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MathGroup Archive 1998

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Which Communications to Use for MathLink on NT?



Hi, mathgroup

in [mg11314] I asked about the slowdown of MathLink on NT machines.
There was one RE-posting on this, also I got another response by direct
email. 

Both also encountered this slowdown. One told me, it is almost directly
proportional to the number of MathLink calls and almost independent of
the amount of data transferred in the calls.

To overcome it, both suggested to buffer calls, i.e. write another
interface for the function to be called many times, collect all the
arguments and then call the "buffered" function only a few times
returning multiple results over one MathLink call.

This however would screw up the structure of my programming quite a bit.
It certainly would help, as first experiments show.

Now I asked an NT expert, because I still can not believe, that the idle
process eats up that much processor power (much more than 90%!) even if
there is lot of work to be done. The expert told me, if TCPIP  is the
underlying data transport mechanism, he would not wonder about  this
slowdown. TCPIP is very fine to connect to other computers, but as a
means of communication within the same computer... If I would use 
named pipes instead, he expected much increase. According to him, TCPIP
always  includes "waiting for the network being ready", even if there 
is no physical network and if it is all in the same computer. He was
not  amazed, that the Idle process takes over many times, although one
of the two (frontend or the mathlinked program) is always ready.
According to him, it is technically possible, to exchange data between
Programs on NT without the Idle process coming in between (if there is
no disk- activity, only other Programs or NT itself might come in
between,  according to priority).

With this information, I looked up the Mathematica-bible. On pp631 and
655 I found, that "MathLink can use any interprogram communications
mechanism, that exists on your computer system". Well, HOW can I  tell
* which communications mechanism my system takes by default, * which
other communications mechanism I might use instead, and how can I
actually direct it to use NamedPipes. In Mathematica 2.2.3, if I
remember right, there was a dialog box where one might select "LOCAL"
protocol. Where has this choice gone now? - even if the LOCAL protocol
does not exist any longer?

One other thing, my NT expert suggested to me to think about
programmati- cally increasing the priority of the MathLink process
(after it has gained control) in order to prevent it to be pre-empted
too often and to return its priority to the normal state, before it
goes to sleep. Would this be feasible?

Thanks in advance,

Dipl.-Math. Adalbert Hanszen <hsse@amath01.amath.zeiss.de>



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