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"Reduce" wierdness (or too slow?)

  • To: mathgroup at smc.vnet.net
  • Subject: [mg88996] "Reduce" wierdness (or too slow?)
  • From: TuesdayShopping <TuesdayShopping at yahoo.com>
  • Date: Fri, 23 May 2008 03:07:43 -0400 (EDT)

Following equations solve (H, z4 and a couple of others are fully solved; others are not solved; that is OK) in a fraction of a second. If I add the inequalities ONE AT A TIME "t7 > 0, t7 > t1, t7 > t2, t7 > t3, t7 > t4, t7 > t5, t7 > t6", the time taken for "Reduce"  will will go up exponentially; after the inequation "t7>t3" it will not even complete in 600 seconds!

Is "Reduce" buggy? Any idea how I can still use Reduce to solve the set with inequations (a solution like "OK. .  so do not use the inequations with Reduce" is not a solution because I isolated the inequations after a lot of time trying various things and may not be able to do that for all the problems; and sometimes I do need the inequations in order to limit the result set)

Thanks a lot for any input into this.

InputForm[AbsoluteTiming[TimeConstrained[Reduce[
        {1000 + t2 == t3
         , 1200 + w1 == w2
         , 125 + t1 == t2
         , 125 + t5 == t6
         , k*t3 == (v2 + z2)/2
         , t7*z1 + t2*z2 + z3 + z4 == H + (k*t2^2) + (k*t7^2) + w1
         , t7*z1 + t3*z2 + z3 + z4 == H + (k*(t3^2 + t7^2))
         , t7*z1 + z3 + z4 == 2*H + (k*t7^2)
         , w1 + t6*z1 + z3 == (k*t6^2) + w1 + w2
         , w1 == w2 + ((t1 - t2)*(k*t1 + k*t2 - z2))
         , w2 + t5*z1 + z3 == (k*t5^2) + w1 + w2
         , w2 == (-k*t1^2) + t1*z2 + z4
         , z1 == (2*k*t4) + v2
         , z2 == 0
 
  
         ,(k*t1^2)+w2==H+t1*z2

  
     }, {g, H, t1, t2, t3, t4, t5, t6, t7, v2, w1, w2, z1, z2, z3, z4}], 120, TimedOut]], NumberMarks -> False]


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