##

14.1 Sorted integrals

If the integrals are stored on disk, immediately after evaluation they
are sorted into complete symmetry-packed matrices, so that later
program modules that use them can do so as efficiently as possible.
As discussed above, it is normally not necessary to call the integral
and sorting programs
explicitly, but sometimes additional options are desired, and can be
specified using the `INT`
command, which should appear after geometry and basis specifications,
and before any commands to evaluate an energy.
`INT`

,
[`[NO]SORT`

,]
[`SPRI=`

value]

`SORT`

,
[`SPRI=`

value]

`INT,NOSORT;SORT`

can be used to explicitly separate the integral
evaluation and sorting steps, for example to collect separate timing
data. With value set to more than 1 in the `SPRI`

option,
all the two-electron integrals are printed.

The detailed options for the integral sort can be specified using the
`AOINT` parameter set, using the input form

`AOINT`

,
key1=value1,
key2=value2,

`AOINT`

can be used with or without an explicit `INT`

command.

The following summarizes the possible keys, together with their meaning,
and default values.

**c_final**
- Integer specifying the compression algorithm to be
used for the final sorted integrals. Possible values are 0 (no
compression), 1 (compression using 1, 2, 4 or 8-byte values), 2 (2,
4 or 8 bytes), 4 (4, 8 bytes) and 8.
Default: 0
**c_sort1**
- Integer specifying the compression algorithm for
the intermediate file during the sort.
Default: 0
**c_seward**
- Integer specifying the format of label tagging and
compression
written
by the integral program and read by the sort program.
Default: 0
**compress**
- Overall compression; c_final, c_seward and c_sort1
are forced internally to be not less than this parameter.
Default: 1
**thresh**
- Real giving the truncation threshold for compression.
Default: , which means use the integral evaluation threshold (
`GTHRESH,TWOINT`

)
**io**
- String specifying how the sorted integrals are
written. Possible values are
`molpro`

(standard
MOLPRO record on file 1) and `eaf`

(Exclusive-access
file). `eaf`

is permissible only if the program has been
configured for MPP usage, and at present `molpro`

is
implemented only for serial execution. `molpro`

is required if
the integrals are to be used in a restart job. For maximum
efficiency on a parallel machine, `eaf`

should be used, since
in that case the integrals are distributed on separate
processor-local files.

For backward-compatibility purposes, two convenience commands are also
defined:
`COMPRESS`

is equivalent to `AOINT,COMPRESS=1`

, and
`UNCOMPRESS`

is equivalent to `AOINT,COMPRESS=0`

.

molpro@molpro.net 2019-05-24