#!/usr/local/bin/ruby # frozen_string_literal: false # # 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. # # USAGE: # ruby linear.rb [input file solved] # # :stopdoc: require "bigdecimal" require "bigdecimal/ludcmp" # # NOTE: # Change following BigDecimal.limit() if needed. BigDecimal.limit(100) # include LUSolve def rd_order(na) printf("Number of equations ?") if(na <= 0) n = ARGF.gets().to_i end na = ARGV.size zero = BigDecimal("0.0") one = BigDecimal("1.0") while (n=rd_order(na))>0 a = [] as= [] b = [] if na <= 0 # Read data from console. 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 = ARGF.gets a << BigDecimal(s) as << BigDecimal(s) end printf("Contatant vector element b[%d] ? ",i) b << BigDecimal(ARGF.gets) end else # Read data from specified file. printf("Coefficient matrix and constant vector.\n") for i in 0...n do s = ARGF.gets printf("%d) %s",i,s) s = s.split for j in 0...n do a << BigDecimal(s[j]) as << BigDecimal(s[j]) end b << BigDecimal(s[n]) end end x = lusolve(a,b,ludecomp(a,n,zero,one),zero) printf("Answer(x[i] & (A*x-b)[i]) follows\n") for i in 0...n do printf("x[%d]=%s ",i,x[i].to_s) s = zero for j in 0...n do s = s + as[i*n+j]*x[j] end printf(" & %s\n",(s-b[i]).to_s) end end