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mirror of https://github.com/TREX-CoE/qmckl.git synced 2024-12-21 20:04:08 +01:00

Added woodbury 3x3 HPC and DOC kernels back. They pass the tests.

This commit is contained in:
Francois Coppens 2023-07-12 15:39:44 +02:00
parent 81be8263a0
commit 44323468e6
2 changed files with 695 additions and 3 deletions

View File

@ -2059,6 +2059,698 @@ assert(rc == QMCKL_SUCCESS);
#+end_src
* Woodbury 3x3
** ~qmckl_woodbury_3x3~
:PROPERTIES:
:Name: qmckl_woodbury_3x3
:CRetType: qmckl_exit_code
:FRetType: qmckl_exit_code
:END:
*** Introduction
The Woodbury 3x3 kernel. It is used to apply two rank-1 updates at once. The formula used in
this algorithm is called the Woodbury Matrix Id
\[
(S + U V)^{-1} = S^{-1} - C B^{-1} D
\]
where
$S$ is the Slater-matrix
$U$ and $V$ are the matrices containing the updates and the canonical basis matrix
$S^{-1}$ is the inverse of the Slater-matrix
$C:= S^{-1}U$, a Dim $\times 3$ matrix
$B := 1 + VC$, the $3 \times 3$ matrix that is going to be inverted
$D := VS^{-1}$, a $3 \times Dim$ matrix
If the determinant of the Slater-matrix is passed, it will be updated to the determinant resulting
from applying the updates to the original matrix.
*** API
#+NAME: qmckl_woodbury_3x3_args
| Variable | Type | In/Out | Description |
|-----------------+-------------------+-------+-------------------------------------------------|
| ~context~ | ~qmckl_context~ | in | Global state |
| ~LDS~ | ~uint64_t~ | in | Leading dimension of Slater_inv |
| ~Dim~ | ~uint64_t~ | in | Dimension of Slater_inv |
| ~Updates~ | ~double[3*Dim]~ | in | Array containing the updates |
| ~Updates_index~ | ~uint64_t[3]~ | in | Array containing the rank-1 updates |
| ~breakdown~ | ~double~ | in | Break-down parameter on which to fail or not |
| ~Slater_inv~ | ~double[LDS*Dim]~ | inout | Array containing the inverse of a Slater-matrix |
| ~determinant~ | ~double~ | inout | Determinant of Slater-matrix |
*** Requirements
- ~context~ is not ~qmckl_null_context~
- ~LDS >= 3~
- ~Dim >= 3~
- ~Updates~ is allocated with $3 \times Dim$ elements
- ~Updates_index~ is allocated with $3$ elements
- ~breakdown~ is a small number such that $0 < breakdown << 1$
- ~Slater_inv~ is allocated with $Dim \times Dim$ elements
*** Pedagogical kernel source (in Fortran)
The following source code written in Fortran is inteded to illustrate how the kernel works. Even though the kernel is
able to do numerically correct computations, it does not do it in the most efficient way possible. It should therefore
not be used in real workloads.
#+begin_src f90 :tangle (eval f)
integer function qmckl_woodbury_3x3_doc_f(&
context, &
lds, dim, &
upds, &
updates_index, &
breakdown, &
s_inv, &
determinant) result(info)
use qmckl
implicit none
integer*8 , intent(in) :: context
integer*8 , intent(in) :: lds, dim
integer*8 , intent(in) :: updates_index(3)
real*8 , intent(in) :: upds(3 * lds)
real*8 , intent(in) :: breakdown
real*8 , intent(inout) :: s_inv(dim * lds)
real*8 , intent(inout) :: determinant
integer*8 , dimension(3, dim) :: V
integer*8 , dimension(3, 3) :: Id
real*8 , dimension(dim, dim) :: Inverse
real*8 , dimension(dim, 3) :: Updates, C
real*8 , dimension(3, 3) :: D, invD
real*8 , dimension(3, dim) :: E, F
real*8 :: detD, idetD, idenominator, update
integer*8 :: i, j, k, l
info = QMCKL_FAILURE
if (context == QMCKL_NULL_CONTEXT) then
info = QMCKL_INVALID_CONTEXT
return
endif
! Construct V(3, dim) matrix
V = 0
V(1, updates_index(1)) = 1
V(2, updates_index(2)) = 1
V(3, updates_index(3)) = 1
! Construct Id(3, 3) matrix
Id = 0
Id(1, 1) = 1
Id(2, 2) = 1
Id(3, 3) = 1
! Convert 'upds' and 's_inv' into the more easily readable Fortran
! matrices 'Updates' and 'Inverse'.
call convert(upds, s_inv, Updates, Inverse, int(3,8), lds, dim)
! Compute C(dim, 3) = Inverse(dim, dim) x Updates(dim, 3)
C = 0
do i = 1, dim
do j = 1, 3
do k = 1, dim
C(i, j) = C(i, j) + Inverse(i, k) * Updates(k, j)
end do
end do
end do
! Construct matrix D(3, 3) := I(3, 3) + V(3, dim) x C(dim, 3)
D = 0
do i = 1, 3
do j = 1, 3
do k = 3, dim
D(i, j) = D(i, j) + V(i, k) * C(k, j)
end do
end do
end do
D = Id + D
! Compute determinant := det(D) explicitly
detD = D(1,1) * (D(2,2) * D(3,3) - D(2,3) * D(3,2)) - &
D(1,2) * (D(2,1) * D(3,3) - D(2,3) * D(3,1)) + &
D(1,3) * (D(2,1) * D(3,2) - D(2,2) * D(3,1))
! Return early if det(D) is too small
if (abs(detD) < breakdown) return
! Update det(S)
determinant = determinant * detD
idetD = 1.0d0 / detD
! Compute inv(D) explicitly
invD(1,1) = (D(2,2) * D(3,3) - D(3,2) * D(2,3)) * idetD
invD(1,2) = -(D(1,2) * D(3,3) - D(3,2) * D(1,3)) * idetD
invD(1,3) = (D(1,2) * D(2,3) - D(2,2) * D(1,3)) * idetD
invD(2,1) = -(D(2,1) * D(3,3) - D(3,1) * D(2,3)) * idetD
invD(2,2) = (D(1,1) * D(3,3) - D(3,1) * D(1,3)) * idetD
invD(2,3) = -(D(1,1) * D(2,3) - D(2,1) * D(1,3)) * idetD
invD(3,1) = (D(2,1) * D(3,2) - D(3,1) * D(2,2)) * idetD
invD(3,2) = -(D(1,1) * D(3,2) - D(3,1) * D(1,2)) * idetD
invD(3,3) = (D(1,1) * D(2,2) - D(2,1) * D(1,2)) * idetD
! Compute E(3, dim) := V(3, dim) x Inverse(dim, dim)
E = 0
do i = 1, 3
do j = 1, dim
do k = 1, dim
E(i, j) = E(i, j) + V(i, k) * Inverse(k, j)
end do
end do
end do
! Compute F(3, dim) := invD(3, 3) x E(3, dim)
F = 0
do i = 1, 3
do j = 1, dim
do k = 1, 3
F(i, j) = F(i, j) + invD(i, k) * E(k, j)
end do
end do
end do
! Compute Inverse(dim, dim) := Inverse(dim, dim) - C(dim, 3) x F(3, dim)
do i = 1, dim
do j = 1, dim
do k = 1, 3
Inverse(i, j) = Inverse(i, j) - C(i, k) * F(k, j)
end do
end do
end do
! Copy updated inverse and later updates
! back to s_inv and later_upds
call copy_back_inv(Inverse, s_inv, lds, dim)
info = QMCKL_SUCCESS
end function qmckl_woodbury_3x3_doc_f
#+end_src
**** C interface (not directly exposed)
The function ~qmckl_sm_splitting_core_doc~ makes sure that
~qmckl_sm_splitting_core_doc_f~ can be called from C using the
~ISO_C_BINDING~. Function ~qmckl_sm_splitting_core_doc~ will be
exposed in ~qmckl.h~ and ~qmckl_f.F90~, but
~qmckl_sm_splitting_core_doc_f~ will not.
#+CALL: generate_c_interface(table=qmckl_woodbury_3x3_args,rettyp=get_value("CRetType"),fname="qmckl_woodbury_3x3_doc")
#+RESULTS:
#+begin_src f90 :tangle (eval f) :comments org :exports none
integer(c_int32_t) function qmckl_woodbury_3x3_doc &
(context, LDS, Dim, Updates, Updates_index, breakdown, Slater_inv, determinant) &
bind(C) result(info)
use, intrinsic :: iso_c_binding
implicit none
integer (c_int64_t) , intent(in) , value :: context
integer (c_int64_t) , intent(in) , value :: LDS
integer (c_int64_t) , intent(in) , value :: Dim
real (c_double ) , intent(in) :: Updates(3*Dim)
integer (c_int64_t) , intent(in) :: Updates_index(3)
real (c_double ) , intent(in) , value :: breakdown
real (c_double ) , intent(inout) :: Slater_inv(LDS*Dim)
real (c_double ) , intent(inout) :: determinant
integer(c_int32_t), external :: qmckl_woodbury_3x3_doc_f
info = qmckl_woodbury_3x3_doc_f &
(context, LDS, Dim, Updates, Updates_index, breakdown, Slater_inv, determinant)
end function qmckl_woodbury_3x3_doc
#+end_src
*** C headers (exposed in qmckl.h)
#+CALL: generate_c_header(table=qmckl_woodbury_3x3_args,rettyp=get_value("CRetType"),fname=get_value("Name"))
#+RESULTS:
#+begin_src c :tangle (eval h_func) :comments org
qmckl_exit_code qmckl_woodbury_3x3 (
const qmckl_context context,
const uint64_t LDS,
const uint64_t Dim,
const double* Updates,
const uint64_t* Updates_index,
const double breakdown,
double* Slater_inv,
double* determinant );
#+end_src
#+CALL: generate_c_header(table=qmckl_woodbury_3x3_args,rettyp=get_value("CRetType"),fname="qmckl_woodbury_3x3_hpc")
#+RESULTS:
#+begin_src c :tangle (eval h_func) :comments org
qmckl_exit_code qmckl_woodbury_3x3_hpc (
const qmckl_context context,
const uint64_t LDS,
const uint64_t Dim,
const double* Updates,
const uint64_t* Updates_index,
const double breakdown,
double* Slater_inv,
double* determinant );
#+end_src
#+CALL: generate_c_header(table=qmckl_woodbury_3x3_args,rettyp=get_value("CRetType"),fname="qmckl_woodbury_3x3_doc")
#+RESULTS:
#+begin_src c :tangle (eval h_func) :comments org
qmckl_exit_code qmckl_woodbury_3x3_doc (
const qmckl_context context,
const uint64_t LDS,
const uint64_t Dim,
const double* Updates,
const uint64_t* Updates_index,
const double breakdown,
double* Slater_inv,
double* determinant );
#+end_src
*** C sources
#+begin_src c :tangle (eval c) :comments org
qmckl_exit_code qmckl_woodbury_3x3_hpc(const qmckl_context context,
const uint64_t LDS,
const uint64_t Dim,
const double* __restrict Updates,
const uint64_t* __restrict Updates_index,
const double breakdown,
double* __restrict Slater_inv,
double* __restrict determinant) {
/*
C := S^{-1} * U, dim x 3
B := 1 + V * C, 3 x 3
D := V * S^{-1}, 3 x dim
*/
if (qmckl_context_check(context) == QMCKL_NULL_CONTEXT) {
return qmckl_failwith(context,
QMCKL_NULL_CONTEXT,
"qmckl_woodbury_3x3_hpc",
NULL);
}
const uint64_t row1 = (Updates_index[0] - 1);
const uint64_t row2 = (Updates_index[1] - 1);
const uint64_t row3 = (Updates_index[2] - 1);
// Compute C = (S^T)^{-1}U : Dim x 3
double __attribute__((aligned(8))) C[3 * Dim];
for (uint64_t i = 0; i < Dim; i++) {
C[i * 3] = 0;
C[i * 3 + 1] = 0;
C[i * 3 + 2] = 0;
IVDEP
ALIGNED
for (uint64_t k = 0; k < LDS; k++) {
C[i * 3] += Slater_inv[i * LDS + k] * Updates[k];
C[i * 3 + 1] += Slater_inv[i * LDS + k] * Updates[LDS + k];
C[i * 3 + 2] += Slater_inv[i * LDS + k] * Updates[2 * LDS + k];
}
}
// Compute B = 1 + VC : 3 x 3
const double B0 = C[row1 * 3] + 1;
const double B1 = C[row1 * 3 + 1];
const double B2 = C[row1 * 3 + 2];
const double B3 = C[row2 * 3];
const double B4 = C[row2 * 3 + 1] + 1;
const double B5 = C[row2 * 3 + 2];
const double B6 = C[row3 * 3];
const double B7 = C[row3 * 3 + 1];
const double B8 = C[row3 * 3 + 2] + 1;
// Check if determinant of inverted matrix is not zero
double det;
det = B0 * (B4 * B8 - B5 * B7) - B1 * (B3 * B8 - B5 * B6) +
B2 * (B3 * B7 - B4 * B6);
if (fabs(det) < breakdown) {
return QMCKL_FAILURE;
}
// Update det(S) when passed
if (determinant)
*determinant *= det;
// Compute B^{-1} with explicit formula for 2 x 2 inversion
double __attribute__((aligned(8))) Binv[9], idet = 1.0 / det;
Binv[0] = (B4 * B8 - B7 * B5) * idet;
Binv[1] = -(B1 * B8 - B7 * B2) * idet;
Binv[2] = (B1 * B5 - B4 * B2) * idet;
Binv[3] = -(B3 * B8 - B6 * B5) * idet;
Binv[4] = (B0 * B8 - B6 * B2) * idet;
Binv[5] = -(B0 * B5 - B3 * B2) * idet;
Binv[6] = (B3 * B7 - B6 * B4) * idet;
Binv[7] = -(B0 * B7 - B6 * B1) * idet;
Binv[8] = (B0 * B4 - B3 * B1) * idet;
// tmp = B^{-1}D : 2 x LDS
double __attribute__((aligned(8))) tmp[3 * LDS];
double* r1dim = &(Slater_inv[row1 * LDS]);
double* r2dim = &(Slater_inv[row2 * LDS]);
double* r3dim = &(Slater_inv[row3 * LDS]);
IVDEP
ALIGNED
for (uint64_t j = 0; j < LDS; j++) {
tmp[j] = Binv[0] * r1dim[j] + Binv[1] * r2dim[j] + Binv[2] * r3dim[j];
tmp[LDS + j] =
Binv[3] * r1dim[j] + Binv[4] * r2dim[j] + Binv[5] * r3dim[j];
tmp[2 * LDS + j] =
Binv[6] * r1dim[j] + Binv[7] * r2dim[j] + Binv[8] * r3dim[j];
}
// Compute (S^T)^{-1} - C * tmp : Dim x LDS
for (uint64_t i = 0; i < Dim; i++) {
IVDEP
ALIGNED
for (uint64_t j = 0; j < LDS; j++) {
Slater_inv[i * LDS + j] -= C[i * 3] * tmp[j];
Slater_inv[i * LDS + j] -= C[i * 3 + 1] * tmp[LDS + j];
Slater_inv[i * LDS + j] -= C[i * 3 + 2] * tmp[2 * LDS + j];
}
}
return QMCKL_SUCCESS;
}
#+end_src
#+NAME:woodbury_3x3_kernel_template
#+begin_src c
static inline qmckl_exit_code qmckl_woodbury_3x3_{Dim}(
const qmckl_context context,
const double* __restrict Updates,
const uint64_t* __restrict Updates_index,
const double breakdown,
double* __restrict Slater_inv,
double* __restrict determinant) {
/*
C := S^{-1} * U, dim x 3
B := 1 + V * C, 3 x 3
D := V * S^{-1}, 3 x dim
,*/
if (qmckl_context_check(context) == QMCKL_NULL_CONTEXT) {
return qmckl_failwith(context,
QMCKL_NULL_CONTEXT,
"qmckl_woodbury_3x3_{Dim}",
NULL);
}
const uint64_t row1 = (Updates_index[0] - 1);
const uint64_t row2 = (Updates_index[1] - 1);
const uint64_t row3 = (Updates_index[2] - 1);
// Compute C = (S^T)^{-1}U : {Dim} x 3
double __attribute__((aligned(8))) C[3 * {Dim}];
for (uint64_t i = 0; i < {Dim}; i++) {
C[i * 3] = 0;
C[i * 3 + 1] = 0;
C[i * 3 + 2] = 0;
IVDEP
ALIGNED
for (uint64_t k = 0; k < D{Dim}_P; k++) {
C[i * 3] += Slater_inv[i * D{Dim}_P + k] * Updates[k];
C[i * 3 + 1] += Slater_inv[i * D{Dim}_P + k] * Updates[D{Dim}_P + k];
C[i * 3 + 2] += Slater_inv[i * D{Dim}_P + k] * Updates[2 * D{Dim}_P + k];
}
}
// Compute B = 1 + VC : 3 x 3
const double B0 = C[row1 * 3] + 1;
const double B1 = C[row1 * 3 + 1];
const double B2 = C[row1 * 3 + 2];
const double B3 = C[row2 * 3];
const double B4 = C[row2 * 3 + 1] + 1;
const double B5 = C[row2 * 3 + 2];
const double B6 = C[row3 * 3];
const double B7 = C[row3 * 3 + 1];
const double B8 = C[row3 * 3 + 2] + 1;
// Check if determinant of B is not too close to zero
double det;
det = B0 * (B4 * B8 - B5 * B7) - B1 * (B3 * B8 - B5 * B6) +
B2 * (B3 * B7 - B4 * B6);
if (fabs(det) < breakdown) {
return QMCKL_FAILURE;
}
// Update det(Slater) if passed
if (determinant)
*determinant *= det;
// Compute B^{-1} with explicit formula for 3 x 3 inversion
double __attribute__((aligned(8))) Binv[9], idet = 1.0 / det;
Binv[0] = (B4 * B8 - B7 * B5) * idet;
Binv[1] = -(B1 * B8 - B7 * B2) * idet;
Binv[2] = (B1 * B5 - B4 * B2) * idet;
Binv[3] = -(B3 * B8 - B6 * B5) * idet;
Binv[4] = (B0 * B8 - B6 * B2) * idet;
Binv[5] = -(B0 * B5 - B3 * B2) * idet;
Binv[6] = (B3 * B7 - B6 * B4) * idet;
Binv[7] = -(B0 * B7 - B6 * B1) * idet;
Binv[8] = (B0 * B4 - B3 * B1) * idet;
// tmp = B^{-1}D : 3 x D{Dim}_P
double __attribute__((aligned(8))) tmp[3 * D{Dim}_P];
double* r1dim = &(Slater_inv[row1 * D{Dim}_P]);
double* r2dim = &(Slater_inv[row2 * D{Dim}_P]);
double* r3dim = &(Slater_inv[row3 * D{Dim}_P]);
IVDEP
ALIGNED
for (uint64_t j = 0; j < D{Dim}_P; j++) {
tmp[j] = Binv[0] * r1dim[j] + Binv[1] * r2dim[j] + Binv[2] * r3dim[j];
tmp[D{Dim}_P + j] =
Binv[3] * r1dim[j] + Binv[4] * r2dim[j] + Binv[5] * r3dim[j];
tmp[2 * D{Dim}_P + j] =
Binv[6] * r1dim[j] + Binv[7] * r2dim[j] + Binv[8] * r3dim[j];
}
// Compute (S^T)^{-1} - C * tmp : {Dim} x D{Dim}_P
for (uint64_t i = 0; i < {Dim}; i++) {
IVDEP
ALIGNED
for (uint64_t j = 0; j < D{Dim}_P; j++) {
Slater_inv[i * D{Dim}_P + j] -= C[i * 3] * tmp[j];
Slater_inv[i * D{Dim}_P + j] -= C[i * 3 + 1] * tmp[D{Dim}_P + j];
Slater_inv[i * D{Dim}_P + j] -= C[i * 3 + 2] * tmp[2 * D{Dim}_P + j];
}
}
return QMCKL_SUCCESS;
}
#+end_src
#+NAME:woodbury_3x3_kernel_generator
#+begin_src python :noweb yes :exports none
text="""
<<woodbury_3x3_kernel_template>>
"""
result = []
for Dim in <<kernel_generator_range>>:
Dim=str(Dim)
result.append(text.replace("{Dim}",Dim) )
return ''.join(result)
#+end_src
#+NAME:woodbury_3x3_switch-case_generator
#+begin_src python :noweb yes :exports none
text="""
case {Dim}:
return qmckl_woodbury_3x3_{Dim}(context,
Updates,
Updates_index,
breakdown,
Slater_inv,
determinant);"""
result = []
for Dim in <<kernel_generator_range>>:
Dim=str(Dim)
result.append(text.replace("{Dim}",Dim) )
return ''.join(result)
#+end_src
#+begin_src c :tangle (eval c) :comments org :noweb yes
<<woodbury_3x3_kernel_generator()>>
#+end_src
#+begin_src c :tangle (eval c) :comments org :noweb yes
qmckl_exit_code qmckl_woodbury_3x3(const qmckl_context context,
const uint64_t LDS,
const uint64_t Dim,
const double* Updates,
const uint64_t* Updates_index,
const double breakdown,
double* Slater_inv,
double* determinant) {
if (qmckl_context_check(context) == QMCKL_NULL_CONTEXT) {
return qmckl_failwith(
context,
QMCKL_NULL_CONTEXT,
"qmckl_woodbury_3x3",
NULL);
}
#ifdef HAVE_HPC
if (LDS == (1+(Dim-1)/SIMD_LENGTH)*SIMD_LENGTH) { // Most cases
switch (Dim) {
<<woodbury_3x3_switch-case_generator()>>
}
}
else { // Updating smaller sub-matrix
return qmckl_woodbury_3x3_hpc(
context,
LDS,
Dim,
Updates,
Updates_index,
breakdown,
Slater_inv,
determinant);
}
#else
return qmckl_woodbury_3x3_doc(
context,
LDS,
Dim,
Updates,
Updates_index,
breakdown,
Slater_inv,
determinant);
// return qmckl_woodbury_3x3_hpc(
// context,
// LDS,
// Dim,
// Updates,
// Updates_index,
// breakdown,
// Slater_inv,
// determinant);
#endif
return QMCKL_FAILURE;
}
#+end_src
*** Fortran interfaces (exposed in qmckl_f.F90)
:PROPERTIES:
:Name: qmckl_woodbury_3x3
:CRetType: qmckl_exit_code
:FRetType: qmckl_exit_code
:END:
#+CALL: generate_f_interface(table=qmckl_woodbury_3x3_args,rettyp=get_value("FRetType"),fname=get_value("Name"))
#+RESULTS:
#+begin_src f90 :tangle (eval fh_func) :comments org :exports none
interface
integer(c_int32_t) function qmckl_woodbury_3x3 &
(context, LDS, Dim, Updates, Updates_index, breakdown, Slater_inv, determinant) &
bind(C)
use, intrinsic :: iso_c_binding
import
implicit none
integer (c_int64_t) , intent(in) , value :: context
integer (c_int64_t) , intent(in) , value :: LDS
integer (c_int64_t) , intent(in) , value :: Dim
real (c_double ) , intent(in) :: Updates(3*Dim)
integer (c_int64_t) , intent(in) :: Updates_index(3)
real (c_double ) , intent(in) , value :: breakdown
real (c_double ) , intent(inout) :: Slater_inv(LDS*Dim)
real (c_double ) , intent(inout) :: determinant
end function qmckl_woodbury_3x3
end interface
#+end_src
#+CALL: generate_f_interface(table=qmckl_woodbury_3x3_args,rettyp=get_value("FRetType"),fname="qmckl_woodbury_3x3_hpc")
#+RESULTS:
#+begin_src f90 :tangle (eval fh_func) :comments org :exports none
interface
integer(c_int32_t) function qmckl_woodbury_3x3_hpc &
(context, LDS, Dim, Updates, Updates_index, breakdown, Slater_inv, determinant) &
bind(C)
use, intrinsic :: iso_c_binding
import
implicit none
integer (c_int64_t) , intent(in) , value :: context
integer (c_int64_t) , intent(in) , value :: LDS
integer (c_int64_t) , intent(in) , value :: Dim
real (c_double ) , intent(in) :: Updates(3*Dim)
integer (c_int64_t) , intent(in) :: Updates_index(3)
real (c_double ) , intent(in) , value :: breakdown
real (c_double ) , intent(inout) :: Slater_inv(LDS*Dim)
real (c_double ) , intent(inout) :: determinant
end function qmckl_woodbury_3x3_hpc
end interface
#+end_src
#+CALL: generate_f_interface(table=qmckl_woodbury_3x3_args,rettyp=get_value("FRetType"),fname="qmckl_woodbury_3x3_doc")
#+RESULTS:
#+begin_src f90 :tangle (eval fh_func) :comments org :exports none
interface
integer(c_int32_t) function qmckl_woodbury_3x3_doc &
(context, LDS, Dim, Updates, Updates_index, breakdown, Slater_inv, determinant) &
bind(C)
use, intrinsic :: iso_c_binding
import
implicit none
integer (c_int64_t) , intent(in) , value :: context
integer (c_int64_t) , intent(in) , value :: LDS
integer (c_int64_t) , intent(in) , value :: Dim
real (c_double ) , intent(in) :: Updates(3*Dim)
integer (c_int64_t) , intent(in) :: Updates_index(3)
real (c_double ) , intent(in) , value :: breakdown
real (c_double ) , intent(inout) :: Slater_inv(LDS*Dim)
real (c_double ) , intent(inout) :: determinant
end function qmckl_woodbury_3x3_doc
end interface
#+end_src
*** Performance
This function is most efficient when used in cases where there are only 3 rank-1 updates and
it is sure they will not result in a singular matrix.
*** Tests
#+begin_src c :tangle (eval c_test)
assert(Updates3 != NULL);
assert(Updates_index3 != NULL);
assert(Slater_inv3_1 != NULL);
det = -1.23743195512859e-09;
rc = qmckl_woodbury_3x3(context, LDS, Dim, Updates3, Updates_index3, breakdown, Slater_inv3_1, &det);
assert(fabs(det - 1.602708950725074e-10) < 1e-15);
for (unsigned int i = 0; i < Dim; i++) {
for (unsigned int j = 0; j < Dim; j++) {
res[i * Dim + j] = 0;
for (unsigned int k = 0; k < Dim; k++) {
res[i * Dim + j] += Slater3[i * Dim + k] * Slater_inv3_1[k * LDS + j];
}
}
}
rc = QMCKL_SUCCESS;
for (unsigned int i = 0; i < Dim; i++) {
for (unsigned int j = 0; j < Dim; j++) {
if (i == j && fabs(res[i * Dim + j] - 1) > tolerance) {
rc = QMCKL_FAILURE;
}
if (i != j && fabs(res[i * Dim + j]) > tolerance) {
rc = QMCKL_FAILURE;
}
}
}
assert(rc == QMCKL_SUCCESS);
#+end_src
* Sherman-Morrison with Slagel Splitting
** ~qmckl_sm_splitting~
:PROPERTIES:

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