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Replace BLAS function WDOT with the Fortran DOT_PRODUCT intrinsic function #143

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Merged
yantosca merged 1 commit into from
Oct 31, 2025
Merged

Replace BLAS function WDOT with the Fortran DOT_PRODUCT intrinsic function #143

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2 changes: 1 addition & 1 deletion CHANGELOG.md
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Expand Up @@ -29,7 +29,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0

### Removed
- Removed C-I tests on Microsoft Azure Dev Pipelines
- Replaced BLAS functions (`WAXPY`, `WCOPY`, `WSCAL`, `WADD`, `WLAMCH`) with pure F90 code from `int/*.f90` integrators (thanks to AI for the help)
- Replaced BLAS functions (`WAXPY`, `WCOPY`, `WSCAL`, `WADD`, `WLAMCH`, `WDOT`) with pure F90 code from `int/*.f90` integrators (thanks to AI for the help)

## [3.3.0] - 2025-07-17
### Added
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65 changes: 3 additions & 62 deletions util/blas.f90
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Expand Up @@ -20,70 +20,11 @@
!%%% (5) WLAMCH_ADD %%%
!%%% (6) SET2ZERO %%%
!%%% (7) WADD %%%
!%%% (8) WDOT %%%
!%%% %%%
!%%% @yantosca, 17 Oct 2025 %%%
!%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

!--------------------------------------------------------------
KPP_REAL FUNCTION WDOT (N, DX, incX, DY, incY)
!--------------------------------------------------------------
! dot produce: wdot = x(1:N)*y(1:N)
! only for incX=incY=1
! after BLAS
! replace this by the function from the optimized BLAS implementation:
! CALL SDOT(N,X,1,Y,1) or CALL DDOT(N,X,1,Y,1)
!--------------------------------------------------------------
! USE messy_mecca_kpp_Precision
!--------------------------------------------------------------
IMPLICIT NONE
INTEGER :: N, incX, incY
KPP_REAL :: DX(N), DY(N)

INTEGER :: i, IX, IY, M, MP1, NS

WDOT = 0.0D0
IF (N .LE. 0) RETURN
IF (incX .EQ. incY) IF (incX-1) 5,20,60
!
! Code for unequal or nonpositive increments.
!
5 IX = 1
IY = 1
IF (incX .LT. 0) IX = (-N+1)*incX + 1
IF (incY .LT. 0) IY = (-N+1)*incY + 1
DO i = 1,N
WDOT = WDOT + DX(IX)*DY(IY)
IX = IX + incX
IY = IY + incY
END DO
RETURN
!
! Code for both increments equal to 1.
!
! Clean-up loop so remaining vector length is a multiple of 5.
!
20 M = MOD(N,5)
IF (M .EQ. 0) GO TO 40
DO i = 1,M
WDOT = WDOT + DX(i)*DY(i)
END DO
IF (N .LT. 5) RETURN
40 MP1 = M + 1
DO i = MP1,N,5
WDOT = WDOT + DX(i)*DY(i) + DX(i+1)*DY(i+1) + DX(i+2)*DY(i+2) + &
DX(i+3)*DY(i+3) + DX(i+4)*DY(i+4)
END DO
RETURN
!
! Code for equal, positive, non-unit increments.
!
60 NS = N*incX
DO i = 1,NS,incX
WDOT = WDOT + DX(i)*DY(i)
END DO

END FUNCTION WDOT

!--------------------------------------------------------------
SUBROUTINE WGEFA(N,A,Ipvt,info)
!--------------------------------------------------------------
Expand Down Expand Up @@ -203,14 +144,14 @@ SUBROUTINE WGESL(Trans,N,A,Ipvt,b)

! first solve trans(U)*y = b
DO k = 1, n
t = WDOT(k-1,a(1,k),1,b(1),1)
t = DOT_PRODUCT( a(1:k-1, k), b(1:k-1) )
b(k) = (b(k) - t)/a(k,k)
END DO
! now solve trans(L)*x = y
IF (n >= 2) THEN
DO kb = 1, n-1
k = n - kb
b(k) = b(k) + WDOT(n-k,a(k+1,k),1,b(k+1),1)
b(k) = b(k) + DOT_PRODUCT( a(k+1:n, k), b(k+1:n) )
l = Ipvt(k)
IF (l /= k) THEN
t = b(l); b(l) = b(k); b(k) = t
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