feat: add MPS module with DirectSampling simulation

examples/13_mps/channel_demo.py

@@ -0,0 +1,81 @@
+"""
+Direct Sampling demo — Strebelle (2002) channelized fluvial TI.
+Adapted for GSTools.
+"""
+
+import os
+import urllib.request
+
+import matplotlib.pyplot as plt
+import numpy as np
+from matplotlib.colors import ListedColormap
+
+from gstools import mps
+
+# 1. Load TI
+TI_URL = (
+    "https://raw.githubusercontent.com/GeostatsGuy/"
+    "GeoDataSets/master/MPS_Training_image_and_Realizations_500.npz"
+)
+CACHE = "mps_strebelle.npz"
+if not os.path.exists(CACHE):
+    print("Downloading Strebelle TI ...")
+    urllib.request.urlretrieve(TI_URL, CACHE)
+
+ti_arr = np.load(CACHE)["array1"].astype(int)  # (256, 256)
+ti_model = mps.TrainingImage(ti_arr, categorical=True)
+print(f"TI shape: {ti_model.shape}  sand={ti_arr.mean():.3f}")
+
+# 2. Conditioning: 100 random hard-data points from the TI
+SG_SIZE = 100
+N_COND = 100
+rng = np.random.default_rng(0)
+cond_row = rng.integers(0, SG_SIZE, N_COND)
+cond_col = rng.integers(0, SG_SIZE, N_COND)
+cond_pos = [cond_row.astype(float), cond_col.astype(float)]
+cond_val = ti_arr[cond_row, cond_col].astype(float)
+print(f"Conditioning: {N_COND} pts  sand={cond_val.mean():.3f}")
+
+# 3. Simulate (n=30, f=1.0, t=0.01)
+N_NEIGH = 30
+SCAN_F = 0.1
+THRESH = 0.01
+
+ds = mps.DirectSampling(
+    ti_model, n_neighbors=N_NEIGH, scan_fraction=SCAN_F, threshold=THRESH
+)
+ds.set_condition(cond_pos, cond_val)
+
+print("Starting simulation (this may take a moment)...")
+x = np.arange(SG_SIZE, dtype=float)
+y = np.arange(SG_SIZE, dtype=float)
+sg = ds([x, y], seed=42).astype(int)
+
+honored = (sg[cond_row, cond_col] == cond_val.astype(int)).sum()
+print(f"Simulation complete. Conditioning: {honored}/{N_COND} honored")
+
+# 4. Plot
+cmap = ListedColormap(["#c9a96e", "#2b6cb0"])
+fig, ax = plt.subplots(1, 2, figsize=(12, 6))
+
+ax[0].imshow(ti_arr[:SG_SIZE, :SG_SIZE], cmap=cmap, origin="upper")
+ax[0].set_title("Training Image (Crop)")
+
+im = ax[1].imshow(sg, cmap=cmap, origin="upper")
+ax[1].scatter(
+    cond_col,
+    cond_row,
+    c=cond_val,
+    cmap=cmap,
+    edgecolors="k",
+    s=20,
+    label="Cond. Points",
+)
+ax[1].set_title(f"DS Realization (n={N_NEIGH}, f={SCAN_F}, t={THRESH})")
+ax[1].legend()
+
+plt.colorbar(im, ax=ax.ravel().tolist(), ticks=[0.25, 0.75]).set_ticklabels(
+    ["shale", "sand"]
+)
+plt.savefig("channel_demo_mps.png", dpi=150, bbox_inches="tight")
+print("Saved plot to channel_demo_mps.png")

src/gstools/__init__.py

@@ -23,10 +23,21 @@
     tools
     transform
     normalizer
+    mps
 
 Classes
 =======
 
+Multiple Point Statistics
+^^^^^^^^^^^^^^^^^^^^^^^^
+Classes for Multiple Point Statistics (MPS) simulations
+
+.. currentmodule:: gstools.mps
+
+.. autosummary::
+   DirectSampling
+   TrainingImage
+
 Kriging
 ^^^^^^^
 Swiss-Army-Knife for Kriging. For short cut classes see: :any:`gstools.krige`
@@ -139,6 +150,7 @@
     covmodel,
     field,
     krige,
+    mps,
     normalizer,
     random,
     tools,
@@ -169,6 +181,7 @@
 )
 from gstools.field import PGS, SRF, CondSRF
 from gstools.krige import Krige
+from gstools.mps import DirectSampling, TrainingImage
 from gstools.tools import (
     DEGREE_SCALE,
     EARTH_RADIUS,
@@ -200,7 +213,7 @@
 
 __all__ = ["__version__"]
 __all__ += ["covmodel", "field", "variogram", "krige", "random", "tools"]
-__all__ += ["transform", "normalizer", "config"]
+__all__ += ["transform", "normalizer", "config", "mps"]
 __all__ += [
     "CovModel",
     "SumModel",
@@ -237,6 +250,8 @@
     "SRF",
     "CondSRF",
     "PGS",
+    "DirectSampling",
+    "TrainingImage",
     "rotated_main_axes",
     "generate_grid",
     "generate_st_grid",

src/gstools/mps/__init__.py

@@ -0,0 +1,18 @@
+"""
+GStools subpackage for Multiple Point Statistics (MPS).
+
+.. currentmodule:: gstools.mps
+
+Multiple Point Statistics
+^^^^^^^^^^^^^^^^^^^^^^^^
+.. autosummary::
+   :toctree:
+
+   DirectSampling
+   TrainingImage
+"""
+
+from gstools.mps.direct_sampling import DirectSampling
+from gstools.mps.training_image import TrainingImage
+
+__all__ = ["DirectSampling", "TrainingImage"]