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# 6.16.4 Summary of Keywords

(February 4, 2022)

MEM_STATIC

MEM_STATIC
Sets the memory for individual Fortran program modules
TYPE:
INTEGER
DEFAULT:
240 corresponding to 240 MB or 12% of MEM_TOTAL
OPTIONS:
$n$ User-defined number of megabytes.
RECOMMENDATION:
For direct and semi-direct MP2 calculations, this must exceed OVN + requirements for AO integral evaluation (32–160 MB). Up to 2000 MB for large coupled-clusters calculations.

CC_MEMORY

CC_MEMORY
Specifies the maximum size, in MB, of the buffers for in-core storage of block-tensors in CCMAN and CCMAN2.
TYPE:
INTEGER
DEFAULT:
50% of MEM_TOTAL. If MEM_TOTAL is not set, use 1.5 GB. A minimum of 192 MB is hard-coded.
OPTIONS:
$n$ Integer number of MB
RECOMMENDATION:
Larger values can give better I/O performance and are recommended for systems with large memory (add to your .qchemrc file. When running CCMAN2 exclusively on a node, CC_MEMORY should be set to 75–80% of the total available RAM. )

CC_BACKEND

CC_BACKEND
Used to specify the computational back-end of CCMAN2.
TYPE:
STRING
DEFAULT:
VM Default shared-memory disk-based back-end
OPTIONS:
XM libxm shared-memory disk-based back-end INCORE in-core memory back-end
RECOMMENDATION:
Use XM for large jobs with limited memory or when the performance of the default disk-based back-end is not satisfactory, INCORE for small jobs that fit in main memory.