From 422700fd315ef96501f151a2055c762d44edf9b8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Thomas=20G=C3=BCnther?= <Thomas.Guenther@leibniz-liag.de>
Date: Fri, 3 Jun 2022 10:05:39 +0200
Subject: [PATCH] add LinearModelling operator

---
 pygimli/frameworks/__init__.py  |  2 +-
 pygimli/frameworks/modelling.py | 22 ++++++++++++++++++++++
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/pygimli/frameworks/__init__.py b/pygimli/frameworks/__init__.py
index 63f07cd90..a7a5cbc74 100644
--- a/pygimli/frameworks/__init__.py
+++ b/pygimli/frameworks/__init__.py
@@ -3,7 +3,7 @@
 
 
 from .modelling import (Modelling, Block1DModelling, MeshModelling,
-                        JointModelling, PriorModelling,
+                        JointModelling, PriorModelling, LinearModelling,
                         PetroModelling, LCModelling, ParameterModelling)
 
 from .inversion import (Inversion, MarquardtInversion,
diff --git a/pygimli/frameworks/modelling.py b/pygimli/frameworks/modelling.py
index cd267212c..e3c49e4cf 100644
--- a/pygimli/frameworks/modelling.py
+++ b/pygimli/frameworks/modelling.py
@@ -412,6 +412,28 @@ def drawData(self, ax, data, **kwargs):
             raise Exception("No yet implemented")
 
 
+class LinearModelling(Modelling):
+    """Modelling class for linearized problems with a given matrix."""
+    def __init__(self, A):
+        """Initialize by storing the (reference to the) matrix."""
+        super().__init__()
+        self.A = A
+        self.setJacobian(self.A)
+
+    def response(self, model):
+        """Linearized forward modelling by matrix-vector product."""
+        return self.A * model
+
+    def createJacobian(self, model):
+        """Do not compute a jacobian (linear)."""
+        pass
+
+    @property
+    def parameterCount(self):
+        """Define the number of parameters from the matrix size."""
+        return self.A.cols()
+
+
 class Block1DModelling(Modelling):
     """General forward operator for 1D layered models.