From 09fbd8980525ca060e430996b33256f2aff87acb Mon Sep 17 00:00:00 2001
From: Matt Wala <wala1@illinois.edu>
Date: Fri, 23 Dec 2016 15:48:43 -0600
Subject: [PATCH 1/3] Cache derivative taking so that we start from the nearest
 available derivative (apparently, sympy doesn't do this).

This lets translation operators with big derivative expressions (order
20ish) finish compiling in a reasonable amount of time, even without
symengine.
---
 sumpy/expansion/local.py     | 12 ++++++------
 sumpy/expansion/multipole.py |  5 +++--
 sumpy/tools.py               | 31 +++++++++++++++++++++++++++----
 3 files changed, 36 insertions(+), 12 deletions(-)

diff --git a/sumpy/expansion/local.py b/sumpy/expansion/local.py
index 6c1fd28a..e3219933 100644
--- a/sumpy/expansion/local.py
+++ b/sumpy/expansion/local.py
@@ -91,11 +91,11 @@ class VolumeTaylorLocalExpansionBase(LocalExpansionBase):
     """
 
     def coefficients_from_source(self, avec, bvec):
-        from sumpy.tools import mi_derivative
+        from sumpy.tools import MiDerivativeTaker
         ppkernel = self.kernel.postprocess_at_source(
                 self.kernel.get_expression(avec), avec)
-        return [mi_derivative(ppkernel, avec, mi)
-                for mi in self.get_coefficient_identifiers()]
+        taker = MiDerivativeTaker(ppkernel, avec)
+        return [taker.diff(mi) for mi in self.get_coefficient_identifiers()]
 
     def evaluate(self, coeffs, bvec):
         from sumpy.tools import mi_power, mi_factorial
@@ -115,10 +115,10 @@ class VolumeTaylorLocalExpansionBase(LocalExpansionBase):
                     type(self).__name__,
                     self.order))
 
-        from sumpy.tools import mi_derivative
+        from sumpy.tools import MiDerivativeTaker
         expr = src_expansion.evaluate(src_coeff_exprs, dvec)
-        result = [mi_derivative(expr, dvec, mi)
-                for mi in self.get_coefficient_identifiers()]
+        taker = MiDerivativeTaker(expr, dvec)
+        result = [taker.diff(mi) for mi in self.get_coefficient_identifiers()]
 
         logger.info("building translation operator: done")
         return result
diff --git a/sumpy/expansion/multipole.py b/sumpy/expansion/multipole.py
index f579bd30..79412e17 100644
--- a/sumpy/expansion/multipole.py
+++ b/sumpy/expansion/multipole.py
@@ -92,9 +92,10 @@ class VolumeTaylorMultipoleExpansionBase(MultipoleExpansionBase):
         ppkernel = self.kernel.postprocess_at_target(
                 self.kernel.get_expression(bvec), bvec)
 
-        from sumpy.tools import mi_derivative
+        from sumpy.tools import MiDerivativeTaker
+        taker = MiDerivativeTaker(ppkernel, bvec)
         result = sum(
-                coeff * mi_derivative(ppkernel, bvec, mi)
+                coeff * taker.diff(mi)
                 for coeff, mi in zip(coeffs, self.get_coefficient_identifiers()))
         return result
 
diff --git a/sumpy/tools.py b/sumpy/tools.py
index d2d3a711..aaaeae7b 100644
--- a/sumpy/tools.py
+++ b/sumpy/tools.py
@@ -54,10 +54,33 @@ def mi_power(vector, mi):
     return result
 
 
-def mi_derivative(expr, vector, mi):
-    for mi_i, vec_i in zip(mi, vector):
-        expr = expr.diff(vec_i, mi_i)
-    return expr
+class MiDerivativeTaker(object):
+
+    def __init__(self, expr, var_list):
+        self.var_list = var_list
+        empty_mi = (0,) * len(var_list)
+        self.cache_by_mi = {empty_mi: expr}
+
+    def mi_dist(self, a, b):
+        return np.array(a, dtype=int) - np.array(b, dtype=int)
+
+    def diff(self, mi):
+        closest_mi = min(
+            (other_mi
+                for other_mi in self.cache_by_mi.keys()
+                if (np.array(mi) >= np.array(other_mi)).all()),
+            key = lambda other_mi: sum(self.mi_dist(mi, other_mi)))
+
+        expr = self.cache_by_mi[closest_mi]
+        current_mi = np.array(closest_mi, dtype=int)
+        for idx, (mi_i, vec_i) in enumerate(
+                    zip(self.mi_distvec(mi, closest_mi), self.var_list)):
+            for i in range(1, 1 + mi_i):
+                current_mi[idx] += 1
+                expr = expr.diff(vec_i)
+                self.cache_by_mi[tuple(current_mi)] = expr
+
+        return expr
 
 # }}}
 
-- 
GitLab


From cdd993f91f1b3a58c461e01ea4544525cbca27b8 Mon Sep 17 00:00:00 2001
From: Matt Wala <wala1@illinois.edu>
Date: Fri, 23 Dec 2016 16:11:40 -0600
Subject: [PATCH 2/3] Fix flake8 warning.

---
 sumpy/tools.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sumpy/tools.py b/sumpy/tools.py
index aaaeae7b..b0cd2322 100644
--- a/sumpy/tools.py
+++ b/sumpy/tools.py
@@ -69,7 +69,7 @@ class MiDerivativeTaker(object):
             (other_mi
                 for other_mi in self.cache_by_mi.keys()
                 if (np.array(mi) >= np.array(other_mi)).all()),
-            key = lambda other_mi: sum(self.mi_dist(mi, other_mi)))
+            key=lambda other_mi: sum(self.mi_dist(mi, other_mi)))
 
         expr = self.cache_by_mi[closest_mi]
         current_mi = np.array(closest_mi, dtype=int)
-- 
GitLab


From 5573aa9b2de39018d91162d77a212df654b2e2d5 Mon Sep 17 00:00:00 2001
From: Matt Wala <wala1@illinois.edu>
Date: Fri, 23 Dec 2016 16:17:32 -0600
Subject: [PATCH 3/3] Fix called method name.

---
 sumpy/tools.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sumpy/tools.py b/sumpy/tools.py
index aaaeae7b..ce6c8c9b 100644
--- a/sumpy/tools.py
+++ b/sumpy/tools.py
@@ -74,7 +74,7 @@ class MiDerivativeTaker(object):
         expr = self.cache_by_mi[closest_mi]
         current_mi = np.array(closest_mi, dtype=int)
         for idx, (mi_i, vec_i) in enumerate(
-                    zip(self.mi_distvec(mi, closest_mi), self.var_list)):
+                    zip(self.mi_dist(mi, closest_mi), self.var_list)):
             for i in range(1, 1 + mi_i):
                 current_mi[idx] += 1
                 expr = expr.diff(vec_i)
-- 
GitLab