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vnorm_c

 Procedure Abstract Required_Reading Keywords Brief_I/O Detailed_Input Detailed_Output Parameters Exceptions Files Particulars Examples Restrictions Literature_References Author_and_Institution Version Index_Entries

#### Procedure

```   vnorm_c ( Vector norm, 3 dimensions )

SpiceDouble vnorm_c ( ConstSpiceDouble v1[3] )

```

#### Abstract

```   Compute the magnitude of a double precision 3-dimensional
vector.
```

```   None.
```

#### Keywords

```   VECTOR

```

#### Brief_I/O

```   VARIABLE  I/O  DESCRIPTION
--------  ---  --------------------------------------------------
v1         I   Vector whose magnitude is to be found.

The function returns the magnitude of `v1'.
```

#### Detailed_Input

```   v1          is any double precision 3-dimensional vector.
```

#### Detailed_Output

```   The function returns the magnitude of `v1' calculated in a
numerically stable way.
```

#### Parameters

```   None.
```

#### Exceptions

```   Error free.
```

#### Files

```   None.
```

#### Particulars

```   vnorm_c takes care to avoid overflow while computing the norm of the
input vector `v1'. vnorm_c finds the component of `v1' whose magnitude
is the largest. Calling this magnitude `v1max', the norm is computed
using the formula:

||    1         ||
vnorm_c = v1max * || ------- * v1 ||
||  v1max       ||

where the notation ||x|| indicates the norm of the vector `x'.
```

#### Examples

```   The numerical results shown for this example may differ across
platforms. The results depend on the SPICE kernels used as
input, the compiler and supporting libraries, and the machine
specific arithmetic implementation.

1) Define a set of 3-dimensional vectors and compute the
magnitude of each vector within.

Example code begins here.

/.
Program vnorm_ex1
./
#include <stdio.h>
#include "SpiceUsr.h"

int main( )
{

/.
Local parameters.
./
#define SETSIZ       3

/.
Local variables.
./
SpiceInt             i;

/.
Define a set of 3-dimensional vectors.
./
SpiceDouble          v1     [SETSIZ][3] = {
{ 1.0,    2.0,  2.0   },
{ 5.0,   12.0,  0.0   },
{-5.e-17, 0.0, 12.e-17}  };

/.
Calculate the magnitude of each vector
./
for ( i = 0; i < SETSIZ; i++ )
{

printf( "Input vector:  %9.2e %9.2e %9.2e\n",
v1[i][0], v1[i][1], v1[i][2] );
printf( "Magnitude   :  %23.20f\n", vnorm_c ( v1[i] ) );
printf( "\n" );

}

return ( 0 );
}

When this program was executed on a Mac/Intel/cc/64-bit
platform, the output was:

Input vector:   1.00e+00  2.00e+00  2.00e+00
Magnitude   :   3.00000000000000000000

Input vector:   5.00e+00  1.20e+01  0.00e+00
Magnitude   :  13.00000000000000000000

Input vector:  -5.00e-17  0.00e+00  1.20e-16
Magnitude   :   0.00000000000000013000
```

#### Restrictions

```   None.
```

#### Literature_References

```   None.
```

#### Author_and_Institution

```   N.J. Bachman        (JPL)
J. Diaz del Rio     (ODC Space)
W.M. Owen           (JPL)
W.L. Taber          (JPL)
E.D. Wright         (JPL)
```

#### Version

```   -CSPICE Version 1.0.3, 05-JUL-2021 (JDR)

code example based on existing example.

-CSPICE Version 1.0.2, 16-JAN-2008 (EDW)

Detailed Input to -Detailed_Input
Detailed Output to -Detailed_Output

-CSPICE Version 1.0.1, 12-NOV-2006 (EDW)

```   norm of 3-dimensional vector
`Fri Dec 31 18:41:15 2021`