DBT: Add lightweight fork of DBCSR tensor library from Patrick Seewald

src/dbt/PACKAGE

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+{
+    "description": "Distributed Block-sparse Tensors",
+    "requires": ["./tas", "../dbm", "../base", "../common", "../mpiwrap", "../offload"],
+    "public": ["dbt_api.F"],
+}

src/dbt/README.md

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+# DBT: Distributed Block-sparse Tensors
+
+The DBT is a lightweight fork of [DBCSR Tensors](https://github.com/cp2k/dbcsr/tree/develop/src/tensors)
+and the related [TAS layer](https://github.com/cp2k/dbcsr/tree/develop/src/tas)
+for Tall-and-Skinny matrices.
+
+The code was originally written by Patrick Seewald and is well documented in his
+[PhD thesis](https://www.cp2k.org/_media/docs:phd_thesis_patrick_seewald.pdf).

src/dbt/dbt_allocate_wrap.F

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+!--------------------------------------------------------------------------------------------------!
+!   CP2K: A general program to perform molecular dynamics simulations                              !
+!   Copyright 2000-2022 CP2K developers group <https://cp2k.org>                                   !
+!                                                                                                  !
+!   SPDX-License-Identifier: GPL-2.0-or-later                                                      !
+!--------------------------------------------------------------------------------------------------!
+
+! **************************************************************************************************
+!> \brief Wrapper for allocating, copying and reshaping arrays.
+!> \todo with fortran 2008 support, this should be replaced by plain ALLOCATE
+!> \note in particular ALLOCATE(..., SOURCE=...) does not work in gcc 5.4.0, see also
+!>       https://gcc.gnu.org/bugzilla/show_bug.cgi?id=44672
+!> \author Patrick Seewald
+! **************************************************************************************************
+MODULE dbt_allocate_wrap
+   #:include "dbt_macros.fypp"
+   #:set maxdim = fortran_max_ndim
+
+   USE kinds, ONLY: dp
+
+#include "../base/base_uses.f90"
+   IMPLICIT NONE
+   PRIVATE
+
+   PUBLIC :: allocate_any
+
+   INTERFACE allocate_any
+      #:for dim in range(1, maxdim+1)
+         MODULE PROCEDURE allocate_${dim}$d
+      #:endfor
+   END INTERFACE
+
+CONTAINS
+
+   #:for dim in range(1, maxdim+1)
+! **************************************************************************************************
+!> \brief Allocate array according to shape_spec. Possibly assign array from source.
+!> \note this does not fully replace Fortran RESHAPE intrinsic since source and target array must
+!>       have same rank
+!> \param array target array.
+!> \param shape_spec shape of array to be allocated. If not specified, it is derived from source.
+!> \param source source array to be copied to target array, must have same rank as target array.
+!> \param order in which order to copy source to array (same convention as RESHAPE intrinsic).
+!> \author Patrick Seewald
+! **************************************************************************************************
+      SUBROUTINE allocate_${dim}$d(array, shape_spec, source, order)
+         REAL(dp), DIMENSION(${shape_colon(dim)}$), ALLOCATABLE, INTENT(OUT) :: array
+         INTEGER, DIMENSION(${dim}$), INTENT(IN), OPTIONAL                    :: shape_spec
+         REAL(dp), DIMENSION(${shape_colon(dim)}$), INTENT(IN), OPTIONAL     :: source
+         INTEGER, DIMENSION(${dim}$), INTENT(IN), OPTIONAL                    :: order
+         INTEGER, DIMENSION(${dim}$)                                          :: shape_prv
+
+         IF (PRESENT(shape_spec)) THEN
+            IF (PRESENT(order)) THEN
+               shape_prv(order) = shape_spec
+            ELSE
+               shape_prv = shape_spec
+            END IF
+         ELSEIF (PRESENT(source)) THEN
+            IF (PRESENT(order)) THEN
+               shape_prv(order) = SHAPE(source)
+            ELSE
+               shape_prv = SHAPE(source)
+            END IF
+         ELSE
+            CPABORT("either source or shape_spec must be present")
+         END IF
+
+         IF (PRESENT(source)) THEN
+            IF (PRESENT(order)) THEN
+               ALLOCATE (array(${arrlist("shape_prv", nmax=dim)}$))
+               array(${shape_colon(dim)}$) = RESHAPE(source, shape_prv, order=order)
+            ELSE
+               ALLOCATE (array(${arrlist("shape_prv", nmax=dim)}$), source=source)
+            END IF
+         ELSE
+            ALLOCATE (array(${arrlist("shape_prv", nmax=dim)}$))
+         END IF
+
+      END SUBROUTINE
+   #:endfor
+END MODULE

src/dbt/dbt_api.F

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+!--------------------------------------------------------------------------------------------------!
+!   CP2K: A general program to perform molecular dynamics simulations                              !
+!   Copyright 2000-2022 CP2K developers group <https://cp2k.org>                                   !
+!                                                                                                  !
+!   SPDX-License-Identifier: GPL-2.0-or-later                                                      !
+!--------------------------------------------------------------------------------------------------!
+
+! **************************************************************************************************
+!> \brief This is the start of a dbt_api, all publically needed functions
+!>        are exported here. The others remain private to the library.
+!>        Currently, this is the CP2K used set.
+!>        Ultimately, a reduced subset and well defined api will remain,
+!>        possibly grouped in to standard and expert api.
+!>        Currently, this is work in progress.
+!> \author Patrick Seewald
+! **************************************************************************************************
+MODULE dbt_api
+
+   USE dbt_block,                       ONLY: dbt_iterator_blocks_left,&
+                                              dbt_iterator_next_block,&
+                                              dbt_iterator_start,&
+                                              dbt_iterator_stop,&
+                                              dbt_iterator_type,&
+                                              dbt_reserved_block_indices
+   USE dbt_index,                       ONLY: dbt_get_mapping_info
+   USE dbt_io,                          ONLY: dbt_write_blocks,&
+                                              dbt_write_split_info,&
+                                              dbt_write_tensor_dist,&
+                                              dbt_write_tensor_info
+   USE dbt_methods,                     ONLY: &
+        dbt_batched_contract_finalize, dbt_batched_contract_init, dbt_contract, &
+        dbt_contract_index, dbt_copy, dbt_copy_matrix_to_tensor, dbt_copy_tensor_to_matrix, &
+        dbt_get_block, dbt_get_stored_coordinates, dbt_put_block, dbt_reserve_blocks
+   USE dbt_split,                       ONLY: dbt_split_blocks
+   USE dbt_test,                        ONLY: dbt_checksum,&
+                                              dbt_contract_test
+   USE dbt_types,                       ONLY: &
+        dbt_blk_size, dbt_blk_sizes, dbt_clear, dbt_create, dbt_default_distvec, dbt_destroy, &
+        dbt_dims => dims_tensor, dbt_distribution_destroy, dbt_distribution_new, &
+        dbt_distribution_type, dbt_filter, dbt_finalize, dbt_get_info, dbt_get_num_blocks, &
+        dbt_get_num_blocks_total, dbt_get_nze, dbt_get_nze_total, dbt_max_nblks_local, &
+        dbt_mp_dims_create, dbt_mp_environ_pgrid => mp_environ_pgrid, dbt_nblks_local, &
+        dbt_nblks_total, dbt_nd_mp_comm, dbt_nd_mp_free, dbt_ndims => ndims_tensor, &
+        dbt_ndims_matrix_column => ndims_matrix_column, dbt_ndims_matrix_row => ndims_matrix_row, &
+        dbt_pgrid_change_dims, dbt_pgrid_create, dbt_pgrid_create_expert, dbt_pgrid_destroy, &
+        dbt_pgrid_type, dbt_scale, dbt_type
+
+   IMPLICIT NONE
+
+   PRIVATE
+
+   CHARACTER(len=*), PARAMETER, PRIVATE :: moduleN = 'dbt_api'
+
+   PUBLIC :: dbt_contract, dbt_contract_test
+   PUBLIC :: dbt_get_block
+   PUBLIC :: dbt_get_stored_coordinates
+   PUBLIC :: dbt_put_block
+   PUBLIC :: dbt_reserve_blocks
+   PUBLIC :: dbt_create
+   PUBLIC :: dbt_destroy
+   PUBLIC :: dbt_distribution_destroy
+   PUBLIC :: dbt_distribution_new
+   PUBLIC :: dbt_distribution_type
+   PUBLIC :: dbt_nd_mp_comm
+   PUBLIC :: dbt_nd_mp_free
+   PUBLIC :: dbt_type
+   PUBLIC :: dbt_iterator_next_block
+   PUBLIC :: dbt_iterator_blocks_left
+   PUBLIC :: dbt_iterator_stop
+   PUBLIC :: dbt_iterator_start
+   PUBLIC :: dbt_iterator_type
+   PUBLIC :: dbt_split_blocks
+   PUBLIC :: dbt_pgrid_type
+   PUBLIC :: dbt_pgrid_create
+   PUBLIC :: dbt_pgrid_create_expert
+   PUBLIC :: dbt_pgrid_destroy
+   PUBLIC :: dbt_filter
+   PUBLIC :: dbt_mp_environ_pgrid
+   PUBLIC :: dbt_copy_matrix_to_tensor
+   PUBLIC :: dbt_blk_sizes
+   PUBLIC :: dbt_copy
+   PUBLIC :: dbt_copy_tensor_to_matrix
+   PUBLIC :: dbt_get_info
+   PUBLIC :: dbt_checksum
+   PUBLIC :: dbt_finalize
+   PUBLIC :: dbt_scale
+   PUBLIC :: dbt_get_num_blocks, dbt_get_num_blocks_total
+   PUBLIC :: dbt_get_nze, dbt_get_nze_total
+   PUBLIC :: dbt_clear
+   PUBLIC :: dbt_get_mapping_info
+   PUBLIC :: dbt_write_split_info
+   PUBLIC :: dbt_write_blocks
+   PUBLIC :: dbt_write_tensor_dist
+   PUBLIC :: dbt_write_tensor_info
+   PUBLIC :: dbt_mp_dims_create
+   PUBLIC :: dbt_batched_contract_init
+   PUBLIC :: dbt_batched_contract_finalize
+   PUBLIC :: dbt_ndims
+   PUBLIC :: dbt_dims
+   PUBLIC :: dbt_pgrid_change_dims
+   PUBLIC :: dbt_reserved_block_indices
+   PUBLIC :: dbt_contract_index
+   PUBLIC :: dbt_ndims_matrix_row
+   PUBLIC :: dbt_ndims_matrix_column
+   PUBLIC :: dbt_nblks_local
+   PUBLIC :: dbt_nblks_total
+   PUBLIC :: dbt_blk_size
+   PUBLIC :: dbt_max_nblks_local
+   PUBLIC :: dbt_default_distvec
+
+END MODULE dbt_api