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<h2><font face="Arial"><strong>PolyML.Statistics structure</strong></font></h2>
<p>The PolyML.Statistics structure provides a way for a program to read information
about the run-time system. As well as getting information about the local Poly/ML
process it is also possible to get information about another Poly/ML process
being run by the same user.</p>
<PRE class="mainsig"><STRONG>structure</STRONG> Statistics:
<strong>sig</strong>
<strong>val</strong> getLocalStats : unit ->
{sizeHeap: int,
gcFullGCs: int,
timeGCUser: Time.time,
threadsInML: int,
gcPartialGCs: int,
threadsTotal: int,
timeGCSystem: Time.time,
userCounters: int vector,
threadsWaitIO: int,
timeNonGCUser: Time.time,
sizeAllocation: int,
timeNonGCSystem: Time.time,
threadsWaitMutex: int,
threadsWaitSignal: int,
sizeAllocationFree: int,
sizeHeapFreeLastGC: int,
threadsWaitCondVar: int,
sizeHeapFreeLastFullGC: int}
<strong>val</strong> getRemoteStats : int ->
{sizeHeap: int,
gcFullGCs: int,
timeGCUser: Time.time,
threadsInML: int,
gcPartialGCs: int,
threadsTotal: int,
timeGCSystem: Time.time,
userCounters: int vector,
threadsWaitIO: int,
timeNonGCUser: Time.time,
sizeAllocation: int,
timeNonGCSystem: Time.time,
threadsWaitMutex: int,
threadsWaitSignal: int,
sizeAllocationFree: int,
sizeHeapFreeLastGC: int,
threadsWaitCondVar: int,
sizeHeapFreeLastFullGC: int}
<strong>val</strong> setUserCounter : int * int -> unit
<strong>val</strong> numUserCounters : unit -> int
<strong>end</strong></PRE>
<p>There are two functions that return information..</p>
<div class="entryBlock"><PRE class="entrycode"><STRONG>val</STRONG> getLocalStats : unit -> { ... }</PRE>
<div class="entrytext"> Returns information about the Poly/ML
process that has called this function.</div>
</div>
<div class="entryBlock"><PRE class="entrycode"><STRONG>val</STRONG> getRemoteStats : int -> { ... }</PRE>
<div class="entrytext">
<p>Returns information about another Poly/ML process. The argument is the process
id (pid) of the Poly/ML process for which information is requested. Raises
the Fail exception if this is not a currently running Poly/ML process or the
calling user does not have permission to read the statistics. The statistics
are held in shared memory and on Unix systems these are memory-mapped files
in the user's .polyml directory.</p>
</div>
</div><p>The actual information returned is still being determined and may well change.</p>
<p>In addition to information about the run-time system the statistics mechanism
provides a small array of values that can be set by the ML code. This allows
an ML program to set values that can be read in another process.</p>
<div class="entryBlock"><PRE class="entrycode"><STRONG>val</STRONG> numUserCounters : unit -> int</PRE>
<div class="entrytext"> <p>Returns the number of counters available.
Currently this is eight.</p></div>
</div>
<div class="entryBlock">
<PRE class="entrycode"><STRONG>val</STRONG> setUserCounter : int * int -> unit</PRE>
<div class="entrytext">
<p>setUserCounter(n, m) stores the value m in the n-th counter.</p>
</div>
</div><p>Writing to the counters is potentially an expensive operation. If the information
is likely to change rapidly it will usually be best to use a separate thread
to poll the information periodically and update the counter.</p>
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