LaGriT/documentation/lagrit_manual/commands/math.txt

.. _math:

##  MATH

> The **math** routine operates on attributes of a mesh object(s). It performs
arithmetic operations or evaluates mathematical functions on the source mesh
object or objects, and places the results in the sink mesh object. The source
and sink mesh objects can be the same, and there can be either one or two
source objects, depending on the operation selected.

>

> All attributes must have the same type, rank, and length.

The last parameter, value, may or may not be used according to the operation
details listed below.

For the standard arithmetic operations, value can be either a constant or an
attribute. These arithmetic operations work for all types of attributes.

For the mathematical functions other than **floor** and
**ceiling**,&nbsp_place_holder; value is omitted, and the function is
performed on the src_attr and stored in the sink_attr. Mathematical functions
other than **floor** and **ceiling **are not implemented for attributes whose
values are integers.

FORMAT:

> **math** / operation / cmo_sink/attr_sink / range /cmo_src/attr_src / [
value ]

  
operation: The first parameter is one of the following keywords that indicates
the type of work to perform.

> **plus, add, minus, sub, subtract, times,&nbsp_place_holder; multiply, mult,
divide, min, max, modulo ** are arithmetic operators; the result is stored in
sink_attr:

sink_attr = (src_attr) operator (value), where value can be either a numerical
constant or a second mesh object attribute.

min, max are not to be confused with the minimum or maximum value of an
attribute; rather the the result is a comparison of pairs of source values.

>

> **sin, cos, tan, ln** (natural log), and **log10** are mathematical
functions. The value parameter is omitted, and the function is performed on
the src_attr and stored in the sink_attr. These functions are not implemented
for integer attributes.

>

> **floor** and **ceiling** are mathematical functions where value is used as
the lower or upper limit, the value(s) of src_attr are checked against value,
and the results are stored in the sink_attr. These functions work for all
types of attributes.

>

> **power** function uses both value parameters. The first value or src_attr
is raised to the power of the second value or attribute. You cannot use two
constants. At least one of the sources must be an attribute. The result is
stored in the sink_attr.

>

> **exp** and **exp10** functions raise the constant e or the constant 10 to
the power specified by src_attr and stores the result in the sink_attr.

>

> <>**integrate** function computes the product of 'field_value 'times
'element volume' at each element and either saves these products or sums the
products and saves the integrated result.

The syntax is: math/integrate/cmo_sink/attr_sink/range/attr_src_field<>

<>The 'field_value' for an element is either the value of attr_src (if the
attr_src is an element attribute and has length 'nelements') or is the average
of the values at the vertices of the element (if the attr_src is a node
attribute has length 'nnodes').

If sink_attr does not exist or if it exists and has length 'nelements' and
type 'VDOUBLE' the products (<> <>'field_value' times 'element_volume') are
stored in sink_attr.

If sink_attr exists and has length 'scalar' and type 'REAL', then the products
are summed up and the resulting sum if stored in sink_attr. (If the user
requires just the integrated sum this alternative avoids having to use the
pair of commands 'integrate, sum' and also avoids creating the 'nelement' long
sink attribute)

It is assumed that the sink and source attributes are in the same mesh object
and the second cmo name is ignored.

If range is used, it must refer to a set of elements.

>

> **sum** adds all node or element values in attr_src, within the selected
range and writes the result to attr_sink. The sink attribute must be of type
'REAL' or 'INT' (length='scalar') and will be created if it does not exist.

  
cmo_sink, attr_sink: are the sink cmo and sink attribute for the math results
to be written to. These parameters are required for all math operations.

  
range: is the selection set of elements or nodes for the math operation and
may be in one of these 3 forms:

> /ifirst,ilast,istride / numbers indicating attribute set&nbsp_place_holder;
(1,0,0 means all elements or nodes)

/**pset,get**, pset_name / for attributes with length =
'nnodes'&nbsp_place_holder; (all nodes in the named point set)

/**eltset,get**, eltset_name / for attributes with length = 'nelements' (all
elements in the named element set)

  
value: is required by some math operations and can be of type constant or can
be a cmo attribute. The following are possible forms:

> /cmo_src2/attr_src2/ where cmo_src2 may be the same name as the source cmo,
or the name of a second source cmo.

/attr_src2/ assumes attribute is a part of cmo_src

/constant/ is a numerical value

  
EXAMPLES:

**math**/**multiply**/sink_mo/sink_attribute/50,60,3/src_mo/src_attribute/1.0   
**math/add/**mo/attribute/50,60,3/mo/attribute/100.0   
**math/modulo/**mo/attribute/1,0,0/mo/attribute/10   
**math/sub/**sink_mo/sink_attribute/50,60,3/src_mo1/src_attribute1/src_mo2/src_attribute2/   
**math/min/**sink_mo/sink_attribute/1,0,0/src_mo1/src_attribute1/src_mo2/src_attribute2/  
**math**/**ln**/sink_mo/sink_attribute/1,0,0/src_mo/src_attribute/   
**math/floor/**sink_mo/sink_attribute/1,0,0/src_mo/src_attribute/2.0/   
**math/power**/sink_mo/sink_attribute/1,0,0/src_mo/src_attribute/2.0/   
**math/power**/sink_mo/sink_attribute/1,0,0/2.0/src_mo/src_attribute/   
**math/power**/sink_mo/sink_attribute/1,0,0/base_mo/base_attribute/ power_mo/power_attr   
**math/exp**/sink_mo/sink_attribute/1,0,0/src_mo/src_attribute/   
**math/exp10**/sink_mo/sink_attribute/1,0,0/src_mo/src_attribute/   
**math/integrate/** cmotri /Vf /1,0,0/ cmotri/ Fn   
**math/sum/** cmotri / Vfsum /1,0,0/ cmotri / Vf   
**math/sum/** cmotri / area_sum /1,0,0/ cmotri / darea   
&nbsp_place_holder;