From 9ffb94d2ca9149bbd69b8919d14169a942b4702f Mon Sep 17 00:00:00 2001
From: houkensjtu <houkensjtu@gmail.com>
Date: Thu, 4 May 2023 19:42:43 +0800
Subject: [PATCH] Add docstring to SparseCG and MatrixFreeCG.

---
 python/taichi/linalg/matrixfree_cg.py | 14 ++++++++++++++
 python/taichi/linalg/sparse_cg.py     | 12 ++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/python/taichi/linalg/matrixfree_cg.py b/python/taichi/linalg/matrixfree_cg.py
index d997dc2e61bd3..6af5ef177c387 100644
--- a/python/taichi/linalg/matrixfree_cg.py
+++ b/python/taichi/linalg/matrixfree_cg.py
@@ -17,6 +17,20 @@ def matvec(self, x, Ax):
 
 
 def MatrixFreeCG(A, b, x, tol=1e-6, maxiter=5000, quiet=True):
+    """Matrix-free conjugate-gradient solver.
+    
+    Use conjugate-gradient method to solve the linear system Ax = b, where A is implicitly
+    represented as a LinearOperator.
+
+    Args:
+        A (LinearOperator): The coefficient matrix A of the linear system.
+        b (Field): The right-hand side of the linear system.
+        x (Field): The initial guess for the solution.
+        maxiter (int): Maximum number of iterations.
+        atol: Tolerance(absolute) for convergence.
+        quiet (bool): Switch to turn on/off iteration log.
+    """
+    
     if b.dtype != x.dtype:
         raise TaichiTypeError(f"Dtype mismatch b.dtype({b.dtype}) != x.dtype({x.dtype}).")
     if str(b.dtype) == "f32":
diff --git a/python/taichi/linalg/sparse_cg.py b/python/taichi/linalg/sparse_cg.py
index fc0611fbff660..5ebdf663f5ca9 100644
--- a/python/taichi/linalg/sparse_cg.py
+++ b/python/taichi/linalg/sparse_cg.py
@@ -7,6 +7,18 @@
 
 
 class SparseCG:
+    """Conjugate-gradient solver built for SparseMatrix.
+    
+    Use conjugate-gradient method to solve the linear system Ax = b, where A is SparseMatrix.
+
+    Args:
+        A (SparseMatrix): The coefficient matrix A of the linear system.
+        b (numpy ndarray, taichi Ndarray): The right-hand side of the linear system.
+        x0 (numpy ndarray, taichi Ndarray): The initial guess for the solution.
+        max_iter (int): Maximum number of iterations.
+        atol: Tolerance(absolute) for convergence.
+    """
+    
     def __init__(self, A, b, x0=None, max_iter=50, atol=1e-6):
         self.dtype = A.dtype
         self.ti_arch = get_runtime().prog.config().arch