From 87bde213bad2dfe69ec8059f11440e0daea1b6b4 Mon Sep 17 00:00:00 2001
From: Gordon McCann <gmccann@fsu.edu>
Date: Tue, 8 Jun 2021 09:58:24 -0400
Subject: [PATCH] Removed gsl dependence for compatibility with NRB machines.
 Added in homeade legendre polynomials. Updated README to reflect

---
 README.md              |  2 +-
 include/LegendrePoly.h |  6 ++++++
 input.txt              |  2 +-
 makefile               |  2 +-
 src/LegendrePoly.cpp   | 11 +++++++++++
 src/ReactionSystem.cpp |  4 ++--
 6 files changed, 22 insertions(+), 5 deletions(-)
 create mode 100644 include/LegendrePoly.h
 create mode 100644 src/LegendrePoly.cpp

diff --git a/README.md b/README.md
index d7879dd..3e624b1 100644
--- a/README.md
+++ b/README.md
@@ -33,4 +33,4 @@ To run MASK simply do the following from the MASK directory:
 Input.txt can be replaced by any text file with the correct format.
 
 ## Requirements
-MASK requires that ROOT is installed for data writting and visualization, as well as for random number generation. It also requires gsl to calculate Legendre Polynomials. Testing has been done only on ROOT 6. Mileage on all other ROOT versions will vary.
\ No newline at end of file
+MASK requires that ROOT is installed for data writting and visualization, as well as for random number generation. Testing has been done only on ROOT 6. Mileage on all other ROOT versions will vary.
diff --git a/include/LegendrePoly.h b/include/LegendrePoly.h
new file mode 100644
index 0000000..d05808b
--- /dev/null
+++ b/include/LegendrePoly.h
@@ -0,0 +1,6 @@
+#ifndef LEGENDREPOLY_H
+#define LEGENDREPOLY_H
+
+double P_l(int l, double x);
+
+#endif
\ No newline at end of file
diff --git a/input.txt b/input.txt
index 28d8328..3b38af1 100644
--- a/input.txt
+++ b/input.txt
@@ -1,5 +1,5 @@
 ----------Data Information----------
-OutputFile: /media/gordon/b6414c35-ec1f-4fc1-83bc-a6b68ca4325a/gwm17/12C3Hed_13N3546keV_ps_fixedThetaBins_test.root
+OutputFile: /data1/gwm17/10B3He/Feb2021/12C3Hed_13N3546keV_ps_fixedThetaBins_test.root
 SaveTree: yes
 SavePlots: yes
 ----------Reaction Information----------
diff --git a/makefile b/makefile
index 11edf5c..c6e4090 100644
--- a/makefile
+++ b/makefile
@@ -2,7 +2,7 @@ CC=g++
 ROOTGEN=rootcint
 CFLAGS=-g -Wall `root-config --cflags`
 CPPFLAGS=-I ./include
-LDFLAGS=`root-config --glibs` -lgsl
+LDFLAGS=`root-config --glibs`
 
 ROOTINCLDIR=./
 INCLDIR=./include
diff --git a/src/LegendrePoly.cpp b/src/LegendrePoly.cpp
new file mode 100644
index 0000000..ddeeace
--- /dev/null
+++ b/src/LegendrePoly.cpp
@@ -0,0 +1,11 @@
+#include "LegendrePoly.h"
+
+double P_l(int l, double x) {
+	if(l == 0) {
+		return 1.0;
+	} else if (l == 1) {
+		return x;
+	} else {
+		return ((2.0*l + 1.0)*x*P_l(l-1, x) - (l-1.0)*P_l(l-2, x))/(double(l));
+	}
+}
\ No newline at end of file
diff --git a/src/ReactionSystem.cpp b/src/ReactionSystem.cpp
index 199257c..dfc2f7e 100644
--- a/src/ReactionSystem.cpp
+++ b/src/ReactionSystem.cpp
@@ -1,6 +1,6 @@
 #include "ReactionSystem.h"
 #include "KinematicsExceptions.h"
-#include <gsl/gsl_sf_legendre.h>
+#include "LegendrePoly.h"
 
 namespace Mask {
 
@@ -65,7 +65,7 @@ double ReactionSystem::GetDecayTheta(int L) {
 	do {
 		costheta = generator->Uniform(-1.0, 1.0);
 		check = generator->Uniform(0.0, 1.0);
-		probability = std::pow(gsl_sf_legendre_Pl(L, costheta), 2.0);
+		probability = std::pow(P_l(L, costheta), 2.0);
 	} while(check > probability);
 
 	return std::acos(costheta);