pvm_reduce

Scilab function
Last update : 25/04/2007

pvm_reduce - Performs a reduce operation over members of the specified group

### Calling Sequence

  `[buff, info] = pvm_reduce(func, buff, msgtag, group, rootginst)`

### Parameters

- `func : string, defines the operation performed on the global` data. Should be : Max, Min, Sum or Pro.
- `buff : scalar, local scilab variable. On return, the data array on` the root will be overwritten with the result of the reduce operation over the group.
- `msgtag : integer, message tag supplied by the user. msgtag` should be >= 0. It allows the user's program to distinguish between different kinds of messages.
- `group` : string, group name of an existing group.
- `rootginst : integer, instance number of group member who gets the` result.
- `info : integer, status code returned by the routine. Values` less than zero indicate an error.

### Description

`pvm_reduce` performs global operations such as max, min, sum or product over all the tasks in a group. All group members call pvm_reduce with their local data, and the result of the reduction operation appears on the user specified root task root. The root task is identified by its instance number in the group.

Max and Min are implemented for scalar datatypes (double, complex). For complex values the minimum [maximum] is that complex pair with the minimum [maximum] modulus. Sum and Product are implemented for scalar datatypes.

Note: pvm_reduce does not block. If a task calls pvm_reduce and then leaves the group before the root has called pvm_reduce an error may occur.

### See Also

`pvm_bcast` , `pvm_barrier` , `pvm_send` , `pvm_getinst` , `pvm_gsize` , `pvm_joingroup` , `pvm_lvgroup` ,