CODEWITHSUNDEEP
cperformanceopenvmsbenchmarking
nantonop
nantonop

Reputation: 167

OpenVMS timer precision, better than millisecond accuracy.

I'm wondering which function offers best precision/accuracy for timing on OpenVMS in C.

We have an HP Integrity rx2660 server running OpenVMS V8.3-1H1.

My search so far points to $GETTIM_PREC which offers 100-nano resolution but millisecond accuracy. Does it get any better than this?

regards

Upvotes: 5

Views: 419

Answers (1)

HABO
HABO

Reputation: 15816

From the System Services Reference Manual:

On Integrity servers, $GETTIM_PREC returns the system time after accounting for the time elapsed since the last one millisecond update of the system time.

On Alpha, this service is equivalent to $GETTIM service and just returns the last updated system time. The successful completion status of the service on ALPHA is SS$_LOWPREC.

So on Integrity it may be better than 1ms accuracy, but there doesn't seem to be a commitment to any particular accuracy.

EXE$GL_ABSTIM_TICS only provided accuracy to 10ms. I don't know of any other internal values that are more accurate and haven't stumbled across an IDSM for V8.

Upvotes: 1

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