weight-gen(1) General Commands Manual weight-gen(1)

weight-gen - Generate a distribution of weights for a given mesh

weight-gen [options...] [input.mesh [output.weights]]

weight-gen generates weights for a given mesh.

If input.mesh is omitted or is -, it is read from standard input. If output.weights is omitted or is -, it is written to standard output.

Unless -i, --integers is specified, the generated weights are floating-point numbers.

Only some specific mesh formats are supported. See apply-part(1)'s INPUT FORMAT for details.

See WEIGHT FILE for a description of the output format.

-h, --help

Show a help message and exit.

--version

Show version information and exit.

-d, --distribution <spec>

Required. The definition of a weight distribution. This option must be specified once per criterion. See DISTRIBUTION FORMAT and SUPPORTED DISTRIBUTIONS for more information.

-i, --integers

Truncate weights and generate an integer weight distribution instead.

The option -d, --distribution defines how input weights are laid out. It can be specified multiple times, one for each criterion. Its value must follow the following syntax:

distribution  :=  name *( "," param)
param         :=  value / axis
name          :=  STRING
value         :=  FLOAT
axis          :=  "x" / "y" / "z" / "0" / "1" / "2"

For example, the following will lay out weights in ascending order on the horizontal (X, abscissa) axis, from 0 to 100:

weight-gen --distribution linear,x,0,100

And the following example shows how to form a spike of height 4.2 at the origin:

weight-gen --distribution spike,4.2,0,0

The following distributions are supported:

constant,VALUE

Set all weights to be equal to the given VALUE.

linear,AXIS,FROM,TO

Weights follow a linear slope on the given axis, where the points at the lowest coordinate on that axis are assigned the value FROM, and the one at the highest coordinate are assigned the value TO.

spike,HEIGHT,POSITION,...

Weights form a spike of the given height at the given position. The spike has an exponential shape: weights are of the order of exp(-d) where d is the distance between the element and the center of the mesh. Multiple spikes can be specified.

A weight file is a binary file that consists of a header followed by a list of weights, which can either be integers or floating points. Below is the ABNF representation of the file:

file            = magic version flags criterion-count weight-count weights
magic           = %x4d %x65 %x57 %x65  ; "MeWe"
version         = %x01                 ; Version 1
flags           = %x00-FF              ; see the Flags paragraph
criterion-count = U16                  ; Number of criteria
weight-count    = U64                  ; Number of weights per criterion
weights         = *I64 / *F64          ; criterion-count times weight-count weights

Some notes:

•Weights are laid out as weight-count arrays of criterion-count items.
•U16 is a little-endian 2-byte unsigned integer.
•U64 is a little-endian 8-byte unsigned integer.
•I64 is a little-endian 8-byte signed integer.
•F64 is a little-endian-encoded binary64 IEEE 754-2008 floating point.

The flags byte has the following meaning, from the least significant bit to the most:

•The first bit is 1 if weights are integers (I64), or 0 if weights are floats (F64),
•The other bits are left unspecified.

mesh-part(1)

This executable is part of coupe, which is maintained by Hubert Hirtz <hubert@hirtz.pm> under the direction of Franck Ledoux <franck.ledoux@cea.fr> and the supervision of Cédric Chevalier <cedric.chevalier@cea.fr> and Sébastien Morais <sebastien.morais@cea.fr>.

For more information on coupe development, see <https://github.com/LIHPC-Computational-Geometry/coupe>.

2024-02-06