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+! Copyright 2019 Wojciech Kosior
+  
+! This is free and unencumbered software released into the public domain.
+
+! Anyone is free to copy, modify, publish, use, compile, sell, or
+! distribute this software, either in source code form or as a compiled
+! binary, for any purpose, commercial or non-commercial, and by any
+! means.
+
+! In jurisdictions that recognize copyright laws, the author or authors
+! of this software dedicate any and all copyright interest in the
+! software to the public domain. We make this dedication for the benefit
+! of the public at large and to the detriment of our heirs and
+! successors. We intend this dedication to be an overt act of
+! relinquishment in perpetuity of all present and future rights to this
+! software under copyright law.
+
+! THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+! EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+! MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+! IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
+! OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+! ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+! OTHER DEALINGS IN THE SOFTWARE.
+
+! For more information, please refer to <http://unlicense.org/>
+
+MODULE blockmat
+  IMPLICIT none
+  PRIVATE
+
+  integer, public :: blocksize = 25
+  
+  PUBLIC :: blockmull
+  PRIVATE :: blockmull_4, blockmull_8, blockmull_16
+  
+  INTERFACE blockmull
+     procedure blockmull_4, blockmull_8, blockmull_16
+  END INTERFACE blockmull
+
+CONTAINS
+
+  FUNCTION blockmull_4(A, B) result(C)
+    IMPLICIT none
+    real(kind=4), intent(in), dimension(1:,1:) :: A, B
+    real(kind=4), dimension(size(A, 1), size(B, 2)) :: C
+    integer :: i, ii, ii_max, iiend, j, k, kk, kk_max, kkend
+
+    C = 0
+    
+    kk_max = (size(A, 2) / blocksize) * blocksize + 1
+    ii_max = (size(A, 1) / blocksize) * blocksize + 1
+    
+    DO kk = 1, kk_max, blocksize
+       IF (kk .lt. kk_max) kkend = kk + blocksize - 1
+       IF (kk .eq. kk_max) THEN
+          kkend = size(A, 2)
+          IF (kk .gt. kkend) EXIT
+       END IF
+
+       DO ii = 1, ii_max, blocksize
+          IF (ii .lt. ii_max) iiend = ii + blocksize - 1
+          IF (ii .eq. ii_max) THEN
+             iiend = size(A, 1)
+             IF (ii .gt. iiend) EXIT
+          END IF
+
+          DO j = 1, size(B, 2)
+             DO k = kk, kkend
+
+                C(ii:iiend,j) = C(ii:iiend,j) + A(ii:iiend,k) * B(k,j)
+             END DO
+          END DO
+       END DO
+    END DO
+
+  END FUNCTION blockmull_4  
+
+  FUNCTION blockmull_8(A, B) result(C)
+    IMPLICIT none
+    real(kind=8), intent(in), dimension(1:,1:) :: A, B
+    real(kind=8), dimension(size(A, 1), size(B, 2)) :: C
+    integer :: i, ii, ii_max, iiend, j, k, kk, kk_max, kkend
+
+    C = 0
+    
+    kk_max = (size(A, 2) / blocksize) * blocksize + 1
+    ii_max = (size(A, 1) / blocksize) * blocksize + 1
+    
+    DO kk = 1, kk_max, blocksize
+       IF (kk .lt. kk_max) kkend = kk + blocksize - 1
+       IF (kk .eq. kk_max) THEN
+          kkend = size(A, 2)
+          IF (kk .gt. kkend) EXIT
+       END IF
+
+       DO ii = 1, ii_max, blocksize
+          IF (ii .lt. ii_max) iiend = ii + blocksize - 1
+          IF (ii .eq. ii_max) THEN
+             iiend = size(A, 1)
+             IF (ii .gt. iiend) EXIT
+          END IF
+
+          DO j = 1, size(B, 2)
+             DO k = kk, kkend
+
+                C(ii:iiend,j) = C(ii:iiend,j) + A(ii:iiend,k) * B(k,j)
+             END DO
+          END DO
+       END DO
+    END DO
+
+  END FUNCTION blockmull_8  
+
+  FUNCTION blockmull_16(A, B) result(C)
+    IMPLICIT none
+    real(kind=16), intent(in), dimension(1:,1:) :: A, B
+    real(kind=16), dimension(size(A, 1), size(B, 2)) :: C
+    integer :: i, ii, ii_max, iiend, j, k, kk, kk_max, kkend
+
+    C = 0
+    
+    kk_max = (size(A, 2) / blocksize) * blocksize + 1
+    ii_max = (size(A, 1) / blocksize) * blocksize + 1
+    
+    DO kk = 1, kk_max, blocksize
+       IF (kk .lt. kk_max) kkend = kk + blocksize - 1
+       IF (kk .eq. kk_max) THEN
+          kkend = size(A, 2)
+          IF (kk .gt. kkend) EXIT
+       END IF
+       
+       DO ii = 1, ii_max, blocksize
+          IF (ii .lt. ii_max) iiend = ii + blocksize - 1
+          IF (ii .eq. ii_max) THEN
+             iiend = size(A, 1)
+             IF (ii .gt. iiend) EXIT
+          END IF
+          
+          DO j = 1, size(B, 2)
+             DO k = kk, kkend
+
+                C(ii:iiend,j) = C(ii:iiend,j) + A(ii:iiend,k) * B(k,j)
+             END DO
+          END DO
+       END DO
+    END DO
+
+  END FUNCTION blockmull_16  
+
+END MODULE blockmat