Merge pull request #4 from fortran-fans/add_hybrd_interface

Add hybrd1 interface and example.

Author: certik

README.rst

@@ -21,6 +21,26 @@ of the Jacobian matrix with the functions.
 
 Jorge Moré, Burt Garbow, and Ken Hillstrom at Argonne National Laboratory.
 
+Build with `fortran-lang/fpm <https://github.com/fortran-lang/fpm>`_
+--------------------------------------------------------------------
+
+Fortran Package Manager (fpm) is a great package manager and build system for Fortran.
+
+You can build using provided ``fpm.toml``:
+
+.. code-block:: bash
+
+    fpm build 
+    fpm run --example <example_name, see ``fpm.toml``>
+
+
+To use ``minpack`` within your fpm project, add the following to your ``fpm.toml`` file:
+
+.. code-block:: toml 
+
+    [dependencies]
+    minpack = { git="https://github.com/certik/minpack.git" }
+
 Documentation
 -------------
 

examples/CMakeLists.txt

@@ -1,5 +1,8 @@
 include_directories(${PROJECT_BINARY_DIR}/src)
 
+add_executable(example_hybrd1 example_hybrd1.f90)
+target_link_libraries(example_hybrd1 minpack)
+
 add_executable(example_lmder1 example_lmder1.f90)
 target_link_libraries(example_lmder1 minpack)
 

examples/example_hybrd1.f90

@@ -0,0 +1,74 @@
+!> the problem is to determine the values of x(1), x(2), ..., x(9),
+!>  which solve the system of tridiagonal equations.
+!>
+!>  (3-2*x(1))*x(1)           -2*x(2)                   = -1
+!>  -x(i-1) + (3-2*x(i))*x(i)         -2*x(i+1) = -1, i=2-8
+!>  -x(8) + (3-2*x(9))*x(9) = -1
+program example_hybrd1
+
+    use minpack, only: hybrd1
+    implicit none
+    integer j, n, info, lwa, nwrite
+    double precision tol, fnorm
+    double precision x(9), fvec(9), wa(180)
+    double precision enorm, dpmpar
+
+    data nwrite/6/
+
+    n = 9
+
+    !> The following starting values provide a rough solution.
+    do j = 1, 9
+        x(j) = -1.d0
+    end do
+
+    lwa = 180
+    tol = dsqrt(dpmpar(1))
+
+    call hybrd1(fcn, n, x, fvec, tol, info, wa, lwa)
+    fnorm = enorm(n, fvec)
+    write (nwrite, 1000) fnorm, info, (x(j), j=1, n)
+
+1000 format(5x, "FINAL L2 NORM OF THE RESIDUALS", d15.7// &
+           5x, "EXIT PARAMETER", 16x, i10// &
+           5x, "FINAL APPROXIMATE SOLUTION"// &
+           (5x, 3d15.7))
+
+    !> Results obtained with different compilers or machines
+    !> may be slightly different.
+    !>
+    !>> FINAL L2 NORM OF THE RESIDUALS  0.1192636D-07
+    !>>
+    !>> EXIT PARAMETER                         1
+    !>>
+    !>> FINAL APPROXIMATE SOLUTION
+    !>>
+    !>>  -0.5706545D+00 -0.6816283D+00 -0.7017325D+00
+    !>>  -0.7042129D+00 -0.7013690D+00 -0.6918656D+00
+    !>>  -0.6657920D+00 -0.5960342D+00 -0.4164121D+00
+
+contains
+
+    !> subroutine fcn for hybrd1 example.
+    subroutine fcn(n, x, fvec, iflag)
+
+        implicit none
+        integer n, iflag
+        double precision x(n), fvec(n)
+
+        integer k
+        double precision one, temp, temp1, temp2, three, two, zero
+        data zero, one, two, three/0.0d0, 1.0d0, 2.0d0, 3.0d0/
+
+        do k = 1, n
+            temp = (three - two*x(k))*x(k)
+            temp1 = zero
+            if (k /= 1) temp1 = x(k - 1)
+            temp2 = zero
+            if (k /= n) temp2 = x(k + 1)
+            fvec(k) = temp - temp1 - two*temp2 + one
+        end do
+
+    end subroutine fcn
+
+end program example_hybrd1

fpm.toml

@@ -17,6 +17,11 @@ auto-examples = false
 [install]
 library = false
 
+[[ example ]]
+name = "example_hybrd1"
+source-dir = "examples"
+main = "example_hybrd1.f90"
+
 [[ example ]]
 name = "example_lmder1"
 source-dir = "examples"

src/minpack.f90

@@ -12,6 +12,21 @@ double precision function enorm(n,x)
     double precision x(n)
     end function
 
+    !> The purpose of `hybrd1` is to find a zero of a system of
+    !>  n nonlinear functions in n variables by a modification
+    !>  of the powell hybrid method.
+    subroutine hybrd1(fcn,n,x,fvec,tol,info,wa,lwa)
+        integer n,info,lwa
+        double precision tol
+        double precision x(n),fvec(n),wa(lwa)
+        interface
+            subroutine fcn(n,x,fvec,iflag)
+                integer n,iflag
+                double precision x(n),fvec(n)
+            end subroutine fcn
+        end interface
+    end subroutine hybrd1
+
     subroutine lmder1(fcn,m,n,x,fvec,fjac,ldfjac,tol,info,ipvt,wa,lwa)
     integer m,n,ldfjac,info,lwa
     integer ipvt(n)