pari | 易学教程

初创公司风险投资：一场全垒打的比赛

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　　在不确定的经济条件下，风投这十年步履蹒跚，但始终未变的方向是寻找具有颠覆性的企业。　　过去的十年里，风险资本迅猛增长。　　在数十亿美元退出、硅谷初创企业爆炸式增长以及软银 1000 亿美元愿景基金大规模融资的推动下，全球年度资本投资从 2010 年到 2019 年增长了近 13 倍，达到 1600 亿美元。与此同时，超大轮投资（投资额在 1 亿美元以上）数量从 2016 年到 2018 年几乎增长了两倍。　　图 | 过去十年全球 VC 投资额及投资数量统计（来源：CB Insights）　　然而，新冠肺炎带来的经济下行在一定程度上抑制了投资交易。投资于种子轮公司的风投越来越少，据统计 2020 年 3 月，美国整体风投交易同比下降 22%。疫情让投资者在投资时更加挑剔，他们更倾向于把钱交给那些证明自己有足够实力经受住疫情带来的冲击，并在经济回升时可以实现增长的公司。　　但其实风险投资在很多方面都可以抵御短期风险，原因很简单，风险投资是长期的。VC 并不一定要投资那些在短期之内会有巨大增长的初创公司；他们真正希望寻找到的是那些能在 10 年后成长为行业内顶尖的公司。　　总体而言，风险投资的基本策略从来没有改变过。他们更愿意将赌注押在具有突破性技术/产品或是从根本上改变一个行业的初创公司上。　　在这份报告中，我们将通过解释风险投资中的关键定义

Fraction Value Problem in Ctypes to PARI/GP

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问题 I have written a code to compare the solution of sympy and PARI/GP , but when I give a fraction value D=13/12 , I get error, TypeError: int expected instead of float . So I changed p1[i] = pari.stoi(c_long(numbers[i - 1])) to p1[i] = pari.stoi(c_float(numbers[i - 1])) , but then nfroots gives no output, note that I have to use fraction in A, B, C, D which might take $10^10$ digits after decimal point. How can I solve this problem? The code is given below to download the libpari.dll file,

Getting an Array/Vector from PARI/GP in Python using Ctypes

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问题 I have written a code to compare the solution of sympy and PARI/GP , how ever I am facing a problem to get an array/vector from PARI/GP. When I try to return the vector res from PARI/GP function nfroots , I get a address like this (see the last line) - [3, 4] elements as long (only if of type t_INT): 3 4 <__main__.LP_LP_c_long object at 0x00000000056166C8> how can I get the res as vector/array from nfroots so I can use that array like normal python vector/array? The code is given below to

How to use Tuple/Array/Vector to call PARI/GP from Python (ctypes)?

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问题 I would like to call PARI/GP from Python. I need to use ellisdivisible(E; P; n;{&Q}) function of PARI (see function no 3.15.35 on page 441 in this link:), so I have to pass 2 vectors or arrays (e.g, E = ellinit([0,-1,1,0,0], K);P = [0,0]; ), how I do that? To call a PARI function(in C) of single argument/variable from Python (given by Thomas Baruchel), we have something like below - import ctypes # load the library pari=ctypes.cdll.LoadLibrary("libpari.so") # set the right return type of the

Sending a Polynomial to PARI/GP from Python (ctypes)

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问题 I would like to call nfroots({nf}; x) function of PARI/GP from Python. (see function no 3.13.135.on page 371 in this link:), but the probllem is, I couldn't send the algebraic expression or the polynomial, that need to be send, for example, x^2-7x+12 , here is a very simple example of what gp can do with a quartic polynomial: > V = readvec("coeff.txt"); > print(V) [1,-7,12] > P = Pol(V); # I get following error when I use Pol in my code: func=self._FuncPtr((name_or_ordinal, self))

Unable to install Math::Pari module

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问题 I am trying to install Crypt::Random module, a cryptographically secure random number generator, and says it requires Math::Pari 2.001802, which is not availible from cpan.org, but says it is available from this other URL, which does not work. I tried to install them both anyway and encountered this problem: C:\Users\Jlinne\Documents> cpanm Crypt::Random --> Working on Crypt::Random Fetching http://www.cpan.org/authors/id/V/VI/VIPUL/Crypt-Random-1.25.tar.gz ... OK Configuring Crypt-Random-1

Finding entry of vector in PARI/GP?

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问题 With PARI/GP, if I have a vector with unique entries: a = [9, 7, 3, 5, 2, 8, 1, 0, 11] how do I get the position (index) of an entry in the vector a ? like: i = vectorsearch(a, 8); a[i] %1 = 8 Converting into a set and using setsearch doesn't work! 回答1: Just do select((x) -> x == 8, a, 1) where flag 1 means the "index mode". In general, your function is as shown below. position = (elt, array) -> select((x) -> x == elt, array, 1); Please note, despite the fact that this stuff does a lambda

Compiling with a multi-precision math library in C using Code::Blocks on Windows

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问题 I'm having a lot of trouble figuring out how to do this. I need an arbitrary precision library for math in C. I'm good with either CLN or PARI/GP, both of which I've installed. I'm using Windows, so I had to do this via Cygwin, and ran the ./Configure files, followed by make install. Everything's built, but I cannot figure out how to link it all and use it. I'm using Code::Blocks, and anytime I try to include the necessary header files, there are loads of errors. I also link the .a file with

Doxygen: how to document a non-C function using only its documentation block but not the code?

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问题 I want Doxygen to document the code written in C-like language (PARI/GP) but having slightly different syntax. I believe Doxygen can document the entities those do not exist. It seems to be the simplest way to do the job while the programming language is not Doxygen-supported. I want something like this: /*! \fn foo(param,{option}) \brief some brief description here \param[in](param) mandatory parameter description \param[in](option) optional parameter description */ /*! \cond DOXYGEN_SHOULD

perl Can't locate loadable object for module Math::Pari in @INC

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问题 I've written a perl script which run's fine on my environment, but on my client environment it fails on: Can't locate loadable object for module Math::Pari in @INC (@INC contains: Error-0.17020/lib JSON-2.57/lib URI-1.60 libwww-perl-5.836/lib Net-Address-IP-Local-0.1.2/lib Math-GMP-2.06/ Net- SSH-Perl-1.35/lib/ /etc/perl /usr/local/lib/perl/5.14.2 /usr/local/share/perl/5.14.2 /usr/lib/perl5 /usr/share/perl5 /usr/lib/perl/5.14 /usr/share/perl/5.14 /usr/local/lib/site_perl .) at Net-SSH-Perl-1