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running_molpro_on_parallel_computers [2021/04/27 11:37]
qianli [Specifying parallel execution] 		running_molpro_on_parallel_computers [2021/06/02 08:46]
qianli
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 There are different GA implementation options (runtimes), and there are advantages and disadvantages for using one or the other implementation (see [[GA Installation]]). There are different GA implementation options (runtimes), and there are advantages and disadvantages for using one or the other implementation (see [[GA Installation]]).
  
-The Molpro binary is built with the ''--with-sockets'' GA runtime, which requires pre-allocation of GA memory in some large calculations. +**Since Molpro 2021.2 the [[#disk option]] is used by default** in single node calculation, in which case large data structures are simply kept in MPI files. 
-**Failing to preallocate sufficient amount of GA memory may lead to crashes or incorrect results, unless the [[#disk option]] is used.** +The behavior of previous versions can be recovered by the ''--ga-impl ga'' command line option. 
-It is therefore very important to read and understand [[#memory specifications]] before trying to run large scale parallel calculations with Molpro.+However, ''--ga-impl ga'' requires pre-allocation of GA memory in many calculations if the ''socket'' GA runtime is used, and failing to preallocate sufficient amount of GA memory may lead to crashes or incorrect results. 
 +Preallocating GA is not required with the ''mpi-pr'' runtime of GA or with the disk option. 
 ===== GA Installation notes  ===== ===== GA Installation notes  =====
  
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   * **''-M''** As described above.   * **''-M''** As described above.
-  * **''-M'' and ''-m''** The specified amount $m$ is allocated for each core, the the remaining memory for GA.+  * **''-M'' and ''-m''** The specified amount $m$ is allocated for each core, the remaining memory for GA.
   * **''-M'' and ''-G''** The specified amount $G$ is allocated for GA, and the remaining amount is split equally for stack memory of each process.   * **''-M'' and ''-G''** The specified amount $G$ is allocated for GA, and the remaining amount is split equally for stack memory of each process.
   * **''-M'' and ''-G'' and ''-m''** The specified amounts of $m$ and $G$ are allocated, and the $M$ value is ignored.   * **''-M'' and ''-G'' and ''-m''** The specified amounts of $m$ and $G$ are allocated, and the $M$ value is ignored.
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 Since version 2021.1, Molpro can use MPI files instead of GlobalArrays to store large global data. This option can be enabled globally by setting the environment variable ''MOLPRO_GA_IMPL'' to ''DISK'', or by passing the ''%%--ga-impl disk%%'' command-line option. Since version 2021.1, Molpro can use MPI files instead of GlobalArrays to store large global data. This option can be enabled globally by setting the environment variable ''MOLPRO_GA_IMPL'' to ''DISK'', or by passing the ''%%--ga-impl disk%%'' command-line option.
 +Since version 2021.2 the disk option is made the default in single-node calculations.
 Some programs in Molpro including DF-HF, DF-KS, (DF-)MULTI, DF-TDDFT, and PNO-LCCSD also support an input option ''implementation=disk'' to enable the disk option for the particular job step. Some programs in Molpro including DF-HF, DF-KS, (DF-)MULTI, DF-TDDFT, and PNO-LCCSD also support an input option ''implementation=disk'' to enable the disk option for the particular job step.
 The file system for these MPI files must be accessible by all processors. The file system for these MPI files must be accessible by all processors.
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 The numerical computation of gradients or Hessians, or the automatic generation of potential energy surfaces, requires many similar calculations at different (displaced) geometries. An automatic parallel computation of the energy and/or gradients at different geometries is implemented for the gradient, hessian, and surf programs. In this so-called mppx-mode, each processing core runs an independent calculation in serial mode. This happens automatically using the ''-n'' available cores. The automatic mppx processing can be switched off by setting option ''mppx=0'' on the ''OPTG'', ''FREQ'', or ''HESSIAN'' command lines. In this case, the program will process each displacement in the standard parallel mode.  The numerical computation of gradients or Hessians, or the automatic generation of potential energy surfaces, requires many similar calculations at different (displaced) geometries. An automatic parallel computation of the energy and/or gradients at different geometries is implemented for the gradient, hessian, and surf programs. In this so-called mppx-mode, each processing core runs an independent calculation in serial mode. This happens automatically using the ''-n'' available cores. The automatic mppx processing can be switched off by setting option ''mppx=0'' on the ''OPTG'', ''FREQ'', or ''HESSIAN'' command lines. In this case, the program will process each displacement in the standard parallel mode. 
  
 +===== Options for developers =====
 +
 +==== Debugging options ====
 +
 +  * **''%%--ga-debug%%''** activates GA debugging statements.
 +  * **''%%--check-collective%%''** check collective operations when debugging.
  
-===== Options for pure MPI-based PPIDD build =====+==== Options for pure MPI-based PPIDD build ====
  
 This section is **not** applicable if the Molpro binary release is used, or when Molpro is built using the GlobalArrays toolkit (which we recommend). This section is **not** applicable if the Molpro binary release is used, or when Molpro is built using the GlobalArrays toolkit (which we recommend).