AppInfo.h

Classes

AppInfo -- General information for applications. (full description)

class AppInfo

Interface

Public Members
static Vector<String> workDirectories(uInt minimumFreeSpaceInMB=0)
static String workDirectory(uInt minimumFreeSpaceInMB=0)
static String workFileName(uInt minimumFreeSpaceInMB=0, const String &filenamePrefix="aipstmp_")
static Int availableMemoryInMB()
static uInt memoryInMB()
static uInt nProcessors()
static Double timeZone()
Private Members
static void init()

Description

Review Status

Reviewed By:
wbrouw
Date Reviewed:
1997/10/30
Programs:
Tests:

Prerequisite

Synopsis

This class provides general information that an application might want to know about it's processing environment. This will be based either on information coded into aipsrc variables, or on information which can be obtained directly from some other source. For example, the time zone will generally be obtained from the host OS, but it can be over-ridden by an aipsrc variable if necessary.

Generally speaking, this class is provided to hide the details of how the information is encoded into an aipsrc variables and to avoid having to change applications if the information moves from being coded into a variable to being deduced at runtime.

It is expected that the information which is available from this class will accrete with time.

Example

    if (AppInfo::nProcessors() > 1) {
       ... do something clever in parallel ...
    } else {
      ... serial code ...
    }

Motivation

Further encapsulate information which is usually in aipsrc variables.

Thrown Exceptions

To Do

Member Description

static Vector<String> workDirectories(uInt minimumFreeSpaceInMB=0)

Return a list of directory names into which the user may write data. If minimumFreeSpace is set (>0) then only directories with at least that much free space (in megabytes) are returned. If the aipsrc variable user.directories.work is set, the candidate directories are taken from that variable, otherwise the current working directory (".") is chosen if it exists and is writeable, otherwise /tmp is the candidate. Only one of "." and "/tmp" is chosen, not both.

If no suitable directories are found (i.e., writable directories with enough free space), a zero-length vector is returned. A warning is issued to the logging system for directories which do not exist or are not writable.

static String workDirectory(uInt minimumFreeSpaceInMB=0)

Choose a workDirectory with at least minimumFreeSpace MB of free space available. It uses workDirectories. If there is more than one valid directory it arranges to choose different directories in succession in an attempt to spread out the I/O. That is, on the first call it will return directory1, on the second it will return directory2, etc. in a cyclical fashion. One can imagine more elaborate algorithms than this, however this should suffice for some time, if not forever.

Thrown Exceptions

static String workFileName(uInt minimumFreeSpaceInMB=0, const String &filenamePrefix="aipstmp_")

This function returns a fully qualified filename for a non-existent file in a work directory with enough free space. That is, you can create a temporary file with the name returned from this function. Tthis function calls workDirectory and then appends a unique (files does not exist) filename. By default the prefix of temporary file name is aipstmp_, but you can override this if you choose.

Thrown Exceptions

static Int availableMemoryInMB()

How much memory is available for this process? Note that this number can be less than zero if the process has overdrawn its account. This function returns: 

    AppInfo::memoryInMB() - Memory::allocatedMemoryInBytes()/1024/1024;
You should use this value when making determinations about whether to put something in memory or do I/O instead.

static uInt memoryInMB()

Total memory in MB that the process may use. Reports system.resources.memory if it is set, otherwise return 64 (considered to be the base level for AIPS++).

static uInt nProcessors()

Number of processors on the local host. Returns system.resources.numcpu if it is set, otherwise 1.

static Double timeZone()

Return the local time zone offset in day fractions. This value has to be added to UTC to get local time. Generally the OS supplied value will be used, however it can be overridden with system.time.tzoffset if necessary.

static void init()

Force an initialization of the AppInfo values.