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authorSébastien Dailly <sebastien@chimrod.com>2021-02-05 09:08:39 +0100
committerSébastien Dailly <sebastien@dailly.me>2022-02-07 14:39:30 +0100
commit561d0f0155f4906d90eb7e73a3ff9cb28909126f (patch)
tree9a606c2d7832272ea33d7052512a5fa59805d582 /shapes/matrix/Matrix.ml
parent86ec559f913c389e8dc055b494630f21a45e039b (diff)
Update project structure
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-open Order
-
-module Order = Order
-
-(*************** Exceptions ***************)
-
-exception NonSquare
-exception ImproperDimensions
-
-(* Functor so we can Abstract away! *)
-module MakeMatrix (C: EltsI.ORDERED_AND_OPERATIONAL) :
- (MatrixI.MATRIX with type elt = C.t) =
-struct
-
-
- (*************** End Exceptions ***************)
-
- (*************** Types ***************)
-
- type elt = C.t
-
- (* A matrix is a pair of dimension (n x p) and a array of arrays
- * the first array is the row (n) and the second the column (p) *)
- type matrix = (int * int) * (elt array array)
-
- (*************** End Types ***************)
-
- (*************** Base Functions ***************)
-
- (* catching negative dimensions AND 0 dimensions and too large
- * of a dimension so we don't have to worry about it later *)
- let empty (rows: int) (columns: int) : matrix =
- if rows > 0 && columns > 0 then
- try
- let m = Array.make_matrix rows columns C.zero in ((rows,columns),m)
- with _ ->
- raise ImproperDimensions
- else (* dimension is negative or 0 *)
- raise ImproperDimensions
-
- (*************** End Base Functions ***************)
-
- (*************** Helper Functions ***************)
-
- (* get's the nth row of a matrix and returns (r, row) where r is the length
- * of the row and row is a COPY of the original row. For example, calling
- * calling get_row m 1 will return (3, |1 3 4 |)
- * ________
- * m = | 1 3 4 |
- * |*2 5 6 |
- *)
- (* aside: we don't check whether n < 1 because of our matrix invariant *)
- let get_row (((n,p),m): matrix) (row: int) : int * elt array =
- if row <= n then
- let row' = Array.map (fun x -> x) m.(row - 1) in
- (p, row')
- else
- raise (Failure "Row out of bounds.")
-
- (* similar to get_row. For m, get_column m 1 will return (2, |1 2|) *)
- let get_column (((n,p),m): matrix) (column: int) : int * elt array =
- if column <= p then
- begin
- let column' = Array.make n C.zero in
- for i = 0 to n - 1 do
- column'.(i) <- m.(i).(column - 1)
- done;
- (n, column')
- end
- else
- raise (Failure "Column out of bounds.")
-
- (* sets the nth row of the matrix m to the specified array a.
- * This is done IN-PLACE. Therefore the function returns unit. You should
- * nonetheless enfore immutability whenever possible. For a clarification on
- * what nth row means, look at comment for get_row above. *)
- let set_row (((n, p), m): matrix) (row: int) (a: elt array) : unit =
- if row <= n then
- begin
- assert(Array.length a = p);
- for i = 0 to p - 1 do
- m.(row - 1).(i) <- a.(i)
- done;
- end
- else
- raise (Failure "Row out of bounds.")
-
- (* Similar to set_row but sets the nth column instead *)
- let set_column (((n,p),m): matrix) (column: int) (a: elt array) : unit =
- if column <= p then
- begin
- assert(Array.length a = n);
- for i = 0 to n - 1 do
- m.(i).(column - 1) <- a.(i)
- done;
- end
- else
- raise (Failure "Column out of bounds.")
-
- (* returns the ij-th element of a matrix (not-zero indexed) *)
- let get_elt (((n,p),m): matrix) ((i,j): int*int) : elt =
- if i <= n && j <= p then
- m.(i - 1).(j - 1)
- else
- raise ImproperDimensions
-
- (* Changes the i,j-th element of a matrix to e. Is not zero-indexed, and
- * changes the matrix in place *)
- let set_elt (((n,p),m): matrix) ((i,j): int*int) (e: elt) : unit =
- if i <= n && j <= p then
- m.(i - 1).(j - 1) <- e
- else
- raise ImproperDimensions
-
- (* similar to map, but applies to function to the entire matrix
- * Returns a new matrix *)
- let map (f: elt -> elt) (mat: matrix) : matrix =
- let (dim,m) = mat in
- (dim, Array.map (Array.map f) m)
-
- (* Just some wrapping of Array.iter made for Matrices! *)
- let iter (f: elt -> unit) (mat: matrix) : unit =
- let _, m = mat in
- Array.iter (Array.iter f) m
-
- (* Just some wrapping of Array.iteri. Useful for pretty
- * printing matrix. The index is (i,j). NOT zero-indexed *)
- let iteri (f: int -> int -> elt -> unit) (mat: matrix) : unit =
- let _, m = mat in
- Array.iteri (fun i row -> Array.iteri (fun j e -> f i j e) row) m
-
- (* folds over each row using base case u and function f *)
- (* could be a bit more efficient? *)
- let reduce (f: 'a -> elt -> 'a) (u: 'a) (((p,q),m): matrix) : 'a =
- let total = ref u in
- for i = 0 to p - 1 do
- for j = 0 to q - 1 do
- total := f (!total) m.(i).(j)
- done;
- done;
- !total
-
- let fold_row ~(f: elt array -> 'b) ((_,m): matrix) : 'b list =
-
- let call_row acc v = (f v)::acc in
- Array.fold_left call_row [] m
- |> List.rev
-
-
-
-
- (* given two arrays, this will calculate their dot product *)
- (* It seems a little funky, but this is done for efficiency's sake.
- * In short, it tries to multiply each element by it's respective
- * element until the one array is indexed out of bounds. If the
- * other array is also out of bounds, then it returns their value.
- * Otherwise, the arrays were the wrong size and raises ImproperDimension
-
- THE ABOVE COMMENT HAS NOT BEEN IMPLEMENTED
-
- Instead we calculate the length before starting
- *)
- let dot (v1: elt array) (v2: elt array) : elt =
- let rec dotting (i: int) (total: elt) : elt =
- if i = 0 then total
- else
- let curr = C.multiply v1.(i-1) v2.(i-1) in
- dotting (i - 1) (C.add curr total) in
- let len1, len2 = Array.length v1, Array.length v2 in
- if len1 = len2 then dotting len1 C.zero
- else raise ImproperDimensions
-
- (* function to expose the dimensions of a matrix *)
- let get_dimensions (m: matrix) : (int * int) =
- let ((x,y), _) = m in (x,y)
-
- (*************** End Helper Functions ***************)
-
-
- (*************** Primary Matrix Functions ***************)
-
- (* scales a matrix by the appropriate factor *)
- let scale (m: matrix) (sc: elt) : matrix = map (C.multiply sc) m
-
- (* Generates a matrix from a list of lists. The inners lists are the rows *)
- let from_list (lsts : elt list list) : matrix =
- let check_length (length: int) (lst: elt list) : int =
- if List.length lst = length then length
- else raise ImproperDimensions in
- let p = List.length lsts in
- match lsts with
- | [] -> raise ImproperDimensions
- | hd::tl ->
- let len = List.length hd in
- if List.fold_left check_length len tl = len then
- ((p,len),Array.map Array.of_list (Array.of_list lsts))
- else
- raise ImproperDimensions
-
- (* Generates a matrix from a list of lists. The inners lists are the rows *)
- let from_array (arrs : elt array array) : matrix =
- let check_length (length: int) (arr: elt array) : unit =
- if Array.length arr = length then ()
- else raise ImproperDimensions in
- let p = Array.length arrs in
- match Array.length arrs with
- | 0 -> raise ImproperDimensions
- | _ ->
- let len = Array.length (Array.get arrs 0) in
- Array.iter (check_length len) arrs;
- ((p, len), arrs)
-
- (* Adds two matrices. They must have the same dimensions *)
- let add ((dim1,m1): matrix) ((dim2,m2): matrix) : matrix =
- if dim1 = dim2 then
- let n, p = dim1 in
- let (dim', sum_m) = empty n p in
- for i = 0 to n - 1 do
- for j = 0 to p - 1 do
- sum_m.(i).(j) <- C.add m1.(i).(j) m2.(i).(j)
- done;
- done;
- (dim',sum_m)
- else
- raise ImproperDimensions
-
-
- (* Multiplies two matrices. If the matrices have dimensions m x n and p x q, n
- * and p must be equal, and the resulting matrix will have dimension n x q *)
- let mult (matrix1: matrix) (matrix2: matrix) : matrix =
- let ((m,n), _), ((p,q), _) = matrix1, matrix2 in
- if n = p then
- let (dim, result) = empty m q in
- for i = 0 to m - 1 do
- for j = 0 to q - 1 do
- let (_,row), (_,column) = get_row matrix1 (i + 1),
- get_column matrix2 (j + 1) in
- result.(i).(j) <- dot row column
- done;
- done;
- (dim,result)
- else
- raise ImproperDimensions
-
- (*************** Helper Functions for Row Reduce ***************)
-
- (*
- (* returns the index of the first non-zero elt in an array*)
- let zero (arr: elt array) : int option =
- let index = ref 1 in
- let empty (i: int option) (e: elt) : int option =
- match i, C.compare e C.zero with
- | None, Equal -> (index := !index + 1; None)
- | None, _ -> Some (!index)
- | _, _ -> i in
- Array.fold_left empty None arr
-
- (* returns the the location of the nth non-zero
- * element in the matrix. Scans column wise. So the nth non-zero element is
- * the FIRST non-zero element in the nth non-zero column *)
- let nth_nz_location (m: matrix) (_: int): (int*int) option =
- let ((n,p), _) = m in
- let rec check_col (to_skip: int) (j: int) =
- if j <= p then
- let (_,col) = get_column m j in
- match zero col with
- | None -> check_col to_skip (j + 1)
- | Some i ->
- if to_skip = 0 then
- Some (i,j)
- else (* we want a later column *)
- check_col (to_skip - 1) (j + 1)
- else None in
- check_col (n - 1) 1
-
- (* returns the the location of the first
- * non-zero and non-one elt. Scans column wise, from
- * left to right. Basically, it ignores columns
- * that are all zero or that *)
- let fst_nz_no_loc (m: matrix): (int*int) option =
- let ((_, p), _) = m in
- let rec check_col (j: int) =
- if j <= p then
- let (_,col) = get_column m j in
- match zero col with
- | None -> check_col (j + 1)
- | Some i ->
- match C.compare col.(i-1) C.one with
- | Equal -> check_col (j + 1)
- | _ -> Some (i,j)
- else None in
- check_col 1
- *)
-
- (* Compares two elements in an elt array and returns the greater and its
- * index. Is a helper function for find_max_col_index *)
- let compare_helper (e1: elt) (e2: elt) (ind1: int) (ind2: int) : (elt*int) =
- match C.compare e1 e2 with
- | Equal -> (e2, ind2)
- | Greater -> (e1, ind1)
- | Less -> (e2, ind2)
-
- (* Finds the element with the greatest absolute value in a column. Is not
- * 0-indexed. If two elements are both the maximum value, returns the one with
- * the lowest index. Returns None if this element is zero (if column is all 0)
- *)
- let find_max_col_index (array1: elt array) (start_index: int) : int option =
- let rec find_index (max_index: int) (curr_max: elt) (curr_index: int)
- (arr: elt array) =
- if curr_index = Array.length arr then
- (if curr_max = C.zero then None
- else Some (max_index+1)) (* Arrays are 0-indexed but matrices aren't *)
- else
- (match C.compare arr.(curr_index) C.zero with
- | Equal -> find_index max_index curr_max (curr_index+1) arr
- | Greater ->
- (let (el, index) = compare_helper (arr.(curr_index))
- curr_max curr_index max_index in
- find_index index el (curr_index+1) arr)
- | Less ->
- (let abs_curr_elt = C.subtract C.zero arr.(curr_index) in
- let (el, index) = compare_helper abs_curr_elt curr_max curr_index
- max_index in
- find_index index el (curr_index+1) arr))
- in
- find_index 0 C.zero (start_index -1) array1
-
- (* Basic row operations *)
- (* Scales a row by sc *)
- let scale_row (m: matrix) (num: int) (sc: elt) : unit =
- let (_, row) = get_row m num in
- let new_row = Array.map (C.multiply sc) row in
- set_row m num new_row
-
- (* Swaps two rows of a matrix *)
- let swap_row (m: matrix) (r1: int) (r2: int) : unit =
- let (len1, row1) = get_row m r1 in
- let (len2, row2) = get_row m r2 in
- let _ = assert (len1 = len2) in
- let _ = set_row m r1 row2 in
- let _ = set_row m r2 row1 in
- ()
-
- (* Subtracts a multiple of r2 from r1 *)
- let sub_mult (m: matrix) (r1: int) (r2: int) (sc: elt) : unit =
- let (len1, row1) = get_row m r1 in
- let (len2, row2) = get_row m r2 in
- let _ = assert (len1 = len2) in
- for i = 0 to len1 - 1 do (* Arrays are 0-indexed *)
- row1.(i) <- C.subtract row1.(i) (C.multiply sc row2.(i))
- done;
- set_row m r1 row1
-
- (*************** End Helper Functions for Row Reduce ***************)
-
- (* Returns the row reduced form of a matrix. Is not done in place, but creates
- * a new matrix *)
- let row_reduce (mat: matrix) : matrix =
- let[@tailcall] rec row_reduce_h (n_row: int) (n_col: int) (mat2: matrix) : unit =
- let ((num_row, _), _) = mat2 in
- if (n_col = num_row + 1) then ()
- else
- let (_,col) = get_column mat2 n_col in
- match find_max_col_index col n_row with
- | None (* Column all 0s *) -> row_reduce_h n_row (n_col+1) mat2
- | Some index ->
- begin
- swap_row mat2 index n_row;
- let pivot = get_elt mat2 (n_row, n_col) in
- scale_row mat2 (n_row) (C.divide C.one pivot);
- for i = 1 to num_row do
- if i <> n_row then sub_mult mat2 i n_row (get_elt mat2 (i,n_col))
- done;
- row_reduce_h (n_row+1) (n_col+1) mat2
- end
- in
- (* Copies the matrix *)
- let ((n,p),m) = mat in
- let (dim,mat_cp) = empty n p in
- for i = 0 to n - 1 do
- for j = 0 to p - 1 do
- mat_cp.(i).(j) <- m.(i).(j)
- done;
- done;
- let _ = row_reduce_h 1 1 (dim,mat_cp) in (dim,mat_cp)
-
- (*************** End Main Functions ***************)
-
- (*************** Optional module functions ***************)
-
- (* calculates the trace of a matrix *)
- let trace (((n,p),m): matrix) : elt =
- let rec build (elt: elt) (i: int) =
- if i > -1 then
- build (C.add m.(i).(i) elt) (i - 1)
- else
- elt in
- if n = p then build C.zero (n - 1)
- else raise ImproperDimensions
-
- (* calculates the transpose of a matrix and retuns a new one *)
- let transpose (((n,p),m): matrix) =
- let (dim,m') = empty p n in
- for i = 0 to n - 1 do
- for j = 0 to p - 1 do
- m'.(j).(i) <- m.(i).(j)
- done;
- done;
- assert(dim = (p,n));
- ((p,n),m')
-
- (* Returns the inverse of a matrix. Uses a pretty simple algorithm *)
- let inverse (mat: matrix) : matrix =
- let ((n, p), _) = mat in
- if n = p then
- (* create augmented matrix *)
- let augmented = empty n (2*n) in
- for i = 1 to n do
- let (dim,col) = get_column mat i in
- let arr = Array.make n C.zero in
- begin
- assert(dim = n);
- arr.(i-1) <- C.one;
- set_column augmented i col;
- set_column augmented (n + i) arr
- end
- done;
- let augmented' = row_reduce augmented in
- (* create the inverted matrix and fill in with appropriate values *)
- let inverse = empty n n in
- for i = 1 to n do
- let (dim, col) = get_column augmented' (n + i) in
- let _ = assert(dim = n) in
- let _ = set_column inverse i col in
- ()
- done;
- inverse
- else
- raise NonSquare
-
- (***************** HELPER FUNCTIONS FOR DETERMINANT *****************)
- (* creates an identity matrix of size n*)
- let create_identity (n:int) : matrix =
- let (dim,m) = empty n n in
- for i = 0 to n - 1 do
- m.(i).(i) <- C.one
- done;
- (dim,m)
-
- (* Finds the index of the maximum value of an array *)
- let find_max_index (arr: elt array) (start_index : int) : int =
- let rec find_index (max_index: int) (curr_index: int) =
- if curr_index = Array.length arr then max_index+1
- else
- match C.compare arr.(curr_index) arr.(max_index) with
- | Equal | Less -> find_index max_index (curr_index + 1)
- | Greater -> find_index curr_index (curr_index + 1) in
- find_index (start_index - 1) start_index
-
- (* Creates the pivoting matrix for A. Returns swqps. Adapted from
- * http://rosettacode.org/wiki/LU_decomposition#Common_Lisp *)
- let pivotize (((n,p),m): matrix) : matrix * int =
- if n = p then
- let swaps = ref 0 in
- let pivot_mat = create_identity n in
- for j = 1 to n do
- let (_,col) = get_column ((n,p),m) j in
- let max_index = find_max_index col j in
- if max_index <> j then
- (swaps := !swaps + 1; swap_row pivot_mat max_index j)
- else ()
- done;
- (pivot_mat,!swaps)
- else raise ImproperDimensions
-
- (* decomposes a matrix into a lower triangualar, upper triangualar
- * and a pivot matrix. It returns (L,U,P). Adapted from
- * http://rosettacode.org/wiki/LU_decomposition#Common_Lisp *)
- let lu_decomposition (((n,p),m): matrix) : (matrix*matrix*matrix)*int =
- if n = p then
- let mat = ((n,p),m) in
- let lower, upper, (pivot,s) = empty n n, empty n n, pivotize mat in
- let (_ ,l),(_ ,u), _ = lower,upper,pivot in
- let ((_, _),mat') = mult pivot mat in
- for j = 0 to n - 1 do
- l.(j).(j) <- C.one;
- for i = 0 to j do
- let sum = ref C.zero in
- for k = 0 to i - 1 do
- sum := C.add (!sum) (C.multiply u.(k).(j) l.(i).(k))
- done;
- u.(i).(j) <- C.subtract mat'.(i).(j) (!sum)
- done;
- for i = j to n - 1 do
- let sum = ref C.zero in
- for k = 0 to j - 1 do
- sum := C.add (!sum) (C.multiply u.(k).(j) l.(i).(k))
- done;
- let sub = C.subtract mat'.(i).(j) (!sum) in
- l.(i).(j) <- C.divide sub u.(j).(j)
- done;
- done;
- (lower,upper,pivot),s
- else raise ImproperDimensions
-
- (* Computes the determinant of a matrix *)
- let determinant (m: matrix) : elt =
- try
- let ((n,p), _) = m in
- if n = p then
- let rec triangualar_det (a,mat) curr_index acc =
- if curr_index < n then
- let acc' = C.multiply mat.(curr_index).(curr_index) acc in
- triangualar_det (a,mat) (curr_index + 1) acc'
- else acc in
- let ((dim1,l),(dim2,u), _),s = lu_decomposition m in
- let det1, det2 = triangualar_det (dim1,l) 0 C.one,
- triangualar_det (dim2,u) 0 C.one in
- if s mod 2 = 0 then C.multiply det1 det2
- else C.subtract C.zero (C.multiply det1 det2)
- else raise ImproperDimensions
- with
- | _ -> C.zero
-
-
- (*************** Optional module functions ***************)
-
-
-end