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;
}

[Irrwahn Grausewitz]

Re: TAking the minimum of three values

[cross-posting to c.l.c++ fixed]

Steve Zimmerman <stevetux@sonic .net> wrote:[color=blue]
>Sona wrote:[color=green]
>> I need to find a minimum of three float values [...][/color][/color]
<SNIP>

Why not make use of the standard C library?
Code modified:

#include <stdio.h>
#include <math.h> /* for fminf() */

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

printf("Enter three float values, separated by spaces: ");
scanf("%f%f%f", &a, &b, &c);
printf("The minimum is: %f\n", fminf(a, fminf(b, c)) );

return 0;
}

<SNIP>

--
Close your eyes and press escape three times.

[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

[Jirka Klaue]

Re: TAking the minimum of three values

Irrwahn Grausewitz wrote:[color=blue]
> Steve Zimmerman <stevetux@sonic .net> wrote:[color=green]
>>Sona wrote:
>>[color=darkred]
>>>I need to find a minimum of three float values [...][/color][/color]
>
> Why not make use of the standard C library?
> Code modified:
>
> #include <stdio.h>
> #include <math.h> /* for fminf() */[/color]

Is this in C89, too? If not, the standard C library provides qsort.
It is not *that* efficient for 3 values, but in return it's scalable.


#include <stdio.h>
#include <stdlib.h>

static int cmp(const void *a, const void *b)
{
return *(float *)a < *(float *)b ? -1 : 1; /* Is 0 really required? */
}

int main( void )
{
float v[] = {2.3, 2.4, 2.299};

qsort(v, sizeof v / sizeof *v, sizeof *v, cmp);
printf("The minimum is: %f\n", *v);

return 0;
}

Jirka

[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

[Irrwahn Grausewitz]

Re: TAking the minimum of three values

"Carsten Hansen" <hansen.c@world net.att.net> wrote:[color=blue]
>
>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)))
>[/color]

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

[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