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-rw-r--r--ext/bigdecimal/sample/linear.rb46
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diff --git a/ext/bigdecimal/sample/linear.rb b/ext/bigdecimal/sample/linear.rb
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+#!/usr/local/bin/ruby
+
+#
+# linear.rb
+#
+# Solves linear equation system(A*x = b) by LU decomposition method.
+# where A is a coefficient matrix,x is an answer vector,b is a constant vector.
+#
+require "bigdecimal"
+require "ludcmp"
+
+include LUSolve
+
+def rd_order
+ printf("Number of equations ?")
+ n = gets().chomp.to_i
+end
+
+zero = BigDecimal::new("0.0")
+one = BigDecimal::new("1.0")
+
+while (n=rd_order())>0
+ a = []
+ as= []
+ b = []
+ printf("\nEnter coefficient matrix element A[i,j]\n");
+ for i in 0...n do
+ for j in 0...n do
+ printf("A[%d,%d]? ",i,j); s = gets
+ a <<=BigDecimal::new(s);
+ as<<=BigDecimal::new(s);
+ end
+ printf("Contatant vector element b[%d] ? ",i);b<<=BigDecimal::new(gets);
+ end
+ printf "ANS="
+ x = lusolve(a,b,ludecomp(a,n,zero,one),zero)
+ p x
+ printf "A*x-b\n"
+ for i in 0...n do
+ s = zero
+ for j in 0...n do
+ s = s + as[i*n+j]*x[j]
+ end
+ p s-b[i]
+ end
+end