can someone please share a #define macro or
> something with me for doing this? Thanks
>
> Sona
>[/color]

x = min( a, min( b, c ) );

-Howard

[Ron Natalie]

Re: TAking the minimum of three values

Sona wrote:[color=blue]
> I need to find a minimum of three float values.. what would be the most
> efficient way of doing this? Can someone please share a #define macro or
> something with me for doing this? Thanks
>[/color]

In C++

#include <algoritm>

double min3(double a, double b, double c) {
return std::min(a, std::min(b, c));
}

[Vincent Lascaux]

Re: TAking the minimum of three values

> #include <algoritm>[color=blue]
>
> double min3(double a, double b, double c) {
> return std::min(a, std::min(b, c));
> }[/color]

To keep the templated aspect of min, you could even write

namespace
{
template<class T>
T& min(T const& a, T const& b, T const& c)
{
return min(a, min(b,c));
}
}

Like that std::min works with any type, and with 2 or 3 arguments

[Steve Zimmerman]

Re: TAking the minimum of three values

Sona wrote:
[color=blue]
> I need to find a minimum of three float values.. what would be the most
> efficient way of doing this? Can someone please share a #define macro or
> something with me for doing this? Thanks
>
> Sona
>[/color]

Sona,

Thank you for your post.

--Steve

#include <stdio.h>

float min(float h, float j);

int main()
{
float a, b, c;

printf("Enter three float values, separated by spaces: ");
scanf("%f%f%f", &a, &b, &c);
/*
* NOTE: I had to round the floats off to two decimal places
* in the following printf statement, because I was getting
* weird errors otherwise.
*/
printf("The minimum of these three is %.2f\n", min(a, min(b, c)));

return 0;
}

float min(float h, float j)
{
if (h < j)
return h;
else
return j;
}

[Peter Nilsson]

Re: TAking the minimum of three values

"Howard" <alicebt@hotmai l.com> wrote in message news:<bjl7cq$rl f@dispatch.conc entric.net>...[color=blue]
> "Sona" <sona.gardner@n ospam.com> wrote in message
> news:3f5e1b20$1 @clarion.carno. net.au...[color=green]
> > I need to find a minimum of three float values.. what would be the most
> > efficient way of doing this? Can someone please share a #define macro or
> > something with me for doing this? Thanks
> >
> > Sona[/color]
>
> x = min( a, min( b, c ) );[/color]

Given a typical definition of min(), that will not produce an efficient result.

#define min3(a,b,c) \
( (a) < (b) ? min(a,c) : min(b,c) )

--
Peter

[Martin Ambuhl]

Re: TAking the minimum of three values

Peter Nilsson wrote:
[color=blue]
> "Howard" <alicebt@hotmai l.com> wrote in message news:<bjl7cq$rl f@dispatch.conc entric.net>...[/color]
[color=blue][color=green]
>>x = min( a, min( b, c ) );[/color]
>
>
> Given a typical definition of min(), that will not produce an efficient result.
>
> #define min3(a,b,c) \
> ( (a) < (b) ? min(a,c) : min(b,c) )[/color]

Have you counted the number of evaluations of a or b this involves? There
is a good reason for preferring functions over defines.


--
Martin Ambuhl

[Irrwahn Grausewitz]

Re: TAking the minimum of three values

Martin Ambuhl <mambuhl@earthl ink.net> wrote:[color=blue]
>Peter Nilsson wrote:[color=green]
>>
>> #define min3(a,b,c) \
>> ( (a) < (b) ? min(a,c) : min(b,c) )[/color]
>
>Have you counted the number of evaluations of a or b this involves? There
>is a good reason for preferring functions over defines.[/color]

Not to mention possible side effects; consider:

float m3, x, y, z;
m3 = min3( x *= 3.142, y /= 2.718, z += 1.111 );


Irrwahn
--
Computer: a million morons working at the speed of light.

[Carsten Hansen]

Re: TAking the minimum of three values


"Sona" <sona.gardner@n ospam.com> wrote in message
news:3f5e1b20$1 @clarion.carno. net.au...[color=blue]
> I need to find a minimum of three float values.. what would be the most
> efficient way of doing this? Can someone please share a #define macro or
> something with me for doing this? Thanks
>
> Sona
>[/color]

You want a macro. Here you go:
#define min3(x, y, z) \
((x) < (y)) ? (((y) < (z)) ? (y) : (((x) < (z)) ? (z) : (x))) : (((x) < (z))
? (x) : (((y) < (z)) ? (z) : (y)))

You can't beat that for efficiency. Of course it is totally unreadable. But
you asked for it :-)

Carsten Hansen

[Jirka Klaue]

Re: TAking the minimum of three values

Carsten Hansen wrote:[color=blue]
> "Sona" <sona.gardner@n ospam.com> wrote in message
> news:3f5e1b20$1 @clarion.carno. net.au...
>[color=green]
>>I need to find a minimum of three float values.. what would be the most
>>efficient way of doing this? Can someone please share a #define macro or
>>something with me for doing this? Thanks[/color]
>
> You want a macro. Here you go:
> #define min3(x, y, z) \
> ((x) < (y)) ? (((y) < (z)) ? (y) : (((x) < (z)) ? (z) : (x))) : (((x) < (z))
> ? (x) : (((y) < (z)) ? (z) : (y)))
>
> You can't beat that for efficiency.[/color]

It is not even correct.

float min3(float x, float y, float z)
{
if (x < y)
if (x < z) return x;
if (y < z) return y;
return z;
}

Jirka

[Carsten Hansen]

Re: TAking the minimum of three values


"Jirka Klaue" <jklaue@ee.tu-berlin.de> wrote in message
news:bjlui2$b09 $1@mamenchi.zrz .TU-Berlin.DE...[color=blue]
> Carsten Hansen wrote:[color=green]
> > "Sona" <sona.gardner@n ospam.com> wrote in message
> > news:3f5e1b20$1 @clarion.carno. net.au...
> >[color=darkred]
> >>I need to find a minimum of three float values.. what would be the most
> >>efficient way of doing this? Can someone please share a #define macro or
> >>something with me for doing this? Thanks[/color]
> >
> > You want a macro. Here you go:
> > #define min3(x, y, z) \
> > ((x) < (y)) ? (((y) < (z)) ? (y) : (((x) < (z)) ? (z) : (x))) : (((x) <[/color][/color]
(z))[color=blue][color=green]
> > ? (x) : (((y) < (z)) ? (z) : (y)))
> >
> > You can't beat that for efficiency.[/color]
>
> It is not even correct.
>
> float min3(float x, float y, float z)
> {
> if (x < y)
> if (x < z) return x;
> if (y < z) return y;
> return z;
> }
>
> Jirka
>[/color]

Give an example where it fails.

Carsten Hansen

[Jeff]

Re: TAking the minimum of three values


"Ron Natalie" <ron@sensor.com > wrote in message
news:3f5e256a$0 $46555$9a6e19ea @news.newshosti ng.com...[color=blue]
> Sona wrote:[color=green]
> > I need to find a minimum of three float values.. what would be the most
> > efficient way of doing this? Can someone please share a #define macro or
> > something with me for doing this? Thanks
> >[/color]
>
> In C++
>
> #include <algoritm>
>
> double min3(double a, double b, double c) {
> return std::min(a, std::min(b, c));
> }
>
>[/color]


Please do not post off-topic things here. It waste the bandwidth and time.

--
Jeff

[Irrwahn Grausewitz]

Re: TAking the minimum of three values

"Jeff" <nothing@notexi st.com> wrote:[color=blue]
>
>"Ron Natalie" <ron@sensor.com > wrote in message
>news:3f5e256a$ 0$46555$9a6e19e a@news.newshost ing.com...[color=green]
>> In C++
>>
>> #include <algoritm>
>>
>> double min3(double a, double b, double c) {
>> return std::min(a, std::min(b, c));
>> }[/color]
>
>
>Please do not post off-topic things here. It waste the bandwidth and time.[/color]

Erm, (almost) the whole thread is cross-posted between c.l.c and c.l.c++


--
Computer: a million morons working at the speed of light.

[Jirka Klaue]

Re: TAking the minimum of three values

Carsten Hansen wrote:[color=blue]
>"Jirka Klaue" wrote:[color=green]
>>Carsten Hansen wrote:[color=darkred]
>>>"Sona" wrote:
>>>
>>>>I need to find a minimum of three float values.. what would be the most
>>>>efficient way of doing this? Can someone please share a #define macro or
>>>>something with me for doing this? Thanks
>>>
>>>You want a macro. Here you go:
>>>#define min3(x, y, z) \
>>>((x) < (y)) ? (((y) < (z)) ? (y) : (((x) < (z)) ? (z) : (x))) : (((x) <[/color][/color]
>
> (z))
>[color=green][color=darkred]
>>>? (x) : (((y) < (z)) ? (z) : (y)))
>>>
>>>You can't beat that for efficiency.[/color]
>>
>>It is not even correct.[/color]
>
> Give an example where it fails.[/color]

#include <stdio.h>

#define MIN3(x, y, z) \
((x) < (y)) ? (((y) < (z)) ? (y) : (((x) < (z)) ? (z) : (x))) : (((x) < (z)) ? (x) : (((y) < (z)) ? (z) : (y)))

int main(void)
{
float a = 1.6, b = 1.7, c = 1.8;
printf("%f\n", MIN3(a, b, c));

a = 1.9, b = 1.7, c = 1.8;
printf("%f\n", MIN3(a, b, c));

a = 1.6, b = 1.7, c = 1.5;
printf("%f\n", MIN3(a, b, c));

return 0;
}

1.700000
1.800000
1.600000

Now, give an example where it works.
And even when you fix it, it probably is not the most efficient method.

Jirka

[Steve Zimmerman]

Re: TAking the minimum of three values

Carsten Hansen wrote:
[color=blue]
> "Jirka Klaue" <jklaue@ee.tu-berlin.de> wrote in message
> news:bjlui2$b09 $1@mamenchi.zrz .TU-Berlin.DE...
>[color=green]
>>Carsten Hansen wrote:
>>[color=darkred]
>>>"Sona" <sona.gardner@n ospam.com> wrote in message
>>>news:3f5e1b2 0$1@clarion.car no.net.au...
>>>
>>>
>>>>I need to find a minimum of three float values.. what would be the most
>>>>efficient way of doing this? Can someone please share a #define macro or
>>>>something with me for doing this? Thanks
>>>>
>>>You want a macro. Here you go:
>>>#define min3(x, y, z) \
>>>((x) < (y)) ? (((y) < (z)) ? (y) : (((x) < (z)) ? (z) : (x))) : (((x) <
>>>[/color][/color]
> (z))
>[color=green][color=darkred]
>>>? (x) : (((y) < (z)) ? (z) : (y)))
>>>
>>>You can't beat that for efficiency.
>>>[/color]
>>It is not even correct.
>>
>>float min3(float x, float y, float z)
>>{
>> if (x < y)
>> if (x < z) return x;
>> if (y < z) return y;
>> return z;
>>}
>>
>>Jirka
>>
>>[/color]
>
> Give an example where it fails.
>
> Carsten Hansen[/color]

Carsten,


Thank you for your post.

I don't intend this post as mean-spirited; I cannot write such
a macro.


#include <stdio.h>

#define min3(x, y, z) \
((x) < (y)) ? (((y) < (z)) ? (y) : (((x) < (z)) ? (z) : (x))) : \
(((x) < (z)) ? (x) : (((y) < (z)) ? (z) : (y)))

int main()
{
float x, y, z;

printf("Enter three float values, separated by spaces: ");
scanf("%f%f%f", &x, &y, &z);

printf("The least of these is %f\n", min3(x, y, z));

return 0;
}

Input from keyboard: 12345 44444 55555
Output to screen: The least of these is 44444