### `dsolv_starting_term`

dsolv_starting_term(f,v,w)
:: 正則ホロノミック系 f の方向 w での級数解の Staring terms を計算する. ここで, v は変数の集合.

リスト
f, v, w
リスト
• 正則ホロノミック系 f の方向 w での級数解の Staring terms を計算する. ここで, v は変数の集合.
• 戻り値は次の形をしている: [[e1, e2, ...], [s1, s2, ...]] ここで e1 は exponent ベクトルであり s1 はこのベクトルに 対応する解の集合, 以下同様.
• 変数 `Dsolv_message_starting_term` を 1 にしておくと, この函数は計算の途中にいろいろとメッセージを出力する.

Algorithm: Saito, Sturmfels, Takayama, Grobner Deformations of Hypergeometric Differential Equations ([SST]), Chapter 2.

```[1076]   F = sm1_gkz( [ [[1,1,1,1,1],[1,1,0,-1,0],[0,1,1,-1,0]], [1,0,0]]);
[[x5*dx5+x4*dx4+x3*dx3+x2*dx2+x1*dx1-1,-x4*dx4+x2*dx2+x1*dx1,
-x4*dx4+x3*dx3+x2*dx2,
-dx2*dx5+dx1*dx3,dx5^2-dx2*dx4],[x1,x2,x3,x4,x5]]
[1077]  A= dsolv_starting_term(F[0],F[1],[1,1,1,1,0])\$
Computing the initial ideal.
Done.
Computing a primary ideal decomposition.
Primary ideal decomposition of the initial Frobenius ideal
to the direction [1,1,1,1,0] is
[[[x5+2*x4+x3-1,x5+3*x4-x2-1,x5+2*x4+x1-1,3*x5^2+(8*x4-6)*x5-8*x4+3,
x5^2-2*x5-8*x4^2+1,x5^3-3*x5^2+3*x5-1],
[x5-1,x4,x3,x2,x1]]]

----------- root is [ 0 0 0 0 1 ]
----------- dual system is
[x5^2+(-3/4*x4-1/2*x3-1/4*x2-1/2*x1)*x5+1/8*x4^2
+(1/4*x3+1/4*x1)*x4+1/4*x2*x3-1/8*x2^2+1/4*x1*x2,
x4-2*x3+3*x2-2*x1,x5-x3+x2-x1,1]

[1078] A[0];
[[ 0 0 0 0 1 ]]
[1079] map(fctr,A[1][0]);
[[[1/8,1],[x5,1],[log(x2)+log(x4)-2*log(x5),1],
[2*log(x1)-log(x2)+2*log(x3)+log(x4)-4*log(x5),1]],
[[1,1],[x5,1],[-2*log(x1)+3*log(x2)-2*log(x3)+log(x4),1]],
[[1,1],[x5,1],[-log(x1)+log(x2)-log(x3)+log(x5),1]],
[[1,1],[x5,1]]]

```