eldo_user

Eldo Control Language
Parallel Operation
Parallel Operation
This section is divided into the following:
• General Settings for Parallelism in ECL
• Parallel Construct
• Parallel Loops
• Extended Simulation Functions
• Launching ECL Simulations on Different Machines
General Settings for Parallelism in ECL
Parallelism in ECL means that ECL code will be executed inside different execution threads at
the same time. These threads belong to the main Eldo process, so they will always be run on the
computer that executes the ECL netlist.
The parallelizable ECL code specified by the user is split by ECL into jobs. The threads will
execute these jobs in parallel. There can be more jobs than threads; in that case a thread will
execute another job when it has finished its first job. When there is no parallelism, there is only
one thread, the main thread, which executes all these jobs sequentially.
It is usually interesting to run simulations inside these jobs so that they are executed in parallel.
Simulations are launched by ECL on other Eldo processes (they can be even launched on
different machines when using the .ELDO_CL_MPRUN command). It is important to
understand that parallelism is done at the level of the threads executing ECL jobs, not at the
level of the Eldo processes running simulations; the Eldo processes will be run in parallel only if
the jobs executing the simulation commands are executed by different threads.
The maximum number of threads used for parallelism can be set using the option
set_eldo_cl_max_para=val. The default value corresponds to the number of processors of the
computer. If threads are used to run simulations on the same computer, it is not advised to
increase this number (having more threads than processors to execute heavy jobs is not
efficient).
Concurrency Issues
ECL is very strict about what can be parallelized to avoid concurrency issues (variables having
different values depending on the order of execution of the jobs) and will output errors if the
code is not thread safe. The best way to write correct parallel code is to store any result inside
arrays indexed by the index of the current job and to perform any post-processing inside
sequential code.
Eldo® User's Manual, 15.3 1039