为什么这些线性不等式约束在Matlab中起作用但在Octave中不起作用?

问题描述 投票:1回答:1

我有以下脚本执行非线性优化(NLP),该脚本可在Matlab中运行,并在我的计算机上大约5分钟后命中MaxFunctionEvaluations

% Generate sample consumption data (4 weeks)
x = 0:pi/8:21*pi-1e-1; %figure; plot(x, 120+5*sin(0.2*x).*exp(-2e-2*x) + 10*exp(-x))
y = 120 + 5*sin(0.2*x).*exp(-2e-2*x) + 10*exp(-x);
consumptionPerWeek  = (y + [0; 11; -30; 4.5]).'; % in 168x4 format
consumptionPerHour  = reshape(consumptionPerWeek, [], 1);

hoursPerWeek        = 168;
hoursTotal          = numel(consumptionPerHour);
daysTotal           = hoursTotal/24;
weeksTotal          = ceil(daysTotal/7);

%% Perform some simple calculations
q_M_mean            = mean(consumptionPerHour);
dvsScalingPerWeek   = mean(consumptionPerWeek)/q_M_mean;

%% Assumptions about reactor, hard-coded
V_liq           = 5701.0; % m^3, main reactor; from other script
initialValue    = 4.9298; % kg/m^3; from other script

substrates_FM_year = [676.5362; 451.0241];
total_DVS_year  = [179.9586; 20.8867];
mean_DVS_conc   = 178.1238; %kg/m^3

% Product yields (m^3 per ton DVS)
Y_M             = 420;
Y_N             = 389;

%% Test DVS model
DVS_hour        = sum(total_DVS_year)/hoursTotal; % t/h
k_1             = 0.25; % 1/d
parameters      = [k_1; Y_M; Y_N; V_liq];

%% Build reference and initial values for optimization
% Distribute feed according to demand (-24%/+26% around mean)
feedInitialMatrix = DVS_hour*ones(hoursPerWeek, 1)*dvsScalingPerWeek;

% Calculate states with reference feed (improved initials)
feedInitialVector = reshape(feedInitialMatrix, [], 1);
feedInitialVector = feedInitialVector(1:hoursTotal);

resultsRef      = reactorModel1(feedInitialVector, initialValue, parameters, ...
    mean_DVS_conc);
V_M_PS          = 0 + cumsum(resultsRef(:,2)/24 - consumptionPerHour);
neededMStorage0 = max(V_M_PS) - min(V_M_PS);

%% Setup optimization problem (NLP): feed optimization with virtual product storage
% Objective function 1: Standard deviation of theoretical product storage volume
objFun1 = @(feedVector) objFunScalar(feedVector, initialValue, parameters, ...
    mean_DVS_conc, consumptionPerHour);
% Bounds (lb <= x <= ub), i.e., decision variables can only range between 0 and 0.9*dailyDvsAmount
upperfeedLimitSlot       = 0.90; % Limit DVS feed amount per *slot*
upperfeedLimitDay        = 1.80; % Limit DVS feed amount per *day*
upperfeedLimitWeek       = 1.37; % Limit DVS feed amount per *week*

lowerBound_nlp  = zeros(1, hoursTotal);
upperBound_nlp  = upperfeedLimitSlot*24*DVS_hour.*ones(1, hoursTotal);

% Equality Constraint 1: feed amount mean = constant
A_eq1_nlp   = ones(1, hoursTotal);
b_eq1_nlp   = DVS_hour*hoursTotal;

% Inequality Constraint 1: Limit max. daily amount
A_nlp1      = zeros(daysTotal, hoursTotal);
for dI = 1:daysTotal
    A_nlp1(dI, (24*dI)-(24-1):(24*dI)) = 1;
end
b_nlp1      = upperfeedLimitDay*24*DVS_hour*ones(daysTotal, 1);

% Inequality Constraint 2: Limit max. weekly amount
A_nlp2      = zeros(weeksTotal, hoursTotal);
for wIi = 1:weeksTotal
    A_nlp2(wIi, (168*wIi)-(168-1):(168*wIi)) = 1;
end
b_nlp2      = upperfeedLimitWeek*168*DVS_hour*ones(weeksTotal, 1);

% Summarize all inequality constraints
A_nlp       = [A_nlp1; A_nlp2]; %sparse([A_nlp1; A_nlp2]);
b_nlp       = [b_nlp1; b_nlp2]; %sparse([b_nlp1; b_nlp2]);

try
    % Solver: fmincon (Matlab Optimization Toolbox) --> SQP-algorithm = best
    optionen_GB = optimoptions('fmincon', 'Display', 'iter', 'FunctionTolerance', 1e-5, ...
        'StepTolerance', 1e-4, 'MaxIterations', 2*hoursTotal, ...
        'MaxFunctionEvaluations', 100*hoursTotal, 'HonorBounds', true, 'Algorithm', 'sqp');
catch
    optionen_GB = optimset('Display', 'iter', 'TolFun', 1e-5, 'TolX', 1e-4, ...
        'MaxIter', 2*hoursTotal, 'MaxFunEvals', 100*hoursTotal, 'Algorithm', 'sqp');
end

%% Solve gradient-based NLP
tic; [feedOpt, fval] = fmincon(@(feedVector) objFun1(feedVector), ...
    feedInitialVector, A_nlp, b_nlp, A_eq1_nlp, b_eq1_nlp, lowerBound_nlp, upperBound_nlp, ...
        [], optionen_GB); toc

%% Rerun model and calculate virtual storage volume with optimized input
resultsOpt      = reactorModel1(feedOpt, initialValue, parameters, mean_DVS_conc);
q_M_Opt         = resultsOpt(:,2)/24;

V_M_PS_opt      = 0 + cumsum(q_M_Opt - consumptionPerHour);
neededMStorageOpt = max(V_M_PS_opt) - min(V_M_PS_opt);
sprintf('Needed product storage before optimization: %.2f m^3, \nafterwards: %.2f m^3. Reduction = %.1f %%', ...
    neededMStorage0, neededMStorageOpt, (1 - neededMStorageOpt/neededMStorage0)*100)

%% Objective as separate function
function prodStorageStd = objFunScalar(dvs_feed, initialValues, parameters, mean_DVS_conc, ...
    MConsumptionPerHour)

    resultsAlgb = reactorModel1(dvs_feed(:, 1), initialValues, parameters, mean_DVS_conc);
    q_M_prod    = resultsAlgb(:,2)/24;

    V_M_PS1     = 0 + cumsum(q_M_prod - MConsumptionPerHour);
    prodStorageStd  = std(V_M_PS1);
end

外部函数的读法如下:

function resultsArray = reactorModel1(D_feed, initialValue, parameters, D_in)
    % Simulate production per hour with algebraic reactor model
    % Feed is solved via a for-loop

    hoursTotal  = length(D_feed);
    k_1         = parameters(1);
    Y_M         = parameters(2);
    Y_N         = parameters(3);
    V_liq       = parameters(4);
    resultsArray = zeros(hoursTotal, 3);
    t           = 1/24;

    liquid_feed = D_feed/(D_in*1e-3); % m^3/h

    initialValue4Model0 = (initialValue*(V_liq - liquid_feed(1))*1e-3 ...
        + D_feed(1))*1e3/V_liq; % kg/m^3
    resultsArray(1, 1) = initialValue4Model0*exp(-k_1*t);
    % Simple for-loop with feed as vector per hour
    for pHour = 2:hoursTotal
        initialValue4Model = (resultsArray(pHour-1, 1)*(V_liq - liquid_feed(pHour))*1e-3 ...
            + D_feed(pHour))*1e3/V_liq; % kg/m^3
        resultsArray(pHour, 1) = initialValue4Model*exp(-k_1*t);
    end
    resultsArray(:, 2) = V_liq*Y_M*k_1*resultsArray(:, 1)*1e-3; % m^3/d
    resultsArray(:, 3) = V_liq*Y_N*k_1*resultsArray(:, 1)*1e-3; % m^3/d
end

当我在Octave中执行完全相同的脚本(版本5.1.0和optim 1.6.0)时,我得到:

错误:线性不平等约束:错误的尺寸

实际上是以下行(从命令提示符处执行)

sum(A_nlp*feedInitialVector <= b_nlp)

在Octave和Matlab上都给出32,因此表明尺寸正确

这是一个错误吗?还是Octave处理线性(不等式)约束与Matlab有所不同?

(此外,如果您有如何加快此脚本的提示,它们将派上用场。)

matlab octave nonlinear-optimization
1个回答
2
投票

我已对此进行了一些调试,以帮助您入门。

首先启用对错误的调试:

debug_on_error(1)

然后找到optim的安装文件夹,并查看其中的文件/private/__linear_constraint_dimensions__.m*(我通过对您得到的确切错误进行了grep操作发现了这一点,并找到了相关的文件。在私有文件夹之外还有另一个,您可能也想看看。)] >

[如果您查看引发错误的代码行,则会注意到,例如如果rm != o.np,则触发错误,其中[rm, cm] = size(f.imc)

现在运行您的脚本,并使其在出现错误时进入调试模式。您将看到:

debug> [rm, cm] = size(f.imc)
rm =  32
cm =  672

debug> o.np
ans =  672

debug> rm != o.np
ans = 1   % I.e. boolean test succeeds and triggers error

我不知道它们是什么,大概r和c反映了行和列,但是在任何情况下,您都会发现您似乎试图将行与列进行匹配,反之亦然。

换句话说,似乎您可能在某个时候以换位方式传递了输入。

无论如何,如果这不是正在发生的事情,这应该是一个不错的起点,让您可以找出确切的错误。

我不知道为什么Matlab“有效”。也许您的代码中有一个错误,尽管它(无论好坏),matlab都能正常工作。否则,可能会出现一个错误,即无意中(或至少以与matlab不兼容的方式)对输入进行了调换。]

如果您在调试冒险后觉得它是optim软件包中的错误,请随时提交错误报告:)

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